REMOVAL AND TRANSFORMATION OF GEMFIBROZIL, A PHARMACEUTICALLY ACTIVE COMPOUND, IN WASTEWATER TREATMENT
Krkosek, Wendy Helen
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Pharmaceutically active compounds (PhACs) have been found in wastewater effluents and receiving waters around the world. As yet there are no jurisdictions that regulate their release, or their impact on receiving water ecosystem health. The issue is complex due to the number of PhACs that exist, the variability in their structure and function, the variability in removal during different wastewater treatment processes, the potential for formation of metabolites and transformation products, and a lack of information on the impacts due to their presence on receiving waters. Gemfibrozil is a lipid regulating drug that is commonly found in wastewater effluents and receiving waters. It has been shown to partially degrade during biological wastewater treatment processes and has also been shown to produce reaction products through reactions with free chlorine. This thesis investigated the removal and transformation of gemfibrozil through several different wastewater treatment processes, namely biological removal and chlorination. Reactions between gemfibrozil and free chlorine led to the identification of four reaction products. The structures of three of the four reaction products were elucidated. The kinetics of formation of these reaction products were then investigated at a range of pH values, and in two wastewater matrices. One reaction product, 4’-ClGem was shown to form under conditions relevant to wastewater treatment. The impacts of gemfibrozil and 4’-ClGem presence on the abundance of suspended and biofilm bacteria in a simulated receiving water experiment were evaluated. It was shown that changes in the water matrix had more of an impact on bacterial abundance than presence of gemfibrozil or 4’-ClGem. A bacterial dose-response experiment showed a negative response at 10 mg/L exposure to 4’-ClGem, which is orders of magnitude higher then what would be found in receiving waters. In order to prevent the formation of chlorinated reaction products, it is necessary to remove gemfibrozil prior to disinfection. Recirculating biofilters (RBS), a biological technology for onsite or small-scale wastewater treatment, were explored as a potential treatment process for gemfibrozil removal. Results indicate that RBFs show promise as a robust technology to remove greater than 50% of influent gemfibrozil.