The Processing of crude oil in the oil refinery industry is in dire need of water which is a raw material the processing process. WWTP liquid waste is waste that originates from treatment at the Wastewater Treatment Plant which contains certain characteristics. IPAL PT Pertamina RU IV Cilacap is part of the wastewater treatment unit that produces liquid waste whose parameters are still not in accordance with the quality standards of wastewater. This will have an impact on the environment if it is discharged directly without maximum processing. In this research, the process of liquid water treatment of WWTP Outlets was conducted using a coagulation method using chlorine which aims to reduce the ammonia parameters to comply with the quality standards according to LH PERMEN No.19 of 2010. The study was conducted in two experiments. The first study looked for the most influential variables of dosage, pH and stirring speed. The second study looked for optimal conditions of the required factors. The initial sample conditions before processing were pH 7.5, and ammonia 97.10 mg / L. The first study with namely dosage and stirring speed. pH became a fixed variable then dosage and stirring speed were changed in the second study. Optimal results from the five dose variations (2000, 4000, 6000, 8000, and 10000 mg / L) and stirring speed (150, 175, 200, 225, and 250 rpm) in the ammonia analysis were 1.07 mg / L Based on the results of the analysis of the ammonia parameters, it has fulfilled the quality requirements of wastewater.