engleski

Surfactant-derived Alkylphenolic Compounds in Sewage Effuents and Ambient Waters in Switzerland before and after Risk Reduction Measures

Between 1982 and 1985 nonylphenol polyethoxylates (NPnEO, n=3-20) and their major metabolic products: 4-nonylphenol (NP), 4-nonylphenol monoethoxylate (NP1EO), 4-nonylphenol diethoxylate (NP2EO), nonylphenoxy acetic acid (NP1EC) and nonylphenoxy(ethoxy) acetic acid (NP2EC) were intensively investigated in sewage effluents, sewage sludges, and in ambient waters in Switzerland. Based on the results of these exposure measurements, the use of NPnEO as nonionic surfactants in laundry detergents was banned in 1986 by the Swiss ordinance for environmental pollutants. The detergent manufacturing company voluntarily stopped the addition of NPnEO surfactants to household surface cleaners, but still included them in industrial cleaners and in some other industrial applications. The objective of the study presented here was to evaluate the effect of these legal and voluntary risk reduction measures on the residual levels of nonylphenolic chemicals in municipal wastewaters and in rivers. Enrichment of the NPnEO surfactants (n=3-20) from sewage effluents was carried out by solid-phase extraction using graphitized carbon black (Carbopack B). Enrichment of the lipophilic metabolic products (NP, NP1EO and NP2EO) from secondary sewage effluents and from river water was performed by liquid/liquid extraction with hexane, while NP1EC and NP2EC were extracted using C18 solid-phase extraction. The extracts of NPnEO as well as of the lipophilic metabolites were subsequently analysed by normal-phase HPLC, while NPnEC were analysed by C18 reversed-phase HPLC. Fluorescence detection with wavelengths set at 228 nm for excitation and 305 nm for emission was applied for the analyses of all nonylphenolic compounds considered. Primary sewage effluents of the sewage treatment plant of the city of Zurich contained in October 1997 NPnEO levels around 0.15 mg/L compared to 0.7 - 1.0 mg/L in 1983. Thus, the emission of NPnEO surfactants has been reduced to approximately 10 %. As a consequence, the concentration of different types of NPnEO-metabolites in biologically treated effluents was also significantly reduced. Typical concentration levels of NP found for the Zurich area in 1997/8 were 0.2 - 1.2 ľg/L NP accompanied by NP1EO and NP2EO determined at similar concentrations. Treated waste waters in Eastern Switzerland receiving effluents from textile finishing plants showed elevated levels of NP, and NP1/2EO with maximum concentrations of NP, NP1EO, and NP2EO of 3.5, 5, and 5 ľg/L, respectively. The concentration of nonylphenolic compounds in ambient waters strongly decreased after the 1986 ban. In the Glatt River near Zurich concentrations of NP, NP1EO and NP2EO measured during 1997/8 were in the range of 0.1 - 0.3 ľg/L in comparison to 0.5 - 21 ľg/L in 1983/4. The same type of strong reduction was observed for NPnEC, which decreased from approximately 50 mg/l in 1983/4 to 0.5-5 mg/l in 1998, but remained the predominant nonylphenolic compounds in the river. The risk reduction measures for NPnEO and the improvement of sewage treatment plants have a significant impact on the residual levels found in wastewaters and receiving rivers. The observed attenuation varies considerably. Similarly, the different relative composition found for NP, NP1/2EO and NP1/2EC are probably reflecting differences in the particular wastewater treatment plants and rivers. The reduction of environmental inputs of nonylphenolic compounds could also be detected as it is archived in recent sediments of Swiss lakes. The results of this latter investigation based on dated sediment cores reflected the increased use of NPnEO-surfactants in the early 1960's and a decreased discharge of NP and NP1/2EO after 1986.

nonionic surfactants; nonylphenol; sewage effluents; natural waters; risk assessment

nije evidentirano