%0 Journal Article
%T Low-Temperature (10¡ãC) Anaerobic Digestion of Dilute Dairy Wastewater in an EGSB Bioreactor: Microbial Community Structure, Population Dynamics, and Kinetics of Methanogenic Populations
%A Katarzyna Bialek
%A Denise Cysneiros
%A Vincent O¡¯Flaherty
%J Archaea
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/346171
%X The feasibility of anaerobic digestion of dairy wastewater at 10¡ãC was investigated in a high height£¿:£¿diameter ratio EGSB reactor. Stable performance was observed at an applied organic loading rate (OLR) of 0.5¨C2£¿kg£¿COD£¿m£¿3£¿d£¿1 with chemical oxygen demand (COD) removal efficiencies above 85%. When applied OLR increased to values above 2£¿kg£¿COD£¿m£¿3£¿d£¿1, biotreatment efficiency deteriorated, with methanogenesis being the rate-limiting step. The bioreactor recovered quickly (3 days) after reduction of the OLR. qPCR results showed a reduction in the abundance of hydrogenotrophic methanogenic Methanomicrobiales and Methanobacteriales throughout the steady state period followed by a sharp increase in their numbers (111-fold) after the load shock. Specific methanogenic activity and maximum substrate utilising rate ( ) of the biomass at the end of trial indicated increased activity and preference towards hydrogenotrophic methanogenesis, which correlated well with the increased abundance of hydrogenotrophic methanogens. Acetoclastic Methanosaeta spp. remained at stable levels throughout the trial. However, increased apparent half-saturation constant ( ) at the end of the trial indicated a decrease in the specific substrate affinity for acetate of the sludge, suggesting that Methanosaeta spp., which have high substrate affinity, started to be outcompeted in the reactor. 1. Introduction During the last decades, there has been an increased concern with the environment and the limited energy sources available. In this context, ways to treat wastewaters with energy saving methods need to be developed. Anaerobic digestion (AD) comes forward in this issue because it can treat several types of wastewaters and produce energy in the form of biogas at the same time. In order to improve the energy balance of AD, its application at low temperatures is an interesting option, especially in northern countries, where the temperatures are much lower than the optimum mesophilic temperature range of the process. The application of low-temperature anaerobic digestion (LTAD) at temperatures of 12¡ãC to 15¡ãC has been studied at laboratory- and pilot-scale granular sludge-based bioreactors [1¨C3]. The possibility of applying the LTAD at 10¡ãC can reduce the operation costs of the plant and improve the energy balance even further. Although LTAD at 10¡ãC has also been studied, to date most studies have examined simple synthetic wastewaters [3]. Up to date there are only few reports describing LTAD of complex (with the presence of particulate compounds) or low-strength recalcitrant
%U http://www.hindawi.com/journals/archaea/2013/346171/