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Application of VUV/UV process for micropollutants removal in decentralized water supply systems (e.g., rural drinking water treatment) is promising while few researches by far paid attention to the performance of practical flow-through reactors. This study investigated the degradation of atrazine (ATZ), sulfamethoxazole (SMX) and metoprolol (MET) under different hydrodynamic conditions in reactors with varied internal diameters and baffle allocations. Results showed that the target micropollutants could be degraded efficiently in the flow-through VUV/UV reactors following basically the pseudo-first order kinetics (R2 ≥ 0.97). The largest degradation rate constants were found in the D35 reactor and incorporation of baffles in the D50 and D80 reactors accelerated obviously the micrpollutants degradation. The improved performances of the baffled reactors were due mainly to the elevated utilization of HO•, and a new parameter named UE HO (HO• utilization efficiency) was proposed accordingly. The calculated UE HO values of the reactors ranged between 30.2% and 69.2% with the largest found in the D50-5 reactor. This testified the usually insufficient utilization of radicals in flow-through reactors and the effectiveness of baffle implementation. Electrical energy per order (E EO) values of micropollutants degradation in the reactors were in the range of 0.104–0.263 kWh m−3 order−1. The degradation was inhibited significantly by high-concentration nitrate yet the formed nitrite concentration stayed consistently below the drinking water limitation. The acute toxicity of the micropollutant solutions increased first and leveled off afterwards during the VUV/UV treatment, as indicated by the inhibition ratios of luminescence intensity of Vibrio fischeri. [Display omitted] • Micropollutants were degraded in different flow-through VUV/UV reactors. • Impact of reactor configuration on utilization efficiency of HO.• was evaluated. • The Lowest E EO was found with a proper internal diameter and baffle allocation. • Nitrite formation in tested flow-through VUV/UV reactors was not concerning. • Acute toxicity of the solution tended to increase during VUV/UV treatment. [ABSTRACT FROM AUTHOR]

The degradation of three micropollutants (i.e., atrazine (ATZ), sulfamethoxazole (SMX) and metoprolol (MET)) was comprehensively investigated in flow-through UV/chlorine reactors. Results showed that the micropollutants degradation fitted well with pseudo-first-order kinetics (R2 > 0.92) with the order of rate constants following SMX > MET > ATZ. The developed steady-state approximation (SSA) model was roughly applicable in flow-through UV/chlorine reactors with the predictions deviated within 44%. UV photolysis here stood as the major degradation pathway for ATZ while the contribution of non-radical processes (UV photolysis and chlorination) to SMX degradation increased as the reactor internal diameter enlarged. The degradation rates were reduced to varying extents with complex water matrices (chloride, bicarbonate and dissolved organic matter (DOM)) where the inhibition from the DOM was most prominent (up to 73.6%). Although reactors with a larger internal diameter resulted in reduced degradation rate constants, the energy requirements were also lowered. The E EO values of micropollutants degradation by UV/chlorine fell mostly within 1.0 kWh m−3 order−1 in deionized water and under different water matrices. The acute toxicity was observed to be higher after UV/chlorine treatment in tap water, but still stayed low in general. This study revealed the different kinetics and mechanisms of micropollutants degradation in flow-through reactors and demonstrated the potential of the UV/chlorine process in terms of low energy consumption and acute toxicity. [Display omitted] • Micropollutants were efficiently degraded in flow-through UV/chlorine reactors. • A steady-state approximation model was developed and found approximately applicable. • Effects of reactor internal diameter and water matrices were investigated. • Variations of solution acute toxicity during UV/chlorine treatment were evaluated. [ABSTRACT FROM AUTHOR]