EPROBIO Foggia 10 July 2010 Environmental Aspects of AD of Sewage Sludge

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

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

EPROBIO Foggia 10 July 2010 Options to improve AD

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)

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

EPROBIO Foggia 10 July 2010 Improvement options: 1) pre- treatment

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 ( kJ/kg) TT (145ºC/ 30 min) MAD PS SS TAD PS SS Improvement options: 1) pre-treatments

EPROBIO Foggia 10 July PPCP’s 9 (Esplugas, M. 2010)

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

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

EPROBIO Foggia 10 July 2010 Improvement options: 2 Temperature

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

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

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

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

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, Thermo-Meso2,5+961 Thermo-Thermo2, Improvement options: 3) two-phase AD

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

EPROBIO Foggia 10 July 2010 Improvement options: 4) Co- digestion

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

EPROBIO Foggia 10 July 2010 Mata et al., 1989 IC CAL DIG BIOGAS MEZ FD SEL FORSU Improvement options: 4) Co-digestion

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

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

EPROBIO Foggia 10 July 2010