Mass Transfer, Gas Holdup, and Kinetic Models of Batch and Continuous Fermentation in a Novel Rectangular Dynamic Membrane Airlift Bioreactor

Compared with conventional cylinder airlift bioreactors(CCABs)that produce coarse bubbles,a novel rectangular dynamic membrane airlift bioreactor(RDMAB)developed in our lab produces fine bubbles to enhance the volumetric oxygen mass transfer coefficient(k_(L)a)and gas holdup,as well as improve the bioprocess in a bioreactor.In this study,we compared mass transfer,gas holdup,and batch and con-tinuous fermentation for RNA production in CCAB and RDMAB.In addition,unstructured kinetic models for microbial growth,substrate utilization,and RNA formation were established.In batch fermentation,biomass,RNA yield,and substrate utilization in the RDMAB were higher than those in the CCAB,which indicates that dynamic membrane aeration produced a high k_(L)a by fine bubbles;a higher k_(L)a is more bene-ficial to aerobic fermentation.The starting time of continuous fermentation in the RDMAB was 20 h ear-lier than that in the CCAB,which greatly improved the biological process.During continuous fermentation,maintaining the same dissolved oxygen level and a constant dilution rate,the biomass accumulation and RNA concentration in the RDMAB were 9.71% and 11.15% higher than those in the CCAB,respectively.Finally,the dilution rate of RDMAB was 16.7% higher than that of CCAB during con-tinuous fermentation while maintaining the same air aeration.In summary,RDMAB is more suitable for continuous fermentation processes.Developing new aeration and structural geometry in airlift bioreac-tors to enhance k_(L)a and gas holdup is becoming increasingly important to improve bioprocesses in a bioreactor.

不同载体对DMBR处理模拟生活污水的影响研究

为探究不同载体对DMBR处理模拟生活污水的影响,以150目尼龙网、200目尼龙网、活性炭海绵作为动态膜载体,测定了DMBR运行过程中DOC、NH3-N、PO43-等污染物质的变化情况;通过出水浊度和TMP等参数判断动态膜层形成时间;提取了动态膜层中EPS并进行定量分析。结果表明,使用尼龙网和活性炭海绵作载体均可以提高出水效果,DOC和NH3-N平均去除率均大于97%,PO43-去除率大于90%,出水平均浊度降低至1.87 NTU以下;浊度等数据表明尼龙网作载体时动态膜可以在24 h内形成,活性炭海绵作载体时动态膜形成时间小于90 min,表现出更好的截留效果;EPS测定结果表明PS为形成膜污染的主要物质。

Dynamic membrane bioreactor performance enhancement by powdered activated carbon addition:Evaluation of sludge morphological,aggregative and microbial properties

The effects of powdered activated carbon(PAC) addition on sludge morphological, aggregative and microbial properties in a dynamic membrane bioreactor(DMBR) were investigated to explore the enhancement mechanism of pollutants removal and filtration performance. Sludge properties were analyzed through various analytical measurements. The results showed that the improved sludge aggregation ability and the evolution of microbial communities affected sludge morphology in PAC-DMBR, as evidenced by the formation of large, regularly shaped and strengthened sludge flocs. The modifications of sludge characteristics promoted the formation process and filtration flux of the dynamic membrane(DM) layer. Additionally, PAC addition did not exert very significant influence on the propagation of eukaryotes(protists and metazoans)and microbial metabolic activity. High-throughput pyrosequencing results indicated that adding PAC improved the bacterial diversity in activated sludge, as PAC addition brought about additional microenvironment in the form of biological PAC(BPAC), which promoted the enrichment of Acinetobacter(13.9%), Comamonas(2.9%), Flavobacterium(0.31%) and Pseudomonas(0.62%), all contributing to sludge flocs formation and several(such as Acinetobacter) capable of biodegrading relatively complex organics. Therefore, PAC addition could favorably modify sludge properties from various aspects and thus enhance the DMBR performance.

Characterization of dissolved organic matter in a dynamic membrane bioreactor for wastewater treatment

This paper systematically examined the characteristics of dissolved organic matter(DOM) in a dynamic membrane bioreactor(DMBR) for municipal wastewater with a laboratory-scale continuous-flow device.Experimental results showed that the system performed excellent pollutants' removal efficiencies.The increase of trans-membrane pressure(TMP) for the dynamic membrane(DM) could be divided into three stages,i.e.,zero increase stage,slow increase stage and abrupt rise stage.The maximal fouling rate of the DM reached to 4.34 kPa/h in abrupt rise stage.It was observed that the polysaccharides(PS) concentration of DOM samples gradually increased from the anaerobic zone to the aerobic zone in sequence,but the proteins(PN) concentration performed an opposite trend.The DM could retain a small part of the large molecular substances(>10 kDa) in the aerobic zone.Two particular fluorescence peaks appeared in the anaerobic zone and in the anoxic zone were also found in the effluent,which illustrated the dynamic cake layer closed to the stainless steel mesh might induce an anaerobic/anoxic micro environment.Based on the three-dimensional excitation-emission matrix(EEM) fluorescence spectroscopy analysis,aromatic proteins,aromatic proteinlike substance,fulvic acid-like substances and soluble microbial by-product-like materials could be biodegraded effectively in the DMBR,and the DM could partly remove the humic acid-like substances and soluble microbial by-product-like materials.

Thermodynamic prediction and experimental investigation of short-term dynamic membrane formation in dynamic membrane bioreactors:Effects of sludge properties

In dynamic membrane bioreactors(DMBRs), a dynamic membrane(DM) forms on a support material to act as the separation membrane for solids and liquids. In this study, batch filtration tests were carried out in a DMBR using nylon mesh(25 μm) as support material to filtrate sludge suspensions of variable properties from three different sources to evaluate the effects on the short-term DM formation process(within 240 min). Furthermore, the extended Derjaguin–Landau–Verwey–Overbeek(XDLVO) theory was applied to analyze the sludge adhesion and cohesion behaviors on the mesh surface to predict quantitative parameters of the short-term DM formation process(including initial formation and maturation stage). The filtration results showed that the order of the initial DM formation time(permeate turbidity <1 NTU as an indicator) was as follows: sludge with poor settleability and dewaterability < normal sludge <sludge with poor flocculability. Moreover, normal sludge(regarding settleability, dewaterability,flocculability, and extracellular polymeric substance) showed a more acceptable DM formation performance(short DM formation time, low permeate turbidity, and high permeate flux) than sludge with poor settleability, dewaterability and flocculability. The influence of sludge properties on the initial DM formation time corroborates the prediction of sludge adhesion behaviors by XDLVO theory. Additionally, the XDLVO calculation results showed that acid–based interaction, energy barrier, and secondary energy minimum were important determinants of the sludge adhesion and cohesion behaviors. Therefore, short-term DM formation process may be enhanced to achieve stable long-term DMBR operation through positive modification of the sludge properties.

Development of combined coagulation-hydrolysis acidification-dynamic membrane bioreactor system for treatment of oilfield polymer-flooding wastewater

A combined system composed of coagulation, hydrolysis acidification and dynamic membrane bioreactor (DMBR) was developed for treating the wastewater produced from polymer flooding. Performance and mechanism of the combined system as well as its respective units were also evaluated. The combined system has shown high-capacity to remove all contaminants in the influent. In this work, the coagulant, polyacrylamide-dimethyldiallyammonium chloride-butylacrylate terpolymer (P(DMDAAC-AM-BA)), integrated with demulsifier (SD-46) could remove 91.8% of crude oil and 70.8% of COD. Hydrolysis acidification unit improved the biodegradability of the influent and the experimental results showed that the highest acidification efficiency in hydrolysis acidification reactor was 20.36% under hydraulic retention time of 7h. The DMBR proceeded efficiently without serious blockage process of membrane fouling, and the concentration of ammonia nitrogen (NH3-N), oil, chemical oxygen demand and biological oxygen demand in effluent were determined to be 3.4±2.1, 0.3±0.6, 89.7±21.3 and 13±4.7 mg/L.

动态膜生物反应器(DMBR)研究进展

动态膜生物反应器是一种将动态膜过滤技术和生物法污水处理工艺相结合的新型污水处理工艺.介绍了DMBR机理及工艺处理效果,并从膜基材选择、操作参数控制等方面评述了国内外学者在该领域的研究成果,指出DMBR存在的问题及发展方向.

DMBR-IVCW耦合工艺处理生活污水的研究

进行了1种新型的动态膜生物反应器(DMBR)和复合垂直流人工湿地(IVCW)的耦合工艺处理生活污水的研究。结果表明,3个阶段耦合系统对COD的去除率分别为90.34%、93.35%和93.68%,对TN去除率分别为93.84%、89.77%和85.13%,对TP去除率分别为85.36%、87.99%和90.39%,对浊度去除率分别为86.74%、97.30%和98.60%。各项出水指标均达到GB18918-2002一级A排放要求和CJ25.1-89要求,可作中水回用。DMBR单元可以有效去除COD以及浊度,同时在抗击污染负荷和水力负荷方面也有稳定表现;而IVCW作为DMBR的生物强化单元,主要是去除N、P等营养物质。

盐度对DMBR处理养殖废水脱氮效能的影响

采用动态膜生物反应器(DMBR)处理养殖废水,考察盐度为0～3 000mg·L-1时动态膜生物反应器的脱氮效能.结果表明:DMBR对养殖废水的CODMn和NH3-N的去除效果保持稳定,分别为93%,87%左右;在盐度提高到1 000mg·L-1后,DMBR内反硝化速率明显提高,对NO3-N的去除率提高到97%,总氮去除率也达到94%.在盐度为0～3 000mg·L-1下,DMBR处理养殖废水的出水水质达到SC/T 9101-2007《淡水池塘养殖水排放要求》中的一级排放标准.

重力出流式DMBR处理生活污水的研究

采用重力出流式动态膜生物反应器(DMBR)处理生活污水,重点探讨了有机负荷、DO、pH等因素对污染物去除效果的影响及延缓膜污染的措施。结果表明:该系统对SS的去除效果很好,出水SS基本为零,但对TP的去除率仅为40%左右;耐冲击负荷性能良好,对COD、氨氮的去除效果均保持稳定;在DO、pH得到适当控制时,系统对COD、NH3-N的去除率分别可达94.2%、92.1%;沉淀区的污泥沉降作用和膜组件区的曝气作用可以有效减缓膜污染速度。

投加气化渣对DMBR处理印染废水效果及污泥性能的影响

通过平行对比实验考察投加气化渣对DMBR(动态膜生物反应器)处理印染废水效果及污泥性能的影响。结果表明,投加气化渣后,污染物(COD、NH3-N、TN、TP、色度)的平均去除率分别增加了6.12%,9.21%,8.14%,2.89%,6.0%,且活性污泥比耗氧速率(SOUR)增大,提高了动态膜生物反应器的处理效能;投加气化渣可降低混合液中EPS含量,增大污泥粒径,减小污泥容积指数(SVI),有效地改善了污泥性能。

一体式A／O／DMBR处理高氨氮化粪池废水的研究

自制了一套新型一体式厌氧/好氧/动态膜生物反应器(A/O/DMBR),并将其应用于高浓度氨氮化粪池废水的处理。结果表明,A/O/DMBR达到了良好的有机物和氨氮去除效果,平均去除率分别为81.5%和87.0%。同时还表现出较强的脱氮能力和较好的稳定性,好氧单元和缺氧单元污泥的比硝化速率和比反硝化速率分别达到2.79、1.33 mg/(g.h)。

DMBR运行过程及膜污染影响因素研究进展

动态膜生物反应器(DMBR)是一种具有广泛应用前景的污水处理新技术,与传统膜生物反应器(MBR)相比,处理效果相当且膜通量更高、膜污染更容易控制。简要分析了自生动态膜及预涂动态膜的形成过程和再生过程,并从膜材料、活性污泥的性质以及运行条件等方面综述了膜污染影响因素的研究进展,指出DMBR研究应用中存在的问题及发展方向。

DMBR-IVCW系统处理生活污水的研究

利用动态膜生物反应器单元和复合式垂直流人工湿地单元组成一个复合系统来处理生活污水。研究了系统和各单元对COD，NH4^＋-N，以及浊度的去除效果，结果表明，系统对它们的总去除率分别为93.35％，97.30％和92.13％；研究了膜易污染情况下膜通量的衰减，分别用0.5％，0.5％，0.1％NaOH溶液5h、10h，10h反冲洗膜，可以使膜通量由原来的43.90％，35.79％和53.50％分别恢复到了87.49％.92.87％和89.48％。

投加PAC延缓HDMBR处理印染废水膜污染研究

将动态膜技术与悬浮填料结合构建复合式动态膜生物反应器(HDMBR),采用HDMBR工艺处理印染废水,研究投加粉末活性炭(PAC)前后对印染废水的污泥混合液特性、胞外聚合物分布及其膜污染的影响。投加和未投加PAC反应器分别标为反应器A和B。实验结果表明:反应器A混合液的EPS增加量、LB-EPS积累量、粒径<10μm的微粒所占比例、膜通量与Zeta电位降低幅度均小于反应器B,投加PAC改善了污泥混合液的性质,有效地减缓膜污染。由膜表面滤饼的三维荧光光谱(EEM)与红外光谱(FTIR)解析,膜表面主要污染物是蛋白质和多糖。PAC的吸附性能及其在滤饼层"骨架"功能,可减少膜表面污泥滤饼层的形成和沉积,有利于延缓膜污染。

重力驱动式动态膜生物反应器的膜清洗再生方式优化研究

构建了重力驱动式好氧动态膜生物反应器(DMBR)处理生活污水,比较不同物理清洗方法(空气反冲洗、表面刷洗和组合方式)对动态膜再生的影响,探究了动态膜的形成过程和过滤机理,解析DMBR的污染物去除性能。研究结果表明,动态膜的形成伴随着出水颗粒物粒径的不断减少,5 min后颗粒粒径分布基本稳定,动态膜形成阶段符合滤饼过滤模型,稳定运行阶段符合标准过滤模型。DMBR对浊度、NH_(4)^(+)-N、COD和SCOD的平均去除率分别为99.6%、94.0%、93.2%和82.8%。空气反冲洗辅助刷洗不仅可以去除微网表面的污染层,还可去除对DMBR长期运行有影响的污染物,五个过滤周期的初始通量恢复率均达到93.1%以上。

投加气化渣对DMBR处理造纸废水污泥性能及膜污染的影响

通过两组对比实验,考察了投加气化渣对动态膜生物反应器(DMBR)处理造纸废水污泥性能及膜污染的影响。结果表明,投加气化渣显著提高污染物的去除率,将反应器对COD、色度、NH3-N的平均去除率分别提高到了96.74%、94.30%、90.86%;混合液EPS含量与粘度、粒径呈正相关,相关系数分别为0.974 9和0.911 5,这说明EPS含量与粘度和颗粒具有较强的相关性。气化渣的投加降低了Zeta电位值增加的趋势,有利于减缓膜污染。

悬浮填料延缓DMBR膜污染的研究

采用两组平行动态膜生物反应器(DMBR)处理模拟生活污水,对比研究投加悬浮填料对DMBR中污泥混合液特性、胞外聚合物(EPS)及膜污染的影响。投加和未投加悬浮填料的反应器分别记为反应器A、B。实验结果表明:运行期间,反应器A混合液中污泥浓度、Zeta电位降低与粘度增加程度、膜通量衰减及膜阻力增大速度均小于反应器B,且Zeta电位与蛋白质含量呈强负向相关、而粘度与多糖含量呈强正向相关。由反应器A、B膜基材的扫描电镜可直观地看出,未投加悬浮填料的膜表面沉积大量的污染物,致使膜孔堵塞;而投加悬浮填料的膜表面污染物较少,抗污染性能明显有所改善。在DMBR中投加悬浮填料有利于延缓膜污染。

厌氧氨氧化动态膜过滤特性及膜清洗策略优化

厌氧氨氧化动态膜生物反应器(Dynamic membrane bioreactor,DMBR)能够高效富集厌氧氨氧化菌,较好克服了厌氧氨氧化污泥富集的困难,但仍缺乏对DMBR动态膜过滤特性及膜清洗方式的研究。本研究考察了动态膜有机组分及其对膜过滤特性的影响,以及基于动态膜的物化性质探究了物理性与化学性膜清洗的作用效果。结果表明,DMBR动态膜中陆源性腐殖质和类血红素类物质与膜阻力呈显著正相关,为关键的膜污染成分;0.5%NaClO溶液浸泡3 h呈现最佳清洗效果,清洗后膜通量恢复率高达98.2%,且能有效去除陆源性腐殖质和类血红素类物质。通过解析动态膜有机组分明确关键膜污染成分并优化膜清洗方式,为解决DMBR工程应用中膜污染控制与清洗策略提供了有力的科学依据。

投加壳聚糖对DMBR处理造纸废水效能及膜污染影响研究

通过两组实验,研究了投加壳聚糖对动态膜生物反应器(DMBR)处理造纸废水的效果以及膜污染的影响。结果表明,投加壳聚糖后,由于壳聚糖的吸附和絮凝作用,可以明显提高污染物的去除率,对色度、浊度、COD、NH_3-N的平均去除率分别提高了8.8%,7.3%,5.7%,7.1%,红外光谱分析表明,膜表面污染物的主要成分为蛋白质和多糖。