Biological arsenite oxidation with nitrate as sole electron acceptor

The potential of anoxic biological arsenite oxidation with nitrate as the sole electron acceptor was tested by using the acclimatized activated sludge which was chronically exposed under arsenite and nitrate coexisted aquatic environment. The activated sludge cultivated in a sequencing batch reactor was fed with arsenite and nitrate as the main substrates over six months. A series of batch experiments were conducted with acclimated sludge. Results showed that no obvious inhibition was observed in the anoxic arsenite oxidation linked to nitrate and nitrite reduction at the concentration of arsenite up to 35 mg As^III L^-1. Moreover, it was found that nitrite was accumulated over the reaction probably due to limited availability of arsenite. The kinetic study further suggested that the maximum specific arsenite oxidation rates (q_{obs, max}) with nitrate and nitrite as the electron acceptors were found to be 0.55 ± 0.10 mg As^III g^-1VSS min^-1 and 0.40 ± 0.04 mg As^III g^-1VSS min^-1, respectively.