Acclimatization of resorcinol results in microbial community dynamics and physicochemical characteristics of aerobic activated sludge

Abstract

Several studies have demonstrated that the biodegradation of resorcinol as a major pollutant in domestic coal gas wastewater can vary greatly with respect to its physicochemical properties and the structure of the bacterial flora induced during acclimation. The primary objective of this study is to investigate the degradation of resorcinol by aerobic activated sludge at different stages of domestication, changes in the toxicity of the sludge and the resultant dynamic changes in the structure of the dominant bacterial population. During the 40-day domestication process, we show that as the influent resorcinol concentration increased from 0 mg/L to 50 mg/L to 100 mg/L, the effluent resorcinol concentration and chemical oxygen demand concentration tended to increase then decrease. Organic matter in the sludge, ranging in size from 5 to 10 kDa, gradually accumulated to a concentration of 94.8 ± 1.8 mg/L (0 mg/L), 141.3 ± 2.1 mg/L (50 mg/L) and 192.4 ± 2.3 mg/L (100 mg/L), which constitutes the majority of its organic toxicity. Moreover, our study reveals that the total number of major degrading enzyme genes in the sludge samples during the domestication and stabilization period were 27322 (0 mg/L), 46076 (50 mg/L) and 32472 (100 mg/L). The results of the experiment indicate that Methylotenera, Methylophilus, and Azoarcus gradually took on the role of dominant resorcinol degraders. This contribution is fruitful in explaining the shift in sludge organic toxicity as the result of changes in the enzyme system of microflora in the sludge, which then resulted in an increase in the population of functional bacteria with enzymes that can degrade resorcinol, and in turn, stimulated the increase of the microbial enzyme system.