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 April 2020 issue through the July 2020 issue of EES. Congratulations to all whose work is highlighted.
Radionuclides and toxic metals exist widely in produced water from oil and gas industries and wastewater in many legacy waste sites. Coprecipitation is an effective approach to remove radionuclides and toxic metals at concentrations that could be significantly lower than their solubility limits. In a study focused on coprecipitation of strontium (Sr) with barite (BaSO4), Hunter et al. (2020) used X-ray fluorescence (XRF) nanospectroscopy at the Hard X-ray Nanoprobe (HXN) beamline of the National Synchrotron Light Source II to quantify Sr incorporation into barite. The results showed the amount of incorporated Sr was far larger than thermodynamic models predict, suggesting the formation of metastable solid solutions. Increasing the barite supersaturation index to over ∼3 led to a significant increase of Sr incorporation. A review of the thermodynamics on the equilibrium in solid solution and aqueous solution systems was presented and used as a framework to understand the kinetic control of the coprecipitation process. The insights obtained from the research could help develop approaches for stabilizing radionuclides and toxic metals in various waste streams.
Aerobic granular sludge (AGS) reactors have been increasingly explored to treat organic contaminants because the granules can better withstand fluctuation of wastewater composition and be more easily settled for biomass separation. For wastewater with high salinity, however, it is challenging to grow and maintain the microbial granules for organic degradation. Ibrahim et al. (2020) evaluated the performance of an AGS reactor inoculated with an enriched halophilic culture in comparison with that seeded with activated sludge at salt concentrations ranging from <1 to 85 g NaCl per liter. The results showed that the halophile-inoculated reactor could better retain the granule structure at hypersaline conditions (>40 g NaCl per liter) and produced significantly higher amounts of total extracellular polymeric substances and alginate-like exopolysaccharides. The microbial population of both reactors converged toward halophile-dominated systems at hypersaline conditions. Adding halophilic organisms in the initial inoculum is, therefore, advantageous for treating hypersaline wastewater because of the production of better granules.
Gutierrez et al. (2020) conducted a comprehensive evaluation of phosphorus recovery potential from municipal wastewater solids. Different phosphorus species in biosolids, operationally defined as orthophosphate, condensed polyphosphate, and organic phosphate, were separated and quantified from 11 wastewater treatment plant solids. These results were then used to estimate the phosphorus recovery potential by comparison with the known performance of three established technologies (AIRPREX™, Stuttgart Process, and KREPRO) for phosphorus recovery. The study provides guidance on how to select proper technologies for phosphorus recovery, based on the type of wastewater treatment process and determined phosphorus speciation
Although granular activated carbon (GAC) has long been used for removal of organic micropollutants such as pesticides and pharmaceuticals from water, the treatment cost may still be prohibitively high for regions with limited resources. Kearns et al. (2020) investigated the use of biochar as a low-cost alternative for removal of micropollutants in comparison with GAC, with a particular emphasis on modeling the contaminant breakthrough data and developing a scale-up procedure to predict the contaminant adsorption under the influence of background dissolved organic matter. This comprehensive study provides a user-oriented conservative approach to predicting full-scale micropollutant breakthroughs that is critical to the design and operation of biochar and GAC treatment systems.