膜表面形貌对厌氧膜生物反应器膜污染影响的试验研究

在厌氧膜生物反应器处理高浓度食品废水的试验中,借助原子力显微镜分析了四种表面形貌不同的聚醚砜超滤膜的通量衰减规律.结果表明,超滤膜表面形貌愈粗糙,膜通量的衰减速率愈快,且化学清洗后恢复愈困难.     

氯化铁絮凝法减轻膜污染

采用氯化铁絮凝法去除膜生物反应器混合液中难降解的大分子有机物，确定Fe^3 的最佳投加量为60mg／L，该工艺可显著降低混合液中CODCr，减轻膜污染，并且对膜生物反应器中的生物相活性没有影响。     

膜生物反应器处理甲苯废气的挂膜实验

采用假单胞菌在硅橡胶复合膜生物反应器上进行甲苯废气降解的挂膜启动实验,研究膜生物反应器挂膜启动特性,对挂膜启动过程中循环液吸光度、压力损失、甲苯降解效率和生物膜干重的变化进行考察,并观察挂膜稳定后的生物膜形态.结果表明:挂膜过程主要由生物膜成膜期(0~5 d)、生长期(6~10 d)、稳定期(11~14 d)3个阶段组成.循环液吸光度、反应器内液相压力损失、甲苯降解效率和生物膜干重等参数在成膜期都快速增加;进入膜生长期,循环液吸光度略微下降,而生物膜干重、压力损失和甲苯降解效率都继续增大;在稳定期各参数均趋于相对稳定,稳定后循环液吸光度维持在0.75左右,液相压力损失达到了180 Pa,甲苯降解效率维持在78%以上,生物膜干重为2.25 mg/cm2.试验表明,对循环液吸光度、液相压力损失、甲苯降解效率和生物膜干重等参数的综合分析,可作为膜生物反应器挂膜启动进程的判据.图9参15     

特定静电场长期作用下作物叶绿体膜组分及膜流动性的变化

研究了0.3kV/cm静电场长期作用下,大豆、黄瓜与油青菜心叶片光合细胞中叶绿体膜脂肪酸组分和膜流动性的影响.结果表明,静电场处理使叶绿体膜不饱和脂肪酸相对含量增加,饱和脂肪酸相对含量减少,膜脂肪酸的不饱和度指数和膜流动性提高.进一步研究发现,静电场处理使叶片细胞内丙二醛(MDA)含量降低,超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性提高,表明静电场的作用提高了作物光合细胞抗氧化保护酶系统的功能,使光合细胞中叶绿体膜流动性增加.图3表1参16     

膜生物反应器处理高氨氮废水

试验采用MBR处理高氨氮废水,重点分析了氨氮、有机物的去除以及膜比通量变化等。结果表明,工艺运行稳定,出水氨氮平均浓度低于3mg/L,MBR能够抵抗有机物冲击负荷,氨氮容积负荷可以达到1.11kgNH3-N/(m3·d)。在整个运行期间膜比通量下降比较缓慢,分析认为是高曝气量、低碳氮比以及自养菌的优势生长起了主要作用。     

在线反冲洗控制MBR膜污染的试验

试验采用在线空气反冲洗和在线清水反冲洗控制膜生物反应器(MBR)膜污染。试验结果表明,通过在线空气反冲洗,膜通量最大可恢复至20.5L/(m2·h),恢复率为95.3%,反冲洗周期为5d,且30d后膜通量仍大于12L/(m2·h);采用在线清水反冲洗后,膜通量最大可恢复至20.9L/(m2·h),恢复率为97.7%,第34天进行第3次在线清水反冲洗后膜通量仍可恢复至19.8L/(m2·h)。     

新型抗氧化膜材料PSAA的研制

对聚亚磺酰氨基酰胺(PSAA)作为新型抗氧化反渗透膜材料的可能性,以及聚合条件和成膜条件对膜性能的影响作了初步研究。     

SMBR不同特性膜处理城市内河道水对比试验研究

用一体浸没式膜生物反应器(SMBR)不同特性膜处理上海市城市内河道水,结果表明,SMBR对氨氮含量较高的富营养化河水,氨氮的去除率在90%以上,但对COD的平均去除率仅为50%.比较两种膜的运行性能,亲水性膜在运行通量和通量恢复能力上,均比疏水性膜优越.两种膜的出水水质几乎没有差异.     

磷酸铁膜对黄铁矿氧化抑制作用

本文用动力学、表面分析方法研究在黄铁矿表面磷酸铁膜形成的可能性以及磷酸铁膜抑制黄铁矿的氧化作用,黄铁矿经０．３ｍｏｌ．ｌ＾－１Ｈ２Ｏ２＋０．０１ｍｏｌ．ｌ＾－１ＮａＨ２ＰＯ４＋０．０５ｍｏｌ．ｌ＾－１ＮａＡｃ（ｐｈ５．０）淋洗后,在其表面可形成一层磷酸铁膜,该能显著抑制黄铁矿的进一步氧化,结果还表明,在Ｈ２Ｏ２作用下,黄铁矿氧化有自催化氧化的特征,其氧化产物Ｆｅ＾３＋能加快黄铁矿的氧化速率。     

Relationship between sludge settleability and membrane fouling in a membrane bioreactor

The evolution of activated sludge settleability and its relationship to membrane fouling in a submerged membrane bioreactor were studied at a lab-scale equipment fed with synthetic wastewater. It was found that sludge volume index (SVI) gradually increased and the sludge settleability was reduced, which was caused by the propagation of filamentous bacteria. With increasing SVI, the average increasing rate of trans-membrane pressure increased, the stable filtration period was shortened, and the two stages (smooth stage and accelerating stage) of the trans-membrane pressure were more obvious. At the same time, the increasing rate of trans-membrane pressure at the smooth stage decreased and the rate at the accelerating stage increased with SVI, respectively. The observation by using scanning electronic microscopes showed the cake layer with loose structure and large thickness formed on the membrane surface due to the appearance of filamentous bacteria and high SVI in sludge. Influence of the sludge settleability on the trans-membrane pressure was related to the structure and thickness of the cake layer on the membrane.     

Biofuel types and membrane separation

Environmental Chemistry Letters - Global warming induced by greenhouse gases is major issue worldwide. There is therefore a need to develop renewable sources of energy, such as biofuels. Here, we...     

Energy reduction of a submerged membrane bioreactor using a polytetrafluoroethylene (PTFE) hollow-fiber membrane

The fiber length and packing density of the PTFE membrane element were increased. The MBR was stably operated under an SAD^m of 0.13 m³·m^-2·hr^-1. Specific energy consumption was estimated to be less than 0.4 kWh·m^-3. In this study, we modified a polytetrafluoroethylene (PTFE) hollow-fiber membrane element used for submerged membrane bioreactors (MBRs) to reduce the energy consumption during MBR processes. The high mechanical strength of the PTFE membrane made it possible to increase the effective length of the membrane fiber from 2 to 3 m. In addition, the packing density was increased by 20% by optimizing the membrane element configuration. These modifications improve the efficiency of membrane cleaning associated with aeration. The target of specific energy consumption was less than 0.4 kWh·m^-3 in this study. The continuous operation of a pilot MBR treating real municipal wastewater revealed that the MBR utilizing the modified membrane element can be stably operated under a specific air demand per membrane surface area (SAD_m) of 0.13 m³·m^-2·hr^-1 when the daily-averaged membrane fluxes for the constant flow rate and flow rate fluctuating modes of operation were set to 0.6 and 0.5 m³·m^-2·d^-1, respectively. The specific energy consumption under these operating conditions was estimated to be less than 0.37 kWh·m^-3. These results strongly suggest that operating an MBR equipped with the modified membrane element with a specific energy consumption of less than 0.4 kWh·m^-3 is highly possible.     

Aggravation of membrane fouling and methane leakage by a three-phase separator in an external anaerobic ceramic membrane bioreactor

The existence of three-phase separator did not affect COD removal in the EAnCMBR. The existence of three-phase separator aggravated methane leakage of EAnCMBR. The existence of three-phase separator aggravated membrane fouling rate of EAnCMBR. Start-up of EAnCMBR equipped three-phase separator was slightly delayed. The three-phase separator is a critical component of high-rate anaerobic bioreactors due to its significant contribution in separation of biomass, wastewater, and biogas. However, its role in an anaerobic membrane bioreactor is still not clear. In this study, the distinction between an external anaerobic ceramic membrane bioreactor (EAnCMBR) unequipped (R1) and equipped (R2) with a three-phase separator was investigated in terms of treatment performance, membrane fouling, extracellular polymers of sludge, and microbial community structure. The results indicate that the COD removal efficiencies of R1 and R2 were 98.2%±0.4% and 98.1%±0.4%, respectively, but the start-up period of R2 was slightly delayed. Moreover, the membrane fouling rate of R2 (0.4 kPa/d) was higher than that of R1 (0.2 kPa/d). Interestingly, the methane leakage from R2 (0.1 L/d) was 20 times higher than that from R1 (0.005 L/d). The results demonstrate that the three-phase separator aggravated the membrane fouling rate and methane leakage in the EAnCMBR. Therefore, this study provides a novel perspective on the effects of a three-phase separator in an EAnCMBR.     

A submerged membrane filter apparatus for microbiological sampling

The sampler is operated by hydrostatic pressure and consists of a stainless steel cylinder to which is attached a membrane filter holder. A glass inlet tube is broken by a messenger and a predetermined volume of water is filtered. Valves protect the membrane from flow-back and release the pressure as the sampler returns to the surface. The sampler works satisfactorily at 15 m and is strong enough to be used down to 6000 m. The filling rate is controlled by a jet behind the filter holder.     

Carbon nanotube- and graphene-based advanced membrane materials for desalination

The development of membrane-based desalination and water purification technologies offers new alternatives to meet the global freshwater demand. Rapid advancement in carbon nanotube-based and graphene-based nanomaterials has drawn the attention of scientific investigators on various desalination technologies. These nanomaterials indeed offer advantageous structure, size, shape, porosity and mass transport behavior for membrane separation process. This article  reviews theoretical and experimental investigations of carbon nanotube- and graphene-based composite materials for desalination. Special attention is given to the simulation of molecular transport through these materials. Further, recent advances in the application of functionalization of carbon nanotube- and graphene-based materials for salt rejection and hydraulic permeation properties are discussed.     

Bisphenol A removal from synthetic municipal wastewater by a bioreactor coupled with either a forward osmotic membrane or a microfiltration membrane unit

Forward osmotic membrane bioreactor is an emerging technology that combines the advantages of forward osmosis and conventional membrane bioreactor. In this paper, bisphenol A removal by using a forward osmotic membrane bioreactor and a conventional membrane bioreactor that shared one biologic reactor was studied. The total removal rate of bisphenol A by the conventional membrane bioreactor and forward osmotic membrane bioreactor was as high as 93.9% and 98%, respectively. Biodegradation plays a dominant role in the total removal of bisphenol A in both processes. In comparison of membrane rejection, the forward osmosis membrane can remove approximately 70% bisphenol A from the feed, much higher than that of the microfiltration membrane (below 10%). Forward osmosis membrane bioreactor should be operated with its BPA loading rate under 0.08 mg·g^-1·d^-1 to guarantee the effluent bisphenol A concentration less than10 μg·L^-1.     

Ceramic membrane fouling mechanisms and control for water treatment

● The fouling is summarized based on ceramic membrane performance and pollutants. ● The current research methods and theoretical models are summarized. ● The membrane fouling control methods and collaborative technology are reviewed. Membrane separation, as an important drinking water treatment technology, has wide applications. The remarkable advantages of ceramic membranes, such as chemical stability, thermal stability, and high mechanical strength, endow them with broader prospects for development. Despite the importance and advantages of membrane separation in water treatment, the technique has a limitation: membrane fouling, which greatly lowers its effectiveness. This is caused by organics, inorganic substances, and microorganisms clogging the pore and polluting the membrane surface. The increase in membrane pollution greatly lowers purification effectiveness. Controlling membrane fouling is critical in ensuring the efficient and stable operation of ceramic membranes for water treatment. This review analyzes four mechanisms of ceramic membrane fouling, namely complete blocking, standard blocking, intermediate blocking, and cake filtration blocking. It evaluates the mechanisms underlying ceramic membrane fouling and summarizes the progress in approaches aimed at controlling it. These include ceramic membrane pretreatment, ceramic membrane surface modification, membrane cleaning, magnetization, ultrasonics, and nanobubbles. This review highlights the importance of optimizing ceramic membrane preparation through further research on membrane fouling and pre-membrane pretreatment mechanisms. In addition, combining process regulations with ceramic membranes as the core is an important research direction for ceramic membrane-based water treatment.     

Performance of bioferric-submerged membrane bioreactor for dyeing wastewater treatment

Adding iron salt or iron hydroxide to sludgemixed liquor in an aeration tank of a conventional activated sludge processes (bioferric process) can simultaneously improve the sludge’s filterability and enhance the system’s treatment capacity. In view of this, Fe(OH)₃ was added to a submerged membrane bioreactor (SMBR) to enhance the removal efficiency and to mitigate membrane fouling. Bioferric process and SMBR were combined to create a novel process called Bioferric-SMBR. A side-by-side comparison study of Bioferric-SMBR and common SMBR dealing with dyeing wastewater was carried out. Bioferric-SMBR showed potential superiority, which could enhance removal efficiency, reduce membrane fouling and improve sludge characteristic. When volumetric loading rate was 25% higher than that of common SMBR, the removal efficiencies of Bioferric-SMBR on COD, dye, and NH₄ ⁺-N were 1.0%, 9.5%, and 5.2% higher than that of common SMBR, respectively. The trans-membrane pressure of Bioferric-SMBR was only 36% of that in common SMBR while its membrane flux was 25% higher than that of common SMBR. The stable running period in Bioferric-SMBR was 2.5 times of that in common SMBR when there was no surplus sludge discharged. The mixed liquor suspended solids concentration of Bioferric-SMBR was higher than that of common SMBR with more diversified kinds of microorganisms such as protozoans and metazoans. The mean particle diameter and specific oxygen uptake rate of Bioferric-SMBR were 3.10 and 1.23 times the common SMBR, respectively.