Fitria, YeniMuhdarinaNurhayati2016-05-162016-05-162016-05-16wahyu sari yenihttp://repository.unri.ac.id/xmlui/handle/123456789/8384Clay is one of the natural wealth that has been used as a liquid coagulant in water treatment. Natural clay can be used as a liquid coagulant caused the content of its aluminum and iron able to bind colloidal particles, organic matter and other impurities in the water. Liquid coagulant was made using natural clay on calcined at 700°C for 3 hours. The next step was leaching at 100°C for 2 hours using sulfuric acid extractor with a concentration of 0,4 mol. Liquid coagulant obtained was used in coagulation process Siak river water and analyzed several parameters such as color, pH, turbidity and organic matter content. The results of analysis parameters was compared to PERMENKES No.416/MENKES/PER/IX/1990 about "Requirements and Water Quality Control". KCS0,4 as a liquid coagulant was effective to improve the parameters of Siak river water.encoagulationliquid coagulantSiak riverstudent Paper Post Degree