Ponds for Wastewater Treatment Gilles Altner Global Environmental Engineering Ltd
The Pond System Pre Treatment Anaerobic Pond Facultative Pond Maturation Pond Rock Filter Sand Filter Wetland Membranes UV g2e g2e
Overview Overview Facultative & aerated ponds: How do they work? Facultative & aerated ponds: How do they work? 1. 1. (Facultative, aerated, media ponds) 2. Pond design aspects & upgrade technologies 2. Pond design aspects & upgrade technologies . (Sludge, inlet, outlet, buffering, hydraulic, aeration, mixing, curtain, media) 3. Resource Consents for ponds 3. Resource Consents for ponds. (Ponds versus high rate treatment plants) 4. Other pond issues . 5. When the pond will not do anymore . 5. Other pond issues (Turning the pond into something else) g2e g2e
Overview Facultative & aerated ponds: How do they work? 1. (Facultative, aerated, media ponds) g2e g2e
Waste Stabilization Ponds The Facultative Pond Sunlight Wind If oxygen is not present (mixing & aeration) in upper layer of pond, O 2 odorous gases can be (daylight hours) released O 2 CO 2 H 2 S 1.2 to 5 m Algae Algae Re-aeration New Cells New Cells Aerobic NH 3 , PO 4 NH 3 , PO 4 3 , 3 , T Aerobic Zone etc etc (temperature) Zone Wastewater 0.3 to 0.6m Dead Cells Dead Cells O 2 O 2 CO 2 CO 2 H 2 S + 2O 2 H 2 SO 4 NH 3 , PO 4 NH 3 , PO 4 3 , 3 , Settleable Facultative Bacteria Bacteria etc etc solids • ANAEROBIC PONDS / Anoxic Facultative New Cells New Cells Zone Zone Bottom sludge Dead Cells Dead Cells 0.5 to 0.8m • FACULTATIVE PONDS Anaerobic Organic acids, Anaerobic Organic wastes CO 2 + NH 3 + H 2 S + CH 4 Zone alcohols Zone 0.1 to 0.3m • MATURATION PONDS g2e g2e
Waste Stabilization Ponds • FACULTATIVE PONDS: For domestic and mixed loading Depth 1.5 to 2m, HRT 20 to 60 days, in NZ up to 90 days Up to 80% BOD, in theory up to 80% Am-N reduction (T !!) In theory up to 90% TN reduction, not in New Zeand At temperatures 20 to 25 dgrC, BOD load 100 - 400 kgBOD/ha/day • AEROBIC, FLOW THROUGH PONDS Sludge production about 5 to 7 m 3 /yr/l/sec or about 10mm/yr 2 to 5 m deep, HRT 3 to 5 days, partially / completely mixed High TSS & BOD loading, no Am-N or TN reduction Temperature dependant, BOD load 100 to 350 kgBOD/m 3 /day • AEROBIC PONDS WITH SOLIDS RECYCLE Depth 1 to 1.5m, HRT 5 to 10 days Some BOD, some Am-N reduction, some TN reduction, but mainly TSS (algae) reduction and disinfection g2e g2e
Waste Stabilization Ponds • AERATED PONDS , with or without solids return Generally 3m+ deep, HRT 1 to 3 d, 1d, 1d, 1d to limit algae growth MLSS of about 400 mg/l, no algae, TN reduction only if recycle Power for aeration and mixing 6W/m 3 first, 1 to 1.5 W/m 3 others Sludge production +/- 40m 3 /yr/l/sec (= 6 to 7 times normal pond) Treatment BOD < 20 mg/l TSS < 30 mg/l Am-N < 5 mg/l Aerated & Series of low partially / power aerated TN < 15 mg/l complete Lagoons mixed Lagoon g2e g2e
Waste Stabilization Ponds • PONDS with GROWTH MEDIA: Advanced treatment 1.5 to 3m+ deep, HRT 20 days+, less possible MLSS low, but high TSS (biomass growth), aeration required BOD 5 < 15mg/l, Am-N< 1 mg/l, TN< 10 mg/l Sludge production 5 to 7 m 3 /yr/l/sec (10mm/year) Algae New Cells 3 , NH 3 , PO 4 Biomass Aerobic etc Zone Dead Cells O 2 CO 2 T 3 , (temperature) NH 3 , PO 4 Bacteria etc New Cells O 2 O 2 O 2 Facultative Dead Cells Zone Anaerobic Zone g2e g2e
Overview Overview Facultative & aerated ponds: How do they work? Facultative & aerated ponds: How do they work? 1. 1. (Facultative, aerated, media ponds) 2. Pond design aspects & upgrade technologies (Sludge, inlet, outlet, buffering, hydraulic, aeration, mixing, curtain, media) 4. Other pond issues . 5. When the pond will not do anymore . 5. Other pond issues (Turning the pond into something else) g2e g2e
The Typical New Zealand Pond The Typical New Zealand Pond The Typical New Zealand Pond The Typical New Zealand Pond Sludge Level Two pond system Up to 1.3m 100m x 90m x 1.4m 0 0 WETLANDS WETLANDS WETLANDS WETLANDS (90% of water depth) 1 1 100m x 60m x 1.8m 0 0 2 2 0 0 3 3 0 0 4 4 0 Aerator Aerator 0 Wetlands 5 5 0 0 Wetland clogged 6 6 0 0 POND 1 POND 1 7 7 0 0 150m x 60m plus with pond solids 8 8 0 0 Inlet Inlet Inlet 9 0 110m x 80m 0 0 and plant overgrowth 10 10 POND 1 20 20 30 30 Aerator Aerator 40 40 Odours 50 Poor flow conditions Outlet Outlet Outlet POND 2 POND 2 POND 2 60 70 Algae blooms 80 90 Wetland failure HRT Discharge out of RC Theoretical: 25 days True : 8 days g2e g2e g2e g2e g2e g2e
Simple Pond Improvements Maintaining & Improving Biological / hydraulic load Biological / hydraulic load Reduce shock loads & hydraulic peaks Reduce shock loads & hydraulic peaks Costs, community & industry input Costs, community & industry input Regain HRT Regain HRT Desludging Desludging Costs, damage, disposal, verification Costs, damage, disposal, verification Inlet / outlet design Inlet / outlet design Increase HRT, use flow buffering Increase HRT, use flow buffering Available freeboard, waveband material Available freeboard, waveband material Dividing curtains / barriers Dividing curtains / barriers Prevent short-circuiting Prevent short-circuiting Design, quality of materials used Design, quality of materials used Aeration / mixing / DO Aeration / mixing / DO Reduce odours and overloading Reduce odours and overloading Get them right ! Type, water depth, purpose, power Basic improvements g2e g2e
Simple Pond Improvements g2e g2e
Advanced Pond Improvements What has to be achieved? Dividing ponds Dividing ponds Improve treatment efficiency Improve treatment efficiency What type of pond? HRT What type of pond? HRT Increase HRT, prepare for the future Increase HRT, prepare for the future Heighten the embankment Heighten the embankment What for? Costs What for? Costs Rockfilter (aer/non-aer) Rockfilter (aer/non-aer) Improve TSS, BOD 5 , Am-N and TN Improve TSS, BOD 5 , Am-N and TN Costs, design, references !! Costs, design, references !! Growth media Growth media Increase BOD 5 , Am-N, TN treatment Increase BOD 5 , Am-N, TN treatment Costs, aeration required, HRT Costs, aeration required, HRT Floating wetlands Floating wetlands Improve TSS, BOD 5 (TN, TP), ((Am-N)) Improve TSS, BOD 5 (TN, TP), ((Am-N)) Site data, site specific, costs, quality g2e g2e
Growth Media Carbon black sleeve with floatation tube. Mats are connected to stainless steel wires attached on each side of the treatment pond Lower UltraWeave layer Upper UltraWeave layer promotes bacterial promotes growth of biofilms & acts as sessile algae and higher hydraulic barrier for organisms for uptake of BOD 5 and TSS removal DRP and ammonia g2e g2e
Growth Media Installed Aerobic Zone Air release at >200 mbar dP Biomass Support Media Air flow g2e g2e
Typical results at start-up g2e g2e
Floating Wetlands Know what you need – avoid ’’ one system fits all ’’ Floating wetlands January 2012 Floating wetlands shortly after installation g2e g2e
Example 1: Ponds not achieving RC Domestic & Industriel Flow: 680 960 m 3 /d WETLANDS Peak: 1,600 m 3 /d BOD 5 175 kg/d POND 1 TKN 43 kg/d Inlet Treatment Required Outlet TSS/BOD 5 < 20 mg/l POND 2 TKN < 6 mg/l Am-N < 3 mg/l TP < 3 mg/l g2e g2e
Example 1: Ponds not achieving RC > Insufficient HRT 2.6m 2.3m 1.4m 1.6m POND 1 POND 2 g2e g2e
Example 1: Pond not achieving RC > Improve treatment Improve flow at inlet, transfer & outlet WETLANDS Automatic screening & flow metering Aeration & mixing in inlet area Biological growth media & aeration Alkalinity dosing & Fe dosing for TP reduction g2e g2e
Overview Overview Facultative & aerated ponds: How do they work? Facultative & aerated ponds: How do they work? 1. 1. (Facultative, aerated, media ponds) 2. Pond design aspects & upgrade technologies 2. Pond design aspects & upgrade technologies . (Sludge, inlet, outlet, buffering, hydraulic, aeration, mixing, curtain, media) 3. Resource Consents for ponds (Ponds versus high rate treatment plants) 4. Other pond issues . 5. When the pond will not do anymore . 5. Other pond issues (Turning the pond into something else) g2e g2e
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