The researchers studied the Sg. Serai Water Treatment Plant to improve the treatment of water with low turbidity. They tested different coagulants and doses to find the best way to remove particles and meet water quality standards. The raw water had low levels of TOC and color, requiring pre-treatment for pH correction and softening. The small colloid particles in the water made it hard to optimize the coagulation process. They found that using alum at 15 mg/L removed 96.5% of turbidity, while PAC at 5 mg/L removed 64.1%. pH levels and pre-treatment affected the efficiency of the coagulants.