【作者】 王锋；

【导师】 刘勇弟；

【作者基本信息】 华东理工大学 ， 环境科学与工程， 2013， 博士

【摘要】 针对目前日益严重的硝酸盐污染问题和传统反硝化工艺存在的有机物残留问题,本文以高效脱氮并深度去除反硝化残留有机物为主要研究目标,分别研究了三种各具特色的的反硝化技术:1、颗粒污泥反硝化技术基于厌氧颗粒污泥已经在全球范围内大量使用,本文提出先采用颗粒污泥床去除硝酸盐,再通过生物接触氧化、混凝沉淀技术去除反硝化残留有机物的构思。关于这一构思,反硝化颗粒污泥的成功培养和稳定运行是关键,本文对此进行了系统研究。在上流式污泥床(USB)反应器中接种絮状活性污泥,以甲醇为碳源在40天左右培养出良好的反硝化颗粒污泥。系统显示高效的脱氮能力,当硝酸盐负荷为 5.0 gNO3-N·L-1·d-1,进水 N03-N 为 100 mg·L-1,C/N 为 4.0 时,硝酸盐、COD去除率分别为99%和91%左右。针对反硝化颗粒污泥培养过程中污泥上浮、沟流问题,分别采用改良种污泥和控制反硝化菌增殖速率等手段促进良好反硝化颗粒污泥的形成。研究表明,①接种污泥宜选择老化、稳定的活性污泥。②培养初期,污泥负荷应控制在0.15 gNO3-N·gVSS-1·d-1以内。③细颗粒污泥出现后,污泥床易出现沟流、短路现象。可以通过间歇性鼓气的方法提高污泥床的混合效果。④细颗粒污泥出现后,提高负荷可以加快颗粒污泥的形成,但污泥负荷应低于0.25 gNO3-N·gVSS-1·d-1,这样有利于形成密实、稳定的反硝化颗粒污泥。针对反硝化颗粒污泥在高负荷下出现的污泥粘连、易上浮等不稳定现象,分别采取减小颗粒粒径、提高污泥比重、减弱污泥对气泡的粘附作用、降低进水温度、改变碳源为葡萄糖和降低负荷等6种方法进行调控。研究表明,颗粒污泥不稳定的根本原因是颗粒表面反硝化菌增殖过快,降低微生物的生长速率有助于提高颗粒污泥的稳定性。2、一体化脱氮-除碳(DN-RC)工艺提出一种“硝酸盐反硝化”与“反硝化残留有机物去除”在同一污泥系统内完成的新工艺。系统由脱氮池(DN池)、除碳池(RC池)和沉淀池组成。研究发现,该工艺具有良好的处理性能,当DN池负荷为3.0 gNO3-N·L-1·d-1,进水NO3-N为100 mg·L-1,C/N为4.0时,硝酸盐去除率可达99%以上,出水DOC小于 4.0mg·L-1。对DN-RC工艺性能良好的机理进行研究。系统污泥浓度高达7.0-8.0 gVSS·L-1,生物相丰富,存在杆状菌、丝状菌、原生动物及后生动物等多种微生物。DN池实现高效反硝化,污泥反硝化活性高达25.2mgNO3-N·gVSS-1·h-1,是实际装置去除速率(15.5mgNO3-N·gVSS-1·h-1)的1.6倍。投加碳源在DN池彻底利用,残留有机物主要为大分子SMP,之后在RC池被进一步去除。3、同一曝气池内脱氮除碳工艺(好氧反硝化工艺)通过建立好氧反硝化试验装置,对曝气条件下的反硝化行为进行测试。结果显示,在曝气条件下反硝化可以高效进行,当曝气量为400 mL·min-1,进水负荷为0.5 gNO3-N·L-1·d-1,进水N03-N为50 mg·L-1,C/N为7.0时,硝酸盐去除率达到99%以上,出水COD小于10.0 mg·L-1。分别考察了曝气量、碳源种类对好氧反硝化的影响。研究表明好氧反硝化是反硝化菌和碳氧化菌对COD的速率竞争过程,降低曝气量、选择反硝化速率较快的碳源有助于反硝化对COD的竞争,有利于好氧反硝化的发生。研究结果对现有污水厂的升级改造具有技术指导意义。本研究弥补了目前反硝化研究未涉及处理残留有机物的不足,对硝酸盐污染的治理具有支持和推动作用。更多还原

【Abstract】 According to the serious nitrate pollution situation and the residual organics problems of the traditional denitrifying processes,this paper proposed three different denitrifying processes with the main objective to deeply removing both nitrate and the residual organics from denitrification.1.Denitrifying granular sludge technologySince anaerobic granular sludge has been extensively applied worldwide,this paper proposed that nitrate was firstly treated by granular sludge bed,and then the residual orgaincs from denitrification were further removed by biological contact oxidation and coagulation sediment process.The keypoint of this idea is the sucessful startup and steady operation of denitrifying granular sludge,which were systemically studied in this paper.Well-formed denitrifying granular sludge was obtained within 40 days with methanol as carbon source and flocculent sludge as seed sludge in upflow sludge blanket(USB)reactor.This system showed a good denitrification performance that nitrate and COD removal efficiency were 99%and 91%,respectively when nitrate loading rate(NLR)was 5.0 gNO3-N·L-1·d-1 and influent NO3-N was 100 mg-L-1 with a C/N(COD/NO3-N)at 4.0.As to the sludge floating and channeling phenomena during the cultivation,the measures that improving the seed sludge and controlling the sludge growth rate were adopted respectively to accelerate the formation of good granular sludge.It concluded that ① the stable and aging sludge was better as inoculum.② the sludge loading rate should be within 0.15 gNO3-N gVSS-1·d-1 at the beginning of cultivation.③ when fine granules formed,channeling and dead space were usually observed in the sludge bed,so interval air-blowing was advised to improve the mixing effect;④ increasing loading rate can accelerate the formation of granular sludge,while the sludge loading rate should be less than 0.25 gNO3-N·gVSS-1·d-1 until dense,mature granular sludge appeared.According to the unstable phenomena of denitrifying granular sludge under high NLRs,the six measures that reducing the size of the granules,increasing the density of the granules,weakening the adhesion effect of sludge to bubbles,reducing temperature,replacing methanol with glucose as carbon source,and decreasing NLR were conducted respectively to improve the stability of the reactor.It indicated that too rapid growth of biomass was the root cause of the flotation of denitrifying granules,and decreasing the growth rate of biomass was able to improve the stability of the denitrifying granules.2.Dentrification-Removing carbon(DN-RC)processIn this paper,an integrated process,called DN-RC process,was proposed through which both nitrate and the residual organics from denitrification can be removed in one sludge system,which consisted of a denitrification tank(DN tank),a removing carbon tank(RC tank),and a sedimentation tank.This process exhibited a good performance that nitrate removal efficiency reached approximately 99%at a high nitrate loading rate of DN tank of 3.0 gNO3-N·L-1·d-1 and a low C/N of 4.0,respectively.The mechanism for the good performance of DN-RC process was studied.The system had a high sludge concentration of 7.0-8.0 gVSS·L-1,and a microbial diversity with rod-shaped bacteria,filamentous bacteria,protozoon,and metazoan,etc.The denitrifying activity remained 25.2 mgNO3-N·gVSS-1·h-1 during anoxic/aerobic alteration,which was almost 1.6 times of the actual removal rate.The added carbon source in DN tank was thoroughly utilized and the residual organics were mainly soluble microbial products(SMP)which were then deeply reduced in RC tank.3.Simultaneous dentrification and removing carbon in one aerobic tank(aerobic denitrification process)The denitrification behavior was investigated by a laboratory-scale aerobic denitrification reactor.The results suggested that nitrate can be removed effectively under aerobic conditions.When air rate was 400 mL·min-1,NLR was 0.5 gN03-N·L-1·d-1,and influent NO3-N was 50 mg·L-1 with a C/N of 7.0,nitrate removal efficiency was more than 99%with an effluent COD less than 10.0 mg·L-1.The effects of air rate and carbon type on aerobic denitrifying process were analysed respectively.It indicated that aerobic denitrifying process was a COD competition process between denitrifying bacteria and carbon oxidizing bacteria.Reducing air rate or selecting easily degradable carbon sources was useful to increase the competitiveness of denitrifying bacteria and was helpful for the aerobic denitrification.The results provide directive significance for improving the nitrogen removal efficiency of the exsiting wastewater treatment plants(WWTP).This study made up the gap of the current denitrifying researches that their effluents always contained a certain amount of the residual organics,and could support and promote the nitrate wastewater treatment.更多还原