August 2013, Vol. 25, No.8

Research Notes

Removing endocrine-disrupting compounds from the water stream

Adding one more step to water treatment can help remove endocrine-disrupting compounds. University of Texas at El Paso researchers are developing a process to remove these compounds from reclaimed and drinking water, according to a university news release.  

The compounds, found in such household and industrial products as detergents and pesticides, can disrupt the hormonal balance in humans and wildlife. After humans use or consume products containing endocrine-disrupting compounds, the chemicals end up at water resource recovery facilities, which cannot entirely remove them from the water, the news release says.  

Wen-Yee Lee, associate professor of chemistry at the university and the study’s principal investigator, sampled local wastewater before and after treatment to find that much of the compounds escape treatment and re-enter the environment through reclaimed and drinking water, the news release says.  

To remove the compounds, Lee’s research team constructed additional disinfection processes using ultraviolet rays and chlorination to help achieve removal, the news release says. 

The team continues to refine this process, aiming for complete removal of the compounds, and plans to expand the study to six municipal water resource recovery facilities in El Paso and Socorro, N.M. While these compounds currently are not regulated, the team hopes their findings will provide an effective treatment process to respond to any future potential regulations, the news release says. 

  

Nitrogen moves slowly through groundwater 


Nitrogen does not move through groundwater channels in a matter of days, months, or even years; it can take decades, according to U.S. Geological Survey (USGS) hydrologic researchers.
 

The researchers examined surface and groundwater at seven sites across the United States and determined that nitrate in streams was derived from groundwater, according to a USGS news release. This occurred mainly in groundwater-dominated watersheds where rivers and streams are fed predominantly by groundwater held in underground aquifers.  

To determine the time nitrate takes to reach a stream from groundwater, the researchers conducted an age-dating tracer study in the Tomorrow River in central Wisconsin.  

“Findings indicated that decades-old nitrate-laden water currently was discharging to this stream,” the news release says. The researchers determined that base-flow nitrate concentrations in the stream may be sustained for decades regardless of current and future practices. 

The study was conducted because water quality experts recently have been documenting that nitrate trends in streams and rivers do not meet expectations based on reduced regional use of nitrogen-based fertilizer. Long travel times of groundwater discharge have been suggested as the factor likely responsible for these observations, the news release says. 

The delay means that changes in the use of nitrogen-based fertilizer, a typical source for nitrate in waterways, may take decades to be fully observed in streams, the research indicates. And because waterways obtain more water from groundwater during low flows, nitrate concentrations increase during low and moderate flows in large rivers, the news release says. 

A report on the study results, “Vulnerability of Streams to Legacy Nitrate Sources,” was published in the journal Environmental Science and Technology. 

    

Gasoline-denatured ethanol shows promise for denitrification  

  

During biological nutrient removal, water resource recovery facilities add carbon to post-anoxic denitrification process. Using three lab-scale sequencing batch reactors, researchers evaluated the performance of three carbon sources — methanol, ethanol, and gasoline-denatured ethanol. Results of the study are published in the June issue of Water Environment Research. 

After examining the treatment efficiency and cost of each carbon source, the researchers determined that the use of gasoline-denatured ethanol was “very promising,” the article says. 

While this carbon source costs more than methanol, it had the benefits of high denitrification rates, a higher observed growth yield, commercial availability, ready biodegradability, short adaption periods, and no federal alcoholic beverage tax. “Utilities will have to decide if it is worth paying a little extra to take advantage of its benefits,” the report says. 

To enhance the potential use of denatured ethanol in denitrification, the researchers note a need to examine the efficiency of denatured ethanol at cold temperatures through long-term operations on a larger scale, to determine the possibility of using substrates interchangeably, and to determine a maximum specific growth rate and half-saturation constant, the report says. 

The report, “Evaluation of Gasoline-Denatured Ethanol as a Carbon Source for Denitrification,” is available as an open-access document and can be downloaded free at http://goo.gl/yYAEH. 

 

Water Environment Research  allows open access to one article per issue on a range of important technical topics such as nutrient removal, stormwater, and biosolids recycling.