APPLICATION OF A NOVEL OXIDANT-COAGULANT FOR ARSENIC REMOVAL IN DRINKING WATER TREATMENT

摘要

The objectives of this study are to establish a technical and economical comparison of conventional existing and innovative treatments for Arsenic removal in drinking water. The work shows the interest of a new technology based on the use of ferrate for enhanced Arsenic removal. Ferrate(VI) ion (molecular formula FeO4 2-) is a very strong oxidant, which under acidic conditions, has a redox potential greater than that of ozone and of other main oxidants/disinfectants typically used for water treatment. Also, since the ferric ion generated in all oxidation reactions forms hydroxide oligomers, coagulation occurs eventually. Hence, ferrate(VI) represents a dual-function (oxidant and coagulant) chemical reagent that can be an effective alternative to current approaches for drinking water and wastewater treatment. Within a research and demonstration project partially funded by the European Community 5th Framework Program, a consortium of 9 European partners, is currently developing optimized methods for ferrate production on a large scale and studying several applications of ferrate in industrial, urban waste or drinking water treatment. Consequently, improvement of existing treatment processes and evaluation of new technologies such as Ferrate are needed to comply with the new regulation. Within this project, laboratory scale tests concerning the use of potassium ferrate for municipal water treatment have been carried out. Arsenic removal optimization was conducted on bench scale (Jar test, oxidation and filtration tests) performed on natural groundwater polluted by Arsenic and Manganese. The following treatments were compared and optimized: use of coagulant FeCl3 and KMnO4, use of new chemical (ferrate), use of combination of FeCl3 and ferrate. A classification of the different treatment processes according to their efficiency to remove Arsenic, Manganese and Iron has been obtained. The optimal operating conditions and chemical dosage have been determined, for each treatment process. Because of the new regulation on arsenic, drinking water suppliers need to assess specific processes to remove this pollutant. Several efficient treatments are available. Ferrate(VI) having a dual-function (oxidant and coagulant) can be an effective chemical and promising alternative to conventional approaches for Arsenic and Manganese removal in drinking water production.