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

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 mu g.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 mu g.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. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

This study demonstrates that pyrrhotite can effectively remove arsenite and nitrate from groundwater, with the PAD technology providing a simple and cost-effective way for remediation. The PSLAD biofilter achieved good removal efficiency under a hydraulic retention time of 6 hours, showing the potential for practical application in addressing co-contaminated groundwater.