Abstract : The limited clean water in small island is caused by contamination of sea water to clean water sources of society. This study aims to investigate the effectiveness of several methods of brackish water processing to reduce TDS level. This study is one group pretest-posttest design experiment, this study used water processing with coagulation method of Moringa seeds at dose of 350 mg/l, a pumice stone filter with thickness of 60 cm, an activated carbon filter (mangrove wood) with thickness of 60 cm, and combination method of coagulation-filtration in reducing Total Dissolved Solid (TDS) level. The sample of this study was dug well in Barrang Caddi Island, the data were analyzed using the effectiveness formula, Kruskal Wallis test. Brackish water processing with the coagulation method of Moringa seeds showed an average value of the effectiveness in reducing TDS level of 41.38%; pumice stone filtration of 28.82%; activated charcoal filtration was 63.53% and the combination of coagulation-filtration was 54.66% and there was a significant difference in the effectiveness between the four water treatment methods on TDS parameter (p = 0.016).There is fairly good effectiveness on the combination of coagulation and filtration method in reducing TDS level.