Sewage & Septic Systems

Reducing Nitrogen Pollution from Wastewater


With 18 million people living in the Chesapeake Bay watershed, and the population increasing each year, it is not surprising that human waste is one of the major sources of pollution to the Bay.

Traditional sewage plants and septic systems were designed primarily to reduce bacteria, but not the nutrients (nitrogen and phosphorus), found in waste. The Bay suffers from too many nutrients.

The good news is that upgrades and operational efficiencies at sewage plants throughout the Chesapeake Bay watershed have resulted in steep reductions in nutrient pollution. These improvements have been paid for through billions of dollars of public funding, but the benefits from cleaner water far exceed the costs.

Since the regional Bay clean-up plan—called the Chesapeake Clean Water Blueprint—was established in 2010, the wastewater sector cut nitrogen levels from 52 million pounds to 38 million pounds annually, as of 2017. That’s real progress. This reduction far exceeds the 2017 interim pollution goal the Blueprint set for the sector, and effectively meets the 2025 Bay Blueprint target, according to a Chesapeake Bay Program analysis.

One problem looms, however. As more people move into the Bay area, flows to sewage treatment plants will continue to increase, along with pollution. Moving forward, jurisdictions will need to ensure that this sector maintains its nutrient and sediment pollutant limits in the face of growing populations, increased storm events, sea level rise, temperature changes, and other factors.

The significant progress reducing pollution from sewage plants has not been matched in more suburban and rural areas where onsite septic systems are used to treat human waste. These backyard systems handle a large portion of household waste in many counties in the Bay region. Nitrogen pollution from septic systems is actually increasing, reaching about 8.5 million pounds a year. The 2017 interim goal for the sector was 7.1 million pounds discharged annually.

Nitrogen and phosphorus pollution cause algae blooms that block sunlight to underwater grasses and remove oxygen from the water, creating "dead zones"—areas of the Bay that have too little oxygen to support a healthy ecosystem. These problems degrade habitat for key plants and animals in the Bay's ecosystem, including underwater grasses, crabs, rockfish, and oysters.

To keep states on track to meet sewage and septic pollution reduction goals, the CBF is:

  • ensuring Clean Water Act permits for sewage treatment plants contain limits that are consistent with the Chesapeake Clean Water Blueprint;
  • advocating for state and federal funding to pay for upgrades to sewage plants and septic systems;
  • educating the public and elected officials about the impact of nutrient loads from septic systems on local water quality.

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