Assessment of phenolic compound perturbations of a nitrifier microbial association maintained within a continuous-flow multi-stage laboratory model

To facilitate rapid examination of the environmental impacts of selected mo lecules on cycling processes inherent to aquatic ecosystems, a multi-stage model ecosystem was developed. Nitrification was chosen as the criterion for assessing the inhibitory effe cts of perturbant molecules on a microbial association maintained within th e model. Inhibition of nitrification proved to be a sensitive indicator of both phenol and 2,4-dichlorophenol toxicity. Perturbant compound fate was d etermined by direct analysis and the relationship between residual concentr ation and nitrifying activity was assessed. Phenol, in concentrations of 20 and 60 mg.l(-1), attenuated within the model and it was apparent that low concentrations (<4 mg.l(-1)) must be reached before nitrification proceeded . 2,4-dichlorophenol in concentrations of 10 and 20 mg.l(-1) was found to p ersist and inhibition of nitrification resulted. Biodegradation data of per turbant compounds were, thus, considered important requisites for assessing potential impacts on aquatic environments.