“La tutela dell’Ambiente e dei Beni Culturali
in un Mondo che cambia”
XVII CONGRESSO NAZIONALE DI
CHIMICA DELL’AMBIENTE E DEI BENI CULTURALI
Genova, 24-27 giugno 2018
CONTRIBUTI SCIENTIFICI
SCADENZA 30 APRILE 2016
Il contributo, presentato in lingua inglese, dovrà essere al massimo di 2 pagine, figure e bibliografia comprese, formattato secondo il facsimile riportato nella pagina successiva.
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Coupling of nanofiltration and thermal Fenton reaction for the abatement of carbamazepine
in wastewater
Marco Minella
1marco.minella@unito.it, Nicola De Bellis
1, Claudio Minero
1, Andrea Gallo
2,
Alberto Tiraferri
2, Davide Vione
11 Dipartimento di Chimica, Università degli Studi di Torino, Via P. Giuria 5, Torino.
2 Dipartimento di Ingegneria dell’ambiente, del territorio e delle infrastrutture, Politecnico di Torino, C.so Duca degli
Abruzzi 24, Torino.
1. Introduction
The main scientific and technological efforts in the field of wastewater treatment have been focused in the past on the implementation of plants able to reach a total abatement of the main macro-pollutants [1]. In this context, the widely implemented technologies based on activated sludge are able to satisfy the most recent legislations for the preservation of water resources. However, the attention of the scientific community in the field of water treatment has recently shifted to the ubiquitous occurrence of micro- and biorecalcitrant contaminants in water environments. These compounds are not or are only partially removed by the conventional wastewater treatment plants (WWTPs), which has arisen concern in several governmental authorities around the world [2,3].
Furthermore, the only partial abatement of micro-pollutants by the traditional WWTPs hinders a safe re-use of the water after treatment (e.g., for agriculture). This issue limits the resilience of human societies that live in environments where water resources are either scarce, or will become so as a consequence of climate change. In the absence of a total removal of micropollutants, the need to close the water cycle to save water would in fact magnify the concentration of these compounds and cause problems to both human health and natural ecosystems.
Among the possible strategies to technologically update the existing WWTPs, it is well documented the ability of the advanced oxidation processes (AOPs), and particularly of the Fenton reaction, to remove many recalcitrant pollutants [4,5,6].
In this work we investigated the coupling of a negatively charged loose nanofiltration (NF) membrane (HydraCoRe70, made up of sulphonated polyethersulphone) with the thermal Fenton process to enhance xenobiotics removal. Carbamazepine (CBZ), a drug prescribed mainly for epilepsy treatment, is here used as model xenobiotic.
2. Results and Discussion
After optimizing the conditions for separation and degradation, the NF-Fenton approach was applied to both synthetic wastewater containing organic macromolecules (humic acid, sodium alginate and bovine serum albumin) able to scavenge the reactive species formed during the Fenton process and real samples from an urban WWTP, to assess the overall efficiency of CBZ removal.
The Fenton degradation of CBZ was drastically enhanced in nanofiltered samples (see Fig. 1), thanks to the removal by the membrane of nearly all organic matter that would otherwise consume the reactive oxidizing species (e.g., the hydroxyl radical or iron super-oxidized species such as the ferryl ion).
Based on a preliminary treatment costs analysis, it can be concluded that the combined process is potentially applicable to the treatment of several kinds of wastewaters (e.g., industrial ones) to favor the removal of biorecalcitrant contaminants. Key cost savings of NF-Fenton concern the lower amounts of Fenton reagents needed to degrade CBZ and (even more importantly) the decreased levels of acids and bases for pH adjustment before and after the oxidative process, due to the lower buffer capacity of the NF permeate compared to feed wastewater, following the removal by NF of many inorganic ions and of most organic carbon.
Fig. 1 – Time trend of CBZ in 5-additions experiments, shown in duplicates (C0
= 0.5 ppm, pH 3 by
H
2SO
4, H
2O
20.5 mM + Fe(II) 0.05 mM for each addition step), in real waste water sample, used
as-is or previously subjected to NF.
3. Conclusions
The NF-Fenton coupling is here proposed as a useful approach to reach an efficient Fenton removal of biorecalcitrant contaminants in wastewater samples that are rich of interfering species. The loose NF membrane showed an excellent ability to remove scavengers, consisting of both high molecular weight compounds in synthetic solutions, and of the TOC (as well as ions, total nitrogen and total organic nitrogen) in actual wastewater. The NF-Fenton approach could considerably enhance the degradation of micropollutants compared to Fenton alone, when applied to a complex water matrix, thereby allowing a significant saving in the use of reagents. Indeed, the NF-Fenton system is significantly effective in the presence of high concentration values of interfering species. In contrast, the coupling of Fenton with NF seems much less justified when operating on matrices containing fewer interfering agents. Moreover, the NF step carries out a notable improvement of the overall water quality, by considerably decreasing the levels of TOC, TON and of the main inorganic nutrients such as nitrate, ammonia and phosphate. However, an in-depth evaluation of the change of the permeation ability at long working times, for instance to properly assess the role of fouling on the overall features of the NF membrane.
Quite interestingly, the cost savings allowed by NF-Fenton are due to both the lower levels of Fenton reactants needed to degrade CBZ in the presence of fewer scavengers, and to the lower amounts of acids and bases required for pH adjustment before and after the Fenton treatment.
The technology here proposed might be considered even for the treatment of industrial wastewater (e.g., textile and/or pharmaceutical industries) where the effluents are often characterized by the concomitant presence of high concentrations of biodegradable agents, easily removed by common activated sludge processes, and biorecalcitrant micropollutants. This technology gives water of very high quality that is potentially re-usable in human activities: its application may be favored either by legislative actions that are going to force toward the total abatement of contaminants of emerging concern from civil/industrial wastewaters, or by the need to re-use wastewater in the framework of water-scarcity conditions.
References
[1] Hammer M. J. Sr., Hammer M. J. Jr. (2012) Water and Wastewater Technology, 7th Edition, Pearson.
[2] Petrie B., Barden R., Kasprzyk-Hordern B. (2015) A review on emerging contaminants in wastewaters and the environment: Current knowledge, understudied areas and recommendations for future monitoring, Water Res. 72, 3–27. [3] Richardson S. D. (2012) Environmental Mass Spectrometry: Emerging Contaminants and Current Issues, Anal. Chem. 84, 747–778.
[4] Barbeni M., Minero C., Pelizzetti E., Borgarello E., Serpone, N. (1987) Chemical degradation of chlorophenols with Fenton's reagent (Fe2+ + H
2O2), Chemosphere 16, 2225–2237.
[5] Lipczynska-Kochany, E. (1991) Degradation of aqueous nitrophenols and nitrobenzene by means of the Fenton reaction, Chemosphere 22, 529–536.
[6] Vione D., Merlo F., Maurino V., Minero C. (2004) Effect of humic acids on the Fenton degradation of phenol, Environ. Chem. Lett. 2, 129–133.
