Exploring the effectiveness of in-situ sodium ferrate (VI) during the bench-scale of manganese removal from raw water collected from a South African WTP

Abstract

Manganese (Mn) is an essential element for human body and several enzymes rely on its redox properties. Its elevated concentrations in water can be toxic to humans, stain porcelains and can generate an undesirable taste in beverages. Several methods including adsorption, biologically active filtration oxidation and precipitation have been used to reduce it from water. Unfortunately, most of these methods have disadvantages of generating harmful by-products. Ferrate (VI) has been considered as a supplant to common oxidants during the treatment of drinking water. It has main advantages such as production of ferric ion, high oxidation potential, which may support coagulation, and the lack of significant halogenated by-product generation. However, this study aimed at exploring the effectiveness of in-situ liquid sodium ferrate (Na2FeO4) during the removal of Mn from raw water collected from Cullinan water treatment plant (CWTP) at the bench-scale. Na2FeO4 was produced using a wet oxidation method. The treatment of raw water collected from CWTP presented the removal percentage of Mn ranging between 82.70 and 99.20%. The pH of the drinking water sample raised from 7.25 to 10.97 after treatment. The treatability index (TI) was also studied. Only the TI of pH value was less than one. The TI results indicated high value of EC and authors would like to replace sodium by calcium in the ferrate product to reduce EC of the treated water and recommend the application of FeO42- ions for the treatment of raw water in a full-scale as it showed to be a promising a green oxidant.