Design and operational aspects regarding the utilization of activated sludge processes for the treatment of both toxic and nontoxic organic wastes are presented; a key component of the technology concerns the application of a kinetic model which has been shown to be effective for predicting process performance for activated sludge systems treating such carbon sources. After developing an acclimated biomass which is capable of degrading a particular waste, it is prudent to determine the nature, inhibitory or noninhibitory, of the microbial growth rate equation as a function of exogenous substrate concentration. For noninhibitory wastes, one can employ the Monod function for relating µ to S; however, inhibitory wastes require the use of an inhibition function such as the Haldane equation; methods and analytical considerations regarding the evaluation of the biokinetic constants are discussed. The design and operational equations for activated sludge systems treating toxic compounds are developed. Analysis of these equations underscores the significance of the critical, or peak, growth rate, µ*, which is characteristic of systems treating inhibitory wastes. If this growth rate is exceeded in continuous flow units treating toxicants, rapid effluent deterioration and reactor failure can occur; this can be demonstrated analytically and has been verified in pilot plant studies. The predictive power of the model for establishing the critical operating conditions in activated sludge systems is also discussed.

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