Bile Acids as a New Class of Sewage Pollution Indicator

The bile acid content of raw sewage, treated effluent, and estuarine sediment was determined as the first step in the development of bile acids as a new class of sewage pollution indicator. Sediments and particulates from raw sewage and effluent, were solvent extracted, saponified, fractionated by solid phase extraction (SPE) and “flash” column chromatography, derivatized, and analyzed by gas chromatography (GC) and GC/mass spectrometry (GC/MS). Mass spectral comparisons confirmed unambiguously the presence of bile acids in all the samples studied. The major compounds detected were deoxycholic and lithocholic acids, together with minor components, in a characteristic distribution that reflected the predominantly human origin of the effluent. Bile acids were found to exist in a “bound” form and were released upon saponification. They were found to be quantitatively relatively more resistant to degradation during sewage treatment as compared to coprostanol. Some changes were observed in the abundances of certain minor bile acids, for example, the 3β-epimers were much reduced in relative abundance in the treated effluent and sediment as compared to their 3α counterparts. Bile acids offer considerable promise as indicators of specific sources of sewage pollution, particularly if used in conjunction with the widely employed 5β-stanols, e.g., coprostanol.