Provision of Wastewater Treatment to Service the Huntsville Area: Receiving Water Assessment

Transcription

1 TECHNICAL MEMORANDUM Provision of Wastewater Treatment to Service the Huntsville Area: Receiving Water Assessment PREPARED FOR: COPY TO: District Municipality of Muskoka Project File PREPARED BY: CH2M HILL DATE: August 26, 2014 PROJECT NUMBER: Summary The District Municipality of Muskoka has developed effluent quality standards for its wastewater treatment plants (WWTPs) through a multi criteria analysis that considers a number of factors. The process followed in developing effluent quality standards for wastewater treatment within Huntsville is shown in Figure S.1. This standard will be used for upgrading the Golden Pheasant WWTP when the Mountview WWTP is decommissioned as per the recommendation of the Mountview WWTP and Huntsville Sewage Works Upgrades Schedule C Class Environmental Assessment. Figure S.1 Process for Developing Future Discharge Requirements 1

2 PROVISION OF WASTEWATER TREATMENT TO SERVICE THE HUNTSVILLE AREA: RECEIVING WATER ASSESSMENT Through this process, the District has strived to develop performance objectives that align with the District s Mission and Strategic Priorities relative to both effluent quality as well as the efficient use of energy and chemicals. To this end, Effluent Quality standards were established to accomplish the following: Meet or exceed regulatory requirements, including federal effluent quality regulations, which apply to all wastewater systems in Canada, and address un-ionized ammonia (UIA) and chlorine residuals. Protect all uses of the water body including recreation, drinking water supplies, and aquatic life. Protect human health and the natural environment. Provide long-term protection of Muskoka s economy which is highly dependent on pristine lakes and rivers. The entire process is documented in this Receiving Water Impact Assessment (RWIA) and is summarized as follows: Consideration of Current and Future Regulations: Regulatory considerations used as the basis for deriving effluent criteria include the MOE s policies governing the Provincial Water Quality Objectives (PWQO) and effluent non-toxicity requirements; the government of Canada s Wastewater Systems Effluent Regulations (WSER) requiring treatment standards to protect the receiver quality; Source Water Protection standards; and loading allocations established as part of the District s Lake System Health Program. Assimilative Capacity Assessment The Assimilative Capacity Assessment includes the development of background water quality conditions and execution of an outfall analysis. A site-specific waste assimilative capacity assessment was conducted for the Muskoka River and Fairy Lake, the receiving waters for the existing Mountview and Golden Pheasant WWTPs. The assessment proposes receiving-water based effluent requirements in accordance with Ministry of the Environment Procedure B-1-5. It is noted that based on the preferred alternative, the analysis was conducted under the assumption that the existing Golden Pheasant WWTP outfall would be utilized for the expanded facility when the Mountview WWTP is decommissioned. Additionally, as the existing outfall discharges into the Muskoka River at the mouth of Fairly Lake (and within the zone of influence of Fairy Lake), analyses were conducted with for both a river discharge (using a mass balance techniques) and a lake discharge (using CORMIX). The more conservative of the two was used as a basis for developing effluent standards. Standard methods of a desktop study were employed, including the determination of water quantity (7Q20 low flow statistic), upstream quality, and allowable effluent concentrations for non-toxic effluent with respect to UIA as well as the Provincial Water Quality Objectives (PWQO). A mixing zone analysis using CORMIX was also completed. Consideration was also given to climate change effects on the 7Q20 including the effect of severe weather events that would result in hotter/drier years with lower river flows. Based on the analysis of monthly river low flow and plant effluent flows, a minimum dilution ratio with river water was calculated at 11:1, and was and found to occur in July and August. Based on the mixing zone analysis using CORMIX, the initial dilution with assuming a lake based discharge in the near field region of the Golden Pheasant outfall diffuser is 48:1. The dilution ratio calculation that assumed a river based discharge was determined to be the governing parameter. Accordingly a dilution ratio of 11:1 was used. 2

3 M E M O R A N D U M PAGE 3 AUGUST 27, 2014 Ambient water quality in the Vernon Lake-Fairy Lake system, which includes the Muskoka River at Huntsville, was established using data from the following sources: District Municipality of Muskoka s Lake System Health Water Quality Monitoring Program; Provincial Water Quality Monitoring Network (PWQMN); and, special sampling programs undertaken as part of this EA. From this review, the Vernon Lake-Fairy Lake system including the Muskoka River at Huntsville was determined to be Policy 1 with respect to phosphorus, dissolved oxygen (DO), ammonia and E. coli (see Section 3.9 for Policy definitions). In-stream water quality impacts were determined for each parameter to support both the development of proposed Environmental Compliance Approval (ECA) effluent objectives, and the limits for the proposed rated capacity of 8,100 m3/d, the current combined rated capacity of the Mountview and Golden Pheasant WWTPs. Under the proposed preferred solution, all flows within the serviced urban area would be treated at the Golden Pheasant WWTP, and all treated effluent would be discharged through the plant s existing outfall. The analysis was designed to meet the PWQO concentrations after dilution at the 7Q20 low flow, and considered un-ionized ammonia (UIA) in relation to effluent toxicity. Best Practices for Recreational Water Uses In accordance with the goals of the existing regulations to protect the receiver and District s goals to maintain pristine lakes and rivers suitable for recreational and potable water uses, additional parameters to be regulated were considered and are discussed as follows: Denitrification for the Protection of Human Health - Ontario regulations for drinking water assign a Maximum Acceptable Concentration (MAC) for nitrate of 10 mg/l as N. It is also desirable to the District that the MAC be met within the mixing zone due to the significant recreational and bathing uses of the receiving water. Therefore, an effluent objective of 7 mg/l of nitrate-nitrogen was considered. Denitrification for the protection of Aquatic Life - Ongoing research shows that Biological nutrient removal removes nearly all acute toxicity, including UIA through nitrification. Therefore, there is a benefit to implementing a nitrifying and denitrifying treatment process with respect to minimizing effluent toxicity. During low flow periods impacts on fisheries are minimized. Denitrification has the added benefit of alkalinity recovery, thereby reducing chemical consumption and operating costs. Disinfection Levels for Protection of Human Health Disinfection levels must be provided to control E.Coli and other pathogen levels to support end of pipe quality suitable for swimming and bathing adjacent to the WWTP outfall. Contaminants of Emerging Concern As technology advances, a growing list of compounds that can have physiological effects on human beings and aquatic organisms are being detected in surface water. The MOE conducted a study to determine the world wide state of research on the removal of contaminants of emerging concern (CECs) at municipal WWTPs (CH2M HILL, 2010). The study s findings included the following: WWTPs that strive to remove ammonia (through nitrification) appear to eliminate most of the acute biological impacts of CECs WWTPs that strive to remove both ammonia and nitrate appear to eliminate most sub-lethal biological impacts of CECs Proposed Effluent Quality Standards 3

4 PROVISION OF WASTEWATER TREATMENT TO SERVICE THE HUNTSVILLE AREA: RECEIVING WATER ASSESSMENT Proposed effluent criteria shown in Table 1.1 for the Golden Pheasant WWTP were derived based on the discussion in the previous sections and were selected for the ECA enforcement limits. However the design objectives for the WWTP must achieve consistent daily performance to minimize receiver impacts rather than performance to achieve 30 day averages. Detailed calculations are provided in the raw water impact assessment (RWIA) found in Appendix D. Table 1.1 Proposed ECA Effluent Objectives and Limits at 8,100 m 3 /d Rated Capacity for Golden Pheasant WWTP Effluent Parameter Objectives Average Concentration (mg/l) Limits Average Concentration (mg/l) cbod Total Suspended Solids 5 10 Total Phosphorus Total Ammonia Nitrogen 0.14 (monthly average) 892 kg/y) 0.3 June to September 4 7 Nitrate 7 10 E. coli (Geometric Mean) < 2 80 Notes: ph of the effluent maintained between 6.0 to 9.5, inclusive, at all times mg/l = milligram per litre cbod 5 = carbonaceous 5-day biochemical oxygen demand 4

5 M E M O R A N D U M PAGE 5 AUGUST 27, Introduction The District Municipality of Muskoka (the District) strives to develop performance objectives that align with the regulatory objectives and the District s Mission and Strategic Priorities for effluent quality. In developing effluent quality standards, the District works to accomplish the following: Meet or exceed regulatory requirement suitable for protection of the receiver, including federal effluent quality regulations, which apply to all wastewater systems in Canada, and address un-ionized ammonia and chlorine residuals. Consider all uses of the water body including recreation, drinking water supplies, and aquatic life. Protect human health and the natural environment. Provide long-term protection of Muskoka s economy which is highly dependent on maintaining pristine lakes and rivers. As noted in Ministry of the Environment (MOE) Procedure B , discharge proponents are responsible for assessing the site-specific waste assimilative capacity of the receiving water body, and deriving receivingwater based effluent requirements from the assessment. Therefore, the District has adopted a multi-staged approach for developing effluent quality criteria, which includes the development of receiving-water based effluent standards in accordance with MOE procedure B , in addition to other considerations as summarized in Figure 1.1. Figure 1.1 Process for Developing Future Discharge Requirements 5

6 PROVISION OF WASTEWATER TREATMENT TO SERVICE THE HUNTSVILLE AREA: RECEIVING WATER ASSESSMENT Procedure B notes that the derived receiving-water based effluent requirements must be confirmed by MOE staff during the Pre-Application Consultation. For this study, a Pre-Application Consultation meeting was held May 22, 2014, during which the MOE provided guidance for developing the receiving water assessment (RWA). The purpose of this technical memorandum (TM) is to: document the RWA conducted for the Muskoka River and Fairy Lake, as well as for the receiving waters of Mountview WWTP and Golden Pheasant WWTP; and, to propose receiving-water based effluent requirements for the suggested solution. 2. Background The District owns and operates two WWTPs that serve the Town of Huntsville. The plants, Mountview and Golden Pheasant, discharge into Fairy Lake by way of the Muskoka River and Fairy Lake, respectively. Raw sewage is fed to each of the plants through sanitary sewers and sanitary sewage force mains located throughout the Town. The District is undertaking a Schedule C Class EA to plan for wastewater treatment capacity to service the Huntsville Area until the year Specifically, the study will: Verify information and the preferred solution (Phase 2) outlined in the 1989 EA; the EA s recommended solution was to centralize all wastewater treatment at the Golden Pheasant WWTP and decommission the Mountview WWTP; Strive to plan for sufficient capacity to support growth in the Town of Huntsville for the next 20 years; Establish treatment requirements for the WWTP to protect the receiving waters. 2.1 Existing Treatment Processes Figure 2.1 and Figure 2.2 present schematic diagrams of the current operations of Mountview WWTP and Golden Pheasant WWTP. The Mountview WWTP receives wastewater from two pumping stations, one of which is located on Princess Street (influent from Susan St., Centre St. and King St.) and the other on Hodges Lane (influent from Ferguson Rd., Hunters Bay Dr.). There is also the ability to receive additional wastewater from the Church Street pumping station (influent from Lake Dr. and Cliff Ave.). The Golden Pheasant WWTP receives wastewater from five pumping stations, located respectively on Coveside Drive, Church Street (influent from Lake Dr, and Cliff Ave.), Crescent Bay, Grandview Main, and Highland Drive (influent from Highland Hills, Ski club, Hidden Valley, Turner Dr., Greens, Birchcliffe, Lakeview, and Bayshore). Both the Mountview and Golden Pheasant WWTPs include primary and secondary treatment; Golden Pheasant also includes tertiary treatment. The secondary treatment at both plants was designed as a non-nitrifying, conventional activated sludge process. 6

7 M E M O R A N D U M PAGE 7 AUGUST 27, 2014 Figure 2.1 Schematic Representation of the Mountview WWTP Figure 3.2 Schematic Representation of the Golden Pheasant WWTP 7

8 PROVISION OF WASTEWATER TREATMENT TO SERVICE THE HUNTSVILLE AREA: RECEIVING WATER ASSESSMENT 2.2 Preferred Alternative The EA assessed five Alternative Solutions for the Huntsville Area, including the option to: 1. Decommission Golden Pheasant WWTP, route existing flows to Mountview WWTP, and expand the Mountview WWTP on its existing site (Muskoka River receiver); 2. Decommission Mountview WWTP, route flows to the Golden Pheasant WWTP via a new Mountview sewage pumping station (SPS), and upgrade and expand the Golden Pheasant WWTP (Fairy Lake receiver); 3. Replace the Mountview WWTP on the existing site, and upgrade the existing Golden Pheasant WWTP (Muskoka River and Fairy Lake receiver); 4. Decommission Golden Pheasant WWTP, replace the Mountview WWTP on the existing site, and build a new plant on a new site (Receiver TBD); and, 5. Decommission Mountview WWTP, upgrade the Golden Pheasant WWTP, and build a new plant on a new site (Receiver TBD). Design Concept 1 was discarded because of technical challenges and low public acceptability. Design Concept 4 and 5 were discarded due to increased risk of natural environmental impacts, low public acceptability, property acquisition costs, and high capital costs. Design Concept 2 and 3 were chosen to be carried forward due to their use of existing sites (lowered risk of natural environmental impact), as well as their technically feasibility. Design Concept 2 has also gained high public acceptance and is similar to the preferred Design concept selected in the 1989 EA. The shortlisted technologies along with the developed Design Concepts were presented to the public at the second Public Information Centre (PIC) which took place on April 15 th, A detailed evaluation of Design Concepts 2 and 3 was undertaken based on Natural, Technical, Social/Cultural, and Financial Criteria. Based on this evaluation, Design Concept 2 was selected and will be used as the basis for the Receiving Water Assessment in this study. The development and selection of a preferred Design Concept is documented in the Environmental Study Report. 2.3 Receiving Water Currently, effluent from the Mountview WWTP discharges into the Muskoka River, whereas effluent from the Golden Pheasant WWTP outfall discharges at the intersection between the Muskoka River and Fairy Lake. As such, effluent from the Golden Pheasant WWTP mixes with river water from the Muskoka River as well as ambient lake water discharging from Fairy Lake. The Golden Pheasant WWTP effluent is also used seasonally for irrigation at a local golf course. The preferred design concept as determined through the Class EA process entails centralized wastewater treatment at the Golden Pheasant WWTP and the use of the existing Golden Pheasant WWTP outfall for all discharges which is consistent with the 1989 EA scheme. Current effluent compliance criteria for the Mountview WWTP (formerly Huntsville WWTP) are specified in the ECA No and summarized in Table 2.1. Current effluent criteria for the Golden Pheasant WWTP are specified in the ECA No and summarized in Table

9 M E M O R A N D U M PAGE 9 AUGUST 27, 2014 Table 2.1 Existing ECA Effluent Criteria for Mountview WWTP at 3,640 m 3 /d Rated Capacity Effluent Parameter Objectives Average Concentration (mg/l) Limits Average Concentration (mg/l) cbod 5-15 TSS - 15 Total Phosphorus Table 2.2 Existing ECA Effluent Criteria for Golden Pheasant WWTP at 4,456 m 3 /d Rated Capacity Effluent Parameter Objectives Average Concentration (mg/l) Limits Average Concentration (mg/l) cbod TSS Total Phosphorus E. coli 80/100 ml n/a 2.4 Proposed Treatment Strategies for Receiving Water Assessment The preferred Design Concept as determined by this study is: Design Concept 2: Decommission the Mountview WWTP, route flow to the Golden Pheasant WWTP via a new Mountview SPS, upgrade and expand Golden Pheasant WWTP, and discharge all flows through the existing Golden Pheasant Outfall at the mouth of the Muskoka River. Through an evaluation of several treatment alternatives, Membrane Bioreactor technology with UV disinfection was selected as the preferred strategy for implementation at the Golden Pheasant WWTP. This treatment strategy will allow the facility to meet its performance requirements at a competitive lifecycle cost. It has also been successfully implemented at the District s Port Carling and Lagoon Lane WWTPs which are protecting similar receivers and water uses. Membrane bioreactor technology also supports the continued reuse of wastewater effluent for golf course irrigation. 9

10 PROVISION OF WASTEWATER TREATMENT TO SERVICE THE HUNTSVILLE AREA: RECEIVING WATER ASSESSMENT Figure 2.3 Preferred Treatment Strategy MBR with UV Disinfection 2.5 MOE Pre-Application Consultation A pre-application consultation meeting took place with the MOE on May 22, 2014, during which feedback was provided by the MOE on the development of effluent criteria for the Golden Pheasant WWTP. The feedback relevant to this assessment is summarized below, and the meeting minutes are attached in Appendix A. It was noted that the existing ECA for Mountview WWTP and Golden Pheasant WWTP state that the maximum total phosphorus (TP) loading between Mountview and Golden Pheasant WWTPs shall not exceed 892 kg/year. Any expansion of the Golden Pheasant WWTP should not allow for the direct bypassing of untreated wastewater to the Muskoka River, and this should be noted in the environmental study report (ESR). 3 Current and Future Regulations Regulatory considerations used as the basis for deriving site specific effluent criteria include: MOE s policies governing provincial water quality objectives and effluent non-toxicity requirements; Government of Canada s Wastewater Systems Effluent Regulations; Source Water Protection standards; and, loading allocations established as part of the District s Lake System Health Program 3.1 MOE Policy Status As noted in Water Management (1994), the MOE has two policies that relate to maintaining water quality in the Province: Policy 1: In areas which have water quality better than the Provincial Water Quality Objectives, water quality shall be maintained at or above the Objective. Policy 2: Water quality which presently does not meet the Provincial Water Quality objectives shall not be further degraded and all practical measures shall be undertaken to upgrade the water quality to the Objectives. The assimilative capacity of the receivers that abide by Policy 1 can be utilized subject to compliance with Provincial Water Quality Objectives. In general, the effluent limits established in accordance with Policy 1 will be less-stringent than those for Policy 2. However, particular site specific constraints, such as intake protection zones for water purification plants, municipal strategies and priorities, offsets of non-point source increases and stakeholder requirements, can prompt more stringent effluent objectives that would otherwise not be required by straight application of the policy status. This is of significance to the District of 10

11 M E M O R A N D U M PAGE 11 AUGUST 27, 2014 Muskoka as further degradation of the existing receiver is not acceptable due to the variety of water uses in the area. Additionally, MOE Procedure B provides procedures used to establish effluent based discharge criteria. This procedure was followed in developing effluent quality criteria. 3.2 Wastewater Systems Effluent Regulation (WSER) The Government of Canada published the Wastewater Systems Effluent Regulations (WSER) on July 18, These Regulations represent the country s first national standards for wastewater treatment and are established under the Fisheries Act. WSER include mandatory minimum effluent quality standards that can be achieved through the application of a secondary level of wastewater treatment, but require actual effluent criteria to be based on the receiver and end uses. The effluent standards specified in the WSER must be met by all municipal WWTPs that treat 100 m 3 /day or more of wastewater, and requires compliance by the end of 2020, 2030, or 2040, depending on the degree of risk associated with non-compliance. In addition, WWTPs in Ontario must comply with their ECAs or Certificate of Authorization (C of A) issued by the MOE. Currently, the MOE is in negotiations to assume jurisdiction of the federal standards, but this has not yet occurred. Currently, minimum WSER requirements include: Effluent standards: o o o o o Carbonaceous biochemical oxygen demand (cbod): 25 mg/l; Total Suspended Solids (TSS): 25 mg/l; Total Residual Chlorine (TRC): less than 0.02 mg/l; Un-ionized ammonia (UIA): 1.25 mg/l as N at 15 C; and Whole effluent toxicity: not acutely lethal. Required measurement and reporting of BOD, TSS, TRC, and UIA levels was mandated as of January 1, 2013, but compliance will not be enforced until January 1, Acute lethality testing using rainbow trout needs to be performed quarterly beginning January 1, 2015; compliance comes into effect at the same time. 3.3 Toxicity Requirements The MOE has a policy of ensuring that wastewater effluents are non-toxic with respect to aquatic life. Currently, the only parameters in municipal wastewater effluent which are considered when determining effluent toxicity are UIA and TRC. However, ongoing research is determining other contaminants that contribute to effluent toxicity. The speciation of ammonia between its non-toxic ionized form and its toxic un-ionized form depends on the water, ph and temperature. Typically, UIA (as nitrogen) is considered to be toxic to Daphnia Magna and rainbow trout at a concentration of 0.2 mg/l. In order to curve the effects of effluent toxicity caused by UIA to Daphnia Magna and rainbow trout, UIA concentrations of 0.2 mg/l or less should be achieved in the whole effluent. Since UIA is a function of ph and temperature, a 0.2 mg/l UIA-N fraction can only be achieved if the total ammonia-n in the effluent is at or is below the following concentrations: Winter, effluent temperature 4 degrees Celsius and ph 7.5: 46.1 mg/l total ammonia nitrogen; Summer, effluent temperature 26 degrees Celsius and ph 7.5: 8.8 mg/l total ammonia nitrogen. 11

12 PROVISION OF WASTEWATER TREATMENT TO SERVICE THE HUNTSVILLE AREA: RECEIVING WATER ASSESSMENT Table C-1 (Appendix C) lists the maximum effluent total ammonia nitrogen concentrations required to meet the end-of-pipe UIA toxicity requirement of 0.2 mg/l. Chlorinated wastewater effluents are regulated as a CEPA Toxic substance. Federal regulations require effluent TRC concentration to be 0.02 mg/l or less. 4 Best Practices for Recreational Uses and Watershed Protection 4.1 Source Water Protection The outfall of the Golden Pheasant WWTP is located in an area where consideration must be given to the protection of municipal and private water supplies. In order to protect these supplies, pathogen concentrations must be as low as practically possible, and the outfall must be located at a minimum of 1 km from any potential water intakes. Figure 4.1 presents the location of the existing outfalls of the Mountview and Golden Pheasant WWTPs, as well as the intake of the Fairyview Water Treatment. Additionally, this figure indicates locations of private water intakes all around Fairy Lake that require protection. In addition to municipal and private water supply protection, consideration must be given to nitrates and nitrites; nitrates and nitrites have an effect on human health at concentrations greater than 10 mg/l, as these concentrations can cause methemoglobinemia. In order to ensure that private water supplies are not impacted by these harmful effects, the general requirement is to ensure that nitrates/nitrites in vulnerable areas meet drinking water objectives. The number of private water supply intakes in the Muskoka River/Fairy Lake area suggest the need to provide suitable nitrate levels throughout the receiver. In brief, countless private water intakes surround Fairy Lake. Additionally, the areas surrounding the Golden Pheasant and Mountview WWTP outfalls are in the vicinity of waterfront homes and cottages that are extensively used for boating and swimming. As such, an end of pipe discharge nitrate/nitrate concentration of 7 mg/l is proposed. Additionally, an end of pipe E. coli objective of <2 cfu/100 ml is proposed for pathogens. Figure 4.1 Existing Intakes and Intake Protection Zones 12

13 M E M O R A N D U M PAGE 13 AUGUST 27, Lake System Health Requirements The District has a detailed Lake System Health Program to help protect recreational water quality within all of the surface waters of Muskoka. This Lake System Health Program includes a detailed lake health (water quality) model, which assesses impacts of stormwater, wastewater treatment plants, septic systems, and other potential sources of impact on water quality within the various lakes. According to the Lake system Health Program, Fairy Lake is designated as a moderately sensitive, under the threshold lake with respect to phosphorus. The Lake System Health Program has assessed the loading capacity of Fairy Lake at 892 kg/year, a total from both Mountview and Golden Pheasant WWTPs. Therefore, phosphorus discharges from the upgraded/expanded Golden Pheasant WWTP need to be maintained at or below 892 kg/yr. Current conditions in the Lake are a result of plant TP discharges of approximately 250 kg/yr. 4.3 Emerging Pollutants of Concern Historically, BOD 5, suspended solids, total phosphorus, ammonia, E. coli and ph have been regulated in municipal wastewater effluent. However, research has identified compounds such as fragrances, estrogens, pharmaceuticals and endocrine disruptors (EDP) that are not completely removed by some wastewater treatment plants, depending on design and operation. Although these parameters are not currently regulated, they may have potential impacts on human health as well as on river biota living downstream of the WWTPs. Further, these parameters could be subject to regulation in the future. The current state of research indicates that WWTPs that nitrify and denitrify provide a higher degree of removal of emerging pollutants of concern than WWTPs that do not nitrify. The District has taken a proactive approach to addressing contaminants of emerging concern, by implementing nitrification and dentrification wherever possible as an overall strategy to preserving receiving water quality. 5 Background Water Quality and Quantity The Golden Pheasant WWTP outfall is located at the mouth of the Muskoka River, which feeds into Fairy Lake and is within the zone of influence of the discharge of Fairy Lake. 5.1 Development of Dilution Ratios As analyses typically conducted for assessing a river discharge differ from those conducted for a lake discharge, two analyses were carried out: 1. River based discharge analysis: Determine 7Q20 Flows, Determine dilution ratio of 7Q20 flow to WWTP effluent flow (at design flow rate) Check that ratio (7Q20:WWTP Flow) is greater than the MOE recommended minimum of 10:1 2. Lake based discharge analysis: Utilize CORMIX modeling to determine initial mixing ratio Check that dilution ratio is greater than the MOE recommended ratio of 20:1 The governing scenario was used to assess the assimilative capacity of the receiving water and to determine the associated effluent standards. Wastewater Treatment Plant Flows The proposed hydraulic capacity of the Golden Pheasant WWTP (for the preferred alternative) for the planning period to 2036 is 8,100 m 3 /d. This represents the combined existing flows of the Golden Pheasant and the Mountview WWTP. Population and flow projections for the service area indicate that this capacity is sufficient to Further details are provided in the ESR. 13

14 PROVISION OF WASTEWATER TREATMENT TO SERVICE THE HUNTSVILLE AREA: RECEIVING WATER ASSESSMENT Development of 7Q20 Flows The Canada Water Survey operates a gauging station 02EB013 on the East River, which is the primary tributary discharging into Lake Vernon which then discharges into the Muskoka River at Huntsville. Data from 1973 to 2012 (40 years of data) was analyzed to determine the monthly 7Q20 low flows for the East River. These flows were then prorated by the added watershed drainage area of Lake Vernon relative to the combined watershed drainage areas for the East River and Lake Vernon. Table B-1 (Appendix B) lists the monthly 7-day average low flow. The data was then analyzed to determine the 7Q20 by method of moments and method of lowest observed, with the minimum of the two methods taken as the 7Q20 at the gauge location. The 7Q20 at the plant effluent discharge location was calculated as the gauge location 7Q20 pro-rated based on the ratio of the drainage areas (the gauge station has a drainage area of 610 km 2, and there is a draining area of 119 km 2 from Lake Vernon, giving a combined drainage area of 729 km 2 for the Muskoka River at Huntsville). Table B-2 (Appendix B) summarizes the 7Q20 data Development of Dilution Ratios River Discharge It may be assumed that treated effluent only mixes with river flow, and that the dilution ratio is thus a function of the natural flow in the river (at low flow conditions) relative to the amount of flow present from the WWTP. Figure 5.1 shows the 7Q20 low flow by month in comparison to the average flows in the river. Figure 5.2 presents the 7Q20 flows relative to the flows from the Golden Pheasant WWTP at the proposed expansion to 8,100 m 3 /d. Figure 5.3 presents the dilution ratios for the expansion of the Golden Pheasant WWTP based on the 7Q20 flows. The lowest dilution can be seen in July and August, at a 7Q20 of 1 m 3 /s, and a dilution ratio of 11:1. Figure 5.1 Muskoka River 7Q20 and mean flows Flow, m3/s Mean Flow ( ) 7Q20, m3/s Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month 14

15 M E M O R A N D U M PAGE 15 AUGUST 27, 2014 Figure 5.2 Muskoka River 7Q20 and relative to expanded Golden Pheasant WWTP monthly average flows of 8100 m 3 /day Flow, m3/s Golden Pheasant WPCP Muskoka River 7Q20, m3/s Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month 15

16 PROVISION OF WASTEWATER TREATMENT TO SERVICE THE HUNTSVILLE AREA: RECEIVING WATER ASSESSMENT Figure 5.3 Dilution ratios calculated for the proposed expansion to Golden Pheasant WWTP (8100 m 3 /day) based on 7Q20 flows in Muskoka River Dilution Ratio Month Development of Dilution Ratios Lake Discharge Scenario Effluent from the Golden Pheasant WWTP outfall discharges at the location where flow from the Muskoka River enters Fairy Lake and in the zone of influence of the Fairy Lake outlet. As such, effluent from the Golden Pheasant WWTP mixes with both river-water from the Muskoka River as well as ambient lake-water from Fairy Lake. The CORMIX expert system was used to estimate the receiver s mixing characteristics at the effluent discharge location, given the offshore distance of the diffuser and local depth. The existing Golden Pheasant WWTP outfall diffuser consists of ten diffuser ports, each with a m port diameter and spaced 4.6 m apart. The last diffuser port is approximately 100 m from the shore, and the water depth at the midpoint of the diffusers is 11.6 m under low lake levels. A current speed of 1 cm/s was used as a representative low current velocity condition based on drogue studies made as part of the 1989 EA (RV Anderson, 1989). A current speed of 0.5 cm/s was also run in CORMIX to identify dilutions at the lowest measured current speeds. The CORMIX results are listed in Table 5.1 for dilutions ratios with ambient lake-water from Fairy Lake. An initial dilution ratio of 48:1 is achieved at the end of the near-field region, which occurs at a distance of 58 m downstream of the diffuser in the direction of the current. 16

17 M E M O R A N D U M PAGE 17 AUGUST 27, 2014 Table 5.1 Dilutions calculated at different current Current Speed, cm/s Dilution at edge of Near-Field Region X, m Y, m Distance downstream from the diffuser midpoint Distance offshore from the diffuser midpoint a a a Values can be positive or negative and indicate distance from the midpoint of the diffuser in the onshore direction Figure 5.4 Plot of effluent plume as predicted using CORMIX Due to uncertainty associated with circulation patterns and correspondingly to the amount of lake water that mixes with river water at the location of the outfall, mixing calculations were based on the low flow of the Muskoka River only, and not on dilution with ambient water in Fairy Lake. Under this assumption, a minimum dilution of 11:1 is achieved during the critical July and August low flow periods, which meets the MOE s preferred minimum 10:1 dilution for rivers. While the dilution ratio of 11:1 will be used as a basis for developing minimum effluent quality standards to provide compliance with MOE regulations, the design will consider future climate change conditions that can result in extreme conditions such very low flow conditions or extreme wet weather events. 17

18 PROVISION OF WASTEWATER TREATMENT TO SERVICE THE HUNTSVILLE AREA: RECEIVING WATER ASSESSMENT 5.2 Development of Background Water Quality Conditions Background water quality conditions were determined to: 1. Assess the existing condition of the Muskoka River and Fairy Lake in terms of MOE standards (Policy status) and as well the Muskoka Watershed Council s classification of acceptable conditions with respect to Total Phosphorus. a) Policy status is determined by measuring background water quality conditions against PWQOs (see Table 5.2 below). b) The Muskoka Watershed council classifies a watershed as not stressed with respect to Total Phosphorus where ambient quality data indicates TP concentrations less than background + 50%, where background indicates TP concentrations had there been no development (as determined by the Watershed Council s modeling data). According to the Watershed Council s modeling data, the background TP concentration is 7.52 ug/l. 2. Develop a basis for determining effluent standards. Table 5.2 Summary of Provincial Water Quality Objectives Parameter Ammonia, Unionized Provincial Water Quality Objective 20 μg/l Dissolved Oxygen (Cold Water Biota) 8 mg/l at 0 C 7 mg/l at 5 C 6 mg/l at 10 C 6 mg/l at 15 C 5 mg/l at 20 C 5 mg/l at 25 C Total Phosphorus 20 μg/l Data Sources The methodology used in evaluating background water quality was to compare data from different sources and at different sampling locations throughout the Vernon Lake-Fairy Lake system. It was found that all data sources indicated water quality parameters were within the PWQOs and on this basis the receiving water was established as a Policy 1 receiver. Data from Vernon Lake was then used in calculations for the development of effluent quality requirements as outlined in section 6. Vernon Lake was used as the basis for these calculations because it is upstream of the Muskoka River at Hunstville and is therefore representative of background water quality upstream from the WPCP effluent discharge. Lake Partners The Lake Partner Program is Ontario s volunteer-based, water-quality monitoring program. Since 2002, the Ontario Ministry of the Environment has coordinated this lake monitoring program from the Dorset Environmental Science Centre (DESC). Each year, more than 600 volunteers monitor total phosphorus and water clarity in almost 550 inland lakes at over 800 sampling locations. Measurements of TP are available at various locations in both Vernon Lake and Fairy Lake going back to 2002 through this program and indicate ambient conditions within the PWQOs. 18

19 M E M O R A N D U M PAGE 19 AUGUST 27, 2014 District of Muskoka Lake System Health Water Quality Monitoring Program and Muskoka Watershed Council The District Municipality of Muskoka monitors lake health through recreational water quality testing, shoreline surveys, and technical assistance to lake associations interested in undertaking volunteer-based monitoring programs. Data is available for a broad array of water quality parameters from this monitoring program at key points throughout the Vernon Lake-Fairy Lake system including Hunter s Bay which lies directly between the two lakes and in the flow path of the Muskoka River at Huntsville. Data from this monitoring program indicate ambient conditions within the PWQOs with respect to TP, UIA and DO. Special Sampling Campaign Supplementary water quality monitoring points were established at strategic locations both up- and downstream of the two WWTP discharges. The points were sampled on March 2, 2014, under ice cover, and on May 26, 2014, during spring conditions. The purpose of the supplementary sampling was to confirm water quality data sets, as well as provide more site-specific water quality information upstream and downstream for the Mountview and Golden Pheasant WWTP outfalls. The sampling events confirmed the ambient TP and Total Ammonia Nitrogen (TAN) numbers provided from the Lake Partners Program Results ph and Temperature Water quality data from the District s Lake System Health Water Quality Monitoring Program indicate that average ph levels in the Vernon Lake-Fairy Lake system range between 6.35 and This is reflective of the low alkalinity conditions in the area. Temperatures in Hunter s Bay were found to range from 0 to 24 degrees Celsius. Total Phosphorus Data Results: Water quality data from the District s Lake System Health Water Quality Monitoring Program has indicated that average TP concentrations of 9.48 and 8.52 ug/l are found in Vernon Lake and Fairy Lake, respectively. This is within the same range as values measured by the Provincial Water Quality Monitoring Network station (average of 9.7 ug/l). The Lake System Health Water Quality Monitoring Program numbers are also consistent with concentrations measured in a sampling program undertaken as part of this study (average of 9 ug/l). Existing Receiver Condition: These numbers are below the PWQO for TP (20 ug/l) and indicative of Policy 1 conditions. Figure 5.5 presents the long-term trend in phosphorus concentrations in the receiving body of water for both Mountview and Golden Pheasant WWTPs. The figure displays a decrease in ambient TP concentration since Based on this information, the Muskoka River Fairy Lake system is consistent with Policy 1 with respect to TP. Existing ambient conditions within Fairy lake are within the Watershed Council s classification of not stressed (background + 50% which would amount to approximately 14 to 15 ug/l). Statistics for TP measurements from the available data sources are summarized in Table 5.3. Figure 5.5 presents the long-term trend in phosphorus concentrations in the receiving body of water for both Mountview and Golden Pheasant WWTPs. The figure displays a decrease in ambient TP concentration since

20 PROVISION OF WASTEWATER TREATMENT TO SERVICE THE HUNTSVILLE AREA: RECEIVING WATER ASSESSMENT Table 5.3 Summary of TP measurements in Vernon Lake TP, ug/l DMM Lake Partners This Study (1) Average th percentile N/A Note: (1) Special Sampling Campaign undertaken as part of this study. Insufficient samples to obtain 75 th percentile statistic. Figure 5.5 Long term trends in phosphorus concentrations and Secchi depths as reported by the District s Lake System Health Water Quality Monitoring Program Total Ammonia and Un-Ionized Ammonia Data Results: Both Total Kjeldahl Nitrogen (TKN) and TAN measurements were taken in a special sampling program as part of this project, where low concentrations were found in the range of 0.3 and 0.04 mg/l, respectively. TAN is not measured as part of the Districts s Lake System Health Water Quality Monitoring Program. However, TKN measurements made as part of the District s program can be correlated with TKN measurements made as part of the sampling program undertaken in this study. Both programs reveal average TKN concentrations in the range of 0.3 mg/l, from which a TAN concentration of 0.04 mg/l may be reasonably assumed as being characteristic of the ambient concentration for this parameter. Table 5.4 summarizes the ambient TKN and ammonia levels measured in Vernon Lake, as well as displays the resulting UIA concentrations. 20

21 M E M O R A N D U M PAGE 21 AUGUST 27, 2014 Existing Receiver Condition: Based on this information, the Muskoka River Fairy Lake system is consistent with Policy 1 with respect to UIA. Table 5.4 Summary of TAN, TKN and UIA in Lake Vernon Data Source Statistic TAN, mg/l TKN, mg/l TAN/TKN UIA, mg/l This Study (1) Average % (2) 75th percentile DMM Average th percentile Note: (1) Special Sampling Campaign undertaken as part of this study (2) A UIA/TAN ratio of was calculated based on the maximium ph and temperatures measured, respectively, 6.57 and 24 deg. C Dissolved Oxygen Data Results: Dissolved oxygen (DO) concentrations are measured at several locations throughout the Lake Vernon Fairy Lake system. As presented in Table 5.5, the DO levels do not indicate any unhealthy periods (low dissolved oxygen levels) which might threaten the ability of the lake to support sensitive species such as Lake Trout. Testing is always completed in late summer when DO levels are most vulnerable. Table 5.5 Summary of DO and Temperatures measured in Lake Vernon - Hunter s Bay during critical late summer period Parameter Average 25th percentile Temperature DO, mg/l Note: PWQO for Cold Water Biota at a temperature of 20 to 25 deg. C is 5 mg/l Existing Receiver Condition: Based on this information, the Muskoka River Fairy Lake system is consistent with Policy 1 with respect to DO Summary of Ambient Conditions As previously outlined, ambient water quality in the Muskoka River was assessed with respect to TP, ph, DO and UIA in comparison with PWQOs and the Watershed Council s thresholds for TP. Overall, results from the assessment indicate that the Vernon Lake-Fairy Lake system is consistent with Policy 1 for all mentioned water quality parameters and not stressed with respect to TP. Table 5.6 summarizes PWQO and policy statuses for UIA, DO, and TP. Overall, The Muskoka River Fairy Lake system is consistent with Policy 1 with respect to the aforementioned water quality parameters. 21

22 PROVISION OF WASTEWATER TREATMENT TO SERVICE THE HUNTSVILLE AREA: RECEIVING WATER ASSESSMENT Table 5.6 Provincial Water Quality Objectives for Phosphorus, Unionized Ammonia and Dissolved Oxygen Parameter Provincial Water Quality Objective Policy Status of Muskoka River - Fairy Lake System Ammonia, Unionized 20 μg/l Policy 1 Dissolved Oxygen (Cold Water Biota) 8 mg/l at 0 C Policy 1 7 mg/l at 5 C 6 mg/l at 10 C 6 mg/l at 15 C 5 mg/l at 20 C 5 mg/l at 25 C Total Phosphorus 20 μg/l Policy 1 6 Development of Effluent Quality Standards Proposed ECA effluent criteria for the Golden Pheasant WWTP expansion were derived based on criteria discussed in Section 1, which included: current and future regulations, best practices for the water uses, outfall analyses, research on mitigation of CECs, etc. As discussed above, a river based discharge was assumed as the governing condition. Accordingly, a dilution ratio of 11:1 was assumed for this analysis. Detailed calculations are provided in Appendix C. 6.1 Effluent ph and Temperature Effluent ph and temperature values were assumed based on data from similar activated sludge plants in the area. ph An average ph of 7.0 to 7.2 is typically desired in the bioreactors to maintain reasonable nitrification rates (Metcalf & Eddy Inc. 2003). A 75 th percentile ph of 7.4 was chosen to be protective of river water quality with respect to UIA. This value is based on effluent ph values measured at the Golden Pheasant WWTP in

23 M E M O R A N D U M PAGE 23 AUGUST 27, 2014 Figure th Percentile Effluent ph for the Golden Pheasant WWTP Effluent ph Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Temperature Effluent temperatures for the Golden Pheasant WWTP and Mountview WWTP are not recorded. Temperatures taken from an activated sludge plant of similar capacity in the northern Durham Region were used as representative values (Uxbridge WWTP), and ranged from 4 to 26 degrees Celsius. 23

24 PROVISION OF WASTEWATER TREATMENT TO SERVICE THE HUNTSVILLE AREA: RECEIVING WATER ASSESSMENT Figure th percentile effluent temperatures for Uxbridge WWTP Temperature, deg. C Un-ionized Ammonia Acute Toxicity Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec The effluent discharge to the Muskoka River must be non-acutely toxic at 100 percent effluent concentration (i.e. at end-of-pipe). TAN was determined using the UIA factor, which was calculated with the 75 th percentile effluent temperature and effluent ph (constant at 7.5) for each month and for both treatment alternatives. The results are summarized in Table 6.1. These concentrations are higher than those required to meet the PWQO after dilution (see discussion below), and can be achieved by a nitrifying facility. Therefore, achieving the PWQO after effluent dilution in the Muskoka River, and not acute toxicity, is the controlling condition for determining the effluent TAN limits. Table 6.1 Effluent TAN concentrations required to meet end-of-pipe non-toxicity requirements for UIA Month Temp* ph* pka UIA Factor NH3 for 0.2 UIA NH3-N for 0.2 UIA Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec *Typical numbers for activated sludge plants in Ontario used in gaining MOE approval 24

25 M E M O R A N D U M PAGE 25 AUGUST 27, 2014 PWQO after Dilution The effluent discharge must also achieve the PWQO for UIA of 0.02 mg/l ( mg/l as N) after dilution. A dilution ratio of 11:1 was used in this evaluation. Refer to Appendix C for the detailed calculations. Table 6.2 presents effluent TAN concentrations required to meet the PWQO for UIA after dilution, as calculated based on the Muskoka River at the 7Q20 low flow rate, as well as the proposed effluent criteria for TAN during the June to August period. The seasonal variation in TAN requirements for meeting PWQO is primarily due to seasonal changes in river flow as well as seasonal changes in river and effluent temperatures; the ph after mixing varies minimally. Table 6.2 Effluent TAN Required to Meet PWQO after Dilution at 7Q20 NH3-N required to meet PWQO for UIA after dilution, Month mg/l Jan 104 Feb 113 Mar 77 Apr 59 May 27 Jun 11 Jul 7 Aug 9 Sep 35 Oct 24 Nov 55 Dec Nitrate Source Water Protection Ontario drinking water regulations stipulate a MAC for nitrate of 10 mg/l as N. It is desirable to the District that the MAC be met within the mixing zone due to the significant recreational and bathing uses of the receiving water. For example, people routinely swim in this area. Therefore, an ECA objective of 10 mg/l of nitrate-nitrogen has been proposed. In order to achieve this objective, denitrification is required. However, denitrification would be considered regardless of this effluent parameter, due to the many ancillary benefits it provides to operations, including alkalinity recovery, reduction of CECs and improvements to sludge settlement. 25

26 PROVISION OF WASTEWATER TREATMENT TO SERVICE THE HUNTSVILLE AREA: RECEIVING WATER ASSESSMENT Protection of Aquatic Life The Canadian Council of Ministers of the Environment (CCME) published the final version of the Canadian Water Quality Guidelines for the Protection of Aquatic Life for nitrate ion in It notes a concentration of 3 mg/l as N for chronic exposure. Based on a dilution ratio of 11:1, effluent nitrate would need to be below 33 mg/l as N to fall below this threshold. Raw sewage TKN is not sufficiently high for effluent nitrate to exceed 30 mg N/L, and so this requirement would be achieved without denitrification. 6.4 Whole Effluent Toxicity Ongoing MOE research shows that biological treatment with a solids retention time (SRT) of 10 to 15 days removes nearly all acute toxicity, including UIA through nitrification. Biological nutrient removal (BNR) has been shown to be a further benefit beyond that of removing nearly all acute and chronic toxicity. Therefore, there is a benefit to employing nitrification / denitrification with respect to minimizing effluent toxicity. 6.5 Phosphorus The allowable TP loading to Fairy Lake was determined to be 892 kg/year, as calculated by the District s Lake System Health Program. For a rated capacity of 8,100 m 3 /d (associated with the expanded Golden Pheasant WWTP), a corresponding allowable effluent concentration was determined to be 0.3 mg/l. In addition to this loading allocation, effluent criteria must be assessed based on meeting PWQO after dilution in the receiving water, discussed in more detail below. PWQO after Dilution Effluent discharge must also achieve the PWQO for TP of 0.02 mg/l after dilution. A dilution ratio of 11:1 was used in this evaluation. Refer to Appendix C for the detailed calculations. Table 6.3 presents the calculated effluent TP concentrations required to meet the PWQO for TP after dilution, as calculated based on the Muskoka River at 7Q20 low flows, as well as on the proposed effluent criteria for TP on a loading basis. The seasonal variation in TP requirements for meeting PWQO is due to the seasonal change in river flow. In order to meet a TP concentration of 0.02 mg/l at the minimum dilution ratio of 11:1 and during the months of July and August, plant effluent will need to have a TP concentration of 0.14 mg/l or less. Effluent TP concentrations can be higher for other months of the year. Table 6.3 Effluent TP Required to Meet PWQO after Dilution at 7Q20 with an ambient TP concentration of 9.8 ug/l Month TP required to meet PWQO for TP after dilution, mg/l Jan 0.32 Feb 0.36 Mar 0.28 Apr 0.37 May 0.35 Jun 0.19 Jul 0.14 Aug 0.14 Sep 0.39 Oct