Fate of four phthalate plasticizers under various wastewater treatment processes

Authors: ARMSTRONG, DANA - University Of Maryland; Rice, Clifford; RAMIREZ, MARK - District Of Columbia Water & Sewer Authority (DCWASA); TORRENTS, ALBA - University Of Maryland

Submitted to: Journal of Environmental Science and Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/30/2018
Publication Date: 5/18/2018
Citation: Armstrong, D.L., Rice, C., Ramirez, M., Torrents, A. 2018. Fate of four phthalate plasticizers under various wastewater treatment processes. Journal of Environmental Science and Health. https://doi.org/10.1080/10934529.2018.1474580.

Interpretive Summary: Phthalate plasticizers are widely used in commerce, occur widely in the environment and have several suspected affects on humans and other biota. Major environmental releases of these products occur when waste treatment plants produce biosolids that are land applied. Amount reductions can occur during treatment by these plants but there is a general lack of knowledge of how effective different plants are at removing these phthalates. To address this lack of knowledge, four commonly detected phthalate plasticizers, benzyl butyl phthalate (BBP), di(2-ethylhexyl) phthalate (DEHP), diisononyl phthalate (DiNP), and diisodecyl phthalate (DiDP), were determined prior to either aerobic or anaerobic treatment, after treatment, and in final dewatered solids at six different waste water treatment plants located in Maryland. Results varied by processing systems and compound. DEHP was readily degraded during aerobic treatments while anaerobic digestion resulted in either no significant change in concentrations or an increase when more advanced anaerobic systems were employed. Aerobic treatment was generally effective at degrading the other compounds, while anaerobic degradation varied. A predicted environmental concentration for DEHP after a one-time application of contaminated biosolids was found to be below acute or chronic risks as defined by the US EPA. This information will be useful to policymakers and people operating water treatment plants.

Technical Abstract: The fate of four phthalate plasticizers during wastewater treatment processes at six different wastewater treatment plants (WWTPs) was investigated. Concentrations of benzyl butyl phthalate (BBP), di(2-ethylhexyl) phthalate (DEHP), diisononyl phthalate (DiNP), and diisodecyl phthalate (DiDP) were determined prior to either aerobic or anaerobic treatment, after treatment, and in final, dewatered solids. DEHP was readily degraded during aerobic treatments while anaerobic digestion resulted in either no significant change in concentrations or an increase in concentration, in the case of more advanced anaerobic processes. Impacts of the various treatment systems on DiNP, DiDP, and BBP concentrations were more varied – anaerobic digestion led to significant decreases, increases, or no significant change for these compounds, depending on the treatment facility, while aerobic treatment was generally effective at degrading the compounds. Additionally, thermal hydrolysis pretreatment of sludge prior to anaerobic digestion resulted in increases in DiNP, DiDP, and BBP concentrations. The predicted environmental concentrations for all four compounds in soils after a single biosolids application were calculated and the risk quotient for DEHP in soils was determined. The estimated toxicity risk for DEHP in soils treated with a single application of sludge from any of the six studied WWTPs is lower than the level of concern for acute and chronic risk, as defined by the US EPA.