Water treatment

We are involved in major groundwater remediation projects throughout the country. The measures are implemented through an Integrated aquifer interception and treatment system, consisting of:

• over 1200 groundwater extraction wells
• about 5,000 wells for monitoring and conveying water to treatment plants (GTP) fo purification
• 42 water treatment plants, of which 26 owned.

We also manage urban and industrial biological treatment systems at the sites in Gela, Cengio and Manfredonia. All the assets are compliant with Best Available Technology (BAT) and Best Available Technology Not Entailing Excessive Cost (BATNEEC).

The water treatment processes include strict monitoring systems to ensure that the quality of water discharges and atmospheric emissions are fully respected. To facilitate the recovery and use of water resources and with a view to the circular economy, we support research into innovative solutions for sustainable and efficient water management, with the aim of maximising reuse and reducing withdrawals of water from nature. To do this, we have installed and activated special sections for the production of demineralised water at the GTP plants in Priolo, Porto Torres, Assemini and Brindisi, for reuse by the industrial plants. In other cases, such as in Manfredonia, the treated and osmotised water is partially re-injected into the groundwater to restore the natural conditions of the aquifers. During 2021, we treated about 36 million cubic metres of water, recovering about 9 million cubic metres mainly for industrial use.

Our plants use ad hoc technologies depending on the contaminants and salinity present and any salinity. They include chemical-physical sections (metals), stripping (organic chlorides), filtration with activated carbon (organic), biological treatment (ammonia compounds), osmosis (salinity) and purification to return water to the water table so that it can be recovered or reused at Eni sites. 

In line with our mission, we are driving the optimisation of water treatment processes to reduce water consumption by finding new technical solutions and continuously upgrading our facilities. Greater production efficiency means greater respect for the environment and the health and safety of our workers. In Crotone, for example, we have completed the automation and digitalisation of the pump & treat systems with a tool that controls the flow rate of wells. This ensures that only the necessary amount of water is extracted from the groundwater to carry out remediation operations. In Priolo, there is also a new Dynamic Control System, borrowing from experience in the refining sector, which allows the simultaneous, real-time monitoring of pressure, flow and acidity. Its installation has reduced energy consumption (-10%) and reagent consumption (-15%) and has led to an increase in the production of osmotised water. Also in Priolo, in 2019, the project for the construction of the permeable reactive barrier was approved. This is a remediation system that intercepts the groundwater through the construction of a trench (barrier), which contains specific reactive materials that act on the contaminants, removing approximately 90% of them in the first stage of the barrier.

Our experience in water management has enabled us to develop, together with Eni research laboratories, a technology called Blue Water, was ideated to treat and recover production water from crude oil extraction activities, with a view to ensuring the lowest possible environmental impact. Its implementation will make it possible to regenerate production water, as is the case in traditional purification plants, returning it to surface water bodies or, after further treatment, making it available for industrial use. This reduces the disposal of outgoing residues (salt solutions and sludge), which will be disposed of at suitable external plants and minimises the withdrawal of water from natural sources. At the Val d'Agri Oil Centre in Viggiano, Basilicata, we have designed the first industrial-scale plant that will treat part of the production water that is currently sent for disposal, so it can be used to meet the water needs of the industrial site. The process of authorisation with the local authorities is currently in progress.

In 2016, we started the automation and digitalisation of water treatment plants (GTP) and barriers for the optimal management of groundwater remediation systems. A 24-hour control room in San Donato Milanese remotely monitors 25 out of 42 installations and ensures that the following objectives are met:

• reliability and performance analysis
• increased level of security
• control standardisation
• savings in utility and reagent consumption.