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- 1. A proposed sustainable BNR plant with the emphasis on recovery of COD and phosphate Xiaodi Hao*,** * The R & D Centre for Sustainable Environmental Biotechnology, Beijing University of Civil Engineering and Architecture, China N IWA/EWA Amsterdam, October 2-4, 2002 and Mark van Loosdrecht** ** Kluyver Laboratory for Biotechnology, Delft University of Technology, the Netherlands
- 2. N IWA/EWA Drawbacks of conventional BNR processes COD + O2 → CO2 + H2O NH4 + + O2 → NO3 - + H+ + H2O E CO2 Aeration NO3 - + COD → N2 ↑ + CO2 + H2O 4-5 kg COD/kg N PO4 3- + Al3+ → AlPO4↓ 2.2 kg Al/kg P COD Biomass 0.4 sludge-COD/kg COD removed 0.6 kg O2/kg COD E 4.6 kg O2/kg N E 14 MJ/kg COD E O2 Consuming more energy (COD oxidation and nitrification) Using more substances (COD, chemicals etc.)
- 3. N IWA/EWA Concept of sustainable BNR processes COD + O2 → CO2 + H2O CH4 E NH4 + + O2 → NO3 - + H+ + H2O NO2 - N2↑ COD $ $ $ $ $ € € € € € Effluent Struvite (Fertiliser) Minimum P Minimising consumption of energy and resources Recovering energy and elements and recycling effluent
- 4. N IWA/EWA Denitrifying phosphorus removal Denitrifying phosphorus-removing bacteria (DPB) COD PO4 3- NO3 - Cell N2 COD PO4 3- O2 Cell H2O NO3 - + COD → N2 ↑ + CO2 + H2O Bio-N removal: Bio-P removal: COD O2 CO2 Biomass Minimum Integrating bio-N and bio-P removal Saving COD and O2 and reducing sludge and CO2 production
- 5. N IWA/EWA Anaerobic ammonium oxidation (ANAMMOX) NH4 + + NO2 - → N2 ↑ + 2H2O ANAMMOX bacteria Never known 10 years ago Sustainable!!! BNR ANAMMOX is an extremely recent discovery! ……………………………………… EnvironmentWastewater treatment X COD X O2 Converting NH4 + directly into N2 Requiring no COD and O2
- 6. N IWA/EWA The BCFS® and CANON processes The BCFS® process The CANON process B SC F O2 COD Sludge UASB UNITANK Pasveer BCFS NH4 + NH4 + NH4+ O2 + + O2 NO3- NO2 - + ++ H2O H+ H+ O2O2 NO3 - NO2- N2 + H2O + NO3 - N2 NO2- + H+NO2- Biofilm Anaerobic Aerobic BulkBoundary layer z 0 wastewater )PO,NH(COD, -3 44 + effluent excess sludge SETTLER Anaerobic Recirculation A Recirculation B Return sludge AerobicAnoxic MixedContact Recirculation C P-stripping BCFS® : biological and chemical phosphorus and nitrogen removal CANON: completely autotrophic N-removal over nitrite
- 7. N IWA/EWA Proposed sustainable wastewater treatment plant BCFSA Digestion Digested sludge Influent CANON Effluent P-precipitationMgCl Water Sludge/mixed liquor Gas Chemicals CH4 Struvite Converting COD into methane (CH4) Recovering P as struvite (MAP)
- 8. N IWA/EWA Remarks of sustainability for the proposed BRN plant Proposed WWTP Conventional WWTP Oxygen demand kg O2/kg N removed kg O2/kg COD removed 2.6 0.29 4.65 0.6 COD demand kg COD/kg N removed 1.4 4-5 Methane production kg CH4-COD/kg COD removed 0.28 0 Sludge production kg sludge-COD/COD removed 0.29 0.4 Phosphate recovery kg P/kg P removed 0.49 0 Reduction of CO2 release % 18 0 Subject
- 9. N IWA/EWA Conclusions A proposed BNR plant for sewage treatment is based on recoveries of COD as methane and phosphate as struvite. Due to sustainability of the BCFS® and CANON processes, an optimal treatment system is possible with minimal use of energy and resources Technological difficulties will not be a problem in application of the proposed BNR plant to practice. BNR sustainability
- 10. Thank you for your attention!
Editor's Notes
- -Good afternoon, ladies and gentlemen. -This is my presentation title…… -Actually this study was a joint research, which was financed by the Royal Dutch Academy of Sciences. Prof. Mark van Loosdrecht was my promoter.
- -With this slide, I show you ‘Drawbacks of conventional BNR processes’: Consuming…..and Using…… -Let’s see more details -This is carbon oxidation. This reaction needs to consume oxygen, that is, energy consuming. In this way, lots of metabolic heat contained in COD is destroyed. -Nitrification also needs to consume oxygen, or energy. -Oxygen supply is generally supplied by aeration consuming energy. Consumption of energy created from fossil fuel releases green-house gas, carbon dioxide into atmosphere. -Denitrification consumes a lot of carbon soures (COD). -Chemical precipitation of phosphorus needs to consume lots of chemicals. -COD oxidation produces biomass, or excess sludge.
- -Now let’s establish a concept of sustainable BNR processes. The first point is to minimize……and the second point is to recover…… -Direct carbon oxidation should be avoided, and let COD converted into methane. -Nitrification should be shortened to nitrite, instead of nitrate. As an intermediate of nitrification, nitrite can save oxygen for nitrification and save carbon source for denitrification. -Phosphorus should be precipitated as struvite for fertilizer purpose. -Effluent should be recycled for lake refilling, fish farming, toilet flushing, building constructing, etc.
- -Fortunately, there are two biological pathways to realize sustainable BNR processes. -The first one is denitrifying phosphorus removal, which can integrate bio-N and bio-P removal, save COD and O2, and reduce sludge and CO2 production. -This is the principle of bio-N removal, and this is the principle of bio-P removal. -There is a special type of bacterial in nature which has a function of ‘two in one’. That is DPB. -DBP can contribute to minimize consumption of COD and O2, and production of biomass and CO2.
- -The second new biological pathway in wastewater treatment is ANAMMOX, which can convert ammonium directly into N2, and require no COD and O2. -This is the ANAMMOX reaction. 10 years ago nobody knew ANAMMOX. So ANAMMOX is an extremely recent discovery! -Due to no COD and O2 involved in the process, ANAMMOX has a sustainable feature to a great extent, which makes BNR processes reach a new milestone, and makes wastewater treatment and environment friendly.
- -Based on DPB and ANAMMOX, two processes have been developed or developing. BCFS…….and CANON…… -This is the BCFS process, which was developed and applied in the Netherlands. -There have been many BNR process already in practice. Among them, BCFS can hit the sustainable aims as described in the last slide for DPB. -The CANON process occurs in biofilm with three autotrophic bacteria in it. Nitrite accumulation in biolfilm is a key for ANAMMOX development in biofilm. Due to different affinity constants of ammonium oxidizer and nitrite oxidizer, nitrite oxidizer is generally competed out from biofilm. So ammonium oxidizer and nitrite oxidizer serve functions for the CANON process.
- -With the two new processes described above, a sustainable wastewater treatment plant is proposed here, for which conversion of COD into CH4 and recovery of P as struvite are emphasized. -Influent enters the A stage of the A/B process for COD separation as biomass. The remaining COD after the A stage serves denitrifying phosphorus removal. -Sludge both from the A stage and the BCFS process is digested for CH4 production. -Supernatant from digestion is usually rich in both phosphate and ammonium and with high temperature. -Adding MgCl into supernatant creates precipitation of struvite. -The remaining rich ammonium can be removed by the CANON process. -Finally, two effluent streams are mixed for discharge or reuse.
- -With a raw influent to a Dutch WWPT, modeling and mass balance were made for the proposed plant. -This is remarks about sustainability for the plant. -……. -……. -From this table, sustainability of the proposed plant is obvious.
- -Now conclusions. -……. -……. -…….