Analysis of ZVI corrosion products and their functions in the combined ZVI and anaerobic sludge system

The zero-valent iron (ZVI) corrosion products and their functions were investigated in the combined ZVI and anaerobic sludge system. Results showed that ZVI corrosion occurred, and the reductive transformation and dechlorination of p-chloronitrobenzene (p-ClNB) by the anaerobic sludge were enhanced. In the combined systems with different types of ZVIs and mass ratios of anaerobic sludge to ZVI, a considerable amount of suspended iron compounds was produced and coated onto the microbial cells. However, the microbial cellular structure was damaged, and the p-ClNB reductive transformation was affected adversely after the long-term presence of nanoscale ZVI (NZVI) or reduced ZVI (RZVI) with a high concentration of 5 g L^‑1. The oxidized products of FeOOH and Fe₃O₄ were found on the surface of ZVI, which are speculated to act as electron mediators and consequently facilitate the utilization of electron donors by the anaerobic microbes.