Technology and Development Supervised Learning (TDSL)

Autumn 2014

“Preliminary study on potable water solutions for the rural poor”

ABHISHEK AGGARWAL

1st December, 2014

Objective

1. Literature Review:

• Types of Water contamination

• Standards

• Basic Treatment Processes

2. Field Visits: - Ground reality of water quality/availability problem in under-

developed sections of India

3. Market Solutions

Literature Review

Water Contamination

Potable water - doesn’t cause any acute or chronic health effects like diarrhoea, typhoid, intestinal

worms, cancer etc.

Water contamination classified in two types of impurities:

1. Biological contamination: certain species of Bacteria (e.g. cholera, typhoid ), Virus (e.g. hepatitis A, rotavirus),

Protozoa and Helminths (Intestinal Parasites).

2. Chemical contamination: further divided into two categories:

(i) Volatile impurities:-

• Have boiling point close to water or less than it. These impurities evaporate along with the

water.

• Generally organic like benzene, toulene etc.

(ii) Non-volatile impurities:-

• Other impurities might be considered non-volatile with respect to water.

• e.g sodium, calcium , iron, magnese, fluoride, nitrate, lead, arsenic, chlorine, feritlizers,

pesticides etc.

Standards – determine the concn acceptable in water

Fig :Helminths

Pollutants

Visible symptoms of the water contaminants: 1. Arsenic: skin problems

2. Bacteria/Virus/Protozoa/Cryptosporidium: gastrointestinal problems

3. Barium: Difficulty in breathing, changes in heart rhythm, stomach irritation, brain swelling, muscle weakness

4. Chromium: Nausea, gastrointestinal distress, stomach ulcers, skin ulcers, allergic reactions, reproductive

problems, lung and nasal cancer

5. Copper: nausea, vomiting, diarrhea, gastrointestinal illness, abdominal and muscle pain.

6. Fluoride: discoloration/disfiguration/pitting of teeth in children & pain, tenderness, hardness and abnormal

fragility of the bones

7. Nitrite/Nitrate: Blue-baby syndrome seen under 6 months baby

8. Mercury: vision, hearing, memory problems

9. Selenium: Hair and fingernail changes, fatigue and irritability

10. Silver: Skin discolouration

11. Chlorine: Birth defects, heart disease

12. Chloramines: nose irritation, stomach discomfort

13. Lead: mental retardation

14. Cadmium: cause breast cancer

Source: http://www.thewaterexchange.net; http://www.wqa.org/Whats-in-Your-Water

Standards ● No universally recognized and accepted standards.

● May differ by 10 times the other standards.

● Standards are legally enforced in few countries like U.S , Europe

● India – standards are mere guidelines

- At Central Level : many department of Central Government publish their own guidelines like:

• Bureau Of India (BIS) : IS 10500 (2012) – updated in 2012

- Ministry of Drinking Water and Sanitation (MDWS) follow these guidelines

• Central Pollution Control Board (CPCB)

• Central Public Health and Environmental Engg. Organisation (CPHEOO), Ministry of Urban

Development

- Even many states in India have their own guidelines e.g Himachal Pradesh , West Bengal (WBPHED)

Parameter/Organisation W H O E u r o p e U S C h i n a I n d i a

A r s e n i c 10μg/l 10 μg/l 10μg/l 50μg/l 50μg/l

B o r o n 2.4mg/l 1.0 mg/L -- -- 1.0mg/L

C a d m i u m 3 μg/l 5 μg/l 5 μg/l 5 μg/l 3 μg/l

C h r o m i u m 50μg/l 50 μg/l 100 μg/L 50 μg/l 50 μg/l

C o p p e r 2.0 mg/l 2.0 mg/l -- 1 mg/l 1.5 mg/l

C y a n i d e -- 50 μg/l 200 μg/L 50 μg/l 50 μg/l

F l u o r i d e 1.5 mg/l 1.5 mg/l 4 mg/l 1 mg/l 1.5 mg/l

L e a d 10 μg/l 10 μg/l 15 μg/l 10 μg/l 10 μg/l

M e r c u r y 6 μg/l 1 μg/l 2 μg/l 0.05 μg/l 1 μg/l

N i t r a t e 50 mg/l 50 mg/l 10 mg/L (as N) 10 mg/L (as N) 45 mg/l

S e l e n i u m 40 μg/l 10 μg/l 50 μg/l 10 μg/l 10 μg/l

*Reference : http://en.wikipedia.org/wiki/Drinking_water_quality_standards ; http://www.wbphed.gov.in/main/Static_pages/cphed.php ;

http://www.who.int/water_sanitation_health/publications/2011/9789241548151_annex.pdf?ua=1

All the parameters are not included. This is just to show the comparison b/w different guidelines.

Comparison of some of the existing guidelines :

Basic Treatment Processes

Some of the most common methods

1. Boiling

2. Activated Carbon

3. Distillation

4. Reverse Osmosis (RO)

5. Kinetic Degradation Fluxion (KDF) Process Media

6. UV Radiation

7. Chlorination

Boiling :

Process: Keep water at its boiling temperature for 15-20 minutes.

Effect: Kills micro-organisms such as bacteria, virus or parasites and removes some

VOCs

Disadvantages: • Cloudy or highly turbid water must be filtered (can use cloth)

• Boiling may concentrate the contaminants

• Should not be used when toxic metals, chemicals or nitrates are present, since it

increase their concentrations

Activated Carbon:

Form of carbon which is treated with oxygen to make it porous.

Types of carbon filters:

i. Granulated Activated Carbon (GAC) and

ii. Solid Block Activated Carbon (SBAC)

Process:

Adsorption of impurities via electrostatic interaction or chemisorptions.

Note:- Porosity increase the surface area for contact

Effect:

Removes microorganisms and organic chemicals, especially

pesticides, THMs (chlorine by-product), trichloroethylene (TCE), and PCBs

Disadvantages:

• Become breeding grounds for the bacteria they trap

So, run water through it for a few minutes before use

• Hot water damage carbon filter and releases trapped contaminants into the water

• Doesn't affect heavy metals like lead, mercury, arsenic (unless specially designed to), cadmium, total

dissolved solids, hardness(i.e. calcium, magnesium, potassium), nitrates, sulfides, and fluoride

Distillation:

Process:

Steam from boiling water is condensed.

Effect:

Kills pathogens, remove salts that carbon filtration cannot remove, like

heavy metals, nitrates, chlorides. Used rarely when a large amount of

minerals or impurities are to be removed.

Disadvantages:

• VOCs(like pesticides) are not removed ,a post-filter like granular carbon filter is used

• Distilled water highly prone to recontamination or bacterial growth.

• Distilled water have leaching effect i.e. high tendency to absorb substabces.

- Addition of mineral supplements are recommended

• Absorbs atmospheric carbon dioxide forming carbonic acid.

- Distilled water should be stored in closed container preferably glass due to acidic nature

• Maintenance is expensive and is required periodically

Reverse Osmosis (RO):

RO and activated carbon filter - most efficient treatment

Process:

1. Water through a semi- permeable membrane by applied hydraulic pressure which counteracts the

osmotic pressure.

2. Membrane rejects the contaminants that are too large to pass through the tiny pores in the membrane.

Effect:

Removes microbes, total dissolved solids (TDS), asbestos, lead, chloride, fluoride, nitrates and other toxic

heavy metals, radioactive substances (like radium).

Disadvantages:

• Organic compounds and some of pesticides, solvents and VOCs are not completely removed.

-- Post-filter like AC recommended

• RO water is essentially mineral-free

-- Mineral supplements are recommended

• Membrane deterioration occur due to the bacteria (like coliform)

-- A pre-filter is also suggested.

Kinetic Degradation Fluxion (KDF) Process Media: • Alloy of copper and zinc.

• Life of more than 6 years

• Recyclable

Process:

It utilizes the principle of Redox reaction. The KDF creates electrolytic cell with zinc anode, copper

cathode and impure water as electrolyte.

o Metals are attracted to the KDF particles and adhere with them.

o Non-metallic impurities react with the KDF forming oxides, hydroxides, sulfates and even

ozone. Ozone as a by-product forms hostile and desolate environment for micro-organism like

algae, bacteria.

-- These by-products are not dangerous.

Effect:

KDF is known to kill algae and fungi, control bacterial growth, and remove chlorine, pesticides,

organic matter, rust, unpleasant taste and odour, hydrogen sulphide, nickel, chromium, cadmium,

calcium, aluminium, mercury, arsenic, and other organic impurities.

Ultra-Violet (UV) Radiation:

Process:

UV radiation (~ 250nm wavelength) alters the DNA of

micro-organisms, disrupting their growth and reproduction.

Effect:

Kills or render pathogens harmless.

Note: -

• UV lamp effectiveness : Exposure time and lamp intensity

• Turbulent water flow more effective

Disadvantages:

• Lamp requires replacement in a year, since its intensity decreases with use

• Turbid, colored or high concentration of coliform in water, UV not effective

-- Thus, UV is generally used in the last stage of a treatment process.

Source: Article by Cornell Cooperative Extension, College of Human Ecology on Ultraviolet Radiation for Disinfecting Household Drinking Water

(http://waterquality.cce.cornell.edu/publications/CCEWQ-10-UVWaterTrtforDisinfection.pdf )

Chlorination:

1. Cheapest method

2. Has residual effect - prevents re-contamination during transportation

Process:

In water chlorine stays in equilibrium as:

Cl2 + H2O ↔ HOCl + HCl …………… (1)

HOCl ↔ H+ + OCl- …………… (2)

Chlorine and HOCl are neutrally charged -> penetrates the outer membrane of pathogens.

are good oxidizing agents -> react with the enzymes and proteins inside the

cell disrupting their growth and reproduction.

Effect:

Kills or render pathogens harmless.

Note: - Disinfection effect drops with increase in pH since, the equilibrium (2) shifts to the

right side i.e. decreasing the concentration of HOCl

Disadvantages:

• The presence of organic materials (e.g. urine, sweat, hair and skin particles) combines with free chlorine resulting in the production

of carcinogenic Trihalomethanes (THMs).

The WHO has stated that the "risks to health from these by-products are extremely small in comparison with the

risks associated with inadequate disinfection”

• Helminthes insensitive to chlorination.

• Bitter taste and unusual smell of chlorine in water

• Chlorine evaporates due to volatile nature, thus, chlorine needs to be regularly added to prevent biological recontamination

Parameter/

Technology

KDF Activated Carbon RO UV Chlorination Distillation

Electricity/Heating X X ✓ ✓ X ✓

Expensive X X X X X ✓

Life >6 years ≈ 1year (dependig

on amount of

impurities)

≈ 1year (Annual

filter change)

≈ 1year (Annual

bulb change)

- No drop in quality

with time

Recyclable Technology ✓ ✓ - X X -

Taste of water after

processing (✓)Removes

odour and taste

(✓) (✓) Close to Spring

water

(X) - No change (X) (Introduces

bitter taste)

(✓) (Flat taste)

Biological

Contamination(1)

X X X (not

recommended)

✓ ✓ ✓

Volatile Organic

Contaminants (VOCs) X ✓ X - X X

Residual Disinfecting

Effects ✓ X (used at POS,no

storage req. )

X X ✓ X

Non-Volatile Chemical

Contaminants ✓ X ✓ X X ✓

Hazardous By-products X X X X ✓(Tri-Halo Methanes THMs

and haloacetic acids HAAs)

X

* Every location needs to be studied case by case instead of assuming the water treatment that works in one area will work in another.

Note(1): Many germs can no longer be detected in very low concentrations. In these cases, it is not possible to provide scientific proof of a 100%

reduction.

Summarization:

Field Visits 1. Kashivali Village

2. Velpada Village

3. Vikramgarh High School (Livinguard set-up) 4. Thapapada Village

5. JJ Colony, Sawda Village near New Delhi /

"Hub and Spoke" model of Sarvajal 6. Astitva NGO in Wada – Construction of Bio-Sand filter

Kashivali Village Population: 477 ; Households: 70

• Houses on land owned by a farmer -- given permission to live but no construction

• Electricity supply & meters installed -- mostly used in night for dinner.

• Monsoon time: man & female work on farms -- able to produce enough to feed themselves.

• Other times - Men leave the village for months for work ,

some “babus” recruit from the village itself.

- Females stay back -- collect (i) firewood before the monsoons

(ii)water,

takes their entire day

• Wheat grinding – takes entire day

-- no place in village, travel outside.

-- Spend a lot on transportation (Rs. 20 for round trip and Rs. 2/kg wheat grinding).

• Education -- 1st to 8th class School nearby

-- Built this year by Astitva

-- 10 teachers & 8 staff members

-- Books : collected through Donation throughout India,

given free or at small fee (Rs 10-20) to children

• Diseases -- Stomach problems, typhoid (during Monsoons)

-- Pain in Bones & teeth (throughout year )

Astitva foundation -- “Rainwater Harvesting” project started in 2010: - Build pipeline system to villages

tend all technological needs -- motor size, diameter of pipe, storage tank size etc.

provide construction material -- pipe, storage tank, motor etc free of cost.

labour work by village people till now completed 6 such pipelines, at a cost of 2-3 lakhs each, for populations around 500 or more.

Water Condition in village:

• 2 non-perennial wells around 150-200m

• One has holes in lining, so water no longer potable.

• Other well – in good shape. Used for drinking purposes, runs dry in February.

• As level depletes -> women wait in line to get water. If late to collect water than have to travel 5 km to

village, Valvandi (has a perennial well). Valavandi people think this will perish their water supply, so resist

them from taking water from their well.

• Astitva built a pipeline this year(2014) under its “Rainwater Harvesting” project -- used when wells dry up

-- about 1.5 km long and dug 1.5ft in ground

-- 10x15x15 ft well was dug 1.5km away

-- Water pumped by motor and stored in 5000L Plastic storage tank

-- Completed in 15-20 days.

-- Electricity bill for motor is shared (approx 1500 Rs/month)

• Water Decontamination: Villagers don’t have much knowledge

-- Only add TCL tablets in well provided by Gram Panchayat every 2-3 days.

-- Draw water from well -> Use a sieve to remove visible impurities

Velpada Village Population: 557 ; Households: 67

• Electricity supply

• Solar lamp at centre of village – only source of light in night

• Men don’t migrate much – go for not more than 15-20 days

• Education: -- Have 25 graduates in the village.

-- Don’t discriminate much between male and female, send kids to school

-- School till class 4th and Anganwadi in village

-- For high school go to Vikramgarh 1.5km away & for BA/MA travel to Wada 12kms away

• Diseases: Diarrhoea (Monsoons) & Stomach problem, pain in hands & feets ( throughout)

Water Condition: • 1 non-perennial well -- 500m away

• Water Shortage starts from February

-> Drinking water : well in village Rhati Pada (about 2-3 kms)

-> Water for Other Purposes: a perennial water channel (1.5-2km)

• Astitva built a pipeline in April, 2012 --

-- 2 km long and dug 1.5ft in the ground.

-- Water source : well in Rhati Pada

-- Pumped water is stored in a 5000L Plastic storage tank.

-- Completed in 20 days

• Water Decontamination: They also just add TCL tablets provided by the Gram Panchayat.

Vikramgarh High School (Livinguard set-up)

• School has around 2200 students

• Number increases to 3200 during examinations

• Livinguard Technologies Pvt. Ltd. Installed water treatment set-up January, 2014

-- Redesigned in August due to highly turbid water -- Company developed a candle known as Livinguard candle

-- Candle pierces membrane of microorganisms that come in contact

-- Disinfection achieved via Mechanical kill action opposed to conventional Chemical ones

• Set-up in School:

-- Water comes from local overhead Water tank : has high turbidity, coffee coloured.

-- Before storing water in 1500L overhead tank, passed through a Primary filter (decreases turbidity)

-- Then passed through sand filter -> then carbon candle -> then through 2 other filters (to be sure of no

TDS) -> finally through Livinguard Candle and later stored in 2500L tank

-- At start of day -> Using Backwash process sand filter, carbon and Livinguard candle are cleaned

takes about 10 minutes.

“Attendance Drastically Increased”

Thapapada Village Households: 30

• Adjacent to village is a large agricultural land owned by big farmer.

• Astitva started a Balwadi here Care of 17 kids of about 2-5years is taken in it.

• Diseases: Stomach ache and fever

Water Condition:

• A water stream nearby

• 2 non-perennial wells

-- One not dug quite deep (very close) used mostly for activities like washing clothes

-- Other one right in middle of village quite a big well, dries around start of Feb

had green colored water at the time

• Astitva helped digging a perennial well next to water stream

-- Well connected by a pipeline to tank in the village

-- water had a brownish colour: due to rains sand become loose

So, for drinking purpose they were avoiding this water

• A private school is constructing a big water system for itself

-- Have agreed to provide water to village

• Water Decontamination:

-- They also just add TCL tablets provided by the Gram Panchayat.

-- But during monsoons first boil the water and then use cloth for filtering it

Water Sample Testing using a Jal-Tara kit

Sample 1 Water from the well in Kashivali used for drinking

Sample 2 Water from Plastic Storage tank constructed as part of Astitva Rainwater Harvesting project in

Velapada

Sample 3Water from the storage tank before treatment through Livinguard set-up in Vikramgarh High School

Sample 4 Water after treatment through Livinguard set-up in Vikramgarh High School

Sample 5Water from Plastic Storage tank constructed as part of Astitva Rainwater Harvesting project in

Thapapada

Sample 6Water from the well not used for drinking in Thapapada

Sample 7 Water from the well situated right in the middle of the village of Thapapada which is used for drinking

purpose by the villagers

Test/Sample Acceptable

limit(1) 1 2 3 4 5 6 7 Bacterial

Contamination No Yes Yes Yes No Yes Yes Yes

pH(2) 6.5-8.5 6 7 6 6 6 6 6

Turbidity (NTU) 5-10 <10 <10 <10 <10 ≈50 ≈25 ≈25

Residual Chlorine

(mg/L)(3)

0.2 (min) Absent (∵ there was no change in colour)

Chloride (mg/L)(4) 250-1000 1418 1467.63 638.1 666.46 709 1205.3 1666.15*

Fluoride 1-1.5 (max) 0.6 mg/L (∵ all showed the same colour)

Hardness (mg/L) 300-600 120 200 144 144 136 144 200

Ammonia (mg/L) 1.5 0.6 mg/L (∵ all showed the same colour)

JJ Colony, Sawda Village near New Delhi /

"Hub and Spoke" model of Sarvajal Households: 8000-9000

• No pipeline laid

• Delhi Jal Board supplies water free of cost in water tankers but not potable water

-- Appear to cause skin irritation and gastronomical problems

• 60-70% people have motors at their homes

• 2% households even have installed Kent ROs

“Hub and Spoke” model Water Treatment Plant (WTP)

• In area of 100-150 sq.ft

• Ground water in underground 10,000L tank for sedimentation then pumped into a 1,000L tank.

• Subjected to pre-filtration passed through RO membrane UV • Purified water stored water in two 3000L storage tanks

not more than 76hrs

• Observed : TDS of raw water around 1500 mg/l and

-- after Purification around 100-130mg/l

• Clean after 6hrs of use takes about 15min for backwashing and

further 10mins for the rinsing.

Water Kiosks

• 13 kiosks like an ATM in radius of 300-500m

• 1000 people have cards

• Store about 500L of water

• Recharged using a CNG operated recharging vehicle carry about 800L of water

• All kiosks are connected to server using cloud computing monitoring water level

• Whenever water level falls below a level, SMS is sent to people at WTP

Cost

• Electricity bill 10,000 Rs/month.

• Pay each of 2 employees 8,000 Rs/month

• Transportation cost 3,000 Rupees/month

• Cost of each kiosk is Rs 40,000.

Tentative figure, unable to

confirm with organisation

Market Solutions/Case Studies

Solutions studied earlier 1) Jaldoot: -

• Three wheeled rickshaw fitted with multi stage water filtration unit.

Collect water from source – well, water stream etc. Purify it sells it house to house

• Water stored in 500 L stainless steel container mounted on vehicle

• Removes microbiological contamination, sediments, organic compounds, taste and odor

Doesn’t remove contaminants like fluoride, arsenic.

• CTC : 50p/L (depends on dealer) ; Vehicle cost: 5.5 lakhs

• Flow rate – 1430 mL/min

2) Aquakraft: - • Has a water vending machine just outside the WTP

• Contaminants removed are arsenic, fluoride, iron, silica, lead and microbiological.

• CTC : 50p/L ; Initial cost: 3.5 + lakhs

• Flow rate – 1500 mL/min

• Operated from –9:00 –12:00 in morning and 4:30 –7:00 in evening

3) Jaltara: - • Uses BARC UF technology

• removes contaminants like microbiological, organic, turbidity

• CTC :- 500 Rs for new candle set and 250 for replacement

• Flow rate – 83mL/min (very slow)

Livinguard Technologies Pvt. Ltd. http://www.livinguard.com/

Block No C-96, 1st Floor, TTC Industrial Area, Turbhe MIDC, Navi Mumbai 400705

+9122-30212509

info@livinguard.com

● Uses a proprietary disinfecting coating material called Livinguard:

o Impregnated on entire area of fabric.

o Coating forms tiny knives which pierce membranes of microorganisms

o Doesn’t require Electricity, thus, Cost-Effective process

● Cost to Consumers: 2-6 paise/L

● Using the Livinguard filtering technology, they have developed a huge line of at different scales.

o Livinguard "Matka" Filter

o Livinguard Community Filter: Saw in visit to Vikramgarh School

o Livinguard Rural Filter (33 Liter Capacity) MRP 1600 Rs/piece

-- Requires filter to be replaced every year

-- Presently distributing for free

-- Not a suitable solution, since :

a) Expensive

b) Yearly Maintainance cost

c) Just remove Biological Contamination

Sarvajal http://www.sarvajal.com/#

Piramal Water Private Limited, Chandan Bunglow, Opp Paritosh Tower, Near Darpana Academy, Usmanpura, Ahmedabad, Gujarat - 380

013 India

Email - info@sarvajal.com

Office - 079 4050 2100

Toll Free - 1800 103 2334

● Product: Water ATM’s and Filtration plants o Solar powered

o Cloud based remote monitoring system

● Cost to consumer: Rs 0.30 per litre at ATMs away from filtration centre and

Rs 0.15 per litre at the filtration centre

● Water undergoes :

o reverse osmosis

o Ultra-violet treatment

o Do not use Ozonisation process : quite expensive

● Claims water quality maintained according to BIS guidelines

● One of the first model in India to combine Technology for potable water solutions for the poor .

Amazing and Working business model but have pre-requisites:

a) The location must have atleast 3,000-4,000 users to recover the initial cost & cost of

production

b) An ample source of Raw water

BioSand Filter(Developed by CAWST* co-founder Dr. David Manz in 90’s)

Principle: Based on slow-sand filter ● POU water treatment system

● Pathogens and suspended solids are removed by

Mechanical trapping in sand,

Predation -- Micro-organisms in bio-layer eat them,

Adsorption -- Stuck to sand grains,

Natural death -- lack of food,air

● Rate of filtration of water : 12-18 L/hr (for approx ½ x ½ square feet area)

-- Depends on the Cross-section area, since the target is to get 0.4 m3/m2/hr ● Removes up to 95% of turbidity, bad odor & taste,

Up to 100% of helminths, protozoa, 98.5% of bacteria & 70-99% of viruses

Also removes Iron and magnesium

Restrictions/Requirements:

● Chlorinated water should not be used since chlorine kills the biolayer

Disadvantages:

● Cannot remove most of the chemical impurities

● The water may look clear after filtration but there may still be some bacteria and viruses in the water. So, the

water must be further disinfected. Mostly Chlorination, SODIS or boiling is used.

*Centre for Affordable Water & Sanitation Technology

SOURCE: http://www.cawst.org/en/resources/biosand-filter; http://en.wikipedia.org/wiki/BioSand_Filter

A Prototype was constructed at Astitva during a visit to Wada.

• Types of Gravel used:

1) < 0.7 mm gravel - filtration sand

2) 0.7-6 mm gravel - separation gravel

3) 6-12 mm gravel - drainage gravel

• the filtration sand bed be not less than 50 cm in depth

-- To ensure attachment and deactivation of viruses

-- 50 cm is the minimum depth at which slow sand filters operate

• Drainage and separation gravel to prevent filtration sand in water flow.

• Literature suggests minimum height of layer must be 3 times the mean diameter of grain size.

Thus, 5 cm seems safe (2 times this minimum)

SODIS (Solar Water Disinfection) http://www.sodis.ch/index_EN

SODIS Ueberlandstrasse 133 P.O. Box 611 8600 Duebendorf, Switzerland

Phone +41 58 765 52 86

info@sodis.ch

Principle: UV-A rays in sunlight kill germs such as viruses, bacteria and parasites (giardia and

cryptosporidia)

● Clear and Transparent (generally PET) bottles are filled with the water and placed in full sunlight for at least

6 hours (depending on sunlight)

● PET bottles are better than PVC (PVC have a pungent smell and doesn’t burn as easily as possible

whereas PET have)

Restrictions/Requirements:

● Bottles must be transparent, colourless, not heavily scratched

● Water must have turbidity less than 30 and depth shouldn’t be more than 10 cm

Disadvantages:

● If more than half of the sky clouded might be required to keep it under sunlight for 2 days

● Water that has been polluted with chemicals (poisons, fertilisers, etc.) must not be used since SODIS

method change the chemical composition

● Once removed from sunlight, remaining bacteria may again reproduce in the dark

● Only useful in regions with good sunlight and water have only biological

contamination

Source: http://en.wikipedia.org/wiki/Solar_water_disinfection ; http://www.sodis.ch/index_EN

Observations:

As observed, the households in most of the villages in India get their water from

the dug-up well. Majorly it’s polluted with biological contamination. Villagers do

put chlorine powder in wells which is fine. But

1. Once all the TCL is used, Gram Panchayat delays the delivery of TCL

packets. So, during this period people drink contaminated water

2. The other point is that the wells are not properly covered so they also have

organic substances like a dead frog (seen in a well during the field visit),

leaves from the plants etc. which results in the production of carcinogenic

THMs. These bi-products can be avoided:

i. if the wells are properly covered and/or

ii. Instead of directly putting TCL in well they first filter it using activated

carbon or sand filter and then use TCL.

Thank You