Coagulation of surface water: observations on the significance of biopolymers

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Title: Coagulation of surface water: observations on the significance of biopolymers
Authors: Graham, NJD
Su, Z
Liu, T
Yu, W
Li, X
Item Type: Journal Article
Abstract: Although the treatment of natural surface waters by coagulation has been investigated extensively, the detailed interaction between natural organic matter and alum is still not adequately understood or predictable, owing to the complexity of different components of the organic matrix and the conditions during coagulation. In this paper, we present the results of a novel approach to the study of the topic, which involved the progressive separation of organic components according to size, followed by coagulation of the filtrate solution, in order to expose the influence of particular organic fractions. Using two natural water sources, representative of lake and river waters, solutions of different organic content were obtained by progressively filtering the source waters using membranes of decreasing pore size; viz. microfiltration (MF), ultrafiltration (UF), and two grades of nanofiltration (NF). While MF had little impact on the range of organics present, UF was able to separate biopolymers (MW > 100 kDa), and NF had a substantially impact on the separation of medium-high MW (1–10 kDa) substances. The results of the coagulation tests showed that the size of flocs was substantially greater when biopolymers were present, suggesting their beneficial role in bridging precipitated Al(OH)3 nanoparticles. For the smaller organic fractions (<10 kDa), the results showed a trend of increasing floc size with decreasing organic MW and concentration, but the trend was minor and may be explained by charge effects. Very similar results were found with both water sources, which support the main finding that biopolymers have an important influence on floc formation.
Issue Date: 13-Sep-2017
Date of Acceptance: 13-Sep-2017
ISSN: 0043-1354
Publisher: Elsevier
Start Page: 144
End Page: 152
Journal / Book Title: Water Research
Volume: 126
Copyright Statement: © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (
Sponsor/Funder: Engineering & Physical Science Research Council (E
Funder's Grant Number: 144356 (EP/N010124/1)
Keywords: Biopolymer
Flocculation index (FI)
Membrane separation
Natural organic matter
Surface water
MD Multidisciplinary
Environmental Engineering
Publication Status: Published
Appears in Collections:Faculty of Engineering
Civil and Environmental Engineering

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