Characterization of Dissolved Organic Matter from Effluents in a Dry Anaerobic Digestion Process Using Spectroscopic Techniques and Multivariate Statistical Analysis

Abstract

Dissolved organic matter (DOM) collected from a garage-type dry fermentation system was investigated using UV-Vis absorption and fluorescence spectroscopy. Spectral parameters A 253/203 , biological index and fluorescence index were used to assess the structural characteristics and sources of effluent DOM. The results showed that aromatic rings highly substituted with hydroxyl, carbonyl, ester and carboxylic groups were obtained in the aerobic decomposition stage, and microbially derived organic matter dominated in the dry anaerobic digestion process, suggesting that the hydrolysis of organic macromolecules (lignin) in the aerobic decomposition resulted in the formation of water-soluble intermediates which can be easily assimilated and metabolized by microbial cells in dry anaerobic digestion process. PARAFAC of the excitation-emission matrix spectra revealed five fluorescent components occurring in effluent DOM: four humic-like components (C1-C4) and one protein-like component (C5). The F max values of components 1, 2, 3 and 5 showed large fluctuation than that of component C4, suggested the formation and degradation of these components. Component C4, with high aromatic content and higher degree of humification, was more difficult to be utilized and degraded by microorganisms than other components. The PAR-AFAC-PCA displayed three PCA factors (factors 1, 2 and 3), which accounted for 34.51, 34.20 and 31.11 %, respectively, of the variance in fluorescent components. Humic-like component C4 showed positive factor 1 loadings. Factor 2 was mainly explained by the tryptophan-like component C5. The humic-like components 1, 2 and 3 concurrently showed a relatively high factor 3 loading. The PARAFAC-PCA in this study could separate the characteristics of the DOM fluorescent component namely the source strength of the humic-like components versus the contributions of protein-like components in the total fluorescence analyses.

Improving Soil Fertility and Nutrient Dynamics with Leachate Attributes from Sewage Sludge by Impoundment and Co‐Composting

“…Since this soil has been continuously exposed to excess sludge ponding, it is visually observed that physicochemical modifications have occurred in the soil structure and texture over the O‐horizon. [ 38 ] It is also believed that the degradation phase for the organic matter by the soil microbes under the ponded situation with excess sludge inflow can be rate‐limited as per the Monod's assumptions on food‐biomass ratio. However, the availability of nutrients in the soil after the organic amending depends on the biochemical and pedo‐climatic conditions.…”