Water from Tello River can be used as a raw water to meet the clean water, addressed the needs of Makassar
people. The characteristics of river water are very fluctuate depending on the season especially for its turbidity and Total
Suspended Solids (TSS). TSS in water can be reduced through the coagulation process. The aim of this study was to
determine the pH and the coagulant concentration of papaya seeds which was a best way in reducing the TSS
concentration of sample. Variation in pH was carried out at pH of 1 to 12 by adding 1.0 M HCl or 1.0 M NaOH (with
coagulant concentration of 100% from the initial TSS concentration from the sample). After obtaining the optimum initial
pH of the coagulation process, the optimization of coagulant concentration was continued. The coagulant concentration
variation was carried out at a concentration of 50 to 400% of the initial TSS concentration from the sample at the
optimum pH. The coagulation processes used in this study were rapid mixing at 200 rpm for 4 minutes, slow mixing at 50 rpm for 25 minutes, and sedimentation for 60 minutes. The results of this study found that the pH and the coagulant
concentration optimal at 3 and 150% of the initial TSS concentration from the sample with percent TSS removal of
99.13%. The results of this study prove that papaya seeds were the best natural coagulants because it could reduce TSS
concentrations in the sample approaching 100%.