Agenda - Parks and Recreation Commission - 04/10/2014

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C. WATER TREATMENT ALTERNATIVES 1. General For alternative comparison, water treatment facilities will be evaluated for both the groundwater and surface water sources. While groundwater sources currently have water quality which meets safety and regulatory standards, the high levels of iron and manganese will continue to provide a source of consumer concerns. In addition, the construction and maintenance of numerous small chemical treatment facilities at each well site requires a substantial capital investment and operations and management resources. Also, storage of chemicals at numerous sites presents a security and safety challenge regarding public safety. For this reason, a central water treatment facility will be considered. Figure 5.1 shows the proposed future system configuration and alternatives. 2. Ground Water Source Treatment Treatment of groundwater for iron, manganese and other contaminants is typically accomplished utilizing granular media filtration. Granular media filtration is effective in removing arsenic, radionuclides, iron and manganese. Arsenic and radionuclides are removed through a process known -as co -precipitation with iron and manganese. Iron and manganese is typically removed from water using an oxidation and filtration process. This process uses oxygen (through aeration of the water), or chemical oxidants such as chlorine or potassium permanganate, to oxidize and precipitate the iron and manganese. Once precipitated, the iron and manganese is easily captured and removed using granular media filters. Granular media filters can be either gravity type or pressure type filters. Pressure filtration is not generally utilized for radionuclide contaminant removal due to build up of radon gas in the system. 3. Surface Water Source Treatment Treatment for surface water sources can be accomplished utilizing either ultra filtration membrane processes, lime softening systems, or granular media filtration. Due to the decreasing cost of ultra filtration of processes, and the City of Ramsey, Minnesota — M21. 34343 Page 5-3 Water System Study Prepared by Bolton & Menk, Inc.