WATER GLOBAL PRACTICE Wastewater: From Waste to Resource The Case of San Luis Potosí, Mexico Integrated Wastewater Management PHOTO 1. Tenorio Wastewater Treatment Plant Plan and Water Reuse Context Mexico. Water is scarce in the state of San Luis Potosí, ­ 2.7 million inhabitants in the metro- With more than ­ politan area (as of 2015) and intensive industrial and economic development, the region gets less than 400 ­ ear. The state government has been a mm of rainfall a y pioneer in understanding wastewater as a resource to dispose. Since the utilize rather than a waste only to ­ 1990s, the city’s development has been tied to water ­ euse. Given the conservation efforts and wastewater r area’s fast growth, the aquifer was being depleted, recharge. with extractions doubling its natural ­ To protect the aquifer and to promote the use of Source: ComisiÓn Estatal del Agua 2006. wastewater for nonpotable uses such as for agri- culture  and industry, the state government imple- industrial stakeholders have ensured the economic mented an Integrated Plan for Sanitation and Water program. The Plan for Sanitation sustainability of the ­ ­Reuse. Since then, seven wastewater treatment plants and Water Reuse has had economic, environmental, have been built in the region, treating most of the ­ ommunity. and social benefits for the area and the c wastewater from the metropolitan area and reusing This case study focuses on the largest wastewater treated. The innovative 100 percent of the wastewater ­ treatment plant in the area: the Tenorio-Villa de Reyes water reuse contracts and agreements with different (WWTP). wastewater treatment plant ­ 1 CHALLENGE improve the quality in the Tenorio tank, which has Population growth and rapid economic development ‡ been modified to perform as a wetland (see figure ­ 1). overextraction of the aquifer The plant uses different processes for the varying OBJECTIVE reuse  purposes, becoming the first project in Mexico • Better exploitation and management of groundwater sources water. First, the sus- to produce multiquality recycled ­ • Diversify water sources through incorporating alternative pended matters are removed before the water is dis- sources (treated wastewater) charged into the Tenorio t ­ ank. The water for irrigation • Use of treated wastewater for non-potable uses (wastewater reuse) from Tenorio tank meets the standards established by • Improve water efficiency in agriculture the Mexican government regarding total suspended • Rainwater management and control solids (TSS), biochemical oxygen demand (BOD), and coliforms. The water treated for the power plant fecal ­ • Artificial recharge of the aquifer meets the standards agreed with the Federal Electricity • Health improvement of citizens Commission (Comisión Federal de Electricidad, or CFE) to ensure at least the same con- FIGURE 1. Project Tenorio, San Luis Potosí centration cycles in the cooling groundwater. towers as with the ­ Water reused for agriculture (500 ha) Wastewater reuse is not some- WASTEWATER Environmental thing new; it is done in many is used in the cooling enhancement towers instead of Tenorio tank wetland WWTPs in the ­world. The inno- freshwater 600 I/s vative aspects of the Tenorio 450 I/s Project are the multiquality Treated wastewater use of the treated wastewater to meet the different end users’ needs, and the contractual WASTEWATER agreement with the industrial THERMAL POWER PLANT TREATMENT PLANT (CFE) user, which ensure a constant TENORIO WASTEWATER $ revenue stream and enhance from san luis potosí the financial sustainability of the ­project. Source: Treatment plant image is by Tracey Saxby, Integration and Application Network, University of Maryland Center for Environmental Science (ian.umces.edu/imagelibrary/). Note: CFE = Comisión Federal de Electricidad (Federal Electricity Commission). Financial and Contractual Agreements Tenorio Project The infrastructure needed for The Tenorio WWTP is the largest plant in the metro- the Tenorio project required an investment of US$67 politan area of San Luis Potosí, treating 45 percent (2004). Costs included the wastewater treat- million ­ of the total wastewater generated by the ­ c ity. The ment plant, 59 km of sewer pipes, a 39-km water treated wastewater is used for three purposes: (a) for distribution system to the power plant, and an irri- cooling purposes in a nearby thermal power plant gation system for 500 ­ ha. The Mexican federal gov- instead of using groundwater; (b) for agricultural ernment provided 40 percent of the capital costs as a irrigation instead of using wastewater and ground- grant (Fondos FINFRA) with the remaining 60 percent water; and (c) for environmental enhancement to equity). financed through private funding (debt and ­ 2 Wastewater: From Waste to Resource To ensure the sustainability of the project, the State construction years and 18 years of operation (under Water Commission (Comisión Estatal del Agua, or a  build-own-operate-transfer scheme); and a pur- CEA) signed two contracts: one with the private chase agreement of the treated wastewater with company ARTE for the construction and mainte- ­ the CFE for the supply of water for the power plant nance of the wastewater treatment plant for two (see figure ­2). FIGURE 2. Stakeholders of the Project State Water Commission (CEA) Purchase Concession agreement agreement of the treated 18 years wastewater Federal Electricity Commission (CFE) FINFRA (Trust Fund for Aguas del Reuso del Federal Infrastructure) Tenorio (ARTE) Mexican Treated Degremont (41%), Government wastewater Sumitomo (29%), and Prodin (20%) Treated wastewater Banobras and risk capital Farmers Benefits Economic Environmental and social plant. The treated wastewater is 33 percent cheaper, • For the power ­ • Net reduction of groundwater extractions; indirect augmentation more consistent (quality and quantity), and more sustainable than of drinking water resources and rehabilitation of the aquifer previously. The power plant the groundwater the power plant used ­ • Larger biodiversity as a consequence of the improved water quality years. has saved US$18 million in six ­ in the Tenorio tank wetland, especially migratory birds WWTP. The extra revenue stream from treated wastewater • For the ­ • Environmental remediation fees covers almost all operation and maintenance ­ costs. • Health improvements include decrease of gastrointestinal and skin farmers. The treated wastewater is of better quality than • For the ­ diseases rate in the area previously irrigated with raw wastewater previously. That the untreated wastewater that farmers used ­ • Reference case of wastewater reuse, encouraging other industries has led to an increase in agriculture production and has allowed to explore wastewater reuse crops. farmers to diversify or switch to higher value ­ • Improved living standard for the population near the wastewater industry. Reduced risk due to the increased • For the farmers and ­ treatment plant as the ecological environment of the zone was resilience to droughts and competition through the alternative enhanced water ­resource. Wastewater: From Waste to Resource 3 wastewater. Moreover, local water prices for indus- ­ PROFILE try that reflect the cost and scarcity of the area have NAME sources. incentivized the use of alternative ­ Tenorio–Villa de Reyes Wastewater Treatment Plant LOCATION • Stakeholder engagement and ­compromise. For exam- ple, the CEA had to engage and negotiate with the San Luis Potosí, Mexico farmers because they believed that treating the SIZE wastewater would reduce the nutrient content that 91,000 m3/day (capacity) ­ hem. CEA ensured them that served as fertilizer for t MAIN INNOVATIONS the water would be of better quality and explained Integrated wastewater management plan water. them the benefits of using treated ­ Multiquality recycled water Innovative contract agreement and finance • Creative finance and contract TECHNOLOGY • Seeking local ­opportunities. Given that water fees Screening and advanced primary treatment in lamellar for industrial uses in San Luis Potosí are very high, clarifiers enhanced with chemicals ‡ removal of suspended there was an opportunity to engage with those matters and discharge into Tenorio tank wetland final water users and offer them treated wastewa- Natural engineered treatment and polishing in the wetland ter at a better ­ price. with a total surface area of 2 million m2 ‡ agricultural reuse irrigation of fodder crops • Proof of ­concept. As part of the agreement, the Secondary treatment by activated sludge with nitrogen first contract between CFE and CEA was only for removal + tertiary treatment with lime softening, sand one year to prove the reliability of the wastewater filtration, ion exchange for silica, and hardness removal and chlorine disinfection ‡ industrial reuse supply. Once CFE was convinced of the quality of ­ Complex distribution system with several pumping stations the water and the service, contracts were signed and an equalization tank to adjust to the industrial hourly periods. for two-year ­ demand for the power plant • Clear bidding rules, defining responsibilities • Quality and timing of the construction The guaranteed demand for treated wastewater from the power plant allowed the CEA to undertake the • Public outreach, raising awareness of uses of treated wastewater risks. The CEA and CFE agreed that the fee investment ­ for the wastewater would be 67 percent of the price • Multi-quality of wastewater tailored for the different ­ tate. of groundwater for industrial purposes in the s uses (fit to purpose) Waster cost for industrial uses in San Luis Potosí is one of the most expensive in the c ­ ountry. Therefore, the • Consistent quality of the treated wastewater agreement between CEA and CFE benefited both par- • Right mix of ­ expertise. Degremont, Sumitomo, and ties: it reduced operational costs both for the power Prodin formed Aguas del Reuso del Tenorio (ARTE) plant and wastewater treatment plant and it protected to leverage each organization’s respective financial the ­aquifer. capacities and technical ­ expertise. Key Factors for Success Conclusion • Government support and ­leadership. Federal and state In San Luis Potosí, the right mix of local conditions policies promote and regulate the use of treated and political support combined with a creative project 4 Wastewater: From Waste to Resource funding and design that incentivized wastewater reuse, 17. “Mexico 2006: 4th World Water Forum,” WBCSD Conference, March ­ ­h ttp://www.bvsde.ops-oms.org/bvsacg/e/foro4/17marzo/business​ which made wastewater treatment economically and /­sanea.pdf. sustainable. The Tenorio Project is an environmentally ­ V., ­ Lazarova, ­ A. ­ L. Equihua, and ­ 2014. “Sustainable Water Rojas. ­ example of how a well-implemented plan can benefit Management with Multi-Quality Recycled Water Production: both the private and the public sector and have envi- Mexico.” Journal of Water Reuse and The Example of San Luis Potosí in ­ 18-24. DOI: ­ Sanitation 4 (1): ­ 10.2166/wrd.2013.006. ronmental benefits at the same t ­ ime. After six years of operation, groundwater extractions were reduced by Rojas, A (2011) Experiencia de reuso del agua tratada en la Zona Potosí., Jornadas técnicas sobre la recarga arti- Metropolitana de San Luis ­ 48 million cubic meters, which is equivalent to nearly ficial de acuíferos y reuso del Agua, Instituo de Ingeniería UNAM, 9-10 pools. 20,000 Olympic-sized swimming ­ Mexico. ­ June 2011, Mexico DF, ­ http://www.agua.unam.mx/assets​ /­acuiferos/pdfs/presentaciones/albertorojas_ceaslp.pdf. Rojas, A L. Equihua, and ­ ­ ., ­ Gonzalez. ­ F. ­ 2012. 2012 Guidelines for Water References Reuse. ­ ­ EPA. Appendix E: International Case Studies and International ­ ., and ­C. ­Courjaret. ­2006. “Saneamiento Integral y Diaz de Leon Barroso, U Regulations. “Tenorio Project: A Successful Story of Sustainable ­ Potosí.” Presented at Reuso Industrial y en la Agrícultura en San Luis ­ ­Development.” Wastewater: From Waste to Resource 5 ­ ank. Some rights ­ © 2018 International Bank for Reconstruction and Development / The World B reserved. The find- ings, interpretations, and conclusions expressed in this work do not necessarily reflect the views of The World Bank, represent. The World Bank does not guarantee the accuracy its Board of Executive Directors, or the governments they ­ work. This work is subject to a CC BY ­ of the data included in this ­ (https://creativecommons.org/licenses​ 3.0 IGO license ­ by/3.0/igo). The World Bank does not necessarily own each component of the ­ /­ content. It is your responsibility to ­ wner. 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