Waste water treatment and sewage slugde management in Veneto: the role of integrated plants, Composting and Anaerobic Digestion

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Post on 12-Dec-2014



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The management of sewage slude is a challenge and an opportunity. the Integratet plant , WWTP - Anaerobic digestion - Composting is a way to solve this problem


  • 1. Wastewater treatment and sludge production: energy recovery process, techniques and financial evaluation Loro Francesco ARPAV Subotica, Sept. 2013

2. Summary The sludge production from WWTP The solution: Matter recovery Energy recovery The biogas plant The use of sludge mixed with organic waste The technologies The Veneto situation The evaluation of costs and the role of subsidies 3. The sludge production The byproducts of a WWTP are: Clean water Sludge How to Reduce the production: New technologies as MBR Reduction of the amount of water 4. The reduction of water contents High pressure belt press for sludge FILTER PRESSES Centrifuges Drying Beds Performance 70% of water 25% of water To improve the performance it is necessary the use of chemicals 5. The matter recovery Use as fertilizer in agricolture It is necessary a permit Bioaccumulation of pollutants (A.e. if the wastewater is contemined by heavy metals) Specific limits for HV and POPs The Composting plant Production of a fertilizer Use of green waste as filler The process needs energy and dedicated equipment Specific acceptance limits 6. Acceptance limits for sludge Water contents limit landfill acceptance criteria (EU Decision 2003/33) Acceptance limits for composting 7. Acceptance limits for agricolture 8. The energy recovery from sludge using Anaerobic Digestion The production of biogas from sludges was developed during the 70 and 80 but after few years this was abandoned. The causes was: High cost of maintenance Low energy production Market (the landfill was cheaper than AD) 9. A new mix To improve the biogas production the sludge is mixed with organic waste The anaerobic digestion and the composting plant are an integrated plant 10. The Anaerobic Digestion: The technologies applied These technologies works with a mixture of sludge and Organic Waste The main carbon source are the O.W. The sludges represent an income for the waste management plant The composting plant or the reuse in agricolture represents the solution to reduce the amount of sludge and are a fundamental part of an integrated plant 11. Anaerobic digestion plants in Veneto ETRA Bassano d. G. (VI) SESA Este (PD) ETRA Camposampiero (PD) Agrilux Lozzo atestino (PD) Impianto Comunale Treviso Dolomiti ambiente Belluno Agrinord Verona Villa Bionergia Verona 12. The treatment capacity in Veneto Treated sludge (EWC 190805) in 2012 : 110.000 t Treated OW in 2012: more than 300.000 t Biogas production: 35.000.000 Nm3 Energy production: 75 Gwh 13. Plant details Etra - Bassano del Grappa (VI) Valorga Process 14. Plant details: Type Dry Technologies Valorga Reactors 3 reactors 7200 m3 D.M. Contents 20 - 25 % Temperature range 37 C HRT 25 -30 dd 15. Plant Details Etra - Camposampiero (PD) Linde process 16. Type Wet Technologies Linde Reactors size 3300 m3 D.M. Content 9 - 12 % Temperature of the reactor 55 C HRT 17 -20 days The technologies: Etra - Camposampiero 17. Etra Camposampiero (PD) Organic Waste Pulper Sludge Landfill or incinerator Green Waste Composting (Vigonza) Hydrolysis Biogas Anaerobic digestion Solid fraction Liquid fraction WWTP Clean Water Compost Scarps Centrifuge 18. Plant details: Sesa - Este 19. Sesa - Este Type Wet Technologies Internal projects Reactors 4 5000 m3 d.m. Contents 12 - 16 % Regime 37 C HRT 20 25 days 20. Sesa - Este Organic Waste Squeezing Sludge Landfill Green Waste Composting Anaerobic digestion Biogas Separator Solid fraction Liquid fraction WWTP Clean Water Compost Solid fraction Liquid fraction Scarps 21. The importance of quality of waste The production of organic waste presents some features: The production change in terms of quantity and quality during the years The quality of OW could change on the basis of the location and period High contents of inert waste (dangerous for the biogas equipment) Specific flows from industry (as food industry) risk of poisoning A new variable in the process... 22. A new problem: the treatment of wastewater from AD The anaerobic digestion use a big quantity of water and produce a wastewater that cannot be used in Nitrates Vulnerable Areas Part of the wastewater could be used during the composting process of the solid fraction of AD wastewater Some european project on the recovery of NH3 as solid fertilizer Recovery of P as fertilizer (struvite) 23. MBR to reduce the sludge production Some plant use the most advanced technologies in order to reduce the amount of sludge (SESA Este) 24. Struvite production KMg(PO4)6(H2O) MAP [MgNH4PO4*6H2O] 25. The evaluation of the cost Why in the last decade there was a big growth of the AD plant that treat sludges and OW in Italy? The introducion of a special subsides (Green Certificate) that can increase the income of a plant through the energy selling. Without this subsides the AD isnt competitive The evaluation of the cost must take into account the local condition (Green certificates, Green fee) 26. 1. Pre-treatment of the OW and production of organic fraction to the biogas production 2. Wastewater to AD treatment : separation of the solid franction to composting plant 3. Treatment of the liquid fraction of AD with WWTP 4. Energy recovery (Electric/Heat) Dedicated equipment = dedicated costs 27. Anaerobic digestion costs The costs of a composting plant will be lower due to lower technology level 400 450 500 550 600 650 700 750 800 850 900 950 1.000 1.050 Costo di investimento digestori anaerobici per ton di frazione organica trattata Economies of scales, a big treatment capacity reduce the cost of treatment (in terms of euro/t) 28. Investement costs (in Italy) High investement due to the elevate cost per ton.(400- 1000 /ton, around two times for a standard composting plant) The use of anarobic digestion reduce the plant surface (less costs for the purchase of the area where the plant will be located) The evaluation of the cost for an new istallation or the revamping could change on the basis of the national condition (Green Certificates) 29. Operating and maintenance costs The maintenance cost are usually very high (because the machines installed presents an high level of maintenance) Costs fo Employees are usually higher than a composting plant because it is necessary specialized workers. (In Italy around 10 % of the total costs). Costs for technical Costs of enviromental controls, comunication to citizens (NIMBY syndrome) Waste water treatment (the costs are high due to high level of N) Management of the organic fractions (composting, landfill, agricoluture) 30. Simulation of an intergrated plant for slugde OW 72.0000 t/y + 55.000 t or green waste . Interest rate 6%, Amortization and Green Certificate 15 years, solid waste to landfill 14% w/w 35% 10% 2%2% 14% 30% 7% Amortization cost Workers Fuel & Chemicals Environmental Red Tape Maintenance Cost analysis of a real plant 31. Income Analisys of a integrated plant Total income 6.000.000 Workers 23 Energy production 13.000.000 kW Income Composition percentage Green Certificate 18,9 % 27 %Electric Energy Selling 8,9 % Organic Waste Tariff 62,2 % 73 % Other Waste 10,8 % 32. Contacts Loro Francesco Tel. +39.348.0643462 e-mail: lorofrancesco@outlook.com / floro@arpa.veneto.it Thanks for the kind attention Acknowledgement Etra Spa Walter Giacetti


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