WATER AND WALKERTON WALKERTON OUTBREAK

Transcription

1 WATER AND WALKERTON WAKE UP CALL WARNING WHO S NEXT? WALKERTON OUTBREAK May 19: Pediatric cases of bloody diarrhea May 20: E. coli O157:H7 identified May 21: Boil water order issued 1346 reported cases of gastroenteritis 167 confirmed for E. coli O157:H7 116 confirmed for Campylobacter 27 developed Hemolytic Uremic Syndrome (HUS) Seven people died; 4 of which were from E. coli Most cases: May 12-May 19; Earliest case: April 15 As of Aug. 17, 1460 cases; 198 confirmed for E. coli O157:H7; 119 cases of Campylobacter Source: The Investigative Report Of The Walkerton Outbreak Of Waterborne Gastroenteritis, October 10, 2000 October, 2000 Water and Walkerton, (c) Jason A. Tetro 2 1

2 Source: The Investigative Report Of The Walkerton Outbreak Of Waterborne Gastroenteritis, October 10, 2000 October, 2000 Water and Walkerton, (c) Jason A. Tetro 3 Source: The Investigative Report Of The Walkerton Outbreak Of Waterborne Gastroenteritis, October 10, 2000 October, 2000 Water and Walkerton, (c) Jason A. Tetro 4 2

3 WHAT WENT WRONG? During the outbreak, two wells provided the water to Walkerton At least one well contaminated; PUC notified History of one well showed potential for contamination and turbidity Of 13 farms tested in the area (highest at-risk for runoff), 11 were positive for human pathogens Combination of flooding, ground drainage patterns, overwhelming turbidity and failed chlorination efforts led to the outbreak Source: The Investigative Report Of The Walkerton Outbreak Of Waterborne Gastroenteritis, October 10, 2000 October, 2000 Water and Walkerton, (c) Jason A. Tetro 5 Source: The Investigative Report Of The Walkerton Outbreak Of Waterborne Gastroenteritis, October 10, 2000 October, 2000 Water and Walkerton, (c) Jason A. Tetro 6 3

4 Escherichia coli Normal human and animal flora found in gut Some E. coli acquire virulence genes Verotoxigenic E. coli (VTEC) family are able to kill Vero cells; cause bloody diarrhea; can cause hemolytic uremic syndrome (HUS) Serotypes of E. coli are determined by their somatic (O) and flagellar (H) antigens October, 2000 Water and Walkerton, (c) Jason A. Tetro 7 E. coli O157:H7 Member of the VTEC family of E. coli Known as hamburger disease 230 people consumed contaminated hamburger in Washington State, 1993 Causes bloody diarrhea in most individuals Children are most at risk of developing HUS HUS: caused by verotoxin; causes acute renal failure and anemia in ~10% cases of children Case rate is lower in adults October, 2000 Water and Walkerton, (c) Jason A. Tetro 8 4

5 Sources of E. coli O157:H7 Cattle and manure are primary sources 9.5% in cows; 24.7% for calves in Ont. Farm-level presence: 41-50% in Ontario Soil and surface/ground water in Ontario Usually associated with runoff from farms which have improperly spread manure: Application rates not low enough to avoid any immediate runoff Application on steep slopes Failure to avoid any large storms within two days post-application Failure to monitor tile drain and other outlets Can survive, multiply and remain infectious Source: The Investigative Report Of The Walkerton Outbreak Of Waterborne Gastroenteritis, October 10, 2000 October, 2000 Water and Walkerton, (c) Jason A. Tetro 9 Campylobacter Mainly foodborne disease spread by consumption of improperly cooked chicken meat Found in low numbers in feces of cattle Can survive, multiply and remain infectious in soil and water Causes severe abdominal cramping, diarrhea (sometimes bloody), nausea and vomiting Not as problematic as E. coli O157:H7 October, 2000 Water and Walkerton, (c) Jason A. Tetro 10 5

6 Who s At Risk Of Campy? Primarily a foodborne disease Consumption of improperly cooked chicken meat Improper foodhandling Waterborne disease infrequent Poor or no chlorination Mainly ground and recreational surface waters Well water is most frequent source of contamination October, 2000 Water and Walkerton, (c) Jason A. Tetro 11 Wells Provide access to groundwater aquifers Can be bored or dug A number of regulations exist to control well design and safety October, 2000 Water and Walkerton, (c) Jason A. Tetro 12 6

7 Well Design Source: Ministry of the Environment, Ontario Must have a well cap Must have an upslope to mouth Formation seal of grout, concrete, bentonite, clay or other overburden materials Stabilizer made of sand, gravel or overburden materials All joints and other seals must be waterproofed and must prevent leaching from soil October, 2000 Water and Walkerton, (c) Jason A. Tetro 13 Well Testing Wells should be tested for any health risk Microbiological Pesticides/PCB Inorganics/Lead Volatile Organics Nitrate Wells can be tested by government or private laboratories Intervals between testings vary depending on size of well Microbiological testing for individual wells: twice a year Larger waterworks: 16/month Positive tests must be dealt with immediately by the owner Approximate Cost per year for LARGE waterworks: $4, October, 2000 Water and Walkerton, (c) Jason A. Tetro 14 7

8 Problems with Wells Proximity to farms Walkerton s contaminated well was adjacent to cattle farm Flood waters If the upslope is compensated, water will flow into well Turbidity Many wells will accumulate soil and other particulates leading to turbidity (i.e. nutrients) October, 2000 Water and Walkerton, (c) Jason A. Tetro 15 Prevention Chlorination The best method to kill/inactivate microbiological organisms Scalable from small containers to large water treatment plants Use of ordinary household bleach is effective for ind. wells Other Treatments Filters (turbidity/colour/sulfur smell/iron) Water distillers/reverse osmosis UV light, candle filtration, ozonation October, 2000 Water and Walkerton, (c) Jason A. Tetro 16 8

9 Disinfection of Well Water with Bleach (Approx. 5.2% Hypochlorite) Depth of water in well Casing diameter of 15 cm (drilled well) Casing diameter of 90 cm (dug well) New well* Existing well* New well* Existing well* 1.0 m 100 ml 20 ml 3.2 L 0.6 L 3.0 m 300 ml 60 ml 9.8 L 2.0 L 5.0 m 500 ml 100 ml 16.5 L 3.0 L 10.0 m 1000 ml 200 ml 32.0 L 6.5 L Source: Health Canada Well Water Treatment and Maintenance October, 2000 Water and Walkerton, (c) Jason A. Tetro 17 Regional Municipality of Ottawa- Carleton Source: RMOC Water Division Water is taken from the Ottawa River at two plants: Lemieux Island and Britannia 20 pumping stations and 14 reservoirs (mixes both sources) A multi-step process is used to: Remove colour Remove turbidity Remove biologics (algae, bacteria, viruses) Approx. 168,000 water-quality tests are performed every year Compared to Ontario gov t request for ~200 tests per year for large waterworks (Discussion paper: Protecting drinking water for small waterworks in Ontario, August 9, 2000) October, 2000 Water and Walkerton, (c) Jason A. Tetro 18 9

10 Water Purification Flow Chart for RMOC Source: RMOC Water Division October, 2000 Water and Walkerton, (c) Jason A. Tetro 19 Summary of Water-Quality Tests, million litres of drinking water were treated and sent to customers; 168,000 tests performed 1 of 1393 turbidity tests failed and resolved No organics/inorganics/radioactives were detected or were detected at levels far below the guidelines for Drinking Water Quality Source: RMOC Water Division October, 2000 Water and Walkerton, (c) Jason A. Tetro 20 10

11 Summary of Water-Quality Tests, 1999 (cont d) 11,680 bacteriological tests were performed 1 location was found positive for bacteria Further tests showed no pathogens System was flushed, disinfected and retested with a negative result Source: RMOC Water Division October, 2000 Water and Walkerton, (c) Jason A. Tetro 21 SUMMARY Walkerton was a combination of poor engineering, poor weather, poor well maintenance, poor monitoring and poor information gathering and release There are numerous problems that can affect water quality and continue to cause problems (i.e. TCE in Carleton Place) RMOC has a highly effective water treatment and wastewater treatment program that will be effective until 2021 October, 2000 Water and Walkerton, (c) Jason A. Tetro 22 11

12 CAN WALKERTON HAPPEN HERE? Never say never Carrollton, Georgia outbreak of Cryptosporidium (1987) Cabool, Missouri outbreak of E. coli O157:H7 (1989/90) Milwaukee oubreak of Cryptosporidium (1993) Toxoplasmosis outbreak (Victoria, British Columbia, Canada (1995)) Sydney, Australia "event" of "Cryptosporidium" (1998) At best estimates, the risk of such a large outbreak here in Ottawa- Carleton is low October, 2000 Water and Walkerton, (c) Jason A. Tetro 23 REFERENCE INFORMATION De Villiers, M. Water. Stoddart Publishing, Toronto, Canada, 1999 Ontario Ministry of the Environment: Regional Municipality of Ottawa- Carleton Ontario Clean Water Agency Bruce-Grey- Owen Sound Health Unit Spellman, FR. The Science of Water: Concepts and Applications. Technomic Publishing Co, Lancaster PA, 1998 October, 2000 Water and Walkerton, (c) Jason A. Tetro 24 12

13 SEPTIC TANKS Septic Tanks are designed to accumulate solid waste Liquid waste is expelled into the environment Soil becomes unsafe (up to 1 million microbes per L and perhaps more) Minimum distances between septic tanks and wells are established and guidelines exist (15 m from bed) Most minimums are not sufficient and need to be increased (i.e. 30m) Septic tanks, like wells, are to be monitored and maintained by the owner October, 2000 Water and Walkerton, (c) Jason A. Tetro 25 October, 2000 Water and Walkerton, (c) Jason A. Tetro 26 13

14 Distribution Box/Bed for Septic Systems October, 2000 Water and Walkerton, (c) Jason A. Tetro 27 WATER AVAILABILITY Approximately 1.4 billion cubic kilometres of water in total Approximately 97% is salt water 2% are contained in frozen ice caps and glaciers 1% is considered fresh and running Canada holds 5.6% of that 1% Around 784,000 km 3 Ottawa- Carleton uses m 3 a day Equivalent to approx. 125 km 3 /year A drop in the bucket? October, 2000 Water and Walkerton, (c) Jason A. Tetro 28 14

15 Wastewater Treatment Larger cities, including Ottawa-Carleton, have Wastewater Treatment Facilities Water and biosolids are separated in various tanks which help to settle out solids Water is cleaned as best as possible over 8-10 steps and returned to the water supply (usually downstream of the uptake) Solids are accumulated and sent for land application or landfill October, 2000 Water and Walkerton, (c) Jason A. Tetro 29 TREATMENT OF WASTEWATER A. Influent B. Coarse Screen C. Grit Removal D. Primary Settling E. Chemical Addition F. Aeration Tanks G. Final Settling H. Disinfection I. Water Testing J. Sludge Transfer K. Digestion L. Dewatering M. Biosolid Transfer October, 2000 Water and Walkerton, (c) Jason A. Tetro 30 15

16 Three day conference on guaranteeing Safe and Clean Water Guest Speaker: Murray McQuigge from the BGOSHU Total cost: $ per person October, 2000 Water and Walkerton, (c) Jason A. Tetro 31 16