Influence of Variations in pH and Alum Concentrations on Colour and TurbiditY Removal in Raw Water Treatment

One characteristics of raw water is the presence of sediments and suspended particles, alongside dissolved organic matter (DOM). These constituents impart colour and turbidity including pathogens to the water, making it unsafe for human consumption. Coagulation-flocculation is a major step in the drinking water treatment process, allowing the removal of colloidal particles and organic matter which are precursors to potentially carcinogenic disinfection by-products. To provide a practical cost-effective solution to colour and turbidity removal, this work investigated the performance of alum (Al2(SO4)3 at different levels of concentration for the treatment of raw water using the jar test procedure. Each aluminium dose was investigated on a pH level of 6.0, 6.5, 7.0, and 7.5 respectively. The results showed that optimum colour and turbidity removal was achieved at pH 6.5 for which 90 % colour and 70 % turbidity removals respectively were achieved using 90 mg/l alum dose. Above the optimum pH, end turbidity of the water was increased above the residual value for alum concentrations below 90 mg/l, while there was no appreciable reduction in end colour. This study demonstrated that the operating conditions of a water treatment plant can affect its treatment efficiency. It also highlighted the need to investigate the various conditions that could affect colour and turbidity removal in a conventional water treatment process.