Optimization of indigenous natural coagulants process for nitrate and phosphate removal from wet coffee processing wastewater using response surface methodology: In the case of Jimma Zone Mana district

In the developing countries, the coffee production has no controlled disposal of coffee wastewater which has high concentrations of organic and inorganic substances and adversely affects water receiving bodies. This leads to many serious health problems in nearby areas such as ears and skin irradiation, stomach pain, nausea, respiratory problems, and freshwater zone eutrophication. In this study, the coffee processing wastewater were treated by the selected natural coagulant such as acanthus tribe, aloe vera and moringa stenopetala. The goal of this study was to optimize operating parameters on the removal of efficiency of nitrate and phosphate by using response surface methodology. The operating parameters were selected in the range of pH: 3 to 11, coagulation dose: 0.75–1.75 g, mixing rate: 40–120 rpm, and stirring time: 15–45 minutes. Coagulation or aggregation process was experimentally examined by the analysis and survey of selected natural coagulants for removal of nitrate (NO3−), and phosphate (PO43−). Design Expert (11.1.02) was used to statistically analyze the experimental data using ANOVA and the corresponding responses to evaluate the optimal state for the variables. Parameter optimization findings for pH, coagulant dosage, agitation rate, and duration were evaluated. The results of experimental analysis, when the three coagulants were mixed, the optimum conditions for the coagulant dose, pH, stirring speed, and stirring time obtained from the numerical optimization system were 0.750 g, 8.76, 80.73 rpm, and 19.23 min, respectively. The removal efficiency of mixed coagulant of Acanthus tribe, Moringa and aloe vera for NO3− and PO43− were 99.12% and 99.63%, respectively and the more effective coagulants results were obtained in the blended form.