Following plant upgrades and improved techniques at Portland’s East End Wastewater Treatment Facility in 2017, struggling eelgrass beds near the facility’s discharge outfall have rebounded and we have observed a decline in nuisance algal blooms in lower Back Cove.
Portland’s East End Wastewater Treatment Facility, the largest treatment plant in Maine, has removed approximately 1.5 million pounds of nitrogen from its discharges over the past four years. Nitrogen is a nutrient that supports healthy marine ecosystems, yet excess nitrogen from human sources such as wastewater, industry, transportation, and stormwater, can degrade water quality and harm the marine environment. In 2017, Portland Water District reconfigured the facility’s aeration basins and began denitrification, a process that converts nitrogen in the wastewater into a harmless gas. These improvements followed collaborative discussions between Portland Water District, Friends of Casco Bay and the Maine Department of Environmental Protection as the Department was renewing a Clean Water Act permit for the treatment facility.
Why is this a big deal for Casco Bay? Some regions of Casco Bay suffer from excess nitrogen pollution, and keeping 1.5 million pounds of this nutrient out of our waters is great news. In Casco Bay, a healthy amount of nitrogen supports the base of the marine food web by encouraging plant productivity and algal growth. Too much nitrogen however, can lead to nuisance and harmful algal blooms, contribute to coastal acidification, and degrade eelgrass — a vital habitat in the Bay.