【作者】 白玲；

【导师】 蓝伟光； 万金保；

【作者基本信息】 南昌大学 ， 环境工程， 2008， 博士

【摘要】 厌氧膜生物反应器(Anaerobic Membrane Bioreactor,AnMBR)是一种处理高浓度有机废水的有效方法,已成为国外如WERF(Water Environmental ResearchFoundation)等协会研究的重点之一。浸没式MBR由于能耗低、过膜压差(TMP)低和小的占地面积而得到了广泛的应用。但AnMBR的运行方式目前在国内外几乎以外置式为主。是因为浸没式AnMBR的膜污染控制始终无法真正有效地得以解决,而限制了它的应用。因此为了控制、解决浸没式AnMBR中的膜污染问题,我们研发了一套浸没式双轴旋转厌氧膜生物反应器(Submerged Double-shaftRotary Anaerobic Membrane Bioreactor,SDRAnMBR)。系统内装填平板超滤膜,内置的旋转膜组件采用双轴同向旋转,由膜旋转形成的湍流可削弱膜表面的浓差极化及凝胶层的形成,从而有效地控制膜污染,使膜污染降低到最低程度。可将浸没式厌氧膜生物反应器的概念进行真正意义上的落实。我们利用开发的SDRAnMBR处理模拟啤酒废水,系统研究了SDRAnMBR的启动特性、处理啤酒废水的运行效能、膜污染性能及膜污染机理,主要研究成果如下:(1)设计开发了一套SDRAnMBR系统,容器容积120L。有效容积100L,内置的双轴旋转平板超滤膜组件的最大膜面积2.4m~2,双轴旋转最大速度500rpm,最高的平均剪切流速理论值为4.4m/s,满足了一般料液的处理要求。适合用来处理高悬浮物含量、中高浓度的料液。双轴旋转膜组件是本系统的关键和创新部分。(2)由SDRAnMBR的动力学特性的理论分析表明:双轴旋转膜组件在AnMBR中动力学流场中,会产生均匀化效应、交错振动效应和三相旋转流效应。由于他们的协同作用,强化了旋转流的剪切、紊动、振动和传质特性。阻止了复合涡流的产生,降低了渗透反压,可解决单轴旋转膜组件存在的问题。在一定程度上可实现提高膜面流速、降低浓差极化层厚度和渗透液主体浓度以及膜内外的渗透阻力,从而能最大限度降低浓差极化,提高了渗透通量。(3) SDRAnMBR具有良好的启动特性。与常规厌氧生物反应器的启动试验研究对比表明:SDRAnMBR启动速度快,仅用了26天;耐冲击负荷能力强;COD去除率高于常规厌氧生物反应器,稳定在92%以上,约高10%;反应器运行稳定,未发生酸化现象;且出水挥发酸(VFA)和出水的碱度可以在较大的范围变动而不会发生酸化现象。出水碱度为1200～2600mg/L,出水VFA在200～600mg/L范围内,出水碱度/VFA在3.5～6.5之间。而常规厌氧生物反应器则易发生酸化现象,反应器运行稳定性较差。建议直接采用膜生物反应器启动厌氧反应器。(4) SDRAnMBR对啤酒废水有着好的处理效果,负荷提高快,有机物去除率高,系统的耐冲击负荷的能力强,而且运行非常稳定。在正常运行期间,进水COD在2900～5200mg/L,容积负荷为4.97～12.48kgCOD/m~3·d,COD的去除率平均为95.15%。膜的截留作用和三相旋转流的共同作用,加强了在高污泥浓度(MLSS)和高负荷下运行时的混合和传质,从而强化了浸没式AnMBR在高MLSS和容积负荷下运行的稳定性和出水水质。(5) SDRAnMBR具有良好的抗膜污染性能。其运行特点为,在一定HRT、MLSS浓度、膜旋转速度下,系统膜通量和TMP不变,能长期稳定运行。此试验条件下最佳操作参数为:水力停留时间(HRT)为10h,容积负荷(10.52～12.09kgCOD/m~3·d),MLSS(18～19.5g/L),膜旋转速度为150rpm,膜通量(30.75～31.31L/m~2·h),TMP(12～13kPa)。由此可见,采用SDRAnMBR处理废水,能大幅度减轻浸没式AnMBR在高MLSS和高容积负荷下运行的膜污染,实现了在较低膜旋转速度、较短的HRT、较大的容积负荷、较大的MLSS、较大的膜通量和低TMP下的浸没式AnMBR的长期稳定运行。(6) SDRAnMBR中良好动力学特性(均匀化效应、交错振动效应、三相旋转流效应)、膜的截留作用和厌氧颗粒污泥的协同作用的结果,能大大减轻由剪切力过大对污泥活性的影响,并提高了污泥活性;抑制了胞外聚合物(EPS)在污泥混合液中由于MLSS增大而造成的快速积累,同时也抑制了污泥粘度的快速增大。使之能在一定MLSS和污泥粘度范围内膜过滤阻力保持不变。从而大幅度减缓了膜污染。并使之能在较高的MLSS(18～19.5g/L)、较高的EPS浓度(50.9～63.9 mg/gMLSS)、较小的污泥颗粒粒径(4.00～36.54μm)和较大的污泥粘度(6.6～7.5mPa·s)时稳定运行。进一步说明SDRAnMBR强化了膜组件的抗污染性能。(7)提出了SDRAnMBR的膜污染机理。一是膜污染阻力占总阻力的89.68%。其中外部阻力(即浓差极化阻力和泥饼阻力之和)是膜污染的主要成部分,占到总阻力的76.34%。膜本身阻力和内部阻力与外部阻力相比所占比例较小,分别占总阻力的10.32%和13.34%。因此污染阻力主要是由泥饼层引起的,整个过滤过程以泥饼层控制为主。经过146天的运行,膜表面泥饼层仍然较薄而且松散,膜污染速率缓慢,膜污染较轻,过滤阻力随时间的增大的速率非常缓慢,并在一定膜转速下,过滤阻力保持不变。证实了本MBR系统能有效地减小浓差极化和避免污泥颗粒在膜表面的沉积,有效控制膜污染;二是在SDRAnMBR运行的146天里,只发生了阶段1(短时间快速TMP上升)和阶段2(长期慢速的TMP呈线性上升),阶段3(突然的快速的TMP上升)未发生。即把阶段1的膜污染限定在了更短的时间范围内(40min);大幅度延长了阶段2的操作时间,并使会导致过滤无法继续的阶段3未发生。达到了MBR可持续操作的要求。总体来说,SDRAnMBR能最大限度减轻和控制浸没式AnMBR的膜污染,使之能够在低污染情况下和高负荷下长期稳定运行,并保持稳定的运行通量;可较长期的运行而不需清洗,使能耗大幅度降低;成功地解决了浸没式AnMBR膜污染控制存在的问题,使之成为高效、稳定的厌氧MBR系统。证实了对SDRAnMBR动力学特性的理论分析,具有良好的应用前景。更多还原

【Abstract】 Anaerobic membrane bioreactor (AnMBR) is an effective process to treat high concentration organic wastewater and has become one of research emphases of foreign associations such as WERF (Water Environmental Research Foundation). The application of submerged MBRs is very extensive because of lower energy consumption and low transmembrane pressure(TMP) and small footprint. However, most of AnMBR have been conducted with external configureations at present, owing to membrane contamination control of submerged AnMBR has never been able to solve effectively so as to limit its application. In order to control and resolve membrane fouling problem in submerged AnMBR, we developed a set of submerged double-shaft rotary anaerobic membrane bioreactor (SDRAnMBR). System container is filled with flat-sheet Ultrafiltration membrane. Internal rotary membrane module adopted double shaft rotation in the same direction. Turbulence coming from membrane rotation could undermine concentration polarization on the membrane surface and formation of gel layer ,so as to control the membrane fouling effectively and make it reduce to the minimum. It is necessary to realize the concept of submerged AnMBR into implementation. We used the developed reactor to treat synthetic bear wastewater. Discussed and studied some characteristics of SDRAnMBR in detail such as launch characteristics,operation efficiency , performance and mechanism of membrane fouling within SDRAnMBR, the main research results as follows:(1) A set of SDRAnMBR system was designed and developed. System volume of container and its effect one were 120 L and 100 L , respectively, filled with innovative double-shaft rotary flat-plate Ultrafiltration membrane module, loaded with the largest membrane area of 2.4 m~2, maximum double-shaft rotary speed was 500 rpm, the average maximum theoretical value for the shear velocity is 4.4 m / s. So that it can meet the general requirements for the feed fluid treatment, suitable for treating feed fluid of high suspended substances, moderate and high concentration. Thereinto, the double-shaft rotational membrane module was the key and novel part of the newly reactor.(2) The results of theoretics analysis on characteristics of hydraulics dynamics indicated that the effects of equality, interleaving oscillation and three-state rotating flow were produced within SDRAnMBR. So it enhanced the characteristics of shear , turbulence, oscillation and mass transfer within rotating fluid. It were prevented and reduced that composite whirlpool and permeate backpressure from rotational membrane module. It resolved successfully problems of one-shaft rotational membrane module in submerged AnMBR. In a certain extent,it was realized that increasing velocity of flow on membrane surface , reducing concentration polarization and main body concentration of permeate fluid and resistance inside and outside of membrane. So that it could furthest decrease membrane fouling and increase permeate flux.(3) Characteristics of SDRAnMBR start-up was well. Compared to the start-up of conventional anaerobic bioreactor, its start-up velocity was rapid during 26 days, strong ability of endurance impact loading, high COD removal rate which stabilized at above 92% ,about more 10% higher than conventional anaerobic bioreactor. The reactor run steadily and the acidification phenomenon has not happened. Furthermore, the effluent volatile fatty acid (VFA) and effluent alkalinity changed in the larger range and acidification phenomenon will not happen. Effluent alkalinity were in the range 1200-2600mg/L, effluent VFA were in the range 200-600mg/L,and the rate of alkalinity on VFA were between 3.5 and 6.5. However, the conventional anaerobic bioreactor was vulnerable to acidification with poor stability. Direct use of membrane bioreactor to start up anaerobic reactor was suggested.(4) SDRAnMBR had good treatment effect for synthetic beer wastewater and the system not only run steadily but organic loading enhanced fast , had a strong impact resistance capacity and a high rate of organic substrate removal. During the normal operation, When influent COD were in the range 2900-5200mg/L and volume loading rate were in the range 4.97-12.48 kgCOD/m~3·d, COD removal rate was an average of 95.15%. Because of common action of membrane interception and three-state rotating fluid , the effluent quality and operation stability were strengthened consumedly at high mixed liquor suspended solids (MLSS) and high volume loading rate.( 5 ) SDRAnMBR had good anti-contamination performance. Membrane flux ,TMP , filtration resistance immovability and long-term steady running were its mainly running characteristics, when operated at definite range of MLSS and hydraulic retention time(HRT) and membrane rotational speed .The optimal operation parameters were that HRT was 10h, volume loading rate were in the range 10.52-12.09 kgCOD/m~3·d, MLSS were in the range 18-19.5g/L, membrane rotational speed was 150rpm, membrane flux were in the range 30.75-31.31L/m~2·h and TMP were between 12 and 13 kPa under this test condition. Therefore, SDRAnMBR can furthest decrease membrane fouling under high volume loading rate and MLSS. It was realized long-term steady running when operated at lower membrane rotational speed, shorter HRT, higher volume loading rate, biggish MLSS, lower TMP and larger membrane flux.(6) The well characteristics of hydraulics dynamics(equality, interleaving oscillation and three-state rotating flow effect) and cooperate action with membrane interception , anaerobic granules sludge in SDRAnMBR, could decrease the effects on sludge activity come from the shear stress excess bigness, restrain speediness accumulation of extracellular polymeric substances(EPS) in sludge mixed liquor due to MLSS accretion, as well as restrain speediness accretion of sludge dynamic viscosity too. Thereby membrane fouling was reduced consumedly and resulted in membrane filtration resistance immovability when operated at definite range of MLSS and sludge viscosity. It was realized steady running when operated at biggish MLSS (between 18 to 19.5g/L)> higher EPS (between 50.9 to 63.9 mg/gMLSS)、small sludge particle size (between 4.00 to 36.54μm)和larger sludge viscosity(between 6.6 to 7.5 mPa·s). The finging was more identified that membrane module strengthened anti-contamination performance.(7) We also put forward the fouling mechanism in SAnRMBR. Firstly membrane fouling resistance (concentration polarization and cake layer formation) was 89.68%,The external resistance was 76.34% of total resistance.Accordingly,the intrinsic membrane resistance and internal fouling resistance were 10.32% and 13.34% of the total resistance, respectively. Therefore , membrane filtration resistance was arose from the cake layer, its controlling was the predominant during whole operated period. Furthermore ,cake layer was thinner , membrane fouling velocity was very slowly and membrane fouling was very slight with running time during operated 146 days. The membrane filtration resistance was immovability when operated at definite membrane rotational speed . The finging was more identified that SDRAnMBR was effective in minimizing concentration polarization resistance by reducing the accumulation of solute molecules on the membrane surface, and consequently reduced the potential for membrane fouling. Secondly, among membrane fouling 3 stage, which occurs only the stage 1 (an initial short term rise in TMP ) and stage 2 (long-term rise in TMP, either linear or weakly exponential), and that stage 3 (sudden TMP rise, also known as the TMP jump) without occurs in running 145 days by SDRAnMBR. moreover, So sustainable operation the aim was realized by limiting shorter time of stage 1 (40min), prolonging stage 2 consumedly and avoiding stage 3 since it could be difficult to restore.In a word , SDRAnMBR could furthest decrease and control membrane fouling of submerged AnMBR ,and that was realized long-term steady running when operated at lower membrane fouling and higher volume loading rate, with could keep steady flux. So it does not demand to clean chronically, thereby energy consumption was reduced consumedly. The problems of membrane contamination control in submerged AnMBR were resolved successfully, and it became system of high-efficiency and stabilization. The theoretics analysis on double-shaft rotating fluid was identified ,and that it will have well application prospect by SDRAnMBR.更多还原