Abstract
T
Treatment of residual microalgae biomass with anaerobic digestion has the potential to increase the sustainability of microalgae-derived biofuels through production of biogas, recovery of nitrogen and phosphorus, and stabilization of the biomass for disposal. In the first study of its kind, Xiang et al. (2018) demonstrated that the recovery of biogas and nutrients can be highly sensitive to the microalgae speciation and composition. By comparing lipid-extracted Chlorella vulgaris and Cyclotella sp., they found that although the biogas yield was the same between the two species, the biogas production rate and nitrogen and phosphorus recoveries varied greatly. These results demonstrate that the microalgae speciation should be considered when examining nutrient recovery from anaerobic digestion of lipid-extracted microalgae.
Heavy metal contamination poses a significant risk to human health and the environment, with an important example being the leaching of metals from historic mining residuals. Holmes et al. (2018) examined the ability of a novel permeable reactive concrete (PRC) to remove lead, cadmium, and zinc from water. Through bench-scale testing with PRC columns, they demonstrated that precipitation, complexation, and sorption processes within the PRC completely removed the influent metals for 266 days of testing, at which time the metals had not yet been detected in the effluent of the first column. Cost estimates for application of PRC were shown to be 1/6th–1/12th of the cost of comparable technologies, demonstrating that PRCs could greatly enhance the economics for remediation of heavy-metal contaminated water.
Flame retardants (FRs) are chemicals added to foams and plastics in consumer products, such as electronic equipment and furniture, to comply with flammability standards. Research over the past decades has demonstrated that halogenated FRs are associated with adverse health effects, such as endocrine disruption, immunotoxicity, reproductive toxicity, impaired fetal/child development, and cancer. Although many toxic FRs have been replaced by other FRs, existing products containing toxic FRs will remain in service for decades. In a two-part series, Lucas et al. (2018a, 2018b) review issues and best practices associated with the use and responsible disposal of wastes containing FRs and they identify basic and applied research needs.
There are several available methods to quantify the leaching of heavy metals from coal ash, including the U.S. Environmental Protection Agency's Toxicity Characteristic Leaching Protocol, which is conducted at a single pH, the Leaching Environmental Assessment Framework, which is conducted over a pH range with different liquid-to-solid ratios, and focused studies that attempt to mimic the local conditions found in coal ash impoundments. Schwartz et al. (2018) examined the ability of these protocols to roughly group the leachability of coal ash with respect to arsenic and selenium. They found that the methods showed promise in categorizing high- and low-leaching potential ash materials. They also demonstrated that the quantity of leached contaminant varied widely across the tests, indicating that the on-site geochemical conditions play a critical role in arsenic and selenium mobilization from coal ash.
A recent national survey examined the education of undergraduate and graduate students on ethical and societal issues (ESI). In this survey, 158 environmental engineering instructors responded, representing 114 institutions. Although 97% of the respondents taught ESI in their courses, only 30% felt that their program adequately teaches ESI to undergraduate students and only 20% felt this way for graduate students. Bielefeldt et al. (2018) discuss these data and provide results on the topics that instructors integrate ESI into their courses, with the goal of inspiring others to develop and integrate ESI-related topics into their courses.
There is strong representation of environmental engineering and science within the 14 Grand Challenges for Engineering proposed by the National Academy of Engineering. These challenges include the development of affordable and clean energy, management of the nitrogen cycle, and provision of clean water and sanitation. Blaney et al. (2018) provide an additional Grand Challenge for the environmental engineering community, asking us to look inward and focus on improving diversity. They provide and discuss data on the status of diversity within environmental engineering faculty and students and they make the case for including diversity as a critical component for enabling transformative solutions to the grand challenges in environmental engineering.