COMMUNITY MEDICINE -TOPIC: ENVIRONMENT

1. Water sampling and Bacteriological
analysis of drinking water.
Dr.Mittal Rathod,
Community Medicine Dept.,
Associate Professor
AIIMS, JAMMU.

2. Contents
• Safe & wholesome water
• Water Quality –Criteria & Standards
• Water Sampling
• Bacteriological Analysis of Water: Methods
• Public Health significance

3. Learning Objectives
• To understand the water sampling methods.
• To know various Bacteriological indicators .
• To describe its importance & its usage.

4. Safe And Wholesome water
1. Pleasant to taste
2. Free from Pathogens
3. Free from chemicals
4. Usable for domestic purposes

5. Water Quality –Criteria & Standards
1. Acceptability aspects
a. Physical Parameters
b. Inorganic constituents
2. Microbiological aspects
a. Bacteriological Indicators
b. Virological aspects
c. Biological aspects
3.Chemical aspects
4. Radiological aspects

6. 7
Categories of Contaminants
Chemicals
 Organic
 Inorganic
 pH
Microbiological
Bacteria
Virus
Protozoa
Helminths
Physical
 Turbidity
 Colour
 Odor
 Taste

7. Water Sampling
1. Sampling for Physical & Chemical
Examination:
2. Sampling for Bacteriological
Examination:
-

8. Sampling for Physical & Chemical
Examination:
• Clean glass stoppered bottles
“Winchester Quart Bottles”
• Capacity Not < 2 L.
• Precautions:

9. Sampling for Bacteriological
Examination:
• General Considerations:
Clean sterilized glass bottle with glass stopper
Capacity: 200-250 ml
If sampled water is clorinated- add small
quantity of SODIUM THIOSULPHATE.
After collection immediately send to PHL.

10. Collection of the Sample From A Tap
• Open the tap fully
• Allow to run the water for at least 2
minutes
• Fill the sample bottle from gentle
stream of water, avoid splashing.
• If tap is required to be sterilized than
use blow lamp/ spirit lamp

11. Collection of the Sample From Rivers,
Lakes, Reservoirs, Wells
• Not to far or not too near the
bank.
• Take sample from Point of draw
off.
• Here bottle requires string.
• Not too superficial or not too
deep

12. Transport & Storage of samples
• As soon as possible.
• If required to store: keep in ice, not more than
48 hrs.
• Write date & time of collection, dispatch,
source of water, any recent rainfall, sanitary
survey details.

13. Bacteriological Indicators
• Primary Bacterial Indicator:
1. Coliform group of organism
• Supplementary Bacterial Indicator:
2. Faecal streptococci
3. Cl. perfringens

14. Significance
• Failure to provide adequate protection
• Effective Treatment
• Disinfection of drinking water
• Posses risk to…..
“CONTAMINATION”

15. ContaminationHappenswhenwater
comesincontact.
• Faecal matter
• Sewage contamination

16. Coliform organisms
• Any coliform
• Faecal 0r Non-Faecal

17. Reasons
1. Abendance of coliforms constantly in human
intestine.
2. Easily detected
3. Longer survival
4. Have greater resistance to forces of natural
purification

18. Methods for detection of Coliforms
• Presumptive coliform test
a. Multiple tube method
• Confirmatory Test: EIKJMAN’S TEST
• Membrane Filtration Technique
• Colony count

19. Multiple tube method
• Estimation of MPN of coliform organisms in
100 ml of water.
• Culture Media: McConkey’s Lactose Bile Salt
Broth.
• Indicator: Bromocresol Purple
Incubate for 48 hrs

20. MPN cont…
• Results: Fermentation & Acid & Gas formation
• “ Presumption” of coliform organisms

21. Confirmatory Test
• Subculture each presumptive positive tubes in
2 tubes of brilliant green bile broth.
One tube at 37 C * 48 hrs
Second tube at 44 C *6-24 hrs
True MPN Index: McCrady’s tables.

23. Most Probable Number (MPN)
# Positive
Tubes
MPN Index
(CFU/100mL)
0 <1.1
1 1.1
2 2.2
3 3.6
4 5.1
5 6.9
6 9.2
7 12.0
8 16.1
9 23.0
10 >23.0
Sample Table for
10 tube test

24. Most Probable Number (MPN)
– Quantitative results
– Simple to understand and use
– Relatively inexpensive
– Can be used with turbid water
– Requires some training & Requires incubator &
other equipment

25. Membrane Filtration Technique
• A measured volumn of water is filtered
through a membrane “ Cellulose ester”.
• Bacteria present in water- Retained on the
surface of the membrane.
• Inoculate on media
• Count the colonies

27. 25
Membrane Filtration: Advatages
–Most accurate test method
–Ability to test many samples at once
–Internationally recognized method
–Rapid, Gives direct result.
–Useful in rural areas,Samples can be tested in
the field

28. 26
Membrane Filtration: Limitations
– Requires more training
– Requires additional equipment
– Cost of consumables can be high
– Turbid water interferes with bacterial growth.
– Noncoliforms interferes with counting of coliforms.
– Toxic substances in the water may be absorbed by
filter and interferes with bacterial growth.

29. Colony count

30. Colony count cont…
• On Nutrient Agar:
37 deg C 22 deg C
• Count the colonies
• Sudden increase in colony count: earliest
indication of contamination.

31. • Recommended plate count:
Water at point
of consumption
After 2 days at
37 deg C
After 3 days at
22 deg C
Disinfected 0 20
Not- disinfected 10 100

33. Faecal steptococci
• It occurs regularly in Faeces but lesser than E.coli.
• It is a indicator of Recent fecal contamination.
• Highly resistant to drying.
• Imp: after laying new mains or repairs in
distribution systems/ surface run off/ ground
water.

34. Cl. perfringens
• It occurs regularly in Faeces but lesser than
E.coli.
• Spores- survive in water for longer duration.
• It is a indicator of Remote fecal contamination,
in absence of coliform.

35. Summary
• Water sampling Bottle:
• Coliform: Relaible indicator, MPN, Mccrady’s
table, Ejkman’s Test.
• Faecal steptococci: Recent fecal contamination.
• Cl. Perfringens: Remote fecal contamination.

36. Thank You…