Detrimental vs. beneficial influence of ions during solar (SODIS) and photo-Fenton disinfection of E. coli in water: (Bi)carbonate, chloride, nitrate and nitrite effects

https://doi.org/10.1016/j.apcatb.2020.118877Get rights and content
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Highlights

  • A systematic assessment of ions effect on SODIS & photo-Fenton process was performed.

  • Only NO3-,NO2- significantly enhanced SODIS, in presence or absence of organic matter.

  • Photo-Fenton was less negatively affected than SODIS by the ions’ presence in water.

  • HO conversion to other radicals maintains the disinfecting capacity of photo-Fenton.

  • APEX modeling revealed the important contribution of NO2 in bacterial inactivation.

Abstract

In this work, we studied the effect of inorganic ions occurring in natural waters on E. coli inactivation by solar and photo-Fenton processes, two crucial methods for drinking water treatment in sunny or developing countries. HCO3-,Cl-,SO42-,NO3-,NO2- and NH4+ were assessed at relevant concentrations for their inhibiting or facilitating role. The inactivation enhancement during solar disinfection (SODIS) was mainly attributed to the generation of HO radicals produced during by excitation of NO3-,NO2-, while the HO of photo-Fenton may be transformed into other radical species in presence of ions. Natural organic matter (NOM) was found to enhance both processes but also to hinder most of the enhancing ions, except for NO2-; modeling with the APEX software unveiled the inter-relations in the presence of NOM, and the possible inactivation activity by NO2. The photo-Fenton inactivation was more significantly enhanced by ions than SODIS (besides the case of NO3-,NO2-), but both processes were found robust enough.

Abbreviations

APEX
Aqueous Photochemistry of Environmentally occurring Xenobiotics
CFU
Colony Forming Unit
LB
Luria-Bertani
LMCT
Ligand-to-Metal Charge Transfer
MQ
Milli-Q water
NOM
Natural Organic Matter
PCA
Plate Count Agar
RHS
Reactive Halogen Species
ROS
Reactive Oxygen Species
SRNOM
Suwanee River Natural Organic Matter
UV
Ultraviolet

Keywords

Solar disinfection
Photo-Fenton process
Bacteria
Inorganic ions
Inactivation modeling

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