Introduction. Construction and maintenance costs represent a primary aspect in the design and construction of wastewater treatment plants. Objetives. Design and quote a wastewater treatment plant in the rural area of Riobamba canton, taking the Santiago de Calpi Parish Head as a point of analysis to avoid contamination to the Chibunga River. Methodology. Compound sampling was used for the characterization of wastewater, it was shown that Fecal Coliforms, Suspended Solids, Surfactants, Oils and Fats, Biochemical Oxygen Demand (DBO5), Chemical Oxygen Demand (DQO) and Turbidity were the parameters that were consider for the elaboration of the plant design, data compared with the regulations of the Unified Text of Secondary Environmental Legislation of the Ministry of the Environment (TULSMA). Results. The treatment plant is projected for 20 years for a population of 1,887 inhabitants and with a flow of 1,479.6 m3 / day. The system consists of a channel, manual cleaning grating system, a primary settler, an activated sludge tank that goes together with a secondary settler, a disinfection tank, it should be emphasized that the sludge generated in the settlers needs treatment and is proposes 4 drying beds. When carrying out this purification process, results are obtained with a BOD5 37 mg / L, COD 59 mg / L, Suspended Solids 2 mg / L, Surfactants 0.4 mg / L, Oils and Fats 0.2 mg / L and Coliforms fecal ˂ 2 CFU / 100ml, these results are in accordance with the TULSMA, book VI, Annex 1, table 9 - Discharge into a body of Fresh Water. Conclusion. The total price of the wastewater treatment plant is $31699,40 considering good quality materials for its construction, extending the useful life of the equipment and of the plant.