July 2009, Vol. 21, No.7

Research Notes

Scientists Study Safety of Reclaimed Water

U.S. Agricultural Research Service (ARS) scientists Jean McLain and Clinton Williams are studying the effects of irrigating with reclaimed water. The preliminary results of their research suggest that using reclaimed water for irrigation in arid regions is both safe and effective, an ARS news release says.

Since September 2006, the researchers have collected soil and water samples from a municipal park irrigated with reclaimed water. They tested the samples for Escherichia coli and found no strands of the pathogen, the news release says.

Williams also tested for carbmazepine, a drug used to treat seizures from epilepsy that has been detected in trace amounts in the drinking water. The study found that natural organic matter in the soil can prevent the drug from leaching beyond the root zone, the release says.

A slight increase in soil salinity was identified from the sampling, but it was determined not to be enough to harm plant growth, the release says. In addition, one of the researchers’ studies has established that the quality of reclaimed water is harder to assess in winter, with approximately 90% false positives for E. coli in the samples collected in December and January. Chemical analysis revealed that the water’s salt content increased in winter, suggesting that the false positives could be related to salt chemistry, the release says. The researchers are collaborating with scientists at the University of Arizona (Tucson) to confirm this hypothesis.

The study calls for additional research to determine if all soil types interact the same way and if the soil can be broken down by natural soil microorganisms. 

Read more in the January issue of Agricultural Research magazine at www.ars.usda.gov/is/AR/archive/jan09/water0109.htm.

Robotic Fish Will Monitor Pollution in Spain

Robotic fish built to mimic fish movements and resemble carp will be released in the port of Gijon in northern Spain as part of a 3-year research project to detect pollution. For the project, funded by the European Commission and coordinated by BMT Group Ltd. (Teddington, England), the fish are scheduled to be released in the port in approximately 2 years, according to BMT Group research scientist Luke Speller. 

The robotic fish are being built by scientists in the School of Computer Science and Electronic Engineering at the University of Essex (England). Each fish costs about $29,700 (£20,000) to make, according to Speller.

The fish measure 1.5 m long and swim at a maximum speed of approximately 1 m/s. “Instead of the conventional rotary propeller used in ship or underwater vehicles, a robotic fish relies on the undulation tail movement,” according to a University of Essex research report authored by Jindong Liu, Ian Dukes, and Huosheng Hu. The report adds that “this kind of propulsion is less noisy, more effective, and maneuverable than the propeller-based propulsion.”

“If successful, the team hopes that the fish will be used in rivers, lakes, and seas across the world … to detect pollution,” according to a BMT news release. The fish will be equipped with chemical sensors to find the source of pollutants both on the surface and dissolved in the water, such as leaks from vessels or underwater pipes, the news release says.

Tyndall Institute (Cork, Ireland) will develop the chemical sensors to detect pollutants, and Thales Group (Neuilly-sur-Seine, France) is developing ultrasonic communication so the fish can share information and react to the environment to look for and identify the type and source of pollution, Speller said. This allows for real-time monitoring and sampling.

The battery-powered fish are also equipped with sonar to help them avoid obstacles. Each fish must be within 0.62 mi (1 km) of another fish to relay information, Speller said. Information gathered will be transmitted to the port’s control center, the news release says. When the approximately 8 hours of battery life become low, the fish will return automatically to the control center to recharge, the news release says.

The fish will start by monitoring nitrates, phosphates, and petrochemicals, and the technology can be modified and expanded to monitor additional or different pollutants in the future, Speller added.

©2009 Water Environment Federation. All rights reserved.