Sustainable Passive Wastewater Treatment
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Sustainable Passive Wastewater Treatment Troy D. Vassos, PhD FEC PEng Technical Director Integrated Sustainability (Calgary/Vancouver) AOWMA 22ND ANNUAL CONVENTION & TRADE SHOW “SUSTAINABLE PASSIVE WASTEWATER TREATMENT ” SEMINAR Outline Wastewater Characteristics Treatment Mechanisms Lagoon & Wetland Treatment Sustainability Considerations Lagoon Upgrade Examples Wastewater Characteristics and Treatment Domestic Wastewater URINE 30% 10%5% 35% 20% KITCHEN DISH BATH TOILET LAUNDRY SINK WASHER SHOWER 5% FAECES MISC BLACK WASTE GREY WATER WATER WATER Treatment BLACKWATER TREATMENT DISPOSAL or REUSE Toilets & Urinals Organic Solids Kitchen Sink Fats Oils & Grease Compost BIOSOLIDS Bacteria Soluble Organics Digest REUSE Nutrients (N & P) Laundry Toxic Organic & Inorganic DISCHARGE Pathogens Disinfect DISCHARGE Bath & Shower Screenings, Sand & Grit LANDFILL GREYWATER Treatment Levels & Objectives • Primary – remove coarse solids & FOG • Secondary – remove soluble BOD & TSS • Tertiary – remove N & P – remove turbidity (filtration) • Disinfection – remove microoganisms Treatment Summary 1. Lower temperature → more time 2. Complex organics → more time 3. Long solids retention is better than short 4. Mechanical treatment simply mimics and accelerates natural processes 5. Mechanical high capital and O&M cost 6. Passive Treatment – more land Bacteria & Wastewater Treatment Aerobic Bacteria Two general types of aerobic bacteria 1. Heterotrophic Bacteria Consume Organics – Needs oxygen in proportion to the amount of organics consumed – Rapid consumption & growth Aerobic Bacteria 2. Autotrophic Bacteria – uses CO2 as a carbon source – Nitrification: oxidize ammonia NH4 to form nitrite (NO2) and nitrate (NO3) – Not a significant process in lagoons due to limited bacteria in suspension – Lagoon nitrogen reduction generally due to algae growth Anoxic Bacteria • Anoxic: No oxygen, but other electron acceptors present (NO2, NO3, SO4 etc.) • Heterotrophic facultative bacteria digest and remove readily biodegradable soluble organics (electron donors) under anoxic conditions forming sludge, CO2 and nitrogen gas (N2) Anaerobic Bacteria • Anaerobic: No O2, NO2, NO3, SO4 etc. present • Heterotrophic anaerobic bacteria ferment and consume biodegradable soluble and particulate organic constituents forming sludge, CH4, CO2 and odour compounds • Very slow growing • Key condition for biological phosphorus removal Treatment Elements BOD REMOVAL TSS REMOVAL NH4 → NO3 AEROBIC RETURN BACTERIA WASTE BACTERIA Treatment Elements NITROGEN REMOVAL BOD REMOVAL TSS REMOVAL NO3 → N2 NH4 → NO3 RECIRCULATION LOOP ANOXIC AEROBIC RETURN BACTERIA WASTE BACTERIA Treatment Elements PHOSPHORUS NITROGEN REMOVAL REMOVAL BOD REMOVAL TSS REMOVAL PHOSPHORUS NO3 → N2 NH4 → NO3 RELEASE RECIRCULATION LOOP ANAEROBIC ANOXIC AEROBIC RETURN BACTERIA BACTERIA WITHOUT NO3 WASTE BACTERIA Lagoon Treatment Treatment Elements BOD REMOVAL TSS REMOVAL NH4 → NO3 AEROBIC RETURN BACTERIA WASTE BACTERIA Treatment Elements BOD REMOVAL TSS REMOVAL AEROBIC WASTE BACTERIA Treatment Elements BOD REMOVAL TSS REMOVAL TSS REMOVAL DUCKWEED HARVESTING N & P REMOVAL AEROBIC WASTE BACTERIA Facultative Lagoons O2 NH P AEROBIC WASTEWATER 4 ALGAE O2 10 NH3 (FAST) C NH4 P BACTERIA ANOXIC CO pH 2.0 m 2 – (FACULTATIVE) SLUDGE 5 1.5 ANAEROBIC NH4 (SLOW) Facultative Lagoon O2 NH P AEROBIC WASTEWATER 4 ALGAE O2 10 NH3 (FAST) C NH4 P BACTERIA ANOXIC CO pH 2.0 m 2 – (FACULTATIVE) SLUDGE 5 1.5 ANAEROBIC NH4 (SLOW) Lagoon Advantages • Achieves good treatment under cold climate conditions • Withstands high flow and organic loading fluctuations • Lower capital and operating cost than mechanical systems – Lower energy and Labour – Lower operator skill and attention – Easy to maintain Lagoon Disadvantages • Algae blooms affect TSS & BOD • Seasonal nitrogen removal (algae growth) • Limited phosphorus removal • Seasonal turnover and odours • Exfiltration concerns • Sludge accumulation & desludging • Land requirements Algae Water Quality Impact Algae Control Considerations NH4 P WASTEWATER ALGAE O2 C NH4 P CO2 Algae Control Considerations NH4 P WASTEWATER ALGAE O2 C NH4 P BACTERIA CO2 Algae Control Considerations NOT GENERALLY PRACTICAL NH4 P WASTEWATER ALGAE O2 C NH4 P CO2 Algae Control Considerations NH4 P WASTEWATER ALGAE O2 C NH4 P CO2 Algae Control Considerations NH P WASTEWATER 4 ALGAE O2 C NH4 P O2 BACTERIAO2 BACTERIA O2 O2 BACTERIA BACTERIA O AEROBIC 2 m 5.0 (FAST) O2 – 3.0 3.0 O2 Size Comparison – 3,800 m3/d (1 MGD) LAGOON SYSTEM LAND (m2) FACULTATIVE 667,000 PARTIAL-MIX AERATED 200,000 COMPLETE-MIXED AERATED 20,000 Wetland Treatment Constructed Wetlands N & P REMOVAL BY HARVESTING BACTERIA BOD REMOVAL AMMONIA NITRIFICATION Effluent Quality Requirements Wastewater Effluent Systems Regulations • Four “Prescribed Deleterious Substances” 1. 5-day Carbonaceous Biochemical Oxygen Demand (CBOD5) < 25 mg/L (avg) 2. Total Suspended Solids (TSS) < 25 mg/L (avg) 3. Total Residual Chlorine < 0.02 mg/L (avg) 4. Un-Ionized Ammonia (NH3) < 1.25 mg-N/L(max) @ 15 OC +/- 1 OC • Quarterly reports for average annual flows of 2,500 – 17,500 m3/d & HRT > 5 days WSER and Lagoons • WSER impacts small remote communities who rely on lagoon treatment • Upgrading required to mitigate: – Algae growth effects on WSER TSS & BOD effluent criteria – Effluent total & unionized ammonia – Fish toxicity (high pH → high NH3 ) Improved BOD & TSS Removal • BOD REMOVAL – Increase Retention Time (Size & Depth) – Increase Oxygen (Mechanical Aeration) – Increase Bacteria (Attached Growth Media) – Primary Filtration (vs Anaerobic Lagoon) • TSS REMOVAL – Inhibit Algae Growth – Mechanical Separation – Constructed Wetlands (Biofilter) Algae & Ammonia • Problem: Inhibiting algae growth reduces nitrogen and ammonia removal • Seasonal nitrogen removal useful for only intermittent discharges • Post-treatment ammonia nitrification is required for continuous discharges Ammonia Removal Options • INTERMITTENT DISCHARGE LAGOON – Algae Uptake & Seasonal Discharge – Wetland Post Treatment (Nitrification) – Attached-Growth Post Treatment – Attached-Growth In-situ Technology • CONTINUOUS DISCHARGE LAGOON – Wetland Post Treatment (Nitrification) – Attached-Growth Post Treatment – Attached-Growth In-situ Technology Additional Upgrade Measures • Increase oxygen supply and efficiency • Increase depth • Add partitions to optimize HRT • Add media (Fixed film) to increase bacteria • Reduce BOD loading (primary filtration) • Add mechanical treatment components • Phosphorus precipitation & separation Additional Upgrade Measures • Increase oxygen supply and efficiency • Increase depth • Add partitions to optimize HRT • Add media (Fixed film) to increase bacteria • Reduce BOD loading (primary filtration) • Add mechanical treatment components • Phosphorus precipitation & separation Additional Upgrade Measures • Increase oxygen supply and efficiency • Increase depth • Add partitions to optimize HRT • Add media (Fixed film) to increase bacteria • Reduce BOD loading (primary filtration) • Add mechanical treatment components • Phosphorus precipitation & separation Additional Upgrade Measures • Increase oxygen supply and efficiency • Increase depth • Add partitions to optimize HRT • Add media (Fixed film) to increase bacteria • Reduce BOD loading (primary filtration) • Add mechanical treatment components • Phosphorus precipitation & separation Sustainability Considerations Conventional Sustainability Model Economics Social Optimal Conventional Spot Model Environment Alternative Sustainability Model Social Alternative Environment Model Economics Alternative Sustainability Model Social Key Environment Constraint Economics Regulations Cumberland Lagoon Upgrade Village of Cumberland Cumberland Vancouver Victoria Village of Cumberland • Coal mining town incorporated in 1898 • Old combined (storm & sanitary) sewer • Discharge Permit issued in 1967 • Provided 48 years to reduce flows • Authorized works (1967) mechanical screens, aerated/facultative lagoon, phosphorus removal & disinfection • 2-Cell Aerated & facultative lagoons • $2M - 85% Separation = no flow reduction Village of Cumberland • Discharge to man-made drainage canal leading to fish bearing stream with extremely low summer flows • 2018 ADWF = 800 m3/d PWWF > 20,000 m3/d • Permit Effluent Criteria – CBOD5 & TSS < 30 mg/L (max) – Total-P < 1.0 mg-P/L – Fecal Coliforms < 200 MPN/100 mL (median) • Design ADWF = 1,800 m3/d Pop = 3,800 Village of Cumberland SCREENS MAPLE LAKE “CREEK” Full-Flow Mechanical Option 1 – “Lagoon Upgrade” using mechanical enhancements to remove phosphorus, disinfect, discharge to adjacent wetland area to restore natural “wet” conditions and provide for natural polishing treatment. Option 2 – “Excess Wet-Weather Lagoon Treatment” - Membrane Bioreactor (MBR) treatment for 2 x ADWF, wet weather flows directed to existing lagoons. Option 3 – “Full Flow Mechanical” - Moving Bed Biofilm Reactor (MBBR) to treat and disinfect full wet weather flow, with additional tertiary filtration for 2 x ADWF. The lagoons would then be decommissioned. Lagoon Upgrade INLET AERATED FACULTATIVE PERACETIC SOLIDS CHANNEL LARGE SMALL ACID SEPARATION SCREENING LAGOON LAGOON DISINFECTION BYPASS > 3,600 m3/d NATURAL WETLANDS < 3,600 m3/d MLC SOLIDS DISCHARGE MANAGEMENT > 3,600 m3/d Excess Wet-Weather Lagoon Treatment INLET PERACETIC CHANNEL FINE SCREEN MBR ACID SCREENING DISINFECTION < 3,600 m3/d MLC DISCHARGE AERATED FACULTATIVE SOLIDS SMALL LARGE MANAGEMENT LAGOON LAGOON > 3,600 m3/d Full-Flow Mechanical INLET SOLIDS PERACETIC CHANNEL FINE