Wastewater Treatment

Hundreds of wastewater treatment facilities throughout the Chesapeake Bay watershed are being upgraded with advanced technology to reduce the amount of nutrients that are discharged into the Bay's tributaries. Wastewater treatment plant upgrades account for a large portion of overall estimated nutrient reductions to date, and Bay jurisdictions are relying on additional reductions from wastewater to achieve about 15 percent of total overall nutrient reduction goals.

Chesapeake Bay Program Goal to Reduce Nutrients in Wastewater

Since 1985, the Chesapeake Bay Program has been working towards a goal to reduce nutrient pollution from wastewater facilities to correct nutrient-related problems in the Bay and its tidal tributaries by 2010. As of 2008, the seven Bay jurisdictions – Delaware, Maryland, New York, Pennsylvania, Virginia, West Virginia and the District of Columbia – have met 67 percent of the goal to reduce nitrogen from wastewater and 91 percent of the goal to reduce phosphorus from wastewater.

Using Technology to Reduce Nutrients in Wastewater

In 2005, Chesapeake Bay jurisdictions began to implement a new permitting process that limited the amount of nitrogen and phosphorus that the Bay watershed's 483 significant wastewater treatment plants could discharge. To meet the nutrient limits, most of these 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 (mg/l) of nitrogen.
• Enhanced nutrient removal (ENR), which is being used in Maryland, improves upon the nutrient reductions achieved through BNR. Wastewater treated at facilities using ENR contains 3 mg/l of nitrogen and 0.3 mg/l 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 be beneficial because they provide cost-effective solutions for some treatment facilities that need to meet stricter nutrient limits.

Legislation to Reduce Phosphates in Wastewater

Technology upgrades are not the only way Chesapeake Bay jurisdictions are reducing nutrients in wastewater. Several laws have been passed that 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 Bay watershed 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 move reduced the amount of phosphorus flowing to the watershed's wastewater treatment facilities by 25 to 30 percent, or an estimated 7.5 million pounds annually.
• Maryland, New York, Pennsylvania and Virginia have recently passed bills to ban dishwasher detergents containing phosphorus. The phosphate dish detergent bans, which will go into effect in July 2010, will remove an estimated 52,000 pounds of phosphorus that is currently being discharged from treatment facilities.