Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan.
Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan.
Water Res. 2018 Apr 15;133:255-263. doi: 10.1016/j.watres.2018.01.034. Epub 2018 Feb 3.
Coagulation is often applied as a pre-treatment for membrane processes to reduce dissolved organic matter and to prevent membrane fouling. Biopolymers (BPs) have repeatedly been reported as major organic foulants, and coagulation conditions such as pH or dose have been optimised to minimise the remaining BPs. Optimisation however remains problematic because of the complex and heterogenetic nature of BP. In this study, the behaviour of several BP fractions in a coagulation process was investigated by excitation-emission matrix-parallel factor analysis (EEM-PARAFAC) following liquid chromatography (LC)-fractionation. Using a series of jar tests, we found that BP removal depends on the type of source water, reflecting differences in charge neutralisation conditions in three samples of natural water despite nearly identical processes for removing humic substances. This result demonstrates the complexity of optimisation for BP coagulation. Fractionation of EEM-PARAFAC to BP by LC showed that at least three organic component groups (C1, C2 and C3) constitute BP. C1 is tryptophan-like organic matter that is often found in wastewater effluent, C2 is tyrosine-like organic matter that has a phenolic chemical structure, and C3 is a humic-like substance. C1 was removed thoroughly at acidic pH but not at neutral pH, while the removal of C2 was inefficient even with a significant change in pH or dose, indicating similar difficulties in a coagulation process. The difference in components C1 and C2 may partly explain the difference in efficiencies of removal of BP in water from different sources. Our investigation suggests that the optimisation or selection of appropriate pre-treatment processes for membrane systems should be substantially based on the composition of BPs (e.g., C1 and C2 components).
混凝通常作为膜过程的预处理方法，以降低溶解的有机物并防止膜污染。生物聚合物 (BPs) 已被反复报道为主要的有机污染物，并且已经优化了诸如 pH 值或剂量等混凝条件，以最大限度地减少残留的 BPs。然而，由于 BP 的复杂和异质性质，优化仍然存在问题。在这项研究中，通过液质联用（LC）分级后，采用激发-发射矩阵平行因子分析（EEM-PARAFAC）研究了混凝过程中几种 BP 级分的行为。通过一系列的 jar 试验，我们发现 BP 的去除取决于水源的类型，尽管三种天然水中去除腐殖质的过程几乎相同，但电荷中和条件的差异反映了去除腐殖质的过程。这一结果表明 BP 混凝的优化具有复杂性。EEM-PARAFAC 通过 LC 对 BP 的分级表明，至少有三个有机成分组（C1、C2 和 C3）构成了 BP。C1 是一种类似于色氨酸的有机物，通常存在于废水废水中，C2 是一种具有酚类化学结构的酪氨酸类有机物，C3 是一种类似于腐殖质的物质。C1 在酸性 pH 值下被彻底去除，但在中性 pH 值下不会去除，而 C2 的去除效率即使在 pH 值或剂量发生显著变化时也很低，这表明在混凝过程中也存在类似的困难。C1 和 C2 成分的差异可能部分解释了不同来源水中 BP 去除效率的差异。我们的研究表明，膜系统的预处理过程的优化或选择应基于 BPs 的组成（例如，C1 和 C2 成分）。
