Effects of temperature and hydraulic retention time on acetotrophic pathways and performance in high-rate sludge digestion.

High-rate anaerobic digestion of organic solids requires rapid hydrolysis and enhanced methanogenic growth rates, which can be achieved through elevated temperature (>55 °C) at short hydraulic retention times (HRT). This study assesses the effect of temperatures between 55 °C and 65 °C and HRTs between 2 and 4 days on process performance, microbial community structure, microbial capability, and acetotrophic pathways in thermophilic anaerobic reactors. Increasing the temperature did not enhance volatile solids (VS) destruction above the base value of 37% achieved at 55 °C and 4 days HRT. Stable isotopic signatures (δ13C) revealed that elevated temperature promoted syntrophic acetate oxidation, which accounted for 60% of the methane formation at 55 °C, and increasing substantially to 100% at 65 °C. The acetate consumption capacity dropped with increasing temperature (from 0.69-0.81 gCOD gVS(-1) d(-1) at 55 °C to 0.21-0.35 gCOD gVS(-1) d(-1) at 65 °C), based on specific activity testing of reactor contents. Community analysis using 16S rRNA pyrosequencing revealed the dominance of Methanosarcina at 55-60 °C. However, a further increase to 65 °C resulted in loss of Methanosarcina, with an accumulation of organic acids and reduced methane production. Similar issues were observed when reducing the HRT to 2 days, indicating that temperature<60 °C and HRT>3 days are critical to operate these systems stably.

[1]  Damien J. Batstone,et al.  Methanosarcinaceae and Acetate-Oxidizing Pathways Dominate in High-Rate Thermophilic Anaerobic Digestion of Waste-Activated Sludge , 2013, Applied and Environmental Microbiology.

[2]  W. Gujer,et al.  Mathematical model for meso- and thermophilic anaerobic sewage sludge digestion. , 2002, Environmental science & technology.

[3]  J la Cour Jansen,et al.  Hygienization of sludge through anaerobic digestion at 35, 55 and 60 °C. , 2013, Water science and technology : a journal of the International Association on Water Pollution Research.

[4]  S. Haruta,et al.  Methanogenic pathway and community structure in a thermophilic anaerobic digestion process of organic solid waste. , 2011, Journal of bioscience and bioengineering.

[5]  A. Stams,et al.  Thermotoga lettingae sp. nov., a novel thermophilic, methanol-degrading bacterium isolated from a thermophilic anaerobic reactor. , 2002, International journal of systematic and evolutionary microbiology.

[6]  H. D. Stensel,et al.  Wastewater Engineering: Treatment and Reuse , 2002 .

[7]  R. Conrad.  Quantification of methanogenic pathways using stable carbon isotopic signatures: a review and a proposal , 2005 .

[8]  Rob Whyte,et al.  A rough guide to anaerobic digestion costs and MSW diversion , 2001 .

[9]  D. Batstone,et al.  4.17 – Anaerobic Processes , 2011 .

[10]  Pinjing He,et al.  Predominant contribution of syntrophic acetate oxidation to thermophilic methane formation at high acetate concentrations. , 2011, Environmental science & technology.

[11]  Yue-Qin Tang,et al.  Effect of temperature on microbial community of a glucose-degrading methanogenic consortium under hyperthermophilic chemostat cultivation. , 2008, Journal of bioscience and bioengineering.

[12]  Irini Angelidaki,et al.  Acetate Oxidation Is the Dominant Methanogenic Pathway from Acetate in the Absence of Methanosaetaceae , 2006, Applied and Environmental Microbiology.

[13]  A. Schnürer,et al.  Syntrophaceticus schinkii gen. nov., sp. nov., an anaerobic, syntrophic acetate-oxidizing bacterium isolated from a mesophilic anaerobic filter. , 2010, FEMS microbiology letters.

[14]  Xavier Font,et al.  Long term operation of a thermophilic anaerobic reactor: process stability and efficiency at decreasing sludge retention time. , 2010, Bioresource technology.

[15]  B. Demirel,et al.  The roles of acetotrophic and hydrogenotrophic methanogens during anaerobic conversion of biomass to methane: a review , 2008 .

[16]  B. Schink,et al.  Clostridium ultunense sp. nov., a mesophilic bacterium oxidizing acetate in syntrophic association with a hydrogenotrophic methanogenic bacterium. , 1996, International journal of systematic bacteriology.

[17]  F. Chen,et al.  Experimental factors affecting PCR-based estimates of microbial species richness and evenness , 2010, The ISME Journal.

[18]  Maria Westerholm,et al.  Tepidanaerobacter acetatoxydans sp. nov., an anaerobic, syntrophic acetate-oxidizing bacterium isolated from two ammonium-enriched mesophilic methanogenic processes. , 2011, Systematic and applied microbiology.

[19]  Damien J Batstone,et al.  Temperature phased anaerobic digestion increases apparent hydrolysis rate for waste activated sludge. , 2011, Water research.

[20]  William A. Walters,et al.  QIIME allows analysis of high-throughput community sequencing data , 2010, Nature Methods.

[21]  S. Schmidt,et al.  Anaerobic Digestion of Renewable Biomass: Thermophilic Temperature Governs Methanogen Population Dynamics , 2010, Applied and Environmental Microbiology.

[22]  A. Noyola,et al.  Two-phase (acidogenic-methanogenic) anaerobic thermophilic/mesophilic digestion system for producing Class A biosolids from municipal sludge. , 2010, Bioresource technology.

[23]  Jules B. van Lier,et al.  Effect of temperature on the anaerobic thermophilic conversion of volatile fatty acids by dispersed and granular sludge. , 1996 .

[24]  A. Guwy,et al.  Defining the biomethane potential (BMP) of solid organic wastes and energy crops: a proposed protocol for batch assays. , 2009, Water science and technology : a journal of the International Association on Water Pollution Research.

[25]  Paolo Pavan,et al.  High rate mesophilic, thermophilic, and temperature phased anaerobic digestion of waste activated sludge: a pilot scale study. , 2012, Waste management.

[26]  S. Zinder,et al.  Hydrogen Partial Pressures in a Thermophilic Acetate-Oxidizing Methanogenic Coculture , 1988, Applied and environmental microbiology.

[27]  D J Batstone,et al.  Assessing the role of biochemical methane potential tests in determining anaerobic degradability rate and extent. , 2011, Water science and technology : a journal of the International Association on Water Pollution Research.

[28]  Jing Liu,et al.  Effects of solid retention time on anaerobic digestion of dewatered-sewage sludge in mesophilic and thermophilic conditions , 2010 .

[29]  T. R. Sreekrishnan,et al.  Anaerobic digestion from the viewpoint of microbiological, chemical, and operational aspects — a review , 2010 .