Cactus has shown great capabilities as a bio coagulant/flocculent in the treatment of wastewater and as a factor for sustainable development of the environment, due to its abundance and non-toxicity for human health. This has encouraged the present study based on the design of experiments to optimize the two operating factors: the bio coagulant dosage and initial pH. The effect of these considered factors on turbidity and chemical oxygen demand (COD) reduction performances was investigated to treat sewage wastewater from plants by the coagulation/flocculation process using the response surface methodology (RSM) based on a central composite faced design (CCFD). The effect of the pH on the supernatant turbidity removal and the COD reduction was very significant whereas that of the coagulant dosage was insignificant on the COD removal efficiency. Experimental results revealed that the maximum reduction of turbidity and COD could be reached at a coagulant dosage of 28 mg/l and a pH of 12. At these optimal conditions, the removal efficiency of turbidity and COD was 98.33% and 96.55% respectively. By the end of the treatment, final values of 0.84 NTU and 20.8 mg/l were obtained for turbidity and COD, respectively. A notable decrease of orthophosphate (O- PO4-2), nitrite (N-NO3-), ammonium (N-NH4+) and suspended matter (SM) was observed. The study also showed that the quadratic regression model could be used as a theoretical basis for the process based on a high coefficient of determination R2 value > 0.96, obtained from the analysis of variances (ANOVA).
Keywords: Analysis of variance; Bio coagulant; Response; Sustainable development; Wastewater.