The need for clean water is increasing along with the rising population. Water use in developing countries still relies on surface water such as groundwater, which is very easily contaminated by the surrounding environment. The coagulation method for water purification is usually used to remove colloidal residues and assist the coagulation-flocculation process using aluminum sulfate, which can be harmful to health if used for a long time. The coagulation method utilizing natural coagulants such as proteins and tannins is better used because it is cost-effective and relatively safer for health if used for a long time. Tests on the tannin and protein content in the natural coagulant, as well as characterization using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM) on the water sediment after the coagulant is added, are conducted. The groundwater sample that did not meet the physical, chemical, and biological criteria was chosen as the water sample. Moringa oleifera seed powder and Acanthus ilicifolius leaves were added to the water sample at doses of 0.025 g/L and 0.05 g/L, respectively, and then allowed to settle for 30 minutes. Subsequently, tests were conducted to determine the optimum pH, COD, BOD, TSS, TDS, and the number of E. coli bacterial colonies were conducted. The natural coagulants used were proven to reduce COD by 38%, BOD by 52%, TSS by 78%, and TDS by 62%, and to remove 92% of the total E. coli bacteria. FTIR analysis showed that the natural coagulants used contained -OH and C=O functional groups, indicating the presence of natural coagulant molecules.