Optimizing natural organic matter removal at the Koka water treatment plant, Ethiopia, using soil–alum composite material

ABSTRACT Conventional water treatment methods often fail to remove natural organic matter (NOM), leading to the formation of harmful disinfection by-products in chlorinated water. This study aimed to develop a synergistic, local soil–aluminum sulfate (alum) composite material to enhance NOM removal from real water samples. Locally derived soil (Chalaltu) samples were collected from selected locations and subjected to thermal treatment at elevated temperatures. The thermally treated soil was then combined with alum at varying mixing percentages to create the composite material. The synthesized composite materials were thoroughly characterized using X-ray diffraction, X-ray fluorescence, scanning electron microscopy, Fourier transform infrared, and Brunauer–Emmett–Teller techniques. The alum-treated soil, obtained through thermal treatment at 500 °C with a mixing ratio of 50%, a dosage of 25 mg/L, and a settling time of 25 min, exhibited impressive removal efficiencies. The composite material increased removal efficiency by 1.5 times for both UV254 absorbance (91.1%) and dissolved organic carbon (90%), while reducing the alum dose by 58% compared to the existing Koka water treatment plant process. Reducing alum usage could lead to cost savings and alleviate concerns about its association with Alzheimer's disease. This technique is essential within the context of water treatment technology.