AbstractThe commercial use of fluorescent whitening agents (FWA' s) in products such as soaps and detergents has resulted in the presence of these compounds in domestic waste waters.
A model compound (A) (a possible initial degradation product of a stilbene-s-triazine type FWA) was synthesised and biodegradation studies carried out on this compound in filtered activated sludge solution. During the test period (approximately 6 months) no degradation products were observed.
Prior to undertaking biodegradation studies on a purified commercial stilbene-s-triazine FWA, Blankophor REU-P, a method was sought to determine its concentration in aqueous solution. Using ultraviolet absorbance measurements the concentration of the Blankophor could be determined in distilled water. However, this method was unsuitable when the Blankophor was dissolved in filtered activated sludge solution. Attempts to extract the Blankophor from filtered activated sludge solution using solvent extraction and ion-exchange resins were unsuccessful.
Using computer modelling (SIMCA), combined with ultraviolet absorbance measurements, it was possible to determine the concentration of the Blankophor in filtered activated sludge solution. Biodegradation studies were undertaken with the Blankophor using this method to monitor the Blankophor concentration. During the test period (six days) the Blankophor concentration fell from 1Oppm to approximately 5. 5ppm. It was possible to deduce that the Blankophor was not being absorbed onto the solid material of the activated sludge and that it had been metabolised and/or isomerised.
Two ion-pairing agents, tetraphenyl arsoniurn chloride and oly[oxyethylene(dimethylimino)-ethylene(diethylimino)-ethylene] were examined to try to separate the Blankophor and the metabolites and/or isomers from the filtered activated sludge solution but no successful separation was achieved. Thin layer chromatography was examined briefly but again with no success.
Photolysis experiments were undertaken with the Blankophor in distilled water. The concentration of the Blankophor fell from 1Oppm to approximately 7. 5ppm and its ultraviolet spectrum changed shape. This, coupled with the fact that the control spectra remained unaltered, indicated that the Blankophor had undergone photolytic conversion to metabolites and/or isomers.
Although it is clear that FWA' s are fairly stable compounds which are slow to bio- and photo-degrade and that their toxicity to man, both directly and by bio-accumulationis is minimal little is still known about the toxicity of possible degradation products.
|Date of Award||Jan 1990|