Development of Surrogate Parameters to Evaluate Micropollutant Abatement and N-Nitrosodimethylamine (NDMA) Formation Reduction by Permanganate Preoxidation

Abstract

UV absorbance at 254 nm (UV254) and electron-donating capacity (EDC) abatements were developed as novel surrogate parameters to evaluate the degradation of micropollutants in different water samples after direct permanganate (Mn­(VII)) oxidation or Mn­(VII) oxidation with filtration. UV254 abatement was mainly attributed to the enhanced coagulation effect of manganese oxidation products. EDC was abated more efficiently than UV254 because the reaction products of Mn­(VII) oxidation by accepting electrons still absorb at 254 nm. UV254 and EDC abatements during direct Mn­(VII) oxidation were compared to those resulting from other preoxidation processes including ozonation, peroxomonosulfate (PMS) oxidation, and PMS-Fe­(II) oxidation. UV254 was significantly abated during ozonation with tert-butanol while EDC abatement was notable after direct Mn­(VII) oxidation. The humic-like fluorescent value first increased slightly and decreased significantly with increasing Mn­(VII) dose. The assimilable organic carbon formation increased during Mn­(VII) oxidation with filtration. The relative abatement of selected micropollutants showed good one-phase correlations with UV254 or EDC in humic acid solution and lake water and two-phase correlations in groundwater. During Mn­(VII) oxidation and filtration of lake water followed by postchloramination, N-nitrosodimethylamine (NDMA) and total N-nitrosamine formation decreased with increasing specific Mn­(VII) dose. NDMA formation abatement correlated well with EDC abatement.

Electron Donating Capacity: A Promising Surrogate Indicator for the Optimization of Oxidative Water Treatments

“…132 A similar two-phase relationship is also observed for nitrogenous DBPs, absorbable organic halide, haloacetic acids, and total organic chlorine, which could be explained by the mechanisms previously mentioned. 32,72,112 The twophase relationship becomes more pronounced especially for a relatively smaller chlorine dosage. 31,32 Rouge et al 32 further evaluated whether the correlation between EDC reduction and DBP formation depended on preoxidation type.…”

“…Similar results are also obtained in lake water. 112 Comparatively, Fe(VI) also exhibits an ability to abstract electrons similar to that of Mn(VII), but its EDC reduction is less efficient than that of Mn(VII) at equivalent specific doses. The lower-than-expected oxidation efficiency is likely due to the rapid autodecomposition of Fe(VI) and its reduced products, resulting in less oxidant exposure.…”

“…However, the influence of enhanced coagulation is not evident in lake water. 112 5.3. Sulfate Radical Oxidation.…”

“…During an oxidation treatment in which quinone-type compounds are formed, the trend will become more pronounced. 112,126 6.2. Prediction of Oxidant Demand and DBP Formation.…”

“…Changes in relative residual UV 254 (UV 254 /UV 254,0 ) with relative residual EDC (EDC/EDC 0 ) in various oxidation processes. ,− ,,,,,,,,, …”