Transformations of particles, metal elements and natural organic matter in different water treatment processes

Abstract

Characterizing natural organic matter (NOM), particles and elements in different water treatment processes can give a useful information to optimize water treatment operations. In this article, transformations of particles, metal elements and NOM in a pilot-scale water treatment plant were investigated by laser light granularity system, particle counter, glass-fiber membrane filtration, inductively coupled plasma-optical emission spectroscopy, ultra filtration and resin absorbents fractionation. The results showed that particles, NOM and trihalomethane formation precursors were removed synergistically by sequential treatment of different processes. Preozonation markedly changed the polarity and molecular weight of NOM, and it could be conducive to the following coagulation process through destabilizing particles and colloids; mid-ozonation enhanced the subsequent granular activated carbon (GAC) filtration process by decreasing molecular weight of organic matters. Coagulation-flotation and GAC were more efficient in removing fixed suspended solids and larger particles; while sand-filtration was more efficient in removing volatile suspended solids and smaller particles. Flotation performed better than sedimentation in terms of particle and NOM removal. The type of coagulant could greatly affect the performance of coagulation-flotation. Pre-hydrolyzed composite coagulant (HPAC) was superior to FeCl 3 concerning the removals of hydrophobic dissolved organic carbon and volatile suspended solids. The leakages of flocs from sand-filtration and microorganisms from GAC should be mitigated to ensure the reliability of the whole treatment system.

Study of the pH influence on the optical properties of dissolved organic matter using fluorescence excitation–emission matrix and parallel factor analysis

“…DOM is a heterogeneous mixture of various molecular weight aromatic and aliphatic organic compounds that contain oxygen, nitrogen, and sulfur functional groups (e.g., carboxyl, phenol, enol, alcohol, carbonyl, amine, and thiol) [1,2]. The properties of DOM strongly affect its reactivity in both natural and engineered aquatic systems [1,[3][4][5][6][7].…”

Characterization of dissolved organic matter using high-performance liquid chromatography (HPLC)–size exclusion chromatography (SEC) with a multiple wavelength absorbance detector

“…It is composed of relatively high apparent molecular weight (AMW) humic and fulvic acids, as well as low AMW proteins, organic acids, carbohydrates and other compounds (Leenheer and Croue, 2003). The molecular properties of DOM, notably its molecular weight, strongly affect its reactivity in both natural and engineered aquatic systems (Amy et al, 1987;Her et al, 2002a;Leenheer and Croue, 2003;Yan et al, 2006Yan et al, , 2007Korshin et al, 2009). High-performance liquid chromatographysize exclusion chromatography (HPLC-SEC) is one of the most widely used techniques to characterize DOM due to its important advantages, such as little need for DOM pre-concentration, small injection volume, and ease and speed of analysis (Chin et al, 1994;Her, 2003;Korshin et al, 2009).…”

Natural organic matter (NOM) removal in a typical North-China water plant by enhanced coagulation: Targets and techniques

“…The results of pilot-scale tests with AlCl 3 , PACl and HPAC were compared with the traditional coagulation strategy (a composite coagulant prepared using Tests at pilot-scale and at full-scale have shown that particles and NOM are removed synergistically with HPAC as coagulant by sequential treatment processes including pre-ozonation, coagulation, flotation and sand filtration [6,8,20]. The residual Al is relatively low [21]. Coagulant optimization such as by HPAC application can be considered as an alternative option to enhance NOM removal from high alkalinity and micro-polluted waters.…”