Cleaning protocol for a FO membrane fouled in wastewater reuse
Cleaning protocol for a FO membrane fouled in wastewater reuse
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DOI：
10.1080/19443994.2013.795345
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发表时间：
2013-07-01
影响因子：
1.1
通讯作者：
Amy, Gary
中科院分区：
文献类型：
--
作者：
Linares, Rodrigo Valladares;Li, Zhenyu;Amy, Gary
正渗透（FO）是一种新兴的技术，可应用于水回用应用中。渗透是一种自然过程，其能耗低于反渗透（RO），因此可以在低压RO之前用作稀释过程;预计它将与目前使用微滤/超滤和RO的先进水回用技术竞争。本研究的重点是评估在以FO模式工作的浸没式系统的操作期间，不同清洗程序去除FO膜表面的污染的效率（活性层（AL）面对进料溶液），用于二级废水流出物（SWWE）回收，使用海水作为汲取溶液（DS），其将被稀释并且可以进一步被供给到低压RO单元以产生淡水。预计天然有机物（NOM）污染会影响AL，而对于支撑层（SL），透明的外聚合物颗粒（TEP）由于其粘性和增强海水中其他污垢在膜表面上的附着的倾向而被用作污染的指标。的NOM污垢层的组合物进行了适当的表征后，与有机碳检测（LC-OCD），显示生物聚合物和蛋白质样物质的主要成分的液相色谱仪。NOM污垢表现出较高的水力可逆性后，观察到的通量下降25%，高达89.5%时，原位空气冲刷15分钟作为清洗技术。用Alconox（一种含有磷酸盐的工业洗涤剂）和EDTA钠的混合物进行化学清洗，可提高可逆性（93.6%）。使用4%NaCl溶液和去离子水的渗透渗透压被证明是无效的，以恢复通量，由于盐扩散现象发生在AL。部分的通量，不能被恢复是由于TEP污垢的SL，这形成集群清晰可识别的光学显微镜和TEP特定的染色/染色的膜。测试了两种溶液来代替SL进行清洁：1%NaOCl溶液和用于清洁AL的相同洗涤剂溶液。前一种试剂损害了FO膜的完整性，如通量和电导率测量所证明的;后一种试剂回收了94.5%的通量，表明FO膜的化学不可逆结垢约为5.5%，这可能与生物聚合物在AL上的吸附和一些TEP残留在SL上有关。AL的物理清洗（空气冲刷）被证明是控制污垢的最有效方法。
Forward osmosis (FO) is an emerging technology which can be applied in water reuse applications. Osmosis is a natural process that involves less energy consumption than reverse osmosis (RO), and therefore can be applied as a dilution process before low-pressure RO; it is expected to compete favourably against current advanced water reuse technologies that use microfiltration/ultrafiltration and RO. The focus of this research was to assess the efficiency of different cleaning procedures to remove fouling from the surface of a FO membrane during the operation of a submerged system working in FO-mode (active layer (AL) facing feed solution) intended for secondary wastewater effluent (SWWE) recovery, using seawater as draw solution (DS), which will be diluted and can further be fed to a low-pressure RO unit to produce fresh water. Natural organic matter (NOM) fouling was expected to affect the AL, while for the support layer (SL), transparent exopolymer particles (TEP) were used as indicators of fouling due to their stickiness and propensity to enhance the attachment of other foulants in seawater on the membrane surface. The composition of the NOM fouling layer was determined after proper characterisation with a liquid chromatograph coupled with organic carbon detection (LC-OCD), showing biopolymers and protein-like substances as the main constituents. NOM fouling showed high hydraulic reversibility after a 25% flux decline was observed, up to 89.5% when in situ air scouring for 15min was used as a cleaning technique. Chemical cleaning with a mixture of Alconox, an industrial detergent containing phosphates, and sodium EDTA showed to increase the reversibility (93.6%). Osmotic backwash using a 4% NaCl solution and DI water proved to be ineffective to recover flux due to the salt diffusion phenomena occurring at the AL. Part of the flux that could not be recovered is attributable to TEP fouling on the SL, which forms clusters clearly identifiable with an optical microscope and TEP-specific dyeing/staining of the membrane. Two solutions were tested to clean in place of the SL: a 1% NaOCl solution and the same detergent solution used to clean the AL. The former agent compromised the integrity of the FO membrane, as proved with flux and conductivity measurements; 94.5% of flux was recovered with the latter agent, showing that chemically irreversible fouling for the FO membrane is on the order of 5.5%, which might be associated with the adsorption of biopolymers on the AL and some TEP residuals on the SL. Physical cleaning (air scouring) of the AL proved to be the most effective way to control fouling.