TESTING SURFACTANTS FOR ULTIMATE BIODEGRADABILITY

The development of screening biodegradability tests is briefly reviewe d. The ''new chemicals'' screening methods according to the OECD (1981 ) and the EC (1984) are based upon ultimate biodegradability or minera lization by making use of some analytical parameter which is not speci fic for the chemical. The methods are now known as ''ready biodegradab ility'' tests (RBTs). Screening tests that are specifically designed f or surfactants have been developed by the OECD earlier. In the latter tests primary biodegradation is monitored by means of a specific analy tical parameter. Recent harmonization and improvement of RBTs are eval uated in order to see if their applicability can be extended to screen surfactants for ultimate biodegradability. It is shown that condition s for biotransformation of a surfactant in one of the revised RBTs, i. e. the Closed Bottle Test, are similar or even more favourable than in the screening tests for surfactants. Testing ultimate biodegradabilit y is proposed as a supplement to primary biodegradation of surfactants , at the level of both Screening and Confirmatory. Several revised RBT s were applied to evaluate the ultimate biodegradability of twelve sur factants. Results are in agreement with previous studies and correspon d to validated structure biodegradability relationships for surfactant s. It is concluded that a positive result in a RBT can safely be extra polated to aerobic environments in regions where domestic waste water is processed by sewage treatment plants. The proposed test system excl usively employs standardized methods that are published by the OECD an d EC.