Removal of pollutants from coffee Processing wastewater using indigenous natural coagulants: optimization through Response Surface Methodology (RSM

Abstract

In coffee - producing countries, the uncontrolled disposal of coffee wastewater effluent is a significant concern because it shows a high concentration of suspended solids, organics, organic and inorganic matter, nitrate, phosphate and produces adverse effects on the receiving bodies of water. This causes many serious health problems among residents of nearby areas, such as spinning feeling, eye, ear, and skin irritation, stomach pain, nausea, breathing problems, and forms eutrophication on freshwater zone. This study conducted to investigate the coffee processing wastewater effluent potential treatment of selected natural coagulants Acanthus stem, Aloe Vera, and Moringa stenopetala individually and in the blend form within the framework of central composite design- response surface methodology (CCD-RSM) for the optimization process. Grap/hand sampling technique used, and Jar test conducted to evaluate coagulation ability by varying design parameters such as pH (3.0, 7.0, and 11.0), coagulant dosage (0.75,1.25, and 1.75g), stirring speed (40,80,120rpm), and stirring time (15, 30 and 45 min). Coagulation - flocculation process experiment conducted to analyze and investigate the coffee processing wastewater potential treatment of selected natural coagulants in terms of color, turbidity, COD, 𝑁𝑂3,and 𝑃𝑂4 3_ removal. Design expert (11.1.02) was used for statistically analyzing the experimental data with ANOVA and to evaluate the optimum condition or value of both process factors with respective responses. Optimum conditions and responses from the numerical and experimental optimization system for pH, coagulant dosage, agitation speed, and agitation time were studied. Therefore, according to the experimentally analyzed result, the optimum conditions obtained from the numerical optimization system for coagulant dosage, pH, agitation speed, and agitation time were 0.750g, 8.76, 80.73rpm and 19.23min respectively when the blended form of the three coagulants namely, Acanthus stem, Moringa powder, and Aloe-vera used as a natural coagulant. Under these optimum responses from numerical optimization, about 99.99%,98.70%, 98.41%, 99.12% and 99.63% for Color, Turbidity, COD, 𝑁𝑂3 ,and 𝑃𝑂4 3_ removal efficiency was obtained respectively. Even if all coagulants are best, the more effective result was found using the blended form of coagulant for coffee effluent treatment over the individual.