In general, the ZVI-facilitated COD removal process was
achieved mainly through the following two ways: (1) ZVI acts as
a slow-release electron donor to promote methanogenesis, which
improves the biodegradation of organics; (2) ZVI can directly
reduce contaminant at its surface, additionally the corrosioninduced
iron ions may assist in the removal of suspended organic
matter through the flocculation, adsorption, and co-precipitation
reactions. The two aspects that were both affected by the rZVI/VSS
determined the COD removal performance of the combined system
together