The Use of Human Health Risk Assessment as a Tool in the Assessment of Reclaimed Municipal Wastewater

Transcription

1 The Use of Human Health Risk Assessment as a Tool in the Assessment of Reclaimed Municipal Wastewater Karen Phillipps, M.Sc., DABT Intrinsik Environmental Sciences Inc., Calgary, AB Presentation at Watertech, Kananaskis, AB April 22, 2015

2 Summary Overview Methods Results Outcome

3 Overview What is Risk Assessment? The Risk Assessment Paradigm Established and recognized framework Can be applied to many issues to evaluate potential risk

4 Overview Increasing concern regarding the sustainability of public water supplies for drinking water, industry and agriculture Unique development (by Harmony) proposed in Springbank area in Rocky View County: Self-contained municipal wastewater treatment plant (WWTP) Proposed use of reclaimed water for irrigation of golf course and some green spaces within development

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6 Overview Plant Design (by Urban Systems) WWTP Grit Removal Flow equalization Screening Anoxic and aerated bioreactors Membrane filtration UV light Storage pond Natural biodegradation (Sept May) Pre-irrigation treatment Chlorination (May Sept) Irrigation Golf course and green spaces (May Sept) Chlorination (Continuous)

7 Overview of System Key features and issues: Reclaimed water rich in nutrients will be used as primary irrigation water source, and mixed with raw Bow River water under certain circumstances No wastewater discharge to surface water only land irrigation Current wastewater irrigation guidelines in Alberta require setbacks between the irrigated area and various land uses of 15 to 30 metres Is no-setback or a smaller setback possible and feasible? Risk assessment requested by Alberta ESRD and Alberta Health before the approval for the WWTP could be issued Concern about potential for human exposure to reclaimed water

8 Overview Scope of Intrinsik work: Evaluate the potential for adverse health effects in relation to direct human contact with reclaimed water Gain a better understanding of the California Title 22 requirements related to Recycled Water and other available water quality criteria Understand the potential for impacts tp local groundwater quality Evaluate various water quality parameters to aid ESRD in the identification of relevant monitoring parameters

9 Proposed Harmony Plant Specifications as of July 2014 Parameter Carbonaceous biochemical oxygen demand (CBOD 5 ) (mg/l) Fecal coliforms (CFU/100 ml) After Treatment/ Before Storage After Storage/ Before Irrigation < 10 (Median) < 10 (Median) < 20 (Maximum) < 20 (Maximum) 0 (Median) 0 (Median) 14 (Maximum) 14 (Maximum) No measured data available only wastewater treatment plant specifications Total coliforms (CFU/100 ml) Thermotolerant coliforms (CFU/100 ml) E. coli (CFU/100 ml) Not detected (Median) Not detected (Median) 200 (Maximum) 200 (Maximum) Not detected (Median) Not detected (Median) 200 (Maximum) 200 (Maximum) Cyanobacteria Microcystin (µg/l) Not applicable 40 Total suspended solids (TSS) (mg/l) < 5 Turbidity (NTU) < 2 (Average) 5 (Maximum) Chlorine residual (mg/l) 0.5

10 Methods Identification of Exposure Pathways Spray drift PLANTS Key Pathways: Inhalation of spray drift 1. Direct skin contact 2. Inhalation 3. Incidental ingestion Dermal contact spray drift Ingestion of garden produce Dermal contact

11 Methods Comparison with California Title 22 California Title 22 requirements for tertiary recycled water (unrestricted access) Reference: California Department of Public Health Regulations Related to Recycled Water. Title 22 Code of Regulations.

12 Methods Water Quality Criteria Comparison Intrinsik evaluated existing criteria from: Alberta ESRD Alberta Health Australia British Columbia Health Canada State of Nevada United States Environmental Protection Agency World Health Organization

13 Methods Hazard Assessment How can all of the exposure pathways be evaluated? No measured data in a hypothetical system exposure difficult to quantify Completed screening-level human health risk assessment based on estimated water quality after treatment and poststorage Two general categories of water quality criteria evaluated: Agricultural (landscaping, crops for human consumption) Recreational (swimming, secondary contact)

14 Agricultural Guidelines Alberta Guidelines for Municipal Wastewater Irrigation (2000) CBOD 5, fecal coliforms, total coliforms, TSS Alberta Environmental Quality Guidelines for Alberta Surface Waters (2014) Agricultural land use: fecal coliforms, E. coli US EPA Guidelines for Water Reuse (2012) Non-food crops (pasture, soil): CBOD 5, fecal coliforms, TSS, chlorine Food crops (raw): CBOD 5, fecal, total and thermotolerant coliforms, E.coli, turbidity, chlorine Australian Guidelines for Water Recycling (2006) E.coli, TSS Observation: lack of available criteria or guidance for cyanobacteria or related toxins. Agricultural irrigation systems seem to not involve storage ponds

15 Recreational Guidelines Alberta Nuisance and General Sanitation Regulation (2012) Alberta Environmental Quality Guidelines for Alberta Surface Waters (2014) BC Municipal Wastewater Regulation (2012) Health Canada Canadian Guidelines for Domestic Reclaimed Water (2010) Health Canada Guidelines for Recreational Water Quality (2012) US EPA Guidelines for Water Reuse (2012) Australia Australian Guidelines for Water Recycling (2006) State of Nevada General Criteria for Preparing an Effluent Management Plan

16 Results Quality of proposed reclaimed water met requirements for most bacteriological parameters Some areas for additional consideration: E. coli Cyanobacteria and microcystin Turbidity Chlorine residual level

17 Results Expected Quality Reclaimed water: < 14 CFU/100 ml of fecal coliform and 200 CFU/100 ml of E.coli The fecal coliform content meets ESRD guideline of 100 CFU/100 ml Proposed E. coli content (maximum 200 CFU/100 ml) exceeds it ESRD guideline is an interim Canadian Council of Ministers of the Environment (CCME) value derived for the consumption of raw product no additional information or context available

18 Sidebar Toxicology Moment Cyanobacteria (blue-green algae) Can produce toxins that can cause liver damage in humans and livestock under certain conditions Most common toxin is microcystin Production of toxins is difficult to predict or qualitatively evaluate 30-50% of blooms don t produce toxins Health Canada suggests that all cyanobacterial blooms be assumed toxic Some potential for microcystin accumulation in plants and food chain transfer Regulated in recreational waters due to potential for accidental ingestion, inhalation and skin contact while swimming

19 Results Cyanobacteria/Microcystin The proposed concentration of microcystin of 40 µg/l exceeded current criteria from Alberta and Health Canada for recreational water (20 µg/l) Health Canada also has requirement for total cyanobacteria (<100,000 cells/ml)

20 Results California Title 22 Comparison Regulation does not provide guidance for CBOD 5, cyanobacteria/ microcystin or TSS Proposed turbidity of reclaimed water greater than what is required by California Turbidity must be < 0.5 NTU (Maximum) and must be less than 0.2 NTU 95% of the time for microfiltered water that is not coagulated Recent critical review by US National Water Research Institute (2012) found that the California turbidity requirements were not clear California Title 22 regulations not a great fit for this project due to design differences

21 Results Chlorine Residual Proposed chlorine residual of 0.5 mg/l exceeded the US EPA Water Reuse Guidelines for unrestricted urban re-use, impoundments, and the irrigation of food crops (raw and other) Proposed residual is equivalent to the CCME aquatic life criteria Not a direct concern to human health influences bacterial quality of water through disinfection Risks between mitigating human health and potential for adverse aquatic health effects from higher residual chlorine should be balanced

22 Evaluation of Indicator Organisms Focused on markers of potential human pathogens in recycled, recreational or drinking water as they relate to the protection of human health Monitoring of specific types of bacteria (other than coliforms), viruses or protozoa is not routine Indicator organisms serve as sentinels for other organism their presence indicates a potential contamination of the water Conclusion: proposed monitoring of fecal coliform, E.coli and thermotolerant coliforms generally consistent with government agencies for agricultural, recreational and other water uses

23 Conclusions There was no single guideline or framework that completely evaluated potential multi-route exposures to reclaimed water Multi-faceted screening-level human health risk assessment approach helped fill knowledge gaps The proposed reclaimed water quality met majority of criteria exceptions for cyanobacteria/microcystin, fecal coliform, E. coli, turbidity and chlorine residual Selected indicator organisms for monitoring are sufficient Monitoring and mitigation strategies recommended for consideration

24 Thank you Intrinsik: Nino Devdariani, Claire McAuley Urban Systems: Chris Town Harmony/Bordeaux: Elise Harlick

25 Environmental Science and Engineering See article in current edition!

26 Outcome Risk assessment reviewed by ESRD and Alberta Health First risk-based evaluation of municipal wastewater irrigation assuming a zero m setback in Alberta Wastewater treatment plant Approval issued in October 2014 Approval has conditions for: Reducing potential human exposure through access restrictions and irrigation times Water quality monitoring Cyanobacteria management Reporting

27 Thank you Intrinsik: Claire McAuley, Nino Devdariani UrbanSystems: Chris Town Harmony Developments Inc.: Elise Harlick