POLYCHLORINATED DIBENZO-P-DIOXINS AND DIBENZOFURANS IN SEWAGE-SLUDGE - SOURCES AND FATE FOLLOWING SLUDGE APPLICATION TO LAND

Municipal sewage sludge is ubiquitously contaminated with polychlorina ted dibenzo-p-dioxins and dibenzofurans (PCDD/F). Whereas in Germany t here are some industrial sources, associated in particular with the us e of pentachlorophenol (PCP) in the textile industry, surface runoff a nd household wastewater play a more important role in most treatment p lants. Most of the higher chlorinated PCDD/F congeners in sludge origi nate in textiles which become contaminated during production through t he use of PCP. The PCDD/F, which are contaminants in technical PCP, ar e washed out of textiles in the washing machine and enter household wa stewater. The lower chlorinated PCDD/F, on the other hand, reach sludg e largely as the result of transport of atmospheric deposition to the treatment plant in surface runoff. Following application of sewage slu dge to land, the PCDD/F are very persistent, with half lives in excess of 10 years. They accumulate in soils End can under some conditions e nter the agricultural food chain. The potential risk of land applicati on of sewage sludge increasing human exposure to PCDD/F depends on the level of sludge contamination, the intensity of sludge use and the ag ricultural practices.