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Wastewater Department


The Wastewater Treatment Department is dedicated to collecting and treating wastewater that flows into our facility from Nashua and Hudson and delivering a clean, clear effluent into the Merrimack River. The Wastewater Treatment Facility is located at 2 Sawmill Road in the City of Nashua. The Department is under the umbrella of the Division of Public Works.
The first wastewater treatment tanks were installed at the Nashua Wastewater Treatment Facility in 1959. At that time only a small portion of Nashua's flow came into the facility. In 1974, the facility was expanded. New interceptor lines in the city assured that all wastewater flow came into the facility. The facility was upgraded to secondary treatment in 1989 with a design flow of 16 million gallons per day. In 1998, the city started construction of a $10 million dollar anaerobic digester complex, which went on line in December 2000. In December 2014, a $12 million underground combined sewage treatment facility opened along Bancroft Street. This new facility helped to reduce combined sewer overflows into the Nashua and Merrimack rivers.
The city is working to eliminate the combined sewer overflows (CSOs) that are discharged into the Nashua and Merrimack rivers. CSOs occur when storms overpower the collection system and cause wastewater and storm water to be dumped into the rivers without treatment. The program will cost over $100 million dollars.

Plant Flows:
Design Flow = 16,000,000 gallon per day
Average Daily Flow = 13,000,000 gallon per day
Total Flow (One Year) = 4,867,000,000 gallon
Total Septage (One Year) = 375,000 gallons

Plant Efficiency:
Biochemical Oxygen Demand (BOD) = 92% removal on average
Total Suspended Solids = 95% removal on average

WWTF Information:
Process Information
Industrial Pretreatment
Rules for Septage Disposal


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