The town reopened the Vernon C. Russell Water Treatment plant, which had been closed for five weeks because of a construction project. Located on Lake Street in Middleton, the plant treats water from Middleton Pond Reservoir, the primary water supply for Danvers and Middleton, and from nearby Emerson Brook. Danvers, which also has two wells, supplies water to both towns. The $21 million construction project is designed to enhance the effectiveness of the plant’s treatment, improving water quality and allowing the plant to meet drinking water requirements for the next 20 years. During the time the plant was offline, Danvers supplied water by using a combined 1.6 million gallons a day from its two wells on the Ipswich River, a step that required approval from the state Department of Environmental Protection because the wells normally operate only in the winter and spring due to flow conditions on the river. The town purchased another million gallons of water a day from the Salem-Beverly water system, according to Bob Lee, director of operations for the Department of Public Works. During the shutdown, Danvers and Middleton both imposed bans on outdoor water use, which helped reduce demand. Those restrictions were lifted this past week. The project is expected to be completed by next summer.