Billions of gallons of wastewater are produced across the Chesapeake Bay region each day: originating from homes, schools, businesses, farms, industrial facilities and more. To safely and effectively treat this wastewater—and to reduce the amount of excess nutrients polluting the Bay and its tributaries—hundreds of treatment facilities throughout the Chesapeake Bay region are being upgraded with advanced technology.

What is wastewater?

Wastewater refers to liquid waste or sewage from homes, businesses, schools, industrial facilities and other institutions that flows into rivers, streams and the Chesapeake Bay. It can also refer to runoff from stormwater, agriculture and other sources. Essentially, wastewater is all the used water that originates from households—toilets and bathroom fixtures, kitchens, laundry, lawn and garden irrigation, swimming pools—as well as from industrial, commercial and agricultural activities and polluted runoff. Depending on the source, some wastewater can contain nutrient or sediment pollution, or dissolved chemical contaminants.

What is wastewater treatment?

Billions of gallons of wastewater are produced across the region every day. Before this large amount of wastewater can be released back into the environment, it needs treatment to remove pollutants that may cause harm to waterways, wildlife or humans. At designated treatment plants, typically overseen by a community utility or publish works department, wastewater is treated to reduce pollutants and any harmful substances down to a safe level. After treatment, once the remaining water—called effluent—meets water quality standards, it is discharged back into the environment.

The Chesapeake Bay region is home to 472 municipal and industrial wastewater treatment plants. In most localities, all publicly-supplied water is treated to meet federal drinking water standards, regardless of whether it will be used for drinking.

What pollutants are found in wastewater?

Depending on the source, wastewater can include substances such as human waste, food scraps, oils, soaps and chemicals. It can also include:

  • Excess nutrients—in particular, nitrogen and phosphorus—which can fuel the growth of algae blooms that create low-oxygen "dead zones" that suffocate marine life.

  • Bacteria, viruses and disease-causing pathogens that can pollute beaches and contaminate shellfish, leading to restrictions on recreation, drinking water consumption and shellfish consumption.

  • Metals—such as mercury, lead, cadmium and chromium—which can harm both wildlife and humans.

  • Other substances like pesticides, pharmaceutical products and microplastics, which can pose threats to the health of waterways, wildlife and humans.

The potential presence of these contaminants is why proper and thorough treatment of wastewater is so important.

What is being done to reduce nutrients in wastewater?

Since 1985, Chesapeake Bay Program partners have been working to reduce the nutrient pollution flowing from wastewater facilities into the Bay and its tidal tributaries.

Advanced technologies

In 2005, states in the Chesapeake Bay region began to implement a new permitting process that limited the amount of nitrogen and phosphorus that significant wastewater treatment plants in the region could discharge. To meet the nutrient limits, facilities are being upgraded with nutrient reduction technology, including biological nutrient removal (BNR) and enhanced nutrient removal (ENR):

  • Biological nutrient removal (BNR) uses microorganisms to remove nitrogen and phosphorus from wastewater during treatment. It consists of three steps: an anaerobic step (called enhanced biological phosphorus removal); an aerobic step (called nitrification); and an anoxic step (called denitrification). Wastewater treated at facilities using BNR contains less than 8 milligrams per liter of nitrogen.

  • Enhanced nutrient removal (ENR) improves upon the pollution reductions achieved with BNR. Wastewater treated at facilities using ENR contains 3 milligrams per liter of nitrogen and 0.3 milligrams per liter of phosphorus. Maryland's Bay Restoration Fund—also known as the "Flush Fee"—funds ENR upgrades for the state's 66 major wastewater treatment plants that discharge to the Bay.

Some states, including Pennsylvania and Virginia, have created nutrient trading programs that encourage wastewater treatment plants to design upgrades with greater nutrient reductions, then sell nutrient credits to other facilities. Well-designed nutrient trading programs can provide cost-effective solutions for treatment facilities that need to meet stricter nutrient limits.


Technology upgrades are not the only way area states are reducing nutrients in wastewater. Several laws set strict limits on the amount of phosphorus in consumer cleaning products, including laundry and dishwasher detergents, to slow the flow of phosphates coming from homes.

  • In the 1980s, five of the Bay jurisdictions—Maryland, New York, Pennsylvania, Virginia and the District of Columbia—banned laundry detergents containing phosphates. This reduced the amount of phosphorus flowing to wastewater treatment facilities by 25 to 30 percent, an estimated 7.5 million pounds annually.

  • Maryland, New York, Pennsylvania and Virginia passed bills to ban dishwasher detergents containing phosphorus. The phosphate dish detergent bans, effective July 2010, were expected to prevent an estimated 52,000 pounds of phosphorus from being discharged from treatment facilities.

What you can do

To lessen the amount of pollution in wastewater, follow safe and legal disposal methods of paint, motor oil and other household chemicals. Use toxic-free personal products like lotions, cosmetics and perfumes to keep toxic chemicals from washing down the drain.