Use of treated wastewater for irrigation of fruit trees

By: Graciela D. Avila-Quezada, Juan M. Rodriguez-Gaeta, Juan C. Burillo-Montufar

Mexico, like many countries, faces a water crisis. In the last seven decades, per capita water availability has decreased alarmingly, falling from 17,742 m³ to 3,656 m³ per inhabitant, and in the state of Chihuahua (northern Mexico) it has dropped to 1,500 m³ per capita.

This situation is exacerbated by the fact that agriculture uses more than 70% of the total volume of water allocated, as established by the National Development Plan 2025–2030. This volume is exceeded in Chihuahua state, more than 90% of the water is used for agriculture.

This document recognizes the urgency of promoting technologies that improve water use efficiency, as well as wastewater treatment and reuse. However, specialists and representatives of the agricultural sector warn that the proposed measures are still insufficient given the magnitude of the problem, thus, researchers and science-based decision-makers must propose specific actions to address this issue.

Given the scarcity of water in agricultural areas of Chihuahua and Texas, this project proposes the use of treated wastewater for irrigation of fruit trees, such as pecan trees, considering that since there is no direct contact between the fruit and the water, the sanitary risk is minimized.

In some pecan trees-growing regions, water scarcity has caused the abandonment of orchards, thus the use of treated water would make it possible to conserve the subway resource for human use.

Our study included the analysis of microbiological contaminants and heavy metals, such as arsenic, in both treated wastewater and evaporated water using solar prototypes designed at UACH.

The results showed that the evaporation process significantly reduced the bacterial load (total coliforms, fecal coliforms, and E. coli < 1.8 MPN/100 mL) and arsenic (more than 50% reduction), complying with FAO guidelines and Mexican standards for agricultural irrigation. This suggests that evaporated water can be used even on edible crops with direct contact.

In addition, water from the Chihuahua South Treatment Plant was evaluated, which, according to the results obtained in the summer of 2025, complies with the limits established for bacteria such as E.coli, fecal coliforms and arsenic by the Regulations NOM-001-SEMARNAT-2021 (Mexico) and the FAO and WHO recommendations for agricultural irrigation.

As part of this study, we propose the use of filters as a complementary decontamination strategy, which is more efficient due to its speed compared to evaporation treatment.

Our experience was presented at academic events such as the World Water Week at The University of Texas at El Paso (UTEP), El Paso, Texas and the International Congress of Agricultural Management in Chihuahua, Mexico.

In Israel and other countries with severe water shortages, all agricultural irrigation is carried out with treated wastewater, even though its cost could be three times that of native water. This measure, adopted out of necessity, demonstrates the urgency of implementing water purification technologies despite the initial costs.

Researchers: Graciela D. Avila-Quezada, Juan M. Rodriguez-Gaeta, Juan C. Burillo-Montufar

Institution: Autonomous University of Chihuahua (UACH) Mexico

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