SEWAGE TREATMENT FACILITY UPGRADES STP REVIEW FINAL REPORT

Transcription

1 SEWAGE TREATMENT FACILITY UPGRADES STP REVIEW FINAL REPORT PREPARED FOR: VILLAGE OF FORT SIMPSON PO BOX 438 FORT SIMPSON, NT X0E 0N0 PREPARED BY: STANTEC ARCHITECTURE LTD. PO BOX 1777 YELLOWKNIFE, NT X1A 2P4 MARCH 1, 2012

2 EXECUTIVE SUMMARY The Village of Fort Simpson is currently under an Environment Canada Inspector s Directive to improve the effluent from the sewage treatment facility. The purpose of this project is to assist the Village with achieving compliance with that Directive by providing an engineering report with a five-point scope of work: SCOPE OF WORK ITEM 1 Review and comment on the existing treatment facilities and equipment with respect to their current and intended future use and capacity. 1. The existing treatment facilities are currently meeting the water licence requirements but as yet have not passed the LC50 test. 2. If the Canada wide CCME standards are adopted for the North in 2014, this facility cannot meet them. 3. The primary treatment equipment is operating above capacity both hydraulically and organically. 4. A significant positive impact on operational capability was achieved with the introduction of the detritus screen. 5. As the primaries are corroding from within, their continued life is very limited. 6. The sand filters do not work and have not since commissioning. 7. The Waterloo filters do not work as they cannot accept present volumes or solids loading. Therefore, it is our professional opinion that the existing process cannot provide future use and capacity. SCOPE OF WORK ITEM 2 Review and comment on the completed and proposed changes to the primary treatment process prior to biological treatment. Following are the completed changes: 1. Reduction of solids loading by using a detritus screen; 2. Relocation of chemical inputs for alum and poly; 3. Improved chemical pumping; 4. Maintaining a deeper sludge blanket; and 5. Not operating the unit as a pressure vessel (it is not rated as such but was set up to operate in this way before the current operator was hired). All these changes have resulted in safer operation, improved treatment, more consistent treatment and fewer treatment upsets. However, it is unlikely that this state can be sustained for much longer given the internal corrosion of the C-CETS Units. SCOPE OF WORK ITEM 3 Review and comment on the use of the biofiltration process and media from the Waterloo biofilters as the sole biological treatment process with respect to nutrient (ammonia) conversion and removal. The Waterloo filters were not designed to accept 100% of the daily flow, nor to accept solids loadings that exceeded 20 mg/l. As a result they cannot perform any biological treatment for this plant. SCOPE OF WORK ITEM 4 Review and comment on the current and proposed use of the existing ultraviolet disinfection process and equipment with respect to its viability as the sole disinfection method to meet current and future discharge requirements. Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON

3 The current UV disinfection process has been upgraded from 3 to 5 light fixtures. This should provide continued treatment for many years to come. Therefore, it is our professional opinion that UV should remain the disinfection process of choice for Fort Simpson s wastewater. SCOPE OF WORK ITEM 5 Recommend the currently proposed process viability and validate that both the capital and operational costs are minimized, affordable and sustainable based on the approved financial data the Village will provide, and/or Recommend an alternate process and/or equipment that better meets the Village s needs to achieve the mandated treatment levels yet still respects the Village s budgetary capacity regarding capital and operation costs. Various treatment processes were evaluated against criteria that included: Limited financial capability and a limited budget. The capital budget is $1.5M; Incorporate the existing infrastructure to the greatest extent possible; There is little opportunity to expand the existing building which is located in a residential area; The existing building has dedicated areas that cannot be easily altered; The building interior foot print is so limited that a full-sized biological process cannot fit inside; and Anything coming into the building is potentially limited by a 10 x10 access door. In summary, no treatment process but the current process could meet these criteria. Further, the estimated cost of an alternate treatment process ranged from $3M to $6M, depending on the process. Additional Rationale for Recommended Option Discussions with Environment Canada During the period up to January 26, 2011, work with Environment Canada Inspectors was completed to develop terms of reference and guidelines that addressed the Inspector s Direction in light of CCME and Environment Canada regulatory efforts. On January 26th, the Inspectors provided direction as follows: Operate the facility competently and consistently to meet the terms and conditions of the Water Licence issued by the Mackenzie Valley Land and Water Board; Address the process so that it shows improvement in the effluent quality; Report on March 31, 2012 the methodology and schedule to meet the conditions; and Continue to provide updates on the 15th of each month. Environment Canada advised that if: The above was followed; and The schedule outlined in the report was met; and Competent, consistent operation was demonstrated, then Environment Canada should consider the Inspector s Direction to have been met. Confirmed by Environment Canada in subsequent correspondence, further discussion suggested that this could be done within the existing infrastructure and without the need to install new treatment processes to the existing facility. Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON

4 COST ESTIMATES OF THE SELECTED OPTIONS Considering the available budget and all the other factors, the option is to continue with physical/chemical treatment and to improve the operation. Item Est. Cost Sampling plant influent with an automated composite $ 5,000 sampler Maintaining and Improving Raw Sewage Quality $ 45,000 Reducing Infiltration $ 120,000 Increasing Flow Equalization $ 50,000 Improving Chemically Assisted Primary Treatment $ 400,000 Incorporation of Sand Filtration $ 120,000 Improving Overall Building Electrical, Mechanical and $ 300,000 HVAC Development of In-Plant Sludge Thickening; $ 115,000 Construction of a Remote Sludge Composting Facility; $ 100,000 Overall Upgrade and Building Code Compliance; $ 225,000 Preparation of Standard Operating Procedures; $ 25,000 Development of a Maintenance Management System; $ 50,000 and Development of an Environment Management $ 25,000 System. Development of an In-Plant Operator Training $ 25,000 Program; Total Estimated Cost $ 1,605,000 Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON

5 PROPOSED IMPLEMENTATION SCHEDULE Following is a generalized proposed implementation schedule for the proposed upgrades and improvements. For simplicity, end dates where appropriate are suggested for major milestones. Item Phase End Date Environment Canada Submission March 31, 2012 Approval May 30, 2012 Raw Sewage Sampling Sampling May 2012 Raw Sewage Quality Bylaw January 2013 Public Education On-going Reducing Infiltration Tender July 2012 Commission October 2012 Flow Equalization Tender September 2012 Improving Primary Treatment Design January 2013 Electrical, Mechanical and HVAC Commission September 2013 In-Plant Sludge Thickening Upgrade and Building Code Compliance Sand Filtration Pilot August 2012 Tender September 2012 Design January 2013 Commission September 2013 Remote Sludge Composting Facility Design July 2012 MVLWB Approval September 2012 Construction October 2012 Environmental Management System Tender June 2012 Development January 2013 Operation On-going Standard Operating Procedures Tender September 2013 Maintenance Management System Development December 2013 Operation On-going Operator Training Program Tender June 2012 Development December 2013 Operation On-going Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON

6 TABLE OF CONTENTS 1.0. INTRODUCTION BACKGROUND METHODOLOGY DEFINITION OF IMPORTANT TERMS PRESENT TREATMENT ORIGINAL DESIGN AND TREATMENT SCHEME CURRENT TREATMENT SCHEME SEWAGE FLOW RATES SEWAGE QUALITY REVIEW OF EXISTING TREATMENT FACILITY UNDER FUTURE CONDITIONS REVIEW OF MODIFICATIONS TO PRIMARY TREATMENT PROCESS REVIEW OF BIOFILTRATION PROCESS REVIEW OF DISINFECTION PROCESS REVIEW OF ALTERNATE DESIGN CONCEPT PREAMBLE SEQUENCING BATCH REACTOR (SBR) ROTATING BIOLOGICAL CONTACTORS (RBC) EXTENDED AERATION MEMBRANE (MBR) PHYSICAL / CHEMICAL TREATMENT DILUTION CONCLUSION AND PROCESS SELECTION DISCUSSION OF RECOMMENDATION PREAMBLE PLANT INFLUENT SAMPLING MAINTAINING AND IMPROVING RAW SEWAGE QUALITY CONT... Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON

7 8.4. REDUCING INFILTRATION INCREASING FLOW EQUALIZATION IMPROVING CHEMICALLY ASSISTED PRIMARY TREATMENT INCORPORATION OF SAND FILTRATION BUILDING ELECTRICAL, MECHANICAL AND HVAC BUILDING UPGRADES AND CODE COMPLIANCE DEVELOPMENT OF IN-PLANT SLUDGE THICKENING CONSTRUCTION OF A REMOTE SLUDGE COMPOSTING FACILITY PREPARATION OF STANDARD OPERATING PROCEDURES DEVELOPMENT OF A MAINTENANCE MANAGEMENT SYSTEM (MMS) DEVELOPMENT OF AN ENVIRONMENTAL MANAGEMENT SYSTEM DEVELOPMENT OF AN IN-PLANT OPERATOR TRAINING PROGRAM SUMMARY OF COSTS PROPOSED IMPLEMENTATION SCHEDULE Appendices Appendix A: Appendix B: Appendix C: Appendix D: Appendix E: Drawings Proposed Clarifier Proposed Sludge Press Data Summaries Environment Canada Correspondence Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON

8 1.0 INTRODUCTION 1.1 BACKGROUND The Village of Fort Simpson is currently under an Environment Canada Inspector s Directive to improve the effluent from the sewage treatment facility. The purpose of this project is to assist the Village in compliance with that Directive by providing an engineering report with the following work items: 1. Review and comment on the existing treatment facilities and equipment with respect to their current and intended future use and capacity; 2. Review and comment on the completed and proposed changes to the primary treatment process prior to biological treatment; 3. Review and comment on the use of the biofiltration process and media from the Waterloo biofilters as the sole biological treatment process with respect to nutrient (ammonia) conversion and removal; 4. Review and comment on the current and proposed use of the existing ultraviolet disinfection process and equipment with respect to its viability as the sole disinfection method to meet current and future discharge requirements; and 5. Recommend the currently proposed process viability and validate that both the capital and operational costs are minimized, affordable and sustainable based on the approved financial data the Village will provide, And/or Recommend an alternate process and/or equipment that better meets the Village s needs to achieve the mandated treatment levels yet still respects the Village s budgetary capacity regarding capital and operation costs. 1.2 METHODOLOGY REVIEW OF AVAILABLE INFORMATION During the preliminary stages of the project all relevant engineering reports, available specifications, drawings (made from previous works on the sewage system), and effluent sample results from the client were collected and reviewed. This review period included previous work completed in house SITE INVESTIGATION Ron Kent, P. Eng., undertook the site visit during the period November 28 to November 30, Several conversations took place with Mitch Gast, Plant Operator who has been involved with the sewage treatment system since Mitch provided information on volumes, population, and the like. Mitch also provided quotes for new equipment that he had reviewed; these were used in the cost estimate for this report. During the site visit, the available plant records were reviewed DISCUSSIONS WITH ENVIRONMENT CANADA During the period following until January 26th, 2011, several discussions were held with Environment Canada Inspectors to develop terms of reference and guidelines that addressed the Inspector s Direction. On January 26th, the Inspectors provided that direction as follows: Operate the facility competently and consistently to meet the terms and conditions of the Water Licence issued by the Mackenzie Valley Land and Water Board; Address the process so that it shows improvement in the effluent quality; Provide a report on March 31st, 2012 that includes the methodology and a schedule to meet the above conditions; and Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON PAGE 1

9 Continue to provide updates on the 15th of each month. Environment Canada advised that if: The above was followed; The schedule outlined in the report was met; and Competent, consistent operation was demonstrated, then Environment Canada should consider the Inspector s Direction to have been met. Further discussion suggested that this could be done within the existing infrastructure and without the need to install new treatment processes to the existing facility. 1.3 DEFINITION OF IMPORTANT TERMS The following terms are used throughout this report and are defined in alphabetical order below: Biofilter: CBOD: CCME: Decoupling Tank: Faecal Coliform: Hydraulic Loading Rate: Modification: Organic Loading Rate: A biofilter is one of several wastewater treatment technologies that use microorganisms. Not filtration in the truest sense of the word, wastewater flows through a packed bed and the pollutant transfers into a thin biofilm on the surface of the packing material. Microorganisms, including bacteria and fungi, immobilized in the biofilm, degrade the pollutant. Related technologies include biotrickling filters. Carboneous biological demand, previously identified as the five day biochemical oxygen demand. CBOD or BOD5 is considered to be the strength of sewage, is used to design sewage treatment components and treatment efficiency, and is used by regulatory agencies to determine compliance. Canadian Council of Ministries of the Environment. Provinces, territories and federal government have used the CCME forum to jointly undertake initiatives to address major environmental issues in Canada for more than fifteen years. Under this report, CCME would refer to the proposed effluent compliance limit national standards, to be implemented progressively, starting in 2012 or Decouple means to reduce or eliminate the coupling of one circuit or part to another. The decoupling tank stops the coupling of the Proteus unit to the units that follow. Bacteria of the coliform group are naturally present in the intestinal tracts and faeces of warm-blooded animals. They are associated with the presence of disease causing organisms in wastewater. For this report, the hydraulic loading rate is the rate at which liquid flows into a treatment process. A change that is different from the original design. Changing a smaller pump to a larger pump, because it is necessary, is a modification; changing a pump from one manufacturer to another is not. Modifications can be made that, for example, make operations easier. An example is bypass piping to isolate in-line sensors. This makes it easier to access the sensor for maintenance. That no bypass piping was included in the original design is unfortunate in some cases, but not a deficiency. For this report, the organic loading rate is the rate at which organic material, measured as CBOD, enters a treatment process. Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON PAGE 2

10 Phys/chem.: Sand Filter: SCADA: Septage: Sludge: Suspended Solids: Trickling filter: UV: Physical / chemical. In this report phys/chem. is the treatment of sewage by settling (defined as physical removal) through the addition of chemicals that promote settling (also known as sedimentation). The Proteus system (unit) uses phys/chem. as a treatment method. A process in which particles in water are removed by straining through sand as a porous media. Supervisory Control and Data Acquisition is a common process control application that collects data from sensors on the shop floor or in remote locations and sends them to a central computer to determine the control requirements and sends commands to control actuators. SCADA is a very broad umbrella that describes solutions across a large variety of applications. Concentrated solids from a septic tank The thicken solids removed from the wastewater. Defined in waste management, these are small particles of solid pollutants, both organic and inorganic, that resist separation by sedimentation. Also called TSS in this report. A treatment process in which wastewater is trickled over a porous bed of stones or other material covered with bacteria that break down the organic waste. Light in the ultraviolet violet (UV) portion of the spectrum is used for disinfection, to kill pathogenic (disease causing) organisms. Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON PAGE 3

11 2.0 PRESENT TREATMENT Primary treatment using a rotating drum screen was installed in approximately 1991 to upgrade a raw sewage outfall to the Mackenzie River. The drum screen was problematic from the beginning. During collection, raw sewage passed through a lift station and was then pumped into the facility. The pumps macerated the sewage and converted the majority of the solids from a suspended to a dissolved form. As a result, the drum screen was only able to remove the largest remaining solids and the facility was unable to meet effluent quality requirements. Further, screenings were collected manually, which became a health and safety hazard for the operators. It was also reported that odours from the facility upset nearby neighbours on a routine basis. In about 2001, the drums screens were removed and the building converted to a Proteus System. This system of proprietary technology included physical / chemical treatment using alum, followed by sand filters, Waterloo style biofilters, and UV disinfection. In the original design, approximately 68% of the phys/chem treated wastewater was to bypass the biofilters. Problems initially occurred during construction and installation of the treatment system. The General Contractor apparently completed most of the work; however, there were several deficiencies. These deficiencies and other issues have become the subject of litigation between the Village and the General Contractor, and between the General Contractor and his principal subcontractor. Since commissioning, some of the deficiencies have been addressed; while others have not. Additionally, in response to operational difficulties, some of which are a direct result of the raw sewage becoming stronger, the Village has made several modifications including a change in the process and the process treatment scheme. 2.1 ORIGINAL DESIGN AND TREATMENT SCHEME The original design of the treatment facility involved a physical / chemical treatment with the use of biofilters. The phys/chem (Proteus) portion of the facility was rated by the manufacturer at 435 m3/d (115,000 USGPD). The biofilters were rated by Proteus at 173 m3/d (120Lpm). In this design approximately 68 percent of the wastewater was planned to bypass the biofilters. This scheme was based on a mass balance analysis that assumed treatment rates through the various processes and then applied them to meet the licensed effluent quality (as required by the Mackenzie Valley Land and Water Board are listed in Table 2.1 on next page) with a stated safety factor. The proponent argued that it was unnecessary to design excess treatment capacity that would not be immediately needed. Table 2.1: Fort Simpson Licensed Effluent Requirements Parameter Licence Requirement to 2015 Total BOD5 120 mg/l Total Suspended Solids (TSS) 180 mg/l Faecal Coliform <105 CFU/dL 2.2 CURRENT TREATMENT SCHEME The current concept design is shown in Drawing C02-101, Detail 1; attached in Appendix A. In this design, only the new 3mm detritus screening equipment, the primary treatment process and an upgraded UV disinfection system are operational. The continuously backwashed sand filters have been removed from the process approximately in It is understood that the sandfilters were originally to be a multimedia rapid sand design; however, a single media continuous backwash type was supplied and installed. There was no explanation available in the plant documentation for this change. Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON PAGE 4

12 Operators were unable to operate the continuous backwash filters as intended; the filters were reported to have the sand wash out overnight. Consequently, the operators were unable to prevent the sand filters from washing out all the sand. In 2003, the use of the Fournier Sludge press was suspended. The operators found it difficult to operate the press as it blocked with such frequency that it had to be watched continuously during operation. The Village continues to pump out the sludge holding tank although the press remains in stores should it be required in the future. The primary treatment system was overloaded with solids and as a result passed a heavy solids load. Without the sand filters operational, the Waterloo filters failed as they received too many solids from the primary treatment process. 2.3 SEWAGE FLOW RATES POPULATION In 2011, the population of the Village of Fort Simpson is It is understood from previous work that the maximum population of the island is 1070 persons, while the population on the mainland comprises the remainder. Table 2.2: Fort Simpson Population Projections Community Fort Simpson 1,270 1,281 1,291 1,305 1,291 Currently, the island population fluctuates between 800 and 1000 persons with the population at the time of this study to be approximately 900 persons. The remainder, approximately 365, live on the mainland. Sewage originating on the island is piped; sewage originating on the mainland is trucked. The NWT Department of Statistics suggests that there will be very little population growth in the next 20 years. With in-fill capacity on the island and new homes being built on the mainland it will be difficult to accurately predict future sewage flows. This is further complicated as some mainland homes operate with a septic tank and leach field rather than a pumpout SEWAGE FLOWS Table 2.3: Trucked Water Sales Account Type Total Volume (m3) Average Monthly Volume (m3) Jan 1, Dec 15, 2011 Bulk Purchase Commercial 1, Government Industrial Residential 25,223 1,073 Village 93 4 Total (m3) 29,171 1, COLONY FORMING UNITS PER 100 MILLILITRES 2. SEBASTIEN GOYER, PERS COMM, DECEMBER 12, BERNIE SWANSON PERS COMM. NOVEMBER 29, SOURCE: NWT BUREAU OF STATISTICS 5. MITCH GAST, PERS COMM. DECEMBER 16, IBID 5, DECEMBER 22, 2011 Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON PAGE 5

13 Table 2.4: Metered Plant Discharges Daily Flow (m3) Average High Low Average Maximum day factor In 2009 water and wastewater meters where replaced and re-calibrated and it was determined that previous metering was erroneous. Therefore, only the most recent data will be used in this analysis. Comparing the trucked water sales and assuming that all this water returns as pumpout sewage, the average daily flow from the mainland is m3 (41 m3 rounded). Therefore, in 2011, the average daily contribution from the island is calculated to be 233 m3. Based on the 2011 population of 1,265 split as 900 and 365 between the island and the mainland respectively, these values equate to water use population equivalents of 259 Lpcd for the island and 112 Lpcd for the mainland. These values indicate that water use is within expected volumes. Such volumes do not suggest the abuse of conservations principals. By comparison, the average daily water consumption through Canada in 2004 was 329 Lpcd. The Consultant established two population distribution scenario for Fort Simpson, both limiting the maximum population (island plus land) at 1,305 people in 2025, as stated in Table 2.2 above: Current (2010) distribution would be maintained in 2025; in such a case, there would be 928 people on the island, and 377 people on land; the corresponding average day flow rate would be 283 m3/d; this is comparable to the period average daily flow rate (refer to Table 2.4 above); Population on the island would reach its historical (2005) peak of 1,070 people; land population would be only 235 people; that would correspond to a daily sewage flow rate of 304 m3/d. For the rest of the report, in order to take into account additional sewage associated with population growth, the Consultant retained the higher of the above, i.e. 304 m3/d. Maximum day flow rate is typically twice the average day flow rate. At Fort Simpson sewage system, the highest maximum day factor observed during the period was 166 (refer to Table 2.4 above). For design purpose, the Consultant recommends to use 2.0 as the maximum day factor. Corresponding design flow rate would be 608 m3/d; that would govern the design of the secondary biological process, if ever required. Peak hour flow rate typically represent at minimum 50% more than the maximum day flow, or three times the average day flow. The Harmon formulae establishes the peak factor as a function of the total serviced population, as follows: Peak hour factor = / (4 + P1/2), with P = serviced population in thousands For an ultimate population of 1305 people, peak hour factor would be Since the actual maximum day factor is consistently quite low in Fort Simpson, the Consultant recommends to use a lower, equivalent to 50% more than the highest historical maximum day factor, i.e. = 1.66 X 1.5 = 2.5 The corresponding peak hour flow rate would be 760 m3/d. That would govern the design of the low lift pumps, the screening unit, the primary treatment process, the secondary clarifier (if any), the UV system (if not biological tank is required), and all the chemical feed pumps. An alternate option to designing to the 760 m3/d peak hour flow rate is to increase the size of flow equalization such that a peak hour flow rate between 1.66 and 2.0 will can be used. 7. IBID 5 8. ENVIRONMENT CANADA WEBSITE Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON PAGE 6

14 2.4 SEWAGE QUALITY During December 2011 and January 2012, screened solids were collected, dried and weighed. It was determined that 13kg/day of dry solids were removed by the 3mm detritus screen. Raw sewage is extremely difficult to sample representatively. Sampling at this facility is further complicated by piped sewage, trucked sewage delivered weekdays from 8am to 5pm, and septage delivered intermittently. Raw sewage quality is an important consideration in the design of a treatment process. For this analysis, typical sewage concentration normal, as presented in Tables 2.5 and 2.6 on next page, will be considered. Those assumptions would have to be validated with actual raw sewage monitoring data. This implies to use composite sampler equipment, taking a smaller sample either on a time base or a flow pacing base (preferable) after screening. This would be done once every week, including the day prior to take a grab sample at plant effluent, for two to three months. Composite raw water sample should be collected at different day, in order to be representative of the entire week activity. Table 2.5 Typical Raw Sewage Normals Parameter (all in mg/l) Piped Trucked Septage Carboneous Biochemical ,480 Oxygen Demand Total Suspended Solids ,860 Total Suspended Solids ,027 volatile Ammonia/Nitrogen Total Kjeldahl Nitrogen Total Phosphorous Table 2.6: Average Treatment Results 2010/11 Parameter Licence Raw Sewage 2010 Final Effluent 2011 Final Effluent Requirement CBOD 120 mg/l 350 mg/l 84 mg/l 60 mg/l Total Suspended 180 mg/l 380 mg/l 50 mg/l 26 mg/l Solids (TSS) Ammonia Not required 43 mg/l 29.5 mg/l 22.9 mg/l Faecal Coliform <105 CFU/dL >3 x 106 CFU/dL 518 CFU/dL 235 CFU/dL ph Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON PAGE 7

15 2.4.1 DISCUSSION ABOUT EFFLUENT TOXICITY While the Water Licence is valid, and the effluent currently meets the licensed requirements on average, actions under the Fisheries Act take precedence. Currently, in addition to a reporting schedule, the Inspectors Direction requires a non-toxic effluent (read: passes an LC50 bioassay test). Un-ionized ammonia is often a primary culprit in municipal effluent toxicity. The level at which ammonia concentration (y) is acutely lethal to fish is a function of the ph of the effluent and can be calculated using the following equation : y = x (2.7183( x ph)) [Eqn 01] Toxicity increases with ph. In 2010, the highest ph recorded was 7.25; the average was In 2011, the highest ph recorded was 6.69; the average was Substituting 7.25 for ph as the worst case in equation 01 and solving: y = say 110 mg/l NH3-N This corresponds to a value for unionized ammonia from Emmerson et. al. (1975) at 10oC of x 110 = mg/l of unionized ammonia, lower than the value of 2mg/L generally consider to be the threshold of toxicity. Comparing the 2011 average value of 22.9 mg/l Emmerson corresponds to x 22.9 = mg/l of unionized ammonia. 9. MITCH GAST, PERS COMM.. JANUARY 17, WASTEWATER ENGINEERING: TREATMENT & REUSE 4ND ED, METCALF & EDDY. TABLE IBID 8 (ADJUSTED TO 120 LPCD) 12. GUIDE TO SEPTAGE TREATMENT AND DISPOSAL, EPA, TABLE ESTIMATED FROM NORMALS AS A PERCENT OF POPULATION 14. DETERMINED FROM LABORATORY RESULTS. 15. BASED ON A GEOMETRIC MEAN 16. BASED ON A GEOMETRIC MEAN 17. AMENDED DECEMBER 2, 2011 EC FILE NUMBER ENVIRONMENT CANADA, GUIDELINE FOR THE RELEASE OF AMMONIA DISSOLVED IN WATER FOUND IN WASTEWATER EFFLUENTS 19. EMERSON, K., R.C. RUSSO, R.E. LUND, AND R.V. THURSTON. AQUEOUS AMMONIA EQUILIBRIUM CALCULATIONS: EFFECTS OF PH AND TEMPERATURE, JOURNAL OF THE FISHERIES RESEARCH BOARD OF CANADA VOL. 32, P , 1975 Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON PAGE 8

16 3.0 REVIEW OF EXISTING TREATMENT FACILITY UNDER FUTURE CONDITIONS This section involves the review and commenting on the existing treatment facilities and equipment with respect to their current and intended future use and capacity as per scope of work item 1. The existing treatment facilities are currently meeting the water licence requirements but as yet have not passed the LC50 test (two have been conducted); however, future requirements may change once the CCME guidelines are adopted for the North. One can only speculate what they may be. If they are similar to the 2009 southern standards, the current facility will not be able to meet them. The primary treatment equipment does not appear to be achieving the manufacturer s stated capabilities. In addition, the actual sewage strength is twice as strong as what was anticipated in the original design application. Therefore, the system is operating above capacity both hydraulically and organically; however, the operator has been able to compensate to some extent and provide consistent operation with the use of alum and polyelectrolytes. A significant positive impact on operational capability was achieved with the introduction of the detritus screen. It removes approximately 13 kg/ day of solids >3mm, thus, removing the loading from the primary treatment component. Such a screen should remain in any future facility. This performance is within the expected normal operating range. As the primary treatment components are corroding from within, their continued life is very limited. Currently, the primary treatment is operating at 432 m3/d (300 Lpm) and is not capable of operating much beyond this volume. By comparison, the design flow rate for that unit should be 760 m3/d (not considering additional flow equalization). The sand filters do not work and have not been in use since commissioning of the system. Similarly, the Waterloo filters do not work as they cannot accept the present volumes or solids loading. Therefore, it is our professional opinion that the existing processes cannot provide adequate treatment or the required capacity for continued use. 20. WASTEWATER ENGINEERING: TREATMENT & REUSE 4ND ED, METCALF & EDDY. PAGE 454 Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON PAGE 9

17 4.0 REVIEW OF MODIFICATIONS TO PRIMARY TREATMENT PROCESS This section involves the review and commenting on the completed and proposed changes to the primary treatment process prior to biological treatment as per scope of work item 2. Following are the completed changes: 1. Reduction of solids loading by using a screen; 2. Relocation of chemical inputs for alum and poly; 3. Improved chemical pumping; 4. Maintaining a deeper sludge blanket; and 5. Not operating the unit as a pressure vessel (it is not rated as such but was set up to operate in this way before the current operator was hired). All these changes have resulted in safer operation, improved treatment, more consistent treatment and fewer treatment upsets; however, it is unlikely that this state can be sustained for much longer given the internal corrosion of the C-CETS Units. The proposed change is to remove these units and replace them with a conventionally designed primary treatment clarifier capable of 500 cubic metres per day. This proposal provides a familiar treatment process capable of meeting the water licence requirements. In order to provide some redundancy and back-up capability, for emergency and normal scheduled maintenance downtime, the Consultant recommends that flow equalization be increased. If this is not possible, then the peak flow design flow of 760 m3/d should be used and the flow split between two clarifiers designed for 380 m3/d. Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON PAGE 10

18 5.0 REVIEW OF BIOFILTRATION PROCESS This section involves review and commenting on the use of the biofiltration process and media from the Waterloo biofilters as the sole biological treatment process with respect to nutrient (ammonia) conversion and removal as per scope of work item 3. The Waterloo filters were not designed to accept 100% of the maximum daily flow, nor to accept solids loadings that exceeded 20 mg/l. Since both the current flow and solids loading are in excess of the designed values, the Waterloo biofilters cannot perform any biological treatment for this plant. Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON PAGE 11

19 6.0 REVIEW OF DISINFECTION PROCESS This section involves the review and commenting on the current and proposed use of the existing ultraviolet disinfection process and equipment with respect to its viability as the sole disinfection method to meet current and future discharge requirements as per scope of work item 4. Table 6.1: Effluent Summary for Faecal Coliform Parameter Licence Requirement to 2010 Final Effluent 2011 Final Effluent 2015 Faecal Coliform <105 CFU/dL 518 CFU/dL 235 CFU/dL The current UV disinfection process has been upgraded from 3 to 5 light fixtures. This should provide adequate disinfection treatment for future years. There are four types of disinfection processes: chlorination using chlorine gas, chlorination using sodium hypochlorite solution, ozonation, and ultraviolet light. Chlorination has been practiced widely in the past. The benefits of using chlorine include: Kills bacteria effectively in particles of less than 1 mm; The disadvantages of chlorination include: When used in gaseous form, it is a very dangerous chemical to work with. There are many public health and occupational health and safety issues that must addressed; It cannot be operated by untrained or unskilled workers; It produces a toxic effluent; It produces by-products that are potentially carcinogenic and/or teratogenic; Where chlorination is used, dechlorination is mandatory; It is regulated under the Fisheries Act; Water Boards in the NWT have never allowed chlorination of municipal wastewater effluents. Ozone has been used in wastewater treatment for decades as a form of disinfection. Ozone is a very reactive gas that can oxidise bacteria, moulds, organic material and other pollutants. The benefits of using ozone include: Kills bacteria effectively. Oxidizes substances such as iron and sulphur so that they can be filtered out of the solution. There are no odours or residues produced from the treatment. Ozone converts back into oxygen quickly, and leaves no trace once it has been used. The disadvantages of using ozone include: Electricity is required to generate the ozone, thus making it an expensive system in a remote community such as Fort Simpson. Ozone treatment can sometimes produce by-products such as bromate that can harm human health if they are not controlled. Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON PAGE 12

20 Ultraviolet disinfection is nature s own disinfection/purification method. Commercially, it has been used for more than 50 years. Following are the advantages of UV disinfection: Environmentally friendly, no dangerous chemicals to handle or store, no problems of overdosing; Universally accepted disinfection system for potable and non-potable water systems; Low initial capital cost as well as reduced operating expenses when compared with similar technologies such as ozone or chlorine; Immediate treatment, no need for holding tanks, long retention times, etc; Low power consumption; No chemicals added to the water, therefore, no by-products; Automatic operation without special attention or measurement, operator friendly; Simplicity and ease of maintenance; Safe to use. No handling of toxic chemicals, no need for specialized storage requirements, no WSCC requirements; and Easy installation, only two water connections and a power connection. Implementation cost of UV may be an issue at most plant, but not in Fort Simpson, as it is the existing disinfection process. No other disadvantages for UV treatment in Fort Simpson exist with the exception of loss of treatment during power outages. Therefore it is our professional opinion that UV should remain the disinfection process of choice for Fort Simpson s wastewater. 21. DETERMINED FROM LABORATORY RESULTS. 22. COLONY FORMING UNITS PER 100 MILLILITRES Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON PAGE 13

21 7.0 REVIEW OF ALTERNATE DESIGN CONCEPT This section involves recommendations to the currently proposed process viability and validate that both the capital and operational costs are minimized, affordable and sustainable based on the approved financial data the Village will provide, and/or potential subsidies. Recommend an alternate process and/or equipment that better meets the Village s needs to achieve the mandated treatment levels yet still respects the Village s budgetary capacity regarding capital and operation costs. The following sections discuss the proposed changes to the sewage treatment system in Fort Simpson, as per scope of work item 5, with the assumption that current effluent criteria (120 mg/l CBOD, 180 mg/l TSS) would remain. 7.1 PREAMBLE Previously, Fort Simpson s treatment facility was a drum screen in a building designed for that purpose. The existing process was designed into the same building; however the building was enlarged to accommodate the additional components. Improving the existing process is limited by the following factors: The Village has a maximum budget of $1.5M; The continuing wish to incorporate the existing infrastructure to the greatest extent possible; There is little opportunity to expand the existing building which is located in a residential area; The existing building has dedicated areas that cannot be easily altered; Limited financial capability and a limited budget; The building interior foot print is so limited that a full-sized biological process cannot fit inside; Whatever process is chosen, the building will have to be heated to at least 10oC with a desired temperature of 15oC within the manned portion of the plant (control room, office, laboratory, toilet); Process rooms would be kept at minimum at 5oC to prevent raw sewage to cool down any further, to provide best treatment; and Anything coming into the existing building is potentially limited by a 10 x10 access door. 7.2 SEQUENCING BATCH REACTOR (SBR) An SBR is a suspended growth activated sludge process designed to operate under non-steady state conditions. An SBR operates in a batch mode with aeration and sludge settlement both occurring in the same tank. The major differences between SBR and conventional continuous-flow, activated sludge system is that the SBR tank carries out the functions of equalization aeration and sedimentation in a time sequence rather than in the conventional space sequence of continuous-flow systems. In addition, the SBR system can be designed with the ability to treat a wide range of influent volumes whereas the continuous system is based upon a fixed influent flowrate. Thus, there is a degree of flexibility associated with working in a time rather than in a space sequence. Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON PAGE 14

22 Table 7.1: SBR Design Paramaters for Intermitent Flow SBR Treatment Systems Parameter Flow Equalization Pretreatment Primary treatment SBR systems Required Hydraulic retention time (h) 9-30 Total cycle times (h)a 4-12 Secondary Clarification Sludge wasting Screening required Not required, however, cycle times are much longer. Required, could be performed within tank As needed to maintain performance The SBR is rejected as a process as it is too big to fit into the current building. Further, should it be simply added to the building, such a cost would be beyond the Village s financial capabilities. 7.3 ROTATING BIOLOGICAL CONTACTORS (RBC) RBCs are mechanical secondary treatment systems. The rotating disks support the growth of bacteria and micro-organisms present in the sewage, which break down and stabilise organic pollutants. To be successful, micro-organisms need both oxygen to live and food to grow. Oxygen is obtained from the atmosphere as the disks rotate. As the micro-organisms grow, they build up on the media until they are sloughed off due to shear forces provided by the rotating discs in the sewage. Effluent from the RBC is then passed through final clarifiers where the micro-organisms in suspension settle as sludge. The sludge is withdrawn from the clarifier for further treatment. Table 7.2: RBC Design Parameters Parameter Flow Equalization Pretreatment Primary treatment Hydraulic retention time (h) Secondary Clarification Sludge wasting RBC Systems Required Screening required Required less than an hour Required As needed to maintain clarifier performance Similar to the SBR, an RBC Process is rejected as a process as it cannot fit into the existing building. Further, should it be simply added to the building, such a cost would be beyond the Village s financial capabilities. 7.4 EXTENDED AERATION Table 7.3: Extended Aeration Design Parameters Parameter Extended Aeration Flow Equalization Required Pretreatment Screening required Mixed liquor suspended solids (mg/l) 2,000-6, EPA 625/R-00/008 ONSITE WASTEWATER TREATMENT SYSTEMS TECHNOLOGY FACT SHEET DILLON CONSULTING LIMITED, SEWAGE TREATMENT PLANT UPGRADES PRE-DESIGN REPORT, FEBRUARY 23, 2010 Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON PAGE 15

23 F/M load (lb BOD/d/ML VSS) Hydraulic retention time (h) 24 hours (typ) Secondary Clarifier Required Sludge wasting As needed to maintain performance The Extended Aeration Process is also rejected as a process as it cannot fit into the existing building. Further, should it be simply added to the building, such a cost would be beyond the Village s financial capabilities. 7.5 MEMBRANE (MBR) MBR s combine activated sludge with membrane filtration technology. The Village has already undertaken a feasibility study and determined that the process was not affordable. Thus, this process will not be discussed further. 7.6 PHYSICAL / CHEMICAL TREATMENT The Village sewage treatment system currently operates as a physical and chemical treatment system. Environment Canada has stated that it would be acceptable to continue to use this process, however, its operation and consistency must be improved. It is anticipated that this process can be upgraded within the budget and the building. 7.7 DILUTION Dilution of the effluent is an unacceptable method to reach licence limits. 7.8 CONCLUSION AND PROCESS SELECTION Considering the available budget and other relevant factors, the recommended option is to continue with physical/chemical treatment with modifications to improve the current operation. This is valid only if current effluent criteria remain. Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON PAGE 16

24 8.0 DISCUSSION OF RECOMMENDATION 8.1 PREAMBLE The items selected in this option are detailed in the following sections. These items were evaluated and recommended in due consideration of the directions from Environment Canada (discussed previously), the CCME s Canada Wide Strategy for the Management of Municipal Effluent, and the concerns of the INAC Inspector for the Village s Water Licence. Thus, not only will the process be upgraded, but so will the entire system from collection to discharge. These modifications are proposed as follows: Sampling plant influent with an automated composite sampler Maintaining and Improving Raw Sewage Quality; Reducing Infiltration; Increasing Flow Equalization; Improving Chemically Assisted Primary Treatment; Incorporation of Sand Filtration; Improving Overall the Building Electrical, Mechanical and HVAC; Development of In-Plant Sludge Thickening; Construction of a Remote Sludge Composting Facility; Overall Upgrade and Building Code Compliance; Development of an Environmental Management System; Preparation of Standard Operating Procedures; Development of a Maintenance Management System; and Development of an In-Plant Operator Training Program. 8.2 PLANT INFLUENT SAMPLING In order to design the plant upgrades properly, to make sure treatment capability would be adequate to meet effluent criteria at all time, it is crucial to develop better understanding of raw sewage characteristics. The current report has been elaborated on a series of assumptions that should be validated. Without that information, the Village is at risk of implementing equipment that would not meet effluent criteria at all time, or of oversizing equipment. To that effect, the Consultant recommends an automated composite sampler be rented for a two to three month period. Raw sewage would be sampled over a 24 hour period, at a different day of the week, every week, provided it is possible to deliver the sample to an independent lab by courier at the end of the 24-hour period. The sampler should also be used in the sand filter study discussed in section 8.7. Table 8.1: Cost of an Automatic Sampler Item Cost Estimate Automatic sampler $5,000 Subtotal $5,000 Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON PAGE 17

25 8.3 MAINTAINING AND IMPROVING RAW SEWAGE QUALITY Source control is an important part of the CCME s Canada Wide Strategy for the Management of Municipal Effluent. Municipalities must be also aware that if they accept a waste either actively or accidentally, they are responsible to treat it. Source controls are used to discourage the discharges of waste to the sanitary sewer and storm drainage systems that may pose a risk to workers and the public, damage infrastructure, hinder the efficiency of treatment facilities, degrade the quality of receiving waters, or affect the quality of biosolids. For these reasons it is important to control these inputs. These discharges may enter the system via surface runoff, service connections from buildings, or from truck discharges at treatment facilities. CCME s strategy recognizes source control as a mitigating factor in the Environmental Risk Assessment. There are two primary components for source control: a bylaw that sets limits to allow for the rejection of certain contaminants or excess concentrations of contaminants and allows for inspection, enforcement, and penalties; and a public education program. Table 8.2: Cost of Maintaining and Improving Raw Sewage Quality Item Cost Estimate Bylaw Review and Adoption $25,000 Public Education Program $20,000 Subtotal $45, REDUCING INFILTRATION Generally, the piped collection system is in good condition with only a slight observable difference between summer and winter flows. However, during spring freshet and break-up of the Mackenzie River, there are approximately 10 days when surface water can enter through various manhole covers as well as at the truck dump site on Mackenzie Drive. The proposed work to address the infiltration can be completed by Municipal staff and/or by contractors. Table 8.3: Cost of Reducing Infiltration Item Cost Estimate Full system inspection and spot leak repair $50,000 Truck dump repair $10,000 House site manhole cover behind SubArctic $5,000 Water proof 8 manhole covers $20,000 Installation of 3 Still Well Pumps $25,000 Still Well Code Compliance Upgrade $10,000 Subtotal $120, INCREASING FLOW EQUALIZATION The facility experiences high diurnal flows and also regularly receives trucked sewage. Additionally, a degree of infiltration enters the sewage stream in the spring despite best efforts to eliminate it. As a result, the existing flow equalization can be overwhelmed and operators have to refuse trucked sewage and/or surcharge sewers to Sewage Treatment FAcility Upgrades STP Review - Final Report VILLAGE OF FORT SIMPSON PAGE 18