Optimizing poly-aluminium chloride coagulation in rural water treatment: the critical role of sodium hydroxide in residual aluminium control

ABSTRACT Water treatment facilities in rural areas often face operational and resource limitations. Coagulation and flocculation are essential processes in water treatment, with pH being a critical factor influencing the performance of coagulants. Poly-aluminium chloride (PAC) has been widely recognized for its effectiveness in removing turbidity, colour, and residual contaminants. Current research lacks sufficient focus on its use under rural treatment plant conditions where operational constraints, fluctuating water quality, and limited process control are common. This study addresses that gap by investigating the optimum pH for potable water treatment using PAC at the Tapah Water Treatment Plant. Sequential laboratory-scale jar tests were employed using a one-factor-at-a-time approach to evaluate PAC dosages (25–35 mg/L) and sodium hydroxide (NaOH) adjustments (3–18 mg/L) towards the water quality. Optimal coagulation was achieved at pH 7.0 with a PAC dosage of 31 mg/L and NaOH dosing of 9–12 mg/L, resulting in a final treated water turbidity of 3.6 NTU and residual aluminium concentrations of 0.13 mg/L. This research affirms the significance of adjusting pH for efficient water treatment to become drinkable and still meets the National Drinking Water Quality Standards. The results offer useful information for enhancing efficiency and water quality in water treatment facilities in rural and suburban settings.