Flexible biological arsenite oxidation utilizing NOx and O2 as alternative electron acceptors

- Acclimatized AsOB can oxidize AsIII with O2, NO3 and NO2 as electron acceptors.
- Kinetic parameters of AsIII oxidation using various electron acceptors were tested.
- The optimum pH and temperature for AsIII oxidation were examined.

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