Green recovery of energy and nutrients from wastewater in the frame of the Circular Economy.

1. Green recovery of energy and nutrients from wastewater in the frame of the Circular Economy ELENA FICARA POLITECNICO DI MILANO Dipartimento di Ingegneria Civile e Ambientale - Sezione ambientale

2. Dipartimento di Ingegneria Civile e Ambientale Content - Introduction: general circular economy framework - Technologies for resource recovery in WWTPs - Overview on applying algae for wastewater treatment for nutrients/energy recovery/savings

3. Dipartimento di Ingegneria Civile e Ambientale The role of wastewater treatment plants Challenges of sanitation systems:  Supply safe (drinking) water  Limit environmental impacts by wastewater discharges Historically… but…  Growing population,  Life style changing,  Climate change are modifying water availability and request new challenges are to be faced Uptake Use discharge

4. Dipartimento di Ingegneria Civile e Ambientale The circular approach …. Water, energy, resources Water source treatment Reuse treatment discharge New hierarchy use

5. Dipartimento di Ingegneria Civile e Ambientale The circular approach ….

6. Dipartimento di Ingegneria Civile e Ambientale Looking beyond the current "take, make and dispose” extractive industrial model, the circular economy is restorative and regenerative by design.

7. Dipartimento di Ingegneria Civile e Ambientale Which kind of resources to be recovered? Biodegradable organics: 12 – 14 W/PE Total organics: 18 – 20 W/PE Ammoniacal N: 8 W/PE TOTAL: 20 – 28 W/PE (4-5 times energy required for WW treatment) Clean water Chemical energy Nutrients (N, P) Wastewater 40-70 m3/PE/y 2-3 kg N/PE/y 0,5-1 kg P/PE/y = WWTP  WRRP Water Resource Recovery Platform

8. Dipartimento di Ingegneria Civile e Ambientale Energy request for the water sanitation o 10-17 W/PE o 90-150 kWh/PE/y • Reducing water consumption • Optimizing processes • Recovering energy from wastewater 2-3% of electric energy consumption up to 7% (in EU and USA) How to save energy? In Italy: Total consumption 7500 GWh/y (2,5% national electric energy consumption) Campanelli, Foladori, Vaccari (2013) •water supply 57% •water treatment 43%

9. Dipartimento di Ingegneria Civile e Ambientale Energy recovery from wastewater Thermal: Wastewater temperature: 14 - 23°C. Heat pumps to warm (winter) or cool (summer) buildings. e.g.: Nosedo (Milano) WWTP recovers 200 kW Hydro-electric: by taking advantages of head loss e.g.: Folgaria (TN) WWTP recovers 40 kW (50 L/s for 236 m) Chemical energy: typically recovered from the sludge line In Italy: today 121 GWh/y from AD of waste sludge (GSE, 2014) Potential: 2100 GWh/y (= all plants with tertiary treatments would use conventional AD)

10. Dipartimento di Ingegneria Civile e Ambientale Energy positive WWTP: utopic? • Recover energy with effective AD • Optimizing energy intensive processes New pathways in biological treatment Optimization of existing treatment e.g.: Aeration systems Optimized processes Energy consumption P.E. served WWTP of Strauss (Austria) 250 000 P.E. Energy cost for treatment: 11.3 kWh/PE/y, offset by biogas production

11. Dipartimento di Ingegneria Civile e Ambientale Recovery of phosphorus Accessible stocks of P-rocks are going to be exhausted SOON Use Wastes Agriculture Plants P mining Water bodies (WWTP)  P is fundamental in sustaining agriculture  Demand is growing together with word population  Uneven distribution of P mines (Morocco, Cina, US)  EU is P deficient About 18% of the P request could be recovered from waste streams Cordell & White, 2011, Sustainability, 3(10), pp. 2027-2049

12. Dipartimento di Ingegneria Civile e Ambientale Recovery of phosphorus Biological processes: P-iperaccumulating microorganisms Recovery from ashes from sludge inciniration: P + N, K, P, Mg, Ca Chemical precipitation: Addition of Al(OH)3 / Ca5(PO4)3OH Struvite precipitation Recovery alternatives

13. Dipartimento di Ingegneria Civile e Ambientale Recovery of phosphorus - struvite 𝐌𝐠𝐍𝐇 𝟒 𝐏𝐎 𝟒 ∙ 𝟔𝐇 𝟐 𝐎 ∶ 𝐬𝐥𝐨𝐰 𝐫𝐞𝐥𝐞𝐚𝐬𝐞 𝐟𝐞𝐫𝐭𝐢𝐥𝐢𝐬𝐞𝐫 1 2After AD Efficiency up to 90% Low Purity After S/L separation Efficiency: 40% – 60% High Purity http://www.phosphorusplatform.eu/p latform/news/1308-eu-organic- farming-committeepositive-opinion

14. Dipartimento di Ingegneria Civile e Ambientale Recovery of bioplastics (PHA) “European Strategy for Plastics in a Circular Economy”, 16/1/2018 (http://ec.europa.eu/environment/circula r-economy/pdf/plastics-strategy.pdf Carbonera WWTP – pilot demonstration Expected increase in PHA production by 2022: 24000 tonPHA/y (european-bioplastics.org) Motivation

15. Dipartimento di Ingegneria Civile e Ambientale San Rocco (1.050.000 PE) Nosedo (1.250.000 PE) Recovery of water in agriculture Milano WWTPS: Tertiary treatments 120 millions m3/y (185 gg) to agriculture Only 2% of WWTP is reused (Lautze et al., 2014)

16. Dipartimento di Ingegneria Civile e Ambientale HRAP: High rate algal pond Primary sludge PRIMARY SETTLER ACTIVATED SLUDGE SECONDARY SETTLER ANAEROBIC DIGESTION PRE - TREATMENTS INFLUENT EFFLUENT BIOSOLIDS Mixed sludge Recirculation Biogas SOLID/LIQUID SEPARATION TERTIARY TREATMENT Secondary sludge New GREEN solutions: Microalgae & WWTP

17. Dipartimento di Ingegneria Civile e Ambientale Microalgae Oxygenic photosynthesis H2O  O2 • 2.8 billons years • Allowed aerobic organisms to develop  Large increase in productivity O2 Microalgae • Mostly autotrophic/photosynthetic • Versatile • Biodiverse

18. Dipartimento di Ingegneria Civile e Ambientale Highly productive Combined production Fine chemicals/goods Biodiesel/biogas Limited competition for soil with crop production Allow nutrients recovery Process Integration WWTP, AD plants Power stations Microalgae - claims

19. Dipartimento di Ingegneria Civile e Ambientale First applications: earlier than 1960 in California New recent interest «Microalgae + wastewater + treatment» Scopus, 2017 Microalgae & WWTP

20. Dipartimento di Ingegneria Civile e Ambientale Advantages of microalgae in wastewater treatment: - Low energy cost (extensive treatment based on solar energy) - Integration algae/bacteria - Nutrient recovery + COD removal - Production of algal biomass - Other interesting effects:  Disinfection  Removal of micropollutants  Removal of heavy metals Microalgae & WWTP

21. Dipartimento di Ingegneria Civile e Ambientale Water-stream - secondary treatment  Activated sludge algae/bacteria processes  Nutrient recovery(N, P) • Uptake • Conversion (CO2, N2) Removal efficiencies • COD: 60 – 95 % • NH4 +: 70 – 99 % • PO4 3-: 50 – 95 % Primary sludge PRIMARY SETTLER ANAEROBIC DIGESTION PRE - TREATMENTS INFLUENT EFFLUENT BIOSOLIDS P-56 Mixed sludge Microalgal biomass Biogas SOLID/LIQUID SEPARATION TERTIARY TREATMENT PBR SOLID/LIQUID SEPARATION (A) Microalgae & WWTP

22. Dipartimento di Ingegneria Civile e Ambientale Primary sludge PRIMARY SETTLER ACTIVATED SLUDGE SECONDARY SETTLER ANAEROBIC DIGESTION PRE - TREATMENTS INFLUENT EFFLUENT BIOSOLIDS Mixed sludge Recirculation Biogas SOLID/LIQUID SEPARATION (B/C) PBR SOLID/LIQUID SEPARATION Microalgal biomass Secondary sludge Water-STREAM – tertiary treatment  Disinfection  Polishing  Efficiencies (lab -scale): • COD: 85 – 90 % • NH4 +: 80 – 100 % • PO4 3-: 75 – 99 % Microalgae & WWTP

23. Dipartimento di Ingegneria Civile e Ambientale Side-stream (sludge line) Nutrient removal from the liquid fraction of digestate  Reduction of the N and P load by uptake to the water line  savings  Recycling of N-oxidized forms (nitrification)  Removal efficiencies (lab/pilot scale): • COD: 60 – 70 % • NH4 +: 60 – 95 % • PO4 3-: 50 – 95 % Primary sludge PRIMARY SETTLER ACTIVATED SLUDGE SECONDARY SETTLER ANAEROBIC DIGESTION PRE - TREATMENTS INFLUENT EFFLUENT BIOSOLIDS P-106 Recirculation Biogas SOLID/LIQUID SEPARATION TERTIARY TREATMENT Secondary sludge PBR (D) Microalgal biomass SOLID/LIQUID SEPARATION Mixed sludge Microalgae & WWTP

24. Dipartimento di Ingegneria Civile e Ambientale Examples of demonstrative WWTP applying algae as a secondary treatment: • South of Spain (Chiclana) • California (Dehli and San Luis Obispo) • New Zealand (Christchurch, Hamilton) • Morocco HARP = High Rate Algal Pond Microalgae & WWTP

25. Dipartimento di Ingegneria Civile e Ambientale Pilot plant in Chiclana ALL GAS FP7-PROJECT (AQUALIA): • HRAP = primary/secondary treatment • Algal suspension: DAF floatation, AD+biogas upgrading BioCH4 • Energy request = 0,16 kWh/m3 Energy produced = 0,17 kWh/m3 • Land request =2 m2/P.E. Microalgae & WWTP

26. Dipartimento di Ingegneria Civile e Ambientale Biofuels Biofertilizers Biomaterials Nutrients In WW Simplified (low costs) culturing systems Wastewater treatment WWTP  algae  resources

27. Dipartimento di Ingegneria Civile e Ambientale Polisaccaride (Porphyridium) PHA (cianobacteria) PHB (Arthrospira, Sinechocystis) Bioplastics Algal Biomass Fermentation to VFA PHA by iperaccumulating bacteria Bioflocculants Bioplastics WWTP  algae  biomaterials

28. Dipartimento di Ingegneria Civile e Ambientale Conversion Process Product Termochemical Biochemical Fisico-chemical Gasification Pyrolysis, Combustion Syngas Electricity/heat Fermentation Anaerobic digestion Methane Hydrogen Ethanol alcohols Extraction Trans-esterification Biodiesel WWTP  algae  biofuels

29. Dipartimento di Ingegneria Civile e Ambientale Species Theoretical BMP (Sialve et al. 2009) LCH4/gVS Cell wall Actual BMP (Mussgnug et al. 2010) LCH4/gVS Dunaliella salina 0.68 None 0.32 Chlamydomonas reinhardtii 0.69 Protein 0.39 Arthrospira platensis 0.47–0.69 Protein 0.29 Euglena gracilis 0.5–0.8 Protein 0.32 Chlorella kessleri 0.63–0.8 Polysaccharide 0.22 Scenedesmus obliquus 0.59–0.69 Polysaccharide 0.18 WWTP  algae  biogas

30. Dipartimento di Ingegneria Civile e Ambientale Issues/limitations • Low C/N ratio co-digestion • Cell wall resistance to biodegradation pretreatment thermophilic digestion • Low economic value compared to other algae-derived products DA integrated into a biorefinery concept WWTP  algae  biogas

31. Dipartimento di Ingegneria Civile e Ambientale Estimated high productivity (Chisti et al., 2007) crop Oil yield (L ha-1) Maize 172 Soy 446 Colza 1190 Jatropha 1892 Cocco 2689 Palma 5950 Microalgae 136.900 Microalgae 58.700 1: 70% lipids 2: 30% lipids High lipid content: • Special strains (Chlorella, Dunaliella, Isochrysis, Nannochloris, Nannochloropsis, Neochloris, Nitzschia, Phaeodactylum and Porphyridium spp.) • Environmental growth conditions (lack in N/stress) Unrealistic expectations !! More realistic values: 18.000-23000 L/ha WWTP  algae  biodiesel • Production costs (Norsker et al., 2011)  1 ha  10 €/kg  100 ha  4 €/kg  Goal (0.40 €/kg)  combined strategies

32. Dipartimento di Ingegneria Civile e Ambientale Cost reduction strategies Biomass productivityg/m2/day 20 CO2 usage kg/kgbiomass 4 Water evaporation L/m2/day 10 Mixing power consumption W/m3 2 Labour people/ha 0.1 Production days Days 365 Land area ha 100 Ratio V/S m3/m2 0.15 CO2 fixation efficiency 0.45 Dilution rate 1/day 0.2 Total culture volume m3 150000 Scenario Inputs Reactor Harvesting 1Water, CO2 and fertilizers Raceway Centrifugation 2Water, CO2 and fertilizers Raceway Flocculation-Sedimentation+Centrifugation 3Free flue gases and wastewater Raceway Flocculation-Sedimentation+Centrifugation 4Free flue gases and wastewater Raceway Flocculation- LamellarSedimentation+Centrifugation 5Free flue gases and wastewater Raceway Flocculation-LamellarSedimentation+Filtration 6Free flue gases and wastewater Raceway Flocculation-LamellarSedimentation+Filtration WWTP  algae  biodiesel

33. Dipartimento di Ingegneria Civile e Ambientale Algal biomass as: -Slow release fertiliser -Natural pesticide -biostimulants Slow release fertilizer Application rate similar to conventional organic fertilisers 6.5–10 t biomass ha−1 Algal biomass • No phyto-toxicity • Stimulating effects as phyto-ormons • Increase in germination indexes Luxury P uptake  P recovery WWTP  algae  biofertilisers

34. Dipartimento di Ingegneria Civile e Ambientale 1 10 100 1000 10000 Ni Cu Pb Zn (mg/kg) 0 5 10 15 20 25 Cd (mg/kg) D.lgs. 99/1992 Sludge disposal Sludge Directive (in preparation) Metal content in algal biomass 35WWTP  algae  biofertilisers

35. Dipartimento di Ingegneria Civile e Ambientale First project approved in the water sector (University of Valencia) Sustainable wastewater treatment using innovative anaerobic membrane bioreactors technology (AnMBR). • Acceptable metal content • Pathogens, micropollutants –> same levels as for sludge Legislation barriers WWTP  algae  biofertilisers

36. Dipartimento di Ingegneria Civile e Ambientale Conclusions • WWTP  resources is mandatory • Technical solutions exist • Potential for applying microalgae-based processes However: • Economics: no established value chain for recovery products / lack on incentives, lack of standard business models • Still on-going pilot/demonstrative projects to validate techno-economic feasibility • Regulatory barriers

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