But by 2015, regulations that govern trihalomethanes (THMs,) when chlorine is used to disinfect drinking water, are forcing the Danvers/Middleton drinking water plant to spend $21 million to redesign the treatment process.
Once the work begins, it will take about two years to complete the expansion and renovations of the plant
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. Ozone reduces THM formation by replacing ozone as the primary oxidant/disinfectant. While chlorine is retained for secondary disinfection, the lower overall chlorine levels reduce the formation of chlorine based THM/other disinfection by products.
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.