Assessment of Biochar Corn (Zea mays) Cob and Coconut Guinit as Media for Treating Public Market Wastewater

Abstract

Public market discharges often enter surface waters untreated, carrying extremely high organic loads and dissolved/suspended solids. Locally abundant agricultural residues, corncob and coconut guinit, offer a potentially low-cost filtration medium, yet remain understudied in market waste applications. This study evaluated a gravity-fed vertical filtration prototype using three corncob biochar masses (≈247, 389, 530 g; corresponding layer thicknesses ~5, 7.5, 10 cm) sandwiched between constant coconut guinit layers downstream of a pebble pre-filter. Raw public market wastewater from Isabela City, Basilan, was passed through each configuration. Effluents were analyzed for Biological Oxygen Demand (BOD), Total Dissolved Solids (TDS), turbidity, and color. The results were compared with the Philippine DENR DAO 2016-08 Class C effluent standards. Maximum mean reductions were 25.7% (to 2,760 mg/L) for BOD, 29.0% TDS (to 5,072 mg/L), 5.3% turbidity (to 60.1 NTU), and 16.0% color (to 17,707 CU). None met regulatory limits (BOD <50 mg/K; TDS <1,000 mg/L; turbidity <5 NTU). One-way ANOVA revealed no statistically significant differences among biochar dosages (p > 0.05). Findings show that inactivated corncob biochar plus guinit media provide only modest polishing of very high-strength market wastewater under short, uncontrolled contact times. Performance might improve through media activation, optimized particle grading, controlled HRT, and integration with biological or chemical pre-treatment. The work establishes baseline data for further development of low-cost, community-scale treatment options using locally available wastes.