BY ETHAN FORMAN
---- — MIDDLETON — The beeping front end loaders and busy construction crews at the Danvers water treatment plant on Lake Street are out of sight to most Danvers and Middleton residents.
But the importance of the project along the shore of Middleton Pond will be evident every time customers in both towns turn on their taps.
A more than $20 million project to retrofit the Vernon C. Russell Water Treatment Plant is now 80 to 90 percent complete, and it’s expected to wrap up this fall, said Richard Rodgers, the town engineer for Danvers. Danvers supplies both towns with water, mostly drawn from Middleton Pond.
The upgrade is expected to give the plant another 20 to 30 years of life, and allow it to meet stringent new regulations in the federal Safe Drinking Water Act by 2015.
In the meantime, the work has caused discolored water in some areas, but new pumps should clear up the problem. The water is safe to drink, officials said, and residents can run cold water to flush out their pipes.
The soup-to-nuts renovation and addition involves everything from a new walkway at the front entrance to construction of new filtration, ozone treatment and sludge dewatering buildings. The original plant went online in 1976.
The plant also changed the way it disinfects water, switching from chlorine to monochloramines. The latter chemical lasts longer and causes fewer harmful byproducts.
The new filtration building at the back of the plant added massive sand and carbon filters, each the size of a large, rectangular swimming pool, to the two filters already in place. This work increased the plant’s capacity to pump out clean water at a higher rate.
The upgrade also includes a new sludge handling facility to capture water from leftover sediments. Because the plant is not connected to sewers, it must store sludge in lagoons at the back of the property before it is trucked to the South Essex Sewerage District for disposal. Capturing water from the sludge will mean fewer truck trips and less waste.
One of the most significant upgrades is an ozone treatment plant built at the front of the building. It has yet to be brought online.
Plant manager Jason McCarthy said the upgrades are still a work in progress.
“What remains now are the details,” McCarthy said. “We have got one major piece left (the ozone plant) that needs to get started up. Everything else has been at least started up to the point where it’s ready to get handed off to us and we will be using it regularly.”
There are also upgrades to a records room, a break room, bathrooms and storage rooms. New fire suppression and security systems are being installed. Water officials are gingerly switching the functions of the old control room console to a desktop computer, which will be used to run the plant’s operations.
Open houses are being planned in the fall, Rodgers said.
Waterline Industries of Seabrook, N.H., is the general contractor, and the architectural and engineering firm Kleinfelder designed the plant upgrades.
The project is being paid for through the water rate, with the average family shelling out $40 to $50 a year, said David Lane, Danvers public works director.
Staff writer Ethan Forman can be reached at 978-338-2673, by email at firstname.lastname@example.org or on Twitter at @DanverSalemNews.
HOW WATER IS TREATED
Because Middleton Pond is the primary water source for Danvers and Middleton, the water that comes from it is loaded with organic material. Treating the water is a balancing act of chemical and mechanical processes.
A pump house along Middleton Pond sends the pond water through underground pipes into the treatment plant, said plant manager Jason McCarthy. Once inside, the water enters a flash mixer where it gets an initial dose of chemicals to coagulate and precipitate out solids. The water also gets a dose of disinfectant.
The flow of the water is slowed, allowing heavy solids to settle out.
The water flowing above the solids, known as supernatant, is pumped through sand and carbon filters the size of large swimming pools. The sand removes particles and the carbon absorbs organic materials.
The water from the filters then passes into a clear well to be disinfected before being sent out into the water system.
The upgrade to the water treatment plant added a new method of disinfectant using ozone. When this form of treatment is up and running, the pond water will first be treated with ozone, which removes organic materials and kills parasites. The ozone will be generated from 6,000 gallons of liquid oxygen stored at the plant.
“It’s a very aggressive oxidizer and it will remove many of the organics before it ever gets into the plant,” McCarthy said. The ozone also aids in the precipitation and sedimentation process, and helps eliminate harmful byproducts from other disinfectants.
The water will get “a second hit of ozone” before it is run through the carbon and sand filters, McCarthy said. After the water is treated with ozone, it must be sent through ozone gas destruction units to make sure none of it gets into the finished water.
During the treatment process, leftover sediments wind up in large basins under the plant. A new sludge dewatering building is designed to dry out the sludge, reclaiming 2 million gallons of water a year.