Investigation of the natural degradation of selected endocrine disrupting compounds in wastewater
Endocrine disrupting compounds (EDCs) are a class of compounds that are of concern for their potentially adverse effects on fish, wildlife, and humans. They can cause developmental and reproductive anomalies at concentrations in the low ppb to ppt levels. Studies have shown the primary route of exposure of EDCs within the environment is through the discharge of effluent wastewater. Removal efficiencies of wastewater treatment plants have been studied extensively, however, in rural or developing areas, which often lack secondary or tertiary wastewater treatment, little is known about the stability of these compounds and the rate at which they degrade in untreated wastewater. Two of the most commonly found EDCs in wastewater are nonylphenol (NP) (used in personal care products, detergents, and the production of nonylphenol ethoxylate surfactants) and bisphenol A (BPA) (used in the production of polycarbonate plastics, epoxy resins, and other common household items). Therefore, the aim of this research was to investigate the degradation of BPA and NP in untreated wastewater. It was found that in ultrapure water, abiotic degradation (e.g. hydrolysis and photodegradation) of NP was negligible, regardless of pH throughout a storage period of around 30 days. For BPA, it was found that both photodegradation and hydrolysis occurred. In wastewater, NP, NPEO1, and BPA all underwent biodegradation. It was also determined that a single autoclave cycle of 60 minutes was not enough to kill all of the bacteria present in the wastewater capable of degrading NP and BPA. Filtration of samples did seem to be effective in reducing, although not completely stopping, biodegradation of NP and NPEO1. Further pH adjustment to either an acidic pH (e.g. 3) or basic pH (e.g. 11) helped to further slow degradation in an autoclaved filtered wastewater. For BPA, filtration of wastewater seemed to enhance degradation. In unfiltered wastewater, biodegradation of NP, NPEO1, and BPA also occurred. In all wastewater samples, BPA followed first order degradation, and both NP and NPEO1 followed second order degradation. Although most removals were generally incomplete, 100% removal was proven possible at some point for all compounds studied, albeit the rates are very slow. The results presented herein demonstrate the degradation capabilities of NP and BPA in ultrapure and wastewater.
Carrick, Toni, "Investigation of the natural degradation of selected endocrine disrupting compounds in wastewater" (2015). ETD Collection for University of Texas, El Paso. AAI1600309.