Perchlorate reduction by anaerobic granular sludge under different operation strategies: Performance, extracellular polymeric substances and microbial community

Abstract Anaerobic granular sludge (AnGS) has been successfully applied for biological wastewater treatment, but less research has been performed on bioreduction of high-strength perchlorate (ClO4−). The tolerance of AnGS to perchlorate loading rate (PLR) was first investigated under different PLR increase strategies (RS, slow-increasing PLR (SI-PLR); RR, rapid-increasing PLR (RI-PLR)). Under SI-PLR and RI-PLR strategy, the AnGS could achieve the maximum PLR of 9.90 and 10.67 g·L−1·d−1, respectively. When exceeding the maximum PLR, ClO4− removal efficiency decreased due to the disintegration and aggregation of granules. The extracellular polymeric substances (EPS) secretion in RR was 1.9 times higher than that in RS. Overproduction of EPS could allow AnGS to tolerate higher loading rate. The microbial communities and principal component analysis indicated that Hydrogenophaga, Azospira, Cloacibacterium and UKL13-1 were EPS-secreting bacteria. Mechanism for the disintegration and aggregation of granules was proposed.