Optimization of the Chemical Oxygen Demand Removal from the Rural Domestic Wastewater using Taguchi Experimental Design Method

Abstract

KEYWORD: Taguchi method; orthogonal array design; ANOVA; Signal to noise ratio; ABSTRACT: In the present study, two stages of upflow anaerobic filters (UAF) were applied and the performance efficiency of UAF reactor was evaluated for rural domestic wastewater treatment under different operational conditions such as temperature (T), hydraulic retention time (HRT), acid- ity (pH) and different organic loading rates (OLR). In addition, the optimal chemical oxygen demand (COD) removal and operation factors were determine by using Taguchi experimental design method. An L9 (3 4 ) orthogonal array was selected as the experimental plan for the four parameters mentioned above. The results demonstrated that all the factors had a significant influence on the COD removal efficiency. The obtained results allowed concluding that the optimal conditions in term of COD re- moval were initial pH of the wastewater of 7, temperature of 25 oC, HRT of 1.5 day and OLR of 0.166 Kg. COD/m3.day. Moreover, the results showed that the HRT had highest percentage contri- bution in the COD removal process with 39.92 %, followed by temperature of 33.78%, OLR of 13.75% and the pH of 9.18%. Confirmatory experiments conducted at the optimized conditions and compared with the predicted result show a good agreement. At the end of the experimental study, the UAF reactor operated three months with real domestic wastewater and the obtained COD re- moval results at these optimum conditions was 56.5% with an average final COD concentration of 89.1 mg/l.