Iron Oxide Helps Reduce Arsenic Levels for OK Water Plant
The City of Norman, Oklahoma, plans to install a novel arsenic treatment system across 11 wells that were shutdown when the U.S. Environmental Protection Agency lowered the maximum contaminant level for arsenic in drinking water to 10 µg/L (.010 parts per million or 10 parts per billion) in 2006.
The shutdown cut well production in Norman from nearly 5 million gallons per day to just over 2 million gallons per day, resulting in the city buying more expensive water from Oklahoma City. The water treatment system will bring the wells — one-third of the city’s total well capacity — back on line.
Initially, the town ran a one-year demonstration project piloting an arsenic treatment system at one of its wells from Urban Contractors, Garver Engineers and Severn Trent Services.
The system uses iron-oxide-based media, Bayoxide E33, with Severn’s SORB 33 arsenic removal system. Adsorption with iron-oxide based media doesn’t need chemical regeneration or flocculation, making the arsenic removal process much easier and more reliable, according to Severn. In addition, the spent media is classified as non-hazardous so it can be disposed of in solid waste landfills, and the media does not need to be replaced for six months to two years.
The city installed three 5-ft SORB adsorption vessels at one of the Norman wells that had arsenic levels between 40 µg/L and 70 µg/L. In addition, the groundwater contained high levels of iron (500 ppb), manganese (50 ppb) and vanadium (160 µg/L).
The company’s novel system design called “sequencing” was used in Norman in which three pressure vessels with Bayoxide media were used in both parallel and series flow configurations. This allowed for the highest capacity of arsenic adsorption to occur during one media cycle, treating up to 40 percent more water before being replaced, according to Severn.
Full-scale testing began in June 2008. Testing was successful, meeting the city’s agreed upon reduction of arsenic to 8 µg/L or less.
Other cities including Palm Beach, Fla.; Yerinton, Nev., and Virden, Manitoba, are also making water treatment upgrades.
As an example, the city of Palm Beach wants to replace the city’s outdated water treatment system with a $63 million filtration system that will deliver higher quality water, reports Palm Beach Post.
The city of Yerington announced that it is close to securing final funding for its arsenic treatment plant project, reports The Reno-Gazette Journal. The city received a $4.5 million civil program financing grant last year but it didn’t cover all the costs mandated by the new federal arsenic drinking water standards.
Meanwhile, Virden’s $1.8 million upgrade to its water treatment plant is nearly complete, which is expected to resolve the city’s concerns with high arsenic levels, reports WaterWorld. Arsenic levels in the city have held at 0.04 mg/l for the past several years, compared to the provincial standard of 0.01 mg/l, set in 2006.
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