Controlling Nutrients

Nutrient management remains a pressing concern for the state. With funding from WRRI, Hans Paerl, of the University of North Carolina-Chapel Hill Institute of Marine Sciences, helped characterize the nitrogen cycle of the Neuse River. By cataloging the sources and sinks of the nutrient, Paerl’s findings have helped researchers and managers understand contributions to algae blooms and lowered water quality that have plagued the waterbody. Wayne Robarge, of NC State University, helped quantify the input of nitrogen to the Neuse River system from dry deposition originating from intensive animal production operations.

Constructed stormwater wetlands and vegetated buffers can reduce excess nutrients in water. These systems remove nitrogen by transforming it into inert nitrogen gas. Research by Bongkeun Song of the University of North Carolina-Wilmington helped characterize the microbial processes that allow this transformation to occur. Song suggests vegetation that can be used in stormwater wetland construction to maximize nitrogen removal. Deanna Osmond, of NC State University, studied the nitrogen reduction values of shrub buffers used in the Neuse River Basin. This effort helped increase the number of best management practices available to farmers in the region.

Stormwater Management

WRRI funding for research in stormwater management has resulted in changes to the NCDENR Stormwater BMP Manual. Bill Hunt, of NC State University, has conducted research into mitigation strategies for reducing the flow of stormwater and reducing stormwater pollutant inputs into receiving waterbodies. Results of Hunt’s research have been used to in multiple NCDENR Stormwater BMP Manual revisions. Hunt’s use of drainage modeling software originally created for agriculture has allowed researchers to better evaluate stormwater BMPs. Additionally, research by Richard McLaughlin, of NC State University, into the use of polyacrylamide to reduce erosion at construction sites has provided managers multiple options for controlling and reducing sediment pollution associated with stormwater runoff from disturbed sites.

Potable Water Supply

Recent state legislation calls for an increase in the use of reclaimed water. Mark Sobsey, of the University of North Carolina-Chapel Hill, developed new methods to detect and quantify pathogens in reclaimed water. Sobsey is building upon these findings by looking at the microbial quality of reclaimed waters in North Carolina and providing assessments of health risks based upon various water-exposure scenarios.

Reuse of graywater, or water from bathing and washing facilities that are not toilets or food preparation areas, also has potential to reduce pressures on source water. Francis de los Reyes, of NC State University, used advanced molecular techniques to quantify the pathogens found in graywater. De los Reyes then used the findings to quantify the risk of infection associated with a wide range of exposure scenarios.

Orlando Coronell, of UNC-Chapel Hill, has described the fouling properties of local source water on nanofiltration and reverse osmosis installations in the state and provided corresponding cleaning strategies. This information provides water treatment plant operators with locally tailored information about optimum cleaning strategies for membranes.

Toxic Chemicals and Wastewater Treatment

Increasingly, the public is concerned about chemicals in drinking water. Detlef Knappe, of NC State University, analyzed the removal effectiveness of drinking water treatment processes that are currently employed by members of the North Carolina Urban Water Consortium. He determined, at a bench scale, what processes were most effective in removing some of the most common biochemically active compounds.

Knappe is closely examining the occurrence of, and treatment options for, 1,4-Dioxane in North Carolina drinking water sources. The chemical, which is an industrial and manufacturing byproduct of processes involving the chemical ethylene oxide, is a human health concern as a probable carcinogen. It has been found in drinking water in multiple locations in the state. Working with wastewater treatment plants to create methods for identifying sources, Knappe is determining the factors that control concentrations.