UV/sulphite as alternative for UV/H2O2 for micropollutant degradation in drinking water

C H M Hofman-Caris,B A Wols,D H Harmsen

doi:10.2166/ws.2021.164

C H M Hofman-Caris, B A Wols + Show 1 more

Open Access

https://doi.org/10.2166/ws.2021.164

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Abstract

Abstract The UV/SO32– process can be applied to convert organic micropollutants (OMP). The reaction is induced by UV photolysis of sulphite (preferably using a medium pressure (MP) UV lamp). Although in general it is assumed that the UV/SO32− process is an advanced reduction process, our results show degradation of OMP under both anoxic and oxic conditions. Several recalcitrant OMP even show higher degradation rates under oxic conditions than under anoxic conditions. This conversion is affected by the presence of dissolved organic carbon (DOC), HCO3− and NO3−, and thus was more effective in drinking water than in Milli-Q water. The reaction rate constants of the oxic UV/SO32− process in general are lower than those of a UV/H2O2 process, but in cases where the use of H2O2 is not preferred, the UV/SO32− process may be an interesting alternative.

Highlights

Advanced oxidation processes (AOP) for the removal of organic micropollutants (OMP) from water have obtained a lot of attention in the published literature over recent years (Stefan 2017; Capodaglio 2020)
Reaction kinetics In general, the conversion of a compound by UV radiation can be described with Equation (1)
In this equation C0 is the initial concentration of a compound, C is its actual concentration in the aqueous phase and H’ is the UV dose applied

Summary

INTRODUCTION

Advanced oxidation processes (AOP) for the removal of organic micropollutants (OMP) from (drinking) water have obtained a lot of attention in the published literature over recent years (Stefan 2017; Capodaglio 2020). The pH plays an important role in UV advanced reduction processes This is mainly due to the effect on the degree of dissociation of the sulphite, which results in a different UV absorption and radical formation (Jung et al 2014; Xiao et al 2017a, 2017b). At low pH values hydrated electrons may be scavenged according to Equation (5) in the Supplementary Information (Yazdanbakhsh et al 2018), which, results in the formation of a hydrogen radical This seemed to have little effect on the degradation of trichlorophenol, as this was shown to be mainly caused by the sulphite radical. For a selection of micropollutants, which are often encountered in Dutch sources of drinking water, we compared the effect of the UV/SO32À process with that of the well-known UV/H2O2 advanced oxidation process

METHODS

RESULTS AND DISCUSSION

CONCLUSIONS