Simultaneous removal of nitrogen and phosphorus from wastewater by means of FeS-based autotrophic denitrification

The efficacy of iron(II) sulfide (FeS)-based autotrophic denitrification in simultaneous nitrogen and phosphorus removal from wastewater was studied with batch experiments. It was efficient at a wide pH range of 5-9, and temperature range of 10-40 °C. The concentrations of NH₄⁺-N, Mg²⁺ and HCO₃⁻ in the wastewater should be kept over 7.8, 0.24 and 30 mg L⁻¹ for efficient nitrate (NO₃⁻-N) reduction, respectively. The NO₃⁻-N removal rate increased from 0 to 82 mg L⁻¹ d⁻¹ and then leveled off when the NO₃⁻-N concentration increased from 0 to 415 mg L⁻¹ and then to 700 mg L⁻¹, respectively. The NO₃⁻-N removal rate quickly increased, leveled off, and then sharply decreased when the PO₄³⁻-P concentration increased from 0 to 0.1 mg L⁻¹, then to 114.0 mg L⁻¹, and further to 683.8 mg L⁻¹, respectively. The PO₄³⁻-P removal was over 98% when the PO₄³⁻-P concentration ranged 0-683.3 mg L⁻¹. During treatment of the secondary effluent of a local municipal wastewater treatment plant containing NO₃⁻-N of 14.9 mg L⁻¹ and total phosphorus (TP) of 3.9 mg L⁻¹, NO₃⁻-N was reduced to 1.1 mg L⁻¹ and TP was completely removed.