81 / 2021-06-30 17:40:59

Effect of sewage sludge addition on physicochemical properties and microbial community during the pilot-scale composting of distilled grain waste

Distilled grain waste; Sewage sludge; Composting; Maturity; Microbial communities

Distilled grain waste (DGW) is the main solid by-product of the Chinese spirit-making process. Sewage sludge contains many microorganisms and is another main solid waste generating in winery industry. Composting is an efficient and economical approach used to convert organic waste into stable organic fertilizers and soil conditioner. This study compared the DGW composting process with (DSS) or without (D) sewage sludge addition with a focus on physicochemical properties and microbial community structures. Results showed that sewage sludge addition remarkedly improved the maximum pile temperature, organic matter degradation (59.80 vs. 54.13%), maturity (germinate index, 129.83 vs. 113.61%), as well as the nutrients of end-products (N+P₂O₅+K₂O, 8.08 vs. 5.14%) compared to D. At the end of composting, the final compost in both treatments met the requirements of Chinese National Agricultural Organic Fertilizer Standard (NY525-2012). Shannon and Chao1 indices showed that sewage sludge supplementation improved the bacterial community diversity and richness. Veen diagram showed that 227 unique genera were identified in DSS, while only 5 unique genera were identified in D. Principal coordinate analysis and Hierarchical clustering revealed that adding sewage sludge could accelerate the succession of bacterial community. The dominant phyla in both treatments included Firmicutes, Proteobacteria, Actinobacteriota, Bacteroidota, Chloroflexi, Deinococcota, and Planctomycetota, whose abundance varied with composting time. Keystone bacterial such as Bacillus, Planifilum, Saccharopolyspora, Saccharomonospora, Pseudomonas, Galbibacter, norank_f_Limnochordaceae, and Luteimonas were abundant in DSS and D. Co-occurrence network analysis revealed a significant relationship between keystone microbes and physicochemical properties in both treatments. Overall, sewage sludge supplementation could accelerate the succession of bacterial community, promote organic matter degradation, and improved the end-compost quality.