Bacterial Removal From 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.

ReferencesWater Supply - Twort et alExamination of Water for Pollution Control (Vol 3) - M.J. SuessReport 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.htmhttp:// 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

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.

Typical Bacterial Concentrations inWater 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

Bacterial Examination of Water

(1) Can easily distinguish faecal from other sources of contamination.

(2) Extremely sensitive tests.

107 E.coli/100 ml raw sewageCan detect 1 E.coli/100 mlTherefore can dilute sewage x 10-6 and still detect itMuch 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.

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

Bacterial Examination of Water

Some important Definitions:-

(1) Coliforms:- Gram -ve, non-spore forming rods.Aerobic/facultative anaerobesLactose 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 -)

(3) Faecal Streptococci S. faecalis S. faecium S. bovis etc.Gram positive cocci, chain forming.Possess Lancefields Group D antigenGrow in presence of Bile, Salt and Sodium azide, at 45oC.

In animals, are as numerous as E.coli has been used toIn 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 perfringensGram 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)

Raw Water (Abstraction) Standards

1962 WHO (Omitted 1973 and 1984)

Coliform/100ml Classification0-50 I Needs Disinfection only50-5,000 II Needs Conventional treatment5,000-50,000 III Needs Extensive treatment>50,000 IV Unacceptable - only use if

nothing else

1975 EECA1 A2 A3

Coliforms/100 ml 50 5,000 50,000Faecal Coliforms/100 ml 20 2,000 20,000Faecal Streps./100 ml 20 1,000 10,000Salmonellae Nil/5 l Nil/5 l

DisinfectionConventional IntensiveOnly Treatment Treatment

Conventional Treatment- flocculation, coagulation, decantation, filtration, chlorinationIntensive Treatment- breakpoint chlorination, flocculation, coagulation, decantation, filtration, carbon adsorption, disinfection (ozone, final chlorination)

Typical Bacterial Counts for RiverThames at Water Intake

Total ‘aquatic’ bacteria (20 C) 1.2 x 106 /100 mlTotal ‘Coliform’ bacteria (37 C) 1.6 x 105 /100 ml

Faecal Coliforms 2.5 x 103 /100 mlE.coli 8 x 102 /100 mlSalmonellae 3/litre

Typical pattern - Highest counts in winterHigh counts after heavy rainfallHigh counts when river flow highNo: fluctuates widely.

Problems -

(1) Aftergrowth/regrowth

(2) Slime formation

(3) Contamination of Distribution System

(4) Resistance of viruses

WHO Guidelines 1984Bacteriological Quality Treated Water

Piped supplies CFU/100 ml

Treated water entering Faecal coliforms - 0distribution Coliforms 0

Untreated water entering Faecal coliforms - 0distribution Coliforms - 3 in occ. sample

not in consecutive samples0 in 98% yearly samples

Water in distribution Faecal coliforms 0system Coliforms - 3 in occ. sample

not in consecutive samples0 in 95% yearly samples

Unpiped supplies Faecal coliforms - 0Coliforms - 10

Bottled drinking water Faecal coliforms - 0Coliforms - 0

< 1 NTUpH < 80.2 - 0.5 Cl2

1980 EEC Drinking Water Directive(80/778/EEC)

Treated water leaving WTP

Sample (M.F.) (MPN)Total Coliforms 100 ml 0 <1Faecal Coliforms 100 ml 0 <1Feacal Streptococci 100 ml 0 <1Sulphite 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.

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

Volume (m3/day) Check Monitoring (No per Year)

Audit Monitoring (No per Year)

< 100 Member state sets Member state sets

100 - 1000 4 1 1000 – 10,000 1 (+1 per 3000 m3/d) 10,000 – 100,000 3 (+1 per 10,000 m3/d) > 100,000

4 + 3 for every 1000m3/d

10 (+1 per 25,000 m3/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)

Directive and National RequirementsConcept 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.) PCVTotal Coliforms 100 ml 0Escherichia coli 100 ml 0Enterococci 100 ml 0Clostridium perfringens 100 ml 0Colony 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

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

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)

% s

urvi

ving

E. coli 16C

E. coli 12C

37C Plate Count StorageReservoir

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 oxygen10-15% average fall in distribution system.

(4) DisinfectantFailure to maintain residual throughout the distribution

system.

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 failureTC 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

Health guidelines for the use of wastewater in agriculture and aquaculture.

Technical Report Series 778, WHO, Geneva, 1989

This standard is based on epidemiological studies.

Category Reuse conditions Faecal coliforms (geometric mean /100ml)

A. Unrestricted Irrigation (crops likely to beeaten raw, Salad crops)

Less than 1000 faecal coliforms/100 ml

B . Restricted Irrigation. (Only crops which arenot eaten or not eaten raw, cereals, foddercrops, pasture and trees

No faecal coliform standard

Category Reuse conditions Parasites

A. Unrestricted Irrigation (crops likely to beeaten raw, Salad crops)

1 or less helminth egg per litre

B. Restricted Irrigation. (Only crops which arenot eaten or not eaten raw, cereals, foddercrops, pasture and trees)

1 or less helminth egg per litre.