In the present investigation the influence of the temperature and microbial concentration of Bacillus sp. on the biodegradation of fats and oils from the wastewater of Tanneries - Rolemt. in the riverside stage. The Bacillus sp. strain was isolated and identified of the grease trap of a chicken. The tests for the biodegradation of commercial oil were carried out, with a bifactorial design of three levels with three repetitions: temperatures of 25 °C, 30 °C and 35 °C; and cellular concentrations of 1.5 x 108, 3x108 and 6x108 CFU/ml. obtaining the optimum conditions of 35 °C temperature and 6x108 CFU/ml. of bacterial concentration at 72 hours of incubation. In the Treatment of the residual water of tannery, it was possible to remove the fat at 100%, since its maximum concentration was 4549 ppm. and the dosage was ready to degrade 50,000 ppm