活性焦吸附对反渗透浓水膜蒸馏减排工艺的影响

本研究采用膜蒸馏(MD)技术,对煤化工废水2套处理工艺——(1)"混凝-超滤(UF)-反渗透(RO)工艺"和(2)"混凝-活性焦(AC)吸附-超滤-反渗透工艺"的RO浓水进行浓缩。通过对比分析MD的膜通量、产水水质以及膜污染等指标,重点考察AC吸附预处理对后续MD工艺的影响。结果表明,AC吸附作为前置膜处理工艺,可有效降低污染物在膜表面的沉积,减少膜润湿现象,并提高膜通量。GC-MS分析表明,AC能有效吸附废水中的酮类、醇类、酯类以及杂环类等挥发性有机物,降低MD过程中挥发至产水侧的有机物浓度,从而提高MD产水水质。     

直接接触式膜蒸馏浓缩处理高浓度发酵废液效能

采用直接接触式膜蒸馏工艺(DCMD)浓缩处理高浓度发酵废液,在热侧温度65℃、冷侧温度30℃条件下,连续运行21 h,考察了浓缩过程中产水通量、产水侧COD和TOC浓度变化及蛋白质浓缩效果。结果表明,产水通量随运行时间延长而下降且降速较快,15 h内由17.1 kg/(m~2·h)降至8.9 kg/(m~2·h);经去离子水冲洗,产水通量可恢复至56.1%。产水中COD和TOC浓度随处理时间延长而不断增大。此外,原水与膜蒸馏出水中GC-MS分析结果也表明,随运行时间延长,原水中有更多种类的有机物进入产水侧,主要为挥发性有机物。对膜内表面进行扫描电镜-能谱(SEM-EDS)分析发现,膜内表面有块状沉积物出现,主要成分为有机物,含有少量的无机物。DCMD运行21 h后,废液体积浓缩8.3倍,有用组分蛋白质浓缩6.9倍,COD和TOC的去除率均达95%以上。     

减压膜蒸馏法处理石煤提钒废水

利用减压膜蒸馏设备处理石煤提钒废水，分别比较了废水经预处理前后，料液温度、流量、渗透侧真空度等操作条件对膜通量和截留率的影响。测定了不同浓缩倍数情况下膜通量的变化。实验表明，进料温度升高会使膜通量增加，温度为65℃时，热效率最高为70．1％。提高料液流量或真空度都会使膜通量增加。废水经VMD处理产出的淡水电导率均在10μS／cm以下，脱盐率可达99．98％以上。在温度为70％、流量为60L／h、真空度为0．095MPa时，石煤提钒废水经预处理后的废水膜通量为11．359kg／（m^2·h），浓缩10倍时，膜通量仍有3．185kg／（m^2·h）。     

多效膜蒸馏技术浓缩回收废水中的二甲基亚砜

利用具有内部潜热回收功能的气隙式多效膜蒸馏(MEMD)组件对含二甲基亚砜(DMSO)的化纤废水进行了浓缩回收研究,考察了料液中DMSO浓度、进料流量、进料温度和膜侧进口温度对膜通量、造水比、分离因子和回收率的影响。结果表明,多效膜蒸馏可以将DMSO废水浓缩至200~300 g/L;初始浓度为6.2 g/L时,造水比和分离因子最高值分别为12.4和76.0;虽然膜通量、造水比和分离因子均随料液浓度增大而下降,但是当DMSO浓度达到200 g/L时,膜通量、造水比、分离因子仍分别高达3.74 L/(m2·h)、7.1、32.1;在整个浓缩过程中,回收率维持在99.6%以上;当DMSO废水浓缩达到150 g/L以上时,含有少量DMSO的渗透液可作为二次料液继续用MEMD过程浓缩。膜组件在连续运行的1个月内保持了良好的操作性能。该实验研究表明,多效膜蒸馏过程可以高效节能地浓缩回收化纤废水中的DMSO。     

活性焦吸附对煤化工废水膜处理工艺的影响

煤化工废水经过生化处理后一般难以达到回用标准，须采用有效的深度处理工艺才能实现废水的资源化利用。通过对比研究方式，采用“混凝-超滤-反渗透工艺”及“混凝-活性焦吸附-超滤-反渗透”2种处理工艺，考察了活性焦吸附对后续膜处理工艺的影响。结果表明，活性焦对废水中的芳香族类等主要污染物具有很好的吸附性能，混凝出水经活性焦吸附后进人膜系统可有效减缓膜污染，降低膜通量的衰减程度并提高产水水质，因此，将活性焦吸附用于煤化工废水膜系统的前处理，采用“混凝-活性焦吸附-超滤-反渗透工艺”深度处理煤化工废水是有效可行的。     

平板膜污泥浓缩工艺操作条件的优化研究

为了解决传统污泥浓缩存在的问题,采用平板膜污泥浓缩(MST)工艺进行污泥浓缩,在浓缩污泥的同时实现中水回用.采用正交试验和层次分析法分析评价操作条件对MST工艺的影响.正交试验选择了膜通量、曝气量和抽停比3个操作条件.结果表明,针对污泥浓缩效果、出水水质和曝气量3个不同的考核指标,工艺具有不同的最佳操作条件;整个试验过程中出水浊度小于1,COD在30mg/L左右,氨氮小于5mg/L,基本满足城市杂用水水质标准.采用层次分析法选择出了MST工艺的最佳操作条件为:曝气量1.0 m3/h,膜通量18L/(m2·h),抽停比10min:2min.     

厌氧膜生物反应器处理酒厂废水运行特性研究

在一体式平板厌氧膜生物反应器处理酒厂废水的试验中,研究了污染物的去除效果和平板膜组件的运行、污染情况.试验结果表明,COD容积负荷为3～7 kg/(m3·d)、水力停留时间(HRT)为16 h时,平均COD去除率达94.2%;在膜通量为4.6 L/(m2·h)、上升流速为2.5 m/h的条件下,平板膜组件能够连续运行18～20 d;在该试验中临界通量和临界上升流速分别为10～15 L/(m2·h)和5.0m/h,平板膜组件应该在这两个临界值之下运行.膜过滤阻力分析测试结果表明,泥饼层阻力是总阻力的最大组成部分.     

超滤/反渗透双膜技术深度处理印染废水

由于印染废水具有高盐度,可生化性差,使常规方法难于处理完全.采用超滤和反渗透双膜技术处理实际印染废水,考察了不同超滤膜对废水的预处理性能,研究了BW30和CPA2两种反渗透膜在不同操作条件下对印染废水的处理效果,并分析了相关膜通量下降的原因.结果表明,超滤能有效地去除废水浊度和大分子有机物,为反渗透提供良好的进水水质.两种反渗透膜的产水化学需氧量(COD)均小于10 mg/L,电导率小于80/μS/cm,其对有机物和盐的去除率分别可达99%和93%以上,显示该产水能回用于大部分印染工序.BW30膜产水水质稍好于CPA2,但通量低于CPA2.     

新型Janus膜的制备及其在高盐含油废水膜蒸馏处理中的应用

采用表面蚀刻-电喷雾协同技术制备了具有微/纳凹槽表面结构的亲水/疏水型Janus膜,并系统考察了Janus膜的脱盐性能及耐润湿、抗污染功能。Janus膜具有水相超疏油的性能,对原油、正己烷、甲苯和汽油的水下油接触角分别为152.7°、150.1°、146.7°和151.1°。直接接触式膜蒸馏应用实验表明:在连续50 h的运行过程中,Janus膜对盐的截留率可达100%、膜通量稳定在10.18 kg·(m2·h)-1;对于不同浓度(0.1、0.2和0.3 mmol·L-1等)的十二烷基硫酸钠,Janus膜均表现出优异的抗润湿效果。在处理高盐含油废水过程中,Janus膜未发生膜润湿和膜污染的现象,膜通量及盐截留率也保持稳定;油滴力学探针测试结果定量阐释了Janus膜强健的抗油污能力。制备的新型Janus膜兼具耐润湿与抗污染特性,拓展了膜蒸馏技术在高浓度难降解废水处理领域的应用。     

SPEEK涂层纳滤膜处理草甘膦废水

以聚醚砜(PES)超滤膜为基膜,采用涂层法制备磺化聚醚醚酮(SPEEK)中空纤维复合纳滤膜,研究其对草甘膦的浓缩和去除。考察了该膜在浓缩草甘膦模拟废水中的操作条件,如跨膜压力、进料浓度、进料pH和离子强度等对通量和截留率的影响。结果表明,随跨膜压力的增加,草甘膦的截留率和水通量均增加,当跨膜压力由0.3 MPa增加到0.8 MPa时,水通量由34.0 L/(m2.h)增加至98.0 L/(m2·h),截留率高于98%;增加进料浓度和离子强度,截留率和通量均减小,当进料浓度由100 mg/L增至1 000 mg/L,水通量降低12.4%,截留率降低8.4%;而pH由3.0升至11.0时,截留率增加,但通量几乎不变。当把该膜材料用于浓缩含高浓度NaCl的草甘膦母液时,发现在0.5 MPa压力和pH=11.0下,复合纳滤膜对NaCl的截留率低于20%,对草甘膦的截留率可达90%。这说明该复合纳滤膜可以把草甘膦与NaCl有效分离开来,为草甘膦的回收利用提供了基础。     

PVDF/PMMA与PVDF/TPU共混膜抗污染性能研究及应用

观察新型五孔PVDF共混改性纤维膜SEM形貌特征,采用逐级通量法测定PVDF/PMMA和PVDF/TPU共混改性膜的临界通量,研究在次临界和超临界通量下A(PVDF/PMMA)与B(PVDF/TPU)2种管式膜组件的过滤和抗污染性能,并在次临界通量下处理地表水。结果表明,PVDF共混改性膜具有优良的微观结构,且膜B性能较好;膜A、B的临界通量分别为12 L/(m2.h)和10 L/(m2.h);膜组件B比膜组件A抗污染性能好。次临界通量下膜组件的运行比超临界通量下的稳定。与采用单独超滤处理某市地表水相比,2种膜组件采用混凝+超滤工艺的运行处理效果更好,且膜组件B比膜组件A处理效果佳。     

直接接触式膜蒸馏工艺处理高浓度氨氮模拟废水中操作条件的影响

采用直接接触式膜蒸馏处理高浓度氨氮模拟废水。实验对初始pH值、原料液流量和渗透液流量等3项操作条件进行了比较研究。结果表明,提高原料液的初始pH值可以大幅度地提高氨氮的去除效率、传质系数和分离效率,当初始pH达到12时,30 min内氨氮去除率可达到98%以上;提高料液流量可以得到同样的规律,当初始pH值为11,料液流量由400 L/h提高至800 L/h时,氨氮去除率由79.8%提高至88%;但渗透液流量的提高对处理效果的影响并不明显。     

The negative rejection of H+ in NF of carbonate solution and its influences on membrane performance

Nanofiltration (NF) experiments were conducted with simulated solution containing bicarbonate hardness and with three membranes: NF90, NF270 and NF-. The operating pressure was kept at 1.0 MPa, the water sample temperature was kept at 25 degrees C, the velocity on membrane surface was approximately 1 m s(-1) and the feeding pH values were 6.0, 6.5, 7.0, 7.5 and 8.0. Except for sampling, both the concentrate and the permeate were cycled to the feeding tank in order to keep the concentration constant. Experimental results demonstrated that the flux of NF90 membrane was slightly affected by the feeding pH, while the flux of NF270 and NF membranes was augmented when the feeding was acidified. The permeate pH of each membrane was always lower than the concentrate pH, indicating that the H(+) was negative rejected. This phenomenon was observed not only in the filtration of carbonate solution, but also in the filtration of the NaCl solution and the tap water. It is assumed that the small positive H(+) can easily permeate the NF membranes having negative charges. The more charges the membrane has, the more H(+) is negative rejected. High permeability of H(+) can speed decomposition of HCO(3)(-) into CO(3)(2-) and then accelerate CaCO(3) crystallization on membrane surface, which is unfavorable for membrane performances. In NF processes, it is better to considerate the membrane's selection and the feeding's pretreatment simultaneously, and it is beneficial for preventing scaling when selecting the membranes with less negative charges if only the water qualify can meet the demands.     

Removal of arsenic from contaminated groundwater by solar-driven membrane distillation

Experimental investigations were carried out on removal of arsenic from contaminated groundwater by employing a new flat-sheet cross flow membrane module fitted with a hydrophobic polyvinylidenefluoride (PVDF) microfiltration membrane. The new design of the solar-driven membrane module in direct contact membrane distillation (DCMD) configuration successfully produced almost 100 per cent arsenic-free water from contaminated groundwater in a largely fouling-free operation while permitting high fluxes under reduced temperature polarization. For a feed flow rate of 0.120 m³/h, the 0.13 μm PVDF membrane yielded a high flux of 74 kg/(m² h) at a feed water temperature of 40 °C and, 95 kg/m² h at a feed water temperature of 60 °C. The encouraging results show that the design could be effectively exploited in the vast arsenic-affected rural areas of South-East Asian countries blessed with abundant sunlight particularly during the critical dry season.     

气-水联合反冲洗膜污染防治技术研究

采用气水联合反冲洗技术,考察了气水比(Qg/Ql)、反冲洗周期及其对膜污染的防治效果。结果表明,气水联合反冲洗较单独气或水反冲洗效果好;在过滤周期20min,反冲洗时间1min,气水比1.5时,气水联合反冲洗能够恢复膜通量到膜清水通量的80%以上。此法可大幅度清除沉积在膜表面的泥饼层,恢复膜通量,维持膜过滤性能的稳定,是一种较为有效的膜污染防治技术。     

Fluoride removal from aqueous solution by direct contact membrane distillation: theoretical and experimental studies

Direct contact membrane distillation (DCMD) process using polyvinylidene fluoride (PVDF) membrane was used for fluoride removal from aqueous solution. This study has been carried out on heat and mass transfer analyses in DCMD. The dusty-gas model was used to analyze the mass transfer mechanism and to calculate the permeate flux. The heat transfer is analyzed based on energy balance, and the different layers are considered as a series of thermal resistances. Mass transfer analysis showed that the transition Knudsen-molecular diffusion is the dominant mechanism to describe the transport of water vapor through the pores of the PVDF membrane. The most significant operating parameter is the feed temperature. The permeate increases sensitively with feed temperature and velocity, and it shows insignificant change with feed salts concentration. Heat transfer analysis showed the conduction through the matrix of the membrane presents the major part of available energy. The increasing feed temperature leads to increase thermal efficiency (TE) and decrease temperature polarization coefficient (TPC). The experimental results are in good agreement with theoretical values. Therefore, it is suggested to work at high feed temperature, which will benefit both the thermal efficiency and permeate flux. The experimental results proved that DCMD process is able to produce almost fluoride-free water suitable for many beneficial uses.     

Comparative performance of flat sheet and spiral wound modules in the nanofiltration of reactive dye solution

Background and purpose

Besides the opportunities for reuse, stringent regulations and growing public awareness demand an enhanced quality of effluent from dye industries. Treatment of an aqueous solution of dye (reactive red 198) was carried out in a nanofiltration unit using both flat sheet and spiral wound modules to obtain a comparative performance evaluation in terms of permeate flux and quality.

Methods

Hydrophilized polyamide membrane with molecular weight cutoff of 150 was used for the experiments. Effects of trans-membrane pressure (TMP), feed concentration and addition of salt on permeate flux were investigated. Percent reduction of color, chemical oxygen demand (COD), total dissolved solid (TDS), and conductivity were determined to assess performance of the membrane.

Results

The maximum flux decline was 16.1% of its initial value at 490 kPa TMP with 50 ppm feed concentration in spiral wound module, whereas the same in flat sheet under same conditions was 7.2%. The effect of TMP showed a quasi-linear increase in flux with increasing pressure. Increased permeate concentration led to the reduction in observed retention of dye in the membrane. The average reduction in color, COD, and TDS were 96.88%, 97.38%, and 89.24%, respectively. The decline in permeate flux was more in case of spiral wound module compared to flat sheet. However, spiral wound module performed better in terms of color removal, COD reduction, and TDS removal.

Conclusion

Substantial removal of color was achieved in the nanofiltration experiments with a marked reduction in COD and TDS. The process allowed the production of permeate stream with great reutilization possibilities.     

酒石酸钾钠（PST）对纳滤处理重金属废水的强化效果

以酒石酸钾钠（PsT）为络合剂，分别选取cd、zn、As和Ph4种金属废水，探索络合纳滤工艺对金属离子去除率和膜通量的强化效果，测定纳滤膜表面接触角以表征膜通量变化规律，并研究了压力、金属浓度和溶液pH参数对络合纳滤过程的影响。结果表明，PsT对4种金属去除的强化效果存在相似规律，分别有一个最佳PsT添加浓度。随PsT浓度的增加，金属离子去除率先增大后减小，而膜通量一直增大。研究发现，纳滤膜表面接触角与膜通量呈稳定的反比例关系，与金属离子种类和PsT添加量无关。随着操作压力的增大，膜通量线性增加，去除率基本不变；金属离子浓度的增加对膜通量影响不大，金属去除率略有上升；pH在4～5之间变化时，As去除中膜通量和去除率均有所升高，而cd、zn和Ph3种溶液处理效果基本不受pH影响。