Saxman Completes New Surface Water Treatment Facility
April 17, 2012
A community of approximately 436 people located about 2 miles south of Ketchikan on Revillagigedo Island, Saxman's water supply consists of a small dam located on a creek near the community. The watershed that serves the creek is characterized by heavily forested steep mountainous terrain. Water quality in the creek varies rapidly with wide ranges in levels of organic contaminants and turbidity.
The Alaska Native Tribal Health Consortium (ANTHC) assisted the community of Saxman with the planning, design and construction of the new water treatment facility that will allow the community to meet regulatory drinking water requirements including those associated with troublesome Disinfection byproducts (DBPs) which are a common water quality challenge for many small communities in Alaska.
The Alaska Native Tribal Health Consortium (ANTHC) Division of Environmental Health and Engineering (DEHE) works with water systems across Alaska to assist communities with solving water treatment challenges, including those associated with controlling DBP formation.
The community of Saxman has been challenged in recent years with excessive levels of DBPs, such as haloacetic acids, in the water distribution system. The Magnetic Ion Exchange (MIEX®) process was selected as a means to remove additional dissolved organic carbon (DOC) from their raw water source prior to coagulation, filtration and disinfection.
Pilot test results of the new system indicates that the additional dissolved organic carbon (DOC) removal provided by the MIEX® System enables the Saxman Water Treatment Plant to comply with United States Environmental Protection Agency (US EPA) regulations and will reduce the water treatment plant’s consumption of coagulant and chlorine chemicals.
The new process works by the Magnetic Ion Exchange (MIEX®) resin absorbing organic carbon onto the surface of the resin which is regenerated typically with sodium chloride. The magnetically charged resin also removes lower molecular weight organics from the water, which are the most reactive with chlorine and are difficult to remove with coagulation alone. Coagulation compliments the Magnetic Ion Exchange (MIEX®) process by removing the higher molecular-weight organic contaminants that are not adsorbed onto the MIEX resin.
Filtration of the water is then accomplished through pressure filters using a cationic polymer/metal salt blend as the coagulant. The coagulant feed rate is controlled automatically in a closed loop control system using a streaming current detector. The plant is also equipped with an automated shut-down feature that is controlled by online turbidimeters.
Construction costs of the new Saxman Water Treatment system were reduced through the use of Schedule 10 stainless steel pipe that were prefabricated into large lightweight sections prior to shipment to the site. This approach minimized installation time and the costly field labor associated with erection and painting of the piping system.
Long-term maintenance costs for the new Saxman facility were reduced through the use of stainless steel materials to address corrosive water and a high humidity environment.
Energy efficiency of the facility enhanced through the use of pressure filters, heat pumps and low energy lighting.
The community is invited to visit the new Saxman Water Treatment Plant. A Grand Opening is planned for June 2012, with the date to be announced.
Edited by Mary Kauffman, SitNews
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