Response of dissimilatory perchlorate reducing granular sludge (DPR-GS) system to high-strength perchlorate and starvation stress in UASB reactor: Performance, kinetics and recovery mechanism

Abstract

Under high-strength perchlorate concentration ranging from 300 to 1300 mg/L, the dissimilatory perchlorate reducing granular sludge (DPR-GS) was successfully cultivated in an up-flow anaerobic sludge blanket (UASB) reactor to investigate performance and starvation recovery for treating perchlorate wastewater. The mature DPR-GS had excellent perchlorate removal efficiency (98.47%) at 1200 mg/L. Microbial community analysis suggested that the dominant genera in mature DPR-GS were Sulfurospirillum and Acinetobacter. The DPR-GS system conformed well to the modified Stover-Kincannon model with the maximum substrate utilization (Umax) of 90.01 kg/(m3·d) and the saturation value constant (KB) of 83.93 kg/(m3·d). Additionally, the starvation recovery of DPR-GS system was first investigated. The perchlorate removal efficiency recovered to 91.39% after 8 days under the 30-day starvation stress, and the microbial activity also recovered to normal condition. The three-dimensional excitation-emission matrix (3D-EEM) proved that the tryptophan-like component in extracellular polymeric substance (EPS) increased during the starvation period, which was associated with immune functions and played an important role in maintaining the microbial activity. Meanwhile, the secretion of humic acid-like component in EPS promoted electron transfer efficiency, thus improving microbial metabolic activity during the recovery period. Further analysis by the parallel factor (PARAFAC) of 3D-EEM confirmed that the decrease of immune substances and the increase of metabolic products in EPS during the starvation recovery period, which enhanced the recovery of microbial activity and the improvement of perchlorate removal performance. This study revealed the response of the DPR-GS system to high-strength perchlorate and starvation stress, thus provided a further basis of perchlorate tolerance and starvation recovery for the application of DPR-GS system to remove high-strength concentrated perchlorate from contaminated water.