Dynamic relationship between dissolved organic matter and soluble microbial products during wastewater treatment

Abstract Dynamics of the dissolved organic matter (DOM) and soluble microbial products (SMP) significantly affected the sustainability of wastewater treatment plants and effluent qualities. In this study, the origin, transformation, and seasonal variation of DOM components in the anaerobic/anoxic/oxic (A2O) units were illustrated with fluorescence analysis. Results show that the anaerobic process transformed humic acid-like substances (HA) and SMP into fulvic acid-like substances (FA) and aromatic proteins (AP), which indicated the decomposition of macromolecules. In cold seasons, the anoxic process turned AP to HA, SMP, and FA; but the oxic process reversed the transformation. In warm seasons, 6.0% of AP decreased while 3.1% of HA, 1.8% of SMP, and 1.0% of FA increased during the oxic process. Proteobacteria strains were isolated from the activated sludge to stimulate the SMP generation, it was found higher temperature facilitated the transformation of FA and HA (humics) to SMP and AP (proteins), which resulted more proteins presented in the wastewater DOM. These findings indicated that the treatment efficiency and DOM quality in A2O processes were influenced by influent quality and/or temperature conditions, and highlighted the generation of SMP by sludge microorganisms, based on which the corresponding strategies considering the seasonal DOM/SMP dynamics were recommended for the stringent regulation of effluents and the sustainability of the receiving water bodies. Besides, the overall fluorescence intensity was positively correlated with the quantified biopolymer contents in SMP, implying the potential of using the fluorescence-derived information to indicate more quantified DOM properties.