Owing to economic advantages in addition to the potential for improved process robustness and to reduce the pollution load on the environment, particularly in water treatment applications in developing countries, an investigation with biodegradable and eco-friendly naturally occurring seed gum as coagulant was undertaken. Naturally occurring Cassia angustifolia (CA) seed gum was evaluated against the chemical coagulant polyaluminium chloride (PAC) for its coagulation ability to remove colour from synthetic dye solutions. Three groups of dyes: Acid Sendula Red, Direct Kahi Green and Reactive Remazol Brilliant Violet were chosen for the case study. For optimum results the variables studied were pH and dosage. CA was found to be a good working substitute alone or in conjunction with a very low dose of PAC for decolourisation of acid and direct, but not for reactive dye solutions. The performance of PAC was better with direct dye and that of CA was better with that of acid dye.