Case study:
Membrane technology allows
water recovery and savings
at beetroot processing site
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Adapted from Envirowise Publication CS855, published 2009
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Background
This Case Study at G’s Fresh Beetroot demonstrates the cost savings and environmental
benefits that can be achieved when implementing environmental initiatives to reduce
water use and effluent strength. It also demonstrates the added cost benefit through
Enhanced Capital Allowance available from the Water Technology List.
The company has used membrane technology to successfully treat its effluent, producing
a water of sufficient quality for re-use on site. The benefits to G’s of taking action to
minimise water use and waste include:
■ Total cost savings of £152,000/year
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■ Annual water consumption reduced by 22,400 m
■ Water-related cost savings of £16,000/year
■ Effluent-related cost savings of £126,000/year
About G’s Fresh Beetroot
G’s Fresh Beetroot is part of the G’s Marketing group, a family business that was
founded in 1952 by Guy Shropshire, the current President, and is now run by his eldest
son, John Shropshire.
G’s supplies many UK food businesses including a number of the leading quality
supermarkets for whom G’s supplies a range of own-label salads and vegetables. For
more than 40 years G’s has also supplied the independent retail, food service & catering,
and food manufacturing sectors under the G’s trademark.
G’s Fresh Beetroot employs some 120 staff at its
3.5-acre site in March, Cambridgeshire, and
produces around 12,000 tonnes of beetroot a
year.
The site opened in 2001 and currently produces
around 12,000 tonnes of beetroot a year. The
company supplies a number of the leading quality
supermarkets as well as independent retail, food
service & catering, and food manufacturing
sectors.
With the cost of effluent disposal increasing every year, the site sought advice from its
water provider and discussed ways to reduce effluent volume and load, allowing G’s to
ensure compliance and reduce disposal costs.
Review of effluent costs and treatment
Prior to 2007, G’s treated its effluent using an aerobic digester. By July 2005 the site’s
effluent costs, based on the Mogden formula, had risen to around £5.40/m 3 with annual
costs of around £141,750. With the site’s processing capacity expected to increase along
with the annual increase in trade effluent charges, G’s estimated that effluent costs
would be over £160,000 the following year.
Initial investigations found that the clarifier was providing poor retention and therefore
inadequate solids removal. A cone was inserted into the clarifier to create a vortex,
providing better retention.
Furthermore, after discussing the options with the site’s mains water provider, Anglian
Water, G’s decided to look at using membrane technology to further improve effluent
treatment and reduce costs. G’s teamed up with Aquabio to trial a membrane filtration
system that was designed to treat all effluent generated on site (typically 80-90 m3/day),
allowing up to 70% recovery for re-use.
The benefits of membrane technology
When used for wastewater treatment, membrane filtration processes offer a high level of
purification, allowing the wastewater to be recovered and re-used. Moreover, the
technology offers a low footprint and has relatively low energy consumption.
Initially G’s undertook a three-month pilot study to ensure that the effluent could be
adequately treated using the proposed membrane technology. The pilot effluent
treatment plant consisted of a membrane bioreactor (MBR) comprising an aerobic
bioreactor and ultrafiltration (UF) followed by reverse osmosis (RO).
Fig 1 shows the effluent at different stages of treatment. The coarse solids are removed
from the effluent before it is pumped into the bioreactor (A) where the majority of the
chemical oxygen demand (COD) is removed. The effluent is then treated by ultrafiltration
to remove the biomass (B). The UF treated effluent (UF permeate) is then polished by
reverse osmosis, removing the residual colour (C).
Overall this treatment removes >99% COD and
suspended solids loads.
The pilot proved successful in recovering 70% water
(permeate) for re-use, with the remaining 30% (retentate)
being discharged to drain. In addition, the quality of the
recovered water was such that it can be used for boiler
make-up without pretreatment. Previously the boiler
make-up comprised mains water that had to be softened
prior to use.
Fig 1 Effluent at different
stages of treatment
Since the success of the pilot, the site has commissioned a full-scale MBR achieving the
following high performance:
Table 1 MBR performance
COMPONENT
Bioreactor feed
UF permeate
COD
AVERAGE
UNITS
8,117
732
mg/l
kg/day
64
5.8
mg/l
kg/day
Every day samples are analysed on-site for a number of parameters including COD.
Data are entered into the monitoring spreadsheet to track performance and ensure
quality standards are met.
Enhanced Capital Allowance (ECA)
The Enhanced Capital Allowance (ECA) scheme enables businesses to claim 100% firstyear capital allowances in investment in ‘efficient membrane filtration systems for the
treatment of wastewater for recovery and re-use’.
G’s has become the first company to gain ECA approval for tax relief, worth more than
£100,000, for the capital costs of an efficient membrane filtration system.
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The company was awarded a ‘Certificate of Environmental Benefit’ from Defra that
demonstrates that the installation is water efficient and allows G’s to claim ECAs on the
costs of the investment. ECA for the G’s membrane bioreactor has shortened the
payback period of the project by 12 months, which gave senior management the
confidence to invest.
Further information and advice on ECA can be found at www.eca-water.gov.uk
Cost savings
Installing and running the MBR is a high cost. However, with savings of around
£152,000/year, the initiative has a payback period of 2.6 years, taking into account the
benefits realised with ECA (see Table 2). Given that the site’s processing capacity is
expected to increase, the effluent load will almost certainly increase and as such savings
are likely to exceed those reported in Table 2.
Table 2 Summary of costs and savings
ITEM
Water
Effluent
Solid waste (screenings)
Sludge disposal
Other running costs
Capital investment
Total
With ECA benefit
SAVINGS
(£/YEAR)
£16,000
£126,000
£10,000
-
COSTS
PAYBACK
(£/YEAR) PERIOD
£52,650
£500,000
£152,000
£552,650 3.6 years
2.6 years
Environmental benefits
The use of the MBR has resulted in the following environmental benefits:
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■ A reduction in mains water use of 70% (22,400 m /year).
■ Reduced effluent strength by 726 kg/day COD and 138 kg/day suspended solids.
■ Ensured compliance with the trade effluent consent.
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Fig 2 Schematic of membrane bioreactor (MBR)
“ECA eligibility has really made the difference. It has provided us with a
major incentive to invest. Not only will we be able to significantly
reduce our water and effluent costs, but the ECA has also shortened
the payback period of the project by 12 months, giving the board the
confidence to invest.”
Graham Forber, Managing Director, G’s Fresh Beetroot
www.wrap.org.uk/rippleffect
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