Optimization and Modeling of Bio-coagulation Using Pine Cone as a Natural Coagulant: Jar Test and Pilot-Scale Applications

Abstract

Natural coagulants are emerging as effective alternatives to inorganic coagulants in wastewater treatment due to their high coagulation-flocculation activity, abundance, cost-effectiveness, and biodegradability. Despite their potential, research has largely been limited to laboratory-scale experiments, with few studies exploring pilot-scale applications. This study investigates pine cones, a novel and underutilized waste material, as a bio-coagulant for wastewater treatment plants (WTPs). The active coagulating agent was extracted from pine cones treated with a 0.5 M sodium chloride (NaCl) solution. Characterization was performed using Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), and chemical analysis, revealing significant quantities of coagulating agents responsible for effective coagulation. A jar test was initially conducted to determine the optimal coagulant dosage, initial pH, and settling time for the coagulation-flocculation process. The process was modeled and optimized for turbidity, chemical oxygen demand (COD), and phosphate removal using response surface methodology (RSM) with a Box Behnken design (BBD). The optimal conditions identified were a 10 ml/L coagulant dosage at pH 10 and a settling time of 115 min. Experimental data and model predictions showed good agreement, with R² values of 99.12%, 93.52%, and 98.11% for turbidity, COD, and phosphate removal, respectively. Jar tests under these conditions achieved removal efficiencies of 98.81%, 72.02%, and 86.44% for turbidity, COD, and phosphate. The optimized conditions were then applied on a pilot scale, showing removal efficiencies of 97.77%, 71.35%, and 88.6% for turbidity, COD, and phosphate. Our findings highlight pine cones as an effective, cost-efficient, and eco-friendly alternative for WTPs.