Effect of nitrite on hydrolysis-acidification, biogas production and microbial community in semi-continuous two-phase anaerobic digestion of sewage sludge

Previous study found that the pre-treatment of sewage sludge with nitrite improves the biogas production during the mono/two-phase anaerobic digestion (AD) using batch biochemical methane potential tests. In this study, the effects of nitrite on hydrolysis -acidification, biogas production, volatile solids destruction and microbial composition in semi-continuous two-phase AD of sewage sludge were investigated. The addition of nitrite promotes sludge organic matter solubilization ( + 484%) and VFAs production ( + 98.9%), and causes an increase in the VS degradation rate during the AD process ( + 8.7%). The compar-ison of biogas production from the acidogenic and methanogenic reactors with or with-out the addition of nitrite implies that the nitrite has no significant effect on the over-all biogas production of two-phase sludge AD process. High-throughput sequencing anal-ysis shows that the microbial communities of bacteria and archaea in two-phase AD re-actors significantly changes after the addition of nitrite. Vulcanibacillus (bacteria) and Can-didatus Methanofastidiosum (archaea) become the dominant genera in the acidogenic and methanogenic reactors with the nitrite respectively. These findings provide new insights about using nitrite to promote the organic matter degradation of sewage sludge in a semi -continuous two-phase AD system. (c) 2022 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.