AIS(+) CESIO(+) ENVIRONMENTAL SURFACTANT MONITORING PROGRAM - OUTCOMEOF 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 referen ce compound, is described. A very high average LAS removal of 99.2% in sewage treatment has been found. Hence, only low concentrations of LA S 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 wer e also low, range 0.49 - 5.3 mu g/g, which suggested that the surfacta nt was effectively bioeliminated in this environmental compartment. Th e accuracy of the predictions generated with the SIMPLETREAT and WWTRE AT sewage treatment plant models has been checked using the LAS monito ring data. These mathematical models are shown to be useful tools, par ticularly WWTREAT, for gaining an understanding of the fate and distri bution of chemicals during sewage treatment. The many insights gained from these pilot studies have led to an improved experimental design f or use in further surfactant monitoring exercises. In addition, the fi ndings support the view that LAS concentrations in aquatic environment for situations where waste water is treated to those standards accept ed as the EU 'norm', are well below the predicted no effect concentrat ions i.e. 100 to 350 mu g/l for aquatic ecosystems.