A QSAR-based biodegradability model—A QSBR

A microbial biodegradability predictive model has been developed using groups and molecular indices as molecular descriptors. The model contains 12 variables. The model was calibrated and later validated with a data set developed from biodegradation studies of acclimated activated sludge metabolism. It also successfully predicted the biodegradation rate of several other substances with one exception within the limits established by a study of a second database. This latter study was designed to evaluate the expected scatter in acclimated biodegradation rate data. The nitro group, amines, halogens and heteroatoms severely decrease the rate as do structural complexity and electronic alterations created by most substituents. The carboxyl group markedly enhances the rate but the hydroxyl group has little effect. It appears that the hydroxyl group is significant in acclimation but not in degradation. A discussion of statistical methods and software is included in this work.