Nutrient Removal: Everywhere, All the Time?

By Jeanette Brown, 2008-2009 Vice-President of the Water Environment Federation

As water quality experts know, many treatment plants throughout the United States are required to remove nitrogen, phosphorus or both. And if you manage or work at a utility like mine, in a region where nutrient removal is required, you know there are significant related costs, both capital and operating, as well as increased process monitoring requirements. As stewards of the environment, we take great pride not only meeting permit requirements but also in trying to achieve much greater removal of pollutants. Now we must all address a fundamental question as to whether or not every water body would benefit from nutrient removal. It’s complicated, because while we strive for the cleanest water possible, we understand this objective must be balanced against most effective use of environmental resources and diverse considerations that impact water quality at the regional and local levels.

The Natural Resources Defense Council (NRDC) has petitioned EPA to issue generally applicable nitrogen and phosphorus removal requirements for wastewater treatment plants. They contend that total phosphorous limits of 1.0 mg/L and total nitrogen limits of 8.0 mg/L are consistently attainable on an annual average basis using current secondary treatment technology. They also contend that many treatment plants are currently doing this with either a slight increase in cost or in some cases reduction of costs.

Many of us who currently operating nutrient removal plants have some concerns about this proposal because we understand how cold temperatures, wet weather and changing influent characteristics can impact nutrient removal efficiencies. In order to evaluate this petition, which will certainly be a hot topic at the upcoming Nutrient 2009 meeting, members of WEF and the National Association of Clean Water Agencies (NACWA) developed a questionnaire which has now been completed by many plants throughout the country. The results give us an understanding of the processes used at plants, whether or not they are doing nutrient removal, effluent quality, and costs. The goal is to provide EPA with expert advice as they continue to address nutrient criteria and issues.

Additionally WEF has convened a nutrient issues workgroup. This workgroup is assessing base line performance of conventional secondary treatment plants that evaluate how much nitrogen and phosphorus can be removed by the process. They are also evaluating state-of-the-art processes for nutrient removal, including cost and performance.

It is vitally important that we continue to thoroughly address this question of universal benefits of nutrient removal before any final decision is made to mandate generally applicable nutrient removal requirements. As stewards of clean water, we all have a stake in the answer, and I’d appreciate your thoughts.

P.S. You may want to check out the Nutrient Removal Knowledge Center on WEF's website for more information.