European Workshop 15, 16 september 2003 - Brussels Thermal Treatment of Sewage Sludge for CHP Applications ATHOS WET AIR OXIDATION PROCESS. Case study : N-Brussels N WWTP M. BELKHODJA OTV SA VEOLIA WATER SYSTEMS
SEWAGE SLUDGE : THE BIG ISSUE 8.0 M Dry tons /year produced in the E.U. land application : 40% landfill : 40% incineration : 10% other : 10% Page 2
VEOLIA WATER SYSTEMS Sludge Thermal Processes Sludge concentration Process Treatment Description needed PYROFLUID (OTV) Incineration 25-30% PYROFLUID S (OTV) Incineration for Small capacities 18-22% PYROMIX (OTV) Co-Incineration with MSW 18 25% ATHOS (OTV) Wet Air Oxidation 4-8% THELYS (OTV) Thermal Hydrolysis 12-18% BIOTHELYS (OTV) Sludge production reduction 4% BIOCON (KRUGER) J-VAP (US-FILTER) Drying Dewatering-drying device 15-30% - Page 3
WET AIR OXIDATION Principle Thermal oxidation in liquid phase using molecular oxygen T 330 Conditions HP Application 260 MP 200 BP 120 20 30 55 210 P Biological WAO Incineration 20 g/l 200 g/l Page 4
Sludge Volume reduction Liquid sludge @ 4% Final mineral solid @ 50% MS 100 m 3 2,0 m 3 Page 5
Page 6 Sludge Weight Reduction
WAO Incineration Comparison Incineration Thickning Dewatering Incinération WET AIR OXIDATION Thickning WAO Page 7
ATHOS HISTORY 1992 First tests on tubular plug flow reactor 1993 Autoclave tests 1995 Continous pilot plant (25 L/h - 300 PE) 1998 Start up of ATHOS Toulouse (3 m3/h 50 000 PE) Page 8
Anjou Recherche R&D WAO Reactors Page 9 Autoclave reactor 25 l/h pilot unit
ATHOS REFERENCES Toulouse Trucazzanno N-Brussells Epernay (France) (Italy)) (Belgium)) (France) WWTP capacity: 550 000 PE 300 000 PE 1 100 000 PE 150 000 PE ATHOS capacity : 1 100 TDS/y 5 100 TDS/y 15 000 TDS/y 2 200 TDS/y ATHOS capacity : 3 000 kg DS/d 15 000 kg DS/d 45 000 kg DS/d 7 300 kg DS/d Flowrate : 3 m 3 /h 8 m 3 /h 24 m 3 /h 4 m3/h Devices : 1 1 2 1 Sludge quality : mixed digested TH + digested digested Sludge conc. : 4.5% 8.0% 7.7% 7.6% Volatile fraction : 80% 53% 53% 56% Operating hours: 8 000 h/y 8 000 h/y 8 000 h/y 7 800 h/y Start-Up : 1998 2005 2006 2005 Page 10
Page 11 ATHOS TOULOUSE INDUSTRIAL UNIT
Page 12 ATHOS TOULOUSE INDUSTRIAL UNIT
N-Brussels WTTP Sludge Treatment Water Treatment Clarification Dewatering Thermal Hydrolysis Digestion Incineration forbidden Wet Air Oxidation Dewatering/drying Landfill Page 13
Sludge Train Comparison Thickning Dewatering WAO THP+WAO Design volume 96 m3/h 24 m3 /h Thermal Hydrolysis Oxygen need 3 870 kg/h 1 450 kg/h Digestion Wet Air Oxidation Electricity 23 000 MWh/y 8 000 MWh/y Wet Air Oxidation Dewatering Dewatering Landfill Landfill Page 14
N-Brussels Case Study : Sludge Treatment Water Treatment Clarification Dewatering Thermal Hydrolysis Digestion Wet Air Oxidation Dewatering/drying Landfill Municipal sludge 26 500 TDS/y 16% DS, 73% VM Hydrolysed sludge 26 500 TDS/y 16%DS, 12%SS, 73%VM Digested sludge 17 000 TDS/y 12%DS, 7.7%SS, 53%VM Mineral sludge 8 000 DS/y 10% DS - <5% VM Mineral sludge 8 000 DS/y 95% DS - <5% VM Page 15
ATHOS Process Operating conditions 250 C, 50 bar, pure O2 perfectly mixed reactor Copper sulphates as catalyst Mineralization Process in liquid phase & low temperature Typical performance : - COD removal : > 85% - Volume Reduction > 98% Liquid effluent Highly biodegradable (mainly acétic acid) Residual Solid -Mineral, COT <5% -No leaching - 55% DS min dewatering with no additives Off-Gas -No dioxins, furannes, NOx, HCl, and dust - Thermal Treatment operation needed : CO, VOC Page 16
ATHOS PROCESS gas Oxygene Thick Sludge WWTP Page 17 Dewatering
ATHOS MINERAL SOLIDS Mineral solids caracterization Typical analysis (% de DS) SiO 2 CaO Al 2 O 3 CO 3 SO 4 P 2 O 5 38.3 16.8 12 3.6 2 13 Particules : medium 2.7 µm (1 ~10) COT < 5 % Leaching tests : all metals fixed, Construction Solids Re-use Page 18
Thermal Hydrolysis and Digestion Principle : Thermal hydrolysis under moderate pressure (8 bars) and temperature (165 C) of dewatered sludges - Thermal Hydrolysis Process (THP) Batch Process Solubilization process -steam 150-165 C < 10 bar < 1 hour -Digestion Page 19 100-120 g/l - 14 à 18 days retention time VM Total removal: 55 to 62% 60 to 85% more biogas production No need of recirculation heating loop Easy dewatering : up to 35% DS
Sludge Thermal Hydrolysis Thermal Hydrolysis 15-16% DS sludge 15-16 % SS sludge 15-16% DS sludge 10-12% SS sludge Page 20
Thermal Hydrolysis & Digestion Thermal Hydrolysis Flash Steam Biogaz Thick sludge T=165 C P= 8 bars T=110 C P= 3 bars T=40 C Digested sludge Centrifugation 12-16% 16% DS T=85 C Fresh Steam Fresh Steam T=190 C P=12 bars T=190 C P=12 bars TH Reactor Hot Water Turbo digestion Page 21
N-Brussels WWTP : Heat Recovery Water Treatment Clarification 2 x 1500 kw Flash steam Dewatering Thermal Hydrolysis Steam Electricity Water Boiler Buildings Heating 2 500 kw 5 000 kw 2 500 kw Self- sustaining Digestion Wet Air Oxidation Biogaz Steam Steam Generator 2 000 kw Hot Water 2 000 kw Dewatering/drying 7 000 kw Landfill Page 22
Dewatering/Drying Process Blow down air Feed Slurry Filter press Hot water storage tank Pre-condenser Vacuum source Filtrate Dry cake discharge Page 23
Conclusion: The innovative N-Brussels sludge train is cost effective for high plant capacity using THP & WAO Process Better public acceptance for WAO than Incineration Page 24