Evaluating what is Measured by BDOC and AOC Tests
Batch type biodegradable organic material (BOM) tests are modelled using basic kinetic and stoichiometric principles. The modelling results reveal that for biodegradable dissolved organic carbon (BDOC) tests, the change in dissolved organic carbon (DOC) is not equal to BOM. The formation of soluble microbial products (SMP) and the degradation kinetics of the BOM must be considered to estimate the true BOM from BDOC results. For assimilable organic carbon (AOC) tests, using a calibration standard based on an easy to degrade substrate, such as acetate, does not necessarily give an accurate indication of the true BOM. The kinetics of BOM degradation must be estimated before an AOC test can be used to interpret the true BOM in a sample. The inoculum density can also influence the results of AOC and BDOC tests. When the BOM is hard to degrade, using a low density test can underestimate the amount of BDOC in a sample.