Occurrence of organotins in municipal wastewater and sewage sludge and behavior in a treatment plant

The fate of mono-, di- and tri-butyltin (MBT, DBT, TBT, respectively), was investigated at a Zurich sewage works employing activated sludge. Flow proportional composite samples were taken of the liquid phases and snap samples of the sludges. Organotin compounds were extracted, cleaned-up, derivatized with ethyl magnesium bromide and analysed by capillary gas chromatography with a flame ionization detector. No phenyl-, dioctyl- or tricyclohexyl-tins were found. Influent concentrations of MBT, DBT, and TBT were 136-564, 127-1026 and 64-217 ng per litre, respectively, with 81-92 per cent associated with suspended solids. Secondary effluent concentrations were 7-47 ng per litre. Removal was through sedimentation of solids. Concentrations of MBT, DBT and TBT in digested sludges were 0.10-0.97, 0.41-1.24 and 0.28-1.51 ppm on dry matter, respectively. The concentrations in sludge and untreated sewage were environmentally significant. There are 30 references.