Bile acids and sterols in urban sewage treatment plants

The composition of bile acids, sterols and sterones in water and sludge fro m an urban sewage treatment plant has been examined for assessment of the p ossible use of these compounds as pollution biomarkers. Samples were solven t-extracted, hydrolysed, and fractionated by column chromatography to separ ate acids, hydrocarbons, sterones and sterols. These fractions, except hydr ocarbons, were methylated (acids only) and silylated for instrumental analy sis. Gas chromatographic-mass spectrometric analysis was performed in the e lectron-impact mode, using a non-polar capillary column. Lithocholic acids (3 alpha- and 3 beta -epimers), coprostanone, coprostanol, cholesterol, cho lestenone, and cholestanone were found in sludge and all waters. However, t he waters after secondary plant treatment contained mainly lithocholic acid s epimers and coprostanone, pointing to these compounds as potential marker s for urban treatment plant effluents in natural waters courses. (C) 2001 E lsevier Science B.V. All rights reserved.