title: Experiences with the dual digestion of municipal sewage sludge.
abstract: The dual digestion process was investigated using sludge samples collected at the WWTP of Tomaszow Mazowiecki (Poland). Mixed sludge was treated in a laboratory setup under batch and semi-continuous conditions. Dual digestion with a 1d SRT aerobic thermophilic pretreatment followed by an anaerobic step with 20 d of SRT turned out to be optimal, since a 44-46% VS reduction and a biogas yield of 480 dm(3)/kg VS fed were achieved. In the course of the process, the concentration of nitrogen in supernatant increased over 5 times and its major portion was converted into ammonia. Phosphorus also entered the supernatant, reaching over 200 g/m(3). The dual digestion noticeably deteriorated the sludge dewaterability. Following completion of the process, capillary suction time measurements averaged 64 s for the raw sludge, 400 s for aerobically pretreated sludge and 310-360 for the anaerobically digested sludge. Aerobic pretreatment consistently reduced Enterobacteriaceae content to below detectable limits.
authors.affiliation: Technical University of Lodz, Institute of Fermentation Technology and Microbiology, ul. Wólczańska 171/173, 90-924 Łódź, Poland. sebasbor@poczta.onet.pl
authors.forename: Sebastian
authors.initials: S
authors.lastname: Borowski
authors.forename: Józef Stanisław
authors.initials: JS
authors.lastname: Szopa
mesh_terms: D000332:Aerobiosis; D004926:Escherichia coli / Q000378:metabolism; D012475:Salmonella / Q000378:metabolism; D012722:Sewage / Q000382:microbiology
chemical_list: D012722:Sewage