Sulfide Precipitation Process Optimization of Turbidity Removal from Artisanal Gold Smelting Wastewater via Box-Behnken Design Model

School of Chemical, Biological, and Materials Engineering and Sciences, Mapúa University, Intramuros, Manila 1002 Philippines

^* kgnquiton@mapua.edu.ph

Abstract

Addressing the turbid waters of the Marilao-Meycuayan-Obando River System (MMORS), this study addresses the challenge of excessive turbidity in wastewater samples collected from Meycauayan City, Bulacan, observed to surpass US EPA standards. Turbidity levels were assessed using a Portable Eutech TN-100 Waterproof Turbidimeter, with an initial reading of 137 NTU, exceeding the US EPA standards. Three parameters—pH level, precipitant dose, and stirring speed—were investigated for their impact on turbidity removal efficiency. Employing Response Surface Methodology with Box-Behnken Design (RSM-BBD), stirring speed emerged as the most influential factor (p = 0.04111), with optimal conditions identified through RSM-BBD analysis (pH 8.6, 0.5 g L^-1 precipitant dose, and 120 rpm stirring speed), resulting in 99.18% turbidity removal efficiency. Subsequent trials confirmed consistent turbidity removal exceeding 99%. Therefore, the study underscores the efficacy of batch sulfide precipitation in sustainable water management and promotion of turbidity removal in addressing the toxicity levels inherent in industrial wastewater.