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Pyrrhotite-sulfur autotrophic denitrification for deep and efficient nitrate and phosphate removal: Synergistic effects, secondary minerals and microbial community shifts

Li, Ruihua, Wei, Dongyang, Wang, Wei, Zhang, Yongwei
Bioresource technology 2020 v.308 pp. 123302
Thiobacillus, denitrification, ions, iron, microbial communities, minerals, nitrate nitrogen, nitrates, nitrogen, phosphates, phosphorus, protons, sulfate-reducing bacteria, sulfur, synergism, wastewater
Pyrrhotite-sulfur autotrophic denitrification (PSAD) system, using mixture of pyrrhotite and sulfur particle as electron donor, was studied through batch, column and pilot experiments. Treating synthetic secondary effluent at HRT 3 h, the PSAD system obtained the effluent with NO₃⁻-N 0.28 ± 0.14 mg·L⁻¹ and without PO₄³⁻-P to be detected. Thiobacillus was the most abundant autotrophic denitrification bacteria; autotrophic, heterotrophic and sulfate-reducing bacteria coexisted in the PSAD system; phosphate was mainly removed in forms of graftonite, dufrenite, ardealite. The H⁺ produced in the SAD could accelerate the PAD through promoting pyrrhotite dissolution, and iron ions produced in the PAD could accelerate the SAD through Fe³⁺/Fe²⁺ shuttle. Because of the synergistic effects between the pyrrhotite and sulfur, the PSAD system removed nitrate and phosphate deeply and efficiently. It is a promising way to meet the stringent nitrogen and phosphorus discharge standards and to recover phosphorus resources from wastewater.