Residual waters generated by the different industries are a cause of contamination for natural bodies of water, and for that reason it is necessary to treat these waters to reduce their level of impurity and comply with existing laws for their discharge. In the 2003, a residual water treatment system was installed at EARTH University’s academic center, the Food Processing Laboratory (LPA) that processes fruits, vegetables and meat products. The components in this system include a solids separation tank, a tank for separation of fats, a flow equalization tank, an aeration tanks with activated sludge, a sedimentation tank and two constructed wetlands. In 2007, a second center, the Dairy Products Plant (PL), was constructed. The system for treatment of their residual waters consists of a tank for separation of fats, the effluent of which empties into the flow equalization tank of the LPA treatment system. In a diagnostic of both systems, sampling was conducted at three points, the tanks for separation of fats at PL and LPA and the effluent of the sedimentation tank, once a week for a total of four months. The following variables were analyzed in each sample: physical (temperature; solids in suspension, deposited and total; and turbidity), chemical (pH, DBO₅, DQO, nitrate, ammonium and phosphate) and biological (microorganisms). The results indicated removal efficiencies of 68 % for solids, 95 % for DBO₅ and 90 % for DQO. In general, the effluent from the sedimentation tank met the discharge requirements as dictated by the law, indicating that the constructed wetlands are not essential for further treatment and discharge of the residual water. In conclusion, the treatment system is efficient in its operation; however, the implementation of a solids separation tank is recommended for PL. In addition, it is highly recommended to have a management plan for infrastructure maintenance and operation for this residual water treatment system.