AWWA MTC57618

The presence of iron and manganese in drinking water distribution systems is a concern as it reduces the aesthetic quality of the water. When dissolved iron and manganese are oxidized, they form insoluble compounds that precipitate and cause yellowish to reddish-brown to black staining, depending on the relative abundance of each metal. In order to improve the aesthetic quality of drinking water, the US Environmental Protection Agency National Secondary Drinking Water Regulations suggest maximum concentrations of 0.30 mg/L and 0.05 mg/L for iron and manganese, respectively. The ZeeWeed(R) Ultrafiltration Membrane system can remove particles that are greater than 0.1 microns in size, including iron and manganese precipitates. For the removal of dissolved iron and manganese, an oxidation step is added prior to the membrane, which converts the dissolved species into their insoluble forms. Oxidation may be achieved by aeration or by the addition of oxidizing chemicals such as chlorine, chlorine dioxide or potassium permanganate. For water sources requiring both removal of dissolved organics and dissolved iron and manganese, ZENON has developed a unique process in which the ZeeWeed(R) Ultrafiltration Membrane system can be coupled with a single step coagulation-oxidization process. This paper discusses critical process issues required to prevent membrane fouling and to achieve the treated water quality objectives with respect to organics and iron and manganese removal while utilizing the simultaneous step coagulation-oxidation process. This paper also presents the results from numerous pilot studies conducted to demonstrate the capabilities of ZeeWeed(R) 500 immersed membrane system to combine both of these pretreatment steps. A detailed discussion evaluates the effects of different operating parameters on TOC, color, iron and manganese removal from surface waters and groundwaters. Includes 4 references, tables, figures.