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Environmental Aspects of AD of Sewage Sludge

Environmental Aspects of AD of Sewage Sludge. BIOSOLIDS. DEWATERING. LANDFILL. ATAD. LAND APPLICATION. ANAEROBIC DIGESTION. THERMAL DRYING. BIO-DRYING. DEWATERING. COMPOSTING. CEMENT FACTORY. INCINERATION. CO-DIGESTION. GASIFICATION. CLAY FACTORY. OTHER ORGANIC WASTES. Ashes.

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Environmental Aspects of AD of Sewage Sludge

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  1. Environmental Aspects of AD of Sewage Sludge

  2. BIOSOLIDS DEWATERING LANDFILL ATAD LAND APPLICATION ANAEROBIC DIGESTION THERMAL DRYING BIO-DRYING DEWATERING COMPOSTING CEMENT FACTORY INCINERATION CO-DIGESTION GASIFICATION CLAY FACTORY OTHER ORGANIC WASTES Ashes LANDFILL

  3. BIOSOLIDS DEWATERING LANDFILL ATAD LAND APPLICATION • ANAEROBIC DIGESTION • First application of AD • Advantages • Possibilities (heat / power) • Configurations to improve the performance • Co-digestion ANAEROBIC DIGESTION THERMAL DRYING BIO-DRYING DEWATERING COMPOSTING CEMENT FACTORY INCINERATION CO-DIGESTION GASIFICATION CLAY FACTORY OTHER ORGANIC WASTES Ashes LANDFILL

  4. Options to improve AD

  5. Options to improve AD process 1) Hydrolysis: Pretreatments 2) Temperature: TAD At anyoption, theimprovementwilldependon: - Sludgecharacteristics (PS/SS) - HRT used - Temperature of operation (normally MAD) • Thermal • Mechanical (ultrasonic) • Chemical (ozonation, H2O2,etc.) • Biological (enzymatic) • Increase T of AD to reduce HRT and to incrase OLR 4) Nutrient balance 3) Balance between acidogenic and methanogenic step • Co-digestion with other wastes • Two-phase digestion

  6. Improvement options: 1) pre-treatments Mechanical Biological Thermal Chemical • Severaleffects: • Solubilization • Degradation • Improvent of biodegradability Twointerest: Increasedbiogasyield Less residual sludge

  7. Improvement options: 1) pre-treatment

  8. Improvement options: 1) pre-treatments TREAMENTS ULTRASONIC vs THERMAL Increase (%) on methane production • More effectiveness: • - Mesofílic conditions - For secondary sludge • Difference on Investment and operating costs.

  9. PPCP’s (Esplugas, M. 2010) 9

  10. Improvement options: 1) pre-treatments * AOX, LAS, PCB’s, PAH, DEHP, NP/NPE Theirremoval has beenstudiedunderdifferentoperatingconditions * Results are complex as depend of thecontaminant and conditions * In any case thereisanimprovement SS PS 55-71% 53-65% Removal or transformation (%) of NPE and DEHP with US (■) and TT (■) pretreatments

  11. (a) (b) Improvement options: 1) pre-treatments * AOX, LAS, PCB’s, PAH, DEHP, NP/NPE Theirremoval has beenstudiedunderdifferentoperatingconditions * Results are complex as depend of thecontaminant and conditions * In any case thereisanimprovement DEHP NPE

  12. Improvement options: 2 Temperature

  13. Thermophilic vs. Mesophilic AD • Pathogenremovalhigher in TAD (BiosolidsClass A) • Betterremoval of Microcontamiinats % (AOX, LAS, PCB’s, PAH, DEHP, NP/E) At low HRT TAD yields are much higher At high HRT yields are similar Valuesdependontype of sludge - Worsedewaterability - More VFA in supernatants

  14. Incr. 50 % aprox. en CH4 prod. Change of temperature Temperature range alternance (Tartakovsky et al. 2007) TAD ranges are small to avoid methanogens inhibition

  15. Improvement options 3) Two-phase AD XARXA DE CENTRES DE SUPORT A LA INNOVACIÓ TECNOLÒGICA DEPARTAMENT D’ENGINYERIA QUÍMICA GRUP DE RECERCA EN BIOTECNOLOGIA AMBIENTAL

  16. Improvement options: 3) two-phase AD To keepanequilibriumbetweenacidogenic and methanogenicphases Can be considered as a biologicalpretreatment of AD Eachphase has itsown HRT and opertingTemperature Acidogènic Methanogenic Keith et al., 2006

  17. Improvement options: 3) two-phase AD M-M does not improve too much VS removal, but firts acidogenic phase reduces significantly the pathogenic laod

  18. Improvement options: 3) two-phase AD MAD An example with hyperthermophilic conditions was studied by Wang (1997) and Gavala (2003) 1st phase 70ºC or 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 XARXA DE CENTRES DE SUPORT A LA INNOVACIÓ TECNOLÒGICA DEPARTAMENT D’ENGINYERIA QUÍMICA GRUP DE RECERCA EN BIOTECNOLOGIA AMBIENTAL

  19. Improvement options: 4) Co-digestion

  20. Improvement options: 4) Co-digestion • Eventual nutrient deficit is compensated • Eventual inhibitors are diluted • SS digesters are infra-used • Biodegr. OM (High VS conc. Offers a goodopportunity) • A single infra-structureisused Mata et al., 1989

  21. Improvement options: 4) Co-digestion BIOGAS CAL FD MEZ IC DIG SEL FORSU Mata et al., 1989

  22. 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

  23. 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

  24. jmata@ub.edu

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