Simultaneous arsenite and nitrate removal from simulated groundwater based on pyrrhotite autotrophic denitrification

• Published in: Water research (Oxford) 2021-02, Vol.189, p.116662, Article 116662
• Main Authors: Li, Ruihua, Guan, Mengsha, Wang, Wei
• Format: Article
• Language: English
• Subjects: Arsenite; Arsenites; Autotrophic denitrification; Autotrophic Processes; Bioreactors; Denitrification; Groundwater; Nitrate; Nitrates - analysis; Pyrrhotite; Thiobacillus
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2020.116662

lPAD can effectively remove As(III), NO3− and PO43− simultaneously.lSulfur autotrophic denitrifiers are not inhibited by As(III) with concentration up to 70 mg·L−1.lThiobacillus is the most abundant bacterium in the PSLAD biofilter.lPyrrhotite and sulfur are electron donor to reduce NO3− to N2 in the PSLAD biofilter.lAs and PO43− were mainly removed through precipitates FeAsO4 and FePO4, respectively. In this study, pyrrhotite is applied to remove arsenite (As(III)) and NO3− from groundwater simultaneously. Batch experiments find that sulfur autotrophic denitrifiers are not inhibited by As(III) with concentration up to 70 mg·L−1, and pyrrhotite autotrophic denitrification (PAD) can effectively remove As(III), NO3− and PO43− simultaneously. Treating water with As(III) 874.50±32.76 µg·L−1, NO3−-N 30 mg·L−1, and PO43−-P 0.5 mg·L−1, the pyrrhotite-sulfur-limestone autotrophic denitrification (PSLAD) biofilter can achieve effluent with total Arsenic (As) 7.84±7.29 µg·L−1, NO3−-N 3.78±1.14 mg·L−1, and PO43−-P below detection limit at hydraulic retention time 6 h. In the PSLAD biofilter, Thiobacillus is the most abundant bacterium, and it uses pyrrhotite and sulfur as electron donor to reduce NO3−, and basically Fe2+ and As(III) are oxidized to Fe3+ and arsenate, respectively. As and PO43− were mainly removed through precipitates FeAsO4 and FePO4, respectively. Technology based on the PAD is a simple, cost-effective and efficient way for remediation of As(III) and NO3− co-contaminated groundwater, and avoiding contaminants transference between groundwater and surface water. [Display omitted]