Procedures in ready biodegradability testing: Effects of the inoculation and the monitored parameter

Ready biodegradability tests are often limited because of a lack of definit ion in some operating conditions, which can be critical for reproducibility and efficiency. In this paper, the effects of the monitored analytical par ameter and the variations in the inoculum quantity on test results are stud ied. In a Sturm standardized assay, sodium acetate and dodecylbenzene sulfo nate (DBS) were tested at several initial substrate to biomass ratios (S-0/ X-0). The analytical parameter did show itself to be determinant in the est imation of the extent of the acetate biodegradation. In DBS assays, imposed S-0/X-0 ratios did control both lag time and biodegradation level as well as final carbon distribution in cellular, mineralized and residual carbon. Therefore, quantitative measurement of the S-0/X-0 ratio, or alternatively its setting at a certain value, could enhance the reliability of test resul ts. In order to improve the comparison between different analytical procedu res, a low S-0/X-0 ratio is deemed advantageous. The results of these studi es have implications for the methodology used in biodegradation test system s and suggest caution before utilization of a non characterized inoculum po ssibly leading to erroneous conclusions.