AIS(+)/CESIO(+) ENVIRONMENTAL SURFACTANT MONITORING PROGRAM - OUTCOME OF 5 NATIONAL PILOT-STUDIES ON LINEAR ALKYLBENZENE SULFONATE (LAS)

The outcome of pilot surfactant monitoring studies at activated sludge sewage treatment plants (STPs) in Germany, UK, the Netherlands, Spain and Italy which have used the anionic surfactant, LAS, as the reference compound, is described. A very high average LAS removal of 99.2% in sewage treatment has been found. Hence, only low concentrations of LAS were discharged to the receiving waters, the range of mean effluent concentrations was 0.009 - 0.140 mg/l. The concentrations of LAS found on sediment at river sampling sites below the effluent discharges were also low, range 0.49 - 5.3 mu g/g, which suggested that the surfactant was effectively bioeliminated in this environmental compartment. The accuracy of the predictions generated with the SIMPLETREAT and WWTREAT sewage treatment plant models has been checked using the LAS monitoring data. These mathematical models are shown to be useful tools, particularly WWTREAT, for gaining an understanding of the fate and distribution of chemicals during sewage treatment. The many insights gained from these pilot studies have led to an improved experimental design for use in further surfactant monitoring exercises. In addition, the findings support the view that LAS concentrations in aquatic environment for situations where waste water is treated to those standards accepted as the EU 'norm', are well below the predicted no effect concentrations i.e. 100 to 350 mu g/l for aquatic ecosystems.