Occurrence of nonylphenol ethoxylates and their metabolites in municipal wastewater treatment plants and receiving waters.

Nonylphenol ethoxylates (NPEs) are surfactants often used in applications that result in their disposal and treatment in wastewater treatment plants (WWTPs). In this study, three municipal activated sludge WWTPs, receiving primarily residential wastewater, were monitored, with their receiving waters, to determine the occurrence of NPEs and their biodegradation metabolites, including nonylphenol (NP), low-mole and higher-mole nonylphenol ethoxylates (NPE1, NPE2-8, and NPE > or =9), and nonylphenol ether carboxylates (NPECs). The facilities were moderately sized and operating normally when influent and effluent samples were taken. Treatment efficiencies, taking into account concentrations of the parent ethoxylate and metabolites, ranged from 97.2 to 99.8%. Samples of receiving stream water, sediment, and pore water were collected upstream, downstream at the end of the mixing zones, and farther downstream from the WWTP discharges, to determine the occurrence of NPE and their metabolites and to assess the potential effect on the receiving stream ecosystems. Concentrations of nonylphenol or total nonylphenol equivalents measured upstream (<0.02 to 1.29 microg/L), at the end of the mixing zone (0.2 to 3.15 microg/L), and farther downstream (<0.02 to 1.84 microg/L) were compared with the recently established national ambient water quality chronic criteria of 6.6 mcirog/L. On the basis of this analysis, the likelihood of adverse effects on aquatic species within the three receiving streams is low.