Five devices pitched as alternatives to chemical water treatment for water-based air-conditioning systems allowed the same rate of bacterial growth as untreated water, Pitt researchers found in two-year study.
Nonchemical treatment systems are touted as environmentally conscious stand-ins for such chemicals as chlorine when it comes to cleaning the water-based air-conditioning systems found in many large buildings. But a recent study by University of Pittsburgh researchers suggests that this diverse class of water-treatment devices may be ineffective and can allow dangerous bacteria to flourish in the cooling systems of hospitals, commercial offices, and other water-cooled buildings almost as much as they do in untreated water.
The two-year study by a team in Pitt’s Swanson School of Engineering is the first to thoroughly investigate the ability of nonchemical treatment devices (NCDs) to control the growth of bacteria in water-based cooling systems. Of the five NCDs tested, none significantly prevented bacterial growth. On the other hand, the researchers found that standard chlorine treatment controlled these organisms, even after bacteria had been allowed to proliferate.
“Our results suggest that equipment operators, building owners, and engineers should monitor systems that rely on NCDs to control microorganisms,” said coinvestigator Janet Stout, a research associate in the Swanson School’s Department of Civil and Environmental Engineering and director of the Pittsburgh-based Special Pathogens Laboratory. Stout worked with fellow lead investigator Radisav Vidic, chair and William Kepler Whiteford Professor of civil and environmental engineering, and Pitt civil engineering graduate student Scott Duda.
“These cooling systems are energy efficient and, if properly treated, very safe,” Stout continued. “But based on our results, nonchemical devices alone may not be enough to control microbial growth. One possible measure is to add chemical treatment as needed to prevent a potential health hazard.”
The air systems the team investigated work by piping chilled water throughout a building. The water warms as it exchanges temperature with the surrounding air and becomes a hotbed of microorganisms before returning to a central cooling tower to be cleaned and re-chilled.
If the returning water is not thoroughly cleaned, bacteria can spread throughout the system, exposing people within the building to possible infection and hampering the system’s energy efficiency.
The team constructed two scale models of typical cooling towers. One model remained untreated while the other was treated with five commercially available NCDs installed according to the manufacturers’ guidelines. Each device was tested for four weeks. Chlorine was administered three times during the study to demonstrate that an industry-accepted chemical treatment could kill bacteria even in a heavily contaminated system.
The five devices tested represent different classes of NCDs, Vidic said. Pulsed electric-field devices emit electromagnetic energy that, in theory, ruptures bacterial membranes and activates particles that ensnare the bacterium. Electrostatic devices function similarly by producing a constant static field.
Ultrasonic devices pass a mixture of untreated water and high-pressure air through a chamber that purportedly disintegrates the bacterium with sound waves.
For hydrodynamic cavitation devices, two cone-shaped water streams collide to form a vacuum region filled with high-friction bubbles that collide with and presumably deactivate the bacteria. Finally, the team tested a magnetic device, although magnetic NCDs are intended to prevent mineral buildup, not control bacterial growth.
The study was funded by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers.University Units
Morgan Kelly | EurekAlert!
Multi-year study finds 'hotspots' of ammonia over world's major agricultural areas
17.03.2017 | University of Maryland
Diabetes Drug May Improve Bone Fat-induced Defects of Fracture Healing
17.03.2017 | Deutsches Institut für Ernährungsforschung Potsdam-Rehbrücke
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
22.03.2017 | Materials Sciences
22.03.2017 | Physics and Astronomy
22.03.2017 | Materials Sciences