The coagulant effect of the prickly pear stalk Opuntia ficus-indica in liquefied form was studied, as well as the synergizing effect of alum, as a method of treatment of domestic laundry effluents. An easy-to-use treatment system was installed at home, which consisted of a 250 L storage tank where coagulation was performed and evaluated by the prickly pear liquefaction with a resting time of 48 h, finally followed by a filtration stage with cotton, stone and sand. The purifying effect (coagulation – filtration) of the prickly pear, Opuntia ficus-indica, was initially evaluated with the first wash rinse of 62.5 L, using amounts of 100 g, 200 g, 400 g and 800 g of the liquefied stalk, compared to the control group. The best result of the effluent purification effect was obtained with the use of 200 g of liquefied prickly pear stalk in 62.5 L of domestic laundry effluent. A system for hom...