How to improve the agricultural reuse of water used before for other things?

The water that escapes through the drain can be treated and reused to irrigate crops, avoiding extracting larger quantities from natural sources. Based on this idea, a team of researchers has developed a method for efficient and sustainable management of wastewater for use in agricultural irrigation.

The team, which includes researchers from the Polytechnic University of Madrid (UPM) and the University of Valladolid (UVa), both institutions in Spain, specifically proposes a method to quantify the costs and benefits of water reuse projects for irrigation , identifying those that would potentially entail greater net benefits. The proposed method facilitates the definition of alternative scenarios and provides scientific evidence to support water policy decisions.

Water is a fundamental ingredient for agricultural crops, especially irrigated crops that require it to be extracted from the natural environment (reservoirs, underground aquifers). Sometimes farmers do not have as much as they would like, and climate change is also implying greater variability in water availability: more intense rainfall, but also longer and more unpredictable periods of drought.

Increasing the extraction of water from the natural environment has its risks: rivers with little flow hinder the development of flora and fauna, and increasingly deep aquifers require deeper wells and water pumps that consume more energy. For this reason, alternative water sources are sought to continue sustaining agricultural activity without compromising the ecosystems with which it coexists. One of those alternative sources is, literally, the water that we throw down the drains at home. Have we stopped to think that water is not consumed in the same sense that we consume a watermelon, that after eating it ceases to exist as such? Most of the water we use in our homes is still water, just mixed with other elements (soap, food waste, etc.). This water is normally thrown into rivers or the sea after purification treatments that prevent it from being polluting. But a part can undergo additional treatments that restore its initial purity so that it can be reused in irrigation of agricultural crops. With this, several lives can be given to the water that we extract from the natural environment. “The idea is good, and the technology to do it is already available. However, the reuse of water for irrigation is currently well below its potential”, comments Antonio Bolinches, researcher of the RECLAMO project.

These additional treatments can be done in plants called “wastewater regeneration stations” (ERAR). These stations require initial investments for their construction and have a daily operating cost, which means that they must be chosen carefully where to install them. The RECLAMO project, directed by Dr. Irene Blanco from the Polytechnic University of Madrid (UPM) in Spain, fits into this context.

Water is a fundamental resource for agricultural crops. (Photo. USGS)

A specific study that has been undertaken in this project has analyzed how to prioritize water reuse projects, taking into account the potential clients (irrigators) existing in the vicinity, the benefits generated and the infrastructure costs. To do this, the team has developed an algorithm that is capable of automatically generating a layout of the water distribution network that minimizes the cost, based on the characteristics of the plots. The method has been applied in Alto Guadiana, in central Spain, where there have been problems of overexploitation of local aquifers and the consequent restrictions on the use of water.

Taking into account the existing wastewater treatment plants, the candidate projects for reuse are classified according to their benefit/cost ratio, presenting great differences according to the location and potential use of the reclaimed water. With this, the costs and benefits of each candidate project can be known in advance.

With this information, the authorities can make decisions about the investments to be made and anticipate the effect of changes in the type of crop, in the water regeneration technology, or in interest rates for repayments, for example. “In this way we will ensure that water is given more lives than a cat, protecting the environment and maintaining our agricultural resources” conclude the researchers.

Irene Blanco and her colleagues present the technical details of their method in the academic journal Agricultural Water Management, under the title “A method for the prioritization of water reuse projects in agriculture irrigation”. (Source: UPM)