Exploring the role of pyrite in promoting as attenuation in constructed wetland

It is a great challenge for constructed wetlands (CWs) to treat heavy metal wastewater. In this study, we used pyrite as a substrate filler to strengthen the vertical flow CW to remove arsenic (As) wastewater and achieved excellent performances. Results show that pyrite addition enhanced total arsenic (TAs) removal, reaching 81.82 % efficiency which surpassed both control (74.19 %) and magnetite (61.03 %) group by 8 % and 21 %. Notably, mass balance analysis indicated that pyrite substrate captured 77 % of TAs, with a satisfactory 5 % closure. Pyrite can undergo oxidation to generate Fe3+ and SO42−, which subsequently reacts with As(III) to form compounds resembling tooeleite. Moreover, pyrite facilitates the uptake of TAs in plant roots and enhances electron transfer activity by promoting iron and sulfur cycling. The reduction of As(V) mediated by microorganisms was enhanced in the presence of pyrite, owing to the continuous precipitation of As(III) facilitated by Fe and S present in the pyrite system. Micrococcaceae and Opitutaceae were identified as the predominant microbial groups involved in As removal. Furthermore, metagenomic binning revealed that Micrococcaceae exhibited mechanisms related to microbial resistance against As, while Opitutaceae mitigated metabolic damage caused by As(V). In conclusion, the abiotic and biotic effects of pyrite provided insights to As retention in VFCWs. © 2024 Elsevier B.V.