Question of the Week: Wastewater Treatment Plants
Welcome to the latest installment of the BayBlog Question of
the Week. Each week we take a question submitted through the Chesapeake Bay Program
website and answer it here for all to read.
This week’s question comes from Matt:
“How are limits at wastewater treatment plants set? Is it
based on water quality standards or limit of technology?”
Ultimately, nutrient discharge limits for wastewater
treatment plants in the Chesapeake Bay
watershed are set to improve water quality, but many plants face limitations
because of technological capabilities. Nutrient discharge from wastewater
treatment facilities is one of the biggest causes of poor water quality in the
Bay. Because of this, the Chesapeake Bay Program has been working to reduce
nutrient pollution from these sources since 1985.
In 2005, the Chesapeake Bay
jurisdictions introduced a new permitting process limiting the amount of
nitrogen and phosphorous that the watershed’s 483 major wastewater treatment
plants could discharge. These limits meant that most facilities had to make
major renovations and upgrades to include biological nutrient removal and
enhanced nutrient removal technologies.
In the biological nutrient removal (BNR) process, microorganisms
remove nitrogen and phosphorous from wastewater during treatment. The
wastewater treated in this process contains less than 8 milligrams per liter
(mg/l) of nitrogen. Enhanced nutrient
removal improves upon the BNR process, with wastewater treated at these plants
containing 3 mg/l of nitrogen and 0.3 mg/l of phosphorous.
Some of those facilities that are required to meet stricter
limits but cannot afford more advanced upgrades still have options. Nutrient
trading programs have been implemented in Pennsylvania
and Virginia
for precisely that reason. These programs encourage facilities to invest in upgrades
with greater nutrient reductions and then sell their excess nutrient credits to
other facilities. This provides plants a cost-effective way to meet the limits
imposed on them to improve water quality if they are lacking the technological
advances.
And remember, you can do your part to help wastewater
treatment plants reduce nutrient discharge too. Two easy steps are conserving
your water so the facilities have less water to treat and switching to low- or
no-phosphorous dish detergents. For more information, check out our Wastewater
Treatment page.
Do you have a question about the Chesapeake Bay? Please send it to us through our web comment form. Your question might be chosen for our next BayBlog Question of the Week!