Effects of ferrous sulfate (FeSO4) and poly-aluminum chloride (PAC) during wastewater treatment process at a local beverage company were investigated. Optimum concentrations of FeSO4 and PAC together with the effluent quality in wastewater treatment plant were studied. The application of FeSO4 was examined at different concentration of 6.0 ppm, 6.5 ppm, 7.0 ppm, 7.5 ppm, and 8.0 ppm whereas that of PAC was investigated at the concentrations of 9.0 ppm, 9.5 ppm, 10.0 ppm, 10.5 ppm, and 11.0 ppm, respectively. Physicochemical characteristics of wastewater viz pH, color, dissolved oxygen (DO), total dissolved solid (TDS), total phosphorus, iron, ammonia and chemical oxygen demand (COD) before and after treatment were determined. Ferrous sulfate at the concentration of 7.5 ppm was most effective in removing total phosphorous taken into account the cost effectiveness. At this concentration, the effluent compliance in terms of pH, color, DO, TDS, total phosphorous, iron, ammonia and COD was obtained based on the standard value of Ministry of Environment in Cambodia. Similar compliance of effluent quality was achieved at poly-aluminum chloride optimum concentration of 10.0 ppm during which phosphorous flocculation in wastewater treatment plant was accelerated.