CRITICAL-ASSESSMENT OF THE OPERATOR-SPLITTING TECHNIQUE IN SOLVING THE ADVECTION-DISPERSION REACTION EQUATION .2. MONOD KINETICS AND COUPLED TRANSPORT

In the first manuscript of this two-part series, the behavior of the i nherent time-lag error in the operator-splitting technique has been di scussed. However, the discussion has been limited to the advection-dis persion-reaction equation with first-order kinetics. In this manuscrip t, the discussion is extended to address the applicability of the oper ator-splitting technique in solving the advection-dispersion-reaction equation with Monod kinetics. The discussion also considers the two-sp ecies coupled transport problem. The results of the analysis show that the behavior of the time-lag error causing a mass balance error is ra ther similar to those observed with first-order kinetics. The time-lag error directly depends on the reaction rate, and hence, affects the o xygen equation due to the high rate of oxygen consumption. Also, the a lternate operator-splitting scheme shows a greater accuracy compared t o the normal operator-splitting technique. Upon observing such similar ities, a concept of equivalent first-order reaction rate is derived. T he equivalent reaction rate has been found to be extremely useful for predicting the time-lag error of the single- and two-species mass tran sport with Monod kinetics using the result of the first-order reaction problems obtained in the first manuscript.