Organophosphorus flame retardants and plasticizers in Swedish sewage treatment plants

The levels, distribution, and possible sources of 12 organophosphorus flame retardants and plasticizers, some of which are reported to be toxic to aquatic organisms, were investigated in samples of influents, effluents, and sludge from 11 Swedish sewage treatment plants (STPs). The organophosphorus compounds (OPs) studied were poorly removed from the wastewater; especially the chlorinated OPs tended to pass through the STPs without being removed or degraded, while alkyl-OPs, such as tributyl phosphate (TBP), were more successfully removed. In both influents and effluents, tris(2-butoxyethyl) phosphate and TBP were the most prominent substances followed by tris(2-chloroisopropyl) phosphate (TCPP). The highest concentration of any individual OP detected in the influents was 52 mu g L-1 (TBP). Ethylhexyl diphenyl phosphate and TCPP dominated in all sludge samples. A budget calculation comparing the annual amount of OPs in the influent received by Swedish STPs with the known amount of OPs imported indicated that approximately 15% is emitted to STPs. Of the total amount of OPs reaching the STPs annually, 49% is degraded, 50% (27 tons) is emitted to the recipients, and only 1% ends up in the sludge. The concentrations of most OPs were quite similar among the sampled STPs, indicating that the data may be applicable in other STPs.