Opuntia ficus-indica (OFI) is a high added value species which different organs are used in several fields, including water purification. The present study intended to treat contaminated well water using naturally prepared coagulant from the cladodes of four local OFI populations in Tunisia. Physicochemical characterization of the water was carried out before and after treatment. The treatment applied allowed to decontaminate the well water studied. Most of the parameters tested were significantly influenced by the "population used" factor. The treatment by the "Amless" population of OFI resulted in the best reduction rates of the contents of Mg, Na, Cu, and Pb. "Loki" population allowed obtaining the best pH and EC reductions. The “Violet” population resulted in the highest COD, BOD5, and TSS reductions. The effectiveness and simplicity of this treatment method would encourage farmers to use it to improve the quality of the well water that is used for irrigation.