【作者】 彭赵旭；

【导师】 彭永臻；

【作者基本信息】 哈尔滨工业大学 ， 市政工程， 2012， 博士

【摘要】 活性污泥法是目前我国应用最广泛的城市污水处理技术，其结构简单，运行管理方便，但是存在曝气能耗大的缺点，并且饱受污泥膨胀问题的困扰。污泥膨胀具有影响因素多、产生危害大、治理方法难、发生频率高等特点。为了更科学地对待污泥膨胀问题，本课题组在长期采用活性污泥法处理城市污水的过程中，总结生产实践经验，在国内外首次提出了“低溶解氧（DO）丝状菌污泥微膨胀节能理论和方法”。它的核心内容是人为地减少曝气量，调节活性污泥系统在低溶解氧环境下运行，引发丝状菌的适度增长，同时控制其膨胀程度不会影响到系统的正常运转。利用丝状菌具有比表面积大，抗低溶解氧和降解低浓度底物能力强的生理特点，在节能的基础上改善出水水质。为了更好地在生产实践中应用低DO丝状菌污泥微膨胀，采用小试SBR进行试验，通过调节不同的运行方式和反应条件，研究了低DO丝状菌污泥膨胀的引发、过度丝状菌膨胀的抑制以及微膨胀的稳定维持方法。系统地考察了低DO状态下，各种常见的环境因子和工艺参数对活性污泥法运行效果，尤其是污泥沉降性的影响。深入地了解活性污泥法的特性，通过对所得试验数据进行优化，建立了引发和抑制丝状菌生长的有效方法。并将所建立的控制方法分别在处理模拟生活污水和实际生活污水的SBR中进行了验证，同时考察了低DO丝状菌污泥微膨胀状态下的污染物去除特点。建立了丝状菌污泥微膨胀的引发方法。发现了在低DO下，污泥沉降性与有机负荷关系密切。没有前置缺氧段时，负荷在0.30⁰.35kgCOD·（kgMLSS·d）^-1仅靠维持低DO不会引起丝状菌增殖，小于0.25或大于0.40kgCOD·（kgMLSS·d）^-1才会引发丝状菌激增；有前置缺氧段时，负荷小于0.30kgCOD·（kgMLSS·d）^-1仅靠维持低DO不会引起丝状菌增殖，大于0.40kgCOD·（kgMLSS·d）^-1会引发丝状菌激增。通过优化，提出单级好氧方式运行，同时延长反应时间降负荷到0.25kgCOD·（kgMLSS·d）^-1是引发丝状菌增殖的最有效方法。建立了过度丝状菌膨胀的抑制方法。发现了单独提高DO或有机负荷等因素难以有效地抑制丝状菌生长，使用前置缺（厌）氧+好氧运行方式是改善沉降性的有效手段。对于缺氧选择器，良好的除磷性能是其有效抑制丝状菌生长的必要条件；在除磷良好且反硝化充分时，进水RBCOD: NO₃^--N比在33.00⁶6.00可以成功地抑制丝状菌生长，小于33.00或大于66.00时则会抑制失效。对于厌氧选择器，良好的除磷能力对于抑制丝状菌也非常重要。在PO₄^3-–P过量时，进水COD:PO₄^3-–P比对沉降性的改善速率没有影响。在沉降性恶化和改善过程中，污泥容积指数（SVI）在200mL·g^-1左右存在阈值效应，会在短期内骤变。发现了温度、pH和DO等环境因子以及SRT、MLSS和进水方式等工艺参数对活性污泥法运行效果、尤其是污泥沉降性的不同影响。短期变温不会改变污泥絮体中丝状菌的含量，污泥沉降性在降温时会因EPS大量分泌而恶化，在升温时会因絮体的疏松而恶化。生物硝化和除磷过程在小幅变温时波动不大，在温度大幅骤降时（22¹2°C），都会明显恶化；在温度大幅骤升时（12²2°C），除磷不受影响，硝化严重恶化。硝化、反硝化等许多生化反应都直接消耗或产生碱度，再加上水溶液中普遍存在多种离子对的电离平衡，使得活性污泥混合液有良好的调节pH能力。原水pH在6⁹变化时，污泥沉降性波动不大，沉后上清液在酸性环境下较浑浊，在碱性环境下十分清澈。DO的高低不是影响丝状菌生长的重要因素。污泥沉降性随着SRT的降低而改善。硝化速率、放磷量和吸磷量都随着SRT的降低而减小，而比硝化速率、比释磷速率和比吸磷速率都随着SRT的降低而增大。无论是不膨胀污泥还是膨胀污泥，当MLSS过低时污泥絮体都呈离散或半离散状态，沉速较快，泥水分界面模糊，沉后上清液浑浊。当MLSS升高时，各种污泥的沉速都会变慢，泥水分界面变得清晰。验证了由不同进水方式产生的贮存选择作用不能作为一条抑制丝状菌生长的普遍规律。通过联合运用试验前期建立的丝状菌污泥微膨胀的引发方法和过度丝状菌膨胀的抑制方法，分别在处理模拟生活污水和实际生活污水的SBR中实现了低DO丝状菌污泥微膨胀的长期稳定维持。当SVI在阈值附近时，虽然可以根据需要灵活地改变沉降性，但是活性污泥系统并不稳定。为了稳定地在SBR中维持微膨胀，建议在SVI处于250³00mL·g^-1时再调节运行方式控制污泥沉降性。活性污泥法在低DO下长期运行，有利于短程硝化和同步硝化反硝化（SND）的发生。发现了在每周期时间与进水水质不变时，缺（厌）氧时间与好氧时间的比值是决定SND率大小的重要因素。更多还原

【Abstract】 Activated sludge process is the most widely applied municipal wastewatertreatment technology. It owns the characteristics of simple configuration andconvenient management, but has the disadvantage of big aeration energyconsumption. What is more, it is suffered by sludge bulking seriously. Sludgebulking has the characteristics of many influence factors, huge damage, difficulttreatment, high occurrence frequency and so on. Our laboratory team had beentreating municipal wastewater by activated sludge process many years, in order totreat sludge bulking more scientifically,"The theory and technique of saving energyachieved by limited filamentous bulking under low dissolved oxygen （DO）" wasproposed firstly by our laboratory team through summarizing practical experiences.Its core content is adjusting the activated sludge system operate under low DOcondition through decreasing aeration rate artificialy. Filamentous bacterium will beproliferated by low DO, meanwhile, sludge bulking extent is prevented fromdamaging normal operation. On the basis of saving energy, effluent quality can beimproved through using the filamentous bacterial physiological characteristics suchas large specific surface area, strong low DO enduring ability and strongdecomposing low substrate ability.In order to apply the low DO limited filamentous sludge bulking in practicebetter, lab-scale sequencing batch reactor （SBR） was used through adjustingdifferent operation patterns and conditions. The approaches to induce limitedfilamentous bulking, inhibit excessive filamentous bulking and maintain low DOlimited filamentous bulking were all investigated. Under low DO condition, theinfluences of various normal environmental factors and process parameters onactivated sludge process operation effects, especially the sludge settleability, werealso investigated. Through optimizing the experimental datas, the characteristics ofactivated sludge process had been understood further, and the effective approachesto induce and inhibit filamentous bacterium proliferation were established. Finally,the established approaches to control sludge settleability had been verified in theSBR treating synthetic wastewater and real municipal wastewater, respectively.Meanwhile, the pollutants removal characteristics under low DO limited bulkingwere investigated.The approaches to induce limited filamentous bulking were established. It wasfound that sludge settleability and organic loading rate （OLR） had close relationship under low DO condition. When there was no pre-anoxic phase, filamentous bacteriacan not proliferate excessively by adjusting low DO alone when OLR was in therange of0.30⁰.35kgCOD·（kgMLSS·d）^-1, while it will proliferate excessivelywhen OLR was smaller than0.25or larger than0.40kgCOD·（kgMLSS·d）^-1. Whenthere was pre-anoxic phase, filamentous bacteria can not proliferate excessively byadjusting low DO alone when OLR was smaller than0.30kgCOD·（kgMLSS·d）^-1,while it will also proliferate excessively when OLR was larger than0.40kgCOD·（kgMLSS·d）^-1. After optimization, it was proposed the most effectiveapproach to induce filamentous bacteria proliferation was decreasing OLR under0.25kgCOD·（kgMLSS·d）^-1by prolonging aeration time without pre-anoxic phase.The approaches to inhibit excessive filamentous bulking was established. Itwas found increase DO or OLR alone was difficult to inhibit filamentous bacteria,while operate as anoxic（anaerobic）/aerobic was effective to improve sludgesettleability. For anoxic selector, excellent phosphorus removal ability is necessaryto inhibit filamentous bacteria effectively. When phosphorus removal performancewas well and the anoxic time was sufficient, filamentous bacteria can be inhibitedsuccessfully when influent RBCOD: NO₃^--N ratio was in the range of33.00⁶6.00,while it will lost when the ratio was smaller than33.00or larger than66.00. Foranaerobic selector, excellent phosphorus removal ability was also important toinhibit filamentous bacteria. When PO₄^3-–P was excessive, the influentCOD:PO₄^3-–P ratio had no impact on sludge settleability improvement rate. Duringsludge settleability deterioration or improvement processes, sludge volume index（SVI） existed a threshold effect around200mL·g^-1, where it will change sharply ina short time.It was found the environmental factors like temperature, pH, DO and theprocess parameters like sludge retention time （SRT）, mixed liquid suspended solids（MLSS）, feeding pattern had different impacts on activated sludge processoperation effect, especially the sludge settleability. Temperature variation in a shortterm had no impact on filamentous bacterial content. Sludge settleabilitydeteriorated by the excessive excreted extracellular polymeric substances （EPS）when temperature was decreased, while it will deteriorated by the looser flocsconfiguration when temperature was increased. Nitrification and phosphorusremoval processes fluctuated slightly when temperature varied smal. Theydeteriorated seriously when temperature decreased sharply （22¹2°C）. Whentemperature incresed sharply （12²2°C）, nitrification will deteriorated seriously,while phosphorus removal was not affected. Nitrification, denitrification and many other biochemical reactions can consume or produce alkalinity, with a lot of ionpairs existed ionization equation in the water solution, the activated sludge mixturehad excellent pH adjusting ability. When influent pH was in the range of6⁹, pHhad little influence on sludge settleabiliy. The supernatant was turbid under aciditycondition, while it was clear under alkaline condition. DO was not an importantfactor to influence filamentous bacterial proliferation. Sludge settleability improvedwith SRT deduction, nitrification rate, the amounts of PO₄^3-–P released and uptakendecreased with SRT deduction, while the specific nitrification rate, specific PO₄^3-–Preleasing rate and uptaken rate increased with SRT deduction. No matter non-bulking sludge or bulking sludge, when MLSS was too low the activated sludgewould have the characteristics like dispersed or semi-dispersed configuration, rapidsedimentation rate, fuzzy sludge-water interface, tuibid supernatant. When MLSSwas bigger, the sedimentation rate would decrease, and the sludge-water interfacebecome clear. It was verified the storage selection effect caused by different feedingpatterns can not be acceptted as a general law to inhibit filamentous bacterialproliferation.Through combined utilizing the approaches to induce or inhibit filamentousbacterial proliferation estabilished above, the low DO limited filamentous bulkinghad been firstly maintained steadily in SBR treating synthetic municipal wastewaterand real municipal wastewater, respectively. When SVI was close to the thresholdvalue, although sludge settleability could be changed easily, the activated sludgesystem was very unsteady. In order to maintain the limited filamentous bulkingsteadily, it was recommended operation patterns should be altered when SVI was inthe range of250³00mL·g^-1. Operating under low DO in a long term is benificalfor short-cut nitrification and simultaneous nitrification denitrification （SND） totake place. It was found when each cycle duration and influent quality wereconstant, the value of anoxic （anaerobic） time to aerobic time ratio was a determinefactor for SND ratio.更多还原