@article{he_de los reyes_ducoste_2017, title={A critical review of fat, oil, and grease (FOG) in sewer collection systems: Challenges and control}, volume={47}, ISSN={1064-3389 1547-6537}, url={http://dx.doi.org/10.1080/10643389.2017.1382282}, DOI={10.1080/10643389.2017.1382282}, abstractNote={ABSTRACT Fat, oil, and grease (FOG) released into the sewer collection system have resulted in the production of insoluble solids, leading to FOG blockages in sanitary sewer pipes and consequently sanitary sewer overflows (SSOs). FOG-related SSOs continue to be a global challenge for municipalities responsible for maintaining the conveyance of wastewater in sanitary sewer systems. To provide a comprehensive understanding of FOG control in sewers, this paper critically reviews the scientific literature on the FOG deposit formation process, sources of components involved in FOG deposit formation, and solutions to the problems caused by FOG in sewer systems. The implications of these findings were also evaluated to provide support for pretreatment managers responsible for sewer collection system maintenance. Finally, the ongoing challenges in further understanding the FOG deposit formation process, the distribution of the sources of FOG/free fatty acids, the installation and maintenance of grease interceptors (GIs), and the recovery of energy from GI waste and FOG deposits, were also discussed to determine future research directions.}, number={13}, journal={Critical Reviews in Environmental Science and Technology}, publisher={Informa UK Limited}, author={He, Xia and de los Reyes, Francis L., III and Ducoste, Joel J.}, year={2017}, month={Jul}, pages={1191–1217} }
 @article{cubbage_pitt_stone_he_l. de los reyes iii_2017, title={Steam Application to Destroy Foam-Forming Bacteria in Activated Sludge Systems}, volume={143}, ISSN={0733-9372 1943-7870}, url={http://dx.doi.org/10.1061/(ASCE)EE.1943-7870.0001183}, DOI={10.1061/(asce)ee.1943-7870.0001183}, abstractNote={AbstractThe use of steam to destroy filamentous foam-forming bacteria was explored as an alternative foam control measure in activated sludge systems. The effects of combinations of steam pressure ...}, number={5}, journal={Journal of Environmental Engineering}, publisher={American Society of Civil Engineers (ASCE)}, author={Cubbage, Laurissa E. and Pitt, Paul A. and Stone, Alan L. and He, Xia and L. de los Reyes III, Francis}, year={2017}, month={May}, pages={06017001} }
 @article{nguyen_he_reyes_2016, title={Quantifying in situ growth rate of a filamentous bacterial species in activated sludge using rrna:rdna ratio}, volume={363}, ISSN={1574-6968}, url={http://dx.doi.org/10.1093/femsle/fnw255}, DOI={10.1093/femsle/fnw255}, abstractNote={If the in situ growth rate of filamentous bacteria in activated sludge can be quantified, researchers can more accurately assess the effect of operating conditions on the growth of filaments and improve the mathematical modeling of filamentous bulking. We developed a method to quantify the in situ specific growth rate of Sphaerotilus natans (a model filament) in activated sludge using the species-specific 16S rRNA:rDNA ratio. Primers targeting the 16S rRNA of S. natans were designed, and real-time PCR and RT-PCR were used to quantify DNA and RNA levels of S. natans, respectively. A positive linear relationship was found between the rRNA:rDNA ratio (from 440 to 4500) and the specific growth rate of S. natans (from 0.036 to 0.172 h-1) using chemostat experiments. The in situ growth rates of S. natans in activated sludge samples from three water reclamation facilities were quantified, illustrating how the approach can be applied in a complex environment such as activated sludge.}, number={22}, journal={FEMS Microbiology Letters}, publisher={Oxford University Press (OUP)}, author={Nguyen, V. L. and He, X. and Reyes, F. L.}, editor={Kreft, Jan-UlrichEditor}, year={2016}, pages={fnw255} }
 @article{he_so_de los reyes_2016, title={Shifts in microbial communities in bioaugmented grease interceptors removing fat, oil, and grease (FOG)}, volume={100}, ISSN={0175-7598 1432-0614}, url={http://dx.doi.org/10.1007/s00253-016-7398-7}, DOI={10.1007/s00253-016-7398-7}, abstractNote={To understand the effect of daily bioaugmentation in full-scale grease interceptors (GIs), we compared the microbial communities occurring in two full-scale GIs during bioaugmented and non-bioaugmented cycles. The changes in microbial communities were determined using terminal restriction fragment length polymorphism (T-RFLP) and 16S rRNA gene clone library construction. Differences in the microbial community structure between control and bioaugmented cycles were observed in all cases, although the dominant terminal restriction fragments in the biological product were not detected. The addition of bioaugmentation products and changes in the GI microbial ecology were related to differences in GI performance. Understanding the shifts due to bioaugmentation will result in more informed assessments of the benefits of bioadditives on FOG removal in GIs as well as the effects on downstream sewer lines.}, number={16}, journal={Applied Microbiology and Biotechnology}, publisher={Springer Science and Business Media LLC}, author={He, Xia and So, Mark Jason and de los Reyes, Francis L.}, year={2016}, month={Feb}, pages={7025–7035} }
 @article{he_reyes_leming_dean_lappi_ducoste_2013, title={Mechanisms of Fat, Oil and Grease (FOG) deposit formation in sewer lines}, volume={47}, ISSN={["0043-1354"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84879016648&partnerID=MN8TOARS}, DOI={10.1016/j.watres.2013.05.002}, abstractNote={FOG deposits in sewer systems have recently been shown to be metallic salts of fatty acids. However, the fate and transport of FOG deposit reactant constituents and the complex interactions during the FOG deposit formation process are still largely unknown. In this study, batch tests were performed to elucidate the mechanisms of FOG deposit formation that lead to sanitary sewer overflows (SSOs). We report the first formation of FOG deposits on a concrete surface under laboratory conditions that mimic the formation of deposits in sewer systems. Results showed that calcium, the dominant metal in FOG deposits, can be released from concrete surfaces under low pH conditions and contribute to the formation process. Small amounts of additional oil to grease interceptor effluent substantially facilitated the air/water or pipe surface/water interfacial reaction between free fatty acids and calcium to produce surface FOG deposits. Tests of different fatty acids revealed that more viscous FOG deposit solids were formed on concrete surfaces, and concrete corrosion was accelerated, in the presence of unsaturated FFAs versus saturated FFAs. Based on all the data, a comprehensive model was proposed for the mechanisms of FOG deposit formation in sewer systems.}, number={13}, journal={WATER RESEARCH}, publisher={Elsevier BV}, author={He, Xia and Reyes, Francis L., III and Leming, Michael L. and Dean, Lisa O. and Lappi, Simon E. and Ducoste, Joel J.}, year={2013}, month={Sep}, pages={4451–4459} }
 @article{he_osborne_reyes_2012, title={Physico-chemical Characterization of Grease Interceptors with and without Biological Product Addition}, volume={84}, ISSN={["1554-7531"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84863192662&partnerID=MN8TOARS}, DOI={10.2175/106143012x13280358613345}, abstractNote={Hardened and insoluble fat, oil, and grease (FOG) deposits are the primary cause of sewer line blockages leading to sanitary sewer overflows (SSOs). However, there have been very few long‐term assessments of the physico‐chemical characteristics of full‐scale grease interceptors (GIs), the first “line of defense” against FOG buildup in sewer lines. In this study, we assessed the physico‐chemical characteristics of two full‐scale GIs (at a restaurant and a retirement community kitchen) over a one‐year period. Statistically significant differences between bioaugmented and untreated cycles were detected for several chemical and physical properties. The treated cycles had lower BOD and COD at the grease interceptor outlet. While the combined data for all treated cycles did not show lower FOG concentrations in the GI outlet compared to the combined data for all untreated cycles, comparison of specific individual treated and untreated cycles show a positive effect due to the addition of product.}, number={3}, journal={WATER ENVIRONMENT RESEARCH}, publisher={Water Environment Federation}, author={He, Xia and Osborne, Jason and Reyes, Francis L., III}, year={2012}, month={Mar}, pages={195–201} }
 @article{he_iasmin_dean_lappi_ducoste_reyes_2011, title={Evidence for Fat, Oil, and Grease (FOG) Deposit Formation Mechanisms in Sewer Lines}, volume={45}, ISSN={["1520-5851"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79956022597&partnerID=MN8TOARS}, DOI={10.1021/es2001997}, abstractNote={The presence of hardened and insoluble fats, oil, and grease (FOG) deposits in sewer lines is a major cause of line blockages leading to sanitary sewer overflows (SSOs). Despite the central role that FOG deposits play in SSOs, little is known about the mechanisms of FOG deposit formation in sanitary sewers. In this study, FOG deposits were formed under laboratory conditions from the reaction between free fatty acids and calcium chloride. The calcium and fatty acid profile analysis showed that the laboratory-produced FOG deposit displayed similar characteristics to FOG deposits collected from sanitary sewer lines. Results of FTIR analysis showed that the FOG deposits are metallic salts of fatty acid as revealed by comparisons with FOG deposits collected from sewer lines and pure calcium soaps. Based on the data, we propose that the formation of FOG deposits occurs from the aggregation of excess calcium compressing the double layer of free fatty acid micelles and a saponification reaction between aggregated calcium and free fatty acids.}, number={10}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={He, Xia and Iasmin, Mahbuba and Dean, Lisa O. and Lappi, Simon E. and Ducoste, Joel J. and Reyes, Francis L., III}, year={2011}, month={May}, pages={4385–4391} }