陶瓷膜构型对错流微滤酵母悬浮液性能的影响

采用3种构型的陶瓷微滤膜元件对酵母悬浮液进行错流过滤实验,考察陶瓷膜元件的构型对于其错流过滤性能的影响。结果表明:减小陶瓷膜元件的通道直径可以提高料液在膜表面的剪切力,有助于提高过滤稳定通量和临界压力,在3 m/s膜面流速、0.1 MPa跨膜压差条件下,单管、19通道、55通道的稳定通量分别为96、128、196 L/(m2.h);在3 m/s膜面流速条件下,3种陶瓷膜元件的临界压力分别约为0.15、0.2、0.2 MPa。另外,减小通道直径还可以减小滤饼层的比阻,有利于降低过滤阻力;与提高膜面流速来增大过滤通量的方法相比,减小陶瓷膜的通道直径具有能耗较小的优点。     

动态膜的形成机理及其水处理性能研究

以陶瓷管为载体,对高岭土动态膜的形成及其污水处理性能进行了详细的研究.实验中采用错流过滤方式涂膜,考查了跨膜压差、涂膜液浓度、错流速度及涂制时间等对动态膜形成的影响.通过对实验数据分析可知,动态膜形成初期10～13 min,膜的形成过程可用标准过滤模型描述,在此期间颗粒堵塞载体膜管孔道,致使渗透液通量急剧减小;之后,膜的形成过程符合滤饼过滤模型,这一阶段颗粒主要在载体膜管内壁面沉积,渗透液通量缓慢下降直至基本稳定.制备的动态膜可用于处理城市污水厂二级出水,动态膜对浊度去除率基本上为100%,对COD也有一定的去除作用.     

水头差对厌氧动态膜生物反应器动态膜形成影响

以无纺布为粗孔过滤基材构建厌氧动态膜生物反应器(AnDMBR),通过分析成膜时间、出水通量、过滤阻力、压缩性、胞外聚合物(EPS)含量和粒径分布(PSD),研究了水头差(2、5、8 cm)对动态膜(DM)形成和过滤阻力增加的影响。结果表明,随着水头差的增加,动态膜的形成时间缩短,过滤阻力提高;基于成膜时间和出水通量考虑,实验的适宜水头差为5 cm,出水浊度在45 min后降低至2 NTU以下,稳定通量为42 L/(m^2·h)。小颗粒和EPS的积累是造成过滤阻力增加的主要原因。     

弹状流对陶瓷膜超滤葡聚糖水溶液的影响

为降低膜污染和浓差极化需维持较高膜面流速,能耗较高。将气升式外循环引入膜过程,可有效降低浓差极化和能耗。实验考察了曝气量对渗透通量的影响,当曝气量为400 L·h^-1时,与相同液速条件下单相流错流过滤相比较,膜通量提升87%;进一步增大曝气量,膜通量增加趋势变缓。对气升式膜过滤过程的水力学特性进行了研究,在弹状流条件下,气液两相流可有效提高膜面剪切力,增强膜面传质。在较低流速下,曝气可有效降低膜污染阻力,提高膜通量。结合气液两相流理论和膜过滤阻力模型,分析了弹状流提升膜通量的机理。     

响应面法优化预涂动态膜处理城镇污水研究

为优化预涂动态膜工艺处理城镇污水处理厂二级出水膜污染的主要运行条件,首先通过单因素实验研究了硅藻土平均粒径、跨膜压差及涂膜液质量浓度对动态膜形成过程中膜通量的影响规律;其次采用Box-Behnken Design二阶模型优化设计多因素实验,通过回归模型建立及方差分析,得出优化条件及模型预测值;最后验证在该优化运行条件下模型的可靠性。结果表明,硅藻土平均粒径与跨膜压差之间的交互作用显著,各因素对膜平均通量的影响顺序依次为涂膜液质量浓度>硅藻土平均粒径>跨膜压差;根据模型方程得出的优化运行条件为硅藻土平均粒径23.75μm、跨膜压差0.08 MPa、涂膜液质量浓度0.39 g/L,膜平均通量达到36.85 L/（m2·h）,与预测值的误差为0.94%。因此,采用响应面法优化预涂动态膜工艺处理城镇污水处理厂二级出水是切实可行的。     

有机粘土辅助的微滤膜处理高浓度含油废水

将有机粘土与陶瓷微滤膜结合处理高浓度乳化油废水.结果表明,有机粘土作为膜过程的助滤剂,能减轻膜污染,在温度30℃、膜面流速5 m·s-1,跨膜压差0.10 MPa的条件下,膜通量为240 L·m-2·h-1,比直接微滤增大了60%.有效改善了出水水质,提高了除油率,渗透液油含量<10mg·L-1,满足排放要求.     

膜结构和DOM相对分子质量分布对城市二级出水超滤过程的影响

考察了膜孔径、膜孔隙率以及水中溶解性有机物( DOM)相对分子质量分布对二级出水超滤膜过程的影响.结果表明,膜孔孔径对膜污染特性有一定影响,孔径越大,则膜纯水通量越大,单位时间在膜表面和膜孔内形成污染的有机物也越多,膜污染也越严重,导致通量衰减幅度较大;对于膜孔径相近的膜来说,孔隙率大意味着水通量大,过滤过程对膜产生的...     

动态膜微滤含污泥水及膜污染特征

以陶瓷管为载体,对高岭土动态膜微滤含污泥水性能及膜污染特征进行了较为详细的研究. 考察了错流速度、跨膜压差及污泥浓度对滤出液通量及水质的影响,结果表明,提高错流速度和增大跨膜压差均使滤液通量增加,但错流速度超过2.0 m/s易引起动态膜脱落;污泥浓度增加,则滤液通量明显降低;过滤进行约30 min后,出水浊度基本为0;60 min后,化学需氧量的去除率基本保持在50%以上. 动态膜层及其截留的污染物阻力占总过滤阻力的90%以上. 对膜面特征污染物成分分析表明,P, Ca为膜面主要污染元素,分别占23.77%和20.60%(w);对陶瓷膜孔中不可逆污染物的化学洗脱液分析表明,膜中总有机碳近4370 mg/m2,Ca, Mg是主要无机污染元素,分别约1240和886 mg/m2. 先后用0.2 mol/L的NaOH水溶液和0.1 mol/L的HCl水溶液清洗膜中不可逆污染物,可使基膜通量恢复至新膜的85%.     

亲水化改性PVDF超滤膜的抗污染特性研究

以不同通量的自制亲水化纳米SiO2改性PVDF超滤膜(PS)和聚乙烯醇改性PVDF超滤膜(PA),对城市污水二级出水(EfOM)和牛血清蛋白(BSA)水溶液进行了过滤试验,通过对比未添加改性剂的PVDF超滤膜,考察通量衰减率、膜污染阻力构成、通量恢复率等指标,分析水质与膜材料间的相互关系对超滤膜抗污染能力的影响.结果表明,在BSA料液中,3种通量下,低通量的膜抗污染能力好于高通量膜.20 min内PA膜表现出最低的膜通量衰减,而P膜在过滤初期通量就急剧下降.在EfOM料液中,各通量下,P膜通量衰减严重且产生了不可逆的堵孔阻力,亲水化改性后膜通量衰减率降低,稳态通量高,膜污染阻力主要来自于浓差极化和滤饼层阻力,其中PS膜通量下降率最低,而PA膜清洗后通量易恢复.     

正渗透去除微塑料效能及其响应面法优化

试验选取PET塑料颗粒作为去除目标物，NaCl溶液为汲取液，分别考察正渗透膜通量变化及对PET颗粒的去除影响因素分析。结果表明：增大汲取液浓度、运行温度、膜面流速和PET粒径均能显著提高膜通量，且其总膜比通量也较大，但与膜通量衰减存在一定交互作用；试验周期内，在汲取液中未检测到PET颗粒，去除率可达100%。去除率分别由膜截留率及装置系统吸附率贡献，两者占比在各去除影响因素分析中有所变化，其中汲取液浓度、膜面流速和粒径对吸附率去除贡献比影响较大，而温度对其影响不显著，且相关性不强；最后用响应面法优化汲取液浓度、膜面流速和温度对总膜比通量的影响。回归模型分析表明三种影响因素影响程度为：1）在低膜面流速的条件下汲取液浓度>膜面流速>温度；2）在高膜面流速的条件下汲取液浓度>温度>膜面流速。优化方案模型的模拟预测值与实验测试值基本吻合。     

A high flux graphene oxide nanoparticles embedded in PAN nanofiber microfiltration membrane for water treatment applications with improved anti-fouling performance

A high flux and anti-fouling graphene oxide (GO) nanoparticles embedded in polyacrylonitrile (PAN) nanofiber microfiltration membranes (PANGMs) were fabricated through the facile electrospinning method and were characterized by water treatment applications. The synthesized GO nanoparticles and GO nanoparticles embedded in PAN nanofiber membranes were characterized by FESEM, FTIR, and EDS. SEM images showed that the PANGMs possessed randomly overlaid fibers with a network-like highly porous structure similar to the pristine PAN nanofiber membrane, while agglomeration of GO nanoparticles was observed at high GO concentration. The introduction of GO nanoparticles into the PAN polymeric matrix significantly increased the permeation flux of the resulting membrane in both dead-end and cross-flow filtration systems. A high flux recovery ratio of 96.6% and a low irreversible fouling ratio of 3.4% were obtained at 2% (wt.) GO nanoparticles. More importantly, a high flux recovery ratio of GO nanoparticles embedded in PAN nanofiber membrane was retained after 20 repeated cycles of activated sludge suspension filtration. Therefore, it can speculate that the incorporation of GO nanoparticles into the PAN nanofibers could efficiently improve the anti-fouling ability of membranes which had opened up an alternative for the preparation of high flux and anti-fouling microfiltration membranes in practical water treatment applications such as membrane bioreactors.

     

Process intensification with a hybrid system: A tubular packed bed bioreactor with immobilized activated sludge culture coupled with membrane filtration

Performance of a hybrid system consisting of a tubular bioreactor and a membrane filter was studied for removing carbohydrate and protein. Microporous polyurethane (sponge) was used as the packing medium for immobilization activated sludge culture. The bioreactor was operated in series with a cross flow ultrafiltration system to study the effect of influent flow rate and chemical oxygen demand (COD) concentration on the overall system performance. The removal efficiency in the bioreactor decreased linearly with increase in loading. The decline of removal efficiency at higher loadings was more significant for protein than carbohydrate. Coupling the bioreactor with a membrane separation process increased the overall removal rates and provided a consistent effluent quality. The flux through ultrafiltration membrane did not change significantly even when the bioreactor effluent had high levels of protein. Morphological examination of the packing medium both visually and by SEM showed significant accumulation of organisms on the surface which indicates that biofilm thickness was controlled by diffusion limitations. Advantages of the hybrid system include small footprint, economical packing medium, and space savings by coupling the bioreactor with a membrane filtration process.     

膜-序批式生物反应器膜过滤特性研究

采用中空纤维膜-序批式生物反应器(HF-MSBR)和双功能膜-序批式生物反应器(DF-MSBR)处理实际洗浴污水,在不排泥条件下考察了系统对污染物的去除效果及膜的过滤特性。结果表明,两系统污染物去除效果良好,COD、浊度等平均去除率分别达到95.2%和88.4%、99.6%和96.9%;DF-MSBR系统中聚乙烯膜组件对COD的强化去除作用不明显,但对浊度的强化去除作用显著,通过膜曝气可以使膜通量具有一定程度的恢复,但膜过滤性能仍不稳定,膜污染发展速度较快,过滤周期较短;HF-MSBR系统出水COD优于DF-MSBR,出水浊度小于1NTU,在运行期间膜过滤阻力上升缓慢,平均上升速率远远小于DF-MSBR系统。     

Comparison of the filtration characteristics between biological powdered activated carbon sludge and activated sludge in submerged membrane bioreactors

The filtration performances of submerged membrane bioreactors (SMBR) with and without the addition of powdered activated carbon (PAC) were investigated respectively under the same feed and operation conditions. A series of experiments were conducted to analyze near-critical flux, effect of air-scouring rate and time of stable filtration operation of both systems. The experimental results demonstrated that pronounced flux enhancement was achieved by adding 1.2 g/L PAC. The near-critical flux for the biological powdered activated carbon (BPAC) system was about 32% higher than that for the activated sludge (AS) system. Increasing the air-scouring rate led to a more significant flux improvement for the BPAC system compared to the AS system. Long-term operation indicated that, at constant flux, the TMP increasing rate of the BPAC system could be lagged and thus cause the extension of operating intervals about 1.8 times compared to the AS system. Quantitative calculations showed the total hydraulic resistance of the BPAC system was about 44% lower than that of the AS system, and this decrease was mainly caused by the reduction in cake resistance. Analyses were then made from various aspects such as floc size distribution and apparent viscosity of the mixed liquor to elucidate the major factors giving rise to different filtration characteristics.     

The Optimization of Ozonation and Biological Activated Carbon (BAC) in a Water Reclamation Context

A pilot plant study showed that an ozone dosage of about 4 mg/l before filtration and BAC led to the most cost-effective COD removal in the reclamation of water from activated sludge effluent. The combination in the reclamation of water from activated sludge effluent. The combination of ozonation, filtration and BAC could maintain a least COD removal fraction of 30 per cent for more than three times as long an inter–reactivation period as for filtration and BAC without ozonation. Filtration has not been found to contribute significantly to the COD removal by the above combination of process units.     

Membrane filtration characteristics in membrane-coupled activated sludge system - the effect of physiological states of activated sludge on membrane fouling

The effect of sludge physiology on membrane fouling was investigated in a membrane-coupled activated sludge (MCAS) system. A series of ultrafiltrations were performed to assess the flux behaviors according to foaming potential, solids retention time (SRT), growth phase and nutrient condition of the activated sludge. The foaming sludge showed greater flux decline than the non-foaming sludge. The extraordinary increase, that is, more than 100 times in membrane fouling for the foaming sludge, was attributed to the hydrophobic and waxy nature of the foaming sludge surface, which was confirmed by a comparison with relative hydrophobicity. Membrane fouling tendency was increased as SRT decreased. A greater flux decline was observed at the endogenous phase than at the log growth phase. The activated sludge acclimated to the nitrogen deficient substrates produced less extracellular polymeric substances (EPS) and exhibited higher flux than the control activated sludge. The quantitative measurements of EPS content in order to estimate the extent of membrane fouling in various activated sludges showed that, in any physiological states of activated sludge, the higher the content of EPS the activated sludge had, the greater the membrane fouling proceeded. The EPS content of activated sludge is suggested as a probable index for the membrane fouling in a MCAS system.     

膜生物反应器中膜污染机理的研究

在采用膜生物反应器（MBR）处理染料废水的过程中,通过对活性污泥进行终端过滤来反映膜污染机理,着重考察了膜过滤的形式、膜通量变化和膜污染的形成。污泥的终端过滤过程严格符合沉积过滤定律;膜通量随过滤时间呈指数衰减趋势,并在几分钟内就达到相对稳定值;扫描电镜照片也证实了膜污染主要是膜面沉积层引起的。     

受污染原水处理的聚四氟乙烯中空膜组合工艺

该文以排洪期东江水为原水,开展了聚四氟乙烯（PTFE）中空纤维膜组合工艺处理受污染原水的小试和中试研究。工艺将臭氧、混凝与膜过滤集成,后置生物活性炭过滤。试验的PTFE膜孔径为0.12μm,外径×内径为2.3 mm×1 mm。小试试验测得临界膜通量为60 L/m^2·h,臭氧能够促进组合工艺对有机物的去除,并能提高氨氮的去除。中试试验规模为120 t/d,膜通量为41.67 L/m^2·h。结果表明,投加臭氧时组合工艺对氨氮的处理负荷能提高至3.19~4.31 mg/L,COD去除率为70%~94%,UV254去除率达到73%~87%,工艺出水浊度〈0.2 NTU,大于2μm颗粒数〈50 CNT/mL。工艺出水中THMs、HAAs、甲醛、溴酸盐均符合新的饮用水卫生标准;膜出水未检出细菌总数和总大肠菌群数。投加臭氧（O3/TOC=0.6~0.8）可显著减轻膜污染,达到同样的污染程度所需的运行时间较未投加臭氧时延长1倍;投加7~9 mg/L臭氧可逐渐消除膜污染,达到原位修复膜污染,减少化学清洗频次的目的。