Determination of biodegradable dissolved organic carbon using entrapped mixed microbial cells

Several methods for determining biodegradable dissolved organic carbon (BDOC) in water have been developed within the last two decades. However, the problem with most of these methods is the length of time required for the start-up (colonization) and/or determination from days to weeks. In this study, a simple and rapid continuous bioreactor procedure using immobilized cells was developed for BDOC determination. In the first stage of the development, the bioreactors were aerated to ensure that dissolved oxygen was not rate limiting. However, BDOC results obtained from the aerated bioreactors suffered from a large error caused by the release of background dissolved organic carbon (DOC). As a consequence, a different bioreactor scheme, in which the feed (sample) instead of the bioreactor was aerated, was tested. Results show that the feed aerated (FA) bioreactor is a better tool for BDOC determination especially for waters with low initial organic concentrations because of less background DOC released by the immobilized cell systems. Using the FA bioreactor, the accurate and reproducible measurement of BDOC can be achieved within a hydraulic retention time of 3 h, and no start-up period is required.