Reverse Osmosis Removes Chlorides from Contaminated Groundwater

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Located 39 miles northwest of Wichita, the city of Hutchinson, Kan., has a population of more than 40,000. The public water supply is derived from groundwater through 20 municipal wells, most of which have been installed and maintained by Layne Christensen Co.

The city discovered that carbon tetrachloride and other volatile organic compounds (VOCs) had contaminated one of its well sites. Additionally, high levels of inorganic chlorides (salts) were present.

VOCs are typically treated by air stripping; however, this strategy was complicated by the chlorides, which cannot be removed through air-stripping processes.

Professional Engineering Consultants was brought in to devise a treatment strategy. The facility treats water from the contaminated well, removing iron and manganese with manganese dioxide pressure filters, removing chlorides through reverse osmosis (RO) , then removing remaining CO2 and VOCs in a degasifier concealed in the clock tower. The resulting pure water is then blended with city water, resulting in a peak production capability of 10 million gal per day (mgd).

In June 2007, Layne Christensen Co. was awarded a contract from the general contractor, Walters Morgan Construction, to assist in the design and fabrication of an RO system with a peak capacity of 6 mgd. The contract included 5-micron cartridge filters, clean-in-place equipment and chemical feed equipment for the membranes.

The four RO skids were fabricated in Layne’s Lakeland, Fla., manufacturing facility, while chemical feed equipment was fabricated in Layne’s Kansas City, Kan., facility. There are four RO trains comprised of 24 x 12 -7M arrays, using Hydranautics ESPA 2 membranes. Each train is capable of producing 1.5 mgd of permeate from 2 mgd of influent. Combined, the RO trains provide the requisite 6 mgd of RO water from 8 mgd of feed. Layne was also contracted to provide startup and training in the operation of the RO system, the 5-micron cartridge pre-filters, clean-in-place equipment, the degasifier and the chemical feed equipment.

The RO system was completed in April 2009. The city of Hutchinson now has significantly cleaner and softer water and is recovering water that would otherwise be unusable.

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