An Original Theoretical and Experimental Approach to Biopolymer-Based Coagulation-Flocculation Systems for Drinking Water Purification in Rural Northern Nigeria

The provision of clean drinking water in rural communities of northern Nigeria is constrained by the limited availability and cost of synthetic coagulants such as aluminium sulphate, which require chemical expertise and supply chains unsuited to remote settings. Biopolymer-based coagulant-flocculants derived from natural plant sources offer a sustainable alternative, but their fundamental coagulation chemistry, application optimisation, and performance boundaries under the specific raw water quality conditions of northern Nigeria have not been established through rigorous scientific investigation. This study developed an original theoretical and experimental framework for biopolymer-based coagulation-flocculation of typical northern Nigerian raw water sources characterised by high turbidity from harmattan dust and seasonal variation. Coagulant materials were extracted and characterised from three plant sources common in North West and North East Nigeria: Moringa oleifera seeds, Dolichos lablab beans, and Cassia obtusifolia seeds. Coagulant active components were isolated and characterised by sodium dodecyl sulphate polyacrylamide gel electrophoresis, dynamic light scattering, and zeta potential measurements. The coagulation mechanism was investigated through systematic jar tests combined with colloid stability measurements, fractal dimension analysis of floc structures, and surface complexation modelling of the biopolymer-particle interaction. An original kinetic model incorporating charge neutralisation, adsorption-bridge flocculation, and sweep flocculation contributions was developed and parameterised for each plant-derived coagulant. Moringa oleifera seed extract achieved 97.8 percent turbidity removal at an optimal dose of 8 mg/L across typical northern Nigerian raw water compositions. The theoretical framework reveals the dominant bridging flocculation mechanism and provides design equations for dosing optimisation. This original contribution advances the scientific foundation for biopolymer water purification technology deployment in northern Nigeria.

Keywords: biopolymer coagulant, Moringa oleifera, drinking water purification, coagulation mechanism, northern Nigeria