Derry WWTF - Municipal Wastewater Treatment Plant in Derry, New Hampshire

Derry WWTF is a municipal wastewater treatment facility located in Derry, Rockingham County, New Hampshire. The plant serves a population of about 28,478 residents, placing it in the medium-agglomeration category for US wastewater infrastructure. As a US facility, Derry WWTF operates under the Clean Water Act, which requires National Pollutant Discharge Elimination System (NPDES) permits for all point-source discharges. Plants serving populations of this scale typically employ secondary treatment as a minimum standard, with potential for advanced treatment depending on local water quality requirements. The plant discharges treated effluent into the local watershed, which ultimately drains to the Atlantic Ocean via the Merrimack River basin. The receiving waters support diverse aquatic life and are important for regional water quality management in southern New Hampshire.

Derry WWTF discharges into the Merrimack River watershed, which flows southward through New Hampshire and Massachusetts before emptying into the Gulf of Maine, Atlantic Ocean. The watershed supports diverse aquatic ecosystems, including fish populations such as Atlantic salmon and river herring, and is a critical resource for drinking water and recreation in the region.