MANCHESTER — Brace yourselves, citizens of Manchester. The town is about to pop the lid on a big stink.
As part of an upgrade to the sewer plant, two 500,000-gallon "digester" tanks installed in 1954 must be cleaned out and demolished. The work is set to begin on or around July 15 at the plant on the western side of town.
"The cleaning of this old system is going to result in very unpleasant odors depending upon proximity and wind direction," General Manager Scott Shanley said. "We expect the first few weeks of work, when the largest amounts of highly concentrated organic material are being removed, will be the most hostile to the human senses. We expect steady improvement until completion of this phase in late September."
The digester tanks employ microorganisms that break down and reduce waste. Over many years, the containers have become like huge grease traps, with an accumulation of inorganic matter such as flushed toys and other plastic material mixed with the slurry and sludge of human waste.
"When they get to the bottom, it will be almost like asphalt," Wastewater Superintendent Mike Emond Jr. said.
Crews will open access hatches at the tops of the tanks and then pump the material into a portable centrifuge to remove water. The sludge then will be trucked to the nearby landfill, a job to be completed within about three months, Emond said.
The two-year, $43 million plant upgrade is driven by government clean water regulations that mandate reductions of nitrogen and phosphorus in treated water. Treated effluent from the Manchester plant flows into the Hockanum River, and eventually, into Long Island Sound. Improvements include a new facility to handle solid waste, an odor control system, a new final settling tank, a treatment system to remove phosphorus and other upgrades.
In the current solids handling facility, the material is squeezed between belts and rollers to remove some water. The dried material, which looks like damp ash, falls onto a conveyor belt that dumps into a truck parked below a hopper. But the "solid" material is still about 86 percent water. With new equipment, the goal is to get down to 70 percent water, Emond said. That decrease, he said, will make the operation much more efficient and decrease the burden on the local landfill.
The new odor control system, which residents will no doubt appreciate that much more by fall, is somewhat low-tech. Housed in a rectangular metal container about the size of a double-wide trailer, the system uses seashells as a bio-filter, water and sewer department Administrator Patrick Kearney said. The shells have to be replaced about every 10 years, Kearney said.
The plant upgrade is scheduled to be completed in May 2015, Emond said. The main contractor is Carlin Contracting Co. of Waterford. The project is being financed through the state Department of Energy and Environmental Protection's Clean Water Fund, which is providing a grant covering about 22 percent of the total cost and the remainder through a low-interest loan.
The new plant will return clean water to the environment for the next 20 years, Shanley said. To finish the work, however, the big, dirty job of cleaning out the old tanks is necessary. Fortunately, Shanley wrote, it's a task that must be done "but once in a generation."