The purpose of this research is to evaluate the operation of a wastewater treatment system (WTS) in a poultry industry identified as Avícola La Guasima C.A., placed in Carabobo state, Venezuela. The poultry industry benefits 140,000 birds/d and uses a flow rate of 23 L/s. The procedure to carry out the evaluation of the processes that occur in each WTS unit was based on the monitoring of the main constituents of the wastewater and the preparation of a mass balance in the WTS. The monitoring was carried out during three years of operation of the WTS under constant poultry processing conditions, in the company's internal laboratory. The WTS consisted of units, which were a combination of physical operations and biological processes, operating in the following sequence: roughing, homogenization, dissolved air flotation (DAF), activated sludge, rotating biological contactors (RBC) and chlorination. The sludge management units included tanks for separate storage of DAF’s sludge and biological sludge. For the analysis, the monitoring results of each unit of the system were used, considering the elimination of the most significant environmental parameters, constituted by Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD_5,20) and Total Suspended Solids (TSS). The operation of the system was evaluated through a mass balance and the estimation of the efficiency of each flow. The DAF operating efficiency was greater than 70% in the elimination of COD, BOD_5,20 and TSS.. The operating efficiency in the first biological sludge reactor was greater than 85% in the removal of COD, BOD_5,20  and TSS remaining from the DAF unit, the load of solids removed was 333 kg/d. The RBC operating efficiency was greater than 50% in the removal of COD and TSS remaining from the first biological reactor and 71% in removal of BOD_5,20. It can be concluded that the load of contaminants that was removed by the WTS units generated a waste of sludge from the physical process of 1,074 kg/d and biological sludge of 360 kg/d, for a total of 1,434 kg/d, therefore the priority in the operation was the sludge dehydration using belt filter press unit of the sludge generated by the DAF unit. There was a removal efficiency of constituents at the input to the WTS with respect to the output values above 95%. All values are lower than the limits of the environmental regulations specified according to environmental regulation.