Abstract

Dissolved organic matter (DOM) in treated water was fractionated using solid phase extraction (SPE) into six fractions based on polarity and charge; namely, hydrophobic neutrals (HoN), hydrophobic bases (HoB), hydrophobic acids (HoA), hydrophilic bases (HiB), hydrophilic acids (HiA) and hydrophilic neutrals (HiN). HiN fraction was observed to be the highest fraction, accounting for 35% and HoA was found to be the second most abundant fraction in treating water, accounting for 22%. The individual region in fluorescence excitation-emission matrix (F-EEM) result demonstrated that the treated water contained predominantly, humic acid-like material, fulvic acid-like compounds and soluble microbial products (SMPs).

Introduction

Dissolved organic matter (DOM) is a complex mixture of heterogeneous compounds and can be divided into humic compounds and non-humic compounds. Typically, most of the substances containing DOM have anion characteristic, resulting from carboxylic and phenolic groups such as humic and fulvic acids, whereas the remaining of the DOM comprises of neutral substances, for example, carbohydrates and proteins (Leenheer and Croué, 2003; Kim and Yu, 2005). Moreover, DOM can be characterized by DOM segregation into hydrophobics, which comprise of humic and fulvic acids, and hydrophilics, which consist of polysaccharides, proteins and amino acids.

Dissolved organic carbon (DOC) plays an important role in carbon cycle as it acts as primary food sources for aquatic ecosystems. This was due to DOM acts as a source of organic matter in marine environments, as an carbon/energy source for microorganisms and bacteria in aquatic ecosystems (Imai et al., 2002). DOC is the most commonly used to quantify DOM in treating water (Chen et al., 2003). The U.S. Environmental Protection Agency (US.EPA) proposed DOC as a representative for measurement DBP precursors (Marhaba and Van, 2000). DOC in treating water is very crucial because DOC has negative affected on water quality since it could react with chloride and bromide to form disinfection by-products (DBPs) such as trihalomethanes (THMs), haloacetic acids (HAAs) and brominated DBPs (Zhang et al., 2009; Tian et al., 2013).

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