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NEPTUNE

NEPTUNE. WP-2: Novel treatment technology for wastewater and sludge. Kick-Off meeting NEPTUNE November 2th 2006, Rome . Ghent University - Laboratory of Microbial Ecology & Technology . Introduction and objectives. Wastewater as waste. Wastewater as a resource.

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NEPTUNE

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  1. NEPTUNE WP-2: Novel treatment technology for wastewater and sludge • Kick-Off meeting NEPTUNE • November 2th 2006, Rome Ghent University - Laboratory of Microbial Ecology & Technology

  2. Introduction and objectives Wastewater as waste Wastewater as a resource

  3. Introduction and objectives Wastewater as a resource • Established technologies improved and complemented with novel technologies. • Microbial fuel cells Energy recovery and nutrient removal • Ferrate oxidation • Manganese oxide based oxidation Removal of micropollutants • High temperature pyrolysis • Polymer production from sewage sludge  Valorisation of sludge waste

  4. Established technologies • Conventional aerobic treatment: + Simple process and high treatment efficiency - Aeration cost: 0,5 kWh m-3 = 30 kWh.IE-1.yr-1 - Sludge disposal cost: up to € 500 ton-1DM • Anaerobic digestion: + Biogas production = Energy recovery • 1 kg COD converted = 1kWh - Water temperature >28 °C - Not applicable for low strength wastewaters Can microbial fuel cells be an alternative?

  5. Microbial fuel cells: the challenger • MFC technology + The chemical energy of various types of reducing compounds can be recovered as kWh + Works at low temperatures + Produces low amounts of excess sludge - Bacteria need to “like” it

  6. Batteries and fuel cells Anode: oxidation occurs, electrons go to an electrical circuit Cathode: reduction occurs, electrons arrive from an electrical circuit

  7. Microbial fuel cells Anode: oxidation of substrate by a biocatalyst Cathode: reduction of oxygen

  8. MFC Biofilm ecology

  9. Electricity generation from discrete substrates TAKE HOME: Power densities and substrate to current conversions are increasing

  10. Electricity generation from discrete substrates TAKE HOME: Power densities and subtrate to current conversion are lower for O2 compared to K3Fe(CN)6 systems => a good functioning sustainable cathode is needed!

  11. Electricity generation from wastewater TAKE HOME: Substrate to current conversions are lower compared to discrete substrates: biodegradability!

  12. Reactor design: anode MFC in Neptune • Open air cathode • Tubular configuration • Continuous system

  13. Can stacked MFCs provide power at enhanced voltage and current? • By connecting several batteries or power sources in series and parallel, voltages and currents can be increased. • Series connection: = addition of voltages • Parallel connection = addition of currents • Does the series and parallel connection influences the anodic biocatalytic performance of a MFC?

  14. Stacked MFC design • 6 individual MFC units • Anode: granular graphite matrix synthetic influent • Cathode: granular graphite and ferrocyanide • Membrane: Ultrex • Rubber sheet: separation between the individual MFCs • No bipolar plates • The void volume of the anode was 60 mL

  15. Stacked MFCs provide power at enhanced voltage and current • Maximum voltage and current generation without power generation: • Open circuit voltage = 4,2V (Series) • Short circuit current = 425 mA (Parallel) • Voltage and current at maximum power densities (Pv max) during series, parallel and individual stack operation: TAKE HOME: High power densities can be maintained during series and parallel connection

  16. Reactor design: anode • Select a performing electricity producing microbial consortium suited for the mix of soluble COD present in sludge digestate • Maximize energy recovery and COD removal by optimizing the anode potential • Investigate the influence of the operational parameters on the removal of humic acids and xenobiotics • Build a technical scale MFC for energy recovery and treatment of the digestate

  17. Reactor design: cathode • Jurg or Korneel , could you provide a specific slide explaining your work part?

  18. Reactor design: cathode • Optimize the cathode compartment of an MFC • Develop a cathodic denitrification process

  19. Microbial fuel cells applications • Stand alone MFC technology: • Several MFCs in series or parallel to deliver electricity at the desired current and voltage kWh Wastewater MFC

  20. Combined micro-pollutant removal • Recalcitrant waste water: • First: ferrate, manganese oxide, pyrolysis technology • Second: MFC kWh Wastewater Ferrate MnO4 Pyrolysis MFC

  21. Ferrate technology (EAWAG) • Develop kinetic database for the oxidation of phenol-, amine-, and sulphur- containing micropollutants • Study and model the micropollutant oxidation by ferrate(VI) • Compare phosphate removal with ferrate(VI) vs. conventional with Fe(III) • Ferrate(VI): simultaneous oxidation of micropollutants and phosphate removal

  22. Manganese oxide upflow bioreactor technology (LabMET) • MnO2 as solid phase oxidative agent provides catalytic surface • Partly oxidizes recalcitrant compounds (humic acids, atrazine...) • MnO2 Mn2+ • Bacteria re-oxidize Mn2+ to MnO2 • Bacteria utilize low molecular organics • MnO2 precipitate acts as catalytic surface again In situ regeneration of oxidant by Mn oxidizing bacteria

  23. Mn-oxide UBR (LabMET) • Pretreatment of recalcitrant wastewater • 2 L upflow bioreactor filled with 750 mL MnO2 • HRT: 1 h • Monitoring of effluent for recalcitrant compounds of interest: analytical methodology / biological assays • UBR as stand-alone or in combination with MFC technology

  24. High temperature pyrolysis • Valorisation of sludge as soil amendment • High temperature pyrolysis: • Guarantee microbiologically and chemically safe sludge • Removal of heavy metals • Recovery of phosphorus

  25. Polymer production from sewage sludge • PHA: biodegradable copolymers of PHB and PHV (polyhydroxybutyrate and -valerate) • Why biodegradable polymers ? Synthetic plastics: 25 Mton/yr in EU + US < 20% recycled or incinerated > 80% in landfills and marine environments

  26. Production of PHAs • Pure microbial culture: high costs ! • Mixed microbial cultures: • Phosphorus accumulating organisms (PAO) • Glycogen accum. org. (GAO) • Activated sludge- aerobic dynamic feeding (ADF) • Valorize waste streams by digesting it and produce VFA (volatile fatty acids) as starting substrate for PHA production

  27. PHA low-cost production • Large scale production will be required to meet realistic demands in polymer supply • Abundant and concentrated organic waste needed • Primary and secondary sludge (biosolids) • Ferment to VFA using Cambi process as pretreatment (high pressure thermal hydrolysis) • Biosolids solubilization and complete pathogen destruction • Optimize process for VFA and subsequent PHA production: Cambi-process, microbial inoculum, reactor feeding regime, proper C/N ratios...

  28. Milestones & expected results • Novel MFC design for efficient COD removal and energy recovery from domestic wastewater with demonstrated low sludge production. • MFC-based treatment system to achieve nitrogen and phosphorus removal from domestic wastewater. • Tailored oxidation technologies for adequate micropollutant removal • Valorisation strategies for sludge with warranted microbiological and chemical safety

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