A QSBR development procedure for aromatic xenobiotic degradation by unacclimated bacteria

The relationship between chemical structure and the comparative rate of biodegradation (defined here as the biodegradation index) by unacclimated activated sludge has been studied. The findings of one model illustrate that the relationship between structure and biodegradability for a homologous series of aromatic compounds may be easily developed using techniques drawn from medical and pharmacological sciences, in this case, Hammett's constants. This is true when the biodegradation pathway is known. However, such a model is not broadly applicable to a diverse group of substances where such pathway information is not available. A second model was developed using a newer technique—molecular connectivity indices—which does not require pathway information. The second model was calibrated with the data employed in the first model. This model did not contain specific pathway or directional information, but successfully predicted the rates at about the same confidence level as the first.