Effect of chromium on granule-based anammox processes

In this study, the feasibility of application of anaerobic ammonium oxidation (anammox) to teat wastewater containing chromium was assessed. Anammox granule activity decreased with increasing Cr(VI) concentration and pre-exposure time in batch tests, and the 50% inhibition concentration of Cr(VI) on anammox biomass was 296.5 mg L-1. Approximately 93.9% chromium was absorbed by loosely bound-extracellular polymeric substances and tightly bound-extracellular polymeric substances when less than 60 mg L-1 Cr(VI) was added. During long-term operation in up-flow anaerobic sludge blanket reactor, significant inhibitory effects anammox performance were observed for Cr(VI) concentrations up to 2 mg L-1. The nitrogen removal rate (NRR) rapidly decreased to 1.49 +/- 0.89 kg Nm(-3) d(-1), whereas the NRR was 11.37 +/- 1.30 kg Nm(-3) d(-1) in a control reactor. Compared with initial levels, specific anammox granule activity was 22%. The tolerance of the anammox process to Cr(VI) can be enhanced after a long-term adaptive phase.