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Decontaminating water: an increasingly urgent need and an action possible thanks to research. Interview with Barbara Ruffino and Mariachiara Zanetti from the Politecnico di Torino.

Drinking water has increasingly become an asset to be preserved, protected  and – at the same time – to be guaranteed. For this reason, the decontamination of wastewater is a process that has become a necessity in the  in the municipal as well as industrial context. With reference to wastewater generation, the latter is certainly the most impactful sector but, at the same time, it is also the context in which most studies and projects concerning water decontamination take place.

In Italy, most part  of the work and spin-offs in this framework,  comes from research laboratories. One example is ‘Ozonation of Wastewaters with high ammonia loads’ from Politecnico di Torino. The patent, conceived and developed by Prof. Barbara Ruffino and Prof. Mariachiara Zanetti, aims to treat wastewater of industrial origin through an ozonation process, without generating nitrate and with a low environmental impact.

The technology, uploaded on the Knowledge Share platform, was the winner of the 1st KS Awards as the most visualised patent on the English version of the platform in 2022. We therefore interviewed Professors Ruffino and Zanetti to learn more about the project.

What are your background and role/interests in the world of research?

Barbara Ruffino: I  got a degree in Environmental and  Land Engineering (2002) and a PhD in Environmental Geoengineering (2006). Since 2018, I have been an associate professor in Environmental Engineering. My research interests focus on  primary water and wastewater treatment, mainly with advanced oxidation processes (as in the case of the patent) and biological processes,  sludge and waste valorisation. I had the opportunity to improve my knowledge concerning the process covered by the patent thanks to a research contract with Sodai Italia S.p.A. and a research period spent at the University of Washington in Seattle (2015).

Mariachiara Zanetti: Full Professor of Environmental  Engineering at the Politecnico di Torino DIATI Department. I am the coordinator of numerous research contracts with large companies and small and medium-sized enterprises aimed at finding solutions, for the management of water, emissions and waste, that are fully compatible with the environment and at a sustainable cost. The patent developed with Prof. Ruffino is aimed at encouraging the reuse of water in companies in order to minimise water consumption.

‘Ozonation of Wastewaters with high ammonia loads’: from idea to market potential.

The patented process refines and improves an earlier process developed by Japanese engineers. The principle on which the process is based is the oxidation of ammoniacal nitrogen to nitrogen gas by ozone, assisted by bromide ion. Bromide ion improves the efficiency of ozonation. In fact, the traditional process of oxidation of ammoniacal nitrogen by ozone has two main disadvantages: (i) it  has a rather slow rate (ii) it converts ammoniacal nitrogen to nitric nitrogen, not actually removing nitrogen from water but only changing its oxidation state. The ozonation process assisted by bromide ion converts ammoniacal nitrogen into gaseous nitrogen, which is thus permanently removed from wastewater, similarly to the biological process of nitrification-denitrification.

However, the ozonation process assisted by bromide ion has a side effect, namely the generation of bromate ion, which is classified in group 2B, i.e. a possible human carcinogen.  This effect makes the application of the patented process unsuitable for drinking water, which is why it is mainly aimed at treating industrial wastewater (e.g. effluent from the ammonia absorption process) in order to  subsequently promote its reuse.

How does Ozonation of Wastewaters with high ammonia loads’ work and how does it improve the ‘status quo’ of currently used technologies?

The objective of the research that led to the development of the patent was to determine the boundary conditions of the process that would ensure, at the same time, an effective removal of ammonia nitrogen while keeping the bromate ion concentration as low as possible.  Studies have shown that this objective is achievable in water containing only ammoniacal nitrogen and inorganic species (preferably with a buffering effect, i.e. capable of counteracting the inevitable drop in pH caused by the oxidation of ammoniacal nitrogen). Uncertainties remain, however, related to the role of organic substances, natural or synthetic, in the formation of bromate in the ozonation process assisted by the bromide ion. Preliminary studies conducted as part of the PoC project (funded by the Compagnia di Sanpaolo in 2017 and aimed at a better understanding of the potential and limits of the process) have shown that some organic substances do not have effect on the generation of bromate, while others enhance its generation.

Project progress to date and plans for the future: what are you looking for? Have there been any requests for applications in other types of wastewater besides industrial wastewater?

As already mentioned, the main interest of the patented process relates to the treatment of industrial wastewater, but it can also play an important role in the refinement of the quality of wastewater, pre-treated by conventional processes, in order to be reused in the industrial or agricultural sector. The re-use of water, at a time of reduced availability of primary water and the need to safeguard this water, especially if it is of high quality, for drinking purposes, is certainly a strategic issue and worthy of further investigation.

Learn more about ‘Ozonation of Wastewaters with high ammonia loads’: Ozonation of wastewaters with high ammonia loads | Knowledgeshare (knowledge-share.eu)