inhibitory effect of fluoride on anaerobic ammonium oxidation (anammox)

BACKGROUND: Anaerobic ammonium oxidation (anammox) is a promising process for nitrogen removal, but it cannot always be used successfully in the presence of inorganic matter. The feasibility of using the anammox process for treating wastewater that contains fluoride was examined in this study. The short‐term inhibitory effect was tested at various fluoride concentrations and exposure times, and diverse pre‐exposure strategies were performed in special serum bottles. Subsequently, the long‐term effect of fluoride stress was continuously monitored and evaluated in an upflow anaerobic sludge blanket (UASB) reactor. RESULTS: The 50% inhibitory concentration (IC₅₀) of fluoride for anammox biomass was calculated to be 767 mg L⁻¹ in batch tests with an initial total nitrogen (TN) level of 200 mg L⁻¹. A remarkable inhibitory effect of fluoride emerged when the substrate was supplied at >420 mg L⁻¹ TN. The diameter and settling velocity of the granules significantly increased with the addition of 250 mg L⁻¹ fluoride. CONCLUSION: The performance of the anammox system and the granule properties were abnormal at a fluoride concentration of 400 mg L⁻¹. The anammox UASB reactor was able to treat wastewater containing up to 350 mg L⁻¹ fluoride after 183 days. © 2014 Society of Chemical Industry