Blue Plains, which handles the wastewater for 2.3 million people in Maryland, Virginia, and Washington, D.C., is one of the country’s largest sewage treatment facilities. DC Water spent $US 1 billion recently to upgrade the plant’s nutrient removal equipment. Photo © J. Carl Ganter / Circle of Blue
The U.S. Environmental Protection Agency calls nutrient pollution the “single greatest challenge to our nation’s water quality.” Rising concentrations of nitrogen and phosphorus in waterways, the agency reports, are a significant threat to human health, ecosystems, and local economies.
Nutrient pollution has reached an alarming intensity in many of the nation’s waterways. The shutdown of the drinking water system in Toledo, Ohio, in 2014 was the most visible example of what is now a coast-to-coast challenge. More than 40 percent of lakes, rivers, and streams, according to the EPA, have concerning levels of phosphorus. Mats of green muck in the St. Lucie estuary earlier this summer prompted Florida Gov. Rick Scott to declare a state of emergency in four coastal counties. As of mid-August, authorities across the country had issued more than 250 health advisories this year for toxic algae. A warming climate adds another degree of difficulty.
“While many entities have taken meaningful actions to reduce nutrient pollution, there continues to be a pressing need for concerted action to reduce nutrient pollution nationwide,” Joel Beauvais, head of the EPA water office, wrote in a letter sent to state officials on September 22.
Despite the urgency, the EPA lacks basic information for understanding the scope of the problem and recognizing potential solutions.
It does not, for instance, have a comprehensive database on the location and performance of the nation’s more than 16,000 wastewater treatment facilities, which, for some bays and rivers, are the largest source of nutrient pollution. Only one-third of the largest facilities have enforceable limits on nitrogen and phosphorus discharges, and less than two-thirds are required to monitor the two pollutants.
To bridge the knowledge gap, the EPA announced last week that it is developing a national census of wastewater treatment facilities. The goal of the study, which will proceed in phases over four to five years, is two-fold: first, to map the facilities and identify the treatment technology they use. The second, is to determine how effective the facilities are at removing nutrients, with an emphasis on successful, low-cost strategies that lower energy demands and do not require a large capital investment. Existing case studies indicate that such outcomes are possible.
“This census is extremely important for setting a baseline as we think about infrastructure improvements in the coming decades that target resource recovery and energy-neutral or energy-positive wastewater treatment,” George Wells, an assistant professor at Northwestern University who studies wastewater treatment, told Circle of Blue.
Understanding the Challenge
Wastewater treatment plants are not the lone culprit in nutrient discharges to water, and in many cases are not even the ringleader. Fertilizers from farm fields and lawns, or nitrogen in the atmosphere that dissolves into water also contribute.
But wastewater plants can be a significant source. Half of the nitrogen in Manhasset Bay, on Long Island, is from wastewater plants, according to a Nature Conservancy analysis. In the Chesapeake Bay, by contrast, only one-sixth of the nitrogen and phosphorus is from sewage treatment facilities. Farms in the six-state watershed are the larger problem.
Nutrient pollution, as it turns out, is a legacy of one of the nation’s landmark environmental laws. The Clean Water Act, signed in 1972, required sewage facilities to upgrade their services, and provided federal grants to aid the transition. In addition to skimming off the solid waste, facilities had to add a second step: the use of microbes to digest organic matter. Requiring secondary treatment resulted in cleaner water but it removes only a fraction of the nitrogen and phosphorus. Eliminating those plant vitamins requires additional investment that many facilities are only now considering.
The Chesapeake Bay example is a success story that other watersheds would like to emulate. Wastewater treatment facilities cut their nitrogen discharges to the bay by 57 percent and phosphorus by 75 percent in the last three decades. The reductions are producing positive trends for environmental health. The University of Maryland Center for Environmental Science gave the bay ecosystem one of its highest ratings in three decades last year, albeit a C grade.
Those improvements, however, came with a significant price tag for utility customers. Wastewater facilities in the bay watershed invested $US 7 billion to cut nutrient discharges. That is a heavy financial lift for some communities. The purpose of the EPA census is to find ways of reducing nutrient pollution at lower cost.
The EPA already has other showcase examples. In August 2015, the agency released a report highlighting operational changes that resulted in greater nitrogen and phosphorus removal. Operational changes cover more than a dozen actions, including reducing the amount of oxygen that aerators introduce into the waste stream, adjusting chemical levels, and building up wetlands and swales at the end of the pipe for additional filtration before the effluent enters the river.
These approaches can reduce nutrients at far less cost than a new capital project. Victor Valley Wastewater Reclamation Authority, which serves 400,000 people in Southern California, cut total nitrogen discharge by roughly 25 percent by modifying its aeration process. The operational change cost $US 1.1 million compared to an $US 80 million capital investment for a unit designed to remove nitrogen. Victor Valley earned side benefits too. The changes cut energy use and reduced operating costs at the plant by 10 percent.
These are the sorts of hard data and examples that the EPA is seeking in the census. The agency wants to provide a database of nutrient removal performance and help facility operators understand the most effective ways of removing nutrients. The data will also help regulators set achievable nutrient reduction targets.
The EPA is invoking its information-gathering powers under the Clean Water Act to require utilities to submit data. The mandatory response is due to concern that voluntary effort would lead to few submissions. The EPA says that responses are for research only, not for identifying rule breakers, who might exceed pollution limits.
