DETERMINATION OF PERMANGANATE NUMBER AND HARDNESS IN WELL WATER, DRILLED WELL WATER, AND PDAM WATER. JoPM [Internet]. 2024 Dec. 30 [cited 2026 Sep. 20];1(2):64-72. Available from: https://jurnal-stikesindah.umsu.ac.id/index.php/jopm/article/view/10