T he Semanan area is the center of tempeh industry activities. Tempeh liquid waste contains organic matter, TSS, and high turbidity so it has the potential to pollute the waters if disposed of directly. One of the liquid waste treatments is through coagulation-flocculation and sedimentation processes. The use of natural coagulants is more environmentally friendly, easy to find, and affordable. This study aims to determine the effectiveness of the use of trembesi seeds as biocoagulants in processing tempeh liquid waste so that it is safe if discharged into the environment and the use of liquid effluent as liquid organic fertilizer in encouraging sustainable development. Laboratory-scale studies with dose variations of 0, 10, 20, 30, 50, 70, 100, 500, 600, and 700 mg/L, sample volume500 mL, biocoagulant solution volume 125 mL, coagulation speed 200 rpm with fast stirring time variations of 1, 2, and 3 minutes, and flocculation speed 80 rpm with slow stirring time variations of 15, 30, and 45 minutes. The results showed that the optimum biocoagulant dose of 500 mg / L was able to set aside turbidity by63%. The optimum fast stirring time is 2 minutes and the optimum slow stirring time is 30 minutes. BOD concentration decreased by 78% to 273 mg/L. COD concentration decreased by 40% to 3,840 mg/L. TSS concentration decreased by 66% to 205 mg/L. In reactor sample volume 20 L, biocoagulant solution volume 5L, coagulation speed 100 rpm for 1 minute and flocculation 40 rpm for 10 min. The percentage of allowance for BOD, COD, TSS, and turbidity is 68%, 35%, 58%, and 70%, respectively. BOD, COD, and TSS parameters have not met the quality standards of the Minister of Environment Regulation Number 5 of 2014. The liquid effluent from reactor processing cannot be used as liquid organic fertilizer.