TIN AND ORGANOTIN SPECIATION DURING WASTE-WATER AND SLUDGE TREATMENT PROCESSES

The speciation of inorganic tin and organotin compounds is studied in raw water samples and in filtered water samples collected along the ma in steps of the wastewater treatment plant of Bordeaux City (France). Analyses are performed by hydride generation, cryogenic trapping, chro matographic separation and detection by atomic absorption spectrometry . Results show that dissolved inorganic, methylated tin (mono-, di-, t rialkylated forms) and butyltin compounds (mono- and dialkylated forms ) occur at all stages of the water treatment process. Butyltins were f ound at low concentration levels which tends to show that the weatheri ng of PVC is a minor phenomenon. High methyltin contents were however found which illustrate the high methylation rate in sewage water; a ge neral removal trend from the water is observed for inorganic and methy l-tin species both in raw water and filtered water samples. Volatiliza tion of tin compounds is observed in the anaerobic fermentation steps of the activated sludge. Possible pathways for transformation of tin ( methylation, volatilization) during the wastewater treatment are discu ssed.