Olive trees irrigated with treated wastewater, a pilot project to combat drought

Farmland, especially in southern Europe, is thirsty. Every drop of water counts in the Adriatic basin. In Puglia, in southern Italy, water shortage has been accentuated by climate change and, in addition, a bacterium, Xylella fastidiosa, has decimated the olive groves.

The European project ECO FLOW brings together Greek and Italian experts. It proposes reusing Gallipoli's treated wastewater for irrigation, which would otherwise go to the sea. They are focusing on the so-called emerging contaminants. These chemical, material or biological substances, created by humans, come from industrial activities and are present in urban and hospital wastewater.

The experiment is carried out in a field adjacent to the Gallipoli water treatment station. There are three rows of bacteria-resistant olive trees and three forms of irrigation: the traditional one, with the water from the well, the water treated in the purification station and the water subjected to a particular treatment, with which it is intended to reduce the amount of polluting substances. Rocco Protopapa, of the Regional Agency for Irrigation and Forestry Activities (ARIF), a public body in the Puglia region, explains that ECO FLOW's objectives also include "comparing the plants irrigated with the water from the well with those that have received the treated water and those that have received the water treated with hydrogen peroxide.

We want to see how much fruit they produce and how they produce it. And that way we avoid wasting water that would otherwise end up in the sea," he said.At the Gallipoli purification station, the treated water destined for ECO FLOW is purified even more than that of the station's tanks, using the patented technology of a mini station, conceived in another European project, RE-WATER. How does this process of additional water disinfection work?Fabrizio Dell'Anna, in charge of the technical coordination and development of the project from the Aquedotto Pugliese – the organisation in charge of the management of the comprehensive water cycle in Puglia and Campania - comments that the technique "is based on the use of hydrogen peroxide combined with ultraviolet radiation generated by a lamp.

This combination enables the formation of an extremely reactive molecule, capable of degrading pollutants. The challenge was important because the equipment used did not exist on the market." The reactor where the water subjected to this treatment is located is "thermally insulated to avoid temperature variations that could disturb the operation of the hydrogen peroxide". They realised that the number of reactive molecules available to attack the contaminants increased if the water circulated and they completed the system to do so.

ECO FLOW has a budget of more than one and a half million euros, of which 75% have been financed by European cohesion policy and the remaining 25% by funds from Greece and Italy, the two countries participating in the project. In Greece, researchers worked on a physical membrane to better treat and filter wastewater, while in Italy, they concentrated on the chemical solution. Both solutions are complementary, insisted the experts who share this know-how in the framework of the ECOFLOW pilot.

The laboratory of the Polytechnic University of Bari provides technical and scientific support to Acquedotto Pugliese, the project's main partner in the experiments carried out at ECO FLOW. Danilo Spasiano, professor and researcher at the Polytechnic University of Bari explains that the monitoring of ECO FLOW has recently started. They study water and plant development, but also soil characteristics and the accumulation of contingent substances in the soil where the two varieties of olives irrigated in this experiment grow: Favolosa and Lecciana, both resistant to Xylella.This pilot project will run for two years.

The Francesca Stajano farm produces more than sixty tons of olives per year. Its owner, Antonio Astuto, irrigates part of the production with water from his well and another younger olive grove with treated water at the Gallipoli purification station and sees the difference."We didn't expect four-year-old trees to start producing now. Therefore, we were very happy to see that the plants grew faster, probably thanks to the type of water used," he said.In his facilities, the olive trees are irrigated with a drip system to "achieve a good result, avoiding the use of as little water as possible" so that it is not wasted, he concludes.