Optimization of Crab Shell and Cow Bone Blends for Sustainable Bio-Coagulation Treatment of Brewery Wastewater

The brewing industry generates large volumes of high-strength wastewater rich in organic matter, nutrients, and suspended solids, posing significant ecosystem challenges. Conventional chemical coagulants generate high operational costs and toxic residual metal sludges. This study examines the extraction and utilization of sustainable bio-coagulants from fishery and agricultural wastes, crab shell (CS) and cow bone (CB), to treat brewery wastewater via an optimized coagulation-flocculation process. The biopolymers were synthesized and evaluated using Fourier Transform Infrared Spectroscopy (FTIR), Energy-Dispersive X-ray Fluorescence (EDXRF), and X-ray Diffraction (XRD). Spectroscopic analysis confirmed that CS-chitosan functions as a highly crystalline polymer-calcite composite well-suited for charge neutralization and bridging, whereas CB-chitosan functions as an adsorptive carbonaceous-mineral composite. Response Surface Methodology (RSM) based on 4-factor Box-Behnken Design (BBD) optimized process parameters: CS dosage (A), CB dosage (B), coagulation time (C), and stirring speed (D), with Total Dissolved Solids (TDS) reduction as the primary response variable. Analysis of Variance (ANOVA) verified a highly significant quadratic model (R² = 0.9799, p < 0.0001). Individually, CS dosage, time, and stirring speed were highly significant drivers, while CB dosage played a critical supporting role through a significant antagonistic interaction (AB), revealing explicit dosage-dependent synergy. The empirical optimization identified optimal operational conditions: CS dosage of 5.00 g/L, CB dosage of 4.99 g/L, coagulation time of 135 minutes, and a stirring speed of 100 rpm, yielding a maximum predicted and validated TDS reduction of 90.5%. Under these optimized conditions, multi-parameter validation demonstrated high treatment performance: 70.5% TSS removal, 67.0% COD reduction, 65.8% TOC reduction, 85.5% turbidity removal, and complete pH neutralization. These findings validate the blend of crab shell and cow bone as a scalable, circular-economy solution for industrial brewery effluent treatment