The combined CO2/DOC test - a new method to determine the biodegradability of organic compounds

The OECD Guidelines for Testing of Chemicals (OECD, 1993) offer a variety of methods to determine the biodegradability of chemical compounds. The determination of the ready biodegradability, in particular, plays a crucial role in the ecological characterization of substances. Nevertheless, for the methods based on DOC removal it is difficult to differentiate clearly between physical/chemical elimination and microbial degradation. Therefore, the combined CO2/DOC test was designed, which offers the opportunity to simultaneously follow the DOC removal and mineralization of a compound. The new method was optimized with regard to the properties of the medium and inoculum concentration and compared with the manometric respirometry test (OECD 301 F) and the Zahn-Wellens test (OECD 302 B). The results obtained show that the combined C02/DOC test provides reliable results and gives enhanced information on the biodegradation pattern of a chemical compound.