Rancho Viejo Wastewater Treatment Plant, Aguascalientes, Mexico

Rancho Viejo wastewater treatment plant serves the small community of Rancho Viejo in the municipality of San José de Gracia, Aguascalientes, Mexico. With a population served of 365, it is a small-scale facility designed to handle local domestic wastewater. The plant is situated in an inland area, far from coastal zones, and operates under Mexico's national water regulations. The plant provides secondary treatment, which is appropriate for its small population size. Its designed capacity is 86.40 volume units, and it currently discharges 34.56 volume units, indicating it operates below capacity. As a small agglomeration, it falls under Mexican wastewater standards (NOM-001-SEMARNAT-1996 and subsequent updates), which set discharge limits for pollutants based on receiving water body type. The treated effluent is discharged into local water bodies that eventually drain into the Gulf of Mexico via the Lerma-Santiago basin. The surrounding region is semi-arid, making water quality management important for local ecosystems and downstream users. The plant helps protect the local watershed from untreated sewage, supporting aquatic life and agricultural water reuse downstream.

The plant discharges into the Lerma-Santiago basin, which flows through central Mexico and ultimately reaches the Pacific Ocean via the Santiago River and Lake Chapala. This watershed supports diverse aquatic habitats and is a critical water source for agriculture and communities. The semi-arid climate means that maintaining water quality is essential for ecosystem health and human use.