Atika, Atika2021-07-152021-07-152020-07wahyu sari yenihttps://repository.unri.ac.id/handle/123456789/10029Improving the quality of groundwater with the addition of coagulation alum and clay of nature using slow sand filters has been carried out Analysis in this study was carried out based on the physical and chemical parameters namely conductivity, pH, ferrous metal (Fe), color / turbidity level of water, phosphate, nitrate and nitrite. Before filtrasion, the average sampel values of conductivity, pH, ferrous metal (Fe), color / turbidity level of water, phosphate, nitrate and nitrite were 557 μS/cm, 5,91 mg/l, 0,11 mg/l, 16,7 NTU, 0,0303 mg/l, 1,2 mg/l and 0,017 mg/l respectively. After filtration , the results showed that the average sample values of conductivity, pH, ferrous metal (Fe), color / turbidity level of water, phosphate, nitrate and nitrite are 489 μS / cm, 4.18 mg / l,.03 mg / l, 0, 3 0.01 mg / l, 1 mg / l and 0.017 mg / l respectively. The results of this study indicate that the slow sand filter method using alum and natural clay can be used to improve groundwater quality.enEffectivenessAlumNatural ClayQualityGroundwaterSlaw Sand FilterArticle