23 / 2023-04-28 16:49:08

Accelerated humification and alteration of microbial communities by MnO2 addition during sludge straw co-composting

Sludge composting,Manganese dioxide,EEM-PARAFAC,Humification,Bacterial community

Low degree of humification and long process cycle in municipal sludge composting urgently need to be addressed. This study investigates the impact of MnO₂ addition on organic matter degradation and humification in sludge composting. The composition of dissolved organic matter and maturity index were analyzed by the fluorescence excitation emission matrix spectroscopy(3D-EEM) and parallel factor analysis (PARAFAC). High-throughput sequencing and redundancy analysis were employed for revealing the structure dynamics for microbial community and their shaping factors, respectively .Results indicated that addition of MnO₂ prolonged the high-temperature period of composting, promoted the degradation of organic matter, and increased the degree of humification. Compared with the control group, the degradation rate of organic matter in the MnO₂ treatment group increased by 8.61%-11.2%, and the content of humic acid increased by 6.51%. 3D-EEM spectral analysis showed that MnO₂ accelerated the formation of humic substances (HS), while PARAFAC analysis indicated that MnO₂ promoted the increase of humus-like components .Microbial community analysis showed that MnO₂ altered the structure of bacterial communities, promoting the enrichment of dominant bacterial groups for recalcitrant organic compounds, particularly the Actinobacteria and Firmicutes phyla .Redundancy analysis (RDA) indicated that fulvic acid (FA) was the most significant environmental factor affecting the evolution of microbial communities during the co-composting process of sludge and straw, followed by electrical conductivity and temperature.Furthermore, The genus SBR1031 of the Chloroflexi phylum was positively correlated with HA and negatively correlated with FA,which indicated that SBR1031 was a key bacterial genus in the transformation process of FA and HA. These results showed that addition of MnO₂ effectively improved the humification degree of composting and changed the microbial communities of composting during the process of municipal sludge composting .