The aim of this study was to improve the wastewater treatment plant (WWTP) efficiency of a food industry. Despite the anaerobic-aerobic treatment, the efficiency of the plant is poor because of the high pollutants load derived mainly from the use of disinfectants and sanitizers. These cleaning products are used in the production process. In order to achieve the main goal of the study, the pollutants load reduction was targeted and a physicochemical treatment was added for that purpose. For this effort, the tests were divided in three parts. The first consisted of performing coagulation-flocculation laboratory tests to select the best chemical reagent for reduction of the high load of pollutants present in the influent. The evaluated compounds were ferric chloride, aluminum sulphate, hydroxychloride of aluminum (AHC) and polyaluminum sulphate (PAS). The second was a pilot plant study in which physicochemical and biological treatment werecombined. Finally processes were verified in the WWTP characterizing the effluent and evaluating the process for compliance with standards for reuse water. The results showed that the best coagulant was hidroxichloride of aluminium. Improving the relationship Chemical Oxygen Demand/ Biological Oxygen Demand (COD/BOD(5)) of 0.27 to 0.45 and getting a dose of 1 to 5 mg L(- 1) in the laboratory, which improved to make scaling to plant 0.5 to 2 mg L(- 1) with efficiencies removal of contaminants 98% for COD, 95% for BOD(5), 99% for O&G, to 99% for TSS and helminth eggs were not detect. The wastewater was characterized with cyclic voltammetry and the sludge produced with AHC was analyzed by scanning electron microscopy (SEM) and energy-dispersion spectroscopy (EDS).