Occurrence,distribution,and potential influencing factors of sewage sludge components derived from nine full-scale wastewater treatment plants of Beijing,China

Millions of tons of waste activated sludge（WAS） produced from biological wastewater treatment processes cause severe adverse environmental consequences. A better understanding of WAS composition is thus very critical for sustainable sludge management. In this work, the occurrence and distribution of several fundamental sludge constituents were explored in WAS samples from nine full-scale wastewater treatment plants（WWTPs） of Beijing, China. Among all the components investigated, active heterotrophic biomass was dominant in the samples（up to 9478 mg/L）, followed by endogenous residues（6736 mg/L）,extracellular polymeric substances（2088 mg/L）, and intracellular storage products（464 mg/L）among others. Moreover, significant differences（p 〈 0.05） were observed in composition profiles of sludge samples among the studied WWTPs. To identify the potential parameters affecting the variable fractions of sludge components, wastewater source as well as design and operational parameters of WWTPs were studied using statistical methods. The findings indicated that the component fraction of sewage sludge depends more on wastewater treatment alternatives than on wastewater characteristics among other parameters. A principal component analysis was conducted, which further indicated that there was a greater proportion of residual inert biomass in the sludge produced by the combined system of the conventional anaerobic/anoxic/oxic process and a membrane bioreactor. Additionally, a much longer solids retention time was also found to influence the sludge composition and induce an increase in both endogenous inert residues and extracellular polymeric substances in the sludge.

Relationship between physicochemical properties and dewaterability of hydrothermal sludge derived from different source

Sewage sludge（SS） and deinking sludge（DS） were used to comparatively study the hydrothermal dewatering of sludge with different components. For a better overview, an insight into the relationship between physicochemical properties and dewaterability of hydrothermal sludge was provided. Results found that not all kinds of sludge were suitably conditioned by hydrothermal treatment（HT） in term of the elevation of dewaterability.Higher hydrothermal temperature tended to enhance the dewaterability of SS rather than DS, which was supported by the variation of their physicochemical properties（including water distribution, bonding energy, extracellular polymeric substance（EPS）, particles size,acid functional groups and zeta potential in this study）. In addition, the changes in surface morphology suggested that the reverse effect of HT on sludge dewaterability was mainly due to their dewatering behavior. For SS, the destruction of EPS structure leaded to the release of bound water, thereby strengthening sludge dewatering. Conversely, ＂Bridging effect＂ generated by lignocellulose in DS was beneficial for sludge dewatering; however, the increasing hydrothermal temperature degraded part of lignocellulose and weakened＂bridging effect＂, finally resulting in worse dewaterability of DS.