Wastewater management is undergoing a profound transformation. With increasingly resilient purification systems and technologies that enable reuse, the integrated water service is evolving towards a circular model.
Wastewater is the water that results from domestic, agricultural and industrial use. Before it is returned to the environment, it must undergo purification treatments to remove pollutants, including the solid fraction commonly known as sludge.
Within the integrated water service, the sewerage and purification system plays a central role in safeguarding environmental quality and public health. Its resilience — the ability to adapt and operate effectively even under critical conditions — is now essential to meet the challenges posed by climate change and the growing pressure on water resources.
In this context, wastewater management is evolving to consolidate a sustainable model based on reducing consumption, reusing treated water and improving the energy efficiency of processes. It is an approach that turns discharges into opportunities, creating value at every stage of the water cycle.
Reusing purified wastewater
The Hera Group is making investments to strengthen the resilience of the sewerage and purification system, also in response to extreme weather events.
The multi-utility takes concrete action to reduce water consumption, providing customers with self-monitoring tools and acting directly on the management of its own operations. Hera promotes agricultural and industrial reuse through agreements with public bodies and local companies, backed by rigorous testing protocols to ensure quality. As for sludge management, the focus is on reducing landfill disposal and recovering value through innovative reuse solutions.
Around three million cubic metres of drinking water are saved every year by reusing purified water.
Algae and biostimulants: a new frontier for agriculture
In San Cesario sul Panaro, in the province of Modena, Hera has built a pilot plant to cultivate algae and turn them into biomass for the agronomy sector. The project allows to reduce nitrogen and phosphorus concentrations at different stages of purification, as required by regulations, and reuses these elements to support algal growth. The resulting biomass can be processed and turned into a natural biostimulant, a concrete example of circular economy in action. The initiative was developed in collaboration with the University of Bologna through a PhD funded by Hera with NRRP funds, and with the contribution of European experts in biostimulants. The pilot plant is a pioneering technology for urban wastewater treatment plants.
Technology applied at the San Cesario wastewater treatment plant
The pilot plant consists of a 90-square-metre greenhouse built inside the San Cesario wastewater treatment plant, which has an annual capacity of 600,000 cubic metres and enough space to accommodate the new technology.
Inside the greenhouse, located near the wastewater inflow, there is advanced equipment and machinery: a unit for storage and culture preparation, a tank and a vertical photobioreactor for algal cultivation, a centrifugal separator to collect the biomass, and a field laboratory. Here, staff from Biosyntex — a company based in Imola specialising in algal strain selection and pilot plant construction — will isolate from wastewater samples the strains suitable for small-scale algal growth, whose subsequent processing will produce the biostimulant to be used in the agronomy sector.
Prototypes for irrigation and fertilisation
Another example of wastewater reuse in agriculture is the project developed in collaboration with ENEA, the University of Bologna and Irritec: a technologically advanced prototype that allows wastewater to be purified and then used for the irrigation and fertilisation of cultivated fields (https://www.gruppohera.it/-/irrigare-e-fertilizzare-i-campi-con-acque-reflue-depurate-arriva-il-prototipo). The project, which is an example of circular economy, not only enables water reuse but also allows to reduce the use of chemical fertilisers, making the treatment chain even more sustainable.
Beyond giving wastewater a second life, can we also make the sludge life cycle circular by reducing the amount of waste to be disposed of?
Yes, thanks to ultrasonic hydrolysis, a system already installed at the Forlì treatment plant (https://www.gruppohera.it/-/le-acque-reflue-si-fanno-belle-con-un-trattamento-a-ultrasuoni ).
Major steps to protect the environment in smaller urban centres
The Group is carrying out several projects to upgrade and adapt treatment plants, including: the expansion of the Ca’ Nordio (Padua) plant, which will strengthen Padua’s entire sewerage and treatment system even under adverse weather conditions and optimise treatment capacity; the upgrade of the anaerobic digester at the Gramicia plant in Ferrara (Ferrara) to improve sludge management; and the enhancement of the Calcinelli (Pesaro-Urbino) plant.
Many projects have already been completed or are underway in the province of Ferrara to ensure the compliance of discharges in small villages which are not yet connected to treatment plants. Some examples include the upgrade of Cona’s wastewater discharges, with two new pumping stations and a new sewer system about 900 metres long, and the project in Quartiere, where combined flows now reach the Portomaggiore wastewater treatment plant through a new sewer system more than two kilometres long and are then returned to the environment after purification.
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