title: Temperature phased anaerobic digestion increases apparent hydrolysis rate for waste activated sludge.
abstract: It is well established that waste activated sludge with an extended sludge age is inherently slow to degrade with a low extent of degradation. Pre-treatment methods can be used prior to anaerobic digestion to improve the efficiency of activated sludge digestion. Among these pre-treatment methods, temperature phased anaerobic digestion (TPAD) is one promising method with a relatively low energy input and capital cost. In this study, an experimental thermophilic (50-70 °C)-mesophilic system was compared against a control mesophilic-mesophilic system. The thermophilic-mesophilic system achieved 41% and 48% volatile solids (VS) destruction during pre-treatment of 60 °C and 65 °C (or 70 °C) respectively, compared to 37% in the mesophilic-mesophilic TPAD system. Solubilisation in the first stage was enhanced during thermophilic pre-treatment (15% at 50 °C and 27% at 60 °C, 65 °C and 70 °C) over mesophilic pre-treatment (7%) according to a COD balance. This was supported by ammonia-nitrogen measurements. Model based analysis indicated that the mechanism for increased performance was due to an increase in hydrolysis coefficient under thermophilic pre-treatment of 60 °C (0.5 ± 0.1 d(-1)), 65 °C (0.7 ± 0.2 d(-1)) and 70 °C (0.8 ± 0.2 d(-1)) over mesophilic pre-treatment (0.2 ± 0.1 d(-1)), and thermophilic pre-treatment at 50 °C (0.12 ± 0.06 d(-1)).
authors.affiliation: Advanced Water Management Centre (AWMC), Environmental Biotechnology CRC, The University of Queensland, St Lucia, QLD 4072, Australia.
authors.forename: Huoqing
authors.initials: H
authors.lastname: Ge
authors.forename: Paul D
authors.initials: PD
authors.lastname: Jensen
authors.forename: Damien J
authors.initials: DJ
authors.lastname: Batstone
mesh_terms: D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D016001:Confidence Intervals; D005232:Fatty Acids, Volatile / Q000032:analysis; D006868:Hydrolysis; D008697:Methane / Q000032:analysis; D008956:Models, Chemical; D009584:Nitrogen / Q000032:analysis; D000644:Quaternary Ammonium Compounds / Q000032:analysis; D012037:Refuse Disposal / Q000295:instrumentation / Q000379:methods*; D012722:Sewage / Q000382:microbiology*; D012995:Solubility; D013696:Temperature; D014835:Volatilization; D014866:Waste Products / Q000032:analysis*
chemical_list: D005232:Fatty Acids, Volatile; D000644:Quaternary Ammonium Compounds; D012722:Sewage; D014866:Waste Products; D009584:Nitrogen; D008697:Methane