不同材料中空纤维超滤膜处理闽江水的中试对比试验研究

针对闽江水源水,选取了三种材料的中空纤维超滤膜开展中试研究,构建了混凝+超滤一体化装置,探讨了膜材料对超滤装置的处理效果、运行稳定性、清洗方式和产水率的影响。结果表明,聚醚砜(PES)膜组件的亲水性和热稳定性较好且膜孔分布均匀,使其膜比通量(SF)是聚偏氟乙烯(PVDF)和聚丙烯腈(PAN)膜组件的两倍多、跨膜压差(TMP)受温度影响最小;运行压力低使其在能耗方面具有一定优势;PES内压膜耐酸碱性较强,其酸碱交错化学增强反冲洗(CEB)的方式能够替代柔性较好的外压膜所采用的气擦洗,但也增加了耗药量并使得产水率较另外两者低1%以上;单个运行周期内PES的纳污能力不如外压式,单个过滤周期中PES膜组件的SF衰减速率是PVDF和PAN膜组件的4~11倍;三组超滤装置出水的浊度、CODMn、氨氮均优于我国《生活饮用水卫生标准》(GB5749-2006);针对闽江水,当原水水质较好时,考虑SF和能耗方面的优势,可优先选择PES膜组件,但应根据原水水质需要加强超滤前的预处理。     

超滤工艺处理含藻湖库水的中试研究

针对湖库水在夏季藻类含量过高的情况,采用以超滤为核心的组合工艺进行处理,考察了超滤中试系统对藻类的去除效果。结果表明,超滤系统出水的浊度、CODMn、细菌数量等指标均优于GB 5749—2006《生活饮用水卫生标准》,出水浊度为0.1 NTU,CODMn平均去除率为40.0%;前加氯有助于有机物和细菌的去除,CODMn去除率提高了5.8%,膜出水的菌落总数有所减少;超滤系统出水平均藻密度为4.6×104个/L,低于卫生部推荐《饮用水源中藻类卫生标准》警戒限值,也远小于水厂工艺出水藻密度;在超滤之前增加预处理工艺能有效改善超滤过滤性能,膜过滤水厂沉后水的SF比直接过滤原水高出45%左右。超滤膜恒压运行时,0.055 MPa时的膜通量比0.040 MPa时高32%左右,但降低跨膜压差,维持相对低一些的膜通量可以使系统产水更加稳定。因此,采用以超滤为核心的组合工艺能有效地控制湖库水中的藻类,保障饮用水安全。     

炭砂过滤单元对超滤膜阻力的影响研究

为了研究炭砂过滤单元对浸没式超滤膜的影响,以北京市某给水厂的机械加速澄清池出水为研究对象,比较了"混凝沉淀/超滤"和"混凝沉淀/炭砂过滤/超滤"工艺中膜过滤单元的运行特性、膜阻力及出水水质。增加炭砂过滤单元后,跨膜压差(TMP)的上升速度得到缓解,增长率由1.23 k Pa/d下降为0.29 k Pa/d;对不同膜阻力分别进行测量并辅以扫描电镜和三维荧光技术表征膜面及出水水质,发现炭砂滤柱可以截留沉后水中的矾花,使膜的沉积阻力下降了77%;炭砂滤柱还可以有效地吸附色氨酸类蛋白质和腐殖酸等有机物,使UV254由0.026 cm-1下降到0.020cm-1,使膜的孔堵阻力下降了约90%。将炭砂过滤工艺作为膜的预处理单元,其减缓膜污染的能力优于混凝工艺。     

操作条件及运行通量对超滤膜污染的影响

从优化操作工艺和摸索长期运行零污染通量2个角度对浸没式超滤膜污染进行了研究.结果表明:曝气强度为40m3/(m2·h)时,对膜污染的去除可取得良好的效果;运行周期越短,膜污染越轻;存在一个通量范围,在此范围内,TMP和膜阻力随时间增长缓慢,一旦超出了这个范围,TMP和膜阻力便会随时间增长迅速增加.     

不同类型超滤工艺处理引黄水库水的效果对比

采用内压式超滤膜工艺中试系统,结合东营南郊水厂的预氧化/粉末活性炭/混凝/沉淀/砂滤/超滤工艺,对比研究了外压式PVC和内压式聚砜超滤膜的净化效能,以及膜通量对膜污染的影响差异.内压式聚砜膜和外压式PVC膜的出水浊度均稳定在0.02 NTU以下,粒径＞2μm的颗粒数平均为10个/mL左右;混凝沉淀、砂滤、超滤单元对CODMn和TOC均有较显著的去除效果,具有多级屏障作用,但砂滤和超滤单元对UV254没有去除作用;对以上各指标的去除效果与膜材质和超滤形式均没有显著的相关性.对于引黄水库水的微污染水质特点,经过预氧化/粉末活性炭/混凝/沉淀工艺处理后,直接进行超滤更有助于缓解膜污染,延缓跨膜压差的增长.     

浸没式膜过滤技术在再生水厂的应用研究

浸没式膜过滤(SMF)工艺应用于天津纪庄子再生水厂砂滤站改造工程,在长期连续运行过程中考察其对污水深度处理效果以及系统的运行稳定性。结果表明:系统出水水质稳定,UF膜对浊度具有较高的去除率;膜系统跨膜压差(TMP)可长期维持在较稳定的范围;通过对冬季4种运行方式进行比较,在不影响水厂正常供水的情况下,尽量设定在较低滤水流量下运行,TMP波动更稳定。浸没式膜过滤系统运行电耗约为0.05 kW·h/m3,药剂消耗成本为0.014 5元/m3,综合成本为0.06~0.07元/m3,处理成本较低。     

活性炭/超滤复合工艺中膜污染特征的研究

分别从物理清洗、化学清洗和污染物等方面研究了活性炭/超滤复合工艺中超滤膜的污染情况。结果表明,跨膜压差(TMP)从运行初期的20 kPa上升到35 kPa,提高了75%;比通量从3.8~4.6 L/(m2.h.kPa)下降到1.8 L/(m2.h.kPa),下降了50%左右。物理清洗对不可逆污染物的去除效果较差,随着运行时间的延长,比通量下降至70%左右,跨膜压差升高幅度达100%。经过化学清洗后TMP和比通量的恢复率分别为82%~100%和86%~100%。超滤膜污染是由有机物、微生物和金属离子共同所致的综合性污染,包括Fe、A l等高价金属离子,Ca、Mg等二价离子,以及烷烃和芳香烃等小分子有机物。有机物不仅沉积在膜表面,而且也造成了膜孔堵塞;Fe、A l等高价金属离子主要吸附、沉积在膜内壁,而Ca、Mg等二价离子在膜内壁表面以及膜过滤孔隙中都有吸附、沉积。     

混凝/膜过滤过程中泥饼层对膜污染的影响研究

混凝/膜过滤过程可以分离、浓缩污水中有机物,有望实现生活污水的直接处理。但混凝/膜过滤过程中形成的化学泥饼层对膜污染的影响复杂。通过超滤杯过滤试验,证实了混凝/膜过滤过程中形成的化学泥饼层可以提高膜通量,并能增强有机物截留效果,减缓膜的不可逆污染。在泥饼层过滤模式下,四次过滤后膜通量能够恢复到初始通量的85%,这对设计有自动水力清洗设备的膜混凝反应器的长期运行具有现实意义。     

PVDF压力式膜组件深度处理市政污水的中试

采用PVDF压力式膜组件对经过生化处理的市政污水进行深度处理,重点考察了对污染物的去除效果、跨膜压差(TMP)随运行时间的变化及其影响因素.研究表明:在产水通量恒定为60 L/(m<'2>·h)的条件下,膜组件的跨膜压差基本上在25～60 kPa之间变化;常规的维护性化学加强反洗(CEB)对恢复膜通量、降低跨膜压差的效果很好,在连续运行60 d期间只进行了一次化学清洗;过滤出水的浊度<0.2 NTU,SDI<3,对COD的去除率>40%;在水温为6～16℃的秋冬季,耗电量约为0.2 kW·h/m<'3>.因此,PVDF压力式膜组件可用于市政污水的深度处理,可实现水资源的重复利用.     

超滤膜的零污染通量及其在城市水处理工艺中的应用

对于超滤膜在城市水处理工艺中的应用,选择合适的膜通量和控制膜污染是其成功的关键所在。围绕上述关键点,结合城市超滤水厂的运行要求,系统论述了超滤膜零污染通量和经济通量的关系,并以东营超滤水厂为例,开展了超滤膜的零污染通量生产性试验,确定了该水厂在不同条件下的超滤膜零污染通量。超滤膜零污染通量相关内容的研究将可能成为膜技术发展的一个新方向。     

改性PVDF中空纤维膜处理压裂返排液研究

针对中空纤维膜应用于水力压裂返排液处理时存在的膜污染严重、通量衰减快、影响处理效率等问题,研究了PVDF固含量、凝固浴温度等因素对PVDF膜性能的影响,通过非溶剂致相分离法制备了PVDF中空纤维膜,并采用表面接枝技术,对PVDF中空纤维膜进行了表面亲水化改性。压裂返排液吸附实验结果表明,表面接枝降低了PVDF的接触角,提高了膜的亲水性。与未接枝改性的PVDF膜相比,亲水改性后的PVDF膜表面吸附的压裂返排液更少。将亲水性中空纤维膜用于页岩气水力压裂返排液的过滤处理,应用结果表明其对压裂返排液中的总铁、SS、浊度、细菌去除率达到90%以上,长时间运行后的通量保持率高,有较好的抗膜污染性。     

浸入式膜系统的操作条件对膜污染的影响研究

采用浸入式膜处理滦河水,考察了膜系统的操作条件对膜污染的影响。结果表明:适当降低膜通量对膜处理系统的稳定运行起关键作用,试验条件下,膜通量为53.3L/(m2.h)、过滤周期为30min较适宜。提高曝气强度和水反冲洗强度可有效提高反冲洗效果,改善膜污染。浸入式膜对原水水质有较强的适应能力,可适当减少反冲洗排放次数,试验条件下,采用四轮一排较为可行。相比三氯化铁,聚合铝更适合作为PVDF膜的混凝预处理药剂。     

Identification and understanding of fouling in low-pressure membrane (MF/UF) filtration by natural organic matter (NOM)

An understanding of natural organic matter (NOM) as a membrane foulant and the behavior of NOM components in low-pressure membrane fouling are needed to provide a basis for appropriate selection and operation of membrane technology for drinking water treatment. Fouling by NOM was investigated by employing several innovative chemical and morphological analyses.

Source (feed) waters with a high hydrophilic (HPI) fraction content of NOM resulted in significant flux decline. Macromolecules of a relatively hydrophilic character (e.g. polysaccharides) were effectively rejected by low-pressure membranes, suggesting that macromolecular compounds and/or colloidal organic matter in the hydrophilic NOM fraction may be a problematic foulant of low-pressure membranes. Moreover, the significant organic fouling that is contributed by polysaccharides and/or proteins in macromolecular and/or colloidal forms depends on molecular shape (structure) as well as size (i.e. molecular weight). More significant flux decline was observed in microfiltration (MF) compared to ultrafiltration (UF) membrane filtration. MF membrane fouling may be caused by pore blockage associated with large (macromolecular) hydrophilic molecules and/or organic colloids. In the case of UF membranes, the flux decline may be caused by sequential or simultaneous processes of surface (gel layer) coverage during filtration. Morphological analyses support the notion that membrane roughness may be considered as a more important factor in membrane fouling by controlling interaction between molecules and the membrane surface, compared to the hydrophobic/hydrophilic character of membranes. Membrane fouling mechanisms are not only a function of membrane type (MF versus UF) but also depend on source (feed) water characteristics.     

两种不同材质超滤膜处理饮用水的综合性能研究

研究了两种不同材质超滤膜处理饮用水的综合性能。结果表明,聚醚砜(PES)膜对CODMn及TOC的去除效果优于聚偏氟乙烯(PVDF)膜;PES与PVDF膜对浊度的去除效果相差不大,大部分出水浊度小于0.10 NTU;PES和PVDF膜对UV254无去除效果;PVDF膜比PES膜的跨膜压差高15%左右,且抗污性能比PES膜强,其电耗水平比PES膜高50%左右。     

High-performance thin-layer hydrogel composite membranes for ultrafiltration of natural organic matter

Thin-layer hydrogel composite (TLHC) ultrafiltration (UF) membranes were synthesized by photo-grafting of either poly(ethylene glycol) methacrylate (PEGMA) or N,N-dimethyl-N-(2-methacryloyloxyethyl-N-(3-sulfopropyl) ammonium betaine (SPE) onto commercial polyethersulfone (PES) UF membranes. The performance of TLHC UF membranes was evaluated for natural organic matter (NOM) filtration and compared to commercial PES UF membranes. The fouling evaluation was done by investigation of membrane-solute interactions (adsorptive fouling) and membrane-solute-solute interactions (UF). The results suggest that the TLHC membranes convincingly displayed a higher adsorptive fouling resistance than unmodified PES UF membranes. In long-term stirred dead-end UF, a much lower fouling was observed for TLHC membranes than for commercial membranes with the same flux and rejection. Further, water flux recovery was also much higher. An analysis using an existing blocking model was performed in order to elucidate the effect of a polymer hydrogel layer on fouling mechanism as well as cake layer characteristics. The TLHC membranes synthesized by photo-grafting of PEGMA (40 g/L) and PEGMA with a low concentration of cross-linker monomer in the reaction mixture (ratio: 40/0.4 (g/L)/(g/L)) showed a much better performance than the other composite membranes. Those membranes could reduce the cake resistance on the membrane surface. This work has relevance for the design of high-performance UF membranes for applications in water treatment.     

SMBR在次临界通量下的运行特性

利用“通量阶式递增法”测定了两种膜组件的临界通量,在此基础上考察了次临界通量下的运行特性。试验发现,次临界通量操作下的膜污染过程具有明显的两阶段特征,与第一阶段跨膜压差(TMP)平缓直线上升相对应的膜污染机制主要是膜孔堵塞和凝胶层污染,与第二阶段TMP剧烈直线上升相对应的膜污染机制则是颗粒沉积层污染;先清水冲洗再化学清洗的方式能有效恢复膜的过滤能力,其中清水冲洗能有效去除颗粒沉积层污染,而化学清洗则能有效去除膜孔堵塞和凝胶层污染。     

Comparison of humic acid rejection and flux decline during filtration with negatively charged and uncharged ultrafiltration membranes

Increasingly stringent regulations for drinking water quality have stimulated the ultrafiltration (UF) to become one of the best alternatives replacing conventional drinking water treatment technologies. However, UF is not very effectively to remove humic acid due to the comparatively larger pore size compared to the size of humic acid. Fouling issue is another factor that restricts its widespread application. In this study, rejection of humic acid and flux decline were compared with essentially neutral, negatively charged version of a regenerated cellulose membrane, in which electrostatic interaction was explored for a better humic acid removal and less fouling. Solution environment, including ionic strength, pH and calcium ion concentration, affecting humic acid removal and flux decline on negatively charged and neutral membranes was also compared. Results indicated that the appropriate charge modification on the neutral UF membrane could be an effective way for better removal of NOM and reduction of the membrane fouling due to the electrostatic interactions with the combination effect of membrane pore size. Electrostatic interactions are significant important to achieve high humic acid removal and less fouling, and to improve the water quality and protect people’s health.     

Effects of magnetic ion exchange pretreatment on low pressure membrane filtration of natural surface water

Magnetic ion exchange (MIEX) pretreatment has been increasingly employed by water treatment plants for removal of dissolved organic carbon (DOC). In this study, the effects of MIEX pretreatment on low pressure membrane filtration of natural surface water were investigated under different feedwater qualities, membrane properties, and MIEX dosing conditions. Regardless of feedwater DOC, moderate decrease in the total and hydraulically irreversible fouling was observed for a polyvinylidene fluoride (PVDF) microfiltration membrane and a polyethersulfone ultrafiltration (UF) membrane after MIEX pretreatment, which was coincident with moderate removals of high molecular weight DOC in the feedwaters. Comparatively, the fouling of a PVDF UF membrane did not decrease after MIEX pretreatment, revealing the impact of membrane properties on membrane fouling in the presence of MIEX pretreatment. Reuse of virgin or regenerated MIEX resulted in similar membrane fouling as observed with single use of the virgin MIEX. The level of DOC removal by MIEX was similar to the removal of MS2 bacteriophage spiked in the feedwater, suggesting a potential similarity in the removal of organic and microbial particles. In conclusion, MIEX pretreatment was effective for DOC removal, but less effective in controlling short-term membrane fouling or removing viruses.     

超滤膜用于水厂现有工艺时SF的衰减研究

采用混凝/沉淀/超滤膜工艺处理滦河水,考察超滤膜在不同工艺参数下运行时比通量(SF)的衰减情况,旨在为评估超滤膜用于水厂现有工艺时运行的可靠性和长期运行的可能性提供依据。结果表明:在投加助凝剂HCA时,对超滤膜进行定期的NaClO溶液(浓度为200mg/L)浸泡,SF的衰减速率较小;在超滤膜运行23.5h、浸泡30min的条件下,投加助凝剂HCA时的SF衰减速率低于未投加HCA时的;当以泡花碱为助凝剂,且进水中NaClO的浓度为1mg/L时,投加泡花碱时的SF衰减速率比未投加时的大;降低通量能够有效减缓SF的衰减速率。     

Investigation of the effect of coagulation bath composition on PVDF/CA membrane by evaluating critical flux and antifouling properties in lab‐scale submerged MBR

Ultrafiltration membranes were prepared from blends of poly(vinylidene fluoride) (PVDF)/cellulose acetate (CA) via phase inversion method. The effect of different coagulation bath compositions on the morphology and performance of the blend membrane prepared from casting solution of PVDF/CA with ratio of 80/20 was investigated using sewage wastewater. NaCl and ethanol were used as additives of coagulation bath. Fouling analysis was conducted with Bovine Serum Albumin solution and critical flux evaluation was performed using a lab‐scale membrane bioreactor. In terms of morphological structure, the macrovoids decreased and changed to finger‐like structure. The irreversible fouling reduced and the flux recovery ratio (FRR) of the modified membranes increased remarkably while the reversible fouling caused by deposition of foulants on the surface of the membranes increased. The maximum values of FRR and critical flux of irreversibility were reached by the membrane which was prepared in the coagulation bath containing the highest concentration of NaCl.