Jan 15, 2013 4 min read

CARMICHAELS – A study completed by the Carmichaels Municipal Authority recommends a number of operational adjustments to reduce the levels of trihalomethanes in its treated water.

The authority failed to comply in late 2010 and early 2011 with federal safe drinking water standards for THMs, which prolonged exposure has been linked to cancer and other health problems.

Since summer 2011, however, the authority has met the standard, testing well under federal limits for the compound, formed when chlorine, used by the authority as a disinfectant, combines with bromide and organic materials in raw water the authority draws from the river.

The authority has made several changes in its operations to address the problem and had asked its engineer, KLH Engineers, to look at the system and investigate a solution.

Jim Willard of KLH gave the authority a brief overview of the study Monday, first saying that though he didn’t want to minimize the authority’s problem, it isn’t serious in the context of what other water system have faced and it can be controlled.

The authority had three quarters of high THMs readings in 2010 and 2011 when bromide levels in the river were exceedingly high. Problems with the authority’s source water could not have been anticipated, but it did have an impact on the authority’s THM levels, he said.

“It was an unfortunate situation,” Willard said. “The good news is we’ve learned a lot about the plant and things that can be done, such as minor tweaks in the current treatment process.”

Willard spoke of some of the operational adjustments recommended by the study. One would involve minimizing chlorination at the pre-treatment and post-treatment stages while introducing chlorination to water as it leaves the storage tanks.

The longer chlorine remains in contact with organic matter in the water the greater the chance of THMs forming. Chlorinating at the plant results in a longer exposure time as water sits in the storage tanks and lines.

Adding chlorine to water leaving the tank will provide disinfectant in the lines but reduce the time chlorine is in contact with the water, he said.

The authority has been reducing chlorine retention time by flushing lines and by filling its tanks only half-full, but not filling the tanks also reduces the authority’s storage capacity that might be needed for fire protection, leaks or plant shutdowns, Willard said.

The study also recommends relocating the potassium permanganate feed to allow for longer retention, which the authority has already done; monitoring the water’s temperature and pH levels, which have an impact on THMs formation; and improving filter performance.

The study also recommends installing automatic flush devices on lines that hold water for longer periods of time and the addition of aeration and mixing systems at the storage tanks.

Authority manager Lloyd Richard said automatic flushing systems might not be necessary. The authority regularly has to test chlorine levels at the end of its lines and because the system is not large, it can easily flush lines manually at that time.

Willard also noted installing aeration and mixing systems at the tanks would be beneficial but also expensive, costing $250,000 to $500,000.

He urged authority members to read the entire report before deciding which recommendations the authority wishes to implement.

Board member Edgar Harris also suggested the authority use the report to develop operational procedures so plant operators can make adjustments when problems develop in the source water.

Willard agreed, noting operators can be more aware of possible problems and take action when water temperatures near 15 degrees Celsius. THMs start to form when water temperatures exceed that temperature, he said.

Willard also suggested a meeting be held to present the report to the public.

In other business, Richard reported the Environmental Protection Agency had contacted him about the authority participating in a study on THMs on the Monongahela and Allegheny rivers.

The study would provide free water testing for a year. However, Richard said the EPA representative indicated the authority would probably not be chosen because the authority’s problem is not among the worst on the rivers.

The board agreed to tell EPA it is interested in participating in the study.

The board reorganized, electing Dennis McCann, chairman; Harris, vice chairman; and John Beabout, secretary-treasurer.

The board will continue to meet at 4:30 p.m. the second Monday of the month; if the second Monday is a holiday the board will meet the following day. The board agreed to continue to retain Ben Goodwin as solicitor and KLH as engineers.