Bacterial Examination of water is useful for: (1) Detection of faecal pollution in potential water supply (very sensitive test). (2) Assessment of water treatment plant performance. (3) Confirmation of hygienic safety of final water entering supply. (4) Surveillance of water quality throughout distribution. (5) Indicator bacteria: give Quantitative results therefore used as basis for these standards: (1) Raw Water Quality (2) Treated Water Quality (3) Distribution System Water Quality (4) Bathing Water Quality (5) Quality of Water for shellfish growing (6) Quality of water for re-use in irrigation.

1. Bacterial Examination of Water
• Objectives
To understand the theory and practice of monitoring the bacteriological
quality of water.
To know the typical bacteriological standards required for Raw and
Treated Water.
References
Water Supply - Twort et al
Examination of Water for Pollution Control (Vol 3) - M.J. Suess
Report 71 - The microbiology of water 1994 Part 1 - Drinking Water ,HMSO
UK Water Supply (Water Quality) Regulations 2000 (SI 3184)
http://www.dwi.gov.uk/regs/si3184/3184.htm
http:// www.dwi.gov.uk/regs/pdf/Interim2003.pdf (Guidance for SI 3184)
EC Directives
(98/83/EC) Drinking Water - Official Journal L 330
(80/778/EEC) Drinking Water - Official Journal L229
(75/440/EEC) Abstraction - Official Journal L 194

2. Water Supply Bacteriology
useful for:
(1) Detection of faecal pollution in potential water supply (very sensitive test).
(2) Assessment of water treatment plant performance.
(3) Confirmation of hygienic safety of final water entering supply.
(4) Surveillance of water quality throughout distribution.
(5) Indicator bacteria: give Quantitative results therefore used as basis for these
standards:
(1) Raw Water Quality
(2) Treated Water Quality
(3) Distribution System Water Quality
(4) Bathing Water Quality
(5) Quality of Water for shellfish growing
(6) Quality of water for re-use in irrigation.

3. Typical Bacterial Concentrations in
Water Samples
Coliform/100 ml
Underground water <100 (<10)
Upland stream 500
Lowland river 104 (Tyne typically 20,000/100ml)
Industrialised river 105
Raw sewage 107
“Royal Commission” effluent 105
Tap Water 0

4. Bacterial Examination of Water
(1) Can easily distinguish faecal from other sources of contamination.
(2) Extremely sensitive tests.
107 E.coli/100 ml raw sewage
Can detect 1 E.coli/100 ml
Therefore can dilute sewage x 10-6 and still detect it
Much more sensitive than many chemical tests.
(3) Simple, reliable tests
Dehydrated media, pre-sterilised materials available.
Consistent monitoring across Europe (World!)
(4) Quantitative result therefore can define microbiological standards for different
water uses.

5. Indicator Organisms
• 1. Suitable for analysis from all sources
– tap, river, sea, industrial.
• 2. Present wherever enteric pathogens exist
• 3. Should survive longer than hardiest enteric pathogen
• 4. Should not reproduce in the water
• 5. Easy and Specific Assay
• 6. Harmless to humans
• 7. numbers should reflect (correlate with) degree of faecal pollution

6. Bacterial Examination of Water
Some important Definitions:-
(1) Coliforms:- Gram -ve, non-spore forming rods.
Aerobic/facultative anaerobes
Lactose Acid + Gas, 48 hr. 35C (37C)
Oxidase negative.
Tolerant of bile salts (and synthetic detergents, SDS)
(2) Thermotolerant Coliforms:(TTC)
(a) Faecal Coliforms:- As above but at 44C.
(but not all 44 C + orgs.are faecal in origin)
(b) Escherichia coli:- Thermotolerant Coliforms (44 C)
which give Acid + Gas in 24 hrs.
And form Indole from Tryptophan
(MR +; VP -; Citrate -)

7. (3) Faecal Streptococci S. faecalis S. faecium S. bovis etc.
Gram positive cocci, chain forming.
Possess Lancefields Group D antigen
Grow in presence of Bile, Salt and Sodium azide, at 45oC.
In animals, are as numerous as E.coli has been used to
In humans are less numerous than E.coli (FC/FS > 4) identify source
of pollution
F.S. Survive in seawater better than E.coli.
Rapid death at 20oC but prolonged survival < 10oC.
More resistant to chlorination than Coliforms + E.coli.
(4) Sulphite-reducing Clostridia and Clostridium perfringens
Gram positive, spore forming rods. Anaerobic.
Spores survive much longer than vegetative cells of other indicators.
Much more resistant to chlorination.
Useful test for water supplies which can only be sampled occasionally and which
may have intermittent pollution (e.g. shallow wells/springs)
Also useful for examining marine sediments to detect zone affected by sewage
outfall. (Range > 10 km)

8. Raw Water (Abstraction) Standards
1962 WHO (Omitted 1973 and 1984)
Coliform/100ml Classification
0-50 I Needs Disinfection only
50-5,000 II Needs Conventional treatment
5,000-50,000 III Needs Extensive treatment
>50,000 IV Unacceptable - only use if
nothing else
1975 EEC
A1 A2 A3
Coliforms/100 ml 50 5,000 50,000
Faecal Coliforms/100 ml 20 2,000 20,000
Faecal Streps./100 ml 20 1,000 10,000
Salmonellae Nil/5 l Nil/5 l
DisinfectionConventional Intensive
Only Treatment Treatment
Conventional Treatment
- flocculation, coagulation, decantation,
filtration, chlorination
Intensive Treatment
- breakpoint chlorination, flocculation, coagulation,
decantation, filtration, carbon adsorption, disinfection (ozone, final chlorination)

9. Typical Bacterial Counts for River
Thames at Water Intake
Total ‘aquatic’ bacteria (20 C)1.2 x 106 /100 ml
Total ‘Coliform’ bacteria (37 C) 1.6 x 105 /100 ml
Faecal Coliforms 2.5 x 103 /100 ml
E.coli 8 x 102 /100 ml
Salmonellae 3/litre
Typical pattern - Highest counts in winter
High counts after heavy rainfall
High counts when river flow high
No: fluctuates widely.
Problems -
(1) Aftergrowth/regrowth
(2) Slime formation
(3) Contamination of Distribution System
(4) Resistance of viruses

10. WHO Guidelines 1984
Bacteriological Quality Treated Water
Piped supplies CFU/100 ml
Treated water entering Faecal coliforms - 0
distribution Coliforms 0
Untreated water entering Faecal coliforms - 0
distribution Coliforms - 3 in occ. sample
not in consecutive samples
0 in 98% yearly samples
Water in distribution Faecal coliforms 0
system Coliforms - 3 in occ. sample
not in consecutive samples
0 in 95% yearly samples
Unpiped supplies Faecal coliforms - 0
Coliforms - 10
Bottled drinking water Faecal coliforms - 0
Coliforms - 0
< 1 NTU
pH < 8
0.2 - 0.5 Cl2

11. 1980 EEC Drinking Water Directive
(80/778/EEC)
Treated water leaving WTP
Sample (M.F.) (MPN)
Total Coliforms 100 ml 0 <1
Faecal Coliforms 100 ml 0 <1
Feacal Streptococci 100 ml 0 <1
Sulphite reducing Clostridia 20 ml - <1
Tap Water 37C Plate count <10 /ml
(guide level) 22C Plate count <100 /ml
Bottled Water 37C Plate count <20 /ml
(MAC) 22C Plate count <100 /ml
Amended by 1998 Council Directive (98/83/EC)
essentially the same as above and implemented in UK as Water Supply (Water
Quality) Regulations 2000.

12. Sampling Frequency
At consumers Taps
WHO (1984)
• 1 per month per 5000 population (up to 100,000 pop)
• plus 1 per month per additional 10,000 population
EC Directive (80/778/EEC)
• same rate as to WHO (but up to 300,000 pop)
• no increments above 300,000 pop
At Treatment Works
WHO (1984)
daily testing for total coliforms
EC Directive (80/778/EEC)
no requirements

13. Volume(m3
/day) CheckMonitoring
(NoperYear)
AuditMonitoring
(NoperYear)
<100 Memberstatesets Memberstatesets
100-1000 4 1
1000–10,000 1 (+1per3000m3
/d)
10,000–100,000 3 (+1per10,000m3
/d)
>100,000
4
+3forevery1000m3
/d
10(+1per25,000m3
/d)
Sampling Frequency
1998 Drinking Water Directive (98/83/EC)
At consumers taps
Assume 200L (0.2 m3) per person per day
(1 m3 = 5 people)

14. Directive and National Requirements
Concept of Supply Zones, fixed annually, ideally linked to a Supply Point
(i.e.WTW, pumping station, blending point, service reservoir).
Microbiological Quality
(at Consumers taps)
Sample (M.F.) PCV
Total Coliforms 100 ml 0
Escherichia coli 100 ml 0
Enterococci 100 ml 0
Clostridium perfringens 100 ml 0
Colony count - at 22C and 37C (no abnormal change)
(at works, Service reservoirs)
TC, E. coli, Clostridium, Colony counts – (quality requirement as above)
Cryptosporidium (< 1 per 10 litres daily monitoring)
( in Bottled water)
Enterococci and E. coli (0/250ml)
Pseudomonas aeruginosa (0/250ml)
Colony count (22C < 100/ml; 37C < 20/ml)
UK Regulations, Water Supply Regulations 2000

15. Frequency of monitoring
Audit and Check monitoring, Standard and Reduced (where deterioration is negligible)
Frequencies . Therefore frequency varies widely, sliding scales based on:
• Output of WTW (m3/day)
• Size of Supply Zone (<100 to 100,000 p.e)
At Taps (no: per zone unless stated otherwise)
TC, E. coli 1 per month per 5000 population (zones of 100,000 pop)
Enterococci - 1 to 8 per year
Clostridium perfingens* 1 to 8 per year (2 to 76 per year if surface water source)
Colony count* 2 to 76 per year
At works, and service reservoirs (no: per zone)
TC, E. coli , 4 -365 per year
Clostridium perfringens* 1 to 48, or 2 to 2190 (if surface water source)
Colony count* 4 -365 per year
* these termed “Indicator Parameters” (Schedule 2), any failures require further
investigation. Rest are “Prescribed Concentration or Value (PCV)” , (Schedule 1).
Note ; residual disinfectant monitored at taps and works at the same frequency as TC.
UK Regulations, Water Supply Regulations 2000

16. Bacterial Removal
Storage
After 30 days, assume 90% removal E.coli
Coagulation, Sedimentation & Filtration
Assume 99% removal
Disinfection (Cl2)
Assume further 99% removal
Therefore 4-5 log removal of bacteria in water treatment process.
i.e. 100,000 E.coli /100 ml < 1 E.coli /100 ml
10 20 30 40
100
10
1
0.1
time (d)
%
surviving
E. coli 16C
E. coli 12C
37C Plate Count
Storage
Reservoir

17. Supplies at risk from
Microbiological Problems:
Lowland waters with the following characteristics:-
(1) Plate counts from distribution
> 103/ml (22oC 7 day YEA)
(2) Total Organic Carbon, as C
> 2 mg/l in final water
> 0.5 mg/l change in distribution system.
(3) Dissolved oxygen
10-15% average fall in distribution system.
(4) Disinfectant
Failure to maintain residual throughout the distribution system.

18. Enforcement of Standards:
• Drinking Water Inspectorate (DWI)
– formed 1990
– monitors water undertakers’ performance
• Water Undertaker
– analyse samples and keep records
– Produce reports
– Investigate outbreaks (+ inform DWI)
• Identify source (e.g. consumer’s installations or supplies?)
• Possible failure
TC but not FC in supply
– Possible Causes: sludge in pipes, nutrients in water, dead-ends (low chlorine
residual)
• Solutions
– distribution system checks
– flush network
– switch raw water source
– increase disinfectant strength