High efficient bio-denitrification of nitrate contaminated water with low ammonium and sulfate production by a sulfur/pyrite-based bioreactor.

Sulfur-based autotrophic denitrification (SAD) and pyrite-based autotrophic denitrification (PAD) are important technologies that address nitrate pollution, but high sulfate production and low denitrification efficiency, respectively, limit their application in engineering. A bio-denitrification reactor with sulfur and pyrite as filler materials was studied to remove NO3--N from nitrate contaminated water. At an influent NO3--N concentration of 50 mg/L, NO3--N removal efficiency of the sulfur/pyrite-based bioreactor was 99.2%, producing less NH4+-N and SO42- than the sulfur-based bioreactor, even after long-term operation. Denitrification performance was significantly related to environmental variable, especially dissolved oxygen. Proteobacteria and Epsilonbacteraeota were the predominant phyla in the sulfur/pyrite-based bioreactor, and fewer dissimilatory nitrate reductions to ammonia process-related bacteria were enriched compared to those in the sulfur-based bioreactor. Sulfur-pyrite bio-denitrification provides an efficient alternative method for treatment of nitrate contaminated water.