Assessment and surveillance of drinking water quality

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ASSESSMENT AND SURVEILLANCE

OF DRINKING WATER QUALITY

Guide : Dr.Ansuman Panigrahi

Associate Professor Dept . Of Community Medicine,KIMS

Presented By: Dr . Shalini Ray

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Quality

Quantity

WATER AND HEALTH

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The WHO published guideline for drinking water quality.

Its implementation ensures safety of drinking water supplies.

Guidelines for drinking water quality recommended by WHO (2011) relate to :

I. Acceptability aspects II. Microbiological aspects III. Chemical aspects IV. Radiological aspects

GUIDELINES FOR DRINKING WATER QUALITY: 

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Acceptability

Physical parameters

Inorganic constituents

I. ACCEPTABILITY ASPECTS: 

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Turbidity Drinking water should be free from turbidity.

Interferes with disinfection and microbiological determination.

Acceptable level - turbidity of less than 4 NTU

Measured with Turbidity meter 

PHYSICAL PARAMETERS

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Drinking water should be free from colour . Organic matter, iron , manganese , industrial waste

etc. The guideline value - 15 true colour units (TCU).

Colour

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Develop due to contamination by chemicals. Storage and distribution.

Indicative of pollution or malfunction during water treatment or distribution.

Taste and odour : 

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Low water temperature Decrease the efficiency of treatment process. High water temperature Enhances the taste, odour . Corrosion problem may increase. No guideline value is recommended.

Temperature: 

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All water including rain water contain chlorides.

Standard level for chloride - 200 mg/ litre .

Maximum permissible level - 600 mg/ litre

Measured by spectrophotometer or titration method.

Spectrophotometer

INORGANIC CONSTITUENTS Chlorides: 

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Taste threshold for calcium ion - 100-300 mg/ litre .

Excessive soap consumption and scum formation. Forms deposits of calcium carbonate scale on

heating. Soft water : low buffer capacity ,corrosive for water

pipes. Measured by titration method.

Hardness: 

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Ammonia originates from metabolic, agricultural and industrial processes and from disinfection with chloramine .

Natural levels - below 0.2 mg/ litre Anaerobic ground water contains 3mg/ litre Its presence indicates pollution by bacteria , sewage

or animal waste.

Ammonia

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pH< 7 causes severe corrosion Acceptable range - 6.5 to 8.5. Measured with pH meter

pH

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Acceptable limits- 0.05-0.1 mg/l Gives rotten egg odour (stagnant water) Iron On exposure to atmosphere ferrous iron oxidises to

ferric ion Gives reddish brown colour to water Deposit slimy coating on pipes Sodium Measured with Flame photometer. Average taste threshold for sodium - 200 mg/ l

Hydrogen sulphide:

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Flame photometer

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Important effect on taste of water Acceptability levels of TDS -<1000mg/litre Excessive levels cause scaling of boilers , pipes

Zinc Gives undesirable astringent taste Zinc content >5mg/litre gives opalescent look and

greasy film on boiling Manganese Acceptable levels-<0.1mg/litre Excess Mg stains sanitary ware and laundry

Total dissolved solids(TDS)

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Increases corrosion of steel fittings Concentration >1mg/litre cause staining of laundry and

sanitary ware

Aluminium Concentration >0.2mg/l leads to deposition Aluminium

hydroxide floc.

Copper 

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Bacteriological indicators

Virological aspects

Biological aspects

ii) MICROBIOLGICAL ASPECTS

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Coliform organisms- Present in human intestine Presence indicates faecal contamination Faecal streptococci- Occur in faeces Confirmatory evidence of recent faecal

contamination Cl.perfringens – Resist chlorination Presence suggest faecal contamination

Bacteriological aspects

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Coliforms - Faecal groups -E coli Non Faecal – Klebsiella aerogens

Why coliforms? Coliforms are abundant in intestine(200-400billion/day) Easily detected by culture Survive longer than other pathogens Greater resistance to forces of natural purification

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Bacteriological quality of drinking water

ORGANISMS GUIDELINE VALUE

All water intended for drinking Must not be detectable in any 100ml sample

Treated water entering distribution system(E.coli ,total coliform count)

Must not be detectable in any 100ml sample

Treated water entering distribution system(E.coli ,total coliform count)

Must not be detectable in any 100ml sampleIn c/o large supplies, must not be present in 95% of samples taken throughout any 12month period

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Virological aspects

Free from virus Disinfect with 0.5 mg/ml of free chlorine

residual after contact period of at least 30 minutes at pH 8.(Hep A)

Others need 0.2 mg/ml Criteria

Ozone :0.2-0.4 mg/ml for 4 minutes

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Biological aspects

Protozoa- E.histolytica , Balantidium coli Helminths- Infective form of round worm, hook worm

dracunculus medinensis , schistosomes Free living- fungi ,algae interfere with water treatment

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Giardia lamblia

Guinea worm disease

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Chemical aspects

Inorganic constituents

Organic constituents

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INORGANIC CONSTITUENTS

Inorganic constituents

Guideline value

Arsenic 0.01mg/lCadmium 0.3ug/lChromium 0.05 mg/lCyanide 0.07 mg/l , acute toxicityFluoride 1.5mg/lLead 0.01mg/lMercury 0.006 mg/lNitrate 50mg/lNitrite 3mg/lSelenium 0.01mg/l

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Nitrate & nitrite – nitrate - 50 mg/l nitrite – 3 mg/l Conc: of nitrate + Conc:of nitrite = < 1 G.value of nitrate G.value of nitrite

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ORGANIC CONSTITUENTSORGANIC CONSTITUENTS UPPER LIMIT OF CONC(mcg/l)

CHLORINATED ALKANES

CCl4 2

dichloromethane 20

CHLORINATED ETHENES

Vinyl chloride 55

1.1-dichloroethene 30

1.2-dichloroethene 50

AROMATIC HYDROCARBONS

benzene 10

toluene 700

xylene 500

Ethyl benzene 300

styrene 20

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PAH Guidelines

PAH and turbidity Restriction on coal tar based lining in storage tanks Source of contamination should be identified

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Radiological aspects: 

Radioactivity should be as low as possible Guideline values- Gross alpha activity-0.5 Bq /L Gross beta activity- 1.0 Bq /L 1Bq= 1 disintegration per second

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SURVEILLANCE OF DRINKING WATER QUALITY

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“ Continuous and vigilant public health assessment

and overview of the safety and acceptability of

drinking-water supplies”(WHO-1976)

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Quality Quantity Accessibility Affordability Continuity of drinking-water supplies

Service indicators

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•At home•Source•Safe source•Ways to prevent

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Identify & evaluate factors associated with drinking water which could pose a health risk

To take both preventive & remedial action

For development of rational strategies for improvement of quality of water supply services

To meet agreed national standards & institutional targets

Objectives of Surveillance :

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Audit approach

Information regarding system performance

Review records to ensure data is reliable.

Surveillance approach:

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Activities In Surveillance FunctionApproval of new sources(Including private owned)

Watershed protectionApproval-construction & operating procedures of water

works disinfection of the plant & distribution system periodic flushing programmes & cleaning of water storage facilities certification of operators regulation of chemical substances Cross-connection control ,back flow prevention ,leak detection control

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Sanitary surveys

Monitoring programmes

Development of codes of practice for well construction ,pump installation and plumbing

Inspection quality control in bottled water

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Elements of surveillance programme

Sanitary Survey Sampling Bacteriological Surveillance 1)Presumptive Coliform Test - Multiple Tube Method Membrane Filtration Technique 2)Detection Of Faecal Strep & Cl.Perfringes 3)Colony Count Biological Examination Chemical Surveillance

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A sanitary survey defined as “an on-site inspection and evaluation by a qualified

person of all the conditions, devices, and practices in the water supply system which pose a danger to the health and well being of the water consumer ”

Sanitary survey: 

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A new source is being contemplated Laboratory analysis indicates hazard to health An outbreak occurs To interpret bacteriological, chemical and physical

analyses of samples  When any change takes place that can affect the

water system, e.g. industries coming up in watershed and

On a regular basis

When sanitary survey is done?: 

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Ensure no external contamination Asepsis Glass bottles with securely fitting stoppers

or caps with non toxic liners.

Sample for general analysis= 2 litres(non-acidified) Bacteriological analysis=250 ml (sterilized bottle) Metals analysis=1000 ml (acidified sample)

Sampling : 

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Sampling done by sampling assistant

Winchester Quart bottles for physical & chemical examination: 

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Water from a tap in a distribution system

Water from watercourse (river, lake,well etc)

2 basic types of sources for sampling

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Sampling technique

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Sampling from well

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Sampling from reservoir

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Date Time of collection Despatch Source Rainfall Findings

Transport & storage of sample

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Presumptive Coliform Test

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For confirmed test

Take the positive tube from the presumptive test

Incubate one plate at 37°C for 24 hours and another at 44.5°C for 24 hours.

Look for typical colonies in the media ; blue black with green metallic sheen colonies are of E. coli

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Membrane filteration technique

Lactose Tegritol agar Membrane lauryl sulfate lactose

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Nutrient agar at 37 deg C and 22 deg C An estimate of the general bacterial purity of water. Same source at frequent intervals may be of

considerable value. A sudden increase in the colony count may give the

earliest indication of contamination.

COLONY COUNT

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The recommended plate counts are

Water at the point of consumption

Plate count after 2 days at 37 deg C

Plate count after 3 days at 22 deg

( i ) Disinfected 0 20

(ii) Not - disinfected 10 100

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The National Rural Drinking Water Quality Monitoring & Surveillance Programme was launched in February 2006 (2005-06)

Institutionalization of community participation and involvement of PRIs for water quality monitoring & surveillance of all drinking water sources

Jal surakshak

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Park K. Textbook of preventive and social medicine. 22nd ed. Jabalpur (India): Bhanot publishers; 2009. p. 667-78.

WHO - Guidelines for Drinking-water quality: surviellance & control of community supplies. Vol.3, Recommendations. – 3rd ed.

Uniform Drinking Water Quality Monitoring Protocol: Govt Of India, Ministry of Drinking Water and Sanitation ; Feb 2013

http://www.mdws.gov.in/wqms

References

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Thank you