San Luis Wastewater Treatment Plant, Coatepec Harinas, Estado de México

San Luis is a wastewater treatment plant located in Coatepec Harinas, Estado de México, Mexico. It serves a population of approximately 2,738 people, classifying it as a small-scale municipal facility. The plant is situated inland, away from coastal areas, and its operations are part of the local water management infrastructure. The plant provides secondary treatment, which is a standard biological process that removes organic matter and suspended solids. With a designed capacity of 432 m³/day and a current discharge volume of 259.20 m³/day, the facility operates below its full capacity. Under Mexican regulations (NOM-001-SEMARNAT-1996), secondary treatment is required for municipal wastewater to meet discharge standards for receiving water bodies. The treated effluent is discharged into local watercourses that eventually drain into the Balsas River basin, which flows into the Pacific Ocean. The plant plays a key role in protecting downstream water quality and supporting the ecological health of the region's rivers and reservoirs.

The plant discharges into local streams that are part of the Balsas River basin, one of Mexico's major river systems. The Balsas River flows southwestward through the Sierra Madre del Sur and empties into the Pacific Ocean. The watershed supports diverse aquatic life and provides water for agriculture and communities downstream. Proper wastewater treatment is essential to prevent nutrient pollution and maintain water quality in this ecologically sensitive region.