AEROBIC, AQUATIC BIODEGRADABILITY OF LUBRICANTS IN A CLOSED RESPIROMETER: ASTM D6731
EXPLANATION
This test method covers a procedure for determining the degree of biodegradability of lubricants or their components in an aerobic aqueous medium on exposure to an inoculum under controlled laboratory conditions. The test method is an ultimate biodegradation test that measures oxygen demand in a closed respirometer. This test method is suitable for evaluating the biodegradability of volatile as well as non-volatile lubricants or lubricant components. This test method is applicable to lubricants and lubricant components which are not toxic and not inhibitory to the test microorganisms at the test concentration.
Because of the stringency of this test method, low results do not necessarily mean that the test material is not biodegradable under environmental conditions, but indicate that further testing is necessary to establish biodegradability. The water solubility or dispersibility of the lubricant or component may influence the results obtained and hence comparison of test results may be limited to lubricants or components with similar solubilities. The behaviors of complex mixtures are not always consistent with the individual properties of the components.
TEST SUMMARY
Biodegradability is determined by measuring the oxygen consumed when the test material is exposed to microorganisms under controlled aerobic aquatic conditions. This value is then compared to the theoretical amount of oxygen which is required to oxidize all the elements (i.e., carbon, hydrogen, nitrogen, and so forth) in the test material. The test material is mixed with aerobic microorganisms in a closed respirometer containing a defined aquatic medium and measures the biodegradation of the test material by following the decrease in oxygen in the respirometer.
TEST PRECISION
The precision and bias of this test method is not determined as of yet.
