In order to verify the operation of the NSDC company's industrial water treatment plant and to optimize the quality of the liquid discharges by coagulation and flocculation, we carried out the physico-chemical characterization of these liquid discharges and optimized the elimination of the organic matter. The results show that the abatement rate of the parameters SM, COD and BOD5 of the step are respectively 67%, 66% and 89% during November 79% 81% 89% during December and 69% 82% 89% during January. The treated wastewater showed that the WWTP is working properly, but in the coagulation flocculation treatment step instead of using a large amount of Dekfloc alone, we tried to optimize the dose of a plant powder as bio flocculant injected with DEKFLOC as coagulant, which will increase the removal rate of organic matter. The tests of coagulation flocculation show that the application of the combination between DEKFLOC and the powder of the cactus allows to increase the rate of abatement of COD to 54%, of BOD5 to 67%, of TSS to 80%, and therefore the reduction of microorganisms.