【作者】 刘强；

【导师】 王晓昌；

【作者基本信息】 西安建筑科技大学 ， 市政工程， 2009， 博士

【摘要】 论文为国家自然科学基金重点项目和重大国际合作项目的部分研究内容,采用复合式膜生物反应器（HMBR）进行城市生活污水处理的实验研究,重点研究了反应器的EPS分布特性及膜污染控制原理。与常规膜生物反应器（CMBR）相比,HMBR借助于活性污泥中悬浮生长的微生物和载体表面生物膜中附着生长的微生物的综合作用,体现出了良好的膜污染控制能力。论文的主要工作及成果如下:1.通过HMBR和CMBR的对比试验,研究了生物载体投加对污染物去除的强化作用。结果表明,对有机物而言,HMBR的COD和BOD₅去除率分别为94.2%和98.5%,比CMBR均提高了3.8%;对营养物质而言,HMBR的NH₄⁺-N、TN和TP去除率分别为97.2%、51%和81.5%,比CMBR分别提高了4.2%、13.7%和1.7%,说明HMBR显著提高了反应器的反硝化效能;HMBR对浊度的去除率与CMBR基本相同,但对色度的去除率比CMBR提高了8.2%;生物载体投加后总体生物量的增加和生物膜中附着生长微生物的作用是HMBR污染物去除效率提高的主要原因。2.比较了HMBR和CMBR的膜阻力变化情况。结果表明,生物载体投加后随着生物膜的形成和成熟,化学清洗后一个周期内跨膜压差（TMP）的增长速度明显减慢。与生物载体投加前TMP增长到20 kPa的运行时间57天相比,生物载体投加后TMP增长到20 kPa的运行时间延长到了92天,而下一个周期运行140天之后TMP仅增长到16 kPa,说明HMBR有效地控制了膜污染,大幅度地延长了膜的过滤周期。3.分析比较了HMBR和CMBR的胞外多聚物（EPS）分布特性。结果表明,在溶解性EPS（S-EPS）、松散附着性EPS（LB-EPS）和紧密附着性EPS（TB-EPS）这3种胞外多聚物中,无论采用哪种提取剂进行提取,TB-EPS都是EPS的主要成分,占EPS总量的比例均在60%以上,而S-EPS和LB-EPS所占的比例差别不大。HMBR能够有效去除S-EPS和LB-EPS,二者的含量均比CMBR的条件下降低了42%左右;TB-EPS含量也有所降低,但降低幅度仅在2%左右。4.分析了附着性EPS（B-EPS,包括LB-EPS和TB-EPS）和S-EPS含量对膜阻力的影响。对于B-EPS,发现其含量直接影响反应器中活性污泥的物理性质,即随着B-EPS含量的降低,污泥的絮凝性和沉淀性提高,粒径增大,絮体结构趋于密实。与TB-EPS相比,LB-EPS含量对污泥物理性质的影响更为明显。经过相同运行时间后对HMBR和CMBR的滤饼层阻力R_c进行的测定结果表明,前者仅为后者的43%。由此推断,通过对B-EPS的去除以改善活性污泥的物理性质,进而减缓滤饼层阻力的增长速度是HMBR有效控制膜污染的重要原因。对于S-EPS,可认为在HMBR运行条件下其含量的降低对滤饼层阻力的影响不大,而主要是减缓了膜孔阻力R_p的增长速度（经过相同运行时间后HMBR膜孔阻力的实测结果为CMBR的56%）,这是HMBR有效控制膜污染的另一个重要原因。5.对HMBR和CMBR膜阻力的构成情况进行了实测分析,发现经过一定时间运行后滤饼层阻力R_c比膜孔阻力R_p高一个数量级,而R_p与膜固有阻力R_m′处于同一数量级,说明R_c是影响跨膜压差TMP变化的主要因素。为此,建立了HMBR和CMBR的滤饼层阻力模型,并运用该模型对反应器中TMP的变化规律进行了模拟计算,结果表明:在忽略R_m′和R_p的情况下,运行初期阶段TMP的计算值低于实测值,说明此时膜固有阻力和膜孔阻力对TMP变化的影响较大;运行中期阶段TMP的计算值与实测值基本吻合,说明此时R_c是TMP变化的主要影响因素;后期阶段TMP的计算值低于实测值,且计算结果没有出现实测值中TMP最后加速上升的情况,说明R_p有可能在过滤后期成为TMP变化的主要影响因素。然而,模拟计算的结果很好地再现了HMBR有效减缓TMP增长速度,延长膜过滤周期的作用。同时通过计算与实测结果的比较可知,将膜过滤周期控制在R_c起主要作用的阶段内将有效抑制TMP的加速上升,是通过运行优化控制膜污染的可选策略。更多还原

【Abstract】 This work was supported by the National Natural Sciences Foundation of China （50138020） and the National Natural sciences Foundation of China（50621140001）.A hybrid membrane bioreactor（HMBR） which was developed by introducing the biofilm carriers into a conventional membrane bioreactor（CMBR） was exploited in the treatment of municipal wastewater and attention was mainly focused on its extracellular polymeric substances（EPS） distribution characteristics and membrane fouling control mechanism.Comparing with the CMBR which has only suspended biomass in the reactor,the HMBR has additional attached biomass and thus represented a good performance of membrane fouling control.Results are summarized as follows:1.Through the comparative experimental study between the CMBR and HMBR, the contaminants removal enhancements by the biocarriers was studied.Results showed that,the HMBR can remove the organic substances effectively,COD and BOD5 removal was 94.2%and 98.5%,respectively,which was both enhanced by 3.8% comparing with the CMBR;the HMBR can remove the nutrients effectively,NH₄⁺-N, TN and TP removal was 97.2%,51%and 81.5%,respectively,which was enhanced by 4.2%,13.7%and 1.7%,respectively,comparing with the CMBR;the turbidity removal by the HMBR was as same as the CMBR while the color removal by the HMBR was enhanced by 8.2%comparing with the CMBR;the additional biofilm and the increased total biomass in the reactor was the main reason that the HMBR can enhance the contaminants removals.2.The membrane resistances in the CMBR and HMBR was compared and results showed that,with the increase of attached biomass in the HMBR,the transmembrane pressure（TMP） increased much slower than that of the CMBR.When the TMP reached to 20 kPa,the CMBR lasted only for 57 days,while the HMBR lasted for 92 days in the first period after chemical cleaning.In the second period,the TMP in the HMBR was only 16 kPa when the reactor was operated for 140 days.These evidence indicated that the HMBR can retard membrane fouling effectively.3.The EPS distribution characteristics in the CMBR and HMBR was studied and results showed that,among three EPS namely the soluble one（S-EPS）,the loosely bond one（LB-EPS） and the tightly bond one（TB-EPS）,TB-EPS was the main component without reference to the extraction method and accounted for more than 60%of the total.The S-EPS and LB-EPS in the HMBR were both decreased by about 42%and the TB-EPS in the HMBR was decreased by about 2%comparing with the CMBR,indicating that the HMBR can remove EPS effectively,especially for S-EPS and LB-EPS.4.The effect of bound EPS（B-EPS） and S-EPS on the membrane resistance was analyzed and results showed that,B-EPS had a tightly correlation with sludge physical properties.With the decrease of B-EPS,the sludge bioflocculation and settleability was enhanced,the floc diameter was increased and the floc was more compact.B-EPS was subdivided into LB-EPS and TB-EPS.LB-EPS had a more tightly correlation with the sludge properties than TB-EPS.After the same operational period,the cake layer resistance R_c in the HMBR accounted for 43%of that in the CMBR.It can be concluded that,the decrease of B-EPS enhanced the sludge properties and finally slowered the increase of the cake layer resistance,this was the main reason that the HMBR can retard membrane fouling effectively.For S-EPS,its decrease was supposed to affect the pore resistance Rp significantly.After the same operational period,R_p in the HMBR accounted for 56%of that in the CMBR.This was another important reason that the HMBR can retard membrane fouling effectively.5.The constituents of total membrane resistance in the CMBR and HMBR was studied and results showed that,among three membrane resistances namely intrinsic membrane resistance R_m,pore resistance R_p and cake layer resistance R_c,the last one was the main fraction and accounted for more than 70%of the total.Therefore,a cake layer resistance model in the HMBR and CMBR was founded respectivly and was exploited to simulate the variation of TMP in the reactor.Results showed that,when R_m and R_p was ignored,the model calculation was more lower than the experimental results in the first period of filtration,indicating that R_m and R_p affected membrane fouling significantly in this period;the model calculation was nearly equal to the experimental results in the second period of filtration,indicating that R_c was the main fraction of the total in this period;in the end of filtration,the model calculation was more lower than the experimental results and Rp probably turned into the main fraction that affected TMP variation in this period.However,the model calculation reproduced that the HMBR can retard membrane fouling effectively and can prolong the filtration period.At the same time,through the contrast between the model calculation and experimental results,it can be concluded that if the membrane was operated in the period when Rc was the main fraction of the total,the TMP increase can be controlled effectively.更多还原