The water treatment plant that has processed drinking water from Middleton Pond for about 9,000 Danvers and Middleton residents has been working well since 1976, and were it not for tightening federal drinking water standards, the plant would keep on working with periodic improvements and upgrades of equipment and mechanicals.
But by 2015, new federal regulations that govern how many trihalomethanes (THMs,) are formed when chlorine is used to disinfect drinking water, are forcing the town to spend $21 million to redesign the treatment process “to keep us well in compliance,” said Town Engineer Rick Rodgers.
“It is all about the quality of the water. It is a constantly evolving process,” he said.
The construction project is expected to begin next month, after the town hires a building contractor. Rodgers was scheduled to open the bids from four competing companies on Thursday afternoon, but the bid opening was delayed to deal with a bidder's protest.
Once the work begins later this summer, it will take about two years to complete the expansion and renovations of the plant – allowing Danvers to come in a year ahead of the new federal regulations.
David Lane, director of public works, said the new plant is the result of five years of study and work with the state Department of Environmental Protection.
Since no town officials like spending $21 million, Lane, Rodgers and the plant management team have taken various steps in recent years to try to meet the new standards with less expensive upgrades. They wanted to avoid having to change the treatment process radically, which would require this significant investment.
Treatment Plant Today
Today, the millions of gallons of water that flow through the building every day get treated eight times with seven different chemicals. At the start of the process, the water is treated to remove the sediments that are in the pond water. As the water flows under the floor of the plant, it gets cleaner step by step. Machines stir the water to let the sediments settle out; others inject chemicals to separate out the organic materials and improve the quality of the water. There are also large holding tanks where the water slows down to a crawl and passes through sand and carbon filters – all to make the water cleaner.
But all those efforts, even with new equipment, could not pacify the feds on the amount of THMs in the water. The fear is that even miniscule amounts of THMs may cause cancer.
The new treatment process, which has been proven in other water treatment plants such as Andover's, will inject ozones in, purifying the water without creating THMs.
The process will require a new building on the banks of the pond to house the ozone treating equipment. The town is also building a third carbon and sand filter tank, and there will an extension on one end of the building to store the chemicals.
Much of the treatment equipment is being upgraded for higher efficiencies. More water will be recovered from the sludge that settles out of the pond water.The new equipment will be far more energy efficient.
The controls and data monitoring systems are being replaced with computers that take up a fraction of the space.
“You are not going to recognize the building,” said Jason McCarthy, plant manager.
The cost of the new state-of-the-art plant will be financed with a two percent loan from the state Revolving Funds and will be paid off over 20 years.
Rodgers expects that the new plant will last as long as the current one has, "probably 30 to 35 years," he said. That will be well after the veteran engineer is enjoying his retirement.