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New water quality standards will affect wastewater treatment plants

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The expected release of new wastewater discharge permit limits next year could require extraordinary changes for smaller Mississippi towns operating treatment lagoons, while larger cities' mechanical plants may also need some upgrades to meet the new restrictions.

The Mississippi Department of Environmental Quality (MDEQ) is developing water quality standards for nutrients in order to meet court-mandated environmental reforms authorized decades ago by the federal Clean Water Act but not fully implemented. The new limits will require wastewater treatment systems to meet limits for total nitrogen and total phosphorus for the first time, and could render some lagoons and plants obsolete overnight, said WGK, Inc. engineer Jon Huey, PE, BCEE, PhD.

"Many wastewater treatment systems in Mississippi are going to have to meet the new nutrient limits," said Huey, who spent 27 years with MDEQ, finishing his service there in the Environmental Permits Division. "Most small communities have lagoons, facultative or aerated, and many lagoons simply cannot be upgraded in any reasonable way to meet these limits. But it takes years to find funding and to plan, design and build a new wastewater treatment plant. This whole thing is going to be expensive."

Several cities and towns in Mississippi already have nutrient limits measured by daily load (pounds per day). Many of those municipalities are meeting their load limits because their wastewater treatment plants are not operating at full design flow, due to lower-than-expected population growth or, in the case of the Gulf Coast, population loss experienced after Hurricane Katrina. However, the new nutrient regulations expected next year will likely establish nutrient concentration limits (milligrams per liter), effectively closing a loophole for maintaining compliance. Most municipal wastewater treatment systems will be unable to meet those limits without upgrades.

The new nutrient concentration standards were required by the Clean Water Act of 1972 and are only now being developed. The standards are meant to protect the water quality of the nation's rivers and estuaries and to combat the "dead zone" in the Gulf of Mexico, an oxygen-starved area of the Gulf caused by excessive nutrient content.

Some areas of the U.S. have had nutrient limits for years. Such regulations are common around the Great Lakes and Chesapeake Bay states, areas recognized as being sensitive habitats and where water quality is excellent. The rest of the nation is now dealing with the impending rules in the same manner as Mississippi.

"As far as gathering the required data to set nutrient standards, Mississippi is ahead of most states," Huey said. "MDEQ has been gathering this data for several years now, while many states have taken a wait-and-see approach."

WGK has likewise not taken a wait-and-see approach, but instead is actively working with the municipal owners of more than a dozen wastewater treatment plants, ranging in capacity from 50,000 Gallons Per Day to 5 million GPD, to develop master plans for funding and treatment options to meet the anticipated nutrient limits.

WGK, Inc. Principal Greg Gearhart, PE, BCEE, said the firm's engineers have developed competence in each of four approaches for economically meeting the new requirements: no-discharge systems, packaged treatment systems, consolidating smaller systems with larger systems and developing phased upgrades for existing plants capable of meeting the new nutrient limits.

Some current WGK projects being performed in anticipation of the new nutrient standards are not necessarily treatment projects, but are designed instead to make future treatment projects more economical, Gearhart said.

"We are helping our clients with lagoons think two steps ahead. Until now, a moderately leaky sewer system flowing into a lagoon might introduce hundreds of thousands of gallons of infiltrated rainwater to be treated, but usually has not significantly increased the cost of that treatment. But when you transition to a nutrient removal system, typically part of the process takes place in constructed tanks, and then it becomes very important to eliminate inflow and infiltration to minimize both the volume of wastewater you have to treat and the size of the treatment tanks," he explained. "We've worked with a number of clients to apply for Community Development Block Grants to focus on eliminating this extra rainwater and reduce their eventual cost of meeting these new limits."

Gearhart said anyone operating a wastewater treatment plant who is unsure of how their facility is prepared to meet next year’s expected nutrient limits should contact WGK immediately for an evaluation.

"Let us come sit down and explain exactly what you're facing. We can check your permit status and then meet with you to develop a timeline for compliance and help you develop and choose options in the most cost-effective way," he said. "This is something you don't want to put off. The longer you wait, the fewer options are available - particularly if you need to assemble a series of grants and loans to achieve compliance."

It remains unclear how industrial wastewaters will be affected, or if the smallest wastewater systems will be exempt. Nutrient limits for the Mississippi Delta will not be released until November 2014.