Water: drought, with technological innovation, water savings and lower costs for agriculture

Use treated wastewater to irrigate and fertilise fields, meeting up to 70% of the Emilia-Romagna region's irrigation water needs, also reducing fertiliser costs by around 30%. This is the result of experiments conducted by the VALUE CE IN project[1] coordinated by ENEA,[2] in partnership with the Hera Group and the University of Bologna among others.[3] As part of the project, an innovative prototype system for reusing treated water for irrigating peach trees and tomato plants was developed and successfully tested at the Hera treatment plant in Cesena.

70% coverage of water requirements and up to 32% lower fertiliser costs

The general data from the trial, which is particularly critical at a time of water shortage such as the present, are very promising with the potential to meet up to 70% of the regional water demand. Furthermore, the use of purified wastewater, which unlike mains water already contains some nutrients necessary for plant growth, results in savings of 32% nitrogen and 8% phosphorus, for example in the cultivation of peach trees. The percentages reported are significant considering that these nutrients are found in limited concentrations in the purified effluent in compliance with the discharge limits in the area of the Cesena treatment plant, classified as sensitive. Moreover, these values could be even higher in other cases with less stringent discharge limits than the Cesena area, as confirmed by the 98% savings data measured on potassium, a substance for which there is no discharge limit. There was also a total absence of Escherichia coli contamination of both shoots and fruit. Finally, no significant increase in total coliforms and total bacterial load was found at the soil level.

Over one million euros of investment to achieve major environmental benefits

The experimentation, which lasted about two years and will continue in other projects, was carried out at the Cesena wastewater treatment plant where, in compliance with European Regulation no. 741 of June 2020 on the reuse of wastewater, a fully automated prototype was created for the continuous monitoring and control of the quality of secondary and tertiary effluents for their subsequent reuse in an experimental field with 66 peach trees and 54 industrial tomato plants.

The experimental project for the recovery of water discharged from the treatment plant had a total budget of over 1.1 million euros, of which almost 800,000 euros were financed by the Emilia-Romagna Region and co-financed by the Fund for Development and Cohesion (FSC). The aim was to improve the management of purified water with a view to a circular economy and industrial symbiosis in the name of environmental and energy sustainability.

An intelligent irrigation system that takes into account crop needs

The research project was made possible by the installation of a particularly “smart” control and automation unit. In fact, it is able to manage and optimise the reuse of treated water according to its qualitative characteristics and the water and nutritional needs of individual crops in the field.

Some signals acquired by the control unit concern water quality parameters after secondary treatments and at the plant's outlet, which are generated respectively by an online and real-time monitoring system set up by ENEA's LEA laboratory and Hera's instrumentation. Other signals come from the experimental irrigation field, designed and built by the University of Bologna with the collaboration of Irritec, the project's industrial partner, where soil moisture, temperature and conductivity sensors were placed. The control unit was therefore programmed to ensure the activation of pumps, solenoid valves and devices for watering and fertilising the plants, depending on the water requirements of the crops and the nutrient content already present in the purified water. Innovative micro-irrigation systems, again made available by Irritec, were also tested during this phase, and tests were performed on the intelligent irrigation systems used in order to assess the hydrological and agronomic effects associated with reuse.

The Hera Group for the exploitation and circularity of water resources: water reuse

The new experimental system applied to the Cesena treatment plant is part of the drive to increase the value of the resource, which also involves all the other treatment plants managed by the Group. Thanks to agreements with the various Land Reclamation Authorities, the water coming out of the treatment plants, being of good quality, can in fact be reused to supply the main canals of the nodes in the various urban areas.

For example, in 2018 a three-year Programme Agreement was stipulated by the Emilia-Romagna Region, Arpae, Atersir, Hera and Consorzio Bonifica Renana aimed at recovering the wastewater discharged by the Bologna purification plant to ensure the hydrological rebalancing of the flow rates passing through the Canale Navile and Savena Abbandonato water bodies. Initiatives that, in addition to the objective of protecting water bodies in the region, also pursue the principle of reusing water as an asset to be preserved.

After all, saving and reusing water is the cornerstone of the Group's business, which has planned concrete actions that are first and foremost internal. The goal is to reduce the consumption of drinking water in the company's operations by 10%. Moreover, in 2020 Hera initiated further interventions on waste-to-energy plants and purifiers for the recovery and reuse of process water in order to further reduce the use of drinking water in its industrial operations.

“This experimentation, aimed at improving the recovery of purified water”, explains Susanna Zucchelli, Hera's Water Director, “fits perfectly into the perspective of a circular economy system through the reuse of water. The purification of wastewater, which in itself represents an action of recovery and environmental protection, is further maximised through its reuse exploiting precisely the characteristics of this water, channelling it directly to the experimental field set up at the Via Calcinaro plant, with the prospect of generating a positive environmental, social and economic impact for the Cesena area in the future”.

"The results achieved underscore the applicability of the technology chain developed in prototype form as part of the VALUE CE-IN project to all sewage treatment plants in order to guarantee a non-conventional water source that is safe, cost-effective and able to supply nutrients to crops, in line with the new EU guidelines in force from 2023. All this with the aim of promoting the implementation of best practices for the benefit of stakeholders in the supply chain, from plant operators to land reclamation authorities and the automation, control and measurement sector”, stresses project coordinator Luigi Petta, head of the ENEA Laboratory of Technologies for the Efficient Use and Management of Water and Wastewater.

“Thanks to the contribution of a multidisciplinary team of researchers, the experiment has enabled the design, implementation and testing of a precision irrigation and fertigation system capable of exploiting the full potential of reusing purified wastewater for irrigation, while assessing the effects and safety of using non-conventional water on crops for human consumption. This research is particularly relevant in the context of the various actions that UNIBO has been carrying out for several years on the subject of reusing purified urban wastewater in agriculture”, adds Attilio Toscano, professor of agricultural hydraulics at UNIBO.

For more information:

Luigi Petta, ENEA - Head of the Laboratory of Technologies for the Efficient Use and Management of Water and Wastewater,