Emissions of OTNE (Iso-E-super) - mass flows in sewage treatment plants.

The fate and mass flows of OTNE ([1,2,3,4,5,6,7,8-octahydro-2,3,8,8-tetramethylnaphthalen-2yl]ethan-1-one) which is commercialized as Iso-E-Super were studied in three large scale sewage treatment plants (STPs) in detail. The results are compared to 14 smaller ones located in Germany and Switzerland. OTNE inflow concentrations ranged from 4000 to 13,000 ngl(-1) while the effluent concentrations ranged from 500 to 6,900 ngl(-1). It is eliminated from the waste water with 56-64% during waste water treatment. High OTNE concentrations in sewage sludge showed that the elimination was mainly driven by sorption to sludge. This complies with major elimination in the first settling basins (primary settling tanks) while it was removed to a lesser extent in the aeration basin of the activated sludge treatment or in successive biofilters. The mass flows of OTNE in the influent of the German STPs were between 0.9 and 1.9 g per inhabitant and year. In the annual effluents mass flows of OTNE ranged between 0.2 and 0.8 g per inhabitant which complies with data measured in 13 smaller STPs from Switzerland. The similarity of data suggests that the observed mass flow data might be extrapolated to other European regions.