Effects of thiocyanate on granule-based anammox process and implications for regulation

The feasibility of using anaerobic ammonium oxidation (anammox) process to treat industrial wastewater containing thiocyanate (SCN-) was examined in this study. Anammox activity decreased with increasing thiocyanate concentration and pre-exposure time in batch tests. A typical noncompetitive model was used to fit the data for thiocyanate inhibition, and the 50% inhibition concentration (IC50) of thiocyanate on anammox was 620.4 mg L-1 at 200 mg L-1 total nitrogen level. The influent thiocyanate concentration of test reactor (R-1) in phase II gradually increased from 10 to 120 mg L-1, and the average nitrogen removal efficiency (NRE) of R-1 was maintained at 83.0 +/- 7.82%. This robustness was attributed to the self adaptation ability of anammox biomass through long-term acclimatization. The NRE was decreased to 57.1% under 130 mg L-1 thiocyanate within two days. However, the NRE of control reactor (R-0) in absence of thiocyanate was 91.23 +/- 4.11% in this phase. Under thiocyanate stress, the specific anammox activity, settling velocity and heme c content of the granules significantly decreased, and the extracellular polymeric substances content slightly increased. The short-and long-term performance inhibition could be reversed in the presence of 10 mg L-1 Fe(III). (C) 2016 Elsevier B.V. All rights reserved.