Abstract
The “spotlight” column draws attention to selected articles in Environmental Engineering Science, 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 December 2019 issue through the March 2020 issue of EES. Congratulations to all whose work is highlighted.
Management of solid organic wastes is becoming increasingly difficult due to the increasing restrictions on disposal of wastes in landfills, tipping fees, and source separation requirements. Dixon et al. (2019) assessed the use of a high solids anaerobic digestion (HS-AD) method for treating food waste, yard waste, and biosolids individually as well as through codigestion. They found that codigestion of solid organic wastes with biosolids from wastewater treatment plants (WWTPs) provides the highest methane yield. An optimal ratio of substrate to inoculum was reported to be the key parameter for enhancing methane production. Although HS-AD facilities can be a viable option for managing wastes in the United States, the authors suggested a need for further cost-analysis and life-cycle analysis of the large scale HS-AD systems.
Bioremediation is a cost-effective option for remediating petroleum-contaminated soils. Chen et al. (2019) examined an ozonation step for enhancing the feasibility of biodegradation processes designed to treat total petroleum hydrocarbons (TPHs) and the associated total organic carbon. They compared the efficiency of pre- and postozonation steps. They demonstrated that the two-staged process can achieve effectively the regulatory standard of 10,000 mg/kg for TPHs. They suggested that it is important to measure dissolved organic carbon (DOC) along with TPHs to get a deeper insight into the representative dynamics in the integrated process. Overall, this process shows a promise for remediating soils contaminated with petroleum compounds.
Membranes used for water and wastewater treatment are fouled by microorganisms, which reduces the overall performance of membrane technologies. With a goal of developing knowledge needed to design novel cleaning methods, Lishman et al. (2019) studied membrane biofouling in a mesophilic-aerated membrane bioreactor based on a polyvinylidene fluoride microfiltration membrane. They assessed the impacts of both polysaccharide producers and consumers in the microbial community responsible for fouling. They concluded that it is important to characterize the cell growth and associated extracellular polymers in the extramembrane tightly bound biofilm as well as intracore membrane biofilm. This study emphasizes the need to study biofouling on the membrane surface as well as within the membrane.
The evolution of pathogens that resist antibiotic treatments presents as series of human health risks. The aquatic environment represents a reservoir for antibiotic resistance genes (ARGs) and presents an exposure pathway for humans to contact antibiotic-resistant pathogens. Ikuma and Rehmann (2020) developed a novel predictive model that takes into account both intracellular DNA (iDNA) and extracellular DNA (eDNA) to predict the fate and transport of ARGs in receiving waters downstream of WWTPs. The model considers that eDNA contributes to iDNA of ARGs through a horizontal gene transfer process. The predictive model was used to track eDNA and iDNA in the water column as well as in the sediment, taking into account the physical, chemical, and biological processes. The consideration of eDNA fraction of ARGs in WWTP effluent may improve our ability to predict and improve risk assessment of antibiotic resistance in the water environment.
The presence of estrogens in the environment has been linked to potential human health impacts. Maher et al. (2020) studied a sequential treatment process for removing DOC and estrogens simultaneously from water sources. An electrocoagulation (EC) process was used as the first step for removing DOC, followed by an electro-oxidation (EO) process for removing estrogenic compounds. This study used four estrogenic compounds including estrone, 17β-estradiol, estriol, and 17α-ethynylestradiol. First, EC (iron electrodes) was employed to remove humic acid and improve downstream removal of estrogenic compounds while reducing overall energy consumption in EO (boron-doped diamond electrodes). The sequential EC and EO system was found to reduce overall electrical energy per order (EEO) by nearly 50% compared with EO alone for each of the estrogenic compounds. The EEO was also lower than UV photolysis, UV photocatalysis, and ozone alone, respectively. However, it was higher than a photocatalytic reactor membrane and UV/H2O2. Overall, the EC–EO system effectively removed both bulk organic matter and estrogenic compounds.
Mihelcic and Rains (2020) authored an opinion piece on the recent changes to the Clean Water Act (CWA) in a 2020 regulation referred to as the Navigable Waters Protection Rule. This change was jointly mandated by the U.S. Environmental Protection Agency (EPA) and Army Corps of Engineers. Mihelcic and Rains (2020) reviewed the bipartisan history of the CWA and the historic trajectory of how “waters of the United States” are defined to provide legal jurisdiction. They mentioned that the science supported changes to the CWA made in 2015 compared with lack of science that supported the recent changes. The 2015 CWA was based on review of ∼1,200 peer-reviewed articles that served as the basis for a 408-page scientific connectivity report. However, for the 2020 regulation, EPA's Science Advisory Board wrote that EPA did not incorporate the best-available science into the rule making process. Mihelcic and Rains (2020) conclude with a note that EPA and the Corps have ignored their responsibilities, mission, and vision by ignoring established science in their mandates to protect the nation's water.