Study on UV–Visible Spectra Characteristic of Dissolved Organic Matter during Municipal Solid Waste Composting

This paper aims to characterize the evolution of organic matter during the composting of municipal solid waste (MSW). During the 46-day composting process, six samples with different composting time were collected from Songjiang Solid Waste Biological Treatment Plant in Shanghai, China. Dissolved organic matter (DOM) was extracted by ultra-pure water, and the UV-Visible (UV-Vis) spectra of DOM were scanned and investigated. The results showed that, during the composting process, non-humus substances in DOM were gradually transformed into humus substances, the aromatization, molecular weight and humification of humus substances increased. Correlation analysis showed that the absorbance value at 280 nm (SUVA280), and the area of 226~400 nm (A226~400) correlated positively with each other. The dissolved organic carbon (DOC) concentration exhibited a negative correlation with the parameters S275~295, SUVA280 and A200~226, and the correlation coefficients between the DOC content and the A220~226 value was the best (r= -0.976, P=0.001). The absorbance ratio bewteen 465 and 665 nm (E465/E665) showed a significant correlation with SUVA280 (r=-0.892, P=0.017), A226~400 (r=-0.909, P=0.012) and DOC (r=0.840, P=0.036). The absorbance ratio of 250 to 365 nm (E250/E365) correlated significantly with DOC (r=-0.880, P=0.021), and showed no correlation with the other parameters. Absorption curve slope in the range of 275~295nm (S275~295) showed a significantly positive correlation with the DOC content (r=0.961, P=0.002). Among all parameters, the A200~226, A226~400 and S275~295 values reflected compost maturity best.