Insights into Anammox activity inhibition under trivalent and hexavalent chromium stresses

Abstract

The implementation of Anammox process in wastewater has been a growing concern, but chromium toxicity, created by the coexistence of chromium and ammonium, is a challenge, In this study, the acute toxicity of two typical chromium ions (i.e., Cr(III) and Cr(VI)) on Anammox process as well as the kinetics under Cr(VI) stress and the fate of Cr(VI) were assessed. The results showed that Cr(III) had little influence on Anammox activity since the inhibition percentages were only 1.47% at 32 mg L−1. However, Cr(VI) imposed a more pronounced inhibition with a half inhibition concentration of 10.91 mg L-1. Kinetics results indicated that Cr(VI) exerted a non-competitive inhibition on both of ammonium oxidation and nitrite conversion. Moreover, the fate of Cr(VI) was determined by the distribution and species variation of Cr(VI). The results demonstrated that Cr(VI) immigrated into sludge and then reduced to Cr(III). Cr(III) accounted for 92.5% of the total chromium in the sludge. Our results provided deeper insights into chromium acute toxicity on Anammox activity, which will aid in implementing Anammox process into wastewater treatment.