College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua, 321004, China.
Department of Chemical Engineering, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario, P7B 5E1, Canada.
Water Res. 2019 Feb 1;149:477-487. doi: 10.1016/j.watres.2018.11.043. Epub 2018 Nov 19.
Soluble microbial products (SMPs) are the predominate foulants determining fouling extent in membrane bioreactors (MBRs). However, exact mechanism underlying their typical fouling behaviors remains unrevealed. In this study, the typical fouling behaviors of SMPs during initial operational period of a MBR were characterized. It was found that, although being low content, SMPs rather than sludge particulates preferentially adhered to membrane surface to accumulate a gel layer, and moreover, specific filtration resistance (SFR) of SMPs was approximately 700 times larger than that of the sludge particulates at operational day 3. According to energy balance principle, a unified thermodynamic mechanism underlying these fouling behaviors of SMPs was proposed. Thermodynamic analyses demonstrated that, the attractive interaction energy strength in contact between SMPs and membrane was larger by around 3700 times than that between sludge particulates and membrane, well explaining the extremely high adhesive ability of SMPs over sludge particlulates. Meanwhile, filtration through a SMPs layer was modelled and simulated as a thermodynamic process. Simulation on an agar gel showed that, about 92.6% of SFR was originated from mixing free energy change during filtration. Such a result satisfactorily interpreted the extremely high SFR of SMPs layer over sludge cake layer. The revealed thermodynamic mechanism underlying SMPs fouling behaviors significantly deepened understanding of fouling, and facilitated to development of effective fouling control strategies.
可溶性微生物产物（SMPs）是膜生物反应器（MBRs）中决定污染程度的主要污染物。然而，其典型污染行为的具体机制仍未被揭示。本研究对 MBR 初始运行期间 SMPs 的典型污染行为进行了研究。结果表明，尽管 SMPs 的含量较低，但它们优先于污泥颗粒附着在膜表面上积累凝胶层，此外，在运行第 3 天，SMPs 的比过滤阻力（SFR）比污泥颗粒大约大 700 倍。根据能量平衡原理，提出了一个统一的热力学机制来解释这些 SMPs 污染行为。热力学分析表明，SMPs 与膜之间的接触吸引力强度大约比污泥颗粒与膜之间的接触吸引力强度大 3700 倍，这很好地解释了 SMPs 对污泥颗粒的极高粘附能力。同时，通过模拟和模拟将通过 SMPs 层的过滤过程建模为一个热力学过程。对琼脂凝胶的模拟表明，约 92.6%的 SFR 源于过滤过程中混合自由能变化。这一结果很好地解释了 SMPs 层比污泥饼层具有极高 SFR 的原因。揭示的 SMPs 污染行为的热力学机制，显著加深了对污染的理解，并有助于开发有效的污染控制策略。
