Electrochemical treatment of pollutants from industrial wastewater for sustainable reuse

Environmental contaminants found in the various ecosystemic matrices may cause health, economic and social risks. One of these concerns at different territorial scales is the nitrogen content in industrial waste water. In particular, agricultural livestock farms apply these effluents to the soil with the mending/fertilising function. The excess of nitrogen compounds that leach, both due to the agrozootechnical system and the urban system, in surface and underground bodies cause risks to the entire ecosystem. For example, nitrogen pollution causes eutrophication of surface water bodies. The presence of nitrogen compounds in drinking water, particularly in the form of nitrates, could also pose a risk to human health as it causes metahemoglobinemia in blood - recognized as "blue baby syndrome", diabetes, miscarriage, gastric and thyroid cancer and Alzheimer’s disease. Nitrates Directive 91/676/EEC identifies Nitrate Vulnerable Zones (NVZs), and limits the spreading of industrial waste water to soils as fertilisers/soil improvers at certain times of year to avoid leaching of these compounds into groundwater. In order to reduce the nitrogen load, so that a greater amount of waste can be spilled or the number of heads increased, it is necessary to find a removal technology which guarantees, at the same time, flexibility of application, simplicity of management, Economic sustainability and transformation of contaminants into compounds harmless to health and the environment. In addition to the removal of "traditional" contaminants, there is a great need to identify technologies also for the removal of emerging contaminants, chemicals that are not yet regulated or monitored, but which are present in the environment at concentrations, even very low, and raise concerns about its potential adverse effects on human health and the environment, which are refractory to conventional treatment technologies. Emerging contaminants are present in different matrices, such as biological, food and environmental, determining potential effects along the entire trophic chain, already at low concentrations. Recent literature has emphasized how the convergence of climate change, water scarcity and pharmaceutical contamination exacerbates the risks to ecosystems and human health, highlighting the urgent need for advanced and circular water treatment strategies (Mallek & Barceló, 2025). Among these, particular attention is paid to micro- and nanoplastics, recognized as emerging pollutants, detected in numerous biological matrices. Other emerging pollutants requiring particular attention are personal care products and pharmaceuticals (PPCPs). Among the various emerging technologies, of particular interest is electro-oxidation, belonging to the family of innovative oxidation processes (Advanced Oxidation Processes) as it is able to convert nitrogen compounds into molecular nitrogen (gaseous nitrogen) and oxidise microplastics until they are converted into CO2. Another technique of interest is adsorption, which has the advantage of capturing on its surface the pollutants to be removed. The research activity was divided into two parts: the first aimed at removing contaminants of interest to the environment and human health with particular reference to nitrogen compounds (Part A). The second part aimed at removing emerging contaminants with particular reference to microplastics and PPCPs (diclofenac): of which the topic PPCPs, carried out mainly in collaboration with the University of Almeria (Spain). The removal of the nitrogen fraction has been studied through electro-oxidation (optimization of different process configurations - batch (CHAPTER 1A), batch with different electrode configuration (CHAPTER 2A) and use of a continuous flow reactor (CHAPTER 4A). The latter was characterized both from an experimental point of view and through the use of computational fluid dynamics (CHAPTER 3A). Micro-plastics are emerging contaminants found in various environmental and biological matrices including atherosclerotic plaques (CHAPTER 1B) in which specific polymers such as polyvinyl chloride (PVC) and polyethylene (PE) have been identified, and in coronary blood (CHAPTER 2B) where the polymers Polyethylene (PE), Polypropylene (PP), Polystyrene (PS), Polyvinylchloride (PVC), Polyethylene terephthalate (PET) were identified. Optimization of the analytical method, including both sample preparation and instrumental analysis, constituted a crucial step in establishing the relationship between microplastic exposure and the associated human health risks. Following the characterisation phase of these emerging pollutants, the research activity concerned the removal of polystyrene (PS) in aqueous matrix by electro-oxidation (CHAPTER 3B). In addition, other emerging pollutants, PPCPs, Among these are anti-inflammatory pharmaceuticals found in reclaimed water intended for sustainable use in the greenhouses of the city of Almería (CHAPTER 4B) — a city characterized by a strong agricultural vocation and, at the same time, by a qualitative and quantitative scarcity of water resources. One of the anti-inflammatory drugs commonly used in Italy contains diclofenac as its active ingredient. Consequently, we evaluated the removal of diclofenac from simulated wastewater through electro-oxidative treatment and, in collaboration with another research group specialized in the pharmacological sector, we investigated oxidative stress and cell mortality. Concurrently, the removal of diclofenac, an anti-inflammatory pharmaceutical compound, was examined through electro-oxidation (CHAPTER 5B). Subsequently, the removal efficiency of diclofenac from a simulated water matrix was assessed using an adsorption process. For this purpose, a hydrochar derived from grape stalks—an industrial waste matrix—was employed (CHAPTER 6B). In definitive, this research highlighted the characterization of various environmental pollutants and their removal from the water compartment, using an advanced technique respecting the ethical principles of the circular economy and the 2030 Agenda.