August 2014, Vol. 26, No.8

Research Notes

Lighting the way to real-time fecal contamination detection

Detecting fecal contamination in water just became more accurate. Researchers have developed a technology that detects in water trace amounts of urobilin, a byproduct excreted in urine and feces of many mammals such as humans and livestock.  

Traditional detection methods are limited by high costs, small sample sizes, and lengthy analysis times. But this technology finds indicators of fecal contamination thousandths- and even millionths-of-times smaller than those found by conventional methods. It also can be produced for a few hundred dollars, and is capable of analyzing large samples in real-time, according to a Texas A&M University (College Station) news release.  

When mixed with zinc ions, urobilin forms a phosphorescent compound and gives off a greenish glow when examined under ultraviolet light. But samples with low concentrations only give off a weak glow, making it difficult to analyze the sample.  

Vladislav Yakovlev, professor in Texas A&M University’s Department of Biomedical Engineering, worked with a team to thoroughly excite extremely small amounts of urobilin in large samples of water. The researchers collected the resulting phosphorescent emission with the help of a device they referred to as an “integrated cavity,” the news release says. 

The integrated cavity is a hollow cylindrical container manufactured in Yakovlev’s laboratory. A water sample is placed inside the cylinder where it interacts with zinc ions. A laser light is used to excite the urobilin compound in the sample, causing even low levels of urobilin to glow. The only way light exits the cylinder is through the hole it entered by, allowing researchers to efficiently collect the resulting phosphorescent emission and direct it to a photo detector such as a spectrometer for analysis, Yakovlev explained in the release.  

Using the integrated cavity, the team of researchers detected the presence of urobilin down to a nanomole per liter. And because the system is capable of sampling a larger water sample, it promises a more accurate analysis of a system’s overall water quality, Yakovlev said in the release. 

Yakovlev and the team are working to commercialize the technology. The research is featured in the journal Proceedings of the National Academy of Sciences. 

 

Carbon nanomaterials will travel 

As use of graphene and other carbon-based nanomaterials in electronics increases, their potential to affect the health of humans and the environment also increases. So, University of California–Riverside Bourns College of Engineering researchers examined the stability of graphene oxide and its movement in both surface and groundwater. 

The researchers found that graphene oxide nanoparticles are very mobile in lakes or streams and are likely to harm the environment, according to a university news release.  

The nanoparticles’ behavior differed significantly in groundwater versus surface water. Because of groundwater’s higher degree of hardness and lower concentration of natural organic matter, graphene oxide nanoparticles tended to become less stable and eventually settle out or be removed in subsurface environments. In surface waters where there is more organic material and less hardness, nanoparticles remained stable and moved farther, especially in subsurface layers of the waterbodies, the news release says. 

 

The research article, “Stability and Transport of Graphene Oxide Nanoparticles in Groundwater and Surface Water,” was published in the journal Environmental Engineering Science.  

 

 

Researchers examine foam management in nutrient removal facilities

 

The classifying selector, a method for foam elimination introduced in 2001, has been confused with other technologies and practices. Brown and Caldwell (Walnut Creek, Calif.) researchers decided to examine the various methods for foam management or elimination in activated sludge facilities. The research article providing this review appears in the June issue of Water Environment Research.  

High residence times and trapping by baffles cause nuisance foam-causing organisms to accumulate in facilities. This occasionally causes effluent with high levels of total suspended solids and leads to digester foaming when wasted.  

The classifying selector, based on sound biological and physical principles, needs no chemicals and minimal operator attention to work. When properly applied, it will prevent nuisance foams in biological nutrient removal facilities. It can be distinguished from other surface foam wasting schemes by maintaining negative selection pressure so nuisance foam-causing organisms are unable to gain a foothold in sufficient numbers. The process uses the propensity of nuisance-causing organisms to attach to bubbles and establish a rising velocity to enrich them in a surface mixed liquor layer, where they are wasted, the article says. However, publications have not adequately described the process, so benefits of foam elimination from classifying sector concepts have not been widely obtained.  

For inherent foam trapping situations, the only solution is surface foam wasting because foam can’t be eliminated. The article addresses potential efficiency gains possible in these situations. 

The authors note that strategies to manage or eliminate foam rely on the designer and facility owner to choose a nutrient removal process and implement its features. They also suggest developing designs with the operator in mind since the type of wasting conducted relies on the operator as he or she works to optimize facility operation. The article, “A Critical Review of Nuisance Foam Formation and Biological Methods for Foam Management or Elimination in Nutrient Removal Facilities,” can be downloaded free at http://goo.gl/ACSTtf

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


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