Emerging Contaminants Summit

Spring 2020

delongSusan De Long
Assistant Professor
Colorado State University

Dr. Susan De Long is an Assistant Professor in the Department of Civil and Environmental Engineering at Colorado State University. She holds Bachelor’s degrees in Environmental Science and Molecular and Cell Biology from the University of California, Berkeley and earned her M.S. and Ph.D. in Environmental Engineering from The University of Texas, Austin.

She has over 15 years of experience working in the fields of environmental engineering, microbiology and applied molecular biology.

Her research is focused on developing environmentally sustainable biotechnologies. On-going work is advancing technologies for biodegradation of emerging contaminants, water reuse, site bioremediation, and bioenergy generation from waste materials. Dr. De Long’s research group develops and applies molecular biology tools to investigate microbial communities involved in successful treatment processes and leverages this knowledge to improve treatment process design. Additionally, Dr. De Long’s group is applying meta-omics tools to discover genes and enzymes involved in degradation of recalcitrant pollutants; this knowledge will support development of molecular biology assays to track key microbes in natural or engineered systems to guide development of the next generation of treatment technologies.



Impact of Inoculum Sources and Primary Carbon Sources on Removal of Pharmaceuticals and Personal Care Products in Biotreatment Systems

Pharmaceuticals and personal care products (PPCPs) are contaminants of growing concern for the water and wastewater treatment industries, particularly given the increasing number of potable reuse projects. Available physical and chemical treatment technologies are costly, energy intensive, produce potentially toxic byproducts and problematic waste streams, or are ineffective for some compounds. Biological PPCP treatment technologies, including biofiltration and soil aquifer treatment (SAT), are promising lower cost, lower energy use technologies. Many PPCPs are biodegradable, but reported removal efficiencies vary widely and often appear contradictory (e.g., both complete recalcitrance and rapid biodegradation are reported for the same compound in differing studies). Knowledge is lacking regarding how to optimize and manage microbial communities in biological PPCP treatment technologies to achieve efficient and stable PPCP removal. We investigated two critical parameters: (1) the source of microbial inoculum, and (2) the primary carbon source provided. Our approach involved operation of batch biofilm reactors (containing sand as a medium for biofilm growth) and monitoring of PPCP removals and microbial communities. Inocula pre-acclimated to model PPCPs were derived from activated sludge (AS), ditch sediment historically-impacted by wastewater treatment plant effluent (Sd), and material from laboratory-scale soil aquifer treatment (SAT) columns. Six primary carbon sources were tested: casamino acids, humic acid and peptone mixtures (40:60 and 60:40), molasses, organic acid mixture (including citric acid, lactic acid, and succinic acid), and phenol. Six PPCPs (diclofenac, 5-fluorouracil, gabapentin, gemfibrozil, ibuprofen, and triclosan) were monitored using gas chromatography coupled with mass spectrometry. Microbial communities were tracked over time using next-generation sequencing of the 16S rRNA gene. PPCP removals were superior for AS- and Sd-derived inocula compared to the SAT-derived inocula despite comparable biomass. Removal patterns differed among the 6 model compounds examined indicating differences in biotransformation mechanisms. Of the primary carbon sources tested, organic acids, casamino acids and phenol appeared the most promising; however, on a biomass normalized basis, humic acid and peptone mixtures were also effective. Thus, for technologies with short hydraulic residence times (biofilters) the former carbon sources should be considered, while for technologies with longer residence times (e.g., SAT), humic acids and peptone mixtures could potentially be added to biostimulate microbial communities in situ. Microbial phylotypes linked with successful biodegradation included: Bacteroidetes, Beijerinckia, Cytophagaceae, Methlyophilus, Methlyovorus, Myxococcales, Planctomycetales, and Sphinogomon


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