Benefits and limitations of using Fe(III)-EDDS for the treatment of highly contaminated water at near-neutral pH

This study evaluates the use of the Fe(III)-EDDS complexing agent as an alternative to conventional acidic pH photo-Fenton for the treatment of the pesticide imidacloprid in natural water. The main objective is to estimate whether Fe(III)-EDDS is a viable alternative when treating waters containing high concentrations of contaminants. To this end, the mode of action of Fe(III)-EDDS is examined in the presence of carbonates, at different aeration conditions and at different temperatures. The role of HO2 center dot/O-2(center dot-) radical species and some aspects of the Fe(III)-EDDS complexation mechanism are discussed. Degradation kinetics and toxicities of generated intermediates are compared between Fe(III)-EDDS and conventional photo-Fenton treatment. An overview of the benefits and limitations of the process is presented. (C) 2015 Elsevier B.V. All rights reserved.

Principal parameters affecting virus inactivation by the solar photo-Fenton process at neutral pH and mu M concentrations of H2O2 and Fe2+/(3+)

Anna Carratala Ripolles, César Pulgarin

The inactivation of the coliphage MS2 (a human virus indicator) by solar photo-Fenton at near neutral pH in carbonate buffer solution matrix was evaluated. The effects of reactant concentration (H2O2, Fe2+, Fe3+) and solar irradiance on the photo-Fenton process were studied. Specifically, the solar exposure/Fe3+ treatment showed a strong dependence on the iron concentration and solar irradiance intensity leading to complete inactivation (from 10(6) PFU mL(-1) to the detection limit) with 1 mg L-1 of Fe3+ and 60 min of solar irradiance (45 W m(-2)). The MS2 inactivation observed with the photo-Fenton process (solar exposure/H2O2/Fe2+/3+) carried out with Fe3+, was faster than with Fe2+ (detection limit achieved at 20 min and 50 min, respectively). Moreover, virus inactivation by photo-Fenton under different solar irradiance values (15,30 and 45 W m(-2)), H2O2 and Fe3+ concentrations (0.1, 0.5 and I mg L-1) and different pH values (6, 7 and 8) were evaluated. In order to validate the efficiency of the photo-Fenton process at near neutral pH on virus inactivation, the photocatalytic treatment was carried out in natural water (Lake Geneva, Switzerland) and with a human virus (Echovirus). Finally, a conceptual mechanistic interpretation was proposed regarding how solar photo-Fenton acts on viruses in water, involving the key species Fe2+, Fe3+, H2O2, solar irradiance, organic matter, and their possible reactions and interactions. (C) 2015 Elsevier B.V. All rights reserved.

2015

Enhancing the photo-Fenton treatment of contaminated water by use of ultrasound and iron-complexing agents

Stefanos Papoutsakis

The photo-Fenton process is a promising emerging technology for the treatment of contaminated water streams. It is based on the generation of reactive oxygen species that are capable of destroying recalcitrant contaminants otherwise unaffected by conventional municipal wastewater treatment method. Among its innate advantages are that it can be catalyzed naturally by solar radiation and the main reagents required are iron and hydrogen peroxide, both abundant and relatively cheap. There are however some important limitations. The process functions best at acidic pH, is negatively affected by some inorganic ions present in natural water and the water requires pH neutralization and iron recuperation following the treatment. These limitations inhibit the application of the process at larger-scale. This work is an attempt to develop new strategies for enhancing the photo-Fenton process for making it a more attractive option for the treatment of municipal or industrial wastewaters. Two main pathways are investigated, the use of ultrasound and the use of iron-complexing agents. Ultrasonic processes have been shown to improve degradation kinetics when applied in combination with photo-Fenton, while at the same time are not as negatively affected by some of the inorganic ions present in water. Iron-complexing agents can maintain iron soluble at a wider operational pH and can also improve process efficiency via pathways discussed at length in the text. Chapter 2 is focused on the application of ultrasound in combination with photo-Fenton for two very distinct applications: 1) A pilot-scale ultrasound/photo-Fenton system was set-up and evaluated for the treatment of three different contaminants with distinct physicochemical properties and at different concentrations. Synergy was evaluated in terms of degradation kinetics and H2O2 consumption efficiency. 2) Ultrasound was applied alone and in combination with photo-Fenton for the treatment of the iodinated contrast agent Iohexol. These agents are injected in patients during radiographic procedures and excreted via urine. This provided an opportunity to examine if ultrasound could improve their treatment in such a complex aquatic medium. Treatment options both in urine (at the source) and in the context of municipal wastewater are discussed. Chapter 3 is focused on the use of EDDS as an iron-complexing agent for degrading contaminants at near neutral pH across a concentration range usually found in different wastewaters (from ÎŒg L-1 to mg L-1 ). EDDS was used both for the treatment of microcontaminants (ÎŒg L-1) in municipal wastewater treatment plant effluents as well as for highly contaminated ( several mg L-1) water. The importance of several factors and operational conditions is discussed. Chapter 4 discusses the possibility of exploiting natural iron-complexing agents (mainly phenolic/polyphenolic compounds) that can be found in some types of wastewater (e.g from natural products processing industries). The concept of reusing polyphenol-rich wastewater in small quantities as an alternative to artificial complexing agents is introduced. As a case study, water containing highly concentrated cork bark extracts (Cork Boiling Wastewater) has been added in natural water spiked with one or several contaminants. Its capacity to maintain Fe3+ soluble at near-neutral pH as well as the effect on Fenton/photo-Fenton degradation were observed.

EPFL2016

Solar photo-Fenton and UV/H2O2 processes against the antidepressant Venlafaxine in urban wastewaters and human urine. Intermediates formation and biodegradability assessment

Luiz Felippe De Alencastro, Stefanos Giannakis, Hubert Girault, Dominique Grandjean, Idriss Hendaoui, Milica Jovic, César Pulgarin

In this work, the use of Advanced Oxidation Processes (AOPs) against the degradation of an emerging contaminant has been subjected under systematic investigation. The optimization of treatment of the anti- depressant drug Venlafaxine (VFA) was performed, using UV light, the combined UV/H2O2 process, solar light, Fenton and finally the solar photo-Fenton process in laboratory scale. The degradation kinetics, the time necessary to remove 90% of the contaminant and the optimal reactants concentration were proposed. The treatment in pure water, (synthetic) wastewater and urine was assessed, in an effort to identify the opportunities and pitfalls the application of process would encounter in a field application. Treatment by the UV-based methods was found sufficiently efficient and the application of the solar photo-Fenton process showed feasibility in a potential field application with appropriate context. Real urban wastewater effluents after biological and physicochemical treatment were tested, as well as human urine, as a proposal for on-site collection and treatment was also treated. Biological treatment before applying the tested AOPs improved their efficiency, and the strategy of diluting urine prior to treatment greatly enhanced the efficacy of the process. Finally, the identification of the degradation pathway and the biodegradability tests of AOPs treated VFA solutions exhibit promising results concerning the strategy of treatment for similar pollutants of emerging concern.

Elsevier Science Sa2017

Enhancing the photo-Fenton treatment of contaminated water by use of ultrasound and iron-complexing agents

Stefanos Papoutsakis

EPFL2016