【作者】 曹贵华；

【导师】 王淑莹；

【作者基本信息】 北京工业大学 ， 环境工程， 2013， 博士

【摘要】 截止2011年全国污水处理厂中氧化沟系列的工艺占28.6%，传统连续流缺氧/好氧(A/O)工艺、厌氧/缺氧/好氧(A2/O)工艺系列占27.1%，续批式反应器(SBR)系列占16.5%，传统活性污泥工艺系列占27.8%。上述工艺由于存在单一污泥生长系统所固有的弊端，导致我国90%以上的污水处理厂不能实现稳定GB18918-2002一级A排放标准；尤其是低浓度、低COD/TN(C/N)废水更成为污水处理厂出水达标排放的一个“瓶颈”。如何合理地利用废水中的有机碳源以提高氮磷去除效率成为传统生物脱氮除磷技术出水达标排放的关键，同时可有效遏制缓流水体富营养化的进一步恶化。连续流分段进水工艺由于具有污泥浓度高、水力停留时间短、碳源利用率高、氮磷去除稳定高效、节省内回流等特点被国内外广泛研究、应用。因此，分段进水技术可为低浓度、低C/N废水处理提供一条达一级A标准的新途径。目前对分段进水工艺的研究主要基于实验室模拟废水以及较高浓度、较高C/N城市生活污水两个方面，国内外并未见任何有关利用分段进水技术处理低浓度、低C/N实际市政废水研究与应用的报道。为了推动分段进水工艺更广泛的应用，以及为我国南方低浓度、低C/N污水处理厂实际运行提供科学的指导，本研究开发了一套改良A2/O分段进水脱氮除磷新工艺。利用江苏省扬州市江都清源污水处理厂(40000m3.d-1)旋流式沉砂池出水作为研究对象，实验原污水平均COD、氨氮、总氮、总磷、COD/TN和COD/TP分别为146mg.L-1、30.8mg.L-1、31.4mg.L-1、2.9mg.L-1、4.77和52.8；在稳态进水和非稳态正弦波进水两种情况下，考察工艺脱氮除磷性能的影响因素以及优化运行策略：①稳态进水时，研究了工艺的最佳进水流量分配比、体积比、水力停留时间(HRT)、溶解氧(DO)的优化与运行策略，并且对强化系统的同步硝化反硝化(SND)效果以及如何实现短程硝化反硝化策略进行系统讨论；②非稳态正弦波进水时，研究了不同振幅对工艺污染物去除与出水变化规律的影响以及好氧段合理的DO控制范围，同时研究了恒曝气量和周期性变曝气量两种DO控制模式的优化策略，可为本工艺的设计以及后续实际运行提供更科学的参考。（1）稳态进水时，通过优化系统控制参数以及对工况下污染物出水效果的比较，确定了工艺的不同运行模式：①单纯以活性污泥法实现脱氮除磷达一级A标准角度分析，获得系统最优且最经济的运行参数：进水流量分配比为20:35:35:10%、厌氧/缺氧/好氧体积比为4:8:10(每段缺氧/好氧体积比为1:1)、HRT为7h、SRT为15d、污泥回流比为75%、好氧段DO控制范围为0.8-1.2mg.L-1，平均出水COD、氨氮、总氮、总磷浓度分别为27.43mg.L-1、1.57mg.L-1、14.3mg.L-1、0.25mg.L-1，并且原水COD绝大部分作为厌氧释磷和反硝化脱氮所需碳源，系统对碳源有效利用率达70%以上；另外，通过控制好氧段DO为1.0-1.5mg.L-1、并在好氧段投加悬浮填料的策略可以将工艺的HRT进一步缩短至6h，平均出水COD、氨氮、总氮、总磷浓度分别为25.92mg.L-1、1.98mg.L-1、14.5mg.L-1、0.47mg.L-1，并且该运行控制条件下可强化系统中SND效果同时降低对碳源的需求。②从活性污泥法结合化学法实现出水达一级A标准角度确定工艺的最佳运行参数如下：进水流量分配比为20:35:35:10%、厌氧/缺氧/好氧体积比为5:9:8(每段缺氧/好氧体积比为2:1)、HRT为7h、SRT为15d、污泥回流比为75%、好氧段DO控制范围为0.3-0.5mg.L-1，出水COD、氨氮、总氮和总磷分别为28mg.L-1、0.33mg.L-1、8.69mg.L-1和0.65mg.L-1。其中系统中氮去除主要通过短程硝化反硝化实现，亚硝化率达到58%，较低的DO和较短的好氧段HRT是分段进水工艺实现短程硝化反硝化的限制性因素；但总磷还需通过化学法进行深度去除。该运行条件的优势在于适用于低C/N废水并且大大节约曝气能耗，主要劣势在于实现短程硝化反硝化并大量富集AOB的控制条件相当严格且所需周期较长。（2）非稳态进水时，考察非稳态正弦波进水不同振幅对污染物去除的变化规律以及相应好氧段DO的控制策略，结果表明：①进水流量分配比为20:35:35:10%、稳态进水时HRT为8.7h的条件下，非稳态正弦波进水振幅分别为±25%、±50%、±75%时，对COD去除影响不大，但出水氨氮、总氮和总磷浓度逐步增加；不同振幅条件下出水COD浓度均以分段函数形式变化，出水氨氮、总氮和总磷均以类似正弦曲线波动；当进水出现峰谷值时，三个工况出水氨氮的峰谷值都分别延后2h、3h、5h，出水硝态氮的峰谷值分别都延后8h、9h、11h，出水总氮的峰谷值分别延后8h、9h、5h，出水TP的峰谷值分别延后4h、3h和2h。②周期性变曝气量和恒曝气量的两种运行控制模式，对COD和TP去除影响不显著，但是周期性变曝气量有利于提高对氨氮和TN的去除率；相对于恒曝气量，在进水波峰和波谷时周期性变曝气量的进水碳源有效利用率均提高。③当恒定曝气量时，正弦波动振幅为±25%，控制平衡位置初始DO浓度为2mg.L-1，出水均可达一级A排放标准；当周期性变曝气量时，正弦波动振幅可提高至±50%，控制DO浓度为1-3mg.L-1，出水均可达一级A排放标准，并且相比于恒曝气量可节省9.2%的曝气能耗。更多还原

【Abstract】 According to historical records, until2011, the national Wastewater TreatmentPlants(WWTP) were mainly consists of four types of biological nutrient removaltechnology: the oxidation ditch process(28.6%), the traditional A/O process or A2/Oprocess(27.1%), the SBR process(16.5%) and conventional activated sludge process(27.8%). However, the above processes due to the presence of the drawbacks inherentin a single sludge growth system, resulting in more than90%of WWTP could notachieve first level A discharge standards in China(GB18918-2002). Especially for theweak wastewater with low C/N, which was considered to be a "bottleneck" of WWTP,and it was difficult for the conventional biological treatment processes to achieveefficient and stable removal of nitrogen and phosphorus. Therefor, it is very importantfor traditional BNR that how to use the organic carbon reasonably in order toimprove the efficiency of nitrogen and phosphorus removal, and which couldeffectively curb the further deterioration of the slow-flow water eutrophication.The continuous flow step-feed technology had been extensively studied andapplied at home and abroad because of higher mixed liquor suspended solids(MLSS),shorter hydraulic retention time(HRT), higher utilization of carbon sources, nitrogenand phosphorus removal stable and efficient, saving internal reflux et al. Therefore,the step-feed technology can provide a new way up to first level A discharge standardsfor weak wastewater with low C/N. But so far, the step-feed technology was studiedbased primarily on two aspects: one was the laboratory simulated wastewater, theother was the higher municipal sewage with higher C/N, so there is not any researchor application reports about using step-feed process to treat weak actual municipalwastewater with low C/N at home and abroad.In order to improve the development and the wider application of step-feedprocess，and provide scientific reference for the operation of sewage treatment planttreating weak wastewater(COD≤200mg.L-1,NH4+-N≤40mg.L-1) with low influent C/N,a pilot modified Anaerobic/Anoxic/Oxic(A2/O) step-feed process was applied forsimultaneous biological nitrogen(N) and phosphorus(P) removal. During theexperiment, the effluent of swirl grit tank as the research object from TianyuQingyuan Wastewater Treatment Plant(WWTP)(40,000m3.d-1) employing the OrbalOxidation Ditch process (OD) in Yang ZhouCity, Jiangsu Province, China. And the influent COD, NH4+-N, TN, TP, COD/TN and COD/TP were146mg.L-1,30.8mg.L-1,31.4mg.L-1,2.9mg.L-1,4.77and52.8, respectively. Under steady-state andunsteady-state sinusoidal influent conditions, and the different influence factorsaffecting denitrification and phosphorus removal performance and optimal operationstrategies were investigated. In the case of steady-state influent, this paper haddiscussed the optimization and operating strategy of different influent flowdistribution ratio, volume ratio, HRT and DO, and how to strengthen simultaneousnitrification and denitrification(SND) and nitritation-denitritation of the system to bestudied. In the case of unsteady-state sinusoidal influent, that the different amplitudesaffect pollutant removal efficiency and effluent variation as well as DO controloptimization strategy were closer to the actual operating conditions of sewagetreatment plant, which could provide scientific reference for the design and follow-upoperation. After these main elements of systems research into this subject, and thefollowing conclusions were obtained.（1）When the influent was in steady-state mode, this experiment had studiedand optimized operation control parameters, and the effluent effects of pollutants werecompared at different conditions. At last we identified several different operatingmodels of modified A2/O step-feed process:①Nitrogen and phosphorus removal only by activated sludge process andachieved first level A discharge standards in China(GB18918-2002), the optimum andmost economical operating parameters can be set as following: the inflow distributionratio was20:35:35:10%with HRT of7h and SRT of15d, the volume ratio ofanaerobic/anoxic/aerobic was4:8:10and the volume ratio of anoxic/oxic zone inevery step was1:1, sludge reflux ratio was75%, and DO concentration in every oxiczones were controlled between0.8mg.L-1to1.2mg.L-1; Under this condition, theaverage effluent of COD, ammonia nitrogen, total nitrogen, total phosphorus were27.43mg.L-1、1.57mg.L-1、14.3mg.L-1and0.25mg.L-1respectively, and the effluentconcentration was up to Grade A discharging standard of WWTP (GB18918-2002).The majority of COD in raw water was used as carbon source for anaerobicphosphorus release and denitrification, and more than70%of carbon sources wasutilized effectively. In addition, HRT could be reduced to6h when the DOconcentration in aerobic zones were controlled between1.0-1.5mg.L-1and addingsuspended carriers in aerobic zones, the effluent performance of COD, NH4+-N, TNand TP were25.92,1.98,14.5and0.47mg.L-1respectively; and with this operation control condition, SND performance could be enhanced while reducing the demandfor carbon sources.②The effluent achieved first level A discharge standards took advantage ofactivated sludge process combine with chemical method, and this study proposed theoptimum operating parameters: the inflow distribution ratio was20:35:35:10%withHRT of7h and SRT of15d, the volume ratio of anaerobic/anoxic/aerobic was5:9:8and the volume ratio of anoxic/oxic zone in every step was2:1, sludge reflux ratiowas75%, and DO concentration in every oxic zones were controlled between0.3mg.L-1to0.5mg.L-1; Under this condition, the average effluent of COD, ammonianitrogen, total nitrogen, total phosphorus were28mg.L-1、0.33mg.L-1、8.69mg.L-1and0.65mg.L-1respectively. Wherein the nitrogen removal in the system mainly throughnitritation-denitritation, but phosphorus removal needed further chemical method.And the control strategy and the limiting factors of nitritation and denitritation instep-feed system were studied that lower DO concentration and shorter HRT inaerobic zones were key factors for step-feed process to accumulate nitrite. Nitritationwas achieved through a combination of short aerobic hydraulic retention time(HRT=2.5h) and low dissolved oxygen (DO) levels (0.3-0.5mg.L-1). The nitriteaccumulation rate was about58%and ammonia removal efficiency was over95%. Atthe same, the advantages and disadvantages of this model were analyzed. Theadvantages of second operating model is very suitable for low C/N wastewater andgreatly reduce aeration energy consumption, but the main disadvantage is that toachieve nitritation and denitritation and enrich large amount of Ammonia-oxidizingbacteria(AOB), which need very strict controlled conditions and will take a long time.And it is a big challenge for the actual WWTP to operate.（2）When the influent was in unsteady-state mode, this paper had discussed therelationship between unsteady sinusoidal influent and pollutants removal, variation instep-feed process, and obtain the optimal DO control parameters in aerobic zones. Theresults were as follows:①Under the controlled condition: HRT was8.7h at unsteady influent equilibriumposition, influent flow distribution ratio was20:35:35:10%, and sludge reflux ratiowas75%. When Sinusoidal influent amplitude was increased from±25%to±75%,there was little effect on COD removal, but the effluent NH4+-N, TN and TPconcentration were gradually increased.②The amplitudes of Sinusoidal influent were±25%,±50%and±75%under two operation modes of periodic variable aeration and constant aeration, effluentpollutants showed the same variation respectively: the effluent COD exhibit avariation of piecewise function, but the effluent NH4+-N, TN and TP show withsinusoidal function. When influent at peaks and troughs, effluent NH4+-Nconcentration of three different influent amplitudes appeared the peaks and troughswere delayed2h,3h and5h, respectively; effluent NO3-were delayed8h,9h and11h,respectively; effluent TN were delayed8h,9h and5h, respectively; effluent TP weredelayed4h,3h and2h, respectively.③Two operation modes of periodic variable aeration and constant aeration, thathad no significantly impact on COD and TP remove, but periodic variable aerationwas conducive to improve ammonia and TN removal efficiency; and when influent atpeaks and troughs that influent carbon source effective utilization was increased undervariable aeration mode compared to the constant aeration mode.④From up to level A emission standard measured, when the system wasoperated with constant aeration mode, influent fluctuation amplitude only was±25%and DO concentration was controlled of2.0mg·L-1in aerobic zones at unsteadyinfluent equilibrium position, the effluent of COD、NH4+-N、TN and TP were21.82,0.59,11.87and0.26mg·L-1, respectively. However, when the system was operatedwith periodic variable aeration mode, influent fluctuation amplitude could beincreased to±50%, and the effluent of COD、NH4+-N、TN and TP were23.19、1.50、13.88and0.48mg.L-1, respectively; and compared to the constant aeration mode,periodic variable aeration mode could save9.2%aeration energy consumption.更多还原