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Pentabromodiphenyl ethers (PeBDEs) are components of brominated flame retardants which have been detected in various environmental media (waste water, sewage sludge, sediments, and aquatic biota). They are ”︁priority pollutants”. Sewage sludge from 20 different sewage treatment plants under summer and winter conditions showed PeBDE levels in primary sludge of up to 70 μg kg—1 with a dominant range of 5—20 μg kg—1. To insure a safe sludge use in agriculture, sorption, mobility, and dissipation experiments using soil substrates were conducted. PeBDE was bound strongly to organic matter (Koc = 125,000) while Kd values after FREUNDLICH of about 90 and 700 were obtained for clay and sand, respectively, and of 45,000 for humus. Less than 0.001 % was found in eluates from laboratory lysimeters, and about 91 % remained at a depth of 0—3 cm. Thus PeBDE has a low mobility. In the indicative dissipation tests, the recovery rate after 3 weeks was about 50 %, and about 20—25 % was still detectable after 8 weeks. PeBDE proved to be less persistent than previously assumed. A formation of bound residues is presumed to be likely. Only a small difference was found between aerobic and anaerobic dissipation. The strong fixation in soil suggests a need to clarify whether PeBDE accumulates in soil.

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A standardized evaluation concept based on human toxicity, ecotoxicity and soil related data has been developed for the assessment of pollutants in sewage sludge. This assessment concept for different compounds is applicable using evaluation steps that are comparable and transparent based on a classification system. All compounds assessed here were assigned to three groups: pollutants of primary relevance, pollutants of secondary relevance and such, on which more information is necessary for evaluation. For the purpose of comparing the evaluation concept with results from some investigations under field and laboratory conditions degradation, sorption, retardation and plant transfer data for LAS are presented and discussed.

No abstract