Perancangan Sistem Pengolahan Air Bersih untuk Melayani Fakultas Ilmu Keperawatan Universitas Indonesia dengan Slow Sand Filter Bermediakan Pasir Silika dan Karbon Aktif yang Efektif dalam Menghilangkan Parameter Besi, Mangan, dan Fekal Koliform = The Design of Water Treatment System Contains Slow Sand Filter with Silica Sand and Activated Carbon Known Effective to Reduce Iron, Manganaese, and Fecal Coliform Concentration to Serve the Faculty of Nursing in University of Indonesia