Analysis of simulation tools and optimization of the operational conditions for biofilm activated sludge industrial process

Two simulation tools for industrial wastewater treatment plan using a biofilm activated sludge process are contrasted in this paper; biofilm activated sludge consists of moving bed biofilm reactor followed by conventional activated sludge. Wastewater treatment simulator software (BioWin) and general chemical engineering process software with an integrated mathematical model (Aspen Custom Modeler) are used as simulation tools under different configurations of wastewater treatment plant and influent conditions. The simulated results using BioWin do not fit the experimental concentrations of chemical oxygen demand and total suspension solids from a full-scale biofilm activated sludge process for cellulose and viscose plant wastewaters; however, using Aspen Custom Modeler the simulated results fit adequately. The differences between the two software are explained by the consideration or not of the predation and hydrolysis phenomena in the mathematical model. The trade-off between the models complexity and the goodness in the adjustment of the results shows that in the biofilm activated sludge process the inclusion of predation in the mathematical model becomes essential. The optimization tool included in Aspen Custom Modeler is selected to optimize the operational conditions using three objective functions: minimization of nutrients in the effluent, minimization of sludge production and maximization of excess sludge concentration. Operating cost of the process can be reduced up to 10% considering the optimal conditions proposed by the optimization tool.