Liani, RahmaBudijono, Budijono2021-03-122021-03-122019-11978-60251349-1-3wahyu sari yenihttps://repository.unri.ac.id/handle/123456789/9955Most of the Bengkalis areas are peatlands which save a very large quantity of water, but the quality is low, so that its use is limited to fill clean water needs or to support fisheries activities. Many studies have shown alum coagulant and PAC (poly allumunium chloride) can improve the low quality of peat water, but the finding of the coagulant dose partially or in different mixtures that are highly dependent on the characteristics of peat and limited reported the coagulant is available in a practical package. The aims of this study is to determine the quality of peat water coming from the island of Bengkalis in the range of pH 2 - 6 with a dose of lime mixture of 0.5 gL- 1, alum 0.34 gL-1 and PAC 0.56 gL-1. The research was conducted in March-October 2019 at the FPK Waste Management Laboratory, Riau University, using the experimental method. The processed peat water was tested by bioindicator Chlorella sp. Water quality parameters observed were pH, color, organic matter, turbidity, temperature, CO2 and growth of Chlorella sp. The results have shown a mixture of lime 0.5 gL-1, alum 0.34 gL-1 and PAC 0.56 gL-1 could increase the conditioned pH from 2-6 to 6-9 and a decrease in color from 1441 TCU to 39.7-154.7 TCU, turbidity from 24.2 NTU to 1.72-4.08 NTU and organic matter from 520.2 mg / L to 23.6-28.7 mg / L and abundance of Chlorella sp. increased from 224,000-308,000 cells / ml to 1,296 x 106 -1,648 x 106 cells / L. It was concluded that the mixture of lime thor, alum and PAC was able to improve the quality of Bengkalis peat water with a pH of 2-6 and suitable to fill the needs of clean water and fisheries activities.enacid watercalsium carbonatcoagulant and pHArticle