AEESP Spotlight: Late 2023

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 three times per year in the journal 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 a select article from the April through July 2023 issues of EES. Congratulations to those whose work is highlighted.

Many readers of this Spotlight will recognize a conventional train of processes for wastewater treatment: primary sedimentation, activated sludge including secondary sedimentation, filtration, and disinfection. Settled solids are often sent to an anaerobic digester (AD) for stabilization and volume reduction, along with biogas production. A goal of many recent research efforts is to improve the AD process to generate the most biogas possible while minimizing the mass of sludge sent offsite. A thermal hydrolysis process (THP) is one promising approach to achieve those goals.

Armstrong et al. (2023) used sludge from a full-scale wastewater treatment plant to investigate whether the THP process had any effects on endocrine disrupting compounds (EDCs) in the sludge. EDCs are important because they are often found in wastewater and concerns about the health and environmental impacts of these compounds have gained the attention of regulatory agencies in many countries. One idea is that the THP process may cause greater destruction of EDCs, since they are exposed to higher temperatures and pressures. But another possibility is that greater release of EDCs may be caused as they are liberated from their adsorbed state during thermal hydrolysis.

Armstrong et al. (2023) found that some EDC concentrations increased, while others decreased, which points to a mechanistically complex set of interactions in the overall THP-AD treatment train. In an attempt to shed light on the microbial contribution to those mechanisms, bioinformatics was used to evaluate the anaerobic microbiome community structure in the various samples. While THP clearly affected the abundance of microbes in its effluent, there was no clearly discernible effect on the community structure in the downstream AD step. This suggests that the behavior of EDC removal or release was tied to other (perhaps physicochemical) mechanisms. Readers are encouraged to learn more by downloading the article from the June 2023 issue of EES.

Overall, this study serves as an example of the way chemical analysis and microbial analysis can be coupled to better understand chemical fate and transport in engineered treatment systems. This is especially important for new processes where the behavior has not been previously explored and is difficult to predict.