Photocatalytic reactors and processes for the abatement of harmful N-containing pollutants from waste and drinking waters
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Data di Pubblicazione:
2017
Citazione:
Photocatalytic reactors and processes for the abatement of harmful N-containing pollutants from waste and drinking waters / I.G. Rossetti, M. Compagnoni, G. Ramis. ((Intervento presentato al 27. convegno Giornata mondiale dell’acqua tenutosi a Roma nel 2017.
Abstract:
The N-contamination problem has been effectively synthesized in the following Figure (on the left) and is addressed as one of the main concerns by the European Environment Agency (EEA).
Indeed, environmental limits are defined by ‘planetary boundaries’ (right Figure, [Rockström et al., Nature, 461 (2009) 472]), where the inner blue-delimited zones represents estimated planetary safe boundaries. The nitrogen cycle has already disrupted the safe operating limits, well beyond climate change. Initial estimates suggest the ecosystem impacts of nitrogen pollution cost the EU-27 between €25 billion and €115 billion per year, and total costs (including those from N-related health and climate change impacts) could amount to €320 billion a year.
“A Blueprint to Safeguard Europe's Water Resources” has been published in Nov. 2012, highlighting that diffuse and point-source pollution are still significant pressures on the water environment in about 38% and 22% of EU water bodies, respectively. Eutrophication due to excessive nutrient load remains a major threat to the good status of waters as nutrient enrichment is found in about 30% of water bodies in 17 Member States. In the same frame, environmental pollution with pharmaceutical residua is recognized as an emerging pressing problem. The Commission is going to present a report on the scale of this problem, in order to propose adequate legislation. The same document fosters the use of Best Available Techniques (BAT), or the development of new ones, to ensure the improvement of water quality.
Inorganic nitrogen containing pollutants, such as inorganic ammonia, nitrites and nitrates, are responsible of acute and/or chronic diseases, especially for infants and children. Effective methods for their abatement from waste and drinking waters are still missing.
Biological treatments are standardized processes allowing the abatement of biodegradable organics from waste waters to meet common regulations. However, the legislative limits for N containing compounds can hardly be met by this standardized treatment, imposing further processes for N removal (and additional costs). The revision of the whole capacity for waste water treatments of Lombardy evidenced that sufficient depuration efficiency for organic compounds characterizes large scale depuration plants, efficiency decreasing with plant size. In any case, however, the regional objective for the abatement of 75% of N-containing compounds has not been met in any plant, removal efficiency attesting on 60-66% for small and large scale installation, respectively [http://www.arpalombardia.it].
Ion exchange traditionally has been used to remove nitrates from drinking water sources, but this process leaves behind a highly concentrated brine solution that still requires treatment. Alternatively, reverse osmosis and electrodialysis may be used, which however are expensive processes due to their installation and management costs. In addition, several methods have been developed and applied to the treatment of ammonia-containing wastewater, including biological processes, air stripping, ion exchange, breakpoint chlorination, and chemical oxidation. Among these methods, biological processes are generally regarded to be the most efficient. However, these processes have disadvantages, including handling difficulties and large equipment requirements. Moreover, they are difficult to apply to treatment of wastewater that contains harmful co-existing species for bacteria.
Therefore, the development of cheaper and easily scalable systems for their abatement is more than welcome and is at the basis of our strategy. Together with the review of existing tertiary treatments, we developed innovative photocatalytic processes for the abatement of
Tipologia IRIS:
14 - Intervento a convegno non pubblicato
Elenco autori:
I.G. Rossetti, M. Compagnoni, G. Ramis
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