in San Luis Potosí, treated wastewater irrigates crops

San Luis Potosí. A city of about 1.3 million people located in an arid region of Mexico, north of Mexico city. As in the rest of the country, the population is growing and so is its need for water, while groundwater and river levels are becoming increasingly worrying. Not to mention the frequent interruptions to supply and the many leaks in the network.

The country must react quickly in response to this troubling situation of water stress, which compromises access to water in the medium and long term. The measures adopted to fight against water shortages include reusing wastewater in industry and agriculture. SUEZ, the leader in the wastewater recycling market in Mexico, has joined forces with a local consortium and a Japanese company to build a new treatment plant 1 able to recycle the 80,000 m3 of wastewater produced by the city of San Luis Potosí. Of the total volume of treated water, the plant discharges 57% after primary treatment 2 into a lagoon before using it for crop irrigation 3 . The remaining 43% is redirected to secondary and tertiary treatments 4 for industrial needs and more particularly to supply water to a power plant 5 .

Thirteen years after it entered service, the plant has enabled a clear reduction in groundwater consumption of at least 82.5 million m3. The benefits can be felt throughout the area: reusing wastewater provides the industry with a source of water that is 33% cheaper than groundwater. High-quality irrigation water enables farmers to diversify their agricultural production and reduce the morbidity rate from intestinal and skin diseases. Finally, local educational projects have raised awareness among the city s inhabitants of the economic and environmental benefits of recycled water.

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