Paper Title
The Study on The Effect of Chemical Coagulation by Jar Test on Water Supply Quality in Winter Season and Cost Estimates Throughout The Water Supply Treatment Cycle Case Study of Phichit Provincial Waterworks Authority, Thailand

Abstract
The research studied of pH effect on chemical precipitation processes in water supply using the jar test method. The study was water production process at the Phichit provincial waterworks authority in winter season of Thailand. The period of study was mid of October 2018 to mid of February 2019. The raw water was sampling at Nan River in water production process at Phichit site. The range of turbidity of raw water was 12 NTU to 91.7 NTU and the pH of raw water was 7.95 to 8.10. The adjustment of pH of raw water using H2SO4 and NaOH was studies. The result found that the best of flocculation conditions process made in pH of raw water was 8.5. In pH 8.5 of raw water studied found that the optimum dose of Poly Aluminum Chloride (PACL) during the turbidity test was 5 to 15 ppm. Two of water quality parameters were turbidity and color has decreased at pH 8.5 of raw water. The efficiency of turbidity removal was 11 % to 40 % and the color removal was 33 % to 67 %. The nine of water parameters; pH, temperature, conductivity, alkalinity, total hardness, calcium, chloride, Iron (Fe) and manganese (Mn) were not different of data when pH adjustment. Chemical cost of PACL and NaOH at pH 8.5 was 0.66 to 0.80 Baht per m3 of water supply. The equation of turbidity of raw water (X) and optimum dose of PACL (Y) was Y = 0.2218X + 5.8265 Index Terms - Water supply, Phichit provincial waterworks authority, jar test, poly aluminum chloride , efficiency of removal