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1、 斜板沉淀池在一体化氧化沟中的作用摘要：对一体化氧化沟中斜板沉淀池内部的流态及固液分离效果进行了研究，探讨了其分离机理和影响因素。试验结果表明：沉淀池底部设有的特殊过渡区具有良好的消能作用，可使斜板沉淀区的流态快速从紊流转变为层流，达到最佳沉淀效果。斜板区的分离过程是污泥沉淀与污泥悬浮层的过滤、捕获共同作用的结果，其效率比一般二沉池高，水力停留时间30 min，出水SS值38 mg/L。 关键词：一体化氧化沟 斜板沉淀池 固液分离 流态 氧化沟由于其构造简单和运行管理简便已发展成为污水生物处理的主要方法之一。为了适应防止水体富营养化的要求，经过适当的调整和改造，氧化沟在去除污水中有
2、机污染物的同时，还可完成生物脱氮和除磷13，因此氧化沟被各国广泛采用。一体化氧化沟(Integrated Oxidation Ditch)是将沉淀池与氧化沟合建，无单独的污泥回流系统，基建投资和运行费用均较低，并在一定程度上弥补了传统氧化沟占地大的缺点。由于污泥回流及时，减少了污泥膨胀的可能。氧化沟内多水深2 m，目前也有深达34.6 m的。为了避免污泥沉积到沟底，沟内混合液的循环流速0.3 m/s，通常为0.30.5 m/s4。这就使得沟内循环的混合液具有较高的动能。由于受氧化沟结构和运行方式的限制，与氧化沟合建的沉淀池应满足：沉淀池与氧化沟的容积比尽可能小；削减进入沉淀区混合液的能量，以保
3、证高效沉淀。目前应用较多的有BMTS式和船式5、6，斜板沉淀池由于池深浅、占地少、固液分离效果好，也已在一体化氧化沟中广泛应用。1试验装置氧化沟主体和斜板沉淀池模型均用有机玻璃制作。污水由高位水箱经转子流量计流入氧化沟中，并迅速与沟内原有混合液混合。经多次循环处理后，与进水等量的混合液在沉淀池内固液分离，经出水堰排出(见图1)。由于试验模型较小，没有适当规格的曝气转刷可以安装，所以在氧化沟的一端转弯处设一台搅拌机推动混合液在沟内循环流动(转速在100250 r/min之间调节)。搅拌桨的型式类似于曝气转碟，在平面圆盘上固定6片桨板。鉴于搅拌机的供氧能力有限，在进水口前设置一充氧泵。氧化沟模型长
4、为0.8 m，设有沉淀池的廊道宽为0.1 m，另一廊道宽为0.07 m，有效水深为0.3 m，有效容积为41 L。试验中采用斜板沉淀池作为沟内合建的沉淀池。其迎水面制成坡形，防止沟内混合液在沉淀池前由于截面突缩出现旋涡流。在斜板底部设置双层穿孔板作为过渡区，以消耗混合液上升时挟带的动能。沉淀池出水堰口为锯齿型，保证出水均匀和各个斜板间布水均匀、负荷相等。沉淀池底部长为0.20 m，宽为0.05 m ，距沟底0.05 m，侧面廊道宽为0.05 m。沉淀池容积占氧化沟总容积的6.13%。试验历时9个月，污水取自哈尔滨市马家沟河，水质情况(如表1)为典型的城市污水。处理水量为0.67.8 L/h，原
5、水温度基本随季节而变(1027 )，污泥浓度为22.8 g/L，MLVSS为1.41.9 g/L。水质与污泥指标采用标准方法检测。表1马家沟河污水水质项目数值pH6.07.2SS(mg/L)60160CODCr(mg/L)258.9407.5BOD5(mg/L)100.3144.8NH3-N(mg/L)18.230.5TKN(mg/L)23.841.2TP(mg/L)4.58.62斜板沉淀池内流态与固液分离效果斜板沉淀池内的流态如图2所示，共分为4个区：主流区、过渡区、斜板区和清水区。2.1主流区主流区即位于沉淀池底部的氧化沟混合液的流动区，其主要作用是传输待分离的混合液进入沉淀池，沉淀后的污
6、泥又经此进入氧化沟中随混合液继续循环。为防止氧化沟内混合液中污泥沉积，其混合液平均流速取0.35 m/s。设有沉淀池的廊道的过水断面面积为0.03m2；在沉淀池处，由于其占据一定的断面，因此过水断面面积减小至0.0175m2。根据物料平衡原理，沉淀池底部主流区内混合液的平均流速为0.6 m/s。此时水流除水平流速外，还有上、下、左、右的脉动分速，且伴有小的涡流体，属紊流状态，在一定程度可使密度不同的水流较好地混合。为使颗粒沉淀，在进入沉淀池斜板区之前必须降低雷诺数以利于颗粒的沉降。2.2过渡区位于斜板下部的双层穿孔板的作用是消能和调整流态，称为过渡区。当混合液流径过渡区时，由于穿孔板的阻力和孔
7、径的放大，向上的流速降低和水流本身旋转产生的涡流使混合液的能量迅速降低。斜板沉淀池作为二沉池的表面负荷一般为46 m3/(m2h)，相应的斜板区内水流上升速度也为1.111.67 mm/s。过渡区消能作用可以用主流区和斜板区的动能比值表示：E主流E斜板=0.60 m/s21.11 mm/s2=2.9105由上式可1知，过渡区将混合液的能量衰减了5个数量级。若拆除过渡区双层穿孔板，不能消除混合液进入斜板区带有的较大动能，污泥严重上翻，固液分离效果极差，出水中SS高达300 mg/L。过渡区的作用还包括均匀进水和作为污泥回流的通道起着双向传输的作用。由于进水不均匀会使部分斜板负荷高而其他斜板负荷低
8、，造成局部积泥、出水SS升高。沉淀池底部主流区内混合液的平均流速为0.6 m/s，是独立设置在斜板沉淀池底部过渡区中水流速度(1025 mm/s)的2050倍，因此双层穿孔板对保证配水均匀是必不可少的。2.3斜板区斜板区是污泥与水分离的实际区域，即工作区。污泥絮凝体在这里形成并在重力作用下沉降到斜板上，澄清后的污水进入清水区。在过渡区形成的污泥颗粒絮凝体在不断上升的水流带动下进入斜板沉淀区，在斜板上与重力平衡时形成的动态污泥悬浮层相遇，使不断上涌的混合液中污泥颗粒被捕获和过滤。悬浮污泥层的厚度是变化的，当厚度达到一定程度时，重力足以抵抗摩擦力，污泥层就会下沉到氧化沟中进入主流区。此后，从斜板上
9、下滑的污泥层又会逐渐积累，再滑落至氧化沟内周而复始。相对于过渡区对上升水流的阻力而言，悬浮污泥层的动态变化对整个污泥沉降过程没有太大的影响，试验结果也证明了这一点。从理论上讲，沉淀池的出水效率在很大程度上由混合液的上升流速和污泥沉速决定，只有当污泥沉速大于上升流速时，沉淀才能发生。但由于动态污泥悬浮层的存在，水中的颗粒有充分的机会和活性污泥悬浮层的颗粒碰撞凝聚，其沉速远远大于同条件下的静态沉速，从而可以提高上升水流速度或产水量。斜板间的污水流动状态理论上应为层流，其雷诺数为15。从图2可以看出，斜板之间的流动状态并不是完全的层流，从过渡区上升的旋涡流还需要一段时间和距离才能扩散和稳定，因此只能
10、说斜板区的中、上部水流处于层流状态。过渡区上升旋涡流对斜板的冲击影响与混合液的能量及分布的均匀性有关。混合液通过悬浮污泥层类似于絮凝沉淀过程，而混合液的上升流速与污泥的体积浓度有关。上升流速越大，体积浓度越小，悬浮污泥层厚度相应增大。当上升流速接近于自由沉速时，体积浓度接近于零，悬浮污泥层消失。反之，当上升流速越小，悬浮层体积浓度越大。因此水量越大，上升流速越大，过渡区的上升旋涡流对斜板的冲击影响与混合液的能量也越大，斜板底端的紊流区域增加，悬浮污泥层厚度相应增大。当达到某极限值时，出水SS猛增，斜板顶部污泥开始上翻，此极限即是斜板沉淀池的污泥穿透临界点。混合液冲击能量和沉淀池水力停留时间与出
11、水SS的关系，如图3所示。由图3可知，随着停留时间缩短，出水SS逐渐增大。但当水力停留时间30 min时，出水中的SS38 mg/L；当水力停留时间30 min时，出水中的SS值猛增至6998 mg/L。试验表明，可将水力停留时间=30 min作为该斜板沉淀池的污泥穿透临界点。2.4清水区清水区能够分隔沉淀工作区与出水堰区域，使斜板区的沉降过程不受出水水流影响。锯齿形溢流堰比普通水平堰更易加工也更易保证出水均匀。 3影响沉淀效果的因素3.1斜板倾斜角度试验中改变沉淀池的斜板倾斜角度，利用出水的SS值来判断出较佳的斜板倾斜角度。表2为倾斜角与出水中SS的关系。由试验数据可知，斜板呈6
12、5和70倾角时，出水水质较好。表2斜板倾斜角与出水中SS的关系斜板倾角()5560657075出水SS(mg/L)4038342337沉淀池的固液分离过程包括污泥颗粒在斜板区的沉降和絮凝体沿斜板的下滑回落到氧化沟中。在斜板区污泥颗粒受到的作用力有：自身重力、混合液的冲击力、斜板的弹力和摩擦力。污泥颗粒在斜板区沉降过程决定于混合液沿垂直向上方向的冲击力和污泥颗粒的重力之差。因此斜板倾角较大时，冲击力较大，不利于颗粒沉淀。絮凝体沿斜板的下滑过程则是自身重力、混合液的冲击力沿斜板方向的分力和摩擦力的共同作用结果。污泥絮体的粘性比颗粒状泥沙及其絮凝体大，加之斜板区的污泥浓度高，故斜板倾角较小时，其自身
13、重力沿斜板方向的分量不足以抵消其他力沿该方向的合力而不能向下滑动。3.2沉淀池的位置与外形在氧化沟内由于受到弯道的影响，在直流段两端及沟的内外侧和沟中间的混合液流速都是不均匀的，在不改变氧化沟的进水量及沉淀池表面负荷的前提下，将沉淀池置于氧化沟直流段的中后段外侧，污泥沉淀效果最好。氧化沟设置沉淀池后，该段过水断面的流态发生了变化，在沉淀池的底部前端混合液的流动发生了突缩变化，在沉淀池后端混合液的流动发生了突扩的变化。因此，在沉淀池前后的混合液流动紊动程度较大，属于紊流。另外，在沉淀池的底部混合液的过流断面变小、流速变大，如果过流断面过小，则此处混合液的流动成为急流。当急流不能维持在临界水深以下
14、时，则混合液在流过沉淀池的底部后，便向超过临界水深的缓流进行突变，将产生水跃。此外，水头损失与速度有关，当急流的速度大于缓流的速度而底坡不足以克服急流的磨擦损失时，急流也将以水跃的形式转变为缓流。因此，为了减小突缩和突扩形成沟内旋涡区和影响污泥沉降，将沉淀池的迎水面挡板制成船头型，缩小沉淀池的外宽，使氧化沟内的混合液能同时从沉淀池的底部和侧面流动。另外在生产应用中，将氧化沟的横断面在沉淀区一段加宽或加深也是一种可取方案。在实际应用中，氧化沟的结构通常根据场地、曝气设备等条件来确定。对于氧化沟内合建的沉淀池而言，其长宽在氧化沟限定的范围内。由于受到弯道的影响，在沟直流段两端及沟的内、外侧及沟中间
15、的混合液流速都是不均匀的，因此沉淀池的长与宽是决定沉淀池下部的压力分布是否均匀的主要因素之一。在不改变氧化沟的进水量及沉淀池表面负荷的前提下，试验中将沉淀池长宽比L/B对出水SS值的影响进行了考察，结果如图4所示。从图4中可以看出，当1.5L/B4.0时，沉淀池的沉淀效果较好；而当L/B4.0或L/B1.0时，沉淀效果较差。最佳长宽比为1.54.0。分析其原因：当长宽比值较小时，沉淀池内在宽度方向上和在氧化沟沟宽方向上流速的分布是不均匀的，因而出水水质受到一定的影响。当长宽比值较大时，虽然宽度方向上影响小，但在池长方向上受到的影响增大，因而出水水质还是受到一定的影响。3.3污泥浓度与污泥龄由于
16、污泥的沉速随悬浮固体浓度MLSS的增加而减小，因此在相同SVI、相同表面负荷率的条件下，MLSS越高则出水SS越高。为维持一定的出水水质，随着MLSS的增加应相应降低表面负荷率。污泥龄是决定污泥沉降性能的重要因素。污泥龄过短，细菌处于对数增长期，能量较高，不易沉降；而污泥龄过长，污泥容易微细化，因此应根据试验选择合适的污泥龄。试验中将污泥龄控制在1030 d。4结论从以上斜板沉淀池在一体化氧化沟中的固液分离效果和内部混合液的流态试验，可得出以下结论：与氧化沟合建的斜板沉淀池效率比一般二沉池高，水力停留时间30 min，出水SS值38 mg/L。斜板下部设有特殊的过渡区，具有良好的消能和调整流态
17、的作用，可使斜板沉淀区的流态快速从紊流转变为层流，达到最佳沉淀效果，沉降过程不受沟内主流的影响。斜板间的固液分离过程是自由沉淀、絮凝沉淀、污泥悬浮层的过滤和捕获以及污泥层下滑过程的共同作用。影响沉淀效果的因素有斜板倾斜角度、沉淀池的位置与外形、污泥浓度和污泥龄。参考文献：1J X Liu,J W van Groenestijn,H J Doddema,et al.Influence of the aeration brush on nitrogen removal in the oxidation ditchJ.European Water Pollution Control,1996，6(4
18、)：25-30.2刘俊新，王宝贞，J W van Groenestijn，et al.采用氧化沟从城市污水中去除氮和磷的研究J.哈尔滨建筑大学学报,1997，30(5):36-40.3邓荣森，谭显春，焦斌权.一体化氧化沟的生物除磷试验研究J.给水排水，2000，26(1)：14-17.4杨宝林.有发展前途的氧化沟技术J.给水排水，1990，16(1)：38-44.5邓荣森，刘保疆，王涛，等.一体化氧化沟技术的发展J.中国给水排水，1998，14(1)：42-44.6严煦世.水和废水技术研究M.北京：中国建筑工业出版社，1992.7K Krogh Andersen.Secondary sedim
19、entation of activated sludge by a lamella separator placed in an oxidation ditchJ.European Water Pollution Control,1996，6(4)：37-44./Porganization system and working mode, the selection of a number of municipal strengthening group to build innovation and strengthen the organization of the basic level
20、 organizations advanced model.(seven) the manual work of the Communist Youth League Organization published and League branch of manual work, to promote the use of two manuals in the citys organizations at various levels. The county committee, directly under the group (work) is under the jurisdiction
21、 of grassroots League and group (total) using branch ratio shall not be less than 70%.Three, to further strengthen the groups leadership and team building(a) to strengthen the leagues leadership at all levels of construction. Continue to do a good job of municipal Party Committee Organization Depart
22、ment on the strengthening of the Communist Youth League cadres management opinions implementation. To promote the group counties (autonomous counties, cities) Commission and city directly under the group (workers) appointed to carry out the Five team building activities. Improve the League Associati
23、on Department working mechanism. Conscientiously fulfill the duties of CO, combined with the city group directly under (the) Committee of the general election and the adjustment, actively jointly with the unit where the party organization department good group leadership selection with the work. Do
24、a good job in municipal Party committee assistant committee leadership and leading cadres of the annual assessment work, adhere to and improve the assistant secretary of the Communist Youth League talk system group To weave individual conversation and collective conversation, to strengthen the commi
25、ttees of all levels, the Standing Committee of the Standing Committee, the establishment of a sound system of central group learning, the system of investigation and study, the system of important issues and the reporting system.(two) to strengthen the work of education and training of cadres to con
26、scientiously implement the Central Committee. On the implementation of grassroots cadres training project and opinions on carrying out the mission municipal CYL Cadres training project implementation opinions, full implementation of the project of the City Youth League cadres training education. Foc
27、us on the county grassroots cadres and workers focused on training, the new school system vocational training League cadres, for the Municipal Organization Department jointly held the third session of the Communist Youth League system training cadres in party. Focusing on the construction of new soc
28、ialist countryside, strengthening village cadres and rural construction team group member of the young team, the county organizations at various levels throughout the year is expected to train 100 00 rural grassroots cadres, plans to train 1000 village secretary of the village Party branch.(three) a
29、ctively promote grassroots cadres election work. Under the unified leadership of the party organization, to strengthen grassroots organizations direct work, standardize the election work rules and procedures, in the designated candidate, open competition to democratically elected branch secretary at
30、 the same time, actively and steadily the development of Township, streets and other grassroots organizations in the direct election of the pilot work, on the basis of summarizing the experience and gradually expand the scope of the pilot, and gradually formed a set of measures and cadres election s
31、ystem.(four) to strengthen the cadres testing exercise. To study the development of XX city from 2006 to 2008 cadres testing exercise planning. To select outstanding cadres to the central mission in Beijing, Shanghai, Guangzhou and other central organs and sending work in developed areas. With the C
32、entral Committee the implementation of the western region and ethnic minorities cadres training plan . To carry out the eighth batch of municipal organs attachment cadre management, selection, training work. The outstanding cadres to start the National Development Bank XX branch testing exercise.(fi
33、ve) to strengthen the group construction. The main position to play the role of Youth League cadre education and training as the city, in accordance with the requirements of post training, further curriculum scientifically and rationally, adopt arrangement menu course, basic theory includes group wo
34、rk, focus, hot and difficult issues, to enhance the content and practice; to strengthen the construction of teaching staff, the integration of teachers, establish a quality teacher training team, establish and implement course evaluation system; take delivery of training to the countryside, on-site
35、training, and increase the rural grassroots cadres training efforts.Four, efforts to strengthen the work of young talent(a) to tenth XX young 54 medal in recognition of the publicity, and actively explore the XX youth service. 54 Medal of institutionalization, standardization and socialization mecha
36、nism. Give full play to the XX award in recognition of 54 youth medal Association, Youth Award winner in the 54 chapter, investigation activities. Who won the Youth Service medal, dedication to the society to create conditions, build the stage. During the 54, named in recognition of the tenth XX you
37、ng 54 medal. The association of XX editing of young talent , the exchange of information and communication platform for the XX of outstanding young talents.(two) the establishment of municipal Party committee of young talent information database. In accordance with the feasible, effective, classific
38、ation management, implement step by step principle, the establishment of municipal Party committee of youth talent database; guiding organizations at various levels generally established the young talent database, construction of city, county (directly under the Communist Youth League), grassroots o
39、rganizations three young talent information database the relevant information collection system, and gradually establish the citys young people, the Communist Youth League youth talent information network, provide information platform for young talent resource development.Five, take effective measur
40、es to strengthen the mission management(a) to strengthen the mission management work. Strengthen the dues collection and management, continue to adhere to the dues collection regularly reporting system, the annual comprehensive award in recognition of the tour and the tour one vote veto system audit
41、 system. Do statistical work in the group. The group service award in recognition of the advanced units, standardization, promoting group management work institutionalized.(two) to strengthen the organization of research and information exchange efforts. Grassroots carry out research, efforts to for
42、m a number of theoretical results. Make full use of the network carrier, to explore the establishment of electronic group service system, promote the work of Communist Youth League information.Attachment 4:XX municipal Party Committee Propaganda Department of the Communist Youth League work pointsIn
43、 2006, the Communist Youth League propaganda ideological work XX to Deng Xiaoping theory and the important thought of Three Represents as guidance, study and implement the partys sixteen and the spirit of the the fifth Plenary Session of the 16th CPC Central Committee implementation of the eight ple
44、nary session of the two committee, the citys cultural work conference, the Propaganda Department of the meeting and the the fourth Plenary Session of the 15th CPC Central Committee permanent mission spirit, closely around 11th Five-Year XX the goal of full implementation of Scientific Outlook on Dev
45、elopment, emancipating the mind, seeking truth from facts, keep pace with the times, close to reality, close to life, close to the young, persevere grasp orientation, grasping deepening, grasping construction innovation, further improve the groups propaganda and ideological work ability, unity To gu
46、ide the majority of members of the youth to achieve the 11th Five-Year planning tasks, the overall construction of a well-off society, building a socialist harmonious society to make new contributions.One, adhere to the Three Represents important thought and Scientific Outlook on Development educati
47、on to guide the youth, to further strengthen the ideological and political education of youth(a) armed with youth science theory. Unremittingly with Deng Xiaoping theory and the important thought of Three Represents armed members of youth education, to promote the study and implement to expand the d
48、epth and breadth. To study and implement the important thought of Three Represents with the establishment and implementation of Scientific Outlook on Development combine with the implementation of the requirements of constructing socialist harmonious society with Scientific Outlook on Development, carry out education as an important part of th