Correspondence Comment on “Fate of Octyl- and Nonylphenol Ethoxylates and Some Carboxylated Derivatives in Three American Wastewater Treatment Plants” Our review of the Loyo-Rosales, et al. paper ((1)) shows the following. (1) There appears to be a reversal in the reported influent and effluent alkylphenoxyethoxy carboxylates (APEC) data in their Table 2. (2) The authors’ key conclusions are not supported by the authors’ data. And (3) It appears that the authors are confusing wastewater treatment plant (WWTP) “removal” with WWTP “degradation” or “transformation”. It appears that the APEC data in their Table 2 (last column) for influent and effluent have been reversed. It is difficult to believe that all three WWTPs are such a significant source of APECs. If the data are indeed reversed, then the authors need to check and revise Figures 2 and 3 and any resulting conclusions from this discrepancy. Based upon the data in their Table 2, we have calculated alkylphenol ethoxylates (APEOs) (nonylphenol ethoxylates [NPEOs] + octylphenol ethoxylates [OPEOs]) removal for these three WWTPs as follows: We have also included total suspended solids (TSS) removal data in the above table. These data are taken from the authors′ Table S-2 (Supporting Information). As one can see from the above table, the APEOs removal varied from 95.4 to 99.7% for all three plants during summer and winter sampling events. We believe that the APEOs removal range from all three of these WWTPs is excellent and contradictory to the authors’ following general and specific conclusions. General: “. . . overall removal from WWTPs was relatively low and suggested that advanced treatment does not invariably result in better APEO removal.” Specific: (1) “Plant 1 performed similarly to Swiss plants: almost 60% of the incoming APEO mass was released in the effluent and sludge. . .”. (2) “Plant 3 released slightly more than 40% in the winter and approximately 30% in the summer.” (3) “In the case of Plant 2, most of the APEO elimination occurred in the solids, resulting in almost 90% of the APEOs being released from the WWTP”.
10.1021/es702994v CCC: $40.75
Published on Web 05/10/2008
2008 American Chemical Society
TABLE 1. WWTP APEO (NPEO + OPEO) Removals removal, percent plant no.
season
APEOs
TSS
1 1 2 2 3
summer winter summer winter winter
99.4 95.4 99.4 97.0 95.7
98.6 95.0 99.0 98.7 81.5
Based upon the information provided by the authors in their Table 2, all three of these plants appear to be publicly owned treatment works (POTWs). All POTWs are designed to mainly remove TSS and biological oxygen demand (BOD) (a minimum of 85% of each). Some POTWs have additional biological systems to remove nutrients like the authors′ Plants 1 and 2. As is obvious from the data in Table 1 above, all three of these plants are removing APEO greater than 95%; we regard this removal rate as excellent. Interestingly, for Plant 3, while the TSS removal in winter dropped below 85%, the APEO removal remained greater than 95%. We would like to bring to the authors′ attention that the removal of APEO in primary or biological sludge constitutes an overall removal of APEO from each of the three WWTPs’ respective influents and, consequently, from their respective receiving waters. Since the primary and the biological sludge are separated from the effluent (discharge) and processed (incinerated or biologically digested and disposed of at regulated landfills or land application), there is no chance of these APEOs entering their respective receiving waters.
Literature Cited (1) 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, 6815–6821.
Bhupinder S. Dhaliwal and Douglas J. Craig Plant Operations Department, Central Contra Costa Sanitary District, 5019 Imhoff Place, Martinez, California 94553 ES702994V
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