Changes in Enzyme Activity and Bacterial Succession during Sewage Sludge Composting

Abstract

To study the variations in microorganisms and enzyme activity during sewage sludge composting, the dynamic changes in temperature, enzyme activity and microorganism composition were studied by co-composting municipal sludge and corn straw. The results show that the pile underwent mesophilic, thermophilic, and cooling phases and that the high-temperature duration (Â 50 °C) had reached 5 days, which meets harmlessness requirements. During the composting process, the protease, arylsulfatase (ARS) and cellulase content increased gradually; urease content first decreased and then increased rapidly; and peroxidase (POD) content first increased and then decreased. Ureibacillus, Bacillus, Pseudomonas, Flavobacterium and Sporosarcina were the dominant bacteria during sludge composting. Microorganisms played different roles at different stages of the composting. Ureibacillus and Bacillus were the dominant strains in the mesophilic and thermophilic phases, respectively, and Pseudomonas and Flavobacterium were the dominant strains in the cooling phase. Sporosarcina mainly played a role later in the thermophilic and cooling phases. The effect of different bacteria on enzyme activity varied; Pseudomonas played a clear role in promoting the production of urease while Bacillus had a clear inhibitory effect on the production of urease. Ureibacillus inhibited the production of ARS, POD, protease and cellulase. By studying the changes in microbial and enzymatic activities at different stages of sludge composting, it is possible to thoroughly explore the nature of the latter and provide a reference for optimizing composting processes.