Preparation and Analysis of a Synthetic Polymer Coagulant for the Treatment of Surface Water by Chemical Purification Process

This study addressed the limitations of using inorganic coagulants in the treatment of surface water by evaluating the efficiency of synthetic polymers as coagulants agents in the chemical purification process. The treatment of surface water, entails passing the raw water through a series of treatment units which are usually the low lift pump, aeration unit, filtration unit and disinfection unit. The limitations of inorganic coagulants include; discharge of residual metals into downstream waters, over dependence on pH, high dosage and high sludge production. A synthetic polymer coagulant was prepared by dispersing 1g of cassava starch in 100 ml distilled water, making it up to a litre with hot water (80°C-100°C), adding 1 ml of 1N H2SO4 and electrolyzing by means of a stabilized power supply unit at a current of 0.15 amps using aluminium rods as electrodes. Addition of 1 g of activated carbon to serve as a coagulant aid (Sample A) resulted in a better turbidity removal than the one without the aid (Sample B). Sample A was found to be almost as effective as alum both at neutral and basic mediums causing better than 80% turbidity removal at pH 7 and more than 89% turbidity removal at pH 9 with dosage of 20 ml (20 g) of sample A Synthetic polymer coagulant compared satisfactorily with alum. It gave a maximum turbidity removal of 81.16% while alum gave a maximum turbidity removal of 84.80%. Preliminary cost analysis showed that sample A was more economical than alum.