Zapotillo Viejo Wastewater Treatment Plant, Zapotillo Uno, Sinaloa, Mexico

Zapotillo Viejo is a wastewater treatment plant located in Zapotillo Uno (Zapotillo Viejo), within the municipality of Ahome, Sinaloa, Mexico. The facility serves a population of 1,825 and operates with secondary treatment, meeting standard requirements for small communities in the region. The plant has a designed capacity of 190.08 m³/day and currently discharges 172.80 m³/day of treated wastewater. As a secondary treatment facility, it provides biological treatment to reduce organic matter and suspended solids, aligning with Mexico's official standards for wastewater discharge (NOM-001-SEMARNAT). The treated effluent is discharged into local water bodies that ultimately drain into the Gulf of California, a biologically productive marine ecosystem. The plant plays a role in protecting downstream water quality in the coastal lagoons and estuaries of northern Sinaloa, which support diverse aquatic life and local fisheries.

The plant's discharge enters the drainage network of the Fuerte River basin, which flows into the Gulf of California near Topolobampo. This region includes important coastal lagoons and mangrove ecosystems that provide nursery habitat for fish and shellfish. The Gulf of California is a biodiversity hotspot, and maintaining water quality through secondary treatment helps protect these downstream environments.