Abstract
The “spotlight” column draws attention to selected articles in Environmental Engineering Science (EES), the official journal of the Association of Environmental Engineering and Science Professors (AEESP). Spotlight articles appear three times per year in the journal as well as in the AEESP newsletter. Through the publication of high-quality peer-reviewed research, the EES journal helps AEESP achieve its mission of developing and disseminating knowledge in environmental engineering and science. In this entry we shine the spotlight on selected articles from the April 2022 through July 2022 issues of EES. Congratulations to all whose work is highlighted.
Microplastics and disinfection by-products are constantly on the minds of drinking water professionals. More to the point, they are on the minds of consumers as public awareness rapidly expands; however, this attention and awareness has largely been restricted to the water that comes from our taps, not to what we consume in the form of bottled water. That is until now! Parveen et al (2022) quantified the concentrations of both microplastics and various types of trihalomethanes, which are disinfection by-products, in bottled water samples. Interestingly it was determined that at least one type of trihalomethanes was detected in all 44 bottled waters, from 18 unique brands that were sampled. Of these samples, four types (chloroform, bromodichloromethane, dibromochloromethane, and bromoform) of trihalomethanes were detected in 20 samples. These results were particularly surprising given that the bottled waters had not undergone chlorination, raising important questions about how trihalomethanes may enter bottled water sources. Similarly, the researchers detected microplastics in all of the tested bottled waters, with concentrations ranging from ∼500 to 1000 nanograms per liter (ng/L). These colloidal plastics were determined to be polypropylene or polyethylene terephthalate. Considering the general perception of the quality of bottled water compared with that of tap water, this study may represent a watershed moment that leads to a re-evaluation of the methods used in bottled water production.
Speaking of water quality, who among us has not had the pleasure of suffering from a broken hot water heater or from the accumulation of mineral scale in our faucets? Neither are pleasurable experiences, particularly when it results in cold showers for a family that includes children! Beyond considering installation of a home water softener how deeply have such water quality-related events provoked you to think of how the water quality that comes into your household, and your own water usage, affects your overall plumbing system? Even more interesting is how these, and other, variables determine the characteristics of microbial populations in our pipes. Luckily for the environmental engineering community and other stakeholders, a study recently published by Tolofari et al (2022) provides insightful information on this topic. These researchers specifically examined how the chlorine type, water residence time within the plumbing system, and water heater temperature affected the presence of microbes (heterotrophic bacteria and nontuberculous mycobacteria) in water heaters and associated plumbing networks. It was observed that systems employing free chlorine as the primary disinfectant experienced no microbial growth, or presence, in the water heater reservoirs. Conversely, when chloramines were the disinfectant microbial growth was a function of water usage and water heater temperature. In this study, higher usage and water temperature resulted in depressed bacterial counts in both the heater reservoir and the plumbing network. These findings shed new light on how disinfectant selection and usage patterns can affect the quality of the water we consume and the overall “health” of our home plumbing systems. This valuable information will hopefully serve as a springboard for other investigations, by these and other researchers, for developing ways to better manage our water resources within our households.
Staying on the exciting and highly relevant topic of disinfection and keeping our households safe from determined microbes, the development of point-of-use disinfection processes has long been sought. Nevertheless, not much progress has been made, at least in our humble opinion, since the advent of the iodine tablet and a myriad number of filtration devices. Although it should be noted that we would hardly complain of such things when stuck in the back country with only a small stream serving as our drinking water source! Anyone who has experienced the scourge of a waterborne pathogen of any type knows full well the importance of disinfection. Advancing the development of point-of-use disinfection systems that incorporate ultraviolet (UV) light was described in a recent article authored by Nguyen et al (2022). They described the inactivation of bacteriophage MS2 and Escherichia coli after having passed through a custom-designed microscale UV reactor. The authors reported inactivation rates of 7 log/mL (8 sec exposure time) and 7.5 log/mL (8 min exposure time) for E. coli and MS2, respectively. Both inactivation values were impressive and meet or surpass U.S. Environmental Protection Agency (EPA) standards. These findings and the developed technology represent an important step in achieving the overall goal of water treatment professionals to diversify our ability to disinfect water at multiple scales.