【作者】 曾海燕；

【导师】 万金保；

【作者基本信息】 南昌大学 ， 环境工程， 2010， 硕士

【摘要】 膜生物反应器(MBR)作为一种新型高效的水处理技术,具有占地面积小、出水水质好、有机负荷高、剩余污泥产率低、运行启动快、可实现模块化等优点而日益受到人们的关注。然而,在运行过程中由于膜污染存在导致过滤阻力不断增加、膜通量严重衰减、膜组件更换和清洗的频率增加等一系列问题,膜污染已成为限制MBR广泛应用的瓶颈。因此如何控制膜污染一直是当前研究MBR的热点。臭氧作为一种高效的、无二次污染的强氧化剂,在膜过滤系统中广泛运用。由于本实验室在臭氧氧化同步污泥减量工艺的研究中,发现投加适量臭氧至MBR中能达到污泥减量,同时还能改善膜污染,因此本试验采用臭氧+MBR工艺来研究臭氧对膜污染的影响。主要内容包括四部分：①膜的清水实验；②臭氧投加量优化实验；③操作条件优化；④在前面实验结论的基础上,长期对比运行MBR与臭氧化MBR两套系统达175天,综合分析臭氧控制膜污染的效果及污泥减量效果。研究结果表明：(1)膜组件1与膜组件2的膜比通量与过膜压差的关系直线的斜率分别K1=0.104,K2=0.119,数值基本相等,表明两个膜组件相关性比较好,可比性强,可为后续对比研究膜污染奠定基础。(2)臭氧投加量为32.23mg.1-1,作用时间为15min时,膜比通量值达到最高值0.96LMH/kPa。臭氧作用于污泥混合液后,污泥混合液的MLSS基本上呈下降的趋势,粘度变化不大。污泥中的TOC、多糖、蛋白质质量浓度都随着臭氧投加浓度的增加及作用时间的延长而增加,而SOUR及pH会逐渐降低,但不至于影响微生物的生存,这可为臭氧直接充入MBR中用于减缓膜污染研究提供一定的理论支持。(3)考察抽吸压力、抽停时间比、曝气量三个工艺参数对膜通量衰减的影响,结果表明：①最佳的抽吸压力≤0.03MPa,当大于0.03MPa时,其膜通量的衰减速率增大；②最适的抽停时间比为9：1；③最适的曝气量为100 L.h-1,曝气量为200 L.h-1时的膜通量并未明显优于100 L.h-1,这归功于本反应器的圆形构造和微孔曝气结构,使得曝气产生的气泡粒径小、分布均匀,传质速率快,曝气充分又不易形成死角。(4)平行运行臭氧化MBR及MBR175天,三个阶段中臭氧化MBR与MBR的膜比通量SF值呈现相同的规律：与MBR对比,臭氧化MBR膜污染前期发展迅速,而后期增长缓慢。(5)对第三阶段运行44天后的膜组件污染阻力构成进行分析,结果发现：①MBR比臭氧化MBR膜污染严重。MBR膜污染的总阻力值达到21.08×1012m-1,滤饼层阻力Rc、不可逆阻力Rp、固有阻力Rm分别占总阻力的56.31%、24.86%、18.83%,而臭氧化MBR只发展到17.95×1012m-1,其中Rc、Rp、Rm分别占总阻力的40.72%、36.66%、22.62%；②无论MBR还是臭氧化MBR,滤饼层阻力Rc始终是膜污染的主要阻力；③与MBR相比,臭氧化MBR由于臭氧作用后膜的Rc相对减小,而Rp却增大。(6)不同清洗方式膜通量恢复实验进一步说明了膜污染主要以滤饼层为主,对滤饼层污染物进行FTIR分析得到以多糖和蛋白质为主的EPS是膜面有机物污染的主要成分。相比于MBR,臭氧化MBR能有效减缓无机物污染如Fe、Ca的沉积。(7)忽略膜清洗及取样测试的污泥损耗,两系统运行175d污泥变化情况为：MBR污泥浓度增长迅速,从5282mg.L-1增加到12740mg.L-1,总共增加了7458mg.L-1；而臭氧化MBR中污泥浓度从5310mg.L-1增加到8698mg.L-1,总共增加了3388mg.L-1,其污泥增加量只占MBR增加量的45.4%,表明臭氧化MBR确实有污染减量的效果。(8)臭氧化MBR对COD、NH3-N和TP的平均去除率分别达到90%、95.8%、62.1%,膜出水水质略差于MBR,但其影响程度不大。本研究所采用的臭氧化MBR是直接把臭氧通入MBR,发现投加适量臭氧,此工艺能在保证出水水质的条件下不仅能减缓膜污染,还能达到污染减量的效果。本研究可为今后臭氧用于MBR中减缓膜污染或污泥减量提供一定的参考。更多还原

【Abstract】 As a new highly effective water treatment technologies, Membrane bioreactor (MBR) has many advantages such as small footprint, good water quality, high organic load, low sludge production, easily start, can be realized modular and so on. It receives people’s attention increasingly. However, the existence of membrane fouling bring a series of problems such as fast increasing of filtration resistance, serious weaken of membrane flux,short frequency of replacement and clean membrane module. Membrane fouling has become the bottleneck for the widely used of MBR. Therefore, how to control the membrane fouling has been the focus of the current research about MBR.Ozone, as a highly efficient and no secondary pollution strong oxidants, has been used widely in membrane filtration systems. In our laboratory’s previous study of sludge reduction by ozonation, we found that the way adding proper amount of ozone to the MBR, can achieve the reducing of sludge as well as the mitigating of membrane fouling, so in this study, it couples ozone with MBR in order to study the impact of ozone to membrane fouling. The contains mainly including four parts:①test of membrane function in distilled water;②test of optimization about ozone dosage;③test of optimum operating conditions;④comparing MBR and the ozone +MBR two sets of systems on long-run, analysis of the mitigating of membrane fouling and the effect of sludge reductionThe results show that:(1) The slope of membrane module 1 and membrane module 2 about the relationship between specific flux and membrane pressure is K1=0.104, K2=0.119 respectively, it means that these two membrane modules have a strong comparability, which is the foundation of the subsequent research in membrane fouling(2) In the test of optimization about ozone dosage, the highest specific flux can reach up to 0.96LMH/kPa on the condition of ozone dosage was 32.23mg.l-1 and the reaction time was 15min. the characteristics of sludge mixture change a lot after ozonization the concentration of MLSS basically shows a downward trend, the viscosity changes little, the concentration of TOC、polysaccharide and protein in the sludge increases with the large of dosage concentration and the long of reaction time. The value of SOUR and pH decrease a little, but it doesn’t affect the survival of microorganisms. All these results have provide theoretic support for mitigating membrane fouling in ozone +MBR process.(3) In the optimization test of operating conditions, It investigated the effect of membrane flux by three operating parameters including suction pressure, aeration, the ratio of stop/run. the results showed that:①the best suction pressure≤0.03MPa, when more than 0.03 MPa, the decay rate of flux increases fast;②the optimal ratio of pumping suction/stop was 9:1;③the optimal aeration quantity is 100 L. h-1. when at aeration capacity of 200 L.h-1 the membrane flux was not significantly better than the 100 L. h-1,this may thanks to the circular structure of reactor and the microporous aeration structure, it will produce small、uniform size bubble, accelerate the mass transfer and give full play of aeration without the formation of dead angle.(4) Running two systems parallel for 175 days, it found the SF values in three stages of 175 days shows the same regulation that the membrane fouling in ozone +MBR process developed rapidly at first, and later slowly, compared with the MBR process.(5) It investigated fouling resistance composition of the third stage’s membrane modules which have run for 44 days. The results showed:①the membrane fouling in MBR process is more serious than ozone +MBR process. in MBR, the total resistance reached 21.08×1012m-1,the rate of cake layer resistance Rc, the irreversible resistance Rp, natural resistance Rm is 56.31%,24.86%,18.83%, while ozone+MBR process is only developed to 17.95×1012m-1, The rate of Rc,Rp, Rm is 40.84%,36.66%, 22.62%;②Whether in ozone +MBR or MBR process, cake layer resistance Rc is always the main resistance in all kinds of fouling;③Compared with the MBR process, in ozone +MBR process cake layer resistance Rc is relatively reduced,but the irreversible resistance Rp was increased.(6) The experiments by different cleaning methods to restore flux further showed that cake layer fouling is the majority part in membrane fouling whether in ozone +MBR or MBR process, meanwhile, through the analysis of membrane surface pollutants by FTIR it shows the main components of organic pollution is EPS which mainly contain polysaccharide and protein. Ozone +MBR process can migitate inorganic fouling such as Fe, Ca deposition..(7) Without regard to loss of sludge in membrane cleaning and sampling, both of two systems didn’t discharge sludge during a long period of 175 days of experiment operation, the sludge concentration of control reactor increased by 7458mg·L-1 from 5282mg·L-1 to 12740mg·L-1. But the sludge concentration of ozone +MBR reactor just increased by 3388mg·L-1 from 5310mg·L-1 to 8698mg·L-1. The increased amount of sludge in ozone +MBR process only account for 45.4% of the MBR process, it meant that the ozone +MBR process did have the effect of reducing sludge.(8) The average removal rates on COD, NH3-N and TP in ozone+MBR process can reach 90%,95.8%,62.1% respectively. The water quality of membrane effluent in ozone +MBR process is slightly worse than MBR process, however the impact is only a little.By adding ozone directly to MBR, the research found that with the proper amount of ozone, the ozone +MBR process can achieve not only reducing the sludge, but also mitigating membrane fouling in the condition of ensuring the effluent’s water quality, this research will provide some reference for the ozone +MBR process whether it is used for sludge reduction or controlling membrane fouling.更多还原