Chemical oxygen demand removal from wet coffee processing wastewater using indigenous natural coagulants: Optimization through response surface methodology

Abstract

This study was carried out to examine the possibility of treating the wastewater from coffee processing using a number of natural coagulants, both alone and in combination, and also the central composite design (CCD) was used for process optimization. To examine and study the potential treatment of chosen natural coagulants for chemical oxygen demand (COD) removal in the wastewater from coffee processing, a coagulation-flocculation process experiment was carried out. The numerical and experimental optimization system's optimum conditions and outcomes were investigated. A series of batch experiment have been performed for analyzing and optimizing of the coagulation flocculation processes. Based on the experimental analysis, it was found that utilizing a blend of three coagulants—Acanthus sennii C., Moringa stenopetala B., and Aloe vera L., yielded optimal results as a natural coagulant. Under these conditions, the ideal parameters for coagulant dosage, pH level, mixing speed, and mixing time were determined to be 1.25 gL−1, 7, 80 rpm, and 30 min, respectively, in the experimental work. In comparison, the numerical values for these parameters were coagulant dosage-0.750 gL−1, pH-8.76, mixing speed-80.73 rpm, and mixing time-19.23 min, respectively. The COD removal effectiveness under optimal responses from experimental and numerical was about 98.24% and 98.41%, respectively. Even though all coagulants are ideal, it was discovered that employing a mixed kind of coagulant produced better results than using a single type.