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 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 December 2020 through March 2021 issues of EES. Congratulations to all whose work is highlighted.
The highlighted articles in this spotlight edition each discusses global challenges (National Academies of Sciences, Engineering, and Medicine, 2019) that environmental engineers and scientists will continue to work to solve in the coming decades. As discussed by Deng et al. (2021), the sustainable use of Earth's natural resources is essential to addressing the challenges of supplying water and energy to the world's population of almost eight billion people. Reactive transport modeling, which is highlighted in the March special issue, is a powerful tool that can aid in addressing these challenges. Removing antibiotic resistant genes (ARGs) from wastewater treatment plant (WWTP) effluent is essential if we are to meet the challenge of creating healthy cities. Also, important to creating healthy cities is assessing the impact of catastrophic nuclear accidents on public health and then mitigating those impacts. Finally, part of the challenge of adapting to the impacts of climate change can be tackled by improving our understanding of the influence of nutrients on hazardous algae blooms.
As discussed by Gonzalez-Estrella et al. (2021), the release of hydrocarbons from cement fractures of wellbores used for oil and gas industry can result in the release of greenhouse gases, including carbon dioxide (CO2) and methane, into the atmosphere. This study used reactive transport modeling along with bench experiments to investigate the effects of reactive saline brine water at circumneutral pH with fractured wellbore cement. Calcite was found to precipitate along the flow path, decreasing the transport of fluid through the damaged wellbore system. The results suggest that leakage of hydrocarbons into the environment can be mitigated by the injection of saline brine supersaturated with respect to calcium carbonate.
Renewable energy sources, such as wind and solar power, are essential to a sustainable future and maintaining CO2 levels <450 ppm. As solar and wind power are intermittent, there is growing interest in methods to store energy. One promising method is compressed energy storage, where a cushion gas, for example, CO2, is injected into saline aquifers during times of low energy consumption and extracted during times of high demand. However, the potential interactions between CO2 and saline groundwater and their effects on operation are unknown. Iloejesi and Beckingham (2021) used reactive transport simulations to evaluate these interactions and the functionality of using CO2 as a cushion gas in a porous formation. They found that injected CO2 can result in the dissolution of carbonate and aluminosilicate minerals; however, the extent of dissolution decreased after the first injection. The results suggest that storage volume and injectivity will remain relatively constant after the first cycle, making the utilization of cushion gases, including CO2, a viable means of energy storage.
In addition to renewable energy sources, nuclear power is seen as essential to maintaining CO2 levels <450 ppm and part of a sustainable energy future (World Nuclear Association, 2021). However, the catastrophic damage of the Fukushima Dai-Ichi Nuclear Power Plant in 2011 and the Chernobyl Power Plant in 1986 demonstrated the transcontinental transport of the released radioactive isotopes and the global impact of these accidents. As numerous events of the 2021 Summer Olympic Games will be held in the Fukushima Prefecture, there is concern that visitors and athletes may be exposed to radioactive contaminants emanating from the Fukushima Dai-Ichi site. In this study (Kaltofen et al., 2021), soil and dust samples were collected from sites in the Fukushima Prefecture, Greater Tokyo, and in areas between these sites. Alpha and beta activities were not correlated. Radioactivity at Olympic venues in Greater Tokyo was similar to those in the control set from the United States. The beta activity in the sample set from northern Japan was seven times greater than that in the samples from Tokyo Olympic venues, demonstrating the relative success of remediation activities at the Olympic/Paralympic venues as compared with elsewhere in Japan. Data from the Fukushima Prefecture demonstrate the need for continuing assessment and perhaps additional remediation work.
Climate change is predicted to increase water temperature and favor the growth of cyanobacteria in both marine and freshwaters, increasing the frequency, severity, and geographical distribution of harmful algal blooms (HABs). Chujo et al. (2021) developed a novel competitive growth model for Microcystis sp. and Cyclotella meneghiniana, two organisms that proliferate during HABs. The growth model, which was based on the Droop and Lotka-Volterra models, incorporated nitrogen and phosphorus as functional parameters. The results of a monoxenic culture experiment revealed that the initial nitrogen and phosphorus conditions determined which nutrient was critical to Microcystis growth. At nitrogen to phosphorus (N:P) mass ratios >11, phosphorus limited cyanobacterial growth, whereas at N:P mass ratios <11, nitrogen was the critical nutrient.
The presence of ARGs in WWTP effluent is of significant concern globally due to the potential for this resistance to reduce the efficacy of antibiotics, which are commonly used to treat infectious diseases. The efficacy of disinfection processes toward ARGs is limited and ARGs have been shown to persist in the environment. Chen et al. (2020) determined the efficiency of electrocoagulation (EC) for the removal of selected ARGs (sul1, sul2, tetO, and tetX) from WWTP effluent. EC achieved 1.5–2.6 log removal of the target ARGs with an electrolysis time of 60 min under a current density of 20.0 mA/cm2 at neutral pH. Pretreatment of the effluent with conventional ultraviolet (UV) disinfection improved the efficacy of EC. The proposed mechanism of removal of ARGs was the adsorption and enmeshment of the precipitated flocs generated by EC.