Acclimation of 2-chlorophenol Biodegrading Activated Sludge and Microbial Community Analysis

Insight investigation of the on-site activated sludge reduction induced by metabolic uncoupler: Effects of 2,6-dichlorophenol on soluble microbial products, microbial activity, and environmental impact

Metabolic uncoupling technology was one of the methods widely used to on-site control the production of excess sludge in wastewater treatment processes. However, the uncoupler effects on soluble microbial products (SMP), microbial activity, and environment impact have few been reported. This study showed that sludge yield was reduced by 33.3% at 2,6-dichlorophenol (2,6-DCP) concentrations of 10 mg/L. The addition of 2,6-DCP also reduced the content of polysaccharide and protein in SMP, and the three-dimension excitation emission matrix (3D-EEM) suggested that the fluorescence intensities of humic acid-like, fulvic acid-like, and tryptophan protein-like substances decreased, proving that 2,6-DCP addition will weaken the interaction between microorganisms and the environmental matrix. Moreover, 2,6-DCP addition will change the microbial morphology and community of activated sludge. The active or respiring bacteria portion was lessened, and sludge flocs become dispersed, but it will not affect its settling performance. Surprisingly, 2,6-DCP has certain biodegradability and could be used as an environmentally friendly metabolic uncoupler under low-concentration dosing conditions. This study systematically evaluated the effect of 2,6-DCP on sludge production, SMP contents, microbial morphology, microbial community, demonstrating the environmental impact and application feasibility in the wastewater treatment systems.

Formation of microbial products by activated sludge in the presence of a metabolic uncoupler o-chlorophenol in long-term operated sequencing batch reactors

Metabolic uncouplers are widely used for reducing excess sludge in biological wastewater treatment systems. However, the formation of microbial products, such as extracellular polymeric substances, polyhydroxyalkanoate and soluble microbial products by activated sludge in the presence of metabolic uncouplers remains unrevealed. In this study, the impacts of a metabolic uncoupler o-chlorophenol (oCP) on the reduction of activated sludge yield and formation of microbial products in laboratory-scale sequencing batch reactors (SBRs) were evaluated for a long-term operation. The results show the average reduction of sludge yield in the four reactors was 17.40%, 25.80%, 33.02% and 39.50%, respectively, when dosing 5, 10, 15, and 20 mg/L oCP. The oCP addition slightly reduced the pollutant removal efficiency and decreased the formation of soluble microbial products in the SBRs, but stimulated the productions of extracellular polymeric substances and polyhydroxyalkanoate in activated sludge. Furthermore, the significant reduction of electronic transport system activity occurred after the oCP addition. Microbial community analysis of the activated sludge indicates dosing oCP resulted in a decrease of sludge richness and diversity in the SBRs. Hopefully, this study would provide useful information for reducing sludge yield in biological wastewater treatment systems and behaviors of activated sludge in the presence of uncouplers.