Dettah Sewage Lagoon and Wetland Study
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Dettah Sewage Lagoon and Wetland Study Final Report March 2015 – 14-1094 i Table of Contents Acronyms and Abbreviations Executive Summary 1.0 Introduction 1 2.0 Background Information 1 2.1 Current Facilities and Operational Practices .......................................................................... 1 2.1.1 Current Water Licence and Surveillance Network Program (SNP) ......................................... 2 2.2 Previous Studies .................................................................................................................... 3 2.3 Other Relevant Existing Information ....................................................................................... 3 2.4 CCME Strategy for Managing Municipal Wastewater Effluent in the North ............................. 4 3.0 Population Projections and Facility Sizing 5 3.1 Population projections ............................................................................................................ 5 3.2 Sewage Generation Estimates ............................................................................................... 5 3.3 Runoff Contribution to Lagoon Inflow ..................................................................................... 7 4.0 Site and Infrastructure Investigation 8 4.1 Lagoon Cell and Wetland ....................................................................................................... 8 4.2 Truck Access and Turn-Around Pad ...................................................................................... 9 4.3 Berms and Flow Control Mechanism .................................................................................... 11 4.4 Honey Bag Pit ...................................................................................................................... 14 4.5 Influent Analysis ................................................................................................................... 14 4.6 Treatment Performance and Effluent Analysis ..................................................................... 14 4.7 Sludge Depth and Composition Analysis ............................................................................. 17 5.0 Assessment of Site/System for Future 20 5.1 Cell Volume and Capacity .................................................................................................... 20 5.2 Projected parameter loadings .............................................................................................. 21 5.3 Current Sludge Levels and Future Desludging Events ......................................................... 21 5.4 Access Road and Discharge Pad Upgrade .......................................................................... 22 6.0 Summary of Recommendations 23 7.0 Preliminary Costing Estimate 25 8.0 Closure 29 9.0 References 30 Dettah Sewage Lagoon and Wetland Study Final Report March 2015 – 14-1094 ii Appendices A Sewage Lagoon Drainage Basin 1 B Discharge Area Photos 1 C Sewage Lagoon Profiles 1 D Sludge Sample Locations 1 E Future Expansion Lagoon Sections/Profiles 1 F Analytical Results 1 Figures Figure 1: Overview of Dettah Lagoon and wetland drainage course ........................................................................... 2 Figure 2: Historical and projected population growth for the community of Dettah ..................................................................................................................................................... 5 Figure 3: Aerial view of lagoon highlighting berm and flow control structures and surface runoff flow direction ............................................................................................ 11 Figure 4: Lagoon Depth and cross sections with containment berm on east side. ................................................................................................................................................ 20 Tables Table 1: Monitoring Program SNP station Locations and Sampling Requirements ......................................................................................................................................... 2 Table 2: Water Licence Sampling Requirements for SNP 1586-4 .............................................................................. 3 Table 3: Projected Population and Yearly Sewage Generation .................................................................................. 6 Table 4: Raw wastewater Influent Characteristics ....................................................................................................... 14 Table 6: Treatment Performance Parameter Concentration Reductions at the inlet and outlet of the wetland treatment area .................................................................................. 15 Table 7: TP Trigger Ranges for Canadian Lakes and Rivers (CCME 2004) ............................................................... 16 Table 8: Parameter Analysis of Lagoon Sludge Sample ............................................................................................. 17 Photos Photo 1: View of Dettah Lagoon Cell from Southwest corner ..................................................................................... 8 Photo 2: View of Lagoon Cell from west bank ............................................................................................................. 9 Photo 3: Erosion of sandy shoreline on east Bank ...................................................................................................... 9 Photo 4: Truck pad and discharge chutes into lagoon ................................................................................................ 11 Dettah Sewage Lagoon and Wetland Study Final Report March 2015 – 14-1094 iii Photo 5: Exfiltration berm on North End of Lagoon ..................................................................................................... 12 Photo 6: Original Outflow Control Structure ................................................................................................................ 13 Photo 7: Heavy vegetative growth along the periphery of the discharge zone ............................................................ 18 Photo 8: Heavy vegetative growth along the periphery of the discharge zone ............................................................ 19 Dettah Sewage Lagoon and Wetland Study Final Report March 2015 – 14-1094 v Acronyms and Abbreviations CCME Canadian Council of Ministers of the Environment ENR Environment and Natural Resources EC Environment Canada MACA Department of Municipal and Community Affairs MVLWB Mackenzie Valley Land and Water Board NWT Northwest Territories YKDFN Yellowknives Dene First Nation MWWE Municipal Wastewater Effluent NPS National Performance Standard EDO Effluent Discharge Objective CWQG Canadian Water Quality Guidelines FAL Freshwater Aquatic Life WSER Wastewater Systems Effluent Regulations BOD5 5-day Soluble Biological Oxygen Demand FC Faecal Coliforms NH3-N Total Ammonia as Nitrogen NO3-N + NO2-N Nitrate + Nitrate as Nitrogen TKN Total Kjeldahl Nitrogen TP Total Phosphorus TSS Total Suspended Solids VSS Volatile Suspended Solids Dettah Sewage Lagoon and Wetland Study Final Report March 2015 – 14-1094 vii Executive Summary Dillon Consulting Limited (Dillon) was retained by the Yellowknives Dene First Nation (YKDFN) to complete an assessment on the condition and performance of the existing sewage treatment lagoon. This study was conducted to assess future capital planning to support facility rehabilitation and/or upgrades to prepare for the upcoming expiration of the water licence issued by the Mackenzie Valley Land and Water Board (MVLWB). The report contained herein focuses on the Operation and Maintenance activities of the lagoon and the biological treatment within, and around, the sewage treatment facility. Treatment of municipal wastewater in lagoon-based wastewater treatment plants (WWTPs) is common in Canada and very cost effective for smaller communities where land is available and inexpensive. Lagoons are generally inexpensive to build, simple to operate and, when properly designed and maintained, produce a treated effluent that can be discharged to the environment with minimal impact. Lagoon – (Also known as waste stabilization pond) An in-ground earthen basin used for the treatment of wastewater by natural process involving the use of algae and bacteria. They can be classified as aerobic, aerated, facultative and anaerobic. Natural aeration process is enhanced by mechanical devices in aerated lagoons. This best practice provides owners and operators of lagoon-based WWTPs with information to optimize the performance and capacity of their facilities. Through optimization of lagoon operations, the owner can potentially: realize additional capacity; meet more stringent discharge requirements through improved effluent quality; reduce energy use and cost; reduce chemical use and cost; and reduce odour emissions. Lagoon-based WWTPs can be designed in a variety of configurations but all depend largely on natural physical and biological processes to achieve treatment. Improvements in the performance of lagoons can be achieved through: operational and minor design changes that may improve the flow patterns and mixing in the lagoon; modifying the flow scheme in multi-cell lagoon systems; As discussed, evidence of effluent short-circuiting to the point of lagoon discharge is apparent within the lagoon and immediately outside the discharge point of the lagoon. The effluent analysis