SEDENA Leads Cross-Border Initiative to Revamp Wastewater Plant

The Ministry of National Defense (SEDENA) will oversee the rehabilitation of the San Antonio de los Buenos Wastewater Treatment Plant in Tijuana, Baja California, a project set to benefit residents on both sides of the Mexico-US border.

In January 2024, the governments of Mexico and the United States reached an agreement to construct and rehabilitate the San Antonio de los Buenos wastewater treatment plant. This collaborative effort involves an investment of about US$500 million to tackle the longstanding issue of sewage pollution from Tijuana, which has been flowing into the San Diego Bay, California, causing conflicts among border communities for over a decade.

The project was initially intended to be publicly tendered, but President López Obrador later announced that it would be carried out by SEDENA. The National Water Commission (CONAGUA) allocated MX$630 million (US$37.05 million) to kickstart operations under the ministry's supervision. According to Luis Cresencio Sandoval, Minister of SEDENA, the plant's influence extends over 22 contributing sub-basins, most of which drain into the Tijuana River and ultimately into the United States, necessitating vigilant management in accordance with bilateral agreements.

The San Antonio de los Buenos treatment plant, operational since 1987, initially handled 25% of the municipality's sewage. It was rehabilitated in 2003, and by 2015, it was treating 950 L/second. In 2018, the study "Measurement and characterization of Tijuana wastewater" revealed a significant decrease in flow to 410 L/second.

CONAGUA highlights several deficiencies that are classified as violations of the Mexican Official Standard NOM-001-SEMARNAT-2021, which sets permissible limits for contaminants in sewage discharges. "The treatment capacity is considered zero, which is of great relevance since the plant's reengineering is a commitment established in Minute 328 signed in July 2022 by the Mexican and US sections of the International Boundary and Water Commission (CILA)," says CONAGUA.

Ken Salazar, US Ambassador to Mexico, underscores the crucial role of such projects in enhancing the well-being of both countries' populations. He emphasizes the imperative of environmental protection transcending borders and political cycles. Salazar adds that the United States committed to provide US$300 million for plant repairs.

The plant’s rehabilitation is scheduled for completion by Sept. 30, 2024. Upon inauguration, it will have the capacity to process up to 800 L/second, equivalent to the capacity of the South Bay plant in San Diego.

According to the National Inventory of Municipal Drinking Water and Wastewater Treatment Plants, as of December 2022, Mexico had 1,354 wastewater treatment plants, with 988 operational and a combined installed capacity of 152,130.6 L/second. Sinaloa, Oaxaca, and Jalisco have the highest number of operational municipal wastewater treatment plants, with 264, 183, and 170, respectively, as reported by INEGI. 

As droughts continue to affect the country, effective water management has emerged as a top priority. During the second presidential debate, candidates proposed various measures to address this problem, including implementing a national water plan, promoting water recycling, exploring alternative sources, doubling resources for wastewater treatment, and enhancing regulation of water distribution in the private sector.