Flexible biological arsenite oxidation utilizing NO and O as alternative electron acceptors.

The feasibility of flexible microbial arsenite (As) oxidation coupled with the reduction of different electron acceptors was investigated. The results indicated the acclimated microorganisms could oxidize As with oxygen, nitrate and nitrite as the alternative electron acceptors. A series of batch tests were conducted to measure the kinetic parameters of As oxidation and to evaluate the effects of environmental conditions including pH and temperature on the activity of biological As oxidation dependent on different electron acceptors. Kinetic results showed that oxygen-dependent As oxidation had the highest oxidation rate (0.59 mg As g VSS min), followed by nitrate- (0.40 mg As g VSS min) and nitrite-dependent As oxidation (0.32 mg As g VSS min). The kinetic data of aerobic As oxidation were fitted well with the Monod kinetic model, while the Haldane substrate inhibition model was better applicable to describe the inhibition of anoxic As oxidation. Both aerobic and anoxic As oxidation performed the optimal activity at the near neutral pH. Besides, the optimal temperature for oxygen-, nitrate- and nitrite-dependent As oxidation was 30 ± 1 °C, 40 ± 1 °C and 20 ± 1 °C, respectively.