Aerobic thermophilic bacteria enhance biogas production

Abstract

The enhancing effect of aerobic thermophilic (AT) bacteria on the production of biogas from anaerobically digested sewage sludge (methanogenic sludge) was investigated. Sewage sludge (5%, w/w) was incubated at 65°C with shaking for a few months to prepare the AT seed sludge. AT sludge was prepared by incubation of the AT seed sludge (5%, v/v) and sewage sludge (5%, w/w) at 65°C with shaking. The addition of this AT sludge (1.2% Ϯ 0.5% of total volatile solids) to methanogenic sludge enhanced the production of biogas. The optimum volume of the addition and the pretreatment temperature of the AT sludge for optimum biogas production were 5% (v/v) and 65°C. Batchfed anaerobic digestion was covered with the addition of various AT sludges. The AT sludge prepared with the AT seed sludge improved the biogas production by 2.2 times relative to that from the sewage sludge addition. The addition of sludge without AT seed sludge weakly enhanced biogas production. An aerobic thermophilic bacterium (strain AT1) was isolated from the AT seed sludge. Strain AT1 grew well in a synthetic medium. The production of biogas from the anaerobic digestion of sewage sludge was improved by the addition of 5% (v/v) AT1 bacterial culture compared with that from the sewage sludge addition. The addition of AT1 culture reduced the volatile solids by 21%, which was higher than the 12.6% achieved with the sewage sludge addition. The AT1 bacterial culture enhanced the biogas production more than the AT seed sludge. The phylogenetic analysis of the 16 S rRNA gene revealed that strain AT1 is closely related to Geobacillus thermodenitrificans (100% sequence similarity). The improvement in the production of biogas with the AT sludge could be caused by thermophilic bacterial activity in the AT sludge.

Effect of pre-aeration and inoculum on the start-up of batch thermophilic anaerobic digestion of municipal solid waste

“…One could expect two effects of the aerobic pre-treatment: (a) aerobic hydrolytic exo-enzymes secreted by thermophilic aerobic bacteria provide methanogenic metabolites which would benefit methane production (Borowski and Szopa, 2007;Capela et al, 1999;Hasegawa and Katsura, 1999;Miah et al, 2005). (b) aerobic oxidation exhaust the easy-to-degrade component of the starting material (oxidation to CO 2 ) which would otherwise have been used by anaerobic microbes to generate methane (Krzystek et al, 2001).…”

The isolation, identification of sludge-lysing thermophilic bacteria and its utilization in solubilization for excess sludge

“…The scanning electron microscopy image of the thermophilic bacterium AT07-1 is shown in Figure 2. Some early studies had reported that the bacteria which dissolved sludge effectively were mostly thermophilic bacteria Bacillus [20,31]. On the agar plate, AT07-1 produced semi-transparent, edge-irregular, convex, smooth surface and shallow cleft light gray colonies.…”

Bioaugmentation of biogas production by a hydrogen-producing bacterium

“…Several methods have been suggested for the intensification of biogas productivity, e.g. the facilitation of biomass decomposition by means of various pretreatments, modification of the composition of the microbial community, or conduction of the various anaerobic digestion (AD) phases in separate reactors (Divya, 2015;Miah, 2005;Weiß, 2010).…”