FINAL REPORT- WATER PURIFICATION - 2011
DEVIKULAM
The University of Queensland
EWB Challenge 2011
Team Slate
Reflection
The overarching aim of this project was to provide the community of Devikulam, India, with
a reliable supply of uncontaminated drinking water. This was to be achieved through an
engineering solution developed to accommodate the issues that would arise for its function
within this community.
The largest obstacle encountered during this project was in the design development phase
where suitable methods of removing turbidity, bacteria and predominantly, salinity, were
required to be developed. Increasing the challenge was the initial project aims set down to
guide the efficacy of the design to achieve the desired results while maintaining a positive
relationship between the social, economic and environmental aspects pertaining to the
community where the water purification device was to be implemented.
Working as an effective team overall increased the team’s ability to research more methods
to purify water initially which gave the team more options when it came to ultimately
deciding on a specific method to achieve the prescribed project aims. Furthermore, in this
team, the individual strengths of each team member varied which increased overall team
synergy as each member had their own responsibility for individual parts of the project and
report. By breaking the work up into manageable parts and delegating each to a team
member, who had confidence that they could complete the task best, augmented the
overall success of the team to produce a comprehensive report and an effective prototype.
On reflection, if this project was to be done again there would be greater time put into
researching alternative materials that could be used in the installation to provide greater
flexibility when certain materials are not available or able to be obtained. Additionally, it
would prove beneficial if one of the project aims was stated more clearly to specify making
the design a long term option in respect to the working life of all components.
The most enjoyable part of the Challenge was how it provided an appropriate introduction
to the concept of professional engineering to the students by letting us experience firsthand
how to develop project aims and design requirements, create effective designs, decide on
the most appropriate design and deal with the issues surrounding the construction of the
chosen design. By providing a real life context, it gave the Challenge a different dimension
wherein the solutions provided could actually be gauge more specifically as to their impact
which is good for feedback for us.
FINAL REPORT- WATER PURIFICATION DEVIKULAM
2011
2nd June 2011
Dr. Stefano Freguia
Advanced Water Management Centre
The University of Queensland
St. Lucia, Queensland
4067
Dear Dr. Freguia,
Attached is our proposal for the ‘Engineers Without Borders’ project addressing suitable
solutions for access to safe drinking water in Devikulam, India.
This bid assumes that if it is granted, all parties will work together to develop a mutually
agreeable construction schedule. This bid is also based on information provided at this time.
Any revisions required at a later date will be subject to price review at that time.
For further information, please contact any member of the team:
Mitch Smith – 0466 348 606
Danielle Hester – 0415 776 297
Matt Beeston – 0418 122 816
Josh Pellicaan – 0404 741 235
Lawrence Yang – 0425 418 532
Thank you for giving us this opportunity. We look forward to hearing from you.
Yours Sincerely,
Mitch Smith
Danielle Hester
Matt Beeston
Josh Pellicaan
Lawrence Yang
Slate Engineering Clean water for a brighter
future
FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
Leading The Way Forward
UQ Engineering
ENGG1000: P1 – Water Purification
nd
2 of June 2011
Mitch Smith: 42676852
Danielle Hester: 42676889
Matt Beeston: 42671642
Josh Pellicaan: 42443960
Lawrence Yang: 42182223
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FINAL REPORT- WATER PURIFICATION DEVIKULAM
2011
Executive Summary
Pitchandikulam Forest Organisation identified the inadequacy of access to safe drinking
water in the village of Devikulam and has initiated an engineering project, in conjunction
with Engineers Without Borders, to address the situation. Tests conducted in April 2010 on
the Devikulam water supply indicated that salinity, bacteria and turbidity were the main
regions of concern. The main goal is to design a water treatment system which renders the
water drinkable by international drinking water standards and able to be used for everyday
needs. Associated design goals for the project include:
•
•
•
•
•
Building the most cost-effective modular water treatment device;
Ensuring it is environmental sustainable;
Making it socially and culturally acceptable;
Having capacity to supply 10 people with their daily requirements and;
Non-reliant on reticulated power.
Three water treatment processes were selected as having the greatest potential to fit the
requirements and considerations determined by the context. These three methods were:
•
•
•
Filtration and adsorption;
Biogas distillation and;
Solar distillation.
A conclusion was drawn to use an innovative solar distillation device consisting of a first
stage water filter and then a parabolic trough, with the option to use a biogas system if
required. This was the most appropriate method due to the fact it fulfilled the water
purification requirements of removing salinity, turbidity and bacteria. The filter’s main
directive is to remove nearly 100% of turbidity and bacteria from the feed water.
Subsequently, the distillation device will remove salinity and remaining turbidity and
bacteria.
Preliminary feasibility calculations determined that one person would require 20L of clean
water per day for drinking, general hygiene needs and cooking, and thus, a household of ten
would require 200L of clean water per day. Calculations conducted on a water treatment
system concluded that this method can supply the amount of purified water demanded.
It is recommended that a water filter is utilised, as well as a solar distillation device
composing of a trough like design (which still relies on the fundamentals of a conventional
solar still) be installed to meet the demands of Devikulam for purified water. A mirror of
4000mm and radius of 500mm (with angle of curvature at 180°) was the calculated
dimensions for the parabolic mirror trough (assumed sun energy constant) , and for the
filter system, an adapted PVC pipe of dimensions 550mm by 250mm. The expectation is that
subsequent to the water passing through the full system, the water quality will be of that
which satisfies international drinking water standards.
FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
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FINAL REPORT- WATER PURIFICATION DEVIKULAM
2011
Contents
Executive Summary .......................................................................................................... 3
1.0
Introduction ........................................................................................................... 1
1.1
Project Overview ......................................................................................................... 1
1.2
Project Aims and Report Contents .............................................................................. 1
2.0
Problem Definition ................................................................................................. 2
2.0
Task Identification ....................................................................................................... 2
2.1
Pre-existing Water Supply ........................................................................................... 2
2.2
Project Goals Identification ......................................................................................... 2
3.0
Project Scope ......................................................................................................... 3
3.0
Project Scope............................................................................................................... 3
3.1
Inclusions and Exclusions ............................................................................................ 3
3.2
Design Assumptions .................................................................................................... 3
4.0
Literature Search .................................................................................................... 4
4.0
Water Purification ....................................................................................................... 4
4.1
Existing Purification Techniques ................................................................................. 4
4.2
Filtration ...................................................................................................................... 4
4.3
Solar Distillation .......................................................................................................... 5
4.4
Biogas .......................................................................................................................... 5
4.5
Sanitation .................................................................................................................... 6
4.6
Parabolic Reflection .................................................................................................... 7
5.0
Initial Design Concepts ........................................................................................... 8
6.0
Technical understanding ........................................................................................ 9
6.0
Sand Filtration ............................................................................................................. 9
6.1
Ceramic Filter Candle .................................................................................................. 9
6.2
Solar Distillation – Cylindrical Pipe .............................................................................. 9
6.2.1
Parabolic Reflection ................................................................................................. 9
6.2.2
Biogas ..................................................................................................................... 10
7.0
Engineering Sketches............................................................................................ 10
7.1
The Filter System ....................................................................................................... 11
7.2
The Solar Still ............................................................................................................. 12
7.3
Flow Diagram............................................................................................................. 13
8.0
Sustainability ....................................................................................................... 14
FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
8.1
Triple Bottom Line Assessment ................................................................................. 14
8.2
Environmental Sustainability .................................................................................... 15
8.3
Life Cycle Assessment ............................................................................................... 15
8.3.1
Water Filter System ............................................................................................... 15
8.3.2
Solar Still ................................................................................................................ 16
8.3.3
Life Cycle Assessment Conclusion ......................................................................... 17
8.4
Social Sustainability ................................................................................................... 17
8.4.1
Community Consultation Plan ............................................................................... 17
8.4.2
Social Benefits........................................................................................................ 18
8.4.3
Cultural Values ....................................................................................................... 19
8.5
Education................................................................................................................... 19
8.5.1
Complete System ................................................................................................... 19
8.5.2
The End User .......................................................................................................... 19
8.5.3
Maintenance Personnel......................................................................................... 19
8.5.4
Sanitation ............................................................................................................... 20
8.6
Economic Sustainability ............................................................................................ 20
8.6.1
Water Filter System ............................................................................................... 20
8.6.2
Solar Still ................................................................................................................ 22
8.6.3
Conclusions ............................................................................................................ 23
9.0
Feasibility............................................................................................................. 23
9.1
Assumptions and Details for Calculations ................................................................. 23
9.1.1
Water Filter System ............................................................................................... 23
9.1.2
Water Still System.................................................................................................. 23
9.2
Removal Efficiency .................................................................................................... 24
9.2.1
Sand Filter .............................................................................................................. 24
9.2.2
Ceramic Water Filter Candle ................................................................................. 25
9.2.3
Solar Distillation Unit ............................................................................................. 25
9.2.4
Overall Removal Expectation ................................................................................ 26
10.0 Failure Modes and Effects Analysis ....................................................................... 27
10.1
Functional Block Diagram ...................................................................................... 27
10.2
Risk Priority Rating Scale ....................................................................................... 27
10.3
FMEA Analysis Chart .............................................................................................. 28
10.4
FMEA Conclusions ................................................................................................. 30
11.0 Conclusions .......................................................................................................... 30
12.0 Recommendations ............................................................................................... 31
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FINAL REPORT- WATER PURIFICATION DEVIKULAM
2011
13.0 References ........................................................................................................... 33
14.0 Appendix ............................................................................................................. 35
14.1
Decision Making Matrix ......................................................................................... 35
14.2
Sensitivity Analysis................................................................................................. 35
14.3
Pairwise Comparison ............................................................................................. 35
14.4
Life Cycle Analysis of Filter .................................................................................... 36
14.5
Life Cycle Analysis of Still ....................................................................................... 38
14.6
The Ceramic Water Filter (Doultonusa, 2011)....................................................... 40
14.7
Doulton Ceramic Candles and Cartridge Grades ................................................... 44
14.8
Solar Still System.................................................................................................... 46
FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
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FINAL REPORT- WATER PURIFICATION DEVIKULAM
2011
Table of Figures
Figure 1 Parabolic Mirror Reflection.......................................................................................... 7
Figure 2 Design Criteria Weighting - Pairwise Decisions Matrix Results ................................... 8
Figure 3 Drawings of Water Filter System ............................................................................... 11
Figure 4 Drawings of Distillation System ................................................................................. 12
Figure 5 Flow Diagram of Water Treatment System ............................................................... 13
Figure 6 Life Cycle Analysis of Water Filter.............................................................................. 15
Figure 7 Carbon Emissions for Water Filter (LCA, 2011).......................................................... 16
Figure 8 Life Cycle Analysis of Solar Still .................................................................................. 16
Figure 9 Carbon Emissions for Solar Still (LCA, 2011) .............................................................. 16
Figure 10 Functional Block Diagram of Water Treatment System .......................................... 27
Figure 11 Sources of Carbon Emissions (LCA, 2011) ................................................................ 36
Figure 12 Major Impacting Sources (LCA, 2011)...................................................................... 36
Figure 13 Sources of Carbon Emissions (LCA, 2011) ................................................................ 38
Figure 14 Major Impacting Sources (LCA, 2011)...................................................................... 38
List of Tables
Table 1 Report Contents ............................................................................................................ 1
Table 2 Scope of Report ............................................................................................................. 3
Table 3 Strengths and Weaknesses of Filtration (adapted from APEC Water Systems n.d) ..... 5
Table 4 Strengths and Weaknesses of Solar Distillation (Lof, 1961) ......................................... 5
Table 5 Drinking Standards (adapted from WHO 2011) ............................................................ 7
Table 6 Results of Decision Making Matrix ................................................................................ 8
Table 7 Results of Triple Bottom Line Assessment of the Proposed System/s ....................... 14
Table 8 Community Consultation Plan .................................................................................... 18
Table 9 Educational Outcomes of End Users ........................................................................... 19
Table 10 Educational Outcomes of Maintenance Personnel .................................................. 20
Table 11 Cost of Single Water Filter Module ........................................................................... 21
Table 12 Cost of Single Solar Still Module ............................................................................... 22
Table 13 Removal Efficiency - Sand Filter ................................................................................ 24
Table 14 Removal Efficiency - Ceramic Water Filter................................................................ 25
Table 15 Removal Efficiency - Solar Still .................................................................................. 26
Table 16 Decision Making Matrix ............................................................................................ 35
Table 17 Sensitivity Analysis .................................................................................................... 35
Table 18 Pairwise Comparison ................................................................................................. 35
Table 19 Carbon Emissions Produced through Manufacture and Disposal (LCA, 2011) ......... 37
Table 20 Carbon Emissions Produced through Transport (LCA, 2011).................................... 38
Table 21 Carbon Emissions Produced through Manufacture and Disposal (LCA, 2011) ......... 39
Table 22 Carbon Emissions Produced through Transport (LCA, 2011).................................... 40
Table 23 Biodigester Relationship (Camco, 2010) ................................................................... 49
FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
FINAL REPORT- WATER PURIFICATION - DEVIKULAM
2011
1.0 Introduction
1.1 Project Overview
Devikulam is a sparsely populated community situated in eastern India. The 320 locals
struggle daily to obtain the necessary quantities of water to sustain their everyday lives.
Currently the small town relies upon a 30,000L water tank, 3 bores (one of which is saline
and another which is not currently functional) and the local pond for their daily water
supplies. Access to safe drinking water is a fundamental human right and an
indispensable component for maintaining a positive quality of life. The Pitchandikulam
Forest Organisation, working in the Kauveli Bioregion (South-East India), had identified
that the village of Devikulam has inadequate access to a safe water supply. Engineers
Without Borders, paired with the Pitchandikulam Forest Organisation, are in
collaboration to find an environmentally sustainable and culturally acceptable solution
for the water crisis in Devikulam.
1.2 Project Aims and Report Contents
The aim of this project is to provide the community of Devikulam with a reliable supply of
uncontaminated drinking water. It is highly desirable to treat the local water to a level
equal to, or greater than, the levels set by the World Health Organisation (WHO). It is
imperative that the solution is:
•
•
•
•
Cost effective;
Environmentally sustainable;
Socially, economically and culturally acceptable and;
Perceived as being beneficial.
Table 1 Report Contents
Heading
What will be covered
Problem Definition
-
Project Scope
-
Literature Search
-
Initial Design Concepts
Technical Understanding
Sustainability
Feasibility Calculations
-
Failure Modes and Effects Analysis (FMEA)
Conclusions and Recommendations
-
1
Task identification, pre-existing water supply and project
goals identification
What factors the design will address, what factors the
design will not address and project/design assumptions
Pre-existing water purification methods, identification of
plausible treatments, evaluation of plausible water
treatment(s)
How water treatment method was chosen
Description of methods chosen and design drawings
Environmental and social sustainability of system evaluated
Estimations for water usage, estimation for water
production, design dimensions and design assumptions
Evaluation of design through safety model
Summary of current position and viability of the proposed
solution
FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
2.0 Problem Definition
2.0 Task Identification
The vision of the Pitchandikulam Forest Organisation (PFO) is to provide the community of
Devikulam with a reliable and safe supply of water. The primary focus, which was
identified by the E.M.S Lab (2010) results, will be on minimising turbidity, eliminating
bacteria and salinity of the source water from three bore sites situated in the village and
the local pond. By improving the water quality in Devikulam, it is then possible to improve
the overall health of the Devikulam community.
2.1 Pre-existing Water Supply
The community of Devikulam currently relies on two different water supplies for their daily
requirements. Most of the community’s water is supplied by one of the three bores,
however, presently “one of the bores has been considered too ‘saline’ and is no longer
used by the community for drinking purposes, and another of the bores is not functional at
the present time” (EWB 2011). Furthermore, water is supplied to the community through
the local pond, however, this water can be “subject to contamination during the monsoon
season” (EWB 2011), as water that flows into the pond is contaminated. As identified by
the PFO, there are health concerns associated with the consumption of the pond water,
and for this reason, a water purification system must be implemented in the community of
Devikulam.
2.2 Project Goals Identification
The project goals were initially created to come up with a justifiable and acceptable
solution for the problem defined in section 2.1. The goals were created in terms of solving
the water quality issue, the achievements of functions of the designed module as well as
the output of the module. The module will:
•
•
•
•
•
•
•
•
•
•
Improve the water quality, by addressing the three main factors: salinity, turbidity,
bacteria;
Treat Turbidity levels to < 0.5 NTU, Salinity levels to < 100 ppm, with a constant pH
and no traces of Bacteria;
Be an environmentally sustainable and reliable water purification system that
provides clean, uncontaminated water for the Devikulam community;
Be capable of supplying 10 people with 20 litres of clean water daily;
Be a cost effective solution that is can is feasible within the Devikulam economy;
Improve in the general health and hygiene of the Devikulam community by reducing
levels of diarrhoea attributed to contaminated drinking water;
Provide a clean supply of water for drinking, cooking and washing;
Not rely upon reticulated power;
Be seen as beneficial, effective and maintainable by the villages (Maintenance
procedures will be simple and reproducible).
Culturally and socially acceptable, not impeding on community values.
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FINAL REPORT- WATER PURIFICATION - DEVIKULAM
2011
The above goals will be achieved within the Devikulam community so that a sustainable
solution will be implemented to benefit the local community.
3.0 Project Scope
3.0 Project Scope
The project will be dealing with water purification in the community of Devikulam. The
main concept is to treat the contaminated water to an acceptable standard to increase the
health of the local community and to provide a clean and reliable water source. The
purification system will be designed with the project goals in mind, and will be constructed
to remove the contaminants from the water supply.
3.1 Inclusions and Exclusions
The project is not capable of covering all the issues that surround the implementation of a
water purification system in Devikulam, as such, a large scope would take away from the
necessary information regarding the purification system. For this reason parts of the larger
picture are being excluded from the project scope so that the report can focus specifically
on the important aspects of the water purification system. Table 2 displays the scope of
the report:
Table 2 Scope of Report
In Scope
Water treatment capacity
Environmental and social sustainability
Cost effectiveness
Mechanical maintainability
Life cycle of purification system
Out of Scope
Heavy metal cation and anion treatment
By-product management
Position of module within community
Bore’s effect on water access
3.2 Design Assumptions
For the report to be specific and address the required areas, assumptions must be made
where the information is not clear or accessible. Below are the design assumptions for the
water purification system:
•
•
•
•
•
•
There is a sufficient water supply to provide the water purification system with water;
There will be a 24 hour period in which the water can be purified for the ten people;
Each person will only require 20L of water per day (this includes cooking, washing and
drinking);
The hours of sunlight in a day is approximately the same all year;
The villagers will be able to perform small maintenance procedures on the module if
required and;
The average water consumption is the same for men, women and children for all
intents and purposes of the report.
The above assumptions were made so that it was possible to start the feasibility and
design of the project with respect to the project goals.
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FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
4.0 Literature Search
4.0 Water Purification
“Water purification is the process of removing contaminants” (Kostoff et. al 2007), from a
water source so to be used for drinking, washing and industrial purposes. Purification
occurs to limit the levels of certain components of the water so to reduce the potential
associated health risks. “The world health organisation has identified 752 substances that
may be present in tap water” (Sutherland 2008), and it is many of these elements that
purification aims to remove. From “minerals, fungi, and viruses” to “parasites, viruses and
organic matter” (Kostoff et. all 2007) the levels of these elements need to be reduced to
minimal quantities for water to be classified drinkable. Water purification techniques have
evolved with advancing technology over the past decades, from “simple systems based on
the imitation and adaptation of naturally occurring processes” (Brissaud 2006), such as
sand filters, to complex multi stage purification techniques that use such techniques as
“coagulation, flocculation and deionization” (Kostoff et. al 2007). Many different
techniques are still operational around the world depending on the country’s economic
situation and needs.
4.1 Existing Purification Techniques
Presently there are many different techniques that are used to purify water for a variety of
applications. Most purification systems aim to purify water to the standards of the World
Health Organisation so that it can be used as a source of drinking water. A combination of
reverse osmosis, and filtration is one of the main ways in which water is purified in modern
day times.
“Reverse osmosis is a membrane based demineralization technique used to separate
dissolved solids” (Kucera 2010) from water. By using permeable selective membranes and
pressure the system is able to “overcome the ‘osmotic pressure’ allowing water to cross
the membrane from high concentration to low” (McIlvaine 2008). This process is used to
remove ionic contaminants and other dissolved solids form the water.
4.2 Filtration
Filtration is a method of purification used to extract turbidity and sediments from the
contaminated water supply. Sand filters are the most commonly used method of filtration
before reverse osmosis and other such technologies were developed, and it was successful
because it followed a natural system, where water is “filtered through sand in fresh lakes”
(Cartwright 2006). The process of filtration involves the pores of the filtrate; the size of the
pores determines the effectiveness of the purification system. As the water is gravity fed
through the filter, sediment and turbidity are ‘caught’ in the pores between the filtrate,
removing them from the water source. However, this lead to the ‘filter becoming ‘backed
up’ due to the accumulation of contaminants in the filtrate pores, leading to a reduction in
the systems efficacy (Wotton 2002). This is overcome through a backwash technique
developed to remove the contaminants and sediments caught within the filtration system,
restoring it to its original working state.
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FINAL REPORT- WATER PURIFICATION - DEVIKULAM
2011
Table 3 Strengths and Weaknesses of Filtration (adapted from APEC Water Systems n.d)
Strengths
• cost effective
•
•
Weaknesses
• requires backwashing regularly to
maintain filters efficiency
environmentally sustainable
• requires media disposal and replacement
removes majority organic and inorganic • does not remove salts
suspended particles
removes majority of bacteria
• does not remove all chemicals
mechanically maintainable
•
simple operation
•
•
4.3 Solar Distillation
Solar distillation is the technique of harnessing the suns energy (heat) to vaporize water; it
is a traditional method for water purification. The concept of purification by distillation is
simple, water generally has the lowest boiling point out of all the contaminants, by using
the heat of the sun the water can be vaporized before any of the other particulates. By
capturing the vaporized water, a purified water supply can be established, as all of the
original contaminants have been left behind in the original position.
Water has a enthalpy of vaporization of 40.65 KJ/mol (Kucera 2010), meaning that at
373.15oK (100 oC) 40.65KJ/mol is required to transform liquid water into gas. During
distillation all this energy is required from the heat of the sun, and during direct sunlight
the energy produced by the sun can be up to 590.4 KJ/hour/m2 (Qiblaway et. al 2007).
From this it can be seen that it is feasible to gain purified water from distillation as the sun
provides all the energy that is required and it comes at no cost. However, there are always
complications that arise during this process, problems like heat transfer and sun exposure.
Much heat is generally lost through absorption from other materials; this absorption
decreases the amount of heat being transferred to the water and in turn the volume of
water being vaporized.
Table 4 Strengths and Weaknesses of Solar Distillation (Lof, 1961)
Strengths
• potential for expansion from modular design
• removes salinity, turbidity and bacteria
• environmentally sustainable
• mechanically maintainable
• cost effective
Weaknesses
• limited flow rate
• requires solar energy
• removal of healthy minerals
4.4 Biogas
Biogas is a naturally occurring gas from the decomposition of organic matter. “Biogas is
produced through anaerobic digestion or fermentation, whereas hydrocarbons are
released as the bi-product” (Jian, 2009). The hydrocarbon that is the main bi-product of
the decomposition reaction is methane; along with this there is also a large production of
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FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
carbon dioxide. In third world countries (India), biogas is produced “through the
decomposition of cow manure and green waste” (Jian, 2009)). From this methane is
collected and used for such activities as cooking and lighting. The use of biogas is a
conventional renewable for of energy, however, it can produce large quantities of carbon
dioxide and other dangerous gases into the air.
Biogas is a replacement for conventional power, and with the unreliability of the power
grid in developing parts of the world, it is the only sustainable form of energy. For its
production a digester is required, it is here where all of the organic material is broken
down for the production of methane. The use of biogas provides a cheap and economically
sustainable source of energy for developing countries and isolated communities.
The application is biogas technology in isolated communities is one that is technically
suitable and sustainable. In communities without reticulated power, a digester can be set
up at a minimal cost, which with the constant addition of organic matter can provide a
combustible gas free of cost. This gas can be harnessed for heating and cooking, and
provides a sustainable alternative to conventional power in isolated and poor
communities, allowing for improvements in hygiene and quality of life.
4.5 Sanitation
Developing countries have low levels of sanitation and lack basic general health and
sanitation. The World Health Organisation estimates that “1100 million people worldwide
drink unsafe water” and that the “vast majority of diarrheal disease in the world (88%) is
attributed to unsafe drinking water” (Suthar 2009). It is the particulates and sediments in
the water which are responsible for the diseases and the reason why the World Health
Organisation set drinking water standards so to minimize the risk of potential health
detriments. Demonstrated below in Table 3, are the drinking water standards set by the
World Health Organisation.
There are secondary affects that are also associated with the consumption of
contaminated drinking water. It is know that contaminated drinking water is the main
cause of diarrheal disease, plus the fact that Devikulam has “low levels of sanitation” (EWB
2011) that ultimately leads to the significant health and hygiene risks to the local
inhabitants. The problem associated with drinking contaminated water resonates with the
fact that levels of sanitation are low within the Devikulam community. This brings health
risks that could have detrimental effects on the surrounding community and is the reason
why the drinking water standards set by the World Health Organisation need to be
adhered to.
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FINAL REPORT- WATER PURIFICATION - DEVIKULAM
2011
Table 5 Drinking Standards (adapted from WHO 2011)
Parameters
pH
TDS
TA
TH
Na+
Ca2+
Mg2+
CO32HCO3ClSO42F-
ISI Standards
Acceptable Limit
7.0 – 8.5
500
200
200
50
75
30
75
30
200
200
1
WHO Standards
Maximum
Permissible Limit
6.5 – 9.2
1,500
600
600
200
100
200
1,000
400
1.5
6.5 – 9.2
500
100
75
150
75
150
200
200
1
4.6 Parabolic Reflection
The parabolic mirrors reflective properties are due to its shape, it is this shape where any
incident ray of light is reflected onto the focal point above the mirrors surface. The use of a
parabolic mirror for distillation is an effective way of heating the water supply; if the
source is situated in the focal point of the mirror than all of the energy striking the surface
of the mirror will be reflected upon the supply
(seen in Figure 1). By using a cylindrical pipe, the
focal point of the mirror is situated at the radius of
the circle. By incorporating a large surface area
into the parabolic mirror design then the efficiency
of heating the water supply can be increased to an
extent where evaporation comes almost
instantaneously. Through this process the
purification of the water supply can be a very
efficient and an environmentally sustainable
Figure 1 Parabolic Mirror Reflection
process.
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FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
5.0 Initial Design Concepts
For this phase the initial
nitial design proposals were evaluated against the project’s aims and if
discrepancies appeared then that particular design was forgone. For the process of
evaluating the most suitable preliminary design, a Decision Making Matrix (Refer to
Appendix 14.1)) was used to appraise the proposed concept designs against four key criteria
pertinent to the project’s
ct’s core aims. These criteria were:
were
•
•
•
•
Water purification ability (removal efficiencies of turbidity, salinity and bacteria);
Cost effectiveness (cost of materials and time period specific
specific materials are effective);
Sustainability
ity (environmental impacts) and;
Modular design (capacity to have more than one unit function harmoniously together).
Each of the four key criteria were given a weighting scale based on their comparative
pertinence
ce to one another through the utiliseation of a Pairwise Criteria Matrix (Refer to
Appendix 14.2).
). The outcome of this comparison is illustrated in Figure 2..
Design Criteria Weighting
10%
20%
50%
Purification ability
Cost Effectiveness
Sustainability
20%
Modular
Figure 2 Design Criteria Weighting - Pairwise Decisions Matrix Results
Weighting the criteria enabled analysis of the most plausible designs, with the conclusion
being
eing objective and supported by apposite decision. A five point rating scale was used;
founded on relevance to a set standard. In this circumstance the standard was if nothing
was implemented to purify water into the Devikulam community. The rating scale was one
through the five; much worse, worse, same (standard), better and much better than the
standard. Thus, the design with the highest rating total was deemed as the design to
proceed with. Table 4 displays the results of the Decision Making Matrix:
Table 6 Results of Decision Making Matrix
Conventional Solar Still
Total
3.5
Parabolic Trough + Rapid Type
Filter
4.1
The Decision Making Matrix evaluates
evaluate each design in accordance, and respect to, the set
criteria which are based on the project’s aims. It can be concluded from this matrix that a
parabolic trough plus a rapid type filter be used to effectively, and aligned with project
projec aims,
8
FINAL REPORT- WATER PURIFICATION - DEVIKULAM
2011
adequately address the requirements for purified water in the village of Devikulam. (Refer
to Appendix 14.3 for Sensitivity Analysis)
6.0 Technical understanding
The method of purifying the waste water for the community of Devikulam will be subdivided into 5 sections; sand filtration, ceramic water filtration, parabolic reflection, solar
distillation and biogas. All the methods and stages will be clearly stated below.
6.0 Sand Filtration
A rapid type sand filter is utilised as the first stage of filtration. During the first phase,
contaminated water will be flowing through the sand filter to remove the large organic
molecules from the wastewater. This rapid type system is being used as it is the most viable
method for first stage filtration. Sand filtration helps to reduce up to 80% of turbidity, up to
5% of organic material, up to 10% of water colour and almost 90% of bacteria and Coliforms
from the wastewater. Furthermore, due to its low cost and its efficiency it will be used as
the first method of purification.
6.1 Ceramic Filter Candle
A ceramic candle water filter is utilised as the second stage of filtration. The main purpose
of using the filter candle is to block the passage of any molecules that are larger than water
molecules. This process can be also named osmosis. Osmosis is defined as the movement of
water molecules from the region of higher water concentration to a region of lower water
concentration via a semi-permeable membrane. A ceramic water filter will only allow water
or any molecules that are smaller than water molecules to pass though to the other side of
the filter. Additionally, the ceramic water filter contains silver substances, which help to
incapacitate or kill bacteria and prevent the growth of algae on the receptacle. During this
process, the contaminated water is poured in the filter and passes through it into the
receptacle below. The receptacle usually is fitted with a tap. Importantly, a ceramic water
filter contains activated carbon in the inner core which helps to absorb organic compounds
such as chlorine. Therefore, it is expected that once the contaminated water pass through
the filter stage of the purification process the only impurity left within the water will be salt.
6.2 Solar Distillation – Cylindrical Pipe
Solar Distillation is utilised as the third stage of purification to remove the remaining salt
compound from the water. The main purpose of using this technique is to utilise the energy
from the sun to generate heat energy to vaporise water. As salt molecules are smaller and
have a higher boiling point than water molecules, a solar distillation device is one of the
most efficient and low cost techniques available. Water generally has a lower boiling point
(100°C) than any other contaminant, by using this knowledge water can be vaporised before
any other particulates. Once the vaporised water has cooled down, a purified water supply
can be established. However, due to time restrictions and the efficiency of reflection of
sunlight, another two main designer features have to be introduced; parabolic reflection
and biogas.
6.2.1 Parabolic Reflection
Parabolic Reflection is the main design feature of this water treatment device. Due to the
time restrictions, the treatment has to be more effective and efficient. The introduction of a
parabolic mirror is needed to increase the rate at which the water boils. With the use of a
9
FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
parabolic mirror, there is an increase in incident rays of light reflected onto the focal point
above the mirrors surface where the water will be positioned. The use of a parabolic mirror
for distillation is an effective way to speed up the heating process; if the source is situated in
the focal point of the mirror then all of the energy striking the surface of the mirror will be
reflected onto the water (providing 100% reflectivity). By using a cylindrical pipe, the focal
point of the mirror is situated at the radius of the circle. By incorporating a larger surface
area into the parabolic mirror design then the efficiency of heating the water supply can be
increased to an extent where evaporation is almost instantaneous. Through this process the
purification of the water can be a very efficient and an environmental sustainable process.
6.2.2 Biogas
Biogas can be used if the preliminary system of parabolic reflection becomes redundant.
The thinking behind having the additional biogas system it that it can be used to provide the
water treatment system with energy during times where the preliminary system is out of
order or cannot function effectively. Biogas is a naturally occurring gas from the
decomposition of organic matter. It acts to heat up the pipe to boil the filtered water when
ignited. Thus, the salt will be removed from the water which can now be consumed.
7.0 Engineering Sketches
The following drawings show the design and the dimensions of the modular water
treatment system (Detailed on following pages).
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FINAL REPORT- WATER PURIFICATION - DEVIKULAM
7.1 The Filter System
Figure 3 Drawings of Water Filter System
11
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FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
7.2 The Solar Still
Figure 4 Drawings of Distillation System
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FINAL REPORT- WATER PURIFICATION - DEVIKULAM
2011
7.3 Flow Diagram
QUICK OVERVIEW
Figure 5 Flow Diagram of Water Treatment System
IMPURE WATER IN
SAND
VOID
STAGE ONE, SAND FILTER:
REDUCES TURBIDITY, REMOVES
LARGER
PARTICLES,
RAPID
FLOW
HOT WASTE FROM BOILER
REINTRODUCED TO SYSTEM,
INCREASES EFFICIENCY
WATER
VAPOUR
INTO
CONDENSER CONTAINS NO
IMPURITIES.
CONDENSER
STAGE TWO, CERAMIC FILTER:
REDUCTION OF TURBIDITY UP TO
99.69%
(RUST, SAND, SEDIMENT, ALGAE)
REDUCTION UP TO 99.99%
REMOVAL UP TO 99.99%
BOILER
(PARABOLIC MIRROR OR BIOGAS)
FRESH CLEAN WATER OUT.
QUALITY WITHIN
ACCEPTABLE DRINKING
REMOVAL UP TO 99.99%
REMOVAL OF GUINEA WORM100%
HOT WASTE WATER
WITH CONCENTRATED
SALT,
REINTRODUCED
INTO BOILER
CLEAN WATER OUT, ONLY
IMPURITY PRESENT IS SALT.
FLOWS TO BOILER
WATER FROM FILTER SYSTEM
13
HOLDING TANK:
WATER AVAILABLE TO THE
VILLAGE AS REQUIRED.
FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
8.0 Sustainability
Sustainability is the key issue that faces all designs. Consideration needs to be taken as to
whether the design is environmentally, socially and economically sustainable. Table 5
shows the results of a triple bottom line assessment, each issue is then considered in depth
in the preceding sections.
8.1 Triple Bottom Line Assessment
Table 7 Results of Triple Bottom Line Assessment of the Proposed System/s
CRITERIA
RESULT
(1-5)
2
4
•
•
•
•
•
3
•
•
Energy
ENVIRONMENTAL
DESCRIPTION
Resources
•
Impact
5
SOCIAL
Employment
•
•
•
5
•
5
•
•
•
Culture
Education
•
5
•
Initial Cost
ECONOMIC
4
Operational
Cost
3
Profit
14
•
•
•
•
•
•
•
•
PVC piping requires energy to produce, petroleum based.
Transportation uses large amounts of energy.
Production of ceramic candle filter is energy intensive.
Reflective surface production, material is petroleum based.
Uses PVC and copper, both non-renewable, but can be
recycled.
Sand recyclable.
Initial impact on environment substantial, due to
manufacturing process required for some components.
Once system is running negligible impact as it is self
sustaining.
Environmentally friendly waste produced.
Initial setup will create a number of jobs, however these
will be unpaid.
Ongoing maintenance personnel will be paid to maintain
system, small number of jobs created.
Respects traditional local values, does not impose Western
values upon the community.
Aims to improve the standard of living.
Is culturally appropriate.
Creates an awareness of the risk of poor water and lack of
sanitation.
Offers the community a chance to increase their knowledge
of new technologies.
Components can be bought ‘off the shelf’ from local
hardware.
Single module costing not more then $200 (Filter and Still)
Limited operational costs, biogas free.
Main operational cost being filter replacement.
Solar energy used to heat water.
Simple system meaning maintenance cost from staffing
perspective is limited.
Highly durable, limiting breakages and failure.
Community may be able to make profit from salt.
Profit not a key requirement, rather improvement on
quality of life
FINAL REPORT- WATER PURIFICATION - DEVIKULAM
2011
8.2 Environmental Sustainability
A key goal of the proposed system was to ensure that it had minimal impact on the
environment. This has been done by, where possible, using recycled materials and
recyclable materials, where this is not possible the materials then selected must give the
longest operating life possible.
Materials selected for the design have been evaluated to be as environmentally
sustainable as possible. Selection considerations has taken into account the manufacture
and processing required to produce the materials, the below life cycle assessment
summaries all considerations.
8.3 Life Cycle Assessment
8.3.1 Water Filter System
A lifecycle assessment has been completed using the Lifecycle analysis calculator available.
Assumptions have been made: activated carbon used within the ceramic filter has been
assumed as equivalent to the production of clay brick. Assumed lifespan of filter internals
is 1 year.
The assessment has been broken down into a single module. The assessment for the water
filter system can be seen in Figure 9. It is assumed that the modules will be manufactured
within Australia and then sent to Devikulam. The assessment has been biased towards
producing more waste and C02. COMPLETED FOR SINGLE MODULE
Figure 6 Life Cycle Analysis of Water Filter
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FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
Figure 7 Carbon Emissions for Water Filter (LCA, 2011)
Within the water filter system the sand used in the first stage can be sourced locally,
reducing energy usage and C02 emissions. The ceramic filter will however have to be
transported into the region and will be an ongoing impact for the life span of the system.
8.3.2 Solar Still
The assessment for the solar still system can be seen in Figure 11. The solar still is unique
in design and assumptions had to be made for the reflective surface; it is assumed that the
energy required to make the reflective material is approximately equivalent to the
production of a standard mirror.
Figure 8 Life Cycle Analysis of Solar Still
Figure 9 Carbon Emissions for Solar Still (LCA, 2011)
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FINAL REPORT- WATER PURIFICATION - DEVIKULAM
2011
8.3.3 Life Cycle Assessment Conclusion
Each system has been analysed separately increasing energy usage and CO2 production
significantly in the transport stage. This will be offset by the exclusion of small components
required within the system.
There are minimal ongoing energy requirements to run the system. Biogas is used as an
alternative to solar when it is unavailable; the biogas is considered carbon neutral and
therefore is not considered in the production of CO2.
8.4 Social Sustainability
When introducing a new system to a community a key number of points must be
considered. These are:
•
•
•
•
Cultural practices and expectations.
Complexity of the system and required level of understanding required to operate the
system.
Advantage to the community.
The long term goal is for the community to manage and maintain the system without
outside help.
8.4.1 Community Consultation Plan
Communities like to input into ideas/designs that improve their overall community. To
assist in understanding the system, community involvement is essential at every level. A
strong side-benefit comes from pride and increased self-worth gained from contributing to
improved living standards.
In order to communicate the proposed system and design with the Devikulam community,
it was decided that the most effective method would be a two pronged approach. It was
concluded that both approaches must be conveyed using culturally familiar methods, such
as dance and stories.
The two pronged approach would address the whole community and then focus on
educating children at school. The initial proposal would be presented at community
gathering in an informal manner. It will be important to utilise the connections and
familiarity of the EWB staff currently working with the community to introduce the design
and receive feedback.
Potential barriers to implementation have been indentified; these must be overcome to
increase the chance of success for the systems acceptance.
•
•
•
17
Communication: While English is widely spoken in the community, Tamil is most common
and used in everyday conversation. A translator may be required to assist in
communication.
Technical understanding: The community may not understand how the system works and
therefore view the system as ‘suspicious’ believing that it might be ‘bad’.
Sanitation: The community needs to understand the risks associated with poor sanitation
and how this affects their water.
FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
These barriers can be overcome through having an in-depth understanding of the values
and beliefs of the community as well as building trust and a repour with the members of
the community. The following table has been adapted from the best practice guide and
details the community consultation steps for the system.
Table 8 Community Consultation Plan
CONSULTATION STEPS
1. Presentation
Introduction
and
DESCRIPTION
•
•
•
•
•
•
•
2. Installation
3. Education
•
4. Trial Period
Feedback
and
•
•
•
5. Ongoing Evaluation
and
Community
Consultation
•
•
•
Approach key members within the community to introduce
design.
Arrange meeting with whole community to describe the
system, its purpose and likely benefits to the community.
i.e. Health improvement.
Also receive feedback on initial feelings regarding the
system.
Train maintenance staff.
Setup system in appropriate places.
Complete training of maintenance staff.
Educate the wider community on the system as well as
proper sanitation and the benefits of clean water.
Implement an education program into schools using
culturally appropriate techniques.
Monitor operation for a period of 4 weeks.
Facilitate meetings with key members of the community to
gather feedback.
Community meeting to gather wider community feedback
on system.
Continued monitoring of system.
Supervision of maintenance staff until deemed fully
competent.
Continued facilitation of feedback and suggestions for
improvements of the system.
(Best Practice Guide for Students and Tutors, 2011)
8.4.2 Social Benefits
In undeveloped nation’s illness from water related diseases/bacteria is a common problem
and accounts for approx 2.2 million deaths per year globally. (World Health Organisation,
2011).
Clean water will improve the overall health of the community through a reduction of water
borne illnesses. A side benefit from this will include a generally happier population, a
reduction in the strain required to care for ill people allowing for an increase in social
interaction and able bodied people fit for work leading to an increase in income.
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FINAL REPORT- WATER PURIFICATION - DEVIKULAM
2011
Education into proper sanitation methods and an understanding of the importance of
clean drinking water should also help to raise the living standard.
8.4.3 Cultural Values
Research into cultural practices has shown that the proposed design meets cultural
expectations and should not infringe on any cultural beliefs or practices. Any problems
that arise from feedback showing infringement on cultural beliefs or practices will be dealt
with promptly with consultation with community members, allowing the solution to be
culturally acceptable.
8.5 Education
8.5.1 Complete System
While the proposed system is simple, the community will require education in regard to
the system’s use and maintenance. Overall it will be important for all members to have a
basic understanding of the system, which will aid in long term acceptance and use of the
system. Education will be broken into two sections; the end user (most of the community)
and maintenance personnel.
8.5.2 The End User
The end users, being the people of the community, will be accessing and using the system
on a daily basis. It is highly important that this majority has a basic understanding of the
system and it use, as the system is modular, and may be implemented in-home or at the
community level. The community must understand that not all water is safe and that the
reason for the water purification system is to make the water safe for use. The system will
be used by adults and children therefore, a multi-prong approach can be taken, children
can be educated at school, along with community meetings and small group
demonstrations. Emphasis should be place on the dangers of unclean water and a basic
run down of what the system does and how to obtain clean water from it.
Table 9 Educational Outcomes of End Users
Expected Education Outcomes – The End Users
End users should be able to demonstrate:
A basic understanding of the system.
A basic understanding of the associated risks of unclean water.
Use of the system and obtaining clean water.
8.5.3 Maintenance Personnel
During building/installation of the system key members of the community will be selected
and trained to a higher level of understanding of the system. Proper maintenance is
required to ensure the system continues to function as required; these people will
maintain and repair the system. Education will include in-depth troubleshooting of
problems and how to rectify them, a comprehensive understanding on how the system
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FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
functions as well as cleaning and replacement of components of the system. Selected
candidates should be fluent in both English and the local language, they must also be
respected members of the community; their understanding and standing within the
community will aid in acceptance and continued use of the system.
Table 10 Educational Outcomes of Maintenance Personnel
Expected education Outcomes – The Maintenance Personnel
Maintenance Personal should be able to demonstrate:
A complex understanding of the system.
A complex understanding of the associated risks of unclean water.
Disassemble and reassemble the system.
Troubleshoot and rectify problems within the system.
8.5.4 Sanitation
Poor sanitation is a key issue within the community, the common practice of open
defecation must be addressed whilst being mindful of cultural practices. Educating the
community on proper sanitation techniques and associated risk of human/animal waste in
their water will aid in reducing the chance of pathogens in the water before purification.
As the community has access to the internet this tool can be used to help educate the
community in relation to sanitation.
If the containments within the water can be reduced/minimised before the water passes
into the system, this will reduce the stress on the system, maximising the life span of the
components.
8.6 Economic Sustainability
8.6.1 Water Filter System
The design cost has been evaluated using the average price of the materials. A number of
suppliers were contacted for the pricing of each individual component of the system.
The water filter system consists of PVC piping, sand and a ceramic candle water filter. The
sand is held in place within the tube by a simple fine mesh membrane. (For details see
engineering drawings).
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FINAL REPORT- WATER PURIFICATION - DEVIKULAM
2011
Table 11 Cost of Single Water Filter Module
Component
Number
1
2
Description
PVC pipe, system housing.
Wall thickness = 4mm
Sand:
Bedding
Sand,
medium grain.
3
End caps for PVC pipe
4
PVC pipe coupling caps
5
6
Doulton
ceramic
filter
candle.
Mesh-membrane to hold
sand.
Specifications
Height = 880mm
Ø = 250mm
Unit Cost
Total Cost ($)
Quantity
$22 per/m
880mm
19.15
Medium grain $63.17/tonne
0.00736m3 =
13.2 kg
0.85
Ø = 250mm capping
$4.49
4
17.96
Ø = 250mm
$13.74
4
54.96
10 inch unit
$19.95
1
24.95
Ø = 250mm
0.049m2
$0.85
1
0.85
TOTAL (AUD)
$119.52
It is assumed that the internal parts of the filter will have an approximate life span of 1
year. This means that in a worst case scenario, the village will have to re-purchase the filter
system once a year along with approximately $100 in freight transporting the parts from
Australia to Devikulam. This brings the annual cost to $219.52.
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FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
8.6.2 Solar Still
The design cost has been evaluated using the average price of the materials. A number of
suppliers were contacted for the pricing of each individual component of the system.
Table 12 Cost of Single Solar Still Module
Component
Number
Description
Copper pipe (water
flow) Type L used in
residential
and
commercial
water
supply and pressure
applications.
1
2
Copper pipe (gas flow)
3
Wood for the frame
Specifications
Ø = 14.13mm
(conforms to
$22.00/m
standard 1 1/8
inches)
5
6
7
Total
Cost($)
Quantity
4m
88.00
4m
32.00
$25.00/m2
2m2
50.00
4.60/each
2
9.20
4.8/each
1
4.8
$16.50/each
1
16.50
Ø = 19.1mm
(conforms to $8.00/m
standard ¾ inches)
2 part system 98.5%
Reflective surface
reflectivity, 10 year
guarantee
Copper elbows (water
Short elbow to fit 3
flow)
inch pipe
T-junction to fit 3
T-junction
inch pipe
Regulator:
2Kg/h LPG, 2.8 kPa,
Max inlet Pressure
1750 kPa. Inlet
Fitting:
CGA-510
Gas
regulator
and
POL with soft bull
fittings/hose
nose (7/8" - 14T-LH)
Hose:
Quality 1.8 meter
8mm1/4"BSPF, Max
WP 7kPa, AS/NZS
1869
4
Unit Cost
TOTAL
$200.5
It can be assumed that in a worst case scenario the still will have to be replaced between
10 years. This means that the still will cost the village approximately $30.05 per year in
replacement parts and $100 in freight from Australia to Devikulam.
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FINAL REPORT- WATER PURIFICATION - DEVIKULAM
2011
8.6.3 Conclusions
The initial cost of the water treatment system is approximately $320.02. There is also an
additional freight cost of approximately $250, giving a complete initial cost, including
transport, of $570.02. Additionally, there will be an annual cost of $149.57 in
maintenance.
In small villages such as Devikulam, each person has an average income of $500 a year
(Sanford, 2003). The module produces water for 20 people with a combined income of $10
000. This indicates that it is feasible for the village to be able to easily afford the costs of
the system annually.
9.0 Feasibility
9.1 Assumptions and Details for Calculations
Each person in the village has been allocated 20L of purified water for drinking, cleaning and
cooking as per a recommendation by the UN (UN 2010). Design specifications stipulated
that the system must be able to purify water for 10 persons. The village contains 320
persons therefore 16 modules are needed.
The design proposed consists of two parts; Part A: A gravity fed sand filter flowing into a
ceramic candle filter (see engineering drawings for details). Part B: A solar distillation unit.
Each module must be portable as per design requirements.
9.1.1 Water Filter System
The sand within the filter system makes the weight of the filter unit a key concern. It was
concluded that each module will contain 13kg of sand and have a total weight of 15kg. This
weight is deemed as acceptable for each module maintaining the portability of the system.
The system will be contained within a PVC pipe with a diameter of 250mm and a height of
550mm, allowing the system to be robust.
9.1.2 Water Still System
The energy available to the system is controlled through the size of the concave mirror. It
was decided that the mirror would have a length of 4000mm and a radius of 500mm, with
an angle of curvature of 180 degrees.
Another controlling factor is the volume of water which the copper pipe can hold. The
allocated pipe was 4m long with a radius of 14.13mm. This has a resulting volume of 2.129L.
There are also known efficiencies within the still involving solar radiation absorption. The
assumed efficiency of the reflective surface is 95%. There is also an assumed radiation
absorption efficiency for the copper piping of 64%.
The flow rate of the still is the main effecting factor as it has to be steady enough to allow
the water to evaporate within the time it is in the pipe. The minimum flow rate for the
piping is 1L/2.34mins. This flow rate uses all 7.8hrs of sunlight to process 200L, however
there is 32.5 MJ of excess energy at this flow rate.
23
FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
Using this excess energy a maximum flow rate was calculated and was found to be
1L/1.54mins. This produces 304L of water in 7.8hrs and would give the village the ability to
produce more water if necessary.
The excess energy also allows for an output efficiency of less than 100% e.g. 80% efficiency
It was also calculated that to produce enough biogas to distil the 200L of water in the case
of rain, the approximate waste from fifteen cows would be needed. This would then have to
be stored in a digester with a volume of 20m3 and then further transferred into a gas
storage container which can hold the 3.4 m3 of gas required for distillation. It should also be
noted, however, that Devikulam only receives at most ten days of rain, thus meaning the
biogas use will be infrequent.
9.2 Removal Efficiency
9.2.1 Sand Filter
A rapid type sand filter is utilised as the first stage of filtration, it is expected to remove the
larger organic particles and 80% of the turbidity. A rapid type system was determined as
the most viable method for the first stage filtration. Details on the efficiency of the system
are detailed in the following table.
Table 13 Removal Efficiency - Sand Filter
Problem
Expected Improvement
Turbidity
Organic Material
Water Colour
Bacteria and Coliforms
Reduction of turbidity by up to 80%
Reduction in organic material by 5%
Removal of water colour by up to 10%
90 % removal of coliforms, 50-90 %
removal of cryptosporidium and
Giardia cysts,
Table: (ITACA, 2011)
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FINAL REPORT- WATER PURIFICATION - DEVIKULAM
2011
9.2.2 Ceramic Water Filter Candle
A Doulton 5" Super Sterasyl Ceramic Filter Candle type water filter is utilised as the second
stage of filtration, the ceramic candle is expected to remove particles/organic
materials/bacteria that passed through the sand filter. Removal efficiencies are detailed in
the following specifications as retrieved from the manufacturer.
Table 14 Removal Efficiency - Ceramic Water Filter
Problem
Expected Improvement
The Doulton 5" Candle is NSF Certified Standard 42 & 53 for the reduction of:
Turbidity
Reduction of turbidity by up to 99.69%
Particulates
(rust, sand, sediment, algae) Reduction up to 99.99%
Taste and Odour
Removal of up to 99.99%
Bacteria and Coliforms
Removal up to 99.99%
Guinea Worm
100% Removal
Table: (DoultonUSA 2011)
First stage:
The first stage consists of Doulton supercarb ceramic which provides genuine sub-micron
filtration. The cartridge reduces fine particulate matter, bacteria, cysts and turbidity.
Second stage:
The incorporation of silver locked within the ceramic structure gives enhanced
bacteriostatic and self sterilizing properties, preventing the growth of bacteria.
Third stage:
An inner core of activated carbon block removes chlorine and organic compounds.
It is expected that once the water has passed though the filter stage of the purification
process the only impurity left within the water will be salt.
(DoultonUSA 2011)
9.2.3 Solar Distillation Unit
The design of the solar still unit has moved away from the conventional solar still to a
unique module, yet it still works on the same principle of boiling water, collecting the
vapour and condensing it.
Solar stills are proven to be effective in the purification of water. Solar distillation removes
all salts as well as biological contaminants (for example, cryptosporidium, E. coli, etc.) It is
expected that all salts will be removed.
Note: Turbidity, organic material, water colour, bacteria and coliforms will have been
removed by the filter system. In the event of a partial failure of the filter system the below
details the expected removal of particles left in the water after partial filtration.
25
FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
Table 15 Removal Efficiency - Solar Still
Problem
Expected Improvement
Salt
Turbidity
Organic Material
Water Colour
Bacteria and Coliforms
Reduction of salt by 100%
Reduction of turbidity by 100%
Reduction in organic material by 100%
Removal of water colour by up to 90%
90 % removal of coliforms, 50-90 %
removal of cryptosporidium and
Giardia cysts,
The primary disadvantage of distillation is that any material that has a lower boiling point
than the water will boil off along with the water; this may include oils, herbicides/pesticides.
This will not be a concern in the system as the pre-filtration will remove these impurities.
After passing through the solar still all impurities are expected to have been removed.
9.2.4 Overall Removal Expectation
It is expected that after passing through both systems the water quality will be clean of all
impurities and be within the acceptable range for drinking water.
26
FINAL REPORT- WATER PURIFICATION - DEVIKULAM
2011
10.0 Failure Modes and Effects Analysis
10.1 Functional Block Diagram
Water Treatment
Module
Ceramic Filter
Ceramic Filter
PVC End Caps/
Coupling Caps
PVC Piping
Figure 10 Functional Block Diagram of Water Treatment System
10.2 Risk Priority Rating Scale
Severity (Sev)
1
2
3
4
Negligible
Marginal
Critical
Catastrophic
Probability (Prob)
1
2
3
4
Improbable
Remote
Occasional
Expected
Detection Probability (Det)
1
2
3
4
Certain
Likely
Possible
Impossible
27
Mesh Membrane
Water Filter
System
Water Distillation
System
Sand Filter
Solar Distillation
Sand
Reflective Surface
Biogas
Distillation
Copper Piping
Gas Hose
Gas Regulator
FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
10.3 FMEA Analysis Chart
Item
Failure Mode
Causes (Failure Mechanism)
Decomposition of Material
PVC Piping
Fracture/Leak
Long Term Exposure
Temperatures
to
Decomposition of Material
PVC End Caps/ Coupling
Fracture/Leak
Caps
Stress Fractures
Long Term Exposure
Temperatures
Sand
Excess Particle Build
Lack of Maintenance
Up
Mesh Membrane
Fracture
Ceramic Filter
Excess Particle Build
Lack of Maintenance
Up
Fracture
28
to
Term
Exposure
Leakage of Water
Reduction of Gravitational Pressure
Reduction of Production Rate
Disenables the Filtration System
Reduces Effectiveness/Efficiency of Filtration
System
Leakage of Water
Reduction of Gravitational Pressure
High Reduction of Production Rate
Disenables the Filtration System
Reduces Effectiveness/Efficiency of Filtration
System
Leakage of Water
Reduction of Gravitational Pressure
Reduction of Production Rate
Disenables the Filtration System
Reduces Effectiveness/Efficiency of Filtration
System
Leakage of Water
Collapse of Filter System
Leakage of Water
Reduction of Gravitational Pressure
High Reduction of Production Rate
Disenables the Filtration System
Reduces Effectiveness/Efficiency of Filtration
System
Disenables the Filtration System
Reduces Effectiveness/Efficiency of Filtration
System
Stress fractures
Long
Effects
to
Collapse of Sand Support
Spread of Sand through System
Disenables the Filtration System
Reduces Effectiveness/Efficiency of Filtration
System
High Disenables the Filtration System
Risk Priority Rating
Se Pro De RP
v
b
t
N
1
8
1
8
2
4
2 16
3
24
2
1
1
2
3
Recommended
Improvement
Risk Priority Rating
Se Pro De RP
v
b
t
N
1
1
2
3
3
2
6
6
12
18
16 The use of UPVC to resist
8 decomposition
8
16
24
2
1
1
1
3
2
16
2
12
1
1
2
3
8
8
16
The use of UPVC to resist
24 decomposition
1
1
2
3
6
6
12
18
16
4
8
8
8 Reinforcing the PVC with
16 a stainless steel frame to
24 support it
2
1
3
1
1
2
3
16
18 Using sand with different
particle size in order of
biggest at the top to
12 smallest at the bottom
12 Using a stainless steel
12 support
18 Using a larger ceramic
filter bulb to lengthen the
12 time
before
needed
maintenance
24
2
3
2
1
3
1
1
2
3
4
4
2
2
2
2
4
2
2
3
2
3
2
3
3
3
2
3
2
2
2
3
4
2
3
3
2
3
2
1
2
3
2
12
2
6
6
6
12
18
12
9
1
2
3
3
3
2
12
6
6
12
18
3
1
2
1
3
4
2
6
6
6
9
6
24
FINAL REPORT- WATER PURIFICATION - DEVIKULAM
2011
Temperatures
Decomposition of Material
Copper Piping
Leakage
Lack of Maintenance
Long Term Exposure
Temperatures
Gas Hose
Leakage
Decomposition of Material
Gas Regulator
Non-Regulation
Stuck Regulator
to
Decomposition of Material
Reflective Surface
Loss of Reflectivity
Long Term Exposure
Temperatures
29
to
Reduces Effectiveness/Efficiency of Filtration
System
Leakage of Water
Leakage of Gas
Reduction of Production Rate
Disenables the Distillation System
Reduces Effectiveness/Efficiency of Distillation
System
Leakage of Water
Leakage of Gas
Reduction of Production Rate
Disenables the Distillation System
Reduces Effectiveness/Efficiency of Distillation
System
Leakage of Water
Leakage of Gas
High Reduction of Production Rate
Disenables the Distillation System
Reduces Effectiveness/Efficiency of Distillation
System
Leakage of Gas
Reduces Effectiveness/Efficiency of Distillation
System
Reduction of Production Rate
Free Flowing Gas
Uneven Heating
Reduces Effectiveness/Efficiency of Distillation
System
Uncontrolled Heating
Reduction of Production Rate
Disenables the Distillation System
Reduces Effectiveness/ Efficiency of Distillation
System
Reduction of Production Rate
High Disenables the Distillation System
Reduces Effectiveness/ Efficiency of Distillation
System
2
1
3
2
3
2
1
3
2
3
2
1
3
2
3
4
2
4
2
3
2
2
3
2
2
3
2
2
2
2
3
2
2
3
2
16
8
8
16 Coating the copper with a
24 protective
layer
to
prevent
in
16 oxidation/tarnishing
high
temperature
6
18
12
18
12
8
24
16
24
Regular inspections to
insure coating is intact
and copper is not
oxidising/decomposing
16
24
4
2
1
1
4
4
2
2
Replacing the hose after
16 specific periods of time
16
3
2
Regular testing of the
regulator
2
2
16
24
2
1
3
2
3
2
1
3
2
3
2
1
3
2
3
3
1
3
2
2
2
2
3
2
2
3
2
2
2
2
3
Replacing the reflective
16
surface after a certain
16 period of time
24
2
2
3
16
2
16
6
18
12
18
12
1
6
4
6
4
1
18
12
18
12
18
3
2
1
1
3
3
2
2
12
12
3
2
2
2
12
18
12
12
18
12
FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
10.4 FMEA Conclusions
The main outcomes of the FMEA analysis was to highlight the biggest hazards that the
system causes and demonstrate how they are controlled and the risk reduced. The highest
risk priority rating of the original system was 24. This rating generally occurred when
leakage, caused by high temperature exposure or decomposition of the material forced the
failure of the filtration system or distillation system. These hazards can be controlled by
using heat resistant materials (i.e. UPVC piping instead of PVC piping), replacing materials
after a certain period of time, providing maintenance to the vulnerable areas or coating the
materials in exposure resistant paint. These precautions reduced the original risk priority
rating to a maximum of 18 for everything except for the risk of the ceramic filter fracturing.
This specific risk is difficult to control as it mostly happens spontaneously, without warning,
and it is not necessarily dependant on age.
11.0 Conclusions
After extensive research on water purification and treatment methods, a conclusion was
reached on the basis of the criteria which were prescribed. These were:
•
•
•
•
Water purification ability;
Cost effectiveness;
Sustainability and;
Modular design.
Of the potential methods explored; filtration/adsorption, reverse osmosis, solar distillation
and biogas, a solar distiller and filter (with option of biogas addition) were deemed the most
suitable, for the Devikulam community. The primary reason a dual solar distillation and
filtration system was selected over the other water treatment methods was that it did not
have to rely on a reticulated power source and could remove:
•
•
•
Salinity;
Turbidity and;
Bacteria.
Furthermore, this treatment process is also cost-effective as the materials required are
common place and/or can be simply substituted for another material with similar properties
making it also economically acceptable. Additionally, this procedure is environmentally
sustainable as it relies on solar energy, gravity and biogas rather than power from nonrenewable sources. In a basic design form this water treatment system has no moving parts
and is simple to understand, and thus, can be mechanically maintained simply. Community
understanding regarding this process would be of a relatively high level as this type of
method has been used in history (boiling of water) and therefore, the perceptions of it being
beneficial would already exist.
Through a Triple Bottom Line Assessment, the environmental, social and economic impacts
were evaluated and the total life cycle of the system determined. From an environmental
perspective, the energy required for the production of specific components in the treatment
30
FINAL REPORT- WATER PURIFICATION - DEVIKULAM
2011
system was of an elevated level due to the requisite of using hydrocarbons. These elements
included the PVC piping for the filter and the ceramic candle filter. As part of the
environmental division, the resources themselves and their possible impacts were
established. From a resources angle the PVC and copper piping are both non-renewable,
conversely though, both can be recycled. Taken as a whole, this system is environmentally
sound as once it is in operation; there is negligible impact as it is self sustaining.
This water treatment system is completely socially viable as it would be integrated into the
community of Devikulam with ease. The positive influences are that it:
•
•
•
•
Creates employment and builds community ownership;
Respects the established customs of the people and does not impose Western
values, or push capitalist motives upon the community;
Forms an awareness of the health risks associated with water that is contaminated
and;
Produces the opportunity for the community to increase their knowledge base.
As this design has been evaluated as being socially viable, it can be inferred that the
imperativeness of this system will be understood by the people and therefore, they will
actively maintain it to ensure their own well being which is the first step for improved
quality of life.
Finally, it is also essential to appraise the economic viability of the given system to ensure
that it will work in a developing country. The initial outlay is the largest determining factor
to be considered. For this design the cost was at an acceptable level for the work it is to
undertake. Furthermore, there are no operational costs associated with the chosen design’s
energy sources as they are unlimited (being biogas and the sun). Although, there are costs
allied with the filter system including the ceramic candle filter, which has a limited
operational life span in comparison to other components in the system.
12.0 Recommendations
It is recommended that a two part system be installed to meet the demands, and
requirements, of the Devikulam community for treated water. The first part consisting of a
rapid gravity fed sand filter with an addition of a ceramic candle filter and the second part
consisting of a solar distillation unit with the capacity for a biogas heating system to be
attached.
The first part of the system consists of PVC pipe with a diameter of 250mm and a height of
550mm, split into modules so that the sand and ceramic candle filter are separate identities
joined together. It was deemed that 13kg of sand will make up the first section of the first
part of the system which was determined as an acceptable weight, with a total weight of
15kg. The second part of the water treatment system entails a concave mirror of length
4000mm and radius of 500mm with an angle of curvature for the mirror being 180°. The
copper pipe running the length of the concave mirror (4000mm) needs a radius of 14.13mm
(this is a basic component description).
31
FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
Calculations were undertaken to determine the production volume of purified water from
the still using solar energy. To get the required 200L of treated water, 7.8hrs of the day is
needed and the system requires a flow rate of approximately 1L/2.34mins. The approximate
maximum that this system is capable of is 304L of water in 7.8hrs of the day, which would
give Devikulam the ability to produce more water than they would generally require. For
the situation when biogas is used, it was assumed that the biogas will supply the equivalent
energy as the solar radiation or more (supported by the highly exothermic combustion of
methane that makes up a proportion of the biogas). This gives the Devikulam community
the alternative to use biogas when it is necessary.
32
FINAL REPORT- WATER PURIFICATION - DEVIKULAM
13.0
2011
References
APEC Water Systems n.d., Different Water Filtration Methods Explained, viewed 20 March
2011,
<http://www.freedrinkingwater.com/water-education/quality-water-filtrationmethod.htm#Anchor-Ultraviolet-35326>.
APEC,
2011,
Water
Education,
Retrieved
14
March
<http://www.freedrinkingwater.com/water-education/quality-water-filtrationmethod.htm>
2011
Brissaud, F 2006, “Low Technology Systems for Waste Water treatments: perspectives”,
Water Science and Technology, Mexico.
Camco,
2010,
Biogas
Digesters,
viewed
14
<http://igadrhep.energyprojects.net/Links/Profiles/Biogas/Biogas.htm>
May
2011
Cartwright, P.S 2006, “Water Purification”, ASHRAE Journal, vol.41, no. 5, pp. 66.
Engineers Without Borders 2011, “2011 EWB Challenge”, viewed 7 March 2011,
<http://www.ewb.com.au/2011EWBchallenge.htm>.
ITDG,
2008,
Solar
Distillation,
viewed
15
<http://www.itdg.org.pe/fichastecnicas/pdf/solar_distillation.pdf>
April
2011
Jian, L 2009, “Socioeconomic Barriers to Biogas Development”, Human Organisation, vol.68,
iss.4, pp415-430.
Kostoff, R, Rushenberg, R, Solka, J, Wyatt, J 2007, “Technological Forecasting and Social
Change”, vol. 75, issue. 2, pp. 256-275.
Kucera, J 2010, “Reverse Osmosis: Design, Processes and Applications for Engineers”, Wiley,
viewed 6 March 2011, <http://www.wiley.com/Reverseosmosis.html>.
LCA, 2011, LCA Calculator, Retrieved 20 March 2011 <www.lcacalculator.com>
LeChevallier, M. W., & Au, K.-K., 2004, Water Treatment and Pathogen Control: Process
Efficiency in Achieving Safe Drinking Water. London: IWA & WHO.
Lof, GO 1961, ‘Fundamental Problems in Solar Distillation’, Proceedings of the National
Academy of Sciences, vol. 47, no. 8, pp. 1279-90, viewed 20 March 2011,
<http://www.ncbi.nlm.nih.gov/pmc/articles/PMC223133/ >.
McIlvaine, R 2008, “Reverse Osmosis”, Chemical Engineering Journal, vol. 115, no. 8, pp. 20.
MREC, 2006, Anaerobic Digestion and
<http://www.mrec.org/anaerobicdigestion.html>
33
Biogas,
viewed
29
April
2011
FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
Qiblaway, H, Banat, F, 2007, “Solar Thermal Desalination Technologies”, Desalination,
vol.220, iss.1-3, pp.633-644.
Stanford,
2003,
India,
viewed
25
<http://cee45q.stanford.edu/2003/briefing_book/india.html>
April
2011
Suthar, S 2009, “Contaminated drinking water and rural health perspectives in Rajasthem:
an overview of recent case studies”, Springer Science and Business Media, India, viewed 15
March 2011.
ITACA, 2005, An Introduction to Slow Sand Filtration, Retrieved 12 March 2011
<http://itacanet.org/eng/water/Section%206%20Water%20treatment/ssfintro.pdf>
UN, 2010, Statistics, viewed 5 April 2011 <http://www.unwater.org/statistics_san.html>
Wotton, R.S 2002, “Water purification using sand”, Hydrobiologia , vol. 469, no. 1-3, pp.
193-201.
34
FINAL REPORT- WATER PURIFICATION - DEVIKULAM
2011
14.0 Appendix
14.1
Decision Making Matrix
Table 16 Decision Making Matrix
Weighting
0.5
0.2
0.2
0.1
Purification
Cost Effective
Sustainability
Modular
Total
Solar Still
Score
Total
5
2.5
1
0.2
3
0.6
2
0.2
3.5
Parabolic Mirror
Score
Total
5
2.5
2
0.4
4
0.8
4
0.4
4.1
Note: Benchmark is if nothing was implemented to purify the water
Rating Scale (score):
1. Much Worse
2. Worse
3. Same
4. Better
5. Much Better
14.2
Sensitivity Analysis
Table 17 Sensitivity Analysis
Weighting
0.4
0.2
0.3
0.1
Purification
Cost Effective
Sustainability
Modular
Total
14.3
Solar Still
Score
Total
5
2.0
1
0.2
3
0.9
2
0.2
3.3
Parabolic Mirror
Score
Total
5
2.0
2
0.4
4
1.2
4
0.4
4.0
Pairwise Comparison
Table 18 Pairwise Comparison
Purification
Purification
Cost Effective
Sustainability
Modular
0
0
0
Cost
Effective
1
1
0
Sustainability
Modular
1
0
0
1
1
0
-
Note : the design must remain modular as prescribed by project brief.
35
Score
(weight)
3 (0.5)
1 (0.2)
1 (0.2)
0 (0.1)
Scores normalised up to 1
FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
14.4 Life Cycle Analysis of Filter
Figure 11 Sources of Carbon Emissions (LCA, 2011)
Figure 12 Major Impacting Sources (LCA, 2011)
36
FINAL REPORT- WATER PURIFICATION - DEVIKULAM
Table 19 Carbon Emissions Produced through Manufacture and Disposal (LCA, 2011)
37
2011
FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
Table 20 Carbon Emissions Produced through Transport (LCA, 2011)
14.5 Life Cycle Analysis of Still
Figure 13 Sources of Carbon Emissions (LCA, 2011)
Figure 14 Major Impacting Sources (LCA, 2011)
38
FINAL REPORT- WATER PURIFICATION - DEVIKULAM
Table 21 Carbon Emissions Produced through Manufacture and Disposal (LCA, 2011)
39
2011
FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
Table 22 Carbon Emissions Produced through Transport (LCA, 2011)
14.6 The Ceramic Water Filter (Doultonusa,
(D
2011)
Doulton Water Filter Ceramic Candle & Cartridge Technologies, taking the mysteries out of
the drinking water filtration
Ceramics,
cs,
a
natural
water
filter
Sterasyl
micro
micro-filter
Doulton mines only the finest and purest kieselguhr or diatom
earth often described as a silica-like
silica
sediment resulting from
kiesel algae (one celled algae) deposited on the bottom of
geological lakes and
nd lagoons millions of years ago. This is the same
material used in making the finest bone china (like of Royal
Doulton) and numerous other applications.
The filter elements are produced using the latest
ceramic techniques to provide a hollow porous
ceramic
ic which is fired at a temperature in excess of
1000°C. The chemically inert ceramic filter can be stored for eternity
without losing its effectiveness.
Doulton ceramic filter particles from the water but leaves oxygen and
mineral contents unchanged, which gives water it's spring-like
spring
freshness and
taste (not "pure" but wholesome). Pathogens of the most varied diseases
which are reliably filtered from the water include; cholera, typhus,
cryptosporidium, amoebic dysentery, ecoli, colibacillose or bilharzia, anthrax
spores
among
others.
Ceramic filtration technology is often called "dead-end
"dead end filtration” and "depth filtration".
filtration"
40
FINAL REPORT- WATER PURIFICATION - DEVIKULAM
2011
There are several mechanisms by which the ceramic element filters out particles as a deadend filtration.
a) Direct interception or sieving (fig. 1): Particle of 0.5 µm and larger "runs into"
a pore that is smaller than the particle of topmost layer of the ceramic and are
captured as with absolute pore rated
synthetic dead-end membranes.
b) Bridging (fig. 2): Smaller than 0.5
µm particles may be too small to be
intercepted however two particles
hitting the obstruction at the same
time will form a bridge across the
pore adhering to each other. Bridged
particles may not plug the pore creating
even smaller pore gradually forming a
"filter cake". This "cake" creates a finer filtration for subsequent interception at the cost of
decreased flow rate and eventually no flow rate.
Mechanical regeneration of the filter "cake" is simple. The topmost blocked layer can be
removed with stiff brush or nylon scouring pad. This can be repeated many times before
the filter has to be changed.
c) Inertial impaction (fig. 3): Particles flowing through the filter hits
none porous surface barrier it become captured while the water flows
around the barrier. Inertial impaction is more prevalent with smaller
particles in range of 0.1 to 0.4 µm size as these particles are easily
affected by molecular bombardment.
Unlike with synthetic membranes, all of the above methods of capture are dependable
under variable operating conditions e.g. pressure surging, pulsing etc. with Doulton
ceramics.
Ceramic depth filtration will filter out
considerably smaller particles than
equivalent pore size membrane for the
following reasons:
a) Particles intercepted within the ceramic
depth are much smaller than the pores
measured by porometry. This is because
particle laden water has to navigate
through intricate maze of labyrinths. The
path through the filter twists and turns
trough sharp angles due to complicated
41
FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
ceramic structure and so the particles that may have penetrated the topmost layer
become trapped within the structure.
To appreciate the distance and how difficult a path the water has to follow, consider that
the wall thickness of the ceramic is 1000-2000
1
2000 times greater than the pore size of the
ceramic filter and the pores are sharp and jagged rather than smooth and round.
b) Small particles can combine with other particles to form a cluster of particles large
enough to become trapped as a group or individual in dead end
cavities.
c) Weak Van der Waals forces (adsorption fig. 4) attract the small
particles to the ceramic, causing them to be adsorbed onto the wall
of the ceramic. Depth filtration is very dependable as pressure
surges are not affecting
affecting adsorption because the pressure is
stabilized (drops by 50%) on the surface of the ceramic. Doulton
ceramic depth filtration captures particles as small as 0.05 µm with
greater than 90% efficiency.
Given favourable conditions, the accumulated bacteria could
could proliferate and grow unless
prevented by some means.
To prevent this Doulton elements (except the Standard, Ceracarb and Ceramet) are
manufactured with a small amount (about 0.07%) of pure silver (Ag) through-out
through
the porous
ceramic shell. Silver is a recognized bactericide, so when the bacteria comes into contact
with the silver impregnated ceramic, their growth is inhibited. This selfself-sterilizing effect is
known as the bacteriostatic effect.
effect
Silver, a nature's water purifier (I.E. click refresh button to see silver animation)
Free silver ions (Ag+) have
concentrations. They have a
studies describe silver ions
depend
a toxic effect on micro-organisms
micro organisms even in relatively low
highly fungicidal, bactericidal and algaecidel effect. Medical
a catalyst that disable the enzymes that microorganisms
on
to
"breathe".
In the presence of air (oxygen in water), metallic silver forms
silver oxide, which also has a bactericidal effect due to its
adequate solubility. The destruction of viruses, bacteria, moulds,
spores and fungi through contact with silver objects is termed the
spores
oligodynamic effect.
effect. To primitive life forms, oligodynamic silver is
as toxic as the most powerful chemical disinfectants. This,
coupled with its relative harmlessness to animate life (i.e.
mammals), gives oligodynamic silver great potential as a
mammals),
disinfectant.
42
FINAL REPORT- WATER PURIFICATION - DEVIKULAM
2011
The best and most environmentally-friendly silver based disinfectants are capable of
rendering stored water potable for long period of time as in space stations.
The silver leach rate from the Doulton ceramic is very low and always well below the
national recommended limits or equivalent to having a meal using silver cutlery.
Do Doulton ceramic filter removes viruses?
Due to their tiny size viruses theoretically cannot be removed with a 0.2 micron or higher rated
absolute filter (or any mechanical filter for that matter). If virus is a concern simply add a
commercially available disinfectant such as silver (e.g. Katadyn's Micropur®) or iodine tablets.
Doulton Supersterasyl candle will remove the unpleasant taste and odours of the iodine.
Physically viruses have electrical surface charge that attaches them to other larger
particles (free ride). The tight pore-structure of any absolute sub-micron water filter (e.g.
Doulton, Katadyn etc.) can remove "free ride" viruses however due to many variables no
device should be relied upon viral control.
Activated
carbon
as
another
natural
absorber
Doulton uses high quality carbon blends obtained from different raw
materials such as lignite, bituminous coal and
coconut shells. Active carbon is used for water
treatment due to its adsorbing effect with respect to
organic
and
health
endangering chemicals.
Activated
carbon
surfaces
are
both
hydrophobic
and
oleophilic; that is, they
“hate” water but
“love” oil. When flow
conditions
are
suitable, dissolved chemicals in water flowing through the carbon media
“stick” to the carbon surface in a thin film while the water passes on. This
process is call adsorption.
Substances affecting taste and odours such as chlorine,
pesticides (lindane, DDT) and trihalogenmethanes
(THM's) are removed by activated carbon. These
substances are adsorbed on the large surface area of the
active carbon. For visual purpose, one teaspoon of
activated carbon have a surface area the size of a
football field.
Active carbon is available in granulate (GAC filters),
powder (PAC filters) or extruded solid carbon block form
43
FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
(CB filters).
14.7 Doulton Ceramic Candles and Cartridge Grades
Sterasyl membrane: (candle and cartridge form): Used for microbiological removal. The
only ceramic element in the world to meet the stringent NSF antimony and arsenic
extraction test featuring:
•
•
•
•
•
•
>99.99% E.coli removal
Tested with live Cryptosporidium cyst to 100% removal far exceeding EPA three log
cyst reduction requirements
100% efficiency at 0.9 µm absolute (0.5 µm absolute ANSI standard)
> 98% efficiency at 0.2 µm
> 90% efficiency at 0.05 µm
< 0.07 NTU turbidity reduction
Typical application: UV, RO and ozone pre-filter, point-of-use (POU) final polish filter, zero
cyst tolerance in bottling water plants using our industrial multi cartridge filters and
various other application requiring absolute filtration. Least expensive absolute filter on
the market as it is cleanable and reusable for up 60 times. Backwash capable, selfsterilized, no bacteria grow through as encountered in most all synthetic membranes.
Available in candle and open both ends (DOE) cartridge style.
Supersterasyl candle: Used in British Berkefeld gravity filters is a Sterasyl shell packed with
granular activated carbon. Available in 2"x7", 2.75"x7" and 2"x10" candle style with long
threaded end cap. Custom size and end caps configuration available with minimum kiln
firing requirements of 2400 units for all grades of elements.
Carbosyl elements: Sterasyl shell lined with fine activated carbon coating impregnated
throughout the ceramic pore structure then re-fired in excess of 1000°C. Soon to introduce
our inline filter fitted with Carbosyl candle as a replacement for the RO GAC final polish
filter to control heterotrophic plate count (HPC)* bacteria commonly found in virtually all
inexpensive RO systems. Available in 2" slimline and 2.75"x9.75" Imperial cartridge in case
quantity by special order. 25 pcs. slimline and 9 pcs. per case Imperial size.
•
•
Reduces HPC to meet TUV and Alpha Institute requirements. Test results of Carbosyl
vs. RO GAC post filter>>
Meets stringent European Union (EEC) stagnation requirements
Supercarb ceramic elements: Used in all residential pressure filters is a Sterasyl shell with
solid carbon block insert. Economical three stage filtration available in candle and cartridge
style.
Ultracarb ceramic elements: Used in all pressure filters is a Supercarb with ATS ion
exchange medium incorporated into the carbon block for heavy metal reduction.
Economical four stage filtration available in candle and cartridge style.
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FINAL REPORT- WATER PURIFICATION - DEVIKULAM
2011
Conclusion: Doulton ceramic filters are designed to convert raw water into high quality
drinking water that will comply with the most stringent potable water standards all 100%
naturally.
* Heterotrophic (HPC) is a harmless bacteria commonly found in all waters. In absence of
disinfectants this bacteria colonize the reverse osmosis holding tank. As the bacteria die it
creates foul odor therefore all RO's have GAC final filter to remove the odor out of the
water. It should be clearly understood that no GAC filter remove any bacteria.
Calculations for Final Design
•
Assumptions:
An overall system efficiency of 80%, filters are not clogged and are flowing at their
maximum rate:
•
Calculations based on the following information:
These rapid sand filters use coarser sand than slow sand filters and the effective size of the
filter media is usually greater than 0.55 mm. The flow rates are normally between 4 and 21
m/h equating to 400 to 2100 l/h per m2 of filter. These filters do not remove disease
causing entities as efficiently as slow sand filters and usually need a post filtration
chlorination process. Flocculation and coagulation are sometimes used as pre-treatments.
•
Calculations:
Each unit needs to produce 200L of water per day, so assuming 20% loss of water through
the solar still. The filter system must output an amount of water equal to:
Feedwater = 200 x 1.2 (80% efficient)
Feedwater = 240L
The solar still needs a minimum of 240L of feedwater. Therefore the water filter system
must output 240L, the minimum feedwater into the water filter system is calculated by:
Feedwater = 240 x 1.2 (80% efficient)
Feedwater = 290L
290L = 0.29m3 of feedwater.
Assuming only 7 hrs of operation for the water filter unit. (The unit is able to operate 24hrs
if required)
0.29m3 = 0.0414m3/hr
7hrs
So minimum required output = 0.0414m3/hr (Rapid filter minimum requirement =
5m3/hr/m2)
Therefore
45
0.0414 x 5 = 0.207 m3/h/m2
FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
=ට
଴.ଶ଴଻
గ
= Pipe Diameter
= 0.25m
Standard size 250mm pipe diameter.
A pipe diameter of 250mm is required to meet the minimum water requirement of 200L per
day. The rate of flow through the sand filter is related to the surface area of sand, not the
volume of sand, it is recommended that the sand be filled to 150mm height in the filter
system.
Manufacturer specifications place the ceramic candle filter at a flow rate of 2L/min this is
equal to 120 L/hr.
m3/hr =
ଵଶ଴ ௟/௛௥
ଵ଴଴଴
1 m3 = 1000L
= 0.12m3/hr
The ceramic filter flows faster according to manufacturer specifications then the rapid type
sand filter therefore the restrictions placed on the system will come from the sand filter
system.
Weight of the filter unit:
Using a pipe diameter of 250mm (.25m) and a sand depth in the unit of 150mm (0.15m)
Assuming that sand has an average weight of 1800 kg/m3
So volume of sand in the unit (m3):
= 0.00736 m3
So weight of sand in the unit (kg):
= ሺߨ‫ ݎ‬ଶ ሻ x H
= ሺߨ0.125ଶ ሻ x 0.15
= 0.00736 × 1800
= 13.2 kg
The overall weight of the system will be approx 18kg (±0.1 kg). Breakdown as follows:
Pipe and lids – 3 kg
Ceramic Filter – 1kg
Sand Filter Unit – 13.2kg
Miscellaneous – .7kg
14.8 Solar Still System
How a simple solar still operates
The incident solar radiation is transmitted and is absorbed as heat by a surface in contact
with the water to be distilled. The water is heated and gives off water vapour. The vapour
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FINAL REPORT- WATER PURIFICATION - DEVIKULAM
2011
condenses on a surface which is at a lower temperature because it is in contact with the
ambient air, and runs down into a gutter from where it is fed to a storage tank.
Design objectives for an efficient solar still
For high efficiency the solar still should maintain:
• a high feed water temperature
• a large temperature difference between feed water and condensing surface
• low vapour leakage.
A high feed water temperature can be achieved if:
• a high proportion of incoming radiation is absorbed by the feed water as heat. Hence low
absorption glazing and a good radiation absorbing surface are required
• heat losses from the floor and walls are kept low
• the water is shallow so there is not so much to heat.
A large temperature difference can be achieved if:
• the condensing surface absorbs little or none of the incoming radiation
• condensing water dissipates heat which must be removed rapidly from the condensing
surface by, for example, a second flow of water or air, or by condensing at night.
(ITDG, 2008)
Calculations for Final Design
•
Copper Piping
r1 = 0.0130175m
r2 = 0.0142575m
2
Volume of pipe = πr h
= π (0.0130175)2.4
= 0.0021294382m3
= 2.1294382 L
= 2129.4382cm3
Density of copper = 8.94g/cm3
Mass of pipe = volume of copper . density
= (πr2 2h – πr1 2h) . 8.94
= ((π(0.0142575)2 . 4) – (π (0.0130175)2.4)) . 8.94
= 425.0072205 cm3 . 8.94 cm3/g
= 3799.564552 g
•
Mirror
r = 0.5m
length = 4m
Mirror = ½ cylinder
Surface area of mirror = ½ surface area of cylinder
= (2πr2 + 2πrh)/2
= 7.068583471m2
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length = 4m
FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
Solar energy for India = 5760 – 7920 MJ/m2/year
Average
=6840MJ/m2/year
Solar energy per day =18.7269MJ/m2/day
Efficiency of mirror
= 0.95
Mirror reflection in one day
= solar energy . surface area . efficiency
= 18.7269 . 7.06858 . 0.95
= 125.754MJ/day reflected on to pipe
Copper absorbs 0.64 of radiation on surface
Radiation absorbs through copper
= reflection . efficiency
= 125.754 . 0.64
= 80.48253MJ/day is absorbed
Using specific heat to find ΔT of the copper pipe due to absorbed radiation:
Q = 80 482 530 J
C = 0.385
M = 3799.564552 g
Specific heat = Q
= cmΔT
= ΔT = Q/cm
= 80 482 530J / 0.385 . 3799.564552
= 55018.31094
Using conduction to find the heat transfer to the water:
k = 385
A = 6.41x10-4
ΔT =55018.31094
d=4
Conduction
= Q/t = kAΔT/d
= 385 . 6.41x10-4 . 55018.31094 / 4
= 3394.423 J/s is transferred to the water in the pipe
• Water
Need 200L of water through the system per day = 200L/day
An average day (sunlight) in India = 7.8 hours
Rate of water flow out of system
= 200L/7.8hours
= 25.64L/hr
= 25.64L/3600s
= 1L/140.4s
= 1L/2.34mins
Volume of water held within pipe = 2.129L
Time water spends in pipe
= volume of pipe . flow rate out of pipe
= 2.129 . 140.4
= 298.9116s
Using specific heat to find how much energy is needed to evaporate 1L of water:
c = 4.186
ΔT (assume min 25°C, max 100°C) = 75
m = 1L . 1L/kg = 1kg = 1000g
Q = cmΔT = 4.186 . 75 . 1000 = 313 950 J
The 1L of water spend 298.9116s in the pipe
There is 3394.423 J/s transferred to the water
Amount of energy transferred to 1L during time in pipe = Q/t . day(7.8hours = 28080s)
= 3394.423 . 298.9116
= 1 014 840.967 J/L
Using specific heat to find how much energy is needed to evaporate 200L of water:
c = 4.186
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FINAL REPORT- WATER PURIFICATION - DEVIKULAM
2011
ΔT (assume min 25°C, max 100°C) = 75
m = 200L . 1L/kg = 200kg = 200 000g
Q = cmΔT = 4.186 . 75 . 200, 000 = 62 790 000 J
There is 3394.423 J/s transferred to the water
Amount of energy transferred to 1L during time in pipe = Q/t . day(7.8hours = 28080s)
= 3394.423 . 28080
= 95 315 397.84J
The energy transferred to the water in the time it is in the pipe exceeds the energy needed,
therefore it is feasible. This also allows for error and inefficiencies.
It gives excess energy of +32 525 397.84J
If there were no inefficiencies then all the energy may be used to create a higher output of water.
Amount of energy transferred in a day (7.8 hours = 28 080s)
= Q/t . time in day
= 3394.423 . 28 080
= 95 315 397.84 J
1L of water needs 313 950J to evaporate it.
Using this to find how many litres could be produced = energy produced in one day / energy
needed for one litre
= 95 315 397.84/313 950
= 303.6L
Max flow rate
= L/t
= 303.6/28 080
= 1L/92.49s
= 1L/1.54mins
Therefore it may be possible for the village to produce more than the allocated 200L of water per
day.
•
Biogas/Biodigester
Table 23 Biodigester Relationship (Camco, 2010)
Size of Family
6
8
Cows
6
9
Digester (m3)
8.4
10.8
Gas Storage (m3)
1.44
1.92
The biogas produced is approximately 50% methane, with the other 50% mostly comprising
of carbon dioxide.
Using the above table there is a relationship formed between the digester and the gas
storage:
Gas storage = g
Digester
=d
Constant
=k
g/d
=k
1.44/8.4
= 0.171
1.92/10.8
= 0.177
Therefore k is approximately equal to 0.17
d .k = g
Using the above table there is a relationship formed between the digester and the number
of cows needed to produce the waste:
Digester
=d
Cows
=c
Constant
=x
d/c
=x
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FINAL REPORT- WATER PURIFICATION - DEVIKULAM 2011
8.4/6
=1.4
10.8/9
= 1.2
Therefore k is approximately equal to 1.3
d = c.x
The combustion enthalpy of methane is as below:
CH4 + O2 → CO2 + H2O
ΔH = -891kJ/mol
It is known that 62 790kJ is needed to evaporate 200L of water from earlier calculations
Moles of methane needed to be combusted to evaporate water = 62790kJ / 891kJ/mol
= 69.8 moles of methane
Molar mass of methane
= 12 + 4 . 1
= 16 g/mol
Mass of methane needed to evaporate 200L of water
= n . MM
= 69.8 . 16
= 1116.77g
3
Density of methane = 0.668kg/m
= 668 g/m3
Volume of methane needed = mass / density
= 1116.77/668
= 1.67m3
Note that only 50% of biogas is methane. Assume other 50% is carbon dioxide
If there is 69.8 moles of methane in the gas storage tank, then there must also be 69.8
moles of carbon dioxide due to the 50:50 ratio.
Molar mass of carbon dioxide
=12 + 16 . 2
= 44g/mol
Mass of carbon dioxide resulting
= n . MM
= 69.8 . 44
= 3071.2g
Density of carbon dioxide
= 1.8 kg/m3
= 1800g/m3
Volume of carbon dioxide
= mass/density
= 3071.2 / 1800
= 1.7m3
Total volume of gases
= 1.67 + 1.7
= 3.4 m3
The size of the digester
=g/k
= 3.4 / 0.17
= 20 m3
Number of cows needed to produce sufficient bio waste = d / x
= 20 / 1.3
= 15.38
= 15 cows
50