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It is understood that the presence of iron and manganese in drinking water distribution systems 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 (USEPA) National Secondary Drinking Water Regulations suggest maximum concentrations of 0.3 mg/L and 0.05 mg/L for iron and manganese, respectively. During the last decade, microfiltration and ultrafiltration (MF/UF) membranes have become widely accepted as a viable alternative to conventional drinking water treatment technologies such as coagulation, settling and sand filtration. Over the past few years, continuous advances in cost and reliability, coupled with an increasing concern about pathogens such as Cryptosporidium have made MF/UF membranes the preferred alternative to conventional technology for new plants. 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. This technology has been proven through numerous pilot studies using the first three generations of ZeeWeed(R) 500 series immersed membrane systems, as well as the operation of a full-scale plant in New Brunswick, Canada that has been operating since 1996. The ZeeWeed(R) 500c module was recently developed to improve the air distribution within the membrane fiber bundle such that the thickness of the cake layer could be maintained or reduced during permeation. The improved design of the 500c module also allows for higher fluxes to be sustained. The ultrafiltration membrane used in the ZeeWeed(R) 500c system has the same membrane chemistry and absolute pore size as its predecessors and therefore also removes suspended solids, protozoa, bacteria and most viruses. The ZeeWeed(R) 500c membrane can also be coupled with a pre-oxidation step to achieve the removal of dissolved iron and manganese. Pilot studies have recently been completed to demonstrate the iron and manganese removal capabilities of the ZeeWeed(R) 500c immersed membrane system. This paper presents the application of immersed ultrafiltration membranes using oxidation for iron and manganese removal. Specifically, it presents pilot scale data for the ZeeWeed(R) 500c UF system, evaluating the effects of different operating parameters on iron and manganese removal from surface waters and groundwaters. Includes 4 references, table, figures.

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Edition: Vol. - No. Published: 01/01/2001 Number of Pages: 14File Size: 1 file , 490 KB