22 / 2023-04-28 14:47:48

Regulation of municipal sludge composting by steel slag and KH2PO4 to promote organic matter degradation and humification: Effects of enzyme activity and bacterial community

composting,Humification,Network Analysis,Enzyme activity,Bacterial community.

Chemical additives have received extensive attention in the field of nitrogen retention in composting, but there is currently a lack of relevant research on the effects of composting humification. In order to make full use of chemical additives in improving the humification of compost products, steel slag rich in basic oxides such as iron, calcium, magnesium and manganese was combined with KH₂PO₄ chemical additives to be used as exogenous additives in municipal sludge composting. The characteristics and mechanism of organic matter degradation and humification during aerobic composting of municipal sludge were studied by combining different ratios of steel slag (0%, 5%, 7.5%, and 10%) with KH₂PO₄ as composite additives. After 28 days of composting, compared with phosphate alone, the degradation rate of organic matter in the composite addition group increased by 36.0%~43.1%, indicating that the composite addition had a significant promotion effect on the degradation of organic matter. In addition, the content of humic acid (HA) and the ratio of HA/FA (HA/FA) were higher than those of the control treatment, and the content of HA (37.56g/kg) and HA/FA (1.82) of composite addition of 5% steel slag were higher than those of other treatments especially, indicating that the composite addition had a promoting effect on the humification. Additionally, the EM-PARAFAC method was used to analyze the components of dissolved organic matter; the changes of enzyme activity and microbial community succession were analyzed, and the response mechanism between them and environmental factors was revealed. This study is of great significance to elucidating the roles of composite addition of steel slag and KH₂PO₄ on the enhancement of humification during composting of municipal sludge and its biological mechanism, which provides theoretical basis for optimizing composting quality.