Activated carbon and organic matter characteristics impact the adsorption of DBP precursors when chlorine is added prior to GAC contactors. (1st October 2020)

• Record Type: Journal Article
• Authors: Erdem, Cagri Utku; Ateia, Mohamed; Liu, Chao; Karanfil, Tanju
• Is Part Of: Water research. Volume 184(2020)
• Publication Date: 2020-10-01
• Subjects: Activated carbon -- Porosity -- Pre-chlorination -- Disinfection byproducts -- Br-DBPs -- Natural organic matter -- Effluent organic matter; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2020.116146
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: Pre-chlorination (i.e. dosing chlorine prior to granular activated carbon (GAC) contactors) was recently introduced as a promising method to reduce the formation of disinfection byproducts (DBPs). However, our understanding on the effect of natural organic matter (NOM) and GAC characteristics on pre-chlorination efficiency is still elusive. Thus, we have designed this systematic study to investigate the effects of GAC characteristics (i.e. surface area, pore size, and surface charge) on the subsequent reduction of DBP formation using five well-characterized adsorbents with three different NOM under three initial Br − concentrations. The results revealed that the adsorption of halogenated DBPs precursors mostly occurs in the mesoporous region (i.e. 2 nm < pore size <50 nm) of the adsorbents. Subsequently, pre-chlorination before treatment with HD3000 (i.e. GAC with the highest mesoporous surface area) decreased the formation of DBPs by 58%. Furthermore, oxidation of GAC increased the surface acidity and negatively impacted the adsorption of halogenated DBP precursors, which suggests basic GACs as promising adsorbents when applying pre-chlorination. In addition, experiments with different NOM showed that pre-chlorination was effective with higher aromatic NOM (i.e. high specific ultraviolet absorbance (SUVA254 )). However, pre-chlorination of NOM with low SUVA254 has decreased the adsorption of some DBP precursors which resulted in increased formations of haloacetic acid (HAA) and total organic halogen (TOX). Also, experiments with effluent organic matter (EfOM) showed that pre-chlorination did not increase the adsorption of DBP precursors in low SUVA254 wastewater effluents. Besides, increasing initial Br − concentration increased the formation of brominated DBPs (Br-DBPs) and the adsorbed Br-DBP precursors. This study gives in-depth understanding of the mechanisms, advantages, and limitations of pre-chlorination as a potential method to control DBPs formation. Graphical abstract: Image 1 Highlights: Pre-chlorination was tested under various experimental conditions, GACs and fibers. Halogenated DBP intermediates adsorbed mostly at mesoporous region of the adsorbent. Pre-chlorination was effective to NOM with high SUVA254, but not on low SUVA254 NOM. Pre-chlorination increased the adsorption of brominated DBP precursors.