Comparison of biodegradability assessment tests for chemical substances in water

Assessment of biodegradability of specified compounds or wastewaters is an important guide to estimate their behavior in natural aquatic environment. Multilevel protocol for biodegradability assessment was proposed in the European Union to unify tests in different European countries. The protocol begins with tests for ready biodegradability, which are follosed by inherent biodegradability tests and the multilevel protocol is completed with simulation tests. The three-level tests are differentiated by procedure, concentration of test compound, amount and source of inoculum used. The comparisons of biodegradability tests, one standardized from zero level and one standardized from level one and their non-standardized modifications were made for different test substances to estimate the differences between them and to estimate the meaning of multilevel biodegradability testing. It was pointed out that, due to various biodegradation testing levels, differences between test results occur. The main ones are: the lag phase, the biodegradation rate and the final level of biodegradation.