Nephelometric Performance Evaluation of Oxidized Starch in the Treatment of Coal Washery Effluent

This study investigated the coag-flocculation performance of oxidized starch coagulant (OSC) and its blends with alum and FeCl3 in removing turbidity from coal washery effluent at room temperature. A conventional laboratory bench-scale jar test apparatus was employed for the experiments. Coag-flocculation parameters such as reaction order α, rate constant K, coagulation time τ, etc. were determined. The optimum pH was observed at 4.0, while the blend of 30.0 mg/L FeCl3 and 250.0 mg/L OSC achieved the optimum turbidity removal. Turbidity removal efficiency was recorded between 96.0% and 99.9% for various dosages and pH studied. The coagulation rate constants, K recorded range from 9.393 × 10-5 L/mg.min to 8.294 × 10-1 min-1, while coagulation periods τ, range from 3.8 s to 235.7 s for various dosages and pH studied. The use of OSC blended with FeCl3 showed high level of efficiency, for the treatment of coal washery effluent.