Science, research and development European Commission +2:720,1,0,6(6/8'*(352'8&7,21 5(6($5&+3(563(&7,9(6 $QGUHD7LOFKH European Commission – Research DG – Bruxelles Head of Unit “Key Action Sustainable Management and Quality of Water” [email protected] 20/11/2001 ENERGY, ENVIRONMENT AND SUSTAINABLE DEVELOPMENT 1 Science, research and development European Commission Strategies • Reduction of sludge volume and quantity may reduce costs of disposal • Sludge quality however may be worsened • Analysis of sustainability is needed • Interception of pollutants at source is mandatory 20/11/2001 ENERGY, ENVIRONMENT AND SUSTAINABLE DEVELOPMENT 2 Science, research and development European Commission Interception of pollutants at source • Which pollutants can be intercepted? – Some heavy metals, some chlorinated solvents, persistent pollutants coming from industries connected to the sewer • Which pollutants are more difficult to intercept? – – 20/11/2001 Those deriving from road runoff in combined sewer systems (PAHs, mineral oils, heavy metals) and from atmospheric deposition (Hg, other heavy metals, PAHs, etc.) Recalcitrant compounds present in sewage coming from human excreta (residues of pharmaceuticals, hormones, etc.) and residues of Personal Care Products ENERGY, ENVIRONMENT AND SUSTAINABLE DEVELOPMENT 3 Science, research and development European Commission Means of interception • phasing-out of dangerous substances (i.e. ban of mercury thermometers) • early warning from industrial discharges • separation of sewer systems • BMP for managing and pre-treating urban runoff • new design of pharmaceuticals and PCPs • long sludge-age biological wwtp for reducing recalcitrant compounds 20/11/2001 ENERGY, ENVIRONMENT AND SUSTAINABLE DEVELOPMENT 4 Science, research and development European Commission Reduction of sludge quantity: introduction • Sewage sludge originates from the sum of suspended matter in sewage + excess wwtp biological solids • Potential instruments and strategies for reducing sludge generation without modifying the sewage at source: .To use the biochemical energy contained in the wastewater for conversion processes that need energy (denitrification, P removal) and not only for Carbon oxidation or to “waste” biochemical energy in maintenance processes; .To apply wwt processes that are characterised by low biomass growth; .To apply long sludge age systems (extended aeration, membrane bioreactors, biofilm processes); .To manage the activated sludge food chain, stimulating the balanced growth of bacterial predators (with the warning of not grazing the slow growers, like nitrifiers); .To enhance biological sludge stabilisation (pre-treatments, termophilic anaerobic digestion, etc.) 20/11/2001 ENERGY, ENVIRONMENT AND SUSTAINABLE DEVELOPMENT 5 Science, research and development European Commission Nutrient removal wwtp with reduced sludge production • In general terms, biological nutrient removal produce less sludge respect to COD removal only due to: – – – long sludge age no primary settling or primary sludge hydrolysis depends on P concentration in sewage • Chemical P precipitation produces high amounts of sludge 20/11/2001 ENERGY, ENVIRONMENT AND SUSTAINABLE DEVELOPMENT 6 Science, research and development European Commission Two sludge vs single sludge systems • In single sludge systems excess sludge depends on the sum of excess heterotrophs, nitrifiers and PAO’s • In two sludge systems (Denitrifying P-removal bacteria), heterotrophs can be highly reduced • Stoichiometric mass balance (Kuba et al., 1996) show the potential of 30% less oxygen need and 50% less sludge production 20/11/2001 ENERGY, ENVIRONMENT AND SUSTAINABLE DEVELOPMENT 7 Science, research and development European Commission Wwtp with intrinsic lower sludge production • To exploit low yield biological processes – Anaerobic treatment of sewage – Constructed wetlands 20/11/2001 ENERGY, ENVIRONMENT AND SUSTAINABLE DEVELOPMENT 8 Science, research and development European Commission W.I.R.E.S. :D\VRI,QQRYDWLRQIRUWKH5HGXFWLRQRI([FHVV6OXGJH • 2EMHFWLYH prevent biomass formation, the target is to attempt 60% reduction in total biosolids, conserving the treatment efficiency. – Suez-Lyonnaise des Eaux (F) – Université Henri Poincaré Nancy 1 (F) – GENOSCOPE (F) – University of Cambridge (UK) – Inst. National des Sciences Appliquées de Toulouse (F) – Technische Universitaet Berlin (D) – Technische Universitaet Braunschweig (D) – Universitat de Barcelona (E) – Environmental Protection & Resource Conservation (NL) 20/11/2001 ENERGY, ENVIRONMENT AND SUSTAINABLE DEVELOPMENT 9 Science, research and development European Commission W.I.R.E.S. :D\VRI,QQRYDWLRQIRUWKH5HGXFWLRQRI([FHVV6OXGJH • 5RXWHVWREHHYDOXDWHGDVVHVVLQJEDFWHULDOUHVSRQVHWRVWUHVV SRSXODWLRQVKLIWVDQGGLYHUVLW\DQGSURFHVVHIILFLHQF\ – Physical: • • • – Chemical: • • – Oxidants: O³ / H2O2 Uncoupling agents Biological: • • • 20/11/2001 Electrical: Pulsed Electrical Field (PEF) Mechanical: Disintegration techniques Thermal: 65°C and 95°C temperature Low yield induction Anaerobic treatment Predation ENERGY, ENVIRONMENT AND SUSTAINABLE DEVELOPMENT 10 Science, research and development European Commission Long sludge age systems • Biofilm reactors (trickling filters, RBC, SAB?) • Extended aeration • Membrane bioreactors 20/11/2001 ENERGY, ENVIRONMENT AND SUSTAINABLE DEVELOPMENT 11 Science, research and development European Commission Membrane bioreactors Membrane microfiltration system Influent Effluent CSTR Air 20/11/2001 ENERGY, ENVIRONMENT AND SUSTAINABLE DEVELOPMENT 12 Science, research and development European Commission Membrane bioreactors • Very high biomass concentration (25 g/L; limitations for oxygen mass transfer and viscosity) • Very long sludge age possible – treatment of recalcitrant compounds • Zero sludge production possible al low F/M ratios (~0.07 1/d) • Bacteria free effluent • High costs - limited to small wwtp 20/11/2001 ENERGY, ENVIRONMENT AND SUSTAINABLE DEVELOPMENT 13 Science, research and development European Commission Ecological manipulation of the activated sludge environment • Stimulation of the growth of predators (protozoa, metazoa, oligochaetes, etc.) – first CSTR without sludge retention for disperse fast growth (1 to 2 h HRT) – then biofilm reactor for pedrator’s growth • Apparent yield 0.01-0.24 kg TSS/kg COD rem • High energy consumption for aeration 20/11/2001 ENERGY, ENVIRONMENT AND SUSTAINABLE DEVELOPMENT 14 Science, research and development European Commission Enhancement of sludge stabilisation • Pre-treatments to enhance biodegradability – mechanical disintegration – ultrasonic disintegration – chemical conditioning – thermal pre-treatment – enzymatic-microbial pre-treatment – bio-stimulation 20/11/2001 ENERGY, ENVIRONMENT AND SUSTAINABLE DEVELOPMENT 15 Science, research and development European Commission Safe-EX • 6HOI6XVWDLQHG&RPSDFW0RELOH6\VWHP7XUQLQJ :DVWHVOXGJHWRLQHUW 2EMHFWLYH Combine Sludge drying and gasification in one unit having both steps heated by microwave, recovering the thermal energy and the combustible gases. – Muegge Electronic GmbH (D) – Ecutec Barcelona S.L. (E) – Forberg AS (NO) – Vermeulen Product Engineering (NL) – SPEL-PROCONT s.r.o. (SK) – Kiener Hungaria (HU) 57'3HUIRUPHUV • Fraunhofer-Geselleschaft zur Forderung der Angewandten Forschung (D) • PERA International (UK) 20/11/2001 ENERGY, ENVIRONMENT AND SUSTAINABLE DEVELOPMENT 16 European Commission Science, research and development Safe-EX 6HOI6XVWDLQHG&RPSDFW0RELOH6\VWHP7XUQLQJ :DVWHVOXGJHWRLQHUW 20 °C 100°C 120°C 450°C 450°C <80°C forming gasification drying LQSXW product gas microwave Magn. RXWSXW product gas cleaning vaporised water Micro CHP waste heat 20/11/2001 ENERGY, ENVIRONMENT AND SUSTAINABLE DEVELOPMENT 17 Science, research and development European Commission Conclusions • Many different options to reduce sludge generation from wwtp • The main problem stays in the inverse relationship between quantity and quality • Reduction of quantity without affecting sludge quality may be obtained only with the interception of pollutants at source and with enhanced treatment systems • What is sustainable? • Research still needed - sludge reduction in the priorities of the last FP5 Call of Key Action Water 20/11/2001 ENERGY, ENVIRONMENT AND SUSTAINABLE DEVELOPMENT 18