WATER AND WASTEWATER DIVISIONS

Wastewater Treatment

The Haverhill Wastewater Treatment Plant (WWTP) is located off South Porter Street, along the Bradford side of the Merrimack River, in the southeast portion of the city. The plant became operational in 1977 and has the following facilities:

• Screening
• Primary settling
• Secondary treatment using an activated sludge process
• Disinfection with sodium hypochlorite

Detention time for disinfection is achieved by passing through 1,200 feet of 102-inch outfall followed by 800 feet of 60-inch outfall before entering diffusers that discharges to the Merrimack River. Primary sludge is processed in cyclones to remove grit and then gravity thickened. Waste activated sludge is thickened in dissolved air-flotation thickeners. The thickened primary and waste activated sludges are combined and dewatered in centrifuges.

Wastewater Treatment Plant Design Parameters	Value
Influent Flow (mgd)
Average Daily Flow	10 million gallons per day
Maximum Daily Flow	18.1 million gallons per day
Peak Flow	46 million gallons per day

A single pump station pumps all flow from the terminus of the Bradford interceptor to the treatment plant. This station is designed for a peak flow of 46 mgd with 3 pumps in operation and the fourth pump as a standby. Connecting the pump station to the WWTP is a 42-inch force main with a length of approximately 3000 feet.

The Wastewater Treatment Plant is permitted through the National Pollutant Discharge Elimination System (NPDES). The permit expires every five years at which time the City has to apply for a renewal. The current permit was issued on June 26, 2003. The permit establishes the discharge limitations for the plant under the Clean Water Act.