SEAL HARBOR STP - Bar Harbor, Maine Wastewater Treatment Plant

SEAL HARBOR STP is a municipal wastewater treatment plant located in Bar Harbor, Maine, United States. The plant serves a population of approximately 5,915 residents in the Northeast Harbor area of Hancock County. As a secondary treatment facility, it provides biological treatment to reduce organic matter and suspended solids before discharge. The plant has a designed capacity of 1,245.40 thousand cubic meters per year and currently treats an annual volume of 829.01 thousand cubic meters. Under the U.S. Clean Water Act, secondary treatment is the minimum standard for municipal wastewater plants, and facilities of this scale are typically regulated through National Pollutant Discharge Elimination System (NPDES) permits issued by the Maine Department of Environmental Protection. The plant's proximity to the coast (within 10 km) means its treated effluent likely discharges into a coastal watershed that drains into the Gulf of Maine. The Gulf of Maine is a biologically productive marine ecosystem supporting fisheries, marine mammals, and seabirds. Proper treatment is essential to protect water quality and aquatic life in the receiving waters.

The plant discharges into a coastal watershed that ultimately drains into the Gulf of Maine, a semi-enclosed sea of the Atlantic Ocean. The Gulf of Maine supports diverse marine life, including commercially important fish species and endangered North Atlantic right whales. As a coastal facility, the plant's nutrient and pollutant loads can affect local estuaries and nearshore habitats, making effective secondary treatment critical for maintaining ecological balance.