Environ. Sci. Technol. 2008, 42, 4614
Response to Comment on “Fate of Octyl- and Nonylphenol Ethoxylates and Some Carboxylated Derivatives in Three American Wastewater Treatment Plants” In their comment (1) on our paper on the fate of alkylphenol ethoxylates (APEO) in wastewater treatment plants (2), Dhaliwal and Craig suggest that the alkylphenoxyethoxy carboxylate (APEC) concentrations in influents and effluents were reversed because wastewater treatment plants (WWTPs) cannot be “such a significant source of APECs”. However, APEC formation in WWTPs has been reported in the literature from the early studies on APEO degradation (3–5), and we did not emphasize it in our paper precisely because it is a widespread phenomenon (6, 7). APEC concentrations have been shown to constitute a predominant fraction of APEOrelated compounds in WWTP effluent (4, 5), and the concentrations we reported were within the range found by other groups (4–6, 8). Additionally, we find no reason to question our analytical results; although we calculated APEC concentrations using an external standard approach, we verified some of these measurements using standard additions and we found little deviation from the original results (9). Therefore, we stand by the APEC data and conclusions we derived from them. We do agree with Dhaliwal and Craig in that APEO removal from water is excellent in the three WWTPs, especially considering that these plants were not originally designed to remove this class of pollutants. We also agree that the compounds released from the plants with the waste sludge undergo further treatment and they are therefore less likely to reach the receiving waters. However, we believe that a proper assessment of a pollutant’s fate in WWTPs must extend beyond elimination of the pollutant from water, and include all possible environmental compartments and transformation products. It is of course possible that compounds that are removed with sludge rather than biodegraded in the WWTP might not pose an environmental risk, but their fate in the sludge has to be considered and should not be ignored, especially considering that some of these chemicals might be recalcitrant to biodegradation and that biosolids are routinely applied in the environment. In the case of transformation products, some of these might be less toxic than the parent compounds, such as the APECs in our case, but their fate needs to be considered nevertheless when evaluating the overall risk of APEOs to aquatic species.
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We are aware that terms such as “removal from wastewater” are ill defined at best. We deliberately discussed APE removal from wastewater and overall removal from WWTPs in separate sections of our manuscript in an attempt to avoid confusion. We hope that these comments serve as further clarification of this issue.
Literature Cited (1) Dhaliwal, B. S.; Craig, D. J. Comment on “Fate of octyl- and nonylphenol ethoxylates and some carboxylated derivatives in three American wastewater treatment plants”. Environ. Sci. Technol. 2008, 42, 4613. (2) Loyo-Rosales, J. E.; Rice, C. P.; Torrents, A. Fate of octyl- and nonylphenol ethoxylates and some carboxylated derivatives in three American wastewater treatment plants. Environ. Sci. Technol. 2007, 41 (19), 6815–6821. (3) Reinhard, M.; Goodman, N.; Mortelmans, K. E. Occurrence of brominated alkylphenol polyethoxy carboxylates in mutagenic wastewater concentrates. Environ. Sci. Technol. 1982, 16 (6), 351–362. (4) Ahel, M.; Conrad, T.; Giger, W. Persistent organic chemicals in sewage effluents. 3. Determinations of nonylphenoxy carboxylic acids by high-resolution gas chromatography/mass spectrometry and high-performance liquid chromatography. Environ. Sci. Technol. 1987, 21 (7), 697–703. (5) Ahel, M.; Giger, W.; Koch, M. Behaviour of alkylphenol polyethoxylate surfactants in the aquatic environment—I. Occurrence and transformation in sewage treatment. Water Res. 1994, 28 (5), 1131–1142. (6) Bennie, D. T. Review of the environmental occurrence of alkylphenols and alkylphenol ethoxylates. Water Qual. Res. J. Canada 1999, 34 (1), 79–122. (7) Montgomery-Brown, J.; Reinhard, M. Occurrence and behavior of alkyphenol polyethoxylates in the environment. Environ. Eng. Sci. 2003, 20 (5), 471–486. (8) Field, J. A.; Reed, R. L. Nonylphenol polyethoxy carboxylate metabolites of nonionic surfactants in U.S. paper mill effluents, municipal sewage treatment plant effluents, and river waters. Environ. Sci. Technol. 1996, 30 (12), 3544–3550. (9) Loyo-Rosales, J. E.; Rice, C. P.; Torrents, A. Octyl and nonylphenol ethoxylates and carboxylates in wastewater and sediments by liquid chromatography/tandem mass spectrometry. Chemosphere 2007, 68 (11), 2118–2127.
Jorge E. Loyo-Rosales, Clifford P. Rice, and Alba Torrents Department of Civil and Environmental Engineering, University of California, Berkeley, 207 O’Brien Hall, Berkeley, California 94720, Environmental Management and Byproducts Utilization Laboratory, ANRI, ARS/USDA, 10300 Baltimore Avenue, Beltsville, Maryland 20705, and Department of Civil and Environmental Engineering, University of Maryland, College Park, 1173 Glenn L. Martin Hall, College Park, Maryland 20742 ES800010X
10.1021/es800010x CCC: $40.75
2008 American Chemical Society
Published on Web 05/10/2008
