The exploration of potassium ferrate(Ⅵ) as a disinfectant/coagulant in water and wastewater treatment

摘要

This paper aims to explore potassium ferrate(Ⅵ) (K_2FeO_4) as an alternative water treatment chemical for both drinking water and wastewater treatment. The performance of potassium ferrate(Ⅵ) was evaluated in comparison with that of sodium hypochlorite (NaOCl) and that of NaOCl plus ferric sulphate (FS) or alum (AS). The dosages of fer-rate(Ⅵ), NaOCl and FS/AS and sample pH values were varied in order to investigate the effects of these factors on the treatment performance. The study demonstrates that in drinking water treatment, ferrate(Ⅵ) can remove 10-20% more UV_(254)-abs and DOC than FS for the same dose compared for natural pH range (6 and 8). The THMFP was reduced to less than 100 μg l~(-1) by ferrate(Ⅵ) at a low dose. In addition to this, ferrate(Ⅵ) can achieve the disinfection targets ( > 6 log_(10) inactivation of Escherichia coliform (E. coli)) at a very low dose (6 mg l~(-1) as Fe) and over wide working pH in comparison with chlorination (10 mg l~(-1) as Cl_2) plus coagulation (FS, 4 mg l~(-1) as Fe). In wastewater treatment, ferrate(Ⅵ) can reduce 30% more COD, and kill 3 log_(10) more bacteria compared to AS and FS at a similar or even smaller dose. Also, potassium ferrate(Ⅵ) can produce less sludge volume and remove more pollutants, which could make sludge treatment easier.