Comparison of ferrate and ozone pre-oxidation on disinfection byproduct formation from chlorination and chloramination

Abstract

This study investigated the effects of ferrate and ozone pre-oxidation on disinfection byproduct (DBP) formation from subsequent chlorination or chloramination. Two natural waters were treated at bench-scale under various scenarios (chlorine, chloramine, each with ferrate pre-oxidation, and each with pre-ozonation). The formation of brominated and iodinated DBPs in fortified natural waters was assessed. Results indicated ferrate and ozone pre-oxidation were comparable at molar equivalent doses for most DBPs. A net decrease in trihalomethanes (including iodinated forms), haloacetic acids (HAAs), dihaloacetonitrile, total organic chlorine, and total organic iodine was found with both pre-oxidants as compared to chlorination only. An increase in chloropicrin and minor changes in total organic bromine yield were caused by both pre-oxidants compared to chlorination only. However, ozone led to higher haloketone and chloropicrin formation potentials than ferrate. 2 The relative performance of ferrate versus ozone for DBP precursor removal was affected by water quality (e.g., nature of organic matter and bromide concentration) and oxidant dose, and varied by DBP species. Ferrate and ozone pre-oxidation also decreased DBP formation from chloramination under most conditions. However, some increases in THM and dihaloacetonitrile formation potentials were observed at elevated bromide levels.

Three Kinetic Patterns for the Oxidation of Emerging Organic Contaminants by Fe(VI): The Critical Roles of Fe(V) and Fe(IV)

“…Emerging organic contaminants (EOCs) are a group of synthetic compounds widely present in the aquatic environment, as a consequence of various industrial and agricultural activities of human beings . Although the concentrations of EOCs are commonly observed at trace concentrations (typically ng L –1 or μg L –1 ), they have attracted increasing concerns due to their potential human and ecological health risks. − Notably, chemical oxidation is one of the most effective approaches to alleviate EOCs in raw water or municipal wastewater effluents. − Among the commonly used chemical oxidants, ferrate (i.e., Fe­(VI)) has attracted increasing attention in recent years due to its multiple functions − and great superiority over other oxidants in suppressing the formation of some specific disinfection byproducts . Fe­(VI) can not only effectively decompose various organic contaminants, − especially those containing electron-donating moieties, but also sequester the degradation products of target organic contaminants through coagulation and/or adsorption due to the in situ generation of Fe­(III). ,, Although Fe­(VI) can slowly oxidize bromide, the formation of active bromine and bromate at typical water treatment conditions is limited without a public health concern. , Over the past decades, oxidative removal of various EOCs in water by Fe­(VI) has been extensively investigated, including quantitatively determining the kinetics of EOCs degradation. − Generally, it was believed that Fe­(VI) oxidation of a specific EOC followed second-order kinetics behaviors, i.e., first-order dependence on the concentrations of both Fe­(VI) and the target EOC (eq ).…”

Generation of Iron(IV) in the Oxidation of Amines by Ferrate(VI): Theoretical Insight and Implications in Oxidizing Pharmaceuticals

“…Organic amines are key components in organic synthesis, metalloenzymatic reactions, atmospheric particles, coastal waters, and municipal and industrial wastewater discharges. − Amines are widespread in surface water because their moieties are usually found in dissolved natural organic matter and anthropogenic organic contaminants such as pharmaceuticals, personal care products, dyes, and pesticides . Amines in water resources are of concern because disinfection using chlorine and chloramine results in the formation of potentially toxic disinfection byproducts (DBPs). , Many investigators, including our group, are studying an iron-based oxidant, ferrate­(VI) [Fe VI O 4 2– , Fe­(VI)], as a preoxidant prior to disinfection by chlorination. − The application of Fe­(VI) as a preoxidant and subsequent chlorination decrease the levels of chlorinated DBPs (Cl-DBPs) because the oxidation of amine-containing constituents in water and the resulting oxidized products cannot react fully to generate Cl-DBPs. ,,− Amine moieties in pharmaceuticals also play an important role in their oxidation by Fe­(VI) in water. − For example, in the oxidation of sulfonamides, the amine moieties determined the reaction pathways that yield oxidized products. , …”

Tetracycline antibiotics as precursors of dichloroacetamide and other disinfection byproducts during chlorination and chloramination

“…Therefore, we investigated whether common pretreatments methods could reduce DCAcAm formation from tetracyclines. Pretreatment by ClO 2 pre-oxidation, UV photolysis, or the UV/chlorine advanced oxidation process is often used in water treatment to eliminate algae or micropollutants, and these methods affect DBP formation during subsequent chlor(am)ination because of transformation of DBP precursors ( Jiang et al., 2019 ; Zhang et al., 2019b ). Thus, we investigated the effects of these three pretreatment methods on DCAcAm formation during chlor(am)ination of TC.…”