Modřice Plant Anaerobic Digester: Microbial Distribution and Biogas Production

Abstract

Biogas reactors are now a common part of wastewater treatment systems. The quality of produced biogas is the result of many factors, mainly the input substrate and microbial composition of the bioreactor. The aim of this research was to evaluate the microbial community of the Modřice biogas reactor together with the possible changes in biogas composition. The key microbial groups and their content in anaerobic digester were identified by sequencing techniques. The most dominant group were sulphate-reducing (45%), followed by methanogenic (19%), acetate (6%) and hydrogen-producing (11%) microorganisms. The remaining microorganisms were identified only to their order (19%). Phylogenetic trees were constructed to show evolutionary relationships of detected microorganisms. The volume of methane in biogas content was 60%, which corresponds with literature data regarding sewage digesters. None of the detected impurities have crossed the safe limits and their volume remained stable during the measurement period. Despite sulphate-reducing bacteria being the dominant group, their produced hydrogen sulphide (H2S) was detected only in a small quantity (2.43–7.46 ppm) and had no inhibitory effect on the methane production. The mechanism of inhibition by H2S and the perspective of its biological removal were discussed. Application of phototrophic sulphur bacteria, especially Chlorobiaceae and Chromatiaceae family, and the creation of new photobioreactor systems can be a promising pathway for hydrogen sulphide treatment in biogas plants.