Removal mechanism of low-concentration Cr (VI) in a submerged membrane bioreactor activated sludge system.

Removal mechanism of low-concentration Cr (VI) (0.4 mg/L) was studied in a submerged membrane bioreactor (SMBR) activated sludge system. SMBR was operated with the synthetic wastewater containing 0.4 mg/L Cr (VI). Bio-removal and inactivation batch experiments were also carried out for studying the low-concentration Cr (VI) removal mechanism. SMBR activated sludge system recovered rapidly from the 0.4 mg/L Cr (VI) shock to achieve the excellent removal of chemical oxygen demand (COD) and NH4 (+)-N. Sulfuricurvum kujiense grew quickly in the bacterial community of activated sludge after Cr (VI) addition. Cr (VI) was mainly removed by the adsorption of extracellular polymeric substances, probably in the form as R2(SOH(+))2 (.)CrO4 (2-). Only few of Cr (VI) was transferred into Cr (III) under aerobic condition. All the results indicated that the sulfur was probably involved in 0.4 mg/L Cr (VI) removal process in SMBR.