Calculus of the Biochemical Oxygen Demand of effluents with xenobiotics

This paper describes the kinetic equations for the Biochemical Oxygen Demand (BOD) of urban and industrial wastewaters for the 1st, 2nd and nth order reactions. Industrial wastewaters contain products extraneus to nature, xenobiotics, which alter the biodegradation activity of microorganisms, impeding their activity for an initial period of time and changing the mechanism of biodegradation, thus disabling the traditional calculation of the BOD. For effluents with xenobiotic substances, the concept of Equivalent BOD5 is introduced, BOD5+I. The kinetic equations of Biochemical Oxygen Demand delayed by the effective acclimation time of microorganisms are presented. The kinetic equations with delayed activity developed here are applied to the effluents of a paper recycling plant, a textile-dyeing factory, and a river into which flow the treated wastewaters of urban and industrial areas.