July 2011, Vol. 23, No.7

Research Notes

Spraying distillation wastewater increases essential oil yield

To increase essential oil production from peppermint and spearmint plants, spray them with the wastewater created from extracting essential oils from other plants.

Mint essential oils are used in the production of gum, toothpaste, pharmaceuticals, sweet foods, and aromatherapy products. These oils can be extracted by steam distillation, a process that produces wastewater that is often released into waterways. Now, researchers are searching for new ways to beneficially use those byproducts, according to a news release from the American Society for Horticultural Science (Alexandria, Va.). 

Professor Valtcho D. Zheljazkov wrote a study testing the application of plant hormones and distillation wastewater on peppermint and spearmint plants. Zheljazkov and colleagues evaluated the effects of methyl jasmonate, gibberellic acid, and salicylic acid at three concentrations, as well as the residual distillation water from 15 plant species applied as foliar sprays on mint plants. The team evaluated the resulting biomass yields, essential oil content, and essential oil yield of the plants, the news release says.

 Biomass yields for both species increased from application of salicylic acid at 1000 mg/L. Essential oil content of peppermint increased from the application of distillation water of seven plant species, and the application of methyl jasmonate at 100 and 1000 mg/L, gibberellic acid at 10 mg/L, and salicylic acid at 10 and 100 mg/L. Essential oil content of spearmint was increased only by the application of distillation water of one plant species, the news release says.

The findings, reported in HortScience, present a new method for improving yield and essential oil content in mint crops. This finding could provide economic and environmental benefits for production. Zheljazkov explains that further research is needed to verify and further explore the effects identified in his research, the news release says.


Revealing design and operation of the trickling filter system in May WER

Engineers from CH2M Hill (Englewood, Colo.) describe trickling filters in the May issue of Water Environment Research (WER), the Water Environment Federation (Alexandria, Va.) research journal.

The article is titled “Trickling Filter and Trickling Filter-Suspended Growth Process Design and Operation: A State-of-the-Art Review.” It describes the mechanics, design criteria, benefits compared to activated sludge, and operational practices of trickling filter systems. The article also examines the design and operation of the combined trickling filter--–suspended growth process.

The trickling filter is a three-phase wastewater treatment system with fixed biofilm carriers, the article says. The article attempts to describe the selection and design of process components because information on the topic has not been documented well, and available information is fragmented, the article says.

The full article can be downloaded free at http://goo.gl/DEaHs.


Water Environment Research allows open access to one article per issue on a range of important technical issues such as nutrient removal, stormwater, and biosolids recycling. Find more at www.ingentaconnect.com/content/wef/wer.




Researchers on the hunt for bacteria in waterways

Waterways infected with pathogenic Escherichia coli and salmonella bacteria are the target of U.S. Department of Agriculture (USDA) scientists. The scientists have developed a way to detect the harmful microorganisms at lower levels than any other previous method. This is the first attempt by USDA’s Agricultural Resource Service (ARS) at testing for E. coli in waterways, according to an ARS news release.

Health officials usually test for salmonella and E. coli 0157:H7 using two types of nonpathogenic indicator bacteria, Enterococci and generic E. coli. While the indicators often are detected in affected waterways, their presence doesn’t guarantee the presence of either pathogen, according to ARS microbiologist Michael Jenkins.

The indicator organisms often are reliable, but sometimes fail to detect bacteria in pathogen-free waters because it is difficult to detect pathogens in low levels. Just 100 cells of salmonella and just 10 of 100 cells of E. coli 0157:H7 can cause illness, the news release says.

ARS researchers combined methods previously developed to assess water quality and detect pathogens in laboratory settings, the news release says. They collected water samples from a Watkinsville, Ga., pond; ran them through a centrifuge to separate the filtered contents into pellet form; used the suspended pellets to develop cell cultures; confirmed the identity of the bacteria with a genetic method; and determined the concentration found in the original samples.

The results showed that the process is able to detect as little as a few cells of pathogenic E. coli and salmonella in a 10-L water sample.



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