Ronny, Ronny, Irfai Irfai, Dedi Mahyudin, and Jasman Jasman. 2019. “Banana Stem Charcoal As Adsorbents Reduce Water Hardness Levels”. International Journal of Environment, Engineering and Education 1 (1):1-6. https://doi.org/10.55151/ijeedu.v1i1.7.