The goal of the study was to improve the quality of treated sewage water by removing phosphorus using different chemicals. The researchers tested various coagulants and found that polyaluminum chloride (PAC) was the most effective and cost-efficient in removing phosphorus. The optimal dosage of PAC was 23 mg/L, resulting in phosphorus levels below 0.5 mg/L in the treated water. The study also showed that PAC could remove other pollutants like COD, BOD5, and NH+4-N to some extent. Temperature had minimal impact on the effectiveness of PAC in removing phosphorus.