FNQ Water Conference Michael Lever

Transcription

1 FNQ Water Conference 2015 Michael Lever

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3 Multiple Barriers SOURCE TREATMENT Standards Procedures DISINFECTION Monitor Correction DISTRIBUTION

4 Diseases Associated with Water

5 On the Mode of the Communication of Cholera John Snow 1849 Cholera epidemic London (1848) > 500 deaths in 10 days Ghost Map traces deaths to the Broad St pump in Soho Pump handle removed Outbreak controlled Dr William Budd, Typhoid expert Intestinal Fever Lancet 1850 Reduced Cholera and Typhoid deaths from 2000 to 29 ( ) by using Chloride of Lime

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7 Cryptosporidium Left emerging Cryptosporidium sporozoite Right Giardia (8 to 12µm) Cryptosporidium (4 to 6 µm) First identified in animals (1907) but not in water until 1984 (Braun Station, Texas) Chlorine resistant but inactivated by O 3 or UV

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9 Analysis The outbreak was caused by heavy rain in the catchment following lamb scouring. Cryptosporidium ranged from 1 oocyst per litre at the plant up to 24 oocysts per litre in tap samples. There were no faults in plant operation filters removed 80% of cryptosporidium cysts. However, the backwash supernatant recycled 10,000 cysts per litre with a resultant breakthrough. For the number of cysts present in the source water, conventional treatment was inadequate.

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11 North Thames Cryptosporidium Feb to April, 1997, 746,000 boil water advisory notices issued 345 confirmed cryptosporidiosis cases 26 people were hospitalized, two died The largest cryptosporidium outbreak from a ground water supply The first reported outbreak caused by filtered bore water Only six of 605 boreholes in an earlier UK survey had tested positive for cryptosporidium (maximum level of oocysts was 1/L)

12 Source Water Issues 2 year drought followed by rainfall 160 % above February average Well water supplied from a chalk aquifers metres (m) deep Turbidity increased from < 0.5 to 2 NTU Well head 17m from a river with sewage discharged 8km upstream River water samples at sewage works revealed few or no oocysts Source water not expected to have bacteria or cyptosporidium Plant designed to remove traces of pesticides by Ozone/GAC

13 Maximum Cryptosporidium Oocysts Raw Water Backwash Filtered Water Distribution Clay Lane Water Treatment Plant Ozone and granular activated carbon filters Designed to remove pesticides by adsorption, no coagulation 8 deep wells, good quality source water, normally < 0.5 NTU Contaminated surface water penetrated one of the well sources Ozone dose and contact time too low to destroy cryptosporidium Oocyst load too great for coarse GAC filter media (zero removal)

14 Östersund Sweden

15 Lake Storsjön

16 Treatment Plant

17 Östersund Analysis

18 Milwaukee Milwaukee, Wisconsin, population 880,000 people In 1993 the largest waterborne disease outbreak in U.S. March 23 to April 8 more than 400,000 people infected 4400 people were hospitalized with cryptosporidiosis 100 persons are believed to have died from the illness

19 Milwaukee Water Treatment Plant Intakes Sewage Plume Plant Turbidities

20 Background There were two contributing factors: A contaminated source water (Lake Michigan) and Sub-optimised coagulation allowing cryptosporidium to pass through the filters at the Howard water treatment plant The water treatment plant was commissioned in 1962 It has a capacity of 100 mgd (400m 3 /day) with eight filters Its intake is 13 metres deep, 2.3 km from the shore-line Raw water quality is usually good but with variable turbidity However, the water intake was within a sewage plume

21 Operating Data Changed to poly-aluminium chloride after 30 years using alum Settled water turbidities increased from 2 to 6 NTU on the 24 th Filtered water turbidities increased from about 0.2 to 0.5 NTU Jar tests showed more cloudiness at higher PACl doses and therefore operators reduced dosing rates on the 26 th This resulted in inadequate coagulation and an increased ave filtered water turbidity of 2.1 NTU (individually up to 10 NTU) On 2 nd April PACl dosing was stopped and changed to Alum Turbidity Levels stabilised at 0.2 NTU on the 7 th April

22 Notes E-coli counts were zero and the treated water complied with both State and Federal standards for turbidity and water quality 7 other treatment plants used water from Lake Michigan at the same time and had turbidity problems but not cryptosporidium The start of the outbreak can be correlated with a critical turbidity value of 0.5 NTU on 24 th March and high for the next 7 days During the outbreak: the filtration rate was very low (1 m/hour) the sand media was very fine (0.35 mm) filters were rested after backwashing These factors did not compensate for ineffective coagulation

23 North Battleford Battleford, Canada, population 14,000 people Starting March 2001, people experienced severe diarrhoea The first and largest cryptosporidium outbreak in Canada 5800 to 7100 cases of gastroenteritis, 50 hospitalised Water and Sewage treatment plant operational problems Cryptosporidium, Giardia, E.coli in the Saskatchewan River Late boil water notice Council in denial and indifferent

24 North Battleford Canada

25 Primary Cause of Cryptosporidium Outbreak

26 Inquiry Criticisms Operating the plant 8 hours per day not good practice (stop/start) A lack of training. No-one with the knowledge to make good operating decisions - believed Crypto removed if turbidity < 1 and Chlorine > 0.5 Council aware of plant deficiencies - reported by Consultants, foreman (absent on stress) and a persistent operator asked to resign Limited expenditure on plants but an accumulated $1.2 in utility fund City commissioner and the mayor not convinced water was the cause Mayor had resented and dismissed an earlier cryptosporidium warning Mayor resisted boil water notice (could have been 3 weeks earlier) Last plant inspection by State Government 10 years earlier

27 Washington County Fair Albany NY (1999) E. coli O157:H7

28 Analysis Largest E. coli O157:H7 outbreak in United States Washington County Fair, August 23-29, 1999, Albany NY Up to 5000 people developed gastrointestinal illness 781 confirmed cases, 71 hospitalized, two deaths Septic system approximately 10 metres from a well Un-chlorinated well water used to make drinks and ice

29 Walkerton This was the largest E. coli O157:H7 outbreak in Canada Walkerton is a prosperous community of 5000 people Starting May , people began to experience diarrhoea There were an estimated 2300 cases of gastroenteritis Seven people died, 65 people were hospitalized

30 Walkerton This was the largest E. coli O157:H7 outbreak in Canada Walkerton is a prosperous community of 5000 people Starting May , people began to experience diarrhoea There were an estimated 2300 cases of gastroenteritis Seven people died, 65 people were hospitalized

31 Analysis On April 22 nd 70 tons cattle manure spread at a nearby farm Heavy rain, 134 mm in five days with 70 mm falling on 12 May Samples on 1 st and 8 th botched, 15 th May E. coli TN to count Water sourced from a shallow ground water wells No treatment plant, operators fail to chlorinate the water Manager and Foreman jailed for: drinking on the job failing to use adequate doses of chlorine failing to monitor chlorine residuals daily falsifying operating records (0.5 or 0.75)

32 Procedures are the key to preventing waterborne disease outbreaks caused by contamination of the distribution system

33 Procedures for Reservoir Maintenance

34 Gideon, Missouri Location - Gideon, an unremarkable mid-west town of 1000 people A large waterborne salmonella outbreak between Nov and Dec 1993 In November, seven cases of salmonella typhimurium confirmed There were in excess of 650 cases of acute gastroenteritis 15 people were hospitalized and there were 7 deaths

35 Analysis Two bores 390 metres deep constructed mid-1930s 500 KL/day good quality but un-chlorinated supply Contaminated sediment most likely pulled into the distribution system by an extensive flushing program Water storage tower had corroded roof vents and an uncovered hatch Bird feathers were observed in the tank Coliforms detected in water and sediment samples

36 Alamosa, Colorado Alamosa, population 8900 people A large waterborne salmonella outbreak, 2008 Almost 2000 people reported gastrointestinal illness, 442 confirmed salmonella cases, one death Un-chlorinated but good bacterial bore-water

37 Bore water from a low risk confined aquifer (300 to 550m) No coliforms for 5 years and all earlier positives negative in re-samples First salmonella case confirmed on March 6, water advisory 17 th Salmonella found in water samples and Weber Reservoir on March 20 Disinfection and flushing commenced, reservoirs drained Weber reservoir in poor condition (last cleaned in years) A new membrane and chlorination treatment plant was in commissioning stage but to meet new 10 µg/l EPA standard for Arsenic Contamination of reservoir by bird faeces or hibernating rodents

38 Weber Reservoir

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41 Nokia Reticulation System

42 Cross connection

43 Epidemiology

44 Cabool Missouri Outbreak in ; Population E. coli O157:H7 cases, 82 hospitalised, 4 deaths 4 Bores, depth 300 to 400 metres, cased to 135 metres Water not chlorinated but no Coliforms in previous 10 years Distribution system in poor condition with 35% water loss Sewerage system worse, overloaded with frequent overflows Two broken water mains contaminated by sewage

45 Sewage + No Chlorine + No Testing = Trouble

46 Change often precedes risk but so does complacency Storms/Heavy rainfall Plant maintenance Switch coagulant Mains break Hydrant flushing Pathogens are the greatest threat to water safety 80 % of protazoan incidents - caused by ineffective filtration 95 % of bacterial incidents - due to ineffective (or zero) chlorination 60 % of incidents caused by faults in storage or distribution system

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48 Freuchie

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51 Analysis

52 South Bass Island

53 Coliforms in private wells

54 Hydrology