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Methanogenic population dynamics during start‐up of anaerobic digesters treating municipal solid waste and biosolids
Author(s) -
Griffin Matt E.,
McMahon Katherine D.,
Mackie Roderick I.,
Raskin Lutgarde
Publication year - 1998
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/(sici)1097-0290(19980205)57:3<342::aid-bit11>3.0.co;2-i
Subject(s) - mesophile , anaerobic digestion , population , biogas , methanosaeta , biosolids , sewage sludge , propionate , food science , chemistry , pulp and paper industry , manure , methanogenesis , volatile suspended solids , methane , biology , sewage treatment , chemical oxygen demand , environmental science , environmental engineering , bacteria , agronomy , biochemistry , ecology , medicine , genetics , environmental health , organic chemistry , engineering
An aggressive start‐up strategy was used to initiate codigestion in two anaerobic, continuously mixed bench‐top reactors at mesophilic (37°C) and thermophilic (55°C) conditions. The digesters were inoculated with mesophilic anaerobic sewage sludge and cattle manure and were fed a mixture of simulated municipal solid waste and biosolids in proportions that reflect U.S. production rates. The design organic loading rate was 3.1 kg volatile solids/m 3 /day and the retention time was 20 days. Ribosomal RNA‐targeted oligonucleotide probes were used to determine the methanogenic community structure in the inocula and the digesters. Chemical analyses were performed to evaluate digester performance. The aggressive start‐up strategy was successful for the thermophilic reactor, despite the use of a mesophilic inoculum. After a short start‐up period (20 days), stable performance was observed with high gas production rates (1.52 m 3 /m 3 /day), high levels of methane in the biogas (59%), and substantial volatile solids (54%) and cellulose (58%) removals. In contrast, the mesophilic digester did not respond favorably to the start‐up method. The concentrations of volatile fatty acids increased dramatically and pH control was difficult. After several weeks of operation, the mesophilic digester became more stable, but propionate levels remained very high. Methanogenic population dynamics correlated well with performance measures. Large fluctuations were observed in methanogenic population levels during the start‐up period as volatile fatty acids accumulated and were subsequently consumed. Methanosaeta species were the most abundant methanogens in the inoculum, but their levels decreased rapidly as acetate built up. The increase in acetate levels was paralleled by an increase in Methanosarcina species abundance (up to 11.6 and 4.8% of total ribosomal RNA consisted of Methanosarcina species ribosomal RNA in mesophilic and thermophilic digesters, respectively). Methanobacteriaceae were the most abundant hydrogenotrophic methanogens in both digesters, but their levels were higher in the thermophilic digester. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 342–355 1998.