Simple method to prolong the closed bottle test for the determination of the inherent biodegradability

A method to prolong the closed bottle test up to 200 days is described and validated. This prolonged closed bottle test has been used to determine the biodegradability of "recalcitrant" and toxic organic compounds. The results obtained in the prolonged closed bottle test are in accordance with those mentioned in the literature on biodegradation of organic compounds in waste water purification plants and on the isolation of microorganisms capable of utilizing these compounds as carbon and energy source. Furthermore, this test may prevent discrepancies and unexplainable results obtained in a 28-day test. The test has the potential to be used as an inherent biodegradability test when recognized by the authorities.