LAUSR

Abstract This study explored hexavalent chromium (Cr (VI)) adsorption onto active aerobic granular sludge (AGS) under neutral condition and then focused on Cr (VI) desorption from the Cr-loaded AGS. The changes of AGS bioactivity and stability were also analyzed with respect to cations release and extracellular polymeric substances (EPS). Among the 6 test desorbents, sodium carbonate (Na2CO3) showed the best performance for Cr (VI) desorption from Cr-loaded AGS, reflecting a better fit to the pseudo-second-order kinetic model (R2 = 0.985–0.995). Granular specific oxygen uptake rate (SOUR) was detected to decrease from the initial 22.38 to 5.55 mg-O2/g-VSS·h after 60 min desorption by 1 M Na2CO3, with integrity coefficient increased from 5.52% to 25.63%. Release of Ca2+, Mg2+ and K+ was mainly from EPS, especially the tightly bound EPS during the desorption process. Moreover, proteins rather than polysaccharides were found to be more sensitive to the increasing Na2CO3 concentration during the desorption process.