Comparison of UV‐Cl and UV‐H₂O₂ advanced oxidation processes in the degradation of contaminants from water and wastewater: A review

Abstract

Applications of advanced oxidation processes (AOPs) in water and wastewater treatment have been the subject of growing interest throughout the last decade. Although UV/hydrogen peroxide (UV‐H2O2) is the most established technology among the UV‐AOPs, UV‐chlorine (UV‐Cl) is emerging as a reliable and potentially more cost‐effective alternative. Recent studies have indicated that UV‐Cl processes may be more efficient and economically favourable for the degradation of some chemicals of emerging concern from contaminated water. Moreover, in terms of the formation of disinfection by‐products (DBPs), UV‐H2O2 seems to have no superiority over UV‐Cl. This said, more investigation in the assessment of genotoxicity and cytotoxicity of DBPs is required. Additionally, more pilot‐scale and full‐scale studies are required to establish UV‐Cl as a reliable alternative to UV‐ H2O2. This paper compares UV‐Cl and UV‐H2O2 AOPs for the degradation of intractable chemicals from water and wastewater based on the practical considerations of efficiency, cost, DBP formation, kinetics and sensitivity to water matrix variability. Finally, various modelling approaches to UV‐Cl have been reviewed. This review showed that UV‐Cl is superior to UV‐H2O2 in terms of degradation efficiency and cost effectiveness and can be a robust alternative in many UV‐AOPs applications.

Enhanced UV/H2O2 System for the Oxidation of Organic Contaminants and Ammonia Transformation from Tannery Effluents

“…In a UV/peroxide process, the removal of COD and BOD occurs through a combination of oxidation and biodegradation processes. The hydroxyl radicals produced by the UV/peroxide reaction attack and oxidize the organic pollutants, breaking them down into simpler, biodegradable compounds [37], yielding an effluent that microorganisms can potentially use as the pollutant load has decreased to a level where biodegradation processes can occur, further reducing the pollutant load [38]. Table 9 shows the removal percentages achieved in this research compared to other AOPs used for tannery water treatment.…”

“…In this study, COD and color removal results were relatively lower than those of Saranya et al [39], while removal rates for Cr, N-NH3, and TSS were lower than those attained in this study; [40] applied a UV//H2O2 process in the fluxes of a tannery and found COD removals of 18.8%, BOD 30.2%, TSS 49%, Cr 65.7%, and chlorides 43%, which were lower than those reported in this study; nevertheless, color removal was greater compared to that achieved in this research; [41] reported the implementation of two AOPs (UV/H2O2 and TiO2/H2O2/UV) in which they evaluated the removal of COD, color, and N-NH3 showing removals of 18.8%, 67.36%, and 78.8%, respectively, for the UV/H2O2 process and 68.3% for COD, 91.5% for color and 90.7% for N-NH3 in the TiO2//H2O2/UV system, it can be seen that comparing the results with this study, the UV//H2O2 process obtained lower efficiencies while the TiO2 mediated system obtained removals above the system In a UV/peroxide process, the removal of COD and BOD occurs through a combination of oxidation and biodegradation processes. The hydroxyl radicals produced by the UV/peroxide reaction attack and oxidize the organic pollutants, breaking them down into simpler, biodegradable compounds [37], yielding an effluent that microorganisms can potentially use as the pollutant load has decreased to a level where biodegradation processes can occur, further reducing the pollutant load [38]. Table 9 shows the removal percentages achieved in this research compared to other AOPs used for tannery water treatment.…”