The results of many years of systematic monitoring of the Rhine River demonstrate a dramatic decline of more than 90 percent in the volume and concentrations of LAS and almost all detergent-related substances, according to Germany’s Henkel KGaA.
Two factors are held primarily responsible for the decline: 1) the higher ecological quality of the detergents and their ingredients, and 2) the quantitative and qualitative improvement of waste water treatment. High rates of biodegration also were cited.
The Rhine study, involving some 140 sampling points along the river and its major tributaries, was supplemented more recently bu studies of the Rur and other smaller rivers receiving considerable volumes of sewage, often reflecting “worst case” values. The results were equally encouraging, showing predicted no-effect concentrations (PNEC) for LAS of between 0.09 and 0.24 ppm, considerably below the “critical” limit of 1.0. This demonstrates that LAS (and other surfactants) present no ecotoxicological risk and “no cause for concern,” according to the study.1
The Henkel reports conclude that “the concentrations of all surfactants in the aquatic environment are very low (<6µg/1)… (and) are of no immediate concern.”
The Rur study indicated that more than 90 percent of LAS was successfully eliminated in treatment facilities, confirming the findings of the ERASM2 studies in five European countries, which found an average eliination rate of 99.2 percent. The Rur study also found that colder temperatures appeared to have no effect on surfactant concentrations.
Moreover, rates of biodegration of LAS and other surfactants in river water were found to be rapid. Halflives, the time required for half the surfactant to biodegrade, was found to be 1-3 hours.
1. The Rhine and Rur studies were described in detail by Dr. F.R. Schröder in Tenside Det. Surf., 32 (1995) 492-497, SOFW Journal, 121 (1995) 420-427.
2. Environmental Risk Assessment Steering Committee of AIS/CESIO (J. Waters and T.C.J. Feijrel, Chemosphere 30 (1995) 1939-1956.