Effect of municipal sludge/blue-green algae ratio on thermophilic aerobic composting and its dissolved organic matter dynamic process

This work evaluated the performance of thermophilic aerobic co-composting of municipal sludge and blue-green algae and explored the dissolved organic matter dynamic evolution simultaneously. The results of 28-day monitoring demonstrated that the addition of blue-green algae greatly upgraded the municipal sludge thermophilic aerobic composting performance with the highest microcystin removal efficiency averaging 94.9%, germination index over 90% and moisture content below 45% at municipal sludge: blue-green algae ratio of 4:1. The synergistic effect of municipal sludge and blue-green algae enhanced microbial activity through creating a better aerobic composting environment and, therefore, improved the permeability of the input streams. Three-dimensional excitation-emission matrix spectra of the input streams were resolved by the parallel factor analysis model, and the main components were humic acid-like (Component 1), fulvic acid-like (Component 2), tryptophan-like (Component 3), and tyrosine-like (Component 4). In addition, the relative F_max of Component 1 and Component 2 increased during aerobic composting, while the F_max of Component 3 and Component 4 decreased sharply. The variation indicated that aerobic co-composting could enhance the decomposition of protein-like substances and promote the generation of humus-like substances, thus leading to the increased humification. Hence, the aerobic co-composting of municipal sludge and blue-green algae provided important theoretical support for the scale-up engineering treatment of MS.