"We have found something that is not necessarily a surprise but has important implications. These are considerations that water quality professionals should take into account if they have switched or are considering switching to a monochloramine disinfection system," says Dan Kroll, Chief Scientist at Hach Homeland Security in Loveland, Colorado, and lead researcher on the study, presented today at the ASM Biodefense and Emerging Disease Research Meeting.
As part of a recent endeavor to develop a system for online, continuous monitoring of drinking water distribution networks, Kroll and his colleagues, in coordination with the Army Corps of Engineers, studied the interactions of a wide variety of potential waterborne threat agents (both biological and chemical) with different levels of either free chlorine or monochloramine present. They tested dozens of potential hazards, from pesticides to disease-causing bacteria to chemical warfare agents.
The researchers discovered that not only is monochloramine less reactive than free chlorine against a number of chemical threats, it also is a slightly less efficient disinfectant, requiring a longer time to kill bacterial contaminants.
Scientists have long known that monochloramine is a more stable compound, and that is part of the reason it is becoming more popular as an alternative to chlorine in municipal water systems. Free chlorine has traditionally been the disinfectant of choice for municipal water systems throughout the 20th century, but it has some drawbacks. It can react with organic materials in drinking water to produce chlorine by-products. Some of these by-products are considered carcinogenic and their levels in drinking water are regulated by the U.S. Environmental Protection Agency.
But Kroll and his colleagues have confirmed in their study that the stability of the monochloramine may have its drawbacks as well. Treatment with free chlorine, because it is more reactive, can lead to rapid degradation of chemical threats as well as early detection of contamination. As it reacts with a contaminant, chlorine levels in the water drop. Many municipalities use chlorine levels as indicators of possible contamination.
Monochloramine also requires more time to kill microbial contaminants in water. This should not be an issue in treatment plants, as water in monochloramine facilities can be held longer. "In the event of contamination of the water supply after it leaves the treatment plant, though, monochloramine has the potential as being not as effective as chlorine, since there is little control over the contact time," says Kroll.
Kroll is not recommending that system that have already switched to monochloramine switch back. Instead, he wants water quality professionals to recognize that if they have a monochloramine system, they can no longer rely solely on a sudden drop in disinfectant levels to alert them to a potential contaminant. He also recommends that, where possible, some level of free chlorine should be kept in the system.
And if a municipality has a free chlorine-based system, provides water to a high-profile target such as a military base, and are considering the switch to monochloramine, they may want to consider other methods of controlling disinfection byproducts to help comply with EPA regulations.
"The findings in these studies have significant repercussions as to the safety and security of our nations water supplies," says Kroll.
Jim Sliwa | EurekAlert!
What the world's tiniest 'monster truck' reveals
23.08.2017 | American Chemical Society
Treating arthritis with algae
23.08.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
23.08.2017 | Materials Sciences
23.08.2017 | Automotive Engineering
23.08.2017 | Life Sciences