Before arriving at our houses, it passes for many steps on Water Treatment Stations, wherein one of them it is used industrial coagulants, mainly aluminum sulphate, in order to reduce the turbidity. Even being much efficient on that process, this coagulant shows many disadvantages, as the production in a large amount of sludge (which is dumped on rivers). It is growing the number of research which looks for substitute industrial coagulants for natural ones. Some published works use extracted polymer from different types of cactus. In order to obtain one simple methodology for water treatment, using a natural product on coagulation/flocculation process, this work uses cactus Mandacaru. The used water on this research was collected from Dourado River, in Currais Novos-RN. The parameters of turbidity and pH in triplicate were analyzed. The obtained results showed that the part of cactus between the core and the shell, named extern part, it showed more efficient. Analyses done for 240 minutes, using 1g of that material obtained reductions in turbidity value bigger than 90%. arriving to value less than 5 UNT, as recommend by legislation. There was no significant alteration in pH values of studied systems. Rural communities will be able to use this methodology in muddy water.