Determining Minimum Treatment Requirements for Well-Based Municipal Systems

Transcription

1 Determining Minimum Treatment Requirements for Well-Based Municipal Systems Monica B. Emelko, Ph.D. Department of Civil & Environmental Engineering University of Waterloo Aziz Ahmed, P.Eng. Supervisor, Approvals and Licensing Safe Drinking Water Branch

2 Terms of Reference for the Evaluation of Water Quality to Determine Minimum Treatment Requirements for Subsurface Water Supplies Monica B. Emelko, Ph.D. Department of Civil & Environmental Engineering University of Waterloo Aziz Ahmed, P.Eng. Supervisor, Approvals and Licensing Safe Drinking Water Branch

3 Overview GUDI Terms of Reference* Review Project Charter GUDI and associated treatment requirements New ToR: Determining Treatment Requirements for Subsurface Water Supplies Process of Revision Next Steps * Terms of Reference, Hydrogeological Study to Examine Groundwater Sources Potentially under Direct Influence of Surface Water, Oct. 2001

4 Project Charter GUDI Terms of Reference Review 2001 GUDI Terms of Reference: old and outdated No change in legislation clarification & transparency Ensure that scarce tax dollars are spent to provide treatment and undertake monitoring, that promotes positive public health outcomes Update to incorporate most current consensus of science Objective: to ensure appropriate treatment of well water is provided by determining whether a communal well requires additional treatment beyond a minimum level of primary disinfection

5 Objective of Proposed TOR: Same as 2001 GUDI TOR To reduce the risk to human health attributable to disease causing microorganisms, Ontario has specified minimum treatment requirements for water works. To ensure appropriate treatment is provided, the principal objective of this hydrogeological study is to determine whether a communal well should be managed as a supply under the direct influence of surface water. Intention: To ensure appropriate treatment to reduce pathogen risk. (also as indicated in Reg. 170/03)

6 Proposed TOR Framework OLD ToR Treatment Requirement NEW ToR GW 2 log virus Category 3b 4 log virus Category 3a GUDI EF 2log Cryptosporidium 3 log Giardia 4 log virus Category 2 SW/GUDI 2log Cryptosporidium 3 log Giardia 4 log virus Category 1 Current TOR Proposed TOR

7 Process of Revision Collaborative, multi stakeholder group, composed of municipal system owners, consultants, academic experts, and cross divisional ministry staff

8 Key Science Foundation There is no easy distinction between GW and SW. Many factors impact pathogen survival/transport in the subsurface. A different focus in conceptual transport models is required. (dissolved/aqueous compounds particles/pathogens) Pathogen transport/survival in the subsurface cannot be predicted. Not all indicator data inform us in the same way. (occurrence survival transport) Hydrologic events are critical so is appropriate monitoring. All systems should have basic disinfection because of virus risk. Most significant well related pathogen risk in Ontario: fecal contamination with bacteria and viruses. Appropriate treatment is based on appropriate water quality measures.

9 Proposed TOR Framework OLD ToR Treatment Requirement NEW ToR GW 2 log virus Category 3b GUDI EF 4 log virus Category 3a 2log Cryptosporidium 3 log Giardia 4 log virus Category 2 lower threshold lower cost higher threshold higher cost SW/GUDI 2log Cryptosporidium 3 log Giardia 4 log virus Category 1 Current TOR Proposed TOR

10 Proposed TOR Framework traditional hydrogeology + microbiological water quality + particle counts OLD ToR Treatment Requirement NEW ToR GW 2 log virus Category 3b GUDI EF SW/GUDI 4 log virus Category 3a 2log Cryptosporidium 3 log Giardia 4 log virus 2log Cryptosporidium 3 log Giardia 4 log virus Category 2 Category 1 health risk + microbiological water quality + surface connectivity (AVCP) water quality (turbidity+doc) Current TOR Proposed TOR

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13 Potential Vulnerability to Contamination by Protozoa This drives the monitoring requirement during the Stage 2 AVCP. ONLY pertains to new systems.

14 Next Steps Completion of final edits of draft document Opportunity for stakeholder comments Finalization of document Implementation through conditions of municipal drinking water licenses and permit

15 Acknowledgments CANADIAN WATER NETWORK Bernadette Conant, Alex Chik MUNICIPAL STAKEHOLDERS City of Guelph, City of Waterloo, RM of Halton, OWWA CONSULTANTS C3Water, Stantec, Tim Lotimer MINISTRY OF ENVIRONMENT Operations Division, Drinking Water Management Division, Environmental Sciences and Standards Division SCIENTIFIC COMMUNITY Monica Emelko, Dave Rudolph, Marylynn Yates, Nicholas Ashbolt, Pierre Payment, Benoit Barbeau, Jennifer Clancy, Ronald Harvey