Investigating the significance of coagulation kinetics on maintaining membrane permeability in an MBR following reactive coagulant dosing
Investigating the significance of coagulation kinetics on maintaining membrane permeability in an MBR following reactive coagulant dosing
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DOI：
10.1016/j.memsci.2016.06.008
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发表时间：
2016-10-15
影响因子：
9.5
通讯作者：
McAdam, E. J.
中科院分区：
文献类型：
--
作者：
Autin, O.;Hai, F.;McAdam, E. J.
在这项研究中，动力学控制的絮凝体生长对维持膜通透性的影响后，反应性混凝剂的剂量是通过模型颗粒系统确定的。絮凝体的形成由加入混凝剂后的两个阶段组成：(i)最初的不稳定阶段，促进蛋白质和多糖的络合；（ii）在絮团生长阶段，聚合物络合物中捕获了粗模型颗粒（3 μ m Firefli （TM）微球）。絮凝体生长的特点是预期的时间滞后与传统的絮凝系统和生物聚合物聚集在动力学上是有利的。当混凝剂在过滤过程中加入时，中间的生物聚合物聚集体（由蛋白质和多糖组成）优先向膜运输，增加了污染。然而，当在过滤开始时投加混凝剂时，膜污染受到抑制。有人断言，通过在过滤开始时给药：(i)生物聚合物聚集的早期发展被启动，这抑制了单个生物聚合物向膜的运输；（ii）在没有发达的极化层的情况下，通过给药混凝剂，可以避免在膜上局部形成生物聚合物复合物。然而，当在过滤开始时投加混凝剂时，只有有限的絮凝体生长发生，这可以通过低施加的壁剪切速率和缺乏“极化”区域来解释，在过滤中期投加混凝剂时，表面上促进了絮凝体的生长。根据所研究的模型颗粒系统的结果，提出反应性混凝剂的最佳投加时间为：(1)停止过滤；（ii）在生物反应器内施加适度的剪切以促进混凝剂的分散；（iii）在过滤开始之前，允许有足够的接触时间来促进絮凝体生长。(C) 2016年作者。Elsevier B.V.出版
In this study, the impact of kinetically controlled floc growth on sustaining membrane permeability following reactive coagulant dosing was determined using a model particle system. Floc formation was indicated to comprise of two stages following coagulant addition: (i) an initial destabilisation phase which encouraged complexation of protein and polysaccharide; and (ii) entrapment of the coarse model particles (3 mu m Firefli (TM) microspheres) in the polymeric complex during the floc growth phase. Floc growth was characterised by an expected time lag as with conventional flocculation systems and biopolymer aggregation was kinetically favoured. When coagulant was dosed during the filtration cycle, the intermediate biopolymer aggregates (comprised of protein and polysaccharide) were preferentially transported toward the membrane increasing fouling. However, when coagulant was dosed at the onset of filtration, membrane fouling was constrained. It is asserted that by dosing at the onset of filtration: (i) early development of biopolymer aggregation is initiated which inhibits transport of the individual biopolymers to the membrane; and (ii) by dosing coagulant in the absence of a developed polarised layer, formation of biopolymer complexes local to the membrane is obviated. However, when dosing coagulant at the onset of filtration, only limited floc growth occurred which can be explained by the low applied wall shear rate and the absence of a 'polarised' region which ostensibly promoted floc growth when coagulant was dosed mid-filtration. Based on results from the model particle system studied, it is proposed that reactive coagulant dosing is best undertaken when: (i) filtration is stopped; (ii) modest shear is applied within the bioreactor to promote coagulant dispersion; and (iii) sufficient contact time is allowed to promote floc growth before commencement of filtration. (C) 2016 The Authors. Published by Elsevier B.V.