BEHAVIOR OF ALKYLPHENOL POLYETHOXYLATE SURFACTANTS IN THE AQUATIC ENVIRONMENT .1. OCCURRENCE AND TRANSFORMATION IN SEWAGE-TREATMENT

Specific analytical techniques were used to study the behaviour of alkylphenol polyethoxylate surfactants (APnEO) in several full-scale mechanical-biological sewage treatment plants in the Glatt Valley, Switzerland. Both parent compounds and the major metabolic products were quantified. Untreated sewage and primary effluents contained considerable amounts of surfactant-derived nonylphenolic compounds (3.0-9.6% of the dissolved organic carbon). Parent nonylphenol polyethoxylates (nEO = 3-20) were efficiently eliminated during biological treatment. However, the overall rate of biodegradation was limited due to the formation of biorefractory metabolites, including nonylphenol (NP), nonylphenol mono- and diethoxylate (NPIEO, NP2EO) and nonylphenoxy carboxylic acids (NPEC). The abundance of a particular metabolite was very dependent on the treatment conditions. Studies of the mass hows of nonylphenolic compounds in sewage treatment plants indicated that their fate was determined not only by microbial transformation, but also by physicochemical processes.