Occurrence and distribution of persistent organochlorine compounds in U.K. sewage sludges

A total of 444 sewage sludges, sampled from sewage treatment works in the U.K., were analyzed for polychlorinated biphenyls (PCB) and the organochlorine insecticides γ-Hexachlorocyclohexane (γ-HCH), aldrin, dieldrin and endrin. PCB, γ-HCH and dieldrin were found to occur more frequently and at higher concentrations in sewage sludges than aldrin and endrin. In order to investigate the temporal variation of these compounds in sewage sludge, three sewage treatment works were sampled at monthly intervals over an 18 mo period. PCB, γ-HCH and dieldrin were again the most frequently detected compounds. Concentrations of aldrin and endrin were only sporadically detected. The results of a serial correlation analysis of these data indicated that some short term correlation of PCB and dieldrin concentrations above and below the mean value was evident. The data acquired in the course of this survey have been compared with the results of similar work conducted previously in the U.K. and other countries. The possible implications of the presence of persistent organochlorine compounds in sewage sludges which are disposed to the environment are discussed.