Prediction of suspended and attached process behavior in anaerobic batch reactor using nonparametric regression model approach based on spline estimator

Anaerobic digestion is sequential complex process and difficult to predict its behavior. Performance of suspended and attached growth in anaerobic batch reactor are studied in this paper. Behavior of those process is applied to treat tofu wastewater in 30 days of contact time. To predict reactor behavior in both processes, we can use spline estimator that has power full and flexible properties in nonparametric regression model, because it can accommodate locally behavior that is showed by optimum knots. In this paper, we interest to predict behavior of COD concentration between suspended process and attached process. The results show that in 30 days of contact time, the behavior of COD concentration in suspended process is more fluctuate showed by number of knots (i.e., has 5 optimum knots) than those attached process (i.e., has 3 optimum knots). In suspended process, the highest both for decreasing and increasing of COD concentration are happened in contact time intervals (in day), 3-6 and 15-18, respectively, and in attached process, those are occurred in contact time intervals (in day), 0-9 and 24-27, respectively.