This Test Guideline describes the modified MITI test (II). This test permits the measurement of the Biochemical Oxygen Demand (BOD) and the analysis of residual chemicals in order to evaluate the inherent biodegradability of chemical substances which have been found by the Standard MITI Method (I) to be low degradable.

An automated closed-system oxygen consumption measuring apparatus (BOD-meter) is used. Chemicals to be tested are inoculated in the testing vessels (six bottles with different quantities of test chemical) with micro-organisms. In order to check the activity of the inoculum, the use of control substances (aniline, sodium acetate or sodium benzoate) is desirable. During the test period, the BOD is measured continuously. Biodegradability is calculated on the basis of BOD and supplemental chemical analysis, such as measurement of the dissolved organic carbon concentration, concentration of residual chemicals, etc. The BOD curve is obtained continuously and automatically for 14 to 28 days. After the 14 to 28 days of testing, pH, residual chemicals and intermediates in the testing vessels are analysed.