Water Reuse in Aguascalientes, Mexico.

Co-investment

Compensation

Water Recycling and Reuse

Overview

The project aims to address the chronic overexploitation of the Aguascalientes Valley aquifer in a structural and sustainable manner by constructing and operating a tertiary wastewater treatment plant with an operational capacity of up to 2,000 liters per second. This infrastructure will convert urban and municipal wastewater into a continuous and reliable source of treated water, significantly reducing the pressure on the groundwater aquifer that supplies over one million people.

Through this intervention, the direct discharge of untreated wastewater into the environment will be eliminated and replaced by a productive and environmentally strategic use. The treated water will be allocated for multiple non-potable purposes: precision irrigation in high-value agricultural plots, industrial supply for non-critical processes, and artificial aquifer recharge through infiltration trenches, percolation wells, and constructed wetlands. These applications will directly contribute to restoring the regional water balance by decreasing net groundwater extraction.

In addition to its impact on water availability, the project will have positive effects on water security, increasing the system’s resilience to prolonged droughts and climate change. It will also promote a circular economy approach, enhancing water efficiency and resource recovery within urban and industrial systems. This solution, while replicable, is envisioned as a cornerstone for transitioning towards more sustainable water management in closed and overexploited basins in the country.

Problem and Causes

The Aguascalientes Valley is experiencing a critical state of water stress, exacerbated by structural and technological factors:

Aquifer Overexploitation: The local aquifer has an extraction deficit of over 100 million cubic meters annually, driven by the region’s dense population and concentration of agricultural and industrial activity.

Unregulated Extraction and Limited Recharge: Groundwater withdrawal far exceeds the aquifer’s natural recharge capacity, further aggravated by widespread soil sealing and the lack of functional green areas.

Land Subsidence and Water Quality Deterioration: The declining water table has caused land subsidence, damaging urban infrastructure and releasing heavy metals like arsenic into the water supply, posing a public health risk.

Lack of Sustainable Alternatives: There are no permanent surface water sources to supplement the supply, and the absence of large-scale water reuse deepens the water deficit.

Insufficient Treatment and Reuse Infrastructure: Most treated wastewater is not reused productively, and there is a lack of infrastructure for artificial recharge.

Health Effects

Mitigation Measures and Solutions

The project proposes a comprehensive solution that addresses both water quantity and quality simultaneously through advanced infrastructure, territorial planning, and sustainable management of the urban water cycle.

Tertiary Treatment Infrastructure: The treatment plant will be designed with a process train capable of removing physical, chemical, and biological contaminants. It will include extended aeration activated sludge, secondary clarification, granular media filtration, and ultraviolet or ozonation disinfection. The use of MBR (Membrane Bioreactor) modules is also under consideration to produce high-quality effluent suitable for demanding reuse applications. These technologies will enable the plant to exceed the standards set by NOM-001-SEMARNAT-2021 and NOM-127-SSA1-2021, ensuring safe reuse.

Productive Use of Treated Water: The treated water will be allocated based on its quality to specific non-potable uses. Priority applications include precision irrigation for high-value crops, non-critical industrial processes, street cleaning, and aquifer recharge through green infrastructure such as infiltration trenches, percolation wells, and artificial wetlands strategically located in permeable zones. This will ensure the safe return of water to the subsurface and support water table recovery.

Reduction of Groundwater Extraction: The project will generate a reliable alternative water source, allowing for a reduction in aquifer withdrawals. By shifting agricultural and industrial water use to reclaimed water, the project aims to stabilize piezometric levels and help restore the hydrological balance. This source substitution aligns with Science-Based Targets for Water by contributing to reduced water stress.

Water Quality Improvement: Advanced wastewater treatment will reduce pollutant loads currently impacting receiving bodies and groundwater. This improvement in effluent quality will positively influence groundwater quality, particularly in areas where natural recharge is affected by contaminated infiltration.

Monitoring and Traceability: The system will be equipped with flow and quality sensors connected in real time to a digital monitoring platform. Data will be periodically reported through platforms such as Aqua Positive and aligned with international frameworks like ESRS E3 (corporate water management) and CDP Water. This traceability will certify the additionality and permanence of water benefits, support third-party validation, and facilitate results-based financing.

Sustainable Development Goals (SDGs)

SDG 3 – Good Health and Well-Being: Reduces exposure to contaminated water and hazardous substances such as arsenic.

SDG 6 – Clean Water and Sanitation: Expands the availability of treated water and promotes efficient reuse.

SDG 8 – Decent Work and Economic Growth: Generates employment in construction, operation, and reuse-driven sectors.

SDG 12 – Responsible Consumption and Production: Optimizes water use and supports the circular economy.

SDG 13 – Climate Action: Enhances water resilience against drought and reduces the climate impact of overextraction.

SDG 15 – Life on Land: Improves the hydrological balance supporting natural ecosystems and prevents land degradation.

SDG 17 – Partnerships for the Goals: Requires collaboration among government, private sector, academia, and civil society.

Project Information

Country:

Mexico

Implementation

The plant will be designed using modular and adaptable technologies to facilitate scalability and accommodate variable pollutant loads. An automated control system supported by online sensors will measure key parameters such as flow, quality, and operational efficiency.

The proposed technological layout includes: mechanical screening, grease removal, sand removal, an anoxic reactor for nitrogen removal, transformation of the activated sludge system into a Membrane Bioreactor (MBR), advanced filtration with activated carbon, reverse osmosis for specific applications, and final disinfection via ultraviolet radiation. This process train ensures a high-quality effluent suitable for agricultural reuse, industrial processes, and aquifer recharge.

Treated water will be redistributed through dedicated secondary networks connected to agricultural and industrial users, as well as infiltration zones. Green infrastructure such as trenches and percolation wells will be implemented in permeable soils.

Monitoring will be continuous and digital. All operational and quality data will be collected in real time via platforms like Aqua Positive, ensuring full traceability, enabling external validation, and supporting reporting aligned with frameworks such as ESRS E3, CDP Water, and Science-Based Targets for Water.

Implementation will follow a phased approach: detailed diagnostics and executive design, construction and equipment installation, commissioning and operational adjustments, and continuous operation with predictive maintenance. This staged development will optimize resources, minimize operational risks, and ensure long-term functional sustainability.

Understanding the Project

The objective of this project is to transform water resource management in the Aguascalientes Valley—one of the regions most severely affected by water stress in Mexico—through the implementation of a tertiary wastewater treatment plant with a capacity of 2,000 liters per second. The plant is designed as a structural intervention to harness urban residual flows in an efficient, safe, and environmentally responsible manner, reducing pressure on the aquifer and improving water quality.

The proposed technical solution integrates an intensive reuse approach for treated water in productive (technified agricultural irrigation, non-potable industrial uses) and environmental (artificial aquifer recharge) applications, thereby strengthening both water availability and sustainability. This approach is framed within the VWBA 2.0 methodology, applying method A-4 (indirect recharge), and incorporates WQBA indicators to track water quality improvements.

The Aguascalientes aquifer has been declared in a state of critical overexploitation by CONAGUA, with an annual deficit exceeding 100 million cubic meters. The drop in the water table has resulted in land subsidence, damaged urban infrastructure, declining well yields, and contamination by substances such as arsenic. In this context, developing a new safe water source through reuse is both strategic and urgent.

The treatment plant design incorporates an advanced process train aimed at producing high-quality effluent that meets NOM-001-SEMARNAT-2021 and NOM-127-SSA1-2021 standards and is safe for proposed uses. The technologies include:

Pretreatment: screening, grease removal, sand removal.
Biological Treatment: inclusion of an anoxic reactor for nitrogen removal.
MBR Conversion: upgrading from conventional activated sludge to a Membrane Bioreactor.
Advanced Filtration: with activated carbon for organic contaminant removal.
Reverse Osmosis: in parallel stream for high-value applications.
Final Disinfection: with ultraviolet radiation for microbiological control.

This configuration yields a stable, traceable, and safely reusable effluent suitable for a wide range of applications with low health risks and strong institutional acceptance.

Treated water reuse will be channeled into three main applications:

Technified Agriculture: especially for high-value crops, using dedicated secondary networks separate from the potable system.
Industrial Sector: as input for non-critical processes (e.g., cooling towers, cleaning, blending).
Aquifer Recharge: through green infrastructure such as infiltration trenches, percolation wells, and artificial wetlands located in permeable zones.

This strategic distribution ensures that reused volumes have a real impact on reducing groundwater extraction.

System operation will be based on an automated and digital control scheme. Sensors will monitor flow, pressure, turbidity, conductivity, nutrients, bacteria, and metals, with real-time transmission to a central platform such as Aqua Positive. This traceability enables:

Verification of additionality and permanence of water benefits (VWBA 2.0).
Reporting under international standards: CDP Water, ESRS E3, and Science-Based Targets for Water.
Facilitation of third-party audits and access to performance-based climate finance.

Expected Impact

Proportional reduction of groundwater extraction.
Decrease in organic pollutants, nutrients, and metals in discharge zones.
Mitigation of health risks associated with arsenic exposure.
Improvement in groundwater quality through indirect recharge.
Strengthening of water security in the face of prolonged droughts.