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 regularly in the journal as an Editor's Note, as well as in the AEESP newsletter. Through 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 August 2020 through November 2020 issues of EES. Congratulations to all whose study is highlighted.
The highlighted articles in this spotlight edition each discuss unconventional means to deal with problems that the environmental engineering and science community are trying to tackle. Perhaps the most unconventional method explored is the use of magnetic fields in water and wastewater treatment. There exists a wide variety of unit processes to treat drinking water and wastewater, but no conventional processes use magnetic fields to impart changes in water chemistry. Wu and Brant (2020) put forward some new ideas about how magnetic fields might be harnessed to improve the efficiency and sustainability of water treatment. They show that flow through a magnetic field alters the hydrogen bond characteristics of water molecules and can even directly affect the pH. The measured bulk electrical conductivity is altered, and that depends on the velocity of water flowing through the magnetic field. Wu and Brant's (2020) study could be applied in processes where coagulation or mineral precipitation occur, among other possibilities. Employing magnetic fields could help reduce our reliance on chemical addition in water and wastewater treatment.
Although stannous chloride is not on the radar of many environmental engineers, it has been approved for use in water treatment, mostly as a corrosion inhibitor. Nguyen et al. (2020) explore stannous chloride for its ability to reduce chromium(VI) to chromium(III) as part of a drinking water treatment train. They find that stannous chloride is effective at 3.5 times the stoichiometric dose when applied to Arizona groundwater. Background oxyanions such as arsenic and tungsten competed with chromium in the reaction, which is important for future process design. The team also reported some practical considerations, such as a reduced effectiveness of stannous chloride when it was exposed to air during storage. This article provides needed information for water treatment practitioners who are weighing various options for treating drinking water sources containing chromium.
Although granular activated carbon (GAC) is a well-known unit process, its performance for microcystin-LR (MLR) removal is less well known. Recent increases in algal blooms are motivating operators of water treatment plants with existing GAC processes to project whether their units can tackle MLR. Villars et al. (2020) provide just such data to determine how different types of GAC behave under various matrix conditions. They used rapid small-scale column tests and found that a hardwood- and lignite-coal-based GAC removed MLR better than bituminous-coal-based GAC, which contained a lower mesopore volume. The conclusion for practitioners is that GAC can be effective for MLR removal and this new study should help practitioners choose a material that will give the longest service time before regeneration is needed.
Aluthgun Hewage et al. (2020) reports on the unconventional use of a combination of ultrasound and ozone nanobubbles for organic pollution remediation in sediments. Thus, polycyclic aromatic hydrocarbons (PAHs), for example, can become remediated in New Jersey's Lower Passaic River superfund site. The ultrasound and ozone nanobubbles approach is a one–two punch: ultrasound provides mechanical energy to desorb contaminants from the sediments and ozone oxidizes the desorbed contaminants. That second punch is especially effective because the nanobubble configuration enhances the ozone concentration and half-life. Under some conditions the application of ultrasound with ozone nanobubbles achieved about 92% removal of PAH from the sediment. Future study is planned to investigate whether the technique is scalable and cost-effective. If so, this may be added to the toolbox of options for sediment remediation, which is needed for many sites in the United States and around the world.