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EPROBIO Foggia 10 July 2010 Environmental Aspects of AD of Sewage Sludge
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EPROBIO Foggia 10 July 2010 BIOSOLIDS LAND APPLICATION ANAEROBIC DIGESTION DEWATERING COMPOSTING DEWATERING THERMAL DRYING CO- DIGESTION INCINERATION GASIFICATION LANDFILL CLAY FACTORY Ashes LANDFILL BIO-DRYING OTHER ORGANIC WASTES CEMENT FACTORY ATAD
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EPROBIO Foggia 10 July 2010 BIOSOLIDS LAND APPLICATION ANAEROBIC DIGESTION DEWATERING COMPOSTING DEWATERING THERMAL DRYING CO- DIGESTION INCINERATION GASIFICATION LANDFILL CLAY FACTORY Ashes LANDFILL BIO-DRYING OTHER ORGANIC WASTES CEMENT FACTORY ATAD ANAEROBIC DIGESTION First application of AD Advantages Possibilities (heat / power) Configurations to improve the performance Co-digestion
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EPROBIO Foggia 10 July 2010 Options to improve AD
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EPROBIO Foggia 10 July 2010 Options to improve AD process 1) Hydrolysis: Pretreatments Thermal Mechanical (ultrasonic) Chemical (ozonation, H 2 O 2,etc.) Biological (enzymatic) 2) Temperature: TAD Increase T of AD to reduce HRT and to incrase OLR 3) Balance between acidogenic and methanogenic step Two-phase digestion 4) Nutrient balance Co-digestion with other wastes At any option, the improvement will depend on: - Sludge characteristics (PS/SS) - HRT used - Temperature of operation (normally MAD)
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EPROBIO Foggia 10 July 2010 Mechanical Biological Thermal Chemical Several effects: -Solubilization -Degradation Improvent of biodegradability Two interest: Increased biogas yield Less residual sludge Improvement options: 1) pre-treatments
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EPROBIO Foggia 10 July 2010 Improvement options: 1) pre- treatment
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EPROBIO Foggia 10 July 2010 TREAMENTS ULTRASONIC vs THERMAL Increase (%) on methane production More effectiveness: - Mesofílic conditions - For secondary sludge Difference on Investment and operating costs. Pretreatment US (11.000 kJ/kg) TT (145ºC/ 30 min) MAD PS 21.311.7 SS 30.017.9 TAD PS 12.516.7 SS 21.418.3 Improvement options: 1) pre-treatments
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EPROBIO Foggia 10 July 2010 9 PPCP’s 9 (Esplugas, M. 2010)
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EPROBIO Foggia 10 July 2010 * AOX, LAS, PCB’s, PAH, DEHP, NP/NPE Their removal has been studied under different operating conditions * Results are complex as depend of the contaminant and conditions Removal or transformation (%) of NPE and DEHP with US (■) and TT (■) pretreatments PS SS 55-71% 53-65% * In any case there is an improvement Improvement options: 1) pre-treatments
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EPROBIO Foggia 10 July 2010 (a) (b) DEHPNPE * AOX, LAS, PCB’s, PAH, DEHP, NP/NPE Their removal has been studied under different operating conditions * Results are complex as depend of the contaminant and conditions * In any case there is an improvement Improvement options: 1) pre-treatments
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EPROBIO Foggia 10 July 2010 Improvement options: 2 Temperature
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EPROBIO Foggia 10 July 2010 Thermophilic vs. Mesophilic AD At low HRT TAD yields are much higher At high HRT yields are similar Values depend on type of sludge -Pathogen removal higher in TAD (Biosolids Class A) Better removal of Microcontamiinats % (AOX, LAS, PCB’s, PAH, DEHP, NP/E) - More VFA in supernatants - Worse dewaterability
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EPROBIO Foggia 10 July 2010 Temperature range alternance (Tartakovsky et al. 2007) Incr. 50 % aprox. en CH4 prod. TAD ranges are small to avoid methanogens inhibition Change of temperature
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EPROBIO Foggia 10 July 2010 GRUP DE RECERCA EN BIOTECNOLOGIA AMBIENTAL DEPARTAMENT D’ENGINYERIA QUÍMICA XARXA DE CENTRES DE SUPORT A LA INNOVACIÓ TECNOLÒGICA Improvement options 3) Two- phase AD
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EPROBIO Foggia 10 July 2010 To keep an equilibrium between acidogenic and methanogenic phases Can be considered as a biological pretreatment of AD Each phase has its own HRT and operting Temperature Keith et al., 2006 AcidogènicMethanogenic Improvement options: 3) two-phase AD
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EPROBIO Foggia 10 July 2010 M-M does not improve too much VS removal, but firts acidogenic phase reduces significantly the pathogenic laod ConfigurationHRT(d)VS rem (%) Meso-Meso3,5+6,550-55 Thermo-Meso2,5+961 Thermo-Thermo2,5 + 563 Improvement options: 3) two-phase AD
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EPROBIO Foggia 10 July 2010 GRUP DE RECERCA EN BIOTECNOLOGIA AMBIENTAL DEPARTAMENT D’ENGINYERIA QUÍMICA XARXA DE CENTRES DE SUPORT A LA INNOVACIÓ TECNOLÒGICA An example with hyperthermophilic conditions was studied by Wang (1997) and Gavala (2003) 1st phase 70ºC MAD TAD Improvements: 30-50% For PS improvements for TAD For SS, improvements for MAD and TAD HRT and T should be fixed for each particular mixture or Improvement options: 3) two-phase AD
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EPROBIO Foggia 10 July 2010 Improvement options: 4) Co- digestion
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EPROBIO Foggia 10 July 2010 Improvement options: 4) Co-digestion SS digesters are infra- used Biodegr. OM (High VS conc. Offers a good opportunity) A single infra-structure is used Eventual nutrient deficit is compensated Eventual inhibitors are diluted Mata et al., 1989
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EPROBIO Foggia 10 July 2010 Mata et al., 1989 IC CAL DIG BIOGAS MEZ FD SEL FORSU Improvement options: 4) Co-digestion
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EPROBIO Foggia 10 July 2010 CONCLUSIONS DA can improve its yields (biogas productions and VS removal and digestate quality) Improvement can be carried out by pretreatments and a significant activity on this field is underway. Improvement options are quite a few and should be carefully studied as many factors are affecting
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EPROBIO Foggia 10 July 2010 CONCLUSIONS Requirements of land application can favour TAD and possibly pre-treatmnes. Directive will have a high influence on these issues. Co-digestion is a logical choice, depending on the surroundings, with important benefits
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EPROBIO Foggia 10 July 2010 jmata@ub.edu
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