CHATHAM – South Chatham residents will be happy to learn that they'll soon no longer have to worry about stains from high iron levels in water pumped from a town well in their neighborhood. In September, water from well number seven will begin flowing through the town's new water treatment plant, a $10 million facility designed to remove high levels of iron and manganese from drinking water.
Currently, the plant off Morton Road is treating water from well number 6, which has been offline for several years due to high manganese levels. Despite a relatively dry summer, the town's water system has been able to keep up with demand and avoid taxing wells by relying on the additional one million gallons a day being pumped from the well.
High iron and manganese levels have been problems for years in three wells located in the South Chatham area. While well six has been kept offline due to “very high” levels of manganese, said Chief Water Operator Lynn Carr, wells seven and nine have been used at lower volumes due to slightly lower, but still high, levels of manganese, plus the high iron in well seven.
Wells seven and nine as scheduled to begin flowing into the treatment plant in September, said Department of Public Works Director Tom Temple.
Two years ago, when conditions were dry and water demand spiked, town wells were pumping at up to 21 hours per day, which not only draws down the aquifer, and potentially allow bacteria into the water, but taxes the machinery. Last year's summer was wet and there wasn't a pumping problem; this year has been drier and usage is up, but with the additional water from well six the department has kept up with demand running other wells at a more acceptable rate of 15 or 16 hours a day, Temple said.
So far this year, the water department has pumped 15 million gallons more this year than last, but a third of that was used in testing, backfilling and other operations associated with the new treatment plant.
The new plant, which began operating on July 5, includes four large pressure vessels in the main filter room. Two run at any one time and can treat up to three million gallons of water a day. The filters are run for about 35 hours and then taken offline for backwashing and cleaning.
Raw water coming into the plant has a pH level of about six, which is very acidic. Potassium permanganate
is mixed into the water in a large basin, located under the floor, to bind and remove the manganese, while chlorine is used to oxidize both the iron and manganese. The water is then filtered through gravel, a proprietary material called Green Sand Plus, and anthracite in the vessels. An aeration tower raises the pH, and the water exits the plant at a more neutral pH of 7.3 to 7.5.
“It's actually very simple,” said Carr. “It's just getting the chemistry just right.”
The water coming into the plant is clear; once the chemicals are added to bind the iron and manganese, it turns a rusty brown. Then, once treated through the filter vessels, the final product is crystal clear.
The original design of the plant included lagoons for disposal of the waste left over from the filtration process, but that would have required clearing of more area. The waste is instead being pumped and driven to the wastewater treatment plant; eventually, once new sewer mains go down Route 137 as part of the project tying East Harwich into the sewer system, the water treatment plant will be connected to the sewer line. In addition, the water used to backwash the filter vessels is recycled, Temple said.
The plant also includes a lab and office. It's not complete yet, but when it is it will include large-screen monitors showing plant operation levels; those are currently monitored on a PC. Sections of flooring are also awaiting completion, and blue tape labels are standing in for signs which are now being produced.
The total cost of the treatment plant was more than $10 million, which came in appropriations at two town meetings. In May 2014 voters approved $5,533,000, with a second vote in May 2016 for $3.5 million. According to Finance Director Alix Heilala, additional funds were used from separate water main articles to help pay for water main work associated with the plant.
Two new South Chatham wells, numbers 10 and 11, are being completed with funds appropriated at this year's annual town meeting. Those wells also have high manganese levels. The three wells slated for treatment in the new plant will take up its entire three million gallon a day capacity, but it may be possible to blend in water from wells 10 and 11 to avoid having to build another treatment plant, Temple said. Officials are looking into that possibility.
In the meantime, he urged residents to adhere to the voluntary water restrictions in order to minimize use of town water and save wear and tear on the wells. Even with the additional capacity, it's not healthy to tax the aquifer too much, he said.