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Title: Fate of Octyl- and Nonylphenol Ethoxylates and Some Carboxylated Derivatives in Three American Wastewater Treatment Plants

Author
item LOYO-ROSALES, JORGE - UNIV MD, COLLEGE PARK
item Rice, Clifford
item TORRENTS, ALBA - UNIV MD, COLLEGE PARK

Submitted to: Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/30/2007
Publication Date: 10/1/2007
Citation: Loyo-Rosales, J.E., Rice, C., Torrents, A. 2007. Fate of Octyl- and Nonylphenol Ethoxylates and Some Carboxylated Derivatives in Three American Wastewater Treatment Plants. Environmental Science and Technology. 41(19):6815-6821.

Interpretive Summary: Nonionic surfactants belonging to the alkylphenol ethoxylate group enter waste water treatment plant in great quantities since they are heavily used as cleaning agents. Few recent studies exist on their fate in US waste water treatment plants. The specific and more abundant ingredients of this group, nonylphenol and octylphenol ethoxylates and several of their carboxylated derivatives, were studied in three American wastewater treatment plants (WWTPs), two of which included advanced treatment. In spite of being located in three different metropolitan areas, wastewater entering the WWTPs had similar concentrations of the alkylphenolic compounds; whereas effluent concentrations were only similar when samples from the same season (summer or winter) were compared. Ethoxylate and carboxylate concentrations in winter were on average seven and four times higher than in summer, with carboxylate accumulation showing more variability than APEO depletion. Sorption to particulate was on average 1.6 times higher for nonylphenolic compounds than for their octylphenolic counterparts, in agreement with their difference in octanol water partition coefficient values. Both effluent concentrations and APEO removal rates—the latter averaging 99% in summer and 94% in winter for the NPEOs—were strongly correlated to water temperature, but no correlation was found with suspended solids or organic carbon removal. Mass balance calculations for these WWTPs suggested that advanced treatment did not invariably result in better APEO removal. Additionally, a small survey of urban sewers suggested that household products still constitute an important source of the APEOs reaching WWTPs.

Technical Abstract: The fate of a comprehensive group of nonylphenol and octylphenol ethoxylates and several of their carboxylated derivatives was studied in three American wastewater treatment plants (WWTPs), two of which included advanced treatment. In spite of being located in three different metropolitan areas, wastewater entering the WWTPs had similar concentrations of the alkylphenolic compounds; whereas effluent concentrations were only similar when samples from the same season (summer or winter) were compared. Ethoxylate and carboxylate concentrations in winter were on average seven and four times higher than in summer, with carboxylate accumulation showing more variability than APEO depletion. Sorption to particulate was on average 1.6 times higher for nonylphenolic compounds than for their octylphenolic counterparts, in agreement with their difference in Kow values. Both effluent concentrations and APEO removal rates—the latter averaging 99% in summer and 94% in winter for the NPEOs—were strongly correlated to water temperature, but no correlation was found with suspended solids or organic carbon removal. Mass balance calculations for these WWTPs suggested that advanced treatment did not invariably result in better APEO removal. Additionally, a small survey of urban sewers suggested that household products still constitute an important source of the APEOs reaching WWTPs.