Business Resource Efficiency Guide
Tracking Water Use to Cut Costs
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
II
Our vision is a world without
waste, where resources are
used sustainably.
We work with businesses and
individuals to help them reap the
benefits of reducing waste, develop
sustainable products and use
resources in an efficient way.
Find out more from the WRAP
Resource Efficiency Helpline on
0808 100 2040 or at
www.wrap.org.uk
Contents
1
Home
Why is saving water important?
1.1 The true cost of water
1.2 Understanding where costs arise
1.3 What is a water balance?
1.4 Why produce a water balance?
1.5 How to use this guide
2
2
2
4
6
6
2 A six-step procedure for constructing/using a water balance
2.1 Step 1 – Obtaining top-level commitment and assessing the resources required
2.2 Step 2 – A preliminary review
2.3 Step 3 – Drawing up a water balance
2.4 Step 4 – Adding detail to the water balance
2.5 Step 5 – Using the water balance to save money
2.6 Step 6 – Continuous improvement
33
3
34
34
34
40
Dealing with more complex sites
3.1 Gathering more data
3.2 Finding out more about effluent flows
3.3 Using the water balance to save money
8
8
8
15
17
30
4 Action plan
43
5 Further information
44
1Why is
saving water
important?
2A six-step
procedure
Appendix A: UK charging schemes
46
Appendix B: Where do businesses use water?
58
Appendix C: Unit operations for a boiler and cooling tower 64
Appendix D: Example water balances
65
Appendix E: Producing and using site drainage plans
70
Appendix F: Calculating water flows for cooling towers and steam relief valves
71
Appendix G: Determining pollutant loads
73
3Dealing with
more complex
sites
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
1
Summary
Adopting a systematic approach to water
reduction can typically result in around 30%
water savings if no measures have previously
been implemented. A water balance is a
management tool that provides managers
with an overview of the major uses of
water on their company’s site, irrespective
of the company’s activity. When used to
control water use and effluent generation,
a water balance can help companies and
organisations of all sizes and types to reduce
water use, cut costs and increase profits.
This guide describes a six-step procedure for
constructing a water balance and explains
how this can help you to identify water and
cost saving opportunities.
The step-by-step approach to reducing water
use described in this guide involves:
1.Obtaining commitment and resources.
2.A preliminary review.
3.Drawing up a water balance.
4.Adding detail to the water balance.
5.Using the water balance to save money.
6.Continuous improvement.
Checklists and worksheets are provided
to help you investigate your water use and
effluent sources. Examples of cost savings
already achieved by companies are given
throughout the guide.
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
2
1 Why is saving water important?
Companies that
adopt a systematic
approach to water
reduction typically
achieve a 30%
decrease in the
amount of water
they use.
Most companies and organisations know how
much water they use, but may not always
use this knowledge to help them reduce
the amount of water consumed. Companies
that adopt a systematic approach to water
reduction typically achieve a 30% decrease in
the amount of water they use. By using less
water, companies save money on both water
supply and wastewater disposal. Taking action
to save water may also allow companies to
recover raw materials or product previously
lost in effluent streams.
This guide applies to both industrial and
commercial sites and will help you work out
where water is being used and where less
water could be used. Savings can be made
by companies of any size or type – including
companies that use comparatively little water
per site or per person.
Some sites have a finite water supply (e.g.
from the mains water distribution system
or groundwater and surface water sources),
making it difficult to increase supply to meet
any rise in demand. Increased availability
may also be expensive. Managing water
more efficiently can prevent any potential site
expansion being limited by the availability
of water or the need for an increased water
supply.
1.1 The true cost of water
The type of water used on site and the
type of wastewater generated by site
operations/activities will determine how
much your company pays for water supply
and wastewater disposal. Table 1 lists the
different types of water and wastewater.
Home
Table 1: Types of water and wastewater in the UK
Water is becoming an increasingly expensive
resource with mains, sewerage and trade
effluent charges rising. However, introducing
water efficiency measures is one of the
easiest and most inexpensive ways to achieve
cost savings.
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
Water sources
Wastewater types
¡¡ Mains water
¡¡ Domestic
¡¡ Water abstracted
¡¡ Trade effluent
(wholesome* and
unwholesome)
from groundwater
(borehole) and
surface water
wastewater
(sewage)
¡¡ Surface drainage
(roof and site runoff)
¡¡ Discharge to
surface water and
groundwater
* Drinkable.
There are a number of charging schemes for
water and wastewater (sewerage and trade
effluent charges) in the UK. The amount paid
depends on:
¡ the service provider;
¡ the size of the meter;
¡ the tariff structure agreed with your service
provider; and
¡¡ the year – unit costs are reviewed on an
annual basis.
Appendix A gives details of individual charging
schemes and how to understand your bills.
1.2 Understanding where costs arise
As well as easily identified costs such as
charges for water use, sewerage, surface
water and trade effluent, there are many
hidden costs associated with water use and
the disposal of wastewater. The true cost of
water may be more than three times the total
amount charged for supply and disposal.
Figure 1 shows the elements making up the
true cost of water.
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
3
Figure 1: The true cost of water
¡ Water charges
¡ Sewerage charges
¡ Effluent charges
Easily
identified costs
¡ Cost of energy to heat water
¡ Cost of chemicals for water treatment
¡ Cost of wasted energy (e.g. pumping)
Hidden costs
¡ Cost of chemicals for effluent treatment
¡ Cost of raw materials/product in effluent
¡ Cost of labour
Hidden costs can include:
¡ the energy costs associated with heating/
cooling water prior to use;
¡ lost product or raw materials in effluent,
resulting in sale losses and increased
effluent strength leading to higher trade
effluent charges;
¡ water treatment prior to use (e.g. ion
exchange or membrane technologies
such as reverse osmosis), including the
cost of chemicals for regeneration and
replacement columns/packing materials,
and the labour costs incurred in running
and maintaining these systems;
¡ pumping costs including energy, labour
and maintenance costs; and
¡ wastewater treatment prior to re-use or
discharge, including the cost of acid/alkali
for pH adjustment, flocculants, coagulants,
pumping costs, labour and maintenance.
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
Environmental review identifies true
effluent costs
An environmental review at a chemicals
company revealed that total effluent costs
were £23,000/year and not £4,000/year as
previously thought. The review also showed
that, as well as paying extra effluent charges,
the company was losing saleable product in
the effluent. Following improvements and
procedural changes, the company reduced
its effluent charges by £3,000/year and saved
£8,500/year through product recovery from
the effluent.
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
1.2.1 Added value water
Water treated before use has an added value
because time and money have already been
spent on it before it is used for its main
purpose. Table 2 summarises typical costs
of water.
Table 2: Comparable costs of different water types
Water type
Typical cost
UK mains supply
£0.60 – £1.83/m3*
Chlorinated water
£0.85 – £2.20/m3
Softened water
£1 – £2.16/m3
Demineralised/
deionised water
£2 – £3.70/m3
Condensate –
gas heated **
£3.70 – £4.86/m3
Steam – gas heated **
£29.71 – £30.87/tonne
* UK mains supply based on standard 2011/12 tariffs.
** E
nergy costs at 3.6p/kWh for gas and boiler efficiency
of 90%.
4
1.3 What is a water balance?
A water balance is a numerical account used
to show where water enters and leaves your
business, and where it is used within the
business. It typically contains information
about the amount of water used by each main
process and, for some processes, can be very
detailed. Presenting the water balance as a
diagram makes it easy to understand and use
as a management tool.
A water balance is based on the simple
concept: what goes in must come out...
somewhere (see Figure 2).
It is best to start by looking at your company
as a whole and then adding details as you go
along. It is also helpful to think of your site
or company as a series of blocks, with each
block representing an activity or location with
water inputs and outputs. Figure 3 shows
water inputs and outputs for a fairly simple
site; Figure 4 is a block representation of this
site.
Appendix B gives examples of water use in a
number of industrial and commercial sectors.
Figure 2: Water mass balance
Evaporation
Product
Water in
Leaks to ground
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
Effluent
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
5
Figure 3: Water inputs and outputs for an example site
Water
supply
1 6 4 02
Meter
Evaporation
and steam
Liquid
raw materials
Factory
laundry and washrooms
Factory shop
and canteen
Factory
Water in the product
Domestic wastewater/
trade effluent
Figure 4: Block representation of water inputs and outputs for an example site
Mains water
1 6 4 02
Liquid
raw materials
Factory
Equipment washing
Water added to
product
Boiler
Steam generation
Condensate recovery
Water softening
Laundry and
wash rooms
Toilets, handbasins
and showers
Washing machines
Tumble dryers
Product
Evaporation
and steam
Water in
the product
Leaks
C ondensate recovery
Evaporation
and steam
Meter
Shop and canteen
Toilets and sinks
Dishwasher
Food preparation
Boiler blowdown/
condensate
Domestic wastewater/
trade effluent
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
6
1.4 Why produce a water balance?
A water balance helps you to:
¡ improved compliance with current and
future environmental regulations;
¡ better relationships with regulators,
¡ understand and manage water and effluent
employees, the general public and the local
efficiently;
community;
Mains water
¡ identify the areas with the greatest
¡ improved environmental management; and
opportunities for cost savings; and
¡¡ greater employee awareness of
Meter
¡¡ detect leaks.
environmental issues and the importance
of waste minimisation to the company.
1 6 4 02
Evaporation
Evaporation
Liquid
Small
stopping leaks
and
steambrewery saves money
and steam
rawby
materials
C ondensate recovery
Remember
Monitoring water use allowed a brewer to
discover a significant water leak, which was
You can’t manage what you don’t measure.
Factory
due to three faulty control valves.
The valves
Equipment
washing
Laundry
and
were
replaced
at a total cost of £400,
leading
The waste hierarchy
is acanteen
framework
wash rooms
Shop and
3 Water added to
to Toilets,
reduced
water use of 10,800m /year.
productThis
handbasins
Toilets
and sinks
prioritising the most
environmentally
represented
Boiler in water
and showersa saving of £13,000/year
Dishwasher
desirable options for
waste. The principles
Steam generation
Washing
Food preparation
and
trade machines
effluent charges.
of the waste hierarchy when applied to water
Condensate recovery
Tumble dryers
Water softening (see Figure 5) consist of four levels of waste
The main benefits of using a water balance
management. Apply this hierarchy to each
to identify and implement
Water in opportunities to
process/area that uses water or generates
Leaks
Boiler
blowdown/at your site.
the product
reduce water use are:
wastewater
uct
condensate
¡ reductions in:
1.5 How to use this guide
-- water supply costs;
This guide explains how to draw up a water
Domestic wastewater/
-- on-site water treatment costs; trade effluent balance for your site and then use it to save
money by reducing water use.
-- on-site effluent treatment costs,
including chemicals and capital
For small to medium-sized sites, this involves
depreciation;
following the simple step-by-step procedure
-- effluent and sewage disposal costs;
described in Section 2. This procedure is
-- wasted raw materials or products; and
extended in Section 3 to cater for larger, more
complex sites. Section 4 presents an action
-- management and handling costs (e.g.
plan applicable to all sites.
pumping, maintenance and heating);
Figure 5: Waste hierarchy applied to water
1. Can you eliminate water use at source?
No
Yes
2. Can you reduce the amount of water used?
No
3. Can you re-use water/wastewater?
No
4. Can you recycle/recover water/wastewater?
ry shop
anteen
No
Calculate the cost of disposal
Implement water reduction
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
In this guide, the term domestic wastewater
is used for domestic water and sewage
discharged at the domestic sewerage rate.
Trade effluent refers to effluents from
industrial processes on which trade effluent
charges are levied, based on the strength as
well as the volume of effluent.
The step-by-step approach to reducing water
use described in this guide involves:
1.Obtaining commitment and resources.
2.A preliminary review.
7
Figure 6: The four phases of a typical water
saving campaign
PHASE 1 – Initiation
¡¡ Obtain commitment from senior
management.
¡¡ Involve staff and appoint the leader
(‘champion’) of the water saving team.
¡¡ Find out about water saving devices and
their application.
¡¡ Talk to other interested people in your
3.Drawing up a water balance.
4.Adding detail to the water balance.
company.
¡¡ Develop a simple programme.
¡¡ Allocate sufficient resources.
5.Using the water balance to save money.
6.Continuous improvement.
You may want to use this guide to help drive
forward a water saving campaign. Drawing up
a water balance for your site forms part of the
detail of a typical water saving campaign (see
Figure 6). This process is broadly similar for
industrial and commercial sites and usually
entails four phases.
Wholesale food distributor saves money
at over 100 sites
A wholesale food distributor fitted simple
water saving devices at 109 of its UK outlets.
For an average cost of around £675/site,
water use and wastewater production were
reduced by 65% overall. Each site saved on
average around £980/year, giving a total
reduction of £106,700/year.
Nearly 1% of turnover saved by recycling
process effluent
A Humberside company, employing
180 people, investigated cost-saving
opportunities while seeking improvements in
environmental performance. Investment of
£20,000 in new pipework and tanks allowed
a liquid waste stream to be recycled. This
has enabled the company to save £20,000/
year in effluent charges and £200,000/year in
increased yield and reduced disposal costs.
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
PHASE 2 – Water use survey and
development of a water
balance
¡¡ Identify where, how and why water is used.
¡¡ Identify the water quality requirement at
each point of use.
¡¡ Determine the water quality and
availability at each point of discharge.
PHASE 3 – Evaluation of water saving
options
¡¡ Evaluate current and future water costs
by area or item of equipment.
¡¡ Identify and evaluate cost-effective water
saving devices and practices.
¡¡ Carry out trials of likely options.
PHASE 4 – Implementation
¡¡ Train staff (if necessary).
¡¡ Implement cost-effective water saving
devices and practices.
¡¡ Monitor the implemented devices and
practices.
¡¡ Communicate successes and savings to
employees.
¡¡ Obtain feedback from staff.
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
8
2A six-step procedure for
constructing/using a water balance
For your water
efficiency
programme to be
a success, you will
need commitment
from senior
management.
Use the simple six-step procedure described
below to construct a water balance for your
site. Then use your water balance to identify
opportunities to make significant cost savings
by reducing water use and wastewater/
effluent generation.
2.1 Step 1 – Obtaining top-level commitment
and assessing
the resources required
2.1.1 Obtaining top-level commitment
For your water efficiency programme to be
a success, you will need commitment from
senior management. This should be obtained
at an early stage – particularly if you do not
have the necessary authority to commit
resources to produce a detailed water balance
or to investigate and implement water saving
opportunities.
It may be easier to obtain top-level
commitment once you have started to develop
your water balance and are in a position to:
¡ highlight current costs;
¡ identify the need for more information;
¡ suggest the scope for potential savings;
and
¡¡ highlight some ‘quick win’ opportunities.
Your chances of success will be significantly
improved if you can also suggest some no-cost
and low-cost water saving measures, together
with the anticipated costs and savings.
Examples from other companies may be
appropriate, but specific potential projects for
your site will carry more weight. Examples
might include fitting passive infrared (PIR)
controls in the men’s toilets or fitting water
saving taps.
2.1.2 Assessing the staff and resources
required
The time and effort needed to produce a water
balance depends on your site. On a simple
site, it could take only a few hours. On a more
complicated site, it could take significantly
longer.
Allocation of resources depends on the scale
of the process or the area to be investigated
(e.g. one person working part-time or a
mixed team of engineering, production and
environmental staff). Some companies have
successfully employed students on work
placements to gather data.
Work experience student helps brewery save
money
A brewer employed a graduate trainee to map
the water system, supervise the installation of
new water meters for each main production/
office area, and monitor subsequent
consumption. The waste reduction initiative
led to water saving measures and cost
savings of nearly £100,000/year.
2.2 Step 2 – A preliminary review
Your preliminary review should consist of:
¡ gathering existing data (e.g. annual water
use and costs);
¡ a brief assessment of the major gaps in
your information; and
¡ deciding how detailed a water balance is
appropriate for your company. This will
involve:
-- estimating potential cost savings from
water saving measures; and
-- deciding your budget for obtaining
missing information and/or constructing
a water balance.
For each process or area, use the checklist
given in Figure 7 to review water use and
wastewater generation.
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
9
Walk around your site or building. Use a
note-pad to make sketches and notes on
activities and operations that use water.
Tell other people what you are doing and
ask them for their views on water use and
current practices. Your tour of the site and the
information you obtain may highlight some
‘fast start’ projects that will help you to secure
top-level commitment.
Figure 7: Example water review checklist
Checklist
Comment
Process/area
¡¡ Is the process/activity really necessary?
Water use
¡¡ Is it necessary to use water for the process/
activity or is there a cost-effective alternative?
¡¡ How can I reduce water use?
¡¡ Could I use lower quality water?
¡¡ Can I recover and re-use water anywhere?
¡¡ Is the use authorised and legal?
Wastewater
¡¡ Is it necessary to produce this wastewater/
effluent?
¡¡ Is clean water going down the drain and,
if so, why?
¡¡ Is the discharge authorised and legal?
¡¡ Can the wastewater/effluent be re-used
in a process or used for lower grade duties
(e.g. cleaning)?
¡¡ Would it be cost-effective to treat the
wastewater/effluent on site for re-use?
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
2.2.1 Gather existing data
Table 3 provides a checklist of the type of
information you will need to produce a water
balance.
Start by collecting information that already
exists within the company. Check whether the
information appears accurate and consistent.
For example, check the meter readings on
your latest water bill and find out when your
water meter(s) was last calibrated.
10
To reduce the risk of errors in your
calculations, use the same units for water use
(e.g. litres or m3) depending on the size
of your flows.
Water volume conversion
1m3 = 1,000 litres = 220 gallons
1 gallon = 0.0045m3 or 4.5 litres
Table 3: Useful existing data
Type of data
Description
Water supply and treatment costs
¡¡ Water supply bills
¡¡ Abstraction licence fee
¡¡ Pumping, chemicals, operating, maintenance and
labour costs
Water treatment
¡¡ System type and capacity
Water and effluent quantities
¡¡ Meter readings in and out of site, on individual
machines/process areas
¡¡ Data on rainfall or groundwater inputs
¡¡ Analysis of on-site water treatment and effluent
Water and effluent quality
samples (either in-house, by external laboratories
or by water company)
¡¡ Equipment specifications from suppliers
¡¡ Pumping, chemicals, operating, maintenance and
Effluent treatment costs
labour costs
¡¡ Trade effluent and sewerage bills
Effluent discharge costs
¡¡ Charges for discharge to controlled waters
Effluent removed off site in tankers
¡¡ Waste disposal contractor’s bills for tanker
transport, treatment and disposal
¡¡ Quantities and quality of tankered liquids
¡¡ Water distribution and drainage plans, including
Site plans
water sources and location of meters
Details of process or unit operation
¡¡ Process flow and pipe/process technical drawings,
including manufacturers’ specifications
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
Locate your water meter
Most commercial and industrial properties
have a metered water supply. The water
meter is usually located by the boundary of
the property, often near a road. If the site has
more than one incoming water mains, each
supply should be fitted with a meter.
11
Correct meter size results in cost savings
Correcting the size of its water meter for
current operations meant that a carpet
manufacturer reduced its annual water supply
costs by 89% (£10,530).
As a minimum, your mains supply meter(s)
will allow you to monitor water consumption
of the site on a routine basis (daily, weekly or
monthly).
How to read your water meter
Metered companies are responsible for the
water use recorded on their meter – including
wastage and leaks.
Figure 8 shows a typical water meter. The
white digits in the ‘blue box’ display cubic
metres (m3) and those digits shown in red
display 1/10th (100 litres) and 1/100th
(10 litres) of a cubic metre. Thus, the reading
on the example meter shown in Figure 8 is
2004.87m3. The figures shown in the dials
provide a more detailed reading than 1/100th
of a cubic metre.
Other ways of measuring flow are described
in Section 2.4.5. Section 3.2.2 contains
information about flow meters.
Figure 8: Typical water meter
RIAL
SE
m3
8
7
9 0 1
Cert N .
o
8
7
2
3
9 0 1
6 5 4
2
3
0.001
6 5 4
0.0001
Home
1Why is
saving water
important?
2A six-step
procedure
Recording water consumption in a graphic
format makes it much easier to analyse your
pattern of water usage.
To ensure you compare like with like, it is
a good idea to normalise your data. For
example, express water use in terms of
production (m3 water per tonne of product)
or workforce (m3 water per employee).
This benchmark can be used to identify
excess use or to demonstrate genuine
reductions in water use.
NUMBE
R
CLASS:
Qn m 3/h
Pn bar
What to do with your meter data
Recording meter readings on a regular basis
(daily, weekly or monthly) will allow you to
identify trends in water consumption.
3Dealing with
more complex
sites
Figure 9 and Figure 10 present water
consumption data for an example site.
Although the data are recorded clearly in a
suitable format in the table (Figure 9), the
graph presented in Figure 10 shows the
water consumption trends more clearly.
The increase in water use from March to
August becomes very apparent.
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
12
Figure 9: Example of metered water
consumption at an example site
Month
Water use (m3)
2008
2009
2010
2011
January
170
140
213
February
153
127
220
March
170
150
317
April
160
147
307
May
170
150
377
June
103
120
560
July
93
120
573
103
120
573
August
September
177
193
187
October
180
200
197
November
177
193
187
December
173
147
213
Figure 10: Graph showing trends in water use at the example site
2008
2009
2010
2011
700
600
Water use (m3 )
500
400
300
200
100
0
Home
1Why is
saving water
important?
Sep
2A six-step
procedure
Key
?
Oct
To be assessed
Sub-meter
Nov
Dec
Jan
3Dealing with
more complex
sites
Feb
Mar
Apr
4Action plan
Mains water
May
Jun
Jul
Aug
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
WRAP’s monitoring tool is available at
www.wrap.org.uk and can help you to easily
record and track where water is being used in
your company and analyse your findings. There
are monitoring spreadsheets for recording
water consumption data once a week, five days
a week and seven days a week.
2.2.2 Are there major gaps in your
knowledge?
In your preliminary review, aim to account
for at least 80% of the water you pay for –
including any major leaks. Examine your data
and decide whether your overview of water
use and costs is adequate or whether there
are major gaps.
If more information is needed, it is likely to be
in specific areas. Investigating your main uses
of water (or higher value water – see
Section 1.2.1) is likely to provide most of your
cost saving opportunities.
Begin to develop a picture of your business –
along the lines of Figure 3 (see Section 1) – as
soon as possible. This will help you to identify
gaps in available information and to focus
your efforts. You will develop the picture and
add detail during Steps 3 and 4 (see
Sections 2.3 and 2.4 respectively).
You may prefer to leave the decision on what
extra information and measurements you
need until you have produced your first water
balance diagram (i.e. the equivalent of Figure
4 complete with numerical data). You will
achieve this in Steps 3 and 4.
2.2.3 How detailed a water balance should
you produce?
A simple water balance covering the few
largest water-using activities may be
sufficient to control and reduce major uses
of water and related resources. You need to
decide how detailed a water balance is likely
to be cost-effective for your company. How
far to go is a matter of judgement, about
which general advice is given below. You may
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13
also wish, at this stage, to define the scope
of future work (e.g. whether to analyse the
whole site or to consider one area in more
detail).
To decide how detailed your water balance
should be, consider the potential benefits
versus the cost.
¡ What is the likelihood of identifying costeffective opportunities to save water?
¡ How much money could you save?
¡¡ How much will it cost to investigate water
use in more detail?
For sites with significant water consumption,
the potential savings will be more than
sufficient to justify drawing up a detailed
water balance.
Water balance leads to halving of mains
water consumption
A soap manufacturer used a systematic
approach to identify and quantify water
use, and then implemented measures to
reduce mains water consumption. A detailed
water survey revealed how and where water
was being used. A water balance was then
prepared using data obtained from existing
invoices and meters. A 50% reduction in
mains water use and associated cost savings
were achieved over a period of four years
through a combination of good housekeeping
measures and plant modifications.
For sites that have relatively low water use,
an alternative criterion for deciding whether
to produce a detailed water balance is the
size of annual water and effluent bills. For
example, a multi-site organisation decided
not to investigate water saving opportunities
at sites where water and effluent bills were
less than £300/year. However, the installation
of simple, water saving devices, such as
percussion (push) taps, toilet cistern volume
adjusters and flushing controls, at over twothirds of its sites produced significant overall
cost savings.
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
2.2.4 Estimating potential savings
Cost savings can arise from reductions in:
14
Many people use at least twice as much
water as is needed to perform a given task
(e.g. washing down a piece of equipment
with a continuously running hose). Typical
reductions in water use for various projects
are shown in Table 4.
¡ water use (e.g. in domestic or process use);
¡ on-site water pumping and associated
maintenance;
¡ water treatment (e.g. lower chemical costs
and filter backwash);
¡ water heating or cooling requirements;
¡ effluent pumping;
¡ effluent treatment; and
¡¡ effluent discharge.
2.2.5 Deciding your budget
Once you have estimated the potential
savings, use your company’s method for new
project appraisal to determine how much
money might be available to obtain missing
information and/or construct a water balance.
As a general rule of thumb:
¡ if no water saving measures have so far
been implemented, savings could be 30%
or more of your water-related costs;
¡ if you have implemented some water
saving projects but not applied a systematic
approach, you may still make some
significant savings, especially where higher
value water consumption is reduced; and
¡¡ do not forget the possibility of reducing the
amount of raw materials and product lost
in effluent. This can be significant.
Identify the maximum project budget
Identification of the maximum project budget
can help to determine the areas on which
to concentrate. This helps to assess and
eliminate projects that are unlikely to be
cost-effective.
Maximum project budget (£) = Calculated
saving (£/year) × Required payback period
(years)
Table 4: Typical achievable reductions in water use
Water saving initiative
Typical reduction*
Per project
Per site
Commercial applications
Toilets, men’s toilets, showers and taps
40% (combined)
Industrial applications
Closed loop recycle
90%
Closed loop recycle with treatment
60%
Automatic shut-off
15%
Countercurrent rinsing
40%
Spray/jet upgrades
20%
Re-use of wash water
50%
Scrapers
30%
Cleaning-in-place (CIP)
40%
Pressure reduction
Variable
Cooling tower heat load reduction
Variable
* Assuming no water measures have previously been put in place.
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4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
2.3 Step 3 – Drawing up a water balance
This step involves:
For more complex sites, use a site plan and
process flow diagrams to help you produce a
pictorial representation of the site.
¡ producing a simple pictorial representation
of the site;
¡ translating this picture into a block
diagram; and
¡¡ adding volumes of major water and
wastewater flows to your block diagram
to produce an initial water balance.
When drawing your picture, remember that:
2.3.1 Produce a pictorial representation
of your site
For any water balance, the first step is to
produce a pictorial representation of your site.
All premises – whether a complex site or a
single building – can be described by a series
of activities or operations. Figure 3 in
Section 1 shows a typical example.
Identify and mark on your picture:
¡ major uses of water;
¡ the location of on-site water meters (there
is usually one on the mains supply entering
a site); and
¡¡ the points at which domestic wastewater
and/or trade effluent enter the site
drainage system.
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15
¡ you are looking for major water-using
activities as part of an operation, process
or a piece of equipment where:
-- water enters;
-- a function occurs; and
-- water or effluent leaves; and
¡¡ inputs and outputs may be in a different
form (e.g. liquid raw materials, steam
and product). To help you, examples of
water-using activities in a hotel and on an
industrial site are shown in Appendix C.
Define major water-using operations by the
type of activity carried out, such as cooking
or drying (i.e. removing water from product).
Alternatively, designate activity areas
according to boundaries where flows can be
measured easily. If a water-using operation
becomes unmanageable, try splitting it into
smaller units.
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
2.3.2 Draw a block diagram
Now translate your picture into a more
manageable form by drawing a block diagram
that indicates the relationships between
operations. Figure 11 shows the block
representation of Figure 3. The major waterusing activities at this site are the laundry/
washrooms, the factory and the shop/canteen.
Each major activity on the site is represented
by a box, which lists the significant water
uses. Water feeding to the different activities
is represented on the diagram by arrows
connecting the relevant boxes. Standard
practice is to show water inputs at the top and
water outputs at the bottom of the diagram.
All water, including the mains water supply,
should also be shown.
2.3.3 Add data to the diagram to produce an
initial water balance
To produce the water balance, add the
volumes of all major water and effluent flows
to the block diagram. The units used should
be consistent and are typically m3/day. Obtain
numerical values for water/effluent flows
from investigations and measurements (see
16
Section 2.4). Aim to produce as complete an
account as possible of where the water is
going on the site.
Use the information gathered in your
preliminary review to begin to construct a
water balance for your site. If necessary, use
a site plan and process flow diagrams to help
you. Add the information you can but, at this
stage, you may not be able to account for
a significant proportion of your water use.
In Step 4, you will add detail to your water
balance by carrying out more investigations
and measuring flows.
Figure 12 shows an initial water balance for
the example company depicted in Figure
11. At this stage, only certain flows have
been quantified (mains water input to the
site, water input to the factory, liquid raw
material input to the factory, water in the
product, wastewater output from the factory
and sewage/trade effluent leaving the site).
The completed water balance for this site is
shown in Figure 20 (see Section 2.4.7).
Figure 11: Block representation of a simple example site
Mains water
1 6 4 02
Liquid
raw materials
Factory
Equipment washing
Water added to
product
Boiler
Steam generation
Condensate recovery
Water softening
Laundry and
wash rooms
Toilets, handbasins
and showers
Washing machines
Tumble dryers
Product
Evaporation
and steam
Water in
the product
Leaks
C ondensate recovery
Evaporation
and steam
Meter
Shop and canteen
Toilets and sinks
Dishwasher
Food preparation
Boiler blowdown/
condensate
Domestic wastewater/
trade effluent
Home
1Why is
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4Action plan
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Appendices
0
Jan
WRAP
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
NovWater
DecUse to Cut Costs
Tracking
17
Figure 12: Initial water balance for a simple example site
Key
? To be assessed
Sub-meter
Inputs
Outputs
Mains water
Meter
Recirculation
Evaporation
and steam
Liquid raw materials
75m 3/day
Factory
Equipment washing
Water added to
product
Boiler
Steam generation
Condensate recovery
Water softening
Laundry and
washrooms
Toilets, handbasins
and showers
Washing machines
Tumble dryers
?
C ondensate recovery
?
?
?
1m3/day
Evaporation
and steam
?
85m 3/day
1 6 4 02
Shop and canteen
Toilets and sinks
Dishwasher
Food preparation
65m3/day
Water in
the product
Leaks
Boiler blowdown/
condensate
?
5m3/day
?
79m 3/day
Total
Domestic wastewater/
trade effluent
84m 3/day
For an example of a non-industrial site, see
the detailed water balance exercise for a
medium-sized hotel in Appendix D.
2.4 Step 4 – Adding detail to the water
balance
Now add detail to your initial water balance by:
¡ working out which activities/processes are
likely to use the most water under both
normal and abnormal operating conditions;
¡ measuring flows to add information to your
water balance; and
¡¡ continuing to account for more and more of
your total water input until you decide that
it is no longer cost-effective to make new
measurements.
Your preliminary review (see Section 2.2)
may have enabled you to account for 80% or
less of the site’s water use when you drew up
your initial water balance. Depending on the
amount of water you use, it may be
Home
1Why is
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sites
cost-effective to make measurements to
identify 95% or more of your water use. This
issue should have already been considered as
part of your preliminary review.
This step has various stages and involves:
identifying water supplies;
investigating water use;
identifying sources of effluent;
considering other water losses;
quantifying water use and effluent flows
through direct measurement, monitoring
and, where necessary, estimating nonprocess uses;
¡ recording your information as a water use
chart and on a spreadsheet;
¡ adding the data obtained to your block
diagram to complete your water balance;
and
¡ accounting for any discrepancies.
¡
¡
¡
¡
¡
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
2.4.1 Identify water supplies
The main water sources from which
organisations can obtain their water are shown
in Table 5. In most modern buildings, water
from the mains and any abstracted water
are kept separate from rainwater. When
looking at water sources, make sure there is
no crossover between these water systems.
Some companies collect and treat rainwater
for use within their processes.
Table 5: Main sources of water
Type
Supply route
Mains
Metered flow via
a water company
supply pipe
Surface water
abstraction
Extracted from a river,
stream, lake, reservoir
or canal
Groundwater
abstraction
Pumped from
borehole(s)
Rainwater collection
From a storage tank
18
¡ Is water treated on site? If so, how?
¡¡ How is water transferred (e.g. by pump,
gravity or manually)?
Figure 13 shows an example assessment
of site water sources. The next stage is to
measure flows (see Section 2.4.5).
Look at your water and effluent bills to get
an idea of the quantities of water used and
the amount of effluent discharged from the
site/area. Focus on the larger flows first.
2.4.2 Investigate water use
Depending how complex your site is, use
one or more of the following approaches to
identify and investigate major uses of water.
To help identify where water is used and
which activities/processes use the most
water, start by finding out about where your
water comes from and how it is treated and
distributed on site.
¡ How is water supplied to the site (e.g.
mains, river, reservoir and/or borehole)?
¡ Is water stored on site (e.g. in tanks or
lagoons)? What is the storage capacity?
¡ Walk around the site/process looking at
everything to find water-using points and
equipment.
¡ Identify the location of water meters and
discuss with staff where water is used in
their area.
¡ Where visible, trace water supply pipes
from sources to water use points.
¡¡ Obtain drawings of the water supply
system, where necessary.
At the same time, make a note of effluent
sources and trace pipework back to water
supplies. This will save you time and effort
later. The identification of effluent sources is
described in more detail in Section 2.4.3.
Figure 13: Example water sources assessment
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1Why is
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Source
Processes/
areas served
Treatment
Storage (type
and capacity)
Transfer
method
Use and
frequency
Quantity
(m3/day)
Mains
Product
None
None
Pumped
Production
hours
To be
investigated
Borehole
Product
Softening
Tank
(5m3)
Pumped
Downtime of
mains pumps
(5 days/year)
To be
investigated
River
Gardens
None
None
Pumped and
gravity
Summer
To be
investigated
2A six-step
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3Dealing with
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4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
When collecting data, also gather supporting
information such as:
¡
¡
¡
¡¡
2.4.3 Identify sources of effluent
The next stage is to find out where effluent is
generated and being disposed of.
number of employees on site or per shift;
type of product being produced;
number of lines operating; and
procedures (e.g. number of rinses or cycles
on washing operations).
You may wish to develop a diagram to help you
keep track of your findings. Such a diagram
can be particularly useful if no plan of the
water supply distribution system is available.
¡ Identify the points where water enters the
site or is abstracted on site.
¡ Trace the water supply pipes from these
points to any plant/equipment that uses
water.
¡¡ Draw a flow diagram of pipework
connections.
Water use survey helps wallpaper
manufacturer achieve significant savings
By mapping its site water services and
developing a water balance, a wallpaper
manufacturer reduced water consumption at
one of its sites by nearly 40%. These actions,
together with recommendations from process
improvement teams investigating site water
use, highlighted how water was being used
and where it was being wasted. Estimated
annual savings of £143,000 were achieved at
virtually no cost.
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19
¡ Obtain drawings of the effluent drainage,
surface water drainage and foul sewer
systems. If these are not available, it may
help to develop diagrams for your site.
Appendix E provides guidance on how to
produce and use site drainage plans to
identify sources of effluent.
¡ Walk around your site/process finding
out where water goes and looking for
sources of effluent. Make a note of your
observations.
¡ Talk to other people about where effluent
is produced.
¡¡ Locate any effluent meters or sampling
points.
As well as discharges to sewer or
watercourses, find out about liquid wastes
and slurries removed off site in tankers.
Use the list of typical effluent sources in
Table 6 to help you identify all your sources of
effluent and water losses.
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
20
Table 6: Typical effluent sources and water losses
Effluent sources/water losses
Examples
General
Water treatment units
Filter backwash, wet sludges, chemical spillages, ion exchange regeneration,
reverse osmosis effluents
Water storage, including boiler system
Leaks and overflows
Storms/surface water run-off
Additions to effluent drains
Groundwater
Infiltration to effluent drains
Fire-fighting water systems
Leaks, unnecessary use, wrong connections, safety/pump testing
Car park
Vehicle washing wastewater
Fuelling depot
Spilt fuel and oils to drain
Refrigeration units
Condensate
Laboratories
Condensate, cooling water, liquid effluents, mains water vacuum pumps
Drying processes
Evaporation
Hot processes
Steam, condensate
Oil interceptors
Water/effluent removal
Storage tanks
Bund water/effluent drainage, tank overflows, delivery pump/shaft seal leaks
Site cleaning
Hoses
Commercial
Laundry
Effluent, steam, evaporation from dryers
Kitchens
Effluent, steam, liquid wastes
Toilets/bathrooms/washrooms
Effluent, steam
Swimming pool and leisure facilities
Wash block effluent, swimming pool water
Boiler/heating systems/air-conditioning
Blowdown, condensate, steam
Gardens and water features
Excess water run-off, overflows
Vehicle washing
Effluent, detergents
Industrial
Home
Cooling tower
Blowdown, evaporation, spray/mist
Steam system
Steam leaks and relief valve discharges, steam trap condensate, steam and
evaporation, boiler scale and sludge, blowdown
Condensate recovery
Vent losses to atmosphere, leaks and overflows
Condensate
Loss to product, loss to drain (excluding recovery)
Process/production
Effluent, evaporation, water in product
Scrubbers/strippers
Overflows, mist/vapour
Safety showers
Leaks, unnecessary use
Effluent treatment plant
Treated effluent, sludge, aerosols, liquid wastes (e.g. reverse osmosis
concentrate)
1Why is
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3Dealing with
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4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
Domestic wastewater usually goes down a
foul sewer for treatment by your local water
company or sewerage provider. Uncollected
and uncontaminated rainwater should
preferably be discharged to a soakaway or to
a surface water drain.
To avoid unnecessary treatment charges:
¡ check that rainwater is not entering the
foul sewer;
¡ keep domestic sewage and surface water
drainage separate from trade effluent; and
¡¡ label or colour code all drains. Make sure
that staff are aware of the difference.
2.4.4 Consider other water losses
To complete your water balance, you need
to consider other ways in which water is lost
from your site/process, for example:
¡ water may ‘leave’ the site in product (e.g. in
soft drinks manufacture); and
¡¡ as steam (e.g. some food processing uses
large quantities of steam).
Without information about these other losses,
it will be difficult to complete a representative
water balance for your site.
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21
Remember to check for water losses in:
¡¡ products and by-products;
¡¡ emissions to atmosphere (e.g. evaporation,
steam, mist, spray and losses from
pressure relief valves);
¡¡ spillages, leaks and overflows;
¡¡ slurry and sludge wastes;
¡¡ hoses and taps left on;
¡¡ cooling water (including once-through); and
¡¡ leaks from underground tanks or pipes.
2.4.5 Quantify water use and effluent flows
Once you have identified all major water uses
and effluent sources, the next stage is to
place them in order from largest to smallest.
Do this through a combination of common
sense, your own knowledge and discussions
with other people.
¡ Starting with the largest anticipated water
use/flow, find out how much water is used
each time and how often it is used. Simple
but effective methods include recording
meter readings or timing water flow into a
container of known volume (see Figure 14).
¡ Starting with the largest effluent source,
find out how much effluent is generated
each time and how often it is generated.
The effluent flow may be the same as the
flow of water used.
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
22
Figure 14: Two simple ways of measuring flow, (a) record meter readings (b) using a bucket and
stopwatch approach
(a)
(b)
Bucket and stopwatch approach
Water flow can be measured either in
pipelines or in channels. There are numerous The direct measurement technique described
options for flow measurement, each with its
below involves performing a spot check on
Key
own advantages and disadvantages. More
the flow from a piece of equipment or process
Sub-meter
Mains water
details are given
in
Section
3.2.2.
using a bucket or another container and a
Inputs
stopwatch (or a wristwatch with a second
Outputs
You can quantify
flows in a number of ways.
Recirculation
hand). The flow rate can be calculated from
In order of preference,
are:
Values fromthese
earlier assessment
the volume of water/effluent collected over
shown in Figure 12
3 /day
85m
Meter
a known
time.
You may need to undo a pipe
Newly assessed values
¡ measure directly:
connection temporarily to allow water/
-- flow meter measurements; and
effluent to flow into your container. This
3 /day
0.05m 3/day
1m3/day
technique,1mwhich
will not be applicable to all
-- bucket and stopwatch approach;
Evaporation
Evaporation
Liquid
flows,
is
described
below.
¡ calculate
from other measurements
and steam
and steam
rawwhere
materials
75m 3/day
applicable;
5m 3/day
4m3/day
¡ Assess health and safety requirements
¡ calculate from manufacturers’ published
(e.g. use gloves and safety glasses).
Factory
information;
Equipment
Laundry and
¡ washing
Assemble equipment (e.g. bucket, timer,
¡ calculate
from typical use information; and
Water added
to
washrooms
Shop
canteen bucket
note-pad,
pen and rope
forand
lowering
product
Toilets, handbasins
Toilets and sinks
¡¡ estimate and
from
knowledge of the process.
into drain).
Boiler
showers
Dishwasher
C ondensate recovery
1 6 4 02
Steam generation
preparation
¡ Find a measuring point Food
where
it is possible
Condensate recovery
to catch all the flow in the bucket.
Water softening
Washing machines
Tumble dryers
65m 3/day
Water in
the product
≈ 5m3/day
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1Why is
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2A six-step
2A six-step
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procedure
Leaks
5m3/day
5m3/day
Boiler blowdown/
condensate
70 m3/day
3Dealing with
more complex
Total
sites
3
79 m3/day
4Action plan
5 Further Domestic wastewater/
trade effluent information
≈ 4m3/day
Appendices
WRAP
Tracking Water Use to Cut Costs
¡ Position the empty bucket and start
the stopwatch (or note the exact time)
immediately the bucket starts to catch the
flow.
¡ Remove the bucket, stop the timer and note
the time when the bucket is nearly full (but
not overflowing).
¡ Measure the contents of the bucket in litres
using either graduations on the bucket or a
measuring cylinder.
¡ Calculate the flow rate in litres/second by
dividing the volume of effluent collected in
litres by the number of seconds over which
collection took place.
¡¡ Alternatively, calculate the flow based on
the weight of the effluent and assuming the
effluent has the density of water (i.e. where
1kg of effluent occupies 1 litre).
Measure the flow at representative times,
including both continuous and intermittent
discharges. As this is a one-off measurement,
repeat the test to determine variations in
flows or average flow rates.
23
model and note any modifications. If possible,
compare these data with actual water use.
Savings are possible if the unit is operating
at above its recommended consumption.
Estimating water use based on knowledge
of the process
If necessary, you may have to estimate water
use based on your knowledge of the process.
For example, for a tank filled each time for
a pre-rinse and a wash, measure the tank
dimensions and calculate the volume of water
used. Remember to allow for partial filling or
overflows.
Take measurements to cover all operations
affecting water or effluent quantities. In
particular, check intermittent activities (e.g.
cleaning) where water use is often variable
and wasteful. More information about
measuring water use and flow is given in
Section 3.2.2.
Monitoring washing/cleaning operations
Monitor washing and cleaning operations by
estimating or recording hose or tap use (for
example, frequency, duration and flow rate)
and calculating water/effluent quantities.
Figure 15 shows an example calculation of
water use by a hose. The same calculation
can be applied to effluent generation.
Using manufacturers’ data
If direct measurement is not practicable,
consider obtaining data from manufacturers’
brochures, such as water use for washing
equipment. Take care to use data for the exact
Figure 15: Example calculation of water use by a hose
Calculation
Home
1Why is
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Result
Instantaneous flow/average flow rate
A
Measured
0.5 litres/second = 1,800 litres/hour
Length of event
B
Measured
2 hours
Amount/event
C
A×B
3,600 litres
Frequency of event
D
Measured
Twice a day
Daily total
E
C×D
7,200 litres/day
Daily flow
F
E/1,000
7.2m3/day
2A six-step
2A six-step
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procedure
3Dealing with
more complex
sites
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
Estimating non-process uses
If you have combined domestic and effluent
sewers, you may need to estimate domestic
sewage quantities. Typical values for domestic
water consumption are shown in Table 7.
Water use in toilets can be estimated from
the frequency of use and cistern volume.
WC cistern volumes can be calculated from
measurements obtained by gently tying up the
ballcock before flushing the toilet and filling
the cistern from a graduated bucket.
Use in washbasins can be estimated by
temporarily disconnecting the ‘U’ bend and
running the waste into a large, graduated
plastic bucket while using clean water to
simulate normal use, such as washing hands.
2.4.6 Record your information
When tracking water use, it is important to
keep accurate records of your findings for
future use. You can do this either as a water
use chart or on a worksheet.
Water use chart
Producing a simple block diagram will
help you to determine flows for your water
balance. Figures 16 and 17 show example
charts for a commercial site and an industrial
site respectively.
24
Table 7: Typical rates of domestic water use
Item
Average water use
Toilets
6 – 9 litres/flush
Sinks
3 – 6 litres/event
Showers
45 – 65 litres/event
(higher use for power
showers)
Baths
60 – 170 litres/event
Dishwasher
20 – 40 litres/event
Laundry
(washing machine)
60 – 100 litres/event
Vehicle washing
Ranges from 100 litres/
vehicle using buckets up
to 900 litres/vehicle using
a hose
Garden hose
8 – 30 litres/minute
(500 – 1,800 litres/hour)
Residential
occupant
150 litres/day/person
Employee
(full-time,
no canteen)
25 litres/day/person
Employee
(full-time,
with canteen)
40 litres/day/person
Figure 16: Water use chart: commercial example
Location:
Hotel
Unit operation:
Laundry
Date:
Time:
Investigator:
31/03/12
14.30 hrs
M Brown
Source: Mains water
Metered/unmetered
Home
1Why is
saving water
important?
2A six-step
procedure
Use 1: Washing machine
Use 2: Sink
Volume: 2.4m3/day
Volume: 0.24m3/day
3Dealing with
more complex
sites
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
25
Figure 17: Water use chart: industrial example
Location:
Brewery
Unit operation:
Cooling tower
Date:
Time:
Investigator:
31/03/12
10.30 hrs
D White
Source: Mains water
Metered/unmetered
Use 1: Make-up water
Use 2: Hose
Volume: 7m3/day
Volume: 5.4m3/day
Worksheet
Entering quantity and cost data on a
worksheet will help you use the water
balance to identify and prioritise water saving
opportunities (see Section 2.5).
Keep units consistent and choose the time
period that is most convenient for you.
The example worksheets shown in Figures 18
and 19 are based on weekly use.
Figure 18 shows an example worksheet for
a fictitious commercial site (the same site
used to produce the water use chart shown in
Figure 16). The number of times the sinks are
used is calculated assuming three employees,
each washing their hands eight times a day
for five days per week. The calculations
assume negligible use of liquid detergent/
fabric softener and negligible water losses
as steam/evaporation.
Figure 19 shows an example worksheet for a
fictitious industrial site (the same site used to
produce the water use chart shown in Figure
17). The amount of evaporation is calculated
from the volume of make-up water minus the
volume of blowdown and assuming no leaks
and/or overflows. The calculation assumes
that hose use amounts to 15 hours/week
(3 hours/day, 5 days/week) at a flow rate of
0.5 litres/second (1.8m3/hour).
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
4Action plan
5 Further information
Appendices
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
4Action plan
0.01
Sinks
5 Further information
* Use the time period appropriate for your site.
Total
0.1
Washing
machine
Laundry
Input/event
(m3)
Process
Water
120
120
Number of events
per week*
average 80 pence/m3
120 pence/m3
Hotel
M. Brown
Dept
Effluent discharge costs:
Water supply costs:
Review carried out at:
Review carried out by:
1.2
12.0
Total input
(m3/week)
£1.44
£14.40
Cost of input
(£/week)
0.01
0.1
Output/event
(m3)
31/03/12
120
120
Number of events
per week*
Effluent
Time: 14.30
Date:
1.2
12.0
Total output
(m3/week)
£0.96
£9.60
Cost of output
(£/week)
WRAP
Tracking Water Use to Cut Costs
26
Figure 18: Calculating the weekly cost of water use and effluent generation: example commercial site
Appendices
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
4Action plan
–
5 Further information
* Use the time period appropriate for your site.
Total
–
1.8
(per hour)
Hose
–
15
5
Water
make-up
Water
–
7
Number of events
per week*
Cooling
tower
Input/event
(m3)
Process
Dept
Blowdown
Time:
Date:
10.30
31/03/12
–
–
27.0
35.0
Total input
(m3/week)
–
–
£32.40
£42.00
Cost of input
(£/week)
2.0
3.0
1.8
–
Output/event
(m3)
7
7
15
–
Number of events
per week*
Effluent
14.0
21.0
27.0
–
Total output
(m3/week)
80 pence/m3 for hose use with moderate pollution assuming 42 pence/m3 for blowdown
(based on volume charges only)
120 pence/m3
Brewery
D. White
Effluent discharge costs:average
Water supply costs:
Review carried out at:
Review carried out by:
£5.88
–
£21.60
–
Cost of output
(£/week)
WRAP
Tracking Water Use to Cut Costs
27
Figure 19: Calculating the weekly cost of water use and effluent generation: example industrial site
Appendices
(a)
WRAP
Tracking Water Use to Cut Costs
2.4.7 Completing the water balance
Adding the information obtained from your
investigations of water use and effluent
generation to your block diagram should
enable you to complete your water balance.
In some cases, it may now be easier to expand
the diagram by dividing a‘block’ into two or
(b)
more activities.
The water balance should be a schematic
representation of your process showing:
¡ all known points of water flowing into the
process;
¡ all known points of water flowing out of the
process, as effluent, liquid waste, product
or evaporative loss (see Appendix F for
steam); and
28
¡¡ the amounts of these flows (in consistent
units).
In theory, the total of all the inputs should
equal the total of all the outputs for either
individual unit operations or the whole process.
However, this is rarely the case in practice.
Aim initially for an accuracy of ±10% on the
total amount of water you can account for.
Figure 20 shows the completed water balance
for the example company from Step 3 (see
Section 2.3). The company has now produced
data for all flows and identified major water
leaks from the factory. In this example,
84m3/day out of the input of 85m3/day of water
has now been accounted for.
Figure 20: Completed water balance for a simple example site
Key
Sub-meter
Inputs
Outputs
Recirculation
Values from earlier assessment
shown in Figure 12
Newly assessed values
Mains water
Meter
1 6 4 02
85m3/day
0.05m 3/day
1m3/day
1m3/day
Evaporation
and steam
Liquid
raw materials
Evaporation
and steam
75m 3/day
Factory
Equipment washing
Water added to
product
Boiler
Steam generation
Condensate recovery
Water softening
Laundry and
washrooms
Toilets, handbasins
and showers
Washing machines
Tumble dryers
Shop and canteen
Toilets and sinks
Dishwasher
Food preparation
65m 3/day
Water in
the product
≈ 5m3/day
4m3/day
C ondensate recovery
5m 3/day
Leaks
5m3/day
5m3/day
Boiler blowdown/
condensate
70 m3/day
≈ 4m3/day
79 m3/day
Total
Domestic wastewater/
trade effluent
84m 3/day
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
Further example water balances for an
industrial site and a hotel are shown in
Appendix D.
29
Before carrying out a ‘night flow test’,
switch off any automatic devices (e.g. urinal
automatic flushing devices), but don’t forget
to switch them back on afterwards. Calculate
the rate of water leakage from the difference
between the meter readings and the time
between meter readings.
If the inputs and outputs shown in your water
balance are not equal, consider:
¡¡ Where else is water coming from or
effluent going to?
¡¡ Are there hidden losses (e.g. an undetected
leak)?
¡¡ How accurate is the information?
¡¡ Can it be improved?
Alternatively, when no water is being used, lift
manholes and check for effluent flows.
There is also the possibility of groundwater
leaking into drains and stormwater/rainwater
additions to drains.
2.4.8 Account for discrepancies
As well as checking that there are no hidden
losses, it is also important to look for
inconsistencies in your data. Table 8 lists ways
of identifying inconsistencies.
Detecting leaks
The methods outlined in Table 9 will help you
to detect major leaks.
New meters identify expensive water leak
A company manufactures high-quality
packaging at one of its sites. Historically, the
site only metered incoming mains water, but
this did not provide sufficient information on
water use. As part of the company’s water
efficiency campaign, 28 meters were installed
around the site and water use was recorded
and monitored. A major leak, costing
£11,000/year, was identified and repaired.
Table 8: Identifying discrepancies in your water balance
Method
Reason for inconsistency/solution
General
¡¡ Incorrectly set valves or control systems, leaks, broken
Walk around site
valves, pipes or other equipment.
¡¡ Previously unidentified or cross connections, or unidentified
Hold discussions with staff
take-up by product.
Institute employee suggestion scheme
¡¡ Excessive or unnecessary use.
Hold ‘no-blame’ brainstorming
¡¡ Unknown or unauthorised use.
Check for recycled flows or re-use
¡¡ Double accounting.
Examine previous water and effluent
bills
¡¡ If changes cannot be explained by process modifications,
then investigate further. For example, relate water to output
(i.e. m3 per unit of production, department or area).
Meters
Check meters are read correctly
¡¡ Train staff.
Check for faulty meters
¡¡ Service and calibrate meters regularly.
¡¡ Perform tank level test (i.e. pass a known volume of water out
of a tank and check that the meter records the event correctly).
Check meters are suitable for
application and installed correctly
Home
1Why is
saving water
important?
2A six-step
procedure
¡¡ Check specification of size and type.
¡¡ Check proximity to pipework obstructions such as bends.
3Dealing with
more complex
sites
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
30
Table 9: Leak detection methods
Type
Method
Look
¡¡ Inside – walk around the site or process, examining water-using plant and supply
pipework carefully.
¡¡ Outside – look for lush vegetation or continuously boggy/damp areas. Check the
proximity of these areas to supply pipes.
Listen
¡¡ When the area is quiet, listen for drips or flow of water.
Test
¡¡ Carry out a ‘night flow test’ and listen for flow at meters:
-- read the water meter when all employees have left and all processes have
stopped;
-- read the meter again some time later before anyone returns and uses water; and
-- if the water meter shows a significant increase, suspect a leak and investigate
further. Use sub-meters around the site to carry out detailed investigations in
different areas.
Contractors
¡¡ Use a leak detection service provided by a water company or external contractor.
2.5 Step 5 – Using the water balance to save
money
As you carry out investigations for your water
balance, you may find taps left on, faulty
valves and leaks. You can often take action
to sort out such problems immediately.
Note down what you have done and record the
anticipated savings.
Many of the benefits of producing a water
balance arise from increasing people’s
awareness of the importance of using water
efficiently. However, the full effects will only
be gained by analysing each use of water
carefully.
2.5.1 Identifying opportunities to reduce
water use
Use the water balance to identify major water
uses and sources of wastewater/effluent
generation. Then use the checklist in Figure 7
(see Section 2.2) to help you analyse water
use and effluent generation. Your answers to
the questions in this checklist will help you to
identify opportunities to reduce water use and
thus save money. Photocopy this checklist as
necessary for use by your water saving team.
Suggestions for reducing water use are given
in Table 10. Many of these suggestions are
no-cost and low-cost measures. The others
are likely to cost more, but are still worth
considering.
Use the cost data from your completed water
use worksheet (see Section 2.4.6) to help
you prioritise and implement measures to
reduce water use and wastewater/effluent
generation.
Water balance leads dairy to significant cost
benefits and water savings
A detailed water balance prepared by staff
at a milk processing factory highlighted the
areas where significant amounts of water
were used and wastewater generated. A
major source of wastewater was evaporative
condensate. This warm and relatively clean
wastewater stream is now recovered, treated
by reverse osmosis and re-used for a number
of applications on site including boiler feed
make-up water and hot CIP operations.
The reliance on mains water has reduced
significantly, with potential savings of up to
1,100m3/day.
Ask the people who operate water-using
equipment for their suggestions for
reducing water use and wastewater/effluent
generation.
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
4Action plan
5 Further information
Appendices
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
4Action plan
5 Further information
High
Replace worn-out equipment with low-water use models. On dishwashers and washing machines,
also look for features such as quick washes for lightly soiled loads.
High
Low
Optimise the number of cleaning rinses and rinsing methods.
Replace manual cleaning with cleaning-in-place (CIP) automated systems.
Low
Encourage the use of showers rather than baths where possible.
Procedural changes.
Low
Low
Reduce need for washing by progressing from light/clean to dark/dirty items or production, re-using
wash water where possible.
Service equipment regularly to reduce unplanned downtime of machinery and associated washing
operations.
Preventive maintenance.
Low
Low
Low
Low
Low
Low
Production scheduling.
Repair leaking valves, seals and pipes, dripping taps and overflowing cisterns immediately.
Use leaflets, posters, stickers and department/group meetings to educate employees.
Equipment repair.
Environmental awareness and water
savings.
Promote with progress reports, competitions, suggestion schemes, etc.
Report water use and effluent generation daily or weekly so that excessive use can be identified and
remedial action taken immediately.
Real-time reporting.
Waste reduction culture.
Set staged goals for reducing water use.
Measuring to manage.
Key:Low = easy no-cost and low-cost measures (i.e. less than a few hundred pounds); High = higher cost, more detailed measures.
Operations
Improved
maintenance
Training
Monitoring
Collect rainwater for low-grade uses (e.g. garden watering and yard washing).
High-grade and low-grade water supply
systems.
Low
Reduce unnecessary garden watering or water with perforated pipes instead of a hose or sprinkler to
reduce water loss by evaporation.
High
Low
Potential cost
Use dry cleaning methods initially to minimise water use to one short wash (i.e. use scrapers or
brushes first to remove material from equipment for disposal as solid waste).
Ensure rainfall run-off (from uncontaminated areas) drains to surface water drains or collect for re-use.
Good housekeeping (i.e. using water
wisely).
General
Examples
Keeping foul sewer, trade effluent and
surface water drains separate.
Technique
Issue
WRAP
Tracking Water Use to Cut Costs
31
Table 10: Cost-effective water saving opportunities
Appendices
Home
1Why is
saving water
important?
2A six-step
procedure
Modification of operational techniques.
Operations
(continued)
3Dealing with
more complex
sites
4Action plan
5 Further information
Re-use cooling water for another use (e.g. washing) or re-use after treatment (e.g. in a heat
exchanger).
Re-use the last rinse – usually clean – as initial rinse of next wash cycle – usually dirty
(i.e. countercurrent rinsing).
High
Low
High
High
Consider using block valves (i.e. non-adjustable) instead of adjustable valves to avoid incorrect
settings.
Use air cooling instead of water cooling.
High
Use automatic controls where possible (e.g. automatic blowdown control).
Low
Low
Install tamper prevention devices (e.g. locks for valves) to prevent unauthorised adjustment.
Consider dry cleaning for clothes and fabrics.
Low
Use automatic shut-off valves for hoses (i.e. trigger guns) and tank filling pipework. Install push taps
on basins.
Low
Low
Install automatic flushing devices on urinals and/or reduce toilet cistern volumes.
Microwave food instead of boiling it.
Low
Use pressure reducers or flow restrictors to reduce water use (e.g. on hand washing basins and hoses).
High
High
Reduce the size of washing bowls or other vessels to decrease the amount of water needed to fill them.
Collect wash water, effluent, blowdown or condensate, treat it and re-use.
Low
Avoid washing rinses that overflow. Use a mixer or hot water or allow equipment to soak in order to
use water efficiently.
High
Low
Rinse items in a sink rather than under running water.
Use sprays or jets of high pressure water instead of larger quantities of low pressure water.
Low
Potential cost
Try to use machines (e.g. dishwashers and washing machines) only when they have a full load.
Examples
Tracking Water Use to Cut Costs
Key: Low = easy no-cost and low-cost measures (i.e. less than a few hundred pounds); High = higher cost, more detailed measures.
Matching quality and availability
to requirements to re-use water.
Replacement of process.
Improved instrumentation and control.
Technique
Issue
WRAP
32
Table 10: Cost-effective water saving opportunities (continued)
Appendices
WRAP
Tracking Water Use to Cut Costs
2.5.2 Examples to give you ideas
The following examples are intended to give
you ideas about how your company could save
money by reducing water use.
Company example 1
Water use in a commercial building was
monitored using water meters and a water
balance was developed. Comparison of water
use in different areas revealed markedly
different water use between two washrooms,
even though they were a similar size and
had a similar level of use. Investigations
identified a leaking pipe, a broken tap (water
was running continuously) and a faulty valve
leading to excessive water for toilet flushing.
Simple repairs saved 500m3/year of water and
associated wastewater charges.
Company example 2
During a survey of its water distribution
system, a company noticed that cooling water
was discharged straight to drain after only
one use. Following investigation, it proved
cost-effective to install a cooling unit to
enable water re-use.
Company example 3
Investigations at a site identified taps
running continuously in workshops to
provide cold drinking water (the supply
pipes came through hot process areas) and
to cool milk for tea. Significant amounts of
water and money were saved by installing
chilled drinking water fountains and small
refrigerators for milk or bottled water.
33
2.6 Step 6 – Continuous improvement
Your first water balance should be reviewed
and updated regularly. The review will allow
you to demonstrate that savings are being
made.
Regular recording of flows, water and effluent
costs, meter readings and updating of site
drainage plans will minimise the work
required during a water balance review.
During your regular review:
¡ gather more detailed data (if necessary);
¡ improve estimated data by measurement
or better estimation;
¡ update water supply and drainage system
drawings/plans as appropriate; and
¡¡ incorporate any relevant changes
(e.g. methods, products and employee
numbers).
With time, your water balance will become
increasingly accurate as you account for and
eliminate discrepancies (see Section 2.4.8).
To maintain motivation, let everyone in the
company know about the success of the
water saving initiative through your intranet,
via posters on notice-boards, in company
newsletters, etc.
Send regular reports to top-level
management to maintain their commitment
to water saving.
Company example 4
One company found that its water balance did
not ‘balance’; the site meter registered much
more water as being used than had been
measured. To investigate the discrepancy,
each water-using operation was examined
more closely. In one area, it was found that
a hose was frequently left on unnecessarily
during a washing operation. Fitting a
trigger gun to the hose solved the problem
and reduced water and effluent charges
significantly.
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
34
3 Dealing with more complex sites
Talk to the relevant
staff to obtain the
necessary details
and records.
At larger, more complex sites, it takes longer
to refine the initial water balance and to
identify and implement all cost-effective
water saving opportunities.
This section builds on Section 2 by explaining
how you can investigate water and,
particularly, effluent flows in more detail to
uncover further water saving opportunities.
3.1 Gathering more data
For Step 2 – A preliminary review (see
Section 2.2), it is necessary for more complex
sites to gather more data. Table 11 provides
other sources of information that will help
you to complete the water balance for a more
complex site.
3.2 Finding out more about effluent flows
For more complex sites, you need to
investigate:
¡ discharges to sewers and watercourses;
¡ effluent removed off site in tankers; and
¡¡ other liquid wastes (e.g. small quantities
removed from the site in drums).
Talk to the relevant staff to obtain the
necessary details and records.
Table 11: Additional relevant data for more complex sites
Subject
Details
Site levelling data
Site plan showing levels.
Drainage network details
Condition, age, size and materials of construction.
Water quality standards
Internal specifications for different plant/areas.
Water storage
System type and capacity.
Water and effluent transfer
Whether pumped, gravity-fed or manual.
Effluent removed from site
Use of tankers and drums.
Effluent disposal standards
Trade effluent consent conditions.
Effluent volume and strength
Basis for calculation and billing (i.e. application of Mogden
Formula).
Correspondence with regulators
Details of any problems or pollution incidents.
Rainfall data
Run-off volume and rate calculations (e.g. Met Office data).
Process details
Process equipment arrangements, sketches and plans.
Operational practices
Cleaning routines, number of employees and shift patterns.
Substances and chemicals
Quantities used.
Health and safety data sheets.
Future development proposals
Possible changes in production or number of employees.
Potential future costs
Changes to charging scheme.
Increases in treatment/disposal costs.
Forthcoming legislation.
Historical data
Home
1Why is
saving water
important?
2A six-step
procedure
Past environmental, engineering, health and safety reports.
3Dealing with
more complex
sites
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
3.2.1 Carry out a drain entry point survey
The points at which pipes or channels
containing effluent enter the site drainage
system are known as drain entry points.
Carry out a site survey of drain entry points,
measuring and recording all potential
effluent flows to the drains. Figure 21 shows
an example record from a drain entry point
survey for a fictitious site.
3.2.2 Examine each effluent flow in more
detail
You now need to examine the effluent
characteristics at each drain entry point.
Useful information includes:
¡ source of effluent;
¡ number of sources of each type of effluent;
¡ a description of the effluent (e.g.
temperature, clarity and colour);
Home
1Why is
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3Dealing with
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35
¡ what the water is used for to produce an
effluent (e.g. cleaning);
¡ possible contaminants (e.g. raw material,
product and detergents);
¡ details of the pipe or channel through
which the effluent joins the drainage
system;
¡ flow rate;
¡ whether the flow is intermittent or
continuous;
¡ frequency of flow; and
¡¡ duration of flow.
Record your observations and measurements
on a suitable worksheet. Figure 22 shows
an example worksheet for the same site as
Figure 21.
4Action plan
5 Further information
Appendices
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1Why is
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2A six-step
procedure
3Dealing with
more complex
sites
Number
1
Source (if known)
Not known
Stainless steel
Construction material
For each pipe/channel feeding into drain entry point note:
J. Smith
Silvery grey
Colour of pipe
Date:
Marked on map number:
Processing
Department:
Investigator:
Exact location:
50mm
Vertical
Horizontal or
vertical
31/03/12
2 of 3
Slight trickle
Is flow present?
Describe
Manhole in path by north face
14
Pipe diameter
Feeding to drain entry point number:
Building 3
Amberly Road
Location:
Site:
14.30
Cold, milky colour
Characteristics of flow
(e.g. hot/cold, clear/coloured, solids
present, odour).
Time:
WRAP
Tracking Water Use to Cut Costs
4Action plan
5 Further information
36
Figure 21: Example drain entry point survey sheet
Appendices
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
4Action plan
1
Number
Cleaning
Water use to
produce effluent
* Description as given on drain entry point survey sheet.
Oven cleaning
Source process
For each pipe/channel feeding into drain entry point note:
J. Smith
Intermittent
Intermittent or
continuous
Date:
Pipe,
stainless
steel, vertical
Foaming,
brown, hot
Description
of effluent
31/03/12
2 of 3
Detergents,
baked
and burnt
product
Possible
contaminants
Manhole in path by north face
14
Pipe or channel*
Marked on map number:
Processing
Department:
Investigator:
Exact location:
Feeding to drain entry point number:
Building 3
Amberly Road
Location:
Site:
Rate of flow, frequency
and duration (with units)
14.30
0.1m3/event including
rinsing.
Once every two weeks, plus
annual shutdown clean of
0.2m3
Time:
WRAP
Tracking Water Use to Cut Costs
5 Further information
37
Figure 22: Example effluent source information sheet
Appendices
WRAP
Home
Tracking Water Use to Cut Costs
38
Measuring flow rates
Consider the following questions before
selecting a flow measurement system or
contacting a supplier of flow measurement
equipment:
Flow measurement systems
Flow measurement systems are summarised
in Table 12. Note that the accuracy of flow
measurement equipment is affected by the
proximity of:
¡ What level of accuracy is required?
¡ Will the flow rate obtained by ‘bucket
and stopwatch’ methods be sufficiently
accurate?
¡ How big are the pipes and can they
be opened to insert an invasive flow
measurement system?
¡ What are the temperature, pressure and
range of speed of the water/effluent?
¡ Is the water clean or dirty? If dirty, what is
the nature of the contamination?
¡ Is pipework old and corroded? Corrosion
can cause problems for strap-on flow
meters.
¡ Is pipework insulated or trace heated?
¡ Will a pressure drop across an invasive
metering element be acceptable?
¡¡ Is a signal for output to online monitoring
or recording systems required?
¡ valves;
¡ bends; and
¡¡ other items that affect the flow of water/
effluent.
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
One benefit of using flow measurement
systems is that the electrical signals
produced by such systems can be collected in
data loggers for trend analysis.
Dip tube method
Another method of measuring the water
level is a variation of the pressure technique.
This uses a small dip tube to gently blow
air bubbles into the water from below the
surface. The amount of excess air pressure
required to expel air is related to the depth
of water above the end of the dip tube; the
deeper the water, the higher the pressure
required to expel air.
4Action plan
5 Further information
Appendices
Home
1Why is
saving water
important?
2A six-step
procedure
I
I
Orifice (B)
Magnetic
3Dealing with
more complex
sites
4Action plan
–
–
Bucket and stopwatch
Drop tank test (E)
Rate of change of depth of tank
Time taken to collect a known volume
Level upstream of flume
Level upstream of weir
Doppler for flow pressure for depth
Reflections from particles in water
Vector addition of velocities
Rate of cooling
Distortion of magnetic field
Pressure differential
Variable area
Rotation of turbine blades by flow
Principle
Key:
I=
invasive
N = non-invasive
CW = clean water
DW = dirty water
SDW = slightly dirty water
P=
pipe
C = channel
*Some new systems will measure flow in part-full pipes.
(A), (B), etc: see overleaf for notes on these different systems.
I/N
Flume (D)
I
Ultrasonic plus pressure
I/N
I/N
Ultrasonic (C) – Doppler
Weir (D)
I/N
Ultrasonic (C) – time-of-flight
I
I
Rotameter
Thermal dilution
I
Type
Turbine (A)
Sensor element
CW/DW
CW/DW
CW/DW
DW
DW
CW/SDW
CW/DW
CW/DW
CW
CW
CW
Applicability
C
C
P/C
P
P
P/C
P
P
P
P
‘Spot’ flow measurement
‘Spot’ flow measurement
Settling solids will require removal
Settling solids will require removal
Small weir may be required
Will not work in clean water
Might not work in dirty water
Must remain full*
Solids may block pressure tappings
Must be vertical
Solids or solvents
Common problems
WRAP
Tracking Water Use to Cut Costs
5 Further information
39
Table 12: Commonly used flow measurement techniques
Appendices
WRAP
Tracking Water Use to Cut Costs
(A) Turbine meters
Turbine meters usually provide a direct visual
display of cumulative flow. Instantaneous flow
signals can usually be acquired from optional
sensors which bolt onto the turbine casing
and provide pulsed electrical outputs.
Installing a few inexpensive turbine-type
water meters at key points in the water
distribution system can enhance the results
obtained from a water use survey. A flow
meter for a 12.5mm (1/2”) pipe costs about
£45 and for a 50mm (2”) pipe about £200.
(B) Orifice meters
Numerous versions of inexpensive orifice
meters, which give direct readings of
instantaneous flow, are available.
(C) Ultrasonic meters
Strap-on ultrasonic flow meters can give
good results, but older pipework may cause
problems.
(D) Weirs and flumes
Levels at weirs or flumes, and hence the flow,
can be measured non-invasively by ultrasonic
distance measuring systems or invasively by
pressure gauges.
(E) Drop tank test
These can be used to calibrate flow
measurement systems.
It is important to consider the composition of
the effluent.
¡ Foam on the surface of effluents can cause
problems with ultrasonic systems.
¡¡ Effluent with a high solids content can
block standard pressure transmitters.
Large diameter diaphragm-based pressure
systems may be more suitable in such
cases.
3.2.3 Cooling towers and steam relief valves
If your site has cooling towers and/or steam
relief valves, use the simplified approach
described in Appendix F to calculate water
use and losses. However, a more costeffective approach to determining water use
by a cooling tower is to fit a water meter on
the make-up water pipeline.
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40
3.3 Using the water balance to save money
3.3.1 Using the results of the water balance
For Step 5 (see Section 2.5), the water balance
should also be used to identify:
¡ opportunities to reduce water use and
wastewater/effluent generation. It is possible
to reduce cleaning costs by up to 60%; and
¡ materials present in the effluent that
contribute to pollution load (for which
you pay higher trade effluent charges).
Look for ways of eliminating or reducing
the presence of these materials. Such
materials include:
-- raw materials;
-- products;
-- by-products; and
-- wastes.
You could save a substantial amount of
money by recovering raw materials and
product from your effluents. Section 3.3.3
describes how to calculate the pollution load
and the associated reduction in trade effluent
charges.
Chemical company recovers product worth
£200,000/year from process effluent
An investment of £20,000 in new pipework
and tanks enabled a chemical company to
recycle a liquid waste stream. This saved the
company £20,000/year in effluent charges
and £200,000/year in recovered product and
reduced disposal costs.
3.3.2 Consider options for water re-use
In some cases, it may be possible to re-use
wastewater/effluents directly for another
duty (e.g. low-grade cleaning) or to treat the
effluent for water re-use and/or recovery of
materials.
When considering water re-use, assess
quality requirements and potential problems
by talking to operators, equipment suppliers
and your maintenance, quality control and
health and safety departments.
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
Factors you should consider include:
¡ water quality (as a minimum):
-- pH;
-- temperature;
-- chemical oxygen demand (COD);
-- dissolved and suspended solids;
-- specific substances used in the process;
-- microbiological concentrations; and
-- toxicity issues;
¡ water availability;
¡ frequency of use;
¡ variability; and
¡¡ flow patterns.
Major savings with improved cask washing
process
A brewery knew that its cask washing
plant used water inefficiently. A quality
improvement team formed to evaluate the
washing process identified a number of
opportunities to achieve major savings.
Final rinse water from cask washing is now
recovered and re-used in other stages of the
process (i.e. external rinses, pre-rinses, oil
cooling/bung finding equipment and conveyor
washing). Water consumption at the brewery
fell significantly to give annual savings worth
£23,000.
3.3.3 Reduce the pollution load
Pollution load in an effluent is commonly
expressed as:
¡ COD - this is a measure of the potential
oxygen requirement of an effluent during
natural breakdown of the polluting
substances (i.e. its pollution potential); and
¡¡ total suspended solids (TSS) - this is a
measure of solids present in the effluent.
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Appendix G provides formulae to help you
calculate the pollutant load and concentration
of a pollutant in an effluent.
The benefits of investigating and
implementing measures to reduce the
pollution load include:
¡ reduced material losses to drain, leading
to increased profits;
¡ reduced trade effluent charges (see
Appendix A);
¡ recovered raw materials (usually the
largest cost saving); and
¡¡ reduced load on effluent treatment plant
and other equipment.
In some cases, it may also be possible to
increase concentrations to the point where
material recovery becomes cost-effective.
To determine the concentration of material
in an effluent flow:
¡ obtain a laboratory analysis of a
representative sample; or
¡¡ calculate the average concentration based
on the volume of effluent and the quantity
of substance used. You will need to allow
for the amount of substance released as
product or to another waste stream, and
thus not released in the effluent. This
calculation will only provide a guideline
figure.
It is important to remember that material
concentrations in an effluent could vary
considerably owing to the nature of the
process and the timescales involved.
Advice on how to calculate concentrations
and pollution loads for mixed flows is given in
Appendix G.
4Action plan
5 Further information
Appendices
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Tracking Water Use to Cut Costs
42
Figure 23: Example annual effluent pollution load block diagram
Location:
Confectionery
Unit operation:
Sweets production
Flow 1: Toffee cooker
COD
770kg/day
TSS
50kg/day
Flow 2: Milk make-up vessel
Volume
1 ,630m3/day
COD
185kg/day
TSS
23kg/day
Volume
15m3/day
Flow 3: Polishing pan cleaning
COD
65kg/day
TSS
7kg/day
Volume
55m3/day
Total effluent
COD
1,020kg/day
TSS
80kg/day
Annual pollution load
Use your information to calculate the
pollution load (e.g. on an annual basis) for
the different flows. Figure 23 shows this
information for an example factory (with three
flows) displayed as a block diagram.
Use the information in your diagram to
identify unnecessary or excessive pollution
loads. Then consider ways of reducing the
pollution load. Use Appendices A and G
to estimate how much you would save by
reducing the COD of your trade effluent.
Don’t forget to count the cost of recovered or
avoided materials in the savings.
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Volume
1,700m3/day
Investigate those flows with a high pollution
load. Find out:
¡ why the pollution load (i.e. COD or TSS) is
so high;
¡ if the pollution load can be reduced; and
¡¡ if the flow can be reduced.
Water companies use the Mogden Formula
(see Appendix A) to calculate trade effluent
charges. Reducing both the volume and the
load of an effluent will reduce your costs.
However, it is important to note that water
saving measures that reduce individual
effluents with a low pollution load will
increase the average concentration of the
overall effluent. It is therefore essential to
check before taking action that the site’s
trade effluent consent conditions will not be
breached.
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
43
4 Action plan
Your organisation
will have its own
goals determined
by its own policies
and practices.
You should now be in a position to begin to
develop an action plan to identify activities
to improve water use in your organisation.
You should be able to identify some of these
priority areas by looking at the data you have
gathered. Your organisation will have its own
goals determined by its own policies and
practices. However, the easiest and lowestcost actions will probably be carried through
first as they do not require capital investment
or time commitments and produce results
that can be seen very quickly.
Development of a water balance should be
carried out as part of a campaign to reduce
water use and wastewater generation at your
site. A systematic approach to reducing your
water use is described in the WRAP guide
‘Saving Money Through Resource Efficiency:
Reducing Water Use’ (www.wrap.org.uk)
and the four phases of a typical water saving
campaign are shown in Figure 6 (see
Section 1.5).
If you want to reduce your water and effluent costs
Find out how much your organisation is paying in water and effluent charges.
Construct a water balance for your site by following the six-step procedure
described in this guide.
Use your water balance to identify opportunities to reduce water use and
effluent generation.
Estimate potential savings from reducing water use and effluent generation.
Agree targets.
Identify and evaluate measures to reduce water use and effluent generation.
Implement cost-effective measures and monitor progress.
Review your water balance regularly.
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Appendices
WRAP
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44
5 Further information
Useful sources of information
WRAP guides and tools
¡ Saving Money Through Resource Efficiency: Reducing Water Use.
¡ Reducing Your Water Consumption.
¡ Resource Efficiency for Managers.
¡ Environmental Strategic Review Guide.
¡ Waste Mapping: Your Route to More Profit.
¡ Workforce Partnerships for Resource Efficiency.
¡ Green Office: A Guide to Running a More Cost-effective and Environmentally Sustainable
Office.
¡ The Rippleffect: this provides a wealth of free advice and support to help your business to
save money by using water more efficiently.
¡ Mogden Formula tool.
¡ Water monitoring tool.
Useful links
¡The Federation House Commitment: an agreement by companies in the food and drink
industry to reduce their water use www.fhc2020.co.uk/fhc/cms/
¡ Water Technology List: Visit www.hmrc.gov.uk/capital-allowances/fya/water.htm or call
0844 875 5885.
The following agencies offer advice on regulations affecting water use and wastewater
discharge:
¡ Environment Agency: Tel: 03708 506 506 www.environment-agency.gov.uk
¡ Environment Agency Wales: Tel: 0370 850 6506
www.environment-agency.gov.uk/aboutus/organisation/35675.aspx
¡ Scottish Environment Protection Agency (SEPA): Tel: 01786 457700 (Corporate Office)
www.sepa.org.uk
¡ Northern Ireland Environment Agency (NIEA): Tel: 028 9262 3100 (Water Management
Unit) www.doeni.gov.uk/niea/
The following organisations are regulators of the water and sewerage industry in the UK:
¡ Ofwat: The Water Services Regulation Authority (Ofwat) is the economic regulator of the
water and sewerage industry in England and Wales. Tel: 0121 644 7500
(www.ofwat.gov.uk)
¡ Water Industry Commission for Scotland: Tel: 01786 430200 (www.watercommission.co.uk)
¡ Utility Regulator (Northern Ireland): Tel: 028 9031 1575
(www.uregni.gov.uk/)
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45
WRAP
WRAP (Waste & Resources Action Programme) works in England, Scotland, Wales and
Northern Ireland to help businesses and individuals reap the benefits of reducing waste,
develop sustainable products and use resources in an efficient way.
Since its creation WRAP has funded projects that will, over their lifetimes, deliver over
120 million tonnes of waste diverted from landfill and over 20 million tonnes of CO2
equivalent greenhouse gases saved. Visit www.wrap.org.uk for more information on
all of WRAP’s services.
What support can you get from WRAP?
UK businesses could save £23 billion per year and help create and protect jobs by improving
the way they use resources.
WRAP provides a range of free resource efficiency support for organisations including:
¡
¡
¡
¡
¡
¡¡
WRAP Resource Efficiency Helpline on 0808 100 2040;
online tools and guidance;
online training initiatives;
tailored business support for recycling companies;
case studies; and
guides.
Visit www.wrap.org.uk to find out more.
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46
Appendix A: UK charging schemes
This appendix provides information on UK
charging schemes for April 2011-March 2012.
However, such schemes are subject to change
and updating. For the latest information on
charging schemes affecting your site, please
contact your local water company, sewerage
undertaker or the regulator.
There is considerable variation throughout
the UK with respect to charging for water
and effluent services. There are a number of
factors that affect charging, including:
¡ the service provider;
¡ the size of the meter;
¡ the tariff structure agreed with your service
provider – water volume is banded and
the band into which a company falls will
determine the charging tariff; and
¡¡ the year – unit costs are reviewed on an
annual basis.
This appendix provides information about how
water and effluent bills are calculated to help
you understand:
¡ how your site is being charged for water
use and wastewater discharge; and
¡¡ the effect on your site’s charges of different
measures to reduce water use and effluent
generation.
Details of UK charging schemes are
summarised in Table A11 at the end of this
appendix. The type of information provided on
a water bill and a trade effluent bill, together
with explanatory notes, is shown in Figure A1
and Figure A2 respectively.
Get into the habit of comparing meter
readings on your bills with your own records.
This is particularly important when your bills
are based on estimated readings.
Figure A1: Information given on a water bill
Water Company
1 Refers to
Meter serial no:
pipe size (mm)
Meter location:
Customer address:
Meter size (actual):
(agreed):
No. dials:
the number
shown as
white digits
Tariff:
Customer reference:
Period:
2 Refers to
3 Dictates
to
unit costs
Water charge
Present reading:
X
Y
Previous reading:
Pence/m
m3
3
5 Relates to agreed
pipe size
4 Unit cost related
£
to tariff –
see note 3
Volume:
6 Only applies to a
Sewerage charge
few water companies Unit costs are specific to
8 the water provider and
May
appear
on
7
will change each year
t rade effluent bill
3
3
i.e.Factor
Pence/m
m
£
X –Y
Standing charge:
Non-return to sewer
allowance – specific to 9
each water company
TOTAL CHARGE
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47
Figure A2: Information given on a trade effluent bill
1 Refers to
Water and
Sewerage Company
pipe size (mm)
eed):
Customer reference:
Consent no:
Customer address:
Sample point:
2 Refers to
the number
shown as
white digits
Period:
Date A
Date B
to
3 Dictates
unit costs
5 Relates to agreed
pipe size
£
1
The water company will
take 4-6 samples a year 2
to analyse for COD and
suspended solids
Refers to trade
effluent consent
agreement
m3
total m3
Trade effluent volume
X
X
LESS volume allowances
m3
3
Steam losses
Water in product
You will be asked to
provide data/calculations
for these allowances
Other allowances/losses
Y
LESS domestic volume adjustment
£
No. of employees or full-time equivalents
4
No. of days worked in period
You will be asked to
provide this information
Canteen present?
Daily per capita consumption (litres/head)
Z
Average strengths and solids
Average suspended solids mg/litre (St)
5
Average COD mg/litre (Ot)
See note 2
CHARGING DETAILS
Trade effluent
Charge = (R + V + Bv + M + [B(Ot/Os)] + [S(St/Ss)]) x volume of effluent (m 3)
Flow = (X-Y-Z)m
Pence/m3
R
C = Flow x R
V
C = Flow x V
Bv
C = Flow x Bv
M
C = Flow x M
B
C = Flow x (S x St/Ss)
S
C = Flow x (B x Ot/Os)
mg/litre
Os
6
Ss
R
V
Bv
M
B
S
Os
Ss
Domestic charge
£
Unit costs are specific to
the sewerage undertaker
and will change each year
Reception charge
Primary treatment charge
Additional volume charge (if there is biological treatment)
Marine charge (effluent goes to sea)
Biological treatment charge
Sludge treatment charge
Chemical oxygen demand of settled sewage
Suspended solids concentration in crude sewage
Volume (m 3)
Pence/m3
Z
TOTAL CHARGE
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Water use
Mains supply
Charges for mains supply consist of two
components:
Annual charge
= standard charge + compensation charge
= (V × A × B × C × SUC) + (V × B × C × D × EIUC)
¡ standing charge – a fixed annual sum,
determined by the size of the meter; and
¡¡ volumetric charge – a unit cost (pence/m3)
charged on the actual amount of metered
water used on-site. For a standard user
tariff, the average cost of mains supply
water for the UK is £1.20/m3 (2011/2012
prices), ranging from around 60p/m3 to
£1.83/m3 depending on the service provider.
The cost is subject to conditions (see
below).
Unit costs are revised each year in April and
vary between service providers. For an
up-to-date list for England and Wales, visit
www.ofwat.gov.uk
An example water bill is shown in Figure A1.
For details of individual charging schemes,
contact your service provider.
Abstraction from borehole or surface water
A charge for the abstraction of water from
groundwater (borehole) or surface water
(river, stream etc) applies to companies based
in England, Wales, Scotland and Northern
Ireland.
Abstractors are advised to consult their local
regulator for up-to-date advice.
Charges in England and Wales
The annual charge payable under the
abstraction licensing system administered
by the Environment Agency is the sum of
the standard charge and the compensation
charge, calculated according to the following
formula.
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where: V = Volume specified on the licence (in thousand m3)
A = Source factor (supported, unsupported or tidal)
B = Season factor (summer, winter or all year)
C = Loss factor (high, medium, low or very low)
SUC = Standard Unit Charge (£ per thousand m3)
D = Adjusted source factor
EIUC = Environmental Improvement Unit Charge (£ per thousand m3)
¡ Volume. The annual charge is calculated
from the volume (V) specified on the licence
(in thousand m3) rather than volume
abstracted.
¡ Source factor. The source factor (A)
consists of three categories:
-- Unsupported (factor 1.0) – where
‘supported’ and ‘tidal’ do not apply;
-- Supported (factor 3.0) – if the source of
the authorised abstraction is included in
Schedule 1 of the Environment Agency
Scheme of Abstraction Charges; and
-- Tidal (factor 0.2) – refers to those parts
of inland waters downstream of the
normal tidal limit as marked on the
1:25000 Ordnance Survey map.
¡ Season factor. The season factor (B)
consists of three categories:
-- Summer (factor 1.6) – abstraction
authorised between 1 April and
31 October inclusive;
-- Winter (factor 0.16) – abstraction
authorised between 1 November and
31 March inclusive; and
-- All year (factor 1.0) – abstraction
authorised all year or not covered by
either of the above categories.
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
¡ Loss factor. The loss factor (C) consists of
four categories:
-- High loss (factor 1.0) – spray irrigation,
dust suppression and other purposes
where, due to evaporation, water use is
not returned either directly or indirectly
to any source of supply;
-- Medium loss (factor 0.6) – public
and private supply, commercial and
industrial purposes not specified
elsewhere, boiler feed, use as a means
of conveying material, bottling and uses
which incorporate water in the product,
agricultural purposes (excluding spray
irrigation, fish farms and watercress
growing) and anti-frost spraying;
-- Low loss (factor 0.03) – includes mineral
and vegetable washing, and nonevaporative cooling; and
-- Very low loss (factor 0.003) – power
generation of greater than 5MW, amenity
pools through flow, hydraulic testing,
fish farms, watercress growing, and
effluent dilution.
¡ Standard Unit Charge (SUC). This refers to
the fixed charge for the region in which the
abstraction is authorised (in £ per thousand
m3) and is subject to annual review. The
average SUC in 2011/2012 across nine
regions in England and Wales was around
£17.7 per thousand m3. This equates to
1.7 pence/m3 and is considerably cheaper
than mains supply water. However,
abstracted water may require treatment
(e.g. softening) before use.
¡ Adjusted source factor. The adjusted
source factor (D) consists of two categories:
-- Non-tidal (factor 1.0) – for supported and
unsupported sources; and
-- Tidal (factor 0.2).
¡ Environmental Improvement Unit Charge
(EIUC). This funds compensation for the
Restoring Sustainable Abstraction (RSA)
programme and is collected on a regional
basis.
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An abstraction licence is not required under
the following conditions:
¡ abstraction of less than 20m3 per day,
used for any purpose;
¡ water used for fire fighting; and
¡¡ with the regulator’s consent, abstraction
of more than 20m3 per day to test
underground strata for the presence,
quantity or quality of water.
There are several other cases where an
abstraction licence may not be required,
but it is advised that you check with the
Environment Agency if in any doubt.
Charges in Scotland
Under the Water Environment (Controlled
Activities) (Scotland) Regulations 2011
(CAR), a CAR authorisation is required for
abstraction from surface waters and
groundwaters.
Annual subsistence charges will apply to
licensed abstractions.
The abstraction subsistence charges are
calculated for a licence and not for each
individual controlled activity. This is because
abstraction licences can include large
numbers of activities managed within a
single scheme. Monitoring and regulation is
undertaken at the scheme level. In calculating
abstraction charges, operators will only be
charged once for the abstraction of water.
Abstraction costs will be allocated between
activities according to eight factors:
Subsistence (annual) charge (£) =
Va × Lo × Le × So x Se × Pa × Na x Fa
where: Va = Volume abstracted factor (applies to the maximum
daily volume authorised)
Lo = Loss factor
Le = Length affected factor
So = Source of abstraction factor
Se = Seasonality factor
Pa = Proportion of flow factor
Na = Number of abstractions factor
Fa = Financial factor
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50
Table A1: Charges in Scotland – components, bands and factors
Component
Band
Factor
Va
More than 0m3 to 50m3 per day
0
More than 50m up to and including 100m /day
3
0.3
3
1
More than 100m3 up to and including 2,000m3/day
More than 2,000m up to and including 10,000m /day
5
More than 10,000m3 up to and including 50,000m3/day
9.3
More than 50,000m3 up to and including 150,000m3/day
13.7
More than 150,000m3/day
22.8
Non-consumptive use
0.3
3
Lo
3
1
Partially consumptive use
Le
So
Consumptive use
1.1
Returned less than 500m from abstraction
0.2
Returned 500m to less than 1km from abstraction
0.9
Returned 1km to 5km from abstraction
1.3
Returned more than 5km from abstraction
1.9
Coastal and estuary
0.17
Inland waters
Se
1
Winter only (1 October to 31 March)
0.1
Summer only (1 April to 31 October)
0.3
All year
Pa
1
0.95
Less than 10% of 95th percentile flow abstracted
1
10% – 50% of 95th percentile flow abstracted
More than 50% of 95th percentile flow abstracted
Na
1.05
1
1–5
2
6 – 25
Fa
26 – 100
3.6
More than 100
9.4
Around £1,000, updated annually (2011 – 2012 is £1,102)
Charges in Northern Ireland
Abstraction is controlled under the Water
Abstraction and Impoundment (Licensing)
Regulations (Northern Ireland) 2009 (Fees
and Charges).
Fees and charges:
Annual charge (£) = Vol x ST x S x Co x Fin
Where: Vol = Volume (for abstractions more than 100m3 per day)
ST = Source type
S = Seasonality
Co = Consumptiveness
Fin = Financial factor
(annual standing charge)
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Table A2: Charges in Northern Ireland – components, bands and factors
Component
Band
Factor
Vol
20m3 to 99m3/day
0
100m to 499m /day
2
500m3 to 999m3/day
5
3
3
1,000m to 1,999m /day
10
2,000m3 to 9,999m3/day
15
3
More than 10,000m /day
25
Coastal and estuary
0.1
3
ST
3
Inland water (river, lough, wetland, groundwaters)
S
1
Seasonal
0.3
All year
Co
1
Non-consumptive
0.05
Consumptive
Fin
Annual charge financial factor
(subject to annual review)
Disposal of wastewater
Sewerage
In the same way as mains water, domestic
sewerage charges consist of a standing
charge and a volumetric charge (pence/m3).
However, there are two different ways of
calculating the volume attributed to this
waste stream. Unit costs are revised each
year in April and vary between sewerage
providers. For further information, contact
your service provider.
¡ Domestic wastewater only. If the only
wastewater generated at the site is
domestic, the sewerage volume will
be based on the consumption of water
supplied to the site. The sewerage charge
will appear on the water bill.
If your water is supplied by a company that
only supplies water, the bill will contain a
charge on behalf of a sewerage undertaker.
¡ Domestic wastewater and trade effluent.
If your site discharges both trade effluent
and domestic wastewater, the sewerage
charge will appear on the trade effluent
bill. If the trade effluent is metered and
the domestic wastewater is unmetered,
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£319
the volume of domestic wastewater can
be calculated by subtracting the volume
of trade effluent from the total volume of
water supplied to the site. However, this
may not be accurate if there are non-return
losses such as water in product and loss
from evaporation. In such cases, the site
will be required to provide the following
information:
-- number of employees or full-time
equivalents (A);
-- number of days worked during the
period covered by the bill (B); and
-- whether the site has a canteen providing
hot meals (C).
The domestic allowance can then be
calculated using the formula below:
A×B×C
where: C = typically 25 litres/person/day (no canteen)
= typically 40 litres/person/day (canteen)
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
Trade effluent
Water company charges for trade effluent
discharged to sewer are based on the Mogden
Formula. This formula links charges for a
particular customer to the cost of treating the
effluent (i.e. customers pay according to the
volume and strength of their effluent).
S = Charge for treatment and disposal of primary sludge (pence/m3)
Unit costs are revised each year in April and
vary between service providers. For further
information, contact your sewerage provider.
An example trade effluent bill is shown in
Figure A2.
Scotland
In Scotland, there are two charges:
Ss = Settleable solids (mg/litre), suspended solids after one hour quiescent settlement
¡¡ Operating charge (based on the Mogden
Formula):
The Mogden Formula is expressed as follows
in the UK.
Operating charge
= AVD x [Ro +Vo +Bo x (Ot/Os) + So x (St/Ss)]
England, Wales and Northern Ireland
where: Ro≡ R
C = R + M + V + Bv + B × Ot + S × St
Os
Ss
Vo≡ V
where: C = Total charge (pence/m3)
So≡ S
R = Charge for reception and conveyance (pence/m3)
Bo =Secondary treatment charging
component (pence/m³)
M = Charge for treatment and disposal where effluent goes
to a sea outfall (M for marine) (pence/m3)
AVD = Actual volume discharged (m3)
¡¡ Annual availability charge (Ca):
Ca = 365 × [CDV × (Ra + Va) + (Ba × sBODl) +
(Sa × TSSl)]
V = Charge for primary treatment
(V for volumetric) (pence/m3)
where:
Bv = Additional volume charge if biological treatment is required
(pence/m3). Also referred to as B1.
B = Biochemical oxygen demand (BOD) of settled sewage
(pence/m3). Also referred to as B2
Os = COD of crude sewage after one hour quiescent settlement (mg/litre)
St = Total suspended solids (TSS) (mg/litre) of trade effluent at pH 7
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CDV = Chargeable daily volume (m3)
Ra = Reception charge (pence/m3/day)
Ot = Chemical oxygen demand (COD) of effluent after one hour quiescent settlement at pH 7 (mg/litre)
Home
52
Va = Primary treatment charge (pence/m3/day)
Ba = Biological capacity charge (pence/kg/day)
Sa = Sludge capacity charge (pence/kg/day)
sBODl = Settled biochemical oxygen demand (BOD) load (kg/day)
TSSl = Total suspended solids
(TSS) load (kg/day)
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
Estimating trade effluent charges
Use the Mogden Formula tool on the WRAP
website to:
¡ calculate your existing effluent charges;
and
¡¡ determine how much money you could save
by reducing the volume and strength (COD
and TSS) of your effluent.
The tool contains all the necessary unit costs
for each component of the Mogden Formula
for all UK sewerage undertakers.
Discharge to surface and point source effluent
to groundwaters
England and Wales
Since April 2010, discharges to surface
waters and of point source sewage effluent to
ground/groundwater have been subject to the
Environmental Permitting Regulations.
A company in England and Wales must obtain
the consent of the Environment Agency to
discharge to controlled waters. There are
two types of charges for water discharges:
application charges and subsistence charges.
The subsistence charge depends on four
factors:
¡ volume – maximum daily volume;
¡ content of discharge;
¡ receiving water – groundwaters, coastal,
surface, estuarine; and
¡¡ financial factor – fixed multiplier (£).
¡ The volume factor (A) uses a banded
approach and relates to the maximum daily
volume (see Table A3).
¡ The contents factor (B) relates to the
provisions in the consent issued by the
Environment Agency controlling the
contents of the discharge (see Table A4).
For example, Band A includes wastewater
containing organics such as pesticides,
and aliphatic and aromatic hydrocarbons
(chlorinated and non-chlorinated).
¡ The receiving waters factor (C) consists
of four categories (see Table A5).
¡¡ The financial factor (D) is a fixed annual
fee and is subject to an annual review.
For 2011/2012, the charge is £684.
Table A3: Volume factor: England and Wales
Volume (m3)
Band
Factor
0–5
A
0.3
5–20
B
0.5
20–100
C
1
100–1,000
D
2
1,000–10,000
E
3
10,000–50,000
F
5
50,000–150,000
G
9
More than 150,000
H
14
Table A4: Contents factor: England and Wales
Band
Factor
A
14
B
5
C
3
Subsistence charge = A × B × C × D
where: A = Volume factor
(maximum daily volume)
D
2
E
1
F
0.5
B = Contents factor
G
0.3
C = Receiving waters factor
D = Financial factor
These are multiplied together to calculate the
subsistence charge.
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53
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
Table A5: Receiving waters factor: England and Wales
Type
Band
Factor
Groundwater or land
G
0.5
Coastal water
C
0.8
Surface water
S
1
Estuarine water
E
1.5
Scotland
Under the Water Environment (Controlled
Activities) (Scotland) Regulations 2011 (CAR),
a company must obtain SEPA’s consent to
discharge to controlled waters. Companies
are also subject to an annual fee for the
provision of the licence. The charging scheme
is similar to that operating in England and
Wales.
Activities are charged according to the level
of environmental risk. In turn, environmental
risk directly influences the level of
assessment, inspection and monitoring that
SEPA carries out in relation to a regulated
activity. Charges apply and, where on-going
inspection and monitoring are required,
subsistence (annual) fees may apply. These
charges replaced the Control of Pollution
Act and Groundwater charging schemes on
1 April 2006.
such as pesticides, and aliphatic and
aromatic hydrocarbons (chlorinated and
non-chlorinated).
¡¡ The receiving waters factor (R) consists of
four categories (see Table A8).
¡¡ The number of point source activities (N)
on a single site licence or associated on a
single site or on a sewer network licence.
¡¡ The financial factor (F) is a fixed annual
fee and is subject to an annual review.
For 2011 – 2012, the charge was £696.
Table A6: Volume factor: Scotland
Volume (m3)
Band
Factor
0–5
V1
0.3
5–20
V2
0.5
20–100
V3
1
100–1,000
V4
2
1,000–10,000
V5
3
10,000–50,000
V6
6
50,000–150,000
V7
12
More than 150,000
V8
24
Table A7: Contents factor: Scotland
Band
Factor
A
14
B
5
C
3
The annual charge is calculated according to
the formula: V × C × R × N × F
where: V = Volume factor
(maximum daily volume)
C = Contents factor
D
2
R = Receiving waters factor
E
1
N = Number of activities factor
F
0.5
G
0.3
F = Financial factor
¡¡ The volume factor (V) uses a banded
approach and relates to the maximum daily
volume (see Table A6).
¡¡ The contents factor (C) relates to the
provisions in the consent issued by SEPA
controlling the contents of the discharge
(see Table A7). For example, Band A
includes wastewater containing organics
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Table A8: Receiving waters factor: Scotland
Type
Factor
Groundwater or land
0.5
Coastal water
1.5
Inland water
1
Relevant territorial water
4Action plan
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1.5
Appendices
WRAP
Tracking Water Use to Cut Costs
Northern Ireland
Under the Water (Northern Ireland) Order
1999, a company must obtain the consent
of the NIEA to discharge trade or sewage
effluent to a waterway or into groundwater.
The charging scheme is similar to that
operating in the rest of the UK.
Table A10: Contents factor: Northern Ireland
Band
Factor
A
14
B
5
C
3
The annual charge is calculated according
to the formula:
V×C×F
D
2
E
1
F
0.5
where: V = Volume factor
(maximum daily volume)
G
0.3
C = Contents factor
Surface drainage
F = Financial factor
Surface drainage refers to rainwater from
roof run-off and from car park run-off that
discharges to the public surface drainage
sewer. It should not be confused with
discharge direct to surface water (covered
above). A company can be charged for surface
drainage:
¡¡ The volume factor (V) uses a banded
approach and relates to the maximum daily
volume (see Table A9).
¡ The contents factor (C) relates to the
provisions in the consent issued by the
NIEA controlling the contents of the
discharge (see Table A10). For example,
Band A includes wastewater containing
organics such as pesticides, and aliphatic
and aromatic hydrocarbons (chlorinated
and non-chlorinated).
¡¡ The financial factor (F) is a fixed annual
fee and is subject to an annual review. For
2012, this charge is £445.
Table A9: Volume factor: Northern Ireland
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55
Volume (m3)
Factor
0–5
0.3
5–20
0.5
20–100
1
100–1,000
2
1,000–10,000
3
10,000–50,000
5
50,000–150,000
9
More than 150,000
14
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3Dealing with
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sites
¡ on the basis of the rateable value of the
property;
¡ as part of the sewerage standing charge;
¡ as part of the sewerage volumetric charge;
and
¡¡ on the basis of the surface area of the site.
If your company diverts surface water drains
to foul sewer or to an effluent treatment plant
prior to discharge, then you may be being
charged twice (i.e. once as surface water and
then again as trade effluent). Consult your
service provider as you may be entitled to a
rebate.
Non-return allowance
In cases where water and wastewater do not
return to sewer, you may be entitled to a nonreturn allowance. These include the following.
¡ Domestic sewerage allowance. Most, but
not all, water companies assume that on
average up to 10% of the metered water
supplied to the consumer is not returned to
sewer. This allowance should be included
in the calculation of charges and appear on
the bill as a factor (e.g. a 10% allowance
would appear as a factor of 0.90).
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
¡ Process allowance. Where water is used
in processing and not discharged to sewer
(e.g. as water in product and losses from
evaporation), the company must provide
records or calculations to enable the
water company to calculate these losses
and adjust the sewerage or trade effluent
charge accordingly.
¡ Leaks. No allowance for leakage is given
against water supply charges. However,
an allowance may be granted against
sewerage volumetric charges if the leaked
water did not return to the public sewer.
¡ Surface drainage. A reduction in the
surface water drainage part of the
sewerage charge can be claimed if none
of the surface water from the site enters
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56
the public sewer (other than as metered
trade effluent) or is discharged directly as
surface water with the appropriate consent
from your regulator.
¡ Fire-fighting water. Where mains water
supply (metered) serves fire-fighting
equipment as well as water for normal use,
a reduction in the standing charge may be
obtained. For example, if a site is fitted with
a 100mm meter to allow for provision of
fire-fighting water, but only requires a
50mm meter for normal operating
conditions, the standing charge will be
levied at the rate for the 50mm meter
under normal operating conditions.
4Action plan
5 Further information
Appendices
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4Action plan
V+S
V+S
ü
ü
Scotland
Northern Ireland
ü
ü
ü
ü
5 Further information
Volume charge
Rateable value of property***
Various**
Various**
Surface drainage
ü
ü
ü
ü
Abstracted
ü
ü
Operating charge†
and Availability
charge
Mogden Formula
ü
ü
Mogden Formula
Mogden Formula
Trade effluent
Annual charge = V × C × F
Annual charge = V × C × R × F
Annual charge = A × B × C × D
Annual charge = A × B × C × D
Discharge to controlled water*
Annual charge = Vol × ST × S × Co × Fin
Annual charge = Va × Lo × Le × So × Se × Pa × Na x Fa
Annual charge = (V × A × B × C × SUC) + (V × B × C × D × EIUC)
Annual charge = (V × A × B × C × SUC) + (V × B × C × D × EIUC)
Wastewater
ü
ü
ü
ü
Water
Unit costs are reviewed each year and vary between service providers. For further details including unit costs, contact your service provider.
Volumetric charge + Standing charge.
Based on Mogden Formula.
Referred to as discharge consent in Northern Ireland.
Includes volume charge, standing charge and surface area of site.
A component of the sewerage charge.
V+S
ü
Wales
V+S †
*
** *** V+S
ü
Sewerage
England
Region
Volumetric charge + Standing charge
Volumetric charge + Standing charge
ü
Scotland
ü
Volumetric charge + Standing charge
ü
Wales
Northern Ireland
Volumetric charge + Standing charge
ü
Mains
England
Region
WRAP
Tracking Water Use to Cut Costs
57
Table A11: Summary of UK charging schemes as of March 2012
Appendices
WRAP
Tracking Water Use to Cut Costs
58
Appendix B: Where do businesses
use water?
All businesses are different. However, an
awareness of how other companies use water
may help you to identify where your company
uses water. Figures B1 – B12 show the typical
major uses in a number of different types of
activity.
Offices
Figure B1: Water use in offices
Cleaning
1%
Cleaning
Washing
1%
27%
Washing
Urinal
27% flushing
20%
Urinal flushing
20%
Canteen use
9%
Canteen use
9% flushing
WC
43%
WC flushing
43%
Food and drink industry
Figure B2: Water use in food manufacture
Effluent
treatment
Effluent
0.4%
treatment
0.4%
Processing/
cleaning
Processing/
55%
cleaning
55%
O ffices and kitchens
1%
O ffices and kitchens
Leaks
1% and
overflows
Leaks and
3.6%
overflows
Cooling
3.6%
towers
Cooling
24%
towers
24%
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1Why is
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Conditioning
12%
Conditioning
Product
12%
15%
Product
15%
2A six-step
procedure
Boiler house
16%
Boiler house
16%
Brewhouse
3%
Brewhouse
3%
3Dealing with
more complex
sites
4Action plan
Packaging/
cleaning Appendices
5 Further70%
Packaging/
information
cleaning
70%
towers
towers
24%
24%
WRAP
Boiler house
Boiler
house
Tracking Water
Use to
Cut Costs
16%
16%
59
Figure B3: Water use in brewing
Brewhouse
Brewhouse
3%
3%
Conditioning
Conditioning
12%
12%
Product
Product
15%
15%
Packaging/
Packaging/
cleaning
cleaning
70%
70%
Figure B4: Water use in soft drinks manufacture – carbonates or dilutables category
Equipment
Equipment
preparation 3%
preparation 3%
Other 1%
Other 1%
Floor washing 1%
Floor washing 1%
Domestic use 3%
Domestic use 3%
Rinsing of
Rinsing of
containers 4%
containers 4%
Boiler house 4%
Boiler house 4%
Pasteurisers 6%
Pasteurisers 6%
Product 78%
Product 78%
Figure B5: Water use in red meat processing
Canteen use
9%
Lairage washing 3%
Vehicle washing 5%
Floor/equipment
cleaning 33%
Knife sterilising 5%
Scald tank 7%
Cooling water 6%
WC flushing
43%
Personal hygiene
10%
Sprays and rinses
31%
Vehicle washing 1%
(cold water)
Effluent
treatment
0.4%
Processing/
cleaning
Home 55%
Feather fluming 1%
(cold water)
Personal hygiene 2%
1Why is
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important?
Scald tank 9%
(hot water)
2A six-step
procedure
Evisceration
24%
(67% hot water)
3Dealing with
more complex
sites
4Action plan
Crate and module
washing 6%
(cold water)
Appendices
5 Further information
Carcass chilling 27%
(cold water)
43%
Scald tank 7%
10%
Sprays and rinses
Personal
hygiene
Sprays
rinses
31% and
Tracking Water
10%
31% Use to Cut Costs
Cooling water 6%
WC flushing
WRAP
43%
60
Sprays and rinses
31%
Figure B6: Water use in poultry meat processing
Vehicle washing 1%
Vehicle
washing 1%
(cold water)
(cold water)
Personal hygiene 2%
Vehicle
washing
Personal
hygiene1%
2%
(cold water)
Scald tank 9%
Scald
tank 9%
(hot
water)
Personal
hygiene 2%
(hot water)
Evisceration 24%
Scald
tank 9%
Evisceration
24%
(67% hot water)
(hot
(67%water)
hot water)
Effluent
Effluent
treatment
treatment
0.4%
0.4%
Effluent
Processing/
treatment
Processing/
cleaning
0.4%
cleaning
55%
55%
Processing/
cleaning
Boiler house
55%
Boiler
16% house
16%
Feather fluming 1%
Feather
fluming 1%
(cold water)
(cold water)
Feather
fluming
1%
Crate and
module
Crate
and6%
module
(cold
water)
washing
washing
6%
(cold water)
(cold water)
Crate and module
washing chilling
6%
Carcass
27%
(cold
water)
Carcass
chilling
27%
(cold water)
(cold water)
Evisceration 24%
(67% hot water)
Carcass
chilling30%
27%
Floor washing
(cold
Floorwater)
washing
(50%
hot
water)30%
(50% hot water)
Boiler house
16%
Floor washing 30%
(50% hot water)
Figure B7: Water use in skimmed milk processing
Boiler
Boiler
10%
10%
Fridge
Boiler
Fridge
evaporative
10%
evaporative
condenser
condenser
38%
Fridge
38%
evaporative
Hygiene
condenser
Hygiene
3%
38%
3%
Brewhouse
Brewhouse
3%
3%
Brewhouse
3%
Packaging/
Packaging/
cleaning
cleaning
70%
70%
Packaging/
cleaning
70%
CIP hot
CIP
13%hot
13%
CIPCIP
hotcold 13%
CIP cold 13%
13%
Process
Process
applications
CIP cold 13%
applications
23%
23%
Process
applications
23%
Hygiene
3%
Leather and textile industries
Equipment
Equipment
preparation 3%
preparation 3%
Other 1%
Other washing
1%
Equipment
Floor
1%
Floor
washing
1%
preparation
3%
Domestic use 3%
Domestic
Other 1% use 3%
Figure B8: Water use in leather manufacture
Processing
Processing
20%
20%
Processing
20%
General
General
washing
washing
25%
25%
General
washing
25%
Floor washing 1%
Domestic use 3%
Product 78%
Product 78%
Rinsing
Rinsing
55%
55%
Rinsing
55%
Product 78%
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Tracking Water Use to Cut Costs
61
Figure B9: Water use in textile dyeing and finishing – fibre and yarn sector
Boilers
10%
Boilers
10%
Finishing
15%
Finishing
15%
Boilers
10%
Floor/equipment
cleaning 33%
Floor/equipment
Scald tank
7%
cleaning
33%
Personal
Scald tankhygiene
7%
10%
Floor/equipment
Personal hygiene
cleaning
33%
Sprays
and
rinses
10%
31%
Scald
tank
7%
Sprays and rinses
31%
Personal hygiene
Batch dyeing
75%
Batch dyeing
75%
Finishing
15%
Batch dyeing
75%
10%
Sprays and rinses
31%
Figure B10: Water use in textile dyeing and finishing – woven cloth sector
Feather fluming 1%
(cold water)
Feather fluming 1%
(cold water)
Crate and module
washing 6%
Crate
and module
(cold water)
Feather
fluming 1%
washing 6%
(cold water)
(cold water)
Carcass chilling 27%
(cold
Cratewater)
and module
Carcass
27%
washingchilling
6%
(cold
(coldwater)
water)
Floor washing 30%
(50% hot water)
Floor washing
Carcass
chilling30%
27%
(50% water)
hot water)
(cold
Floor washing 30%
(50% hot water)
Boilers
10%
Boilers
10%
Finishing
13%
Finishing
13%
Boilers
Preparation
10%
27%
Preparation
Finishing
27%
13%
Vacuum systems 1%
Chemical industry
Housekeeping
3%1%
Vacuum systems
Product washing 3%
FigureHousekeeping
B11: Water use
in speciality chemicals manufacturing
3%
Domesticwashing
uses 3%3%
Product
Vacuum
Plant
andsystems
vessel3%1%
Domestic
uses
washing
4%
Housekeeping
3%
Plant and vessel
Product 4%
washing 3%
washing
Raw material
Domestic uses 3%
21%
Raw
material
Plant
and vessel
21%
washing 4%
CIP cold 13%
Process
CIP hot
applications
13%
Process
23%
applications
23%CIP cold 13%
Raw material
21%
Process
applications
23%
Rinsing
55%
Batch dyeing
50%
Preparation
27%
CIP hot
13%
CIP hot
13%
CIP cold 13%
Home
Batch dyeing
50%
Batch dyeing
50%
Other 3%
1Why is
saving water
important?
Hoses 4%
Other 3%
Chemical carrying
Hoses
4%
water 4%
Chemical carrying
Pulper4%
water
Other 3%5%
showers
Pulper
Hoses 4%
Sheet
showers 5%
Chemical 5%
carrying
knock-off
Sheet
water 4%
Box
lubrication
2
A six-step
3Dealing with
knock-off
5%
showers
8%
Pulper
procedure
more complex
Box
lubrication
showers
5%
sites
showers 8%
Cooling 27%
Cooling 27%
Effluent
dilution 6%
Effluent
dilution 6%
pollution
CoolingAir
27%
control 7%
Air pollution
Effluent
control 7%
dilution
Steam6%
production
Steam
25%
Air pollution
production
control 7%
25%
Steam
production
25%
Felt cleaning 2%
Sc reen rejects dilution 2%
Felt cleaning 2%
Refiner sealing water 2%
Sc reen rejects dilution 2%
Refiner sealing water 2%
Vacuum pump
Felt cleaning 2%
29%
Sc reen rejects
dilution
2%
Vacuum
pump
29% water 2%
Refiner sealing
Disc thickener
Appendices
10%
4Action plan
5 Furthershowers
Disc
thickener
information
Vacuum
showerspump
10%
29%
Plant and vessel
washing 4%
CIP hot
13% WRAP
Air pollution
Tracking Water Use
to Cut7%
Costs
control
Raw material
21%
CIP cold 13%
62
Steam
production
25%
Process
applications
23%
Paper and board industry
Figure B12: Water use in paper and board processing
Other 3%
Felt cleaning 2%
Sc reen rejects dilution 2%
Refiner sealing water 2%
Hoses 4%
Chemical carrying
water 4%
Pulper
showers 5%
Vacuum pump
29%
Sheet
knock-off 5%
Disc thickener
showers 10%
Box lubrication
showers 8%
Rinsing
55%
Pump gland
sealing water
10%
Wire showers 16%
Even for companies in the same line of
business, water use varies from company to
company. The factors that affect the amount
of water used by a company include:
¡
¡
¡
¡
¡
¡¡
raw materials used;
number of different products made;
technologies employed;
throughput;
number of staff; and
staff facilities on site.
Typical water uses are listed in Table B1.
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
When considering your water balance, you
may find it useful to consider your water use
in three categories:
¡ general use – this may include on-site
washroom facilities and a canteen.
Substantial savings can be obtained by
detecting and fixing leaks, faulty control
valves, leaking cisterns, etc. You may wish
to include some process-related issues
(e.g. leaks and overflows from pipes/
storage tanks) in this category;
¡ process use – this includes cooling towers,
liquid ring vacuum pumps, heat exchanger
circuits, etc. Substantial savings can be
achieved, but these are generally site
specific; and
¡ cleaning and washdown – this covers
mainly process-related activities, but
may also include cleaning offices and
washrooms. Cleaning often provides major
opportunities for cost savings. In particular,
watch out for extravagant use of hoses – you
could save thousands of pounds per year.
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
63
Table B1: Typical water uses at industrial and commercial sites
Type
Description
Examples
General
Sanitary
Toilet flushing
Sinks
Showers
Domestic
Heating/air-conditioning
Laundry
Drinking
Cooking
Washing up
Recreation
Swimming
Jacuzzi
Ice rink
Gardens
Watering plants/lawns
Fountains
Garage
Vehicle washing
Vehicle maintenance
Industrial
Heating/cooling/sealing
Rotating machinery and process materials
Heat exchange
Condensing vapours
Processing
Dilution/mixing
Heating/cooling
Separation
Product use
Cleaning and washing
Tanks
Vessels
Floors
Pipework
Pumps
Steam raising
Process use
Heating
Trace lagging
Commercial
Treating spills/leaks/drips
Abnormal events where water is used to
dilute and disperse
Cleaning and washing
Canteens
Laundries
Laboratories
Condensers
Vacuum pumps
Special
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
Hospital therapy pools
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
64
Appendix C: Unit operations
for a boiler and cooling tower
Figure C1 and Figure C2 show the water flows
for two common operations.
Figure C1: Boiler house operations
Inputs
Mains water
Outputs
Recirculation
1 6 4 02
Water meter
Steam and
hot water
Ion
exchange
column
Regeneration
chemicals
Condensate
recovery
Sub-meter
Make-up
water
Regeneration
wastewater
to sewer
Boiler
Pump
Hot well
Blowdown
to sewer
Figure C2: Cooling tower operations
Inputs
Evaporation,
spray and mist
to atmosphe re
Mains water
Outputs
Recirculation
Inputs
Outputs
Recirculation
1 6 4 02
Water meter
Cooling tower
Pump
Cold well
Blowdown
to sewer
Blowdown
to sewer
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
Leaks and
overflows
4Action plan
Process
cooling
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
65
Appendix D: Example water balances
Example industrial site
Figure D1 shows the water inputs and outputs
for an example industrial site, which has the
water balance shown in Figure D2. Note the
need to consider recirculated water.
Figure D1: Water inputs and outputs for an example industrial site
Water supply
Cooling tower
1 6 4 02
Steam and
evaporation
– drying processes
Water
meter
1 6 4 02
Cleaning
chemicals,
raw materials
Hot
water
Cold
water
Industrial/manufacturing processes and utilities
(including laboratory operations, toilets/wash
block/canteen)
Water in
products
1 6 4 02
Treatment
chemicals
Water leaks
into ground
including
fire-fighting
water*
1 6 4 02
Water in liquid wastes,
including sludge
Effluent
treatment
plant
Surface water
discharges including
via oil interceptors
Sludge
storage
Treated
effluent
Discharges to sewer
including fire-fighting water*
and domestic sewage
Inputs
Surface water
Outputs
*Potentially contaminated fire-fighting water should be collected separately.
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
66
Figure D2: Water balance for an example industrial site
Water supply
1 6 4 02
1 6 4 02
Water
meter
Water
meter
Water supply
Water
meter
Water
meter
1 6 4 02
1 6 4 02
1 6 4 02
20m3/day
535m3/day
2m /day
liquid
Industrial/manufacturing
process 537m3/day
3
raw
535m3/day
/day
2m
materials
liquid
Industrial/manufacturing process 537m3/day
raw
materials
5m3/day
1m3/day
leaks
to atmosphere
5m3/day 1 6 4 0 2
1m3/day
leaks
489m3/day
to atmosphere
1 6 4 02
495m3/day
n liquid wastes,
cluding sludge
n liquid wastes,
cluding sludge
1 6 4 02
Cooling 495m3/day
tower
Cooling
495m3/day
tower
20m3/day
Water in
products
Water in
products
555m3/day
1 6 4 02
3
1 6 4 02
555m3/day
1 6 4 02
1 6 4 02
19m3/day 495m3/day 38m3/day
blowdown
to foul
3
3
to sewer
sewer
/day
38m
/day
19m
blowdown
to foul
Inputs
Outputs
to
sewer
sewer
Inputs
Outputs
3m3/day
steam and
evaporation
3m3/day
steam and
evaporation
3
Effluent489m /day
treatment
Sludges
plant
Effluent
treatment
Sludges
plant
484m3/day
to sewer
3
or river
484m
/day
to sewer
Recirculation
or river
2m3/day
in products
2m3/day
in products
5m3/day
sludge
tankered
5m3/day
off
site
sludge
tankered
off site
Recirculation
Example hotel
Figure D3 shows the water inputs and outputs
for an example hotel, which has the water
balance shown in Figure D4.
Figure D3: Water inputs and outputs for an example hotel
Water supply
Water supply
1 6 4 02
Water
meter
Evaporation
and steam
Evaporation
and steam
Home
1Why is
saving water
important?
Treatment
chemicals
Treatment
chemicals
Water
1 6 4 02
meter
Hotel
Hotel
Detergents
Detergents
Laundry
Kitchen
Laundry
Kitchen
Inputs
Outputs
Inputs
Outputs
2A six-step
procedure
3Dealing with
more complex
sites
Domestic wastewater
to foul sewer
Domestic wastewater
to foul sewer
4Action plan
Wash blocks
and
bathrooms
Wash
blocks
and
bathrooms
Steam
Steam
Boiler/air-conditioning/
heating/cooling tower
Boiler/air-conditioning/
heating/cooling tower
Blowdown and
condensate to
foul sewer
Blowdown
and
condensate to
foul sewer
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
67
Figure D4: Water balance for an example hotel
Water supply
Water
meter
3m3/day
steam and
evaporation
/day
2m3/day
0.005m3/day
evaporation
and steam
2m3/day
in products
9m3/day
1m3/day
5m3/day
0.005m3/day
liquid
raw materials
Laundry
Washing
machine
5m3/day
sludge
tankered
off site
1m3/day
0.05m3/day
treatment
chemicals
Kitchen
Dishwasher
Sink
2m3/day
dges
1 6 4 02
Hotel bathrooms
Toilets
Showers
and baths
1m3/day
0.05m3/day
steam
Boiler/
air-conditioning
system
5m3/day
1m3/day
blowdown/
condensate
Inputs
Outputs
9m3/day
domestic wastewater
Constructing a water balance for
a medium-sized hotel
Mains water
The water and sewerage
charges at one of the
hotels in a chain had jumped from £8,496/year
to £38,969/year
in consecutive years.3
Water
Treatment
chemicals
Steam
h blocks
and
hrooms
Boiler/air-conditioning/
heating/cooling tower
In the year with the particularly high water
and sewerage charges, the
hotel had a 60%
Known
occupancy rate. The gardens were only
Estimated
watered on two afternoons
in July using a
Calculated
hose fed off the mains supplying
the bar and
1 6 4 02
21,650m /year
toilets.
Because
some
laundry
is
charged to
meter
clients, a record is kept of machine use. The
The hotel has 30 bedrooms, with a restaurant
1,554m3/year
Restaurant/bar
larger (23kg wash) was used 231 times during
and bar (open to non-residents). Ten of the
Dishwasher
the
year and the other (5.5kg wash) was used
rooms are in a separate new wing. All of the
Toilets
450 times. Machine specifications show that
bedrooms are equipped with a bath, shower
the larger machine uses 112 litres/fill and
and WC. Other facilities include a swimming
each wash cycle takes five fills. The smaller
4m3/year
pool and leisure facilities. The hotel
also has
Gardens
machine takes 60 litres/fill and seven fills.
its own kitchens equipped with two large
Hoses
The sub-meters on the kitchens show that
dishwashers and separate laundry facilities
3
with two washing machines. Outside there are 248m of water was used during the year.
extensive gardens.
298m3/year
Old
20-bedroom
The
first stepcomplex
is to draw a block
Showers/baths of the hotel and fill in available
representation
The hotel is supplied with water only from
Toilets and sinks
data for the year. The first values to be
the mains. In addition toSub-meter
the water company’s
entered are those from the sub-meters:
meter, there are sub-meters on the old
bedroom complex (fed by an independent
149m3/year
New 10-bedroom wing
¡Showers/baths
298m3 for the old bedroom complex;
pipeline off the incoming water main), on
and3sinks
¡Toilets
2,241m
the kitchens and on the pipeline serving the
for the flow to the swimming pool,
swimming pool, leisure facilities and new
leisure complex and new bedroom wing; and
bedroom complex.
¡¡ 248m3 for the kitchens.
2,241m3/year
Swimming pool
Make-up water
Sub-meter
Blowdown and
condensate to
foul sewer
Home
1Why is
saving water
important?
Leisure facilities
Showers/baths
Toilets and sinks
2A six-step
procedure
3Dealing with
more complex
248m3/year
sites
4Action plan
Kitchens
Dishwashers
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
The next step is to do some calculations to
determine other flows.
¡ In the garden, one hose was used for two
afternoons in July – say for four hours.
A garden hose uses 8.3 litres/minute as
a minimum. The water use is estimated
at 4.0m3/year (see equation D).
¡ At a cost of around £1.80/m3 (water and
sewerage combined), the year’s bill of
£38,969 gives a water input from the mains
supply of 21,649m3/year.
¡¡ In the laundry, the large machine used
129m3/year (see equation A) and the small
machine used 189m3/year (see equation B).
This gives a total of 318m3/year.
Equation D = (2 hoses × 8.3 litres/minute ×
60 minutes/hour × 4 hours)/1,000
Equation A =
(231 uses × 112 litres/fill × 5 fills/use)/1,000
Equation B =
(450 uses × 60 litres/fill × 7 fills/use)/1,000
¡¡ The average water consumption of an
occupied bedroom is approximately
68 litres/day. A cross-check shows that the
metered water use for the old bedroom
complex agrees with the value calculated
from the occupancy rate and assumed
average water use (i.e. 298m3/year) (see
equation C). Assuming the two sets of
bedrooms use water at the same rate, then
water use for the ten-bedroom wing is
149m3/year.
Equation C = (20 bedrooms × 68 litres/day ×
365 days/year × 0.6 occupancy rate)/1,000
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
68
¡¡ No data exist for the restaurant and bar.
It is estimated at two sinks with a
maximum of two taps each with one
tap running for 6 hours/day for 5 days/
week. Assuming that the taps run at the
same rate as the hose, a reasonable
‘guessestimate’ is 1,554m3/year
(see equation E).
Equation E = (2 taps × 8.3 litres/minute ×
60 minutes/hour × 6 hours/day ×
5 days/week × 52 weeks/year)/1,000
Figure D5 shows the water balance for the
hotel. The total water consumption by the
various areas of the hotel therefore equals
4,663m3/year (1,554 + 298 + 2,241 + 248 + 318
+ 4). This compares favourably with the value
for total water use of 4,720m3/year calculated
from the first year’s bill. Managers have thus
proved that water use had been excessive in
the second year.
4Action plan
5 Further information
Appendices
2m3/day
WRAP
dges
1m3/day
5m3/day
1m3/day
Tracking Water Use toblowdown/
Cut Costs
condensate
5m3/day
sludge
tankered
off site
69
Inputs
Outputs
9m3/day
domestic wastewater
Figure D5: Water balance for the hotel
Known
Mains water
Water
meter
Estimated
Calculated
1 6 4 02
21,650m3/year
1,554m3/year
Treatment
chemicals
Restaurant/bar
Dishwasher
Toilets
4m3/year
Gardens
Hoses
Steam
h blocks
and
hrooms
298m3/year
Old 20-bedroom complex
Showers/baths
Toilets and sinks
Sub-meter
149m3/year
Boiler/air-conditioning/
heating/cooling tower
New 10-bedroom wing
Showers/baths
Toilets and sinks
2,241m3/year
Swimming pool
Make-up water
Sub-meter
Blowdown and
condensate to
foul sewer
Leisure facilities
Showers/baths
Toilets and sinks
248m3/year
Kitchens
Dishwashers
Food preparation
Sub-meter
318m3/year
Laundry
Washing machines
Steps that the hotel could take to investigate
its water use include:
¡ checking the accuracy of the incoming
water meter;
¡ turning off all water-using devices and then
observing the meters and checking the
drains for any flow (but not the drains that
also receive rainwater);
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
¡ fitting more sub-meters to obtain more
accurate data;
¡ looking for leaks;
¡ examining water use in the swimming pool
and leisure facilities; and
¡ checking comparative occupancy rates
between the new and old bedroom
complexes.
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
70
Appendix E: Producing and using site
drainage plans
Producing site drainage plans
¡ Locate all drainage manholes and draw a
sketch plan of their approximate location.
¡ Identify the type of each drain, for example:
-- foul (domestic) sewer (F);
-- effluent (E);
-- surface water (S); and
-- combined.
¡ Record this information on your plan. Mark
(F, E, S) or colour-code the manholes for
future reference.
¡ Identify the direction of flow. If there is no
flow, pour in some water and see which
way it drains. If there is a flow, add a tracer
dye or an object that will float and observe
its flow. Be careful not to contaminate
the effluent, risk pollution, break consent
conditions or block the drains.
¡¡ Identify connections to other manholes
(using added water or tracer dye) and draw
on the plan.
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
Using drainage plans to identify effluent
sources
Obtain drainage plans for the different
drainage systems. For each drainage system:
¡ lift the manholes and draw all pipes or
channels connecting to the manhole on the
plan. Note the number, size and direction
of pipes (even if no flow is observed) and
number them;
¡ trace the pipes or channels back to
above-ground connections. These are
called drain entry points. Look for trench
scars on the floor or, if necessary, use
water/tracer dyes;
¡ at each entry point, note the pipes or
channels feeding into it from process
equipment and number them on the plan;
and
¡ identify the process plant/equipment
feeding each pipe/channel (i.e. the sources
of effluent).
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
71
Appendix F: Calculating water flows for
cooling towers and steam relief valves
Calculating cooling tower water consumption
The following simplified approach gives
an estimate of the water used by a cooling
tower (see Figure F1). The variations and
inaccuracies in water use can be large,
particularly between summer/winter and
day/night.
To calculate water use by a cooling tower (i.e.
volume of make-up water required), you need
to know:
¡ Tout (i.e. the temperature of process water
leaving the cooling tower in °C);
¡ Tin (i.e. the temperature of process water
entering the cooling tower in °C);
¡ airflow (i.e. the flow rate of air into the
cooling tower). If this is not known, assume
it is equal to the flow of cool water to the
process; and
¡¡ Tair (i.e. the temperature of air entering the
cooling tower in °C).
Then follow the steps in Table F1 to calculate
water use by the cooling tower. The units for
the flow and the airflow should be
litres/second and kg/second respectively.
¡ flow (i.e. the flow rate of cool water to
the process). This is obtained from a flow
meter or pump hours-run meter;
Figure F1: Cooling tower schematic
Evaporation
T in
T air
Airflow
Cooling
tower
Process
Make-up water
T out
Flow
Blowdown
V
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
Steam vent stack
D
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
72
Table F1: Calculation of water consumption by a cooling tower
Step
Calculation
Symbol
Units
Formula
1
Thermal load
A
kW
A = Flow × 4.2kJ/kg°C × (Tin - Tout)
Evaporation
where 4.2kJ/kg°C is the specific
heat of water.
2
Cooling load due to airflow
B
B = Airflow × 1kJ/kg°C × [(Tair - (Tin - 3))]
kW
T
air
where 1kJ/kg°C is the specific
Airflow
heat of air.
NB B could be negative.
3
Evaporative load
C
kW
4
Evaporation
D
kg/second
Cooling
tower
C=A+B
C water
D=
Make-up
2,430kJ/kg
where 2,430kJ/kg is the latent heat of evaporation of
water at 30°C.
5
Make-up volume
Vs
litres/
second
Vs = D ×
( 1 + ( N 1– 1 ))
where N = number of concentrations* in the tower.
Blowdown
Typical N values are:
1.5
2
3
6
very hard water
hard water
soft water
deionised water
* Relates to the extent to which solids are concentrated in the cooling tower cold well.
Calculating water release from
a steam vent
The following simplified approach gives an
estimate of the water lost from a steam vent
(see Figure F2).
Figure F2: Steam vent stack schematic
V
To calculate the volume of water lost from the
steam vent you need to know:
¡ the diameter of the stack (D) in metres; and
¡¡ the velocity of steam exiting the vent (V)
in metres/second. If this is not known,
assume a value of 3 metres/second.
D
Steam vent stack
Then follow the steps in Table F2 to calculate
the water loss from the vent.
Table F2: Calculation of water loss from a steam vent
Home
Step
Calculation
Symbol
Units
Formula
1
Surface area of the stack
A
m2
2
A = 3.14 x D
4
2
Volumetric release rate
R
m3/second
R=A×V
3
Water loss
V
m3/second
V = R × 0.6
where 0.6kg/m3 is the density of water vapour at 100°C
and 1 atmosphere pressure.
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
73
Appendix G: Determining pollutant loads
The pollutant load and concentration of a
pollutant in an effluent can be calculated
using the following formulae (remember 1m3
= 1,000 litres and 1kg = 1,000,000mg):
Load (mg/day)
=
Concentration (mg/litre) × Flow volume (m3/day) × 1,000
Load (kg/day)
=
Concentration (mg/litre) × Flow volume (m3/day) × 1,000
=
1,000,000
Concentration (mg/litre) × Flow volume (m3/day)
1,000
Concentration
=
(mg/litre)
Load (kg/day) × 1,000,000
Flow (m3/day) × 1,000
=
Load (kg/day) × 1,000
Flow (m3/day)
Example calculations
Rows 1 and 2 of Table G1 show an example
calculation of the load in kg/day of total
dissolved solids (TDS) in a cleaning effluent
and a boiler blowdown. The flow volume and
concentration of the dissolved solids have
been either measured or estimated.
Row 3 of Table G1 shows the calculation of the
concentration of a combined flow made up of
the two individual flows – the cleaning effluent
and boiler blowdown in rows 1 and 2. The total
volume was determined by adding together
the volumes for the individual flows, and the
total load by adding together the loads for the
individual flows. The concentration was then
calculated using the formula given above.
Table G1: Example calculation of pollutant concentration and load
Home
Row
Effluent
Contaminant
1
Cleaning effluent
2
3
1Why is
saving water
important?
Flow volume
(m3/day)
Concentration
(mg/litre)
Load
(kg/day)
TDS
5
500
2.5
Boiler blowdown
TDS
20
2,500
50
Combined flow
TDS
25
2,100
52.5
2A six-step
procedure
3Dealing with
more complex
sites
4Action plan
5 Further information
Appendices
WRAP
Tracking Water Use to Cut Costs
74
We hope that you have found this guide helpful on your route to greater resource efficiency. Don’t forget that WRAP
is here to help you to improve resource efficiency. Visit the website at www.wrap.org.uk or contact the WRAP
Resource Efficiency Helpline on 0808 100 2040.
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Waste & Resources
Action Programme
The Old Academy
21 Horse Fair
Banbury, Oxon
OX16 0AH
Tel: 01295 819 900
Fax: 01295 819 911
Email: [email protected]
Resource Efficiency Helpline:
0808 100 2040
www.wrap.org.uk/brehub
March 2013
Home
1Why is
saving water
important?
2A six-step
procedure
3Dealing with
more complex
sites
4Action plan
5 Further information
Appendices