The disinfection and natural organic matter removal performance of electro-synthesized ferrate (VI)

Abstract

This study investigated the efficiency of electro-synthesized ferrate (VI) on the degradation of humic acid (HA) and removal of E. coll. for different samples. For providing complete inactivation of E. coli, > 1.5 mg L-1 ferrate (VI) concentration should be applied for only E. coli containing samples. For only HA containing sample, 60% DOC removal was achieved with 25 mg L-1 ferrate (VI). Ferrate (VI) was found to be more efficient at initial pH of 7 (pH(i)). For HA/E.coli containing samples, ferrate (VI) concentration should be increased to 260 mg L-1 for complete inactivation of E. coli. Specific UV absorbance (SUVA) values of raw samples showed that the samples mostly consist of high molecular weight and high hydrophobicity. After the treatment by ferrate (VI); while almost all hydrophobic part was removed, a small portion of hydrophilic part was also removed for only HA containing sample. However, for treated HA/E. coli containing sample, the aromatic removal took place but lower and higher molecular weights of NOM was still in the media in the presence of bacteria. The electro-synthesized ferrate (VI) lowered the trihalomethane formation potential. The residual total iron concentration was 1.14 mg L-1 at 1 min of process time and then remained stable. This means that ferrate (VI) was consumed as soon as it was applied and reduced to Fe-3/Fe-2.