Sources and behaviour of bismuth active substances (BiAS) in a municipal sewage treatment plant

Non-ionic surfactants are widely used for household and industrial purposes. For different reasons the metabolites, e.g. 4-nonylphenol, nonylphenol monoethoxylate, nonylphenol diethoxylate and 4-tert-octylphenol, are especially considered to be endocrine disruptive and thus potentially harmful for the environment. In this study, field samples of raw wastewater from different point sources, including industrial effluents, household effluents, the influent and secondary effluent of a wastewater treatment plant that treats this wastewater were monitored simultaneously. Composite samples were taken five times over periods of 1 week at nine sample sites. The results showed that the concentrations and fluxes were varying. In addition industrial, influent and effluent samples were investigated for nonylphenol (NP). The highest concentrations of bismuth active substances (BiAS) were obtained by wastewater samples from a chemical and a cloth washing company ranging from 10,200 to 65,600 microg/l and 14,600 to 33,900 microg/l BiAS, respectively. Although the concentration of BiAS in the wastewater of the paper production was only between 460 and 1200 microg/l BiAS, the NP/BiAS ratio of 0.51% was considerably higher than in other industrial effluents. The BiAS concentration in wastewater samples from households ranged from 2200 to 7900 microg/l BiAS, but the NP concentration was quite low, 0.01% of BiAS. This could be due to the effort within the EU to phase out nonylphenol polyethoxylates in household detergents. Influent concentrations between 700 and 2200 microg/l BiAS with removal rates in the WWTP ranging from 70.7 to 99.4% with an average of 92.2% could be measured.