Fallon eyed for arsenic removal success
The science the city of Fallon will use to reduce by tenfold the 100 parts per billion of naturally occurring arsenic found in the municipal water supply is novel, but not untested.
A smaller version of the city’s $17 million treatment plant has already proven to work during pilot testing. The process is called enhanced coagulation and microfiltration, and it doesn’t take a chemist to understand how it will remove arsenic.
Raw water from city and Navy wells is piped into the facility off Harrigan Road. The pH is adjusted from 9.2 to 6.5, and iron in a chemical solution is continuously fed into the water stream, which causes a reaction and forms what are called “flocks.” They bond with the arsenic, creating a bigger particle, which can then be screened out by filters.
The filters are backwashed and pressed to reclaim treated water. As water exits the plant into the distribution system, lime is added to readjust the pH level.
What’s left is an arsenic sludge that the U.S. Environmental Protection Agency considers nonhazardous and acceptable for disposal at the city’s landfill.
The key to treating Fallon’s water, experts say, is the pH adjustment and introduction of iron. Evidence of the ability of iron to bond with arsenic and allow it to be filtered out was observed at a water treatment plant in Illinois. In 1998, according to EPA reports, efforts there to clean up municipal water of iron and manganese also removed arsenic incidentally in the process.
When the city starts treatment operations this week, it will treat about 4.5 million gallons a day, depending on seasonal usage. The facility was designed to handle new hookups for the next 20 years and can be expanded to a capacity of 9.6 million gallons a day.
Tim Runnells, an employee of consultant Shepherd Miller and the project manager for Fallon’s water treatment plant, said he knows of no other treatment plant on the scale of Fallon’s designed exclusively to remove arsenic.
“There aren’t any that have been built that I’m aware of,” he said.
Other communities facing a compliance date of January 2006 to get their municipal water systems under 10 ppb will seek technology that is sure to develop at hyperspeed. For its part, Fallon had to move quickly on a treatment process when it received a notice in 2000 of violation and administrative order to treat the water from the EPA.
The city ruled out some arsenic treatment technologies early on because they either cost too much to operate or waste water. Reverse osmosis, while easily adaptable to small scale water treatment, loses a lot of water in the process. Fallon’s treatment plant will lose less than 5 percent of water that comes into the plant. That was a big consideration for a city in a desert that receives less than 6 inches of annual precipitation.
The cost for Fallon, Runnells said, will be the chemicals and materials used to draw out the arsenic, along with the manpower to operate the facility. Right now, the expenses are pegged at about $1.7 million annually, a big bill to be picked up by 2,500 connections. City leaders continue to seek funding to mitigate the cost.
“Have we seen a magic technology that’s going to do it for nothing and not lose lots of water? No, we have not seen that,” Runnells said.
Contact Steve Lyon at firstname.lastname@example.org