【作者】 王波；

【导师】 王秀蘅；

【作者基本信息】 哈尔滨工业大学 ， 环境科学与工程， 2010， 硕士

【摘要】 由于低温环境对微生物的影响,我国北方寒冷地区城市污水的生物处理一直面临处理效果低、出水难以达标的困扰。膜生物反应器处理低温城市污水具有潜在优势,该技术已经在污水回用和难降解有机废水处理领域崭露头角,并在世界范围内许多实际工程中得到了成功的应用。考察膜生物反应器对低温污水的处理效果和研究其强化措施具有重要的意义。本实验采用一体式膜生物反应器（SMBR）对低温污水进行处理,研究了该反应器在低温条件下,超声波强化生物脱氮效果的最佳作用参数及在该参数强化下长期稳定运行的强化效果。并探讨了施加超声波后对膜污染现象的影响,重点研究了超声波强化的作用机理。实验采用自行设计的SMBR,有效容积为28L,实验用水为人工配制,水温控制为10±1℃,HRT为2.4h。启动期不进行超声波强化的结果表明,SMBR处理低温城市污水时启动期较长,为27d。低温对SMBR中COD总去除率的影响不大,COD总去除率仍能维持在90%以上,而对NH₃-N去除的影响较大。低温条件下SMBR启动初期对NH₃-N的处理效果很差,随着硝化细菌对环境的逐渐适应, NH₃-N去除率才开始逐渐上升。在第27d COD去除率达到稳定状态时,NH₃-N的生物去除率和总去除率分别达到59.7%和64.9%。但此时NH₃-N去除效果并没有达到稳态,去除率还继续上升,第31天达到69.6%。此后,稳定在65%到70%之间。引入低强度超声波强化SMBR运行后,在短HRT条件下对提高低温城市污水处理效果有明显作用。在超声波辐照后的48h内每间隔2h到6h取样,考察不同超声波参数组合对NH₃-N降解的强化作用。结果表明,功率密度为0.21W/L、辐照时间为20min及0.28W/L、15min,能量消耗为4.2W·min /L的超声波为最佳参数。结果表明,在此超声波参数作用下, NH₃-N生物去除率提高百分比约为32%。出水中的含氮化合物主要是NH₃-N,NO2-N和NO3-N含量很低。辐照间隔缩短为原来的一半时,膜清洗周期延长了两天。随着系统运行时间的延长,反应器中EPS的总量升高,说明随着系统的长期运行,膜污染程度加重。EPS中的主要成分为蛋白质,而且系统运行的各阶段多糖含量没有明显变化,因此可以认为蛋白质是引起膜污染加剧的主要原因。引入超声波对污泥强化后,有效预防了污泥膨胀的问题。最后,实验对超声波强化低温城市污水生物处理的作用机理进行了探讨。超声波辐照可以改变细胞膜通透性,随着超声波功率密度的增加细胞膜通透性逐渐增加,从而加快细胞内外物质交换、传输和可逆渗透。超声波对细胞膜通透性的改变作用比脱氢酶活性提高率能更好地解释超声波参数选择与NH₃-N去除率提高比的关系。功率密度为0.14W/L和0.21W/L时,随着辐照时间和功率密度的增大,细胞膜通透性也提高。当超声波输入能量过大时,细胞膜上产生的孔太大而使得细胞不能完成自我修复,发生不可逆细胞膜通透性改变,从而影响到微生物细胞代谢功能的提高。更多还原

【Abstract】 As the impact of low temperature, the biological treatment of urban sewage infrigid area has been facing with poor removal efficiency. MBR has the potentialadvantages of treating low temperature urban sewage. It has been used in the waterreuse and wastewater treatment, and many practical projects in the world have beensuccessfully applied in. So investigating the performance of submerged MBRtreating low temperature urban sewage and developing measures to strengthen itseffect are of great significance.In the study, the wastewater at low temperature was treated by an submergedmembrane bioreactor （SMBR）. The best ultrasound-enhanced indexes and theperformance of the reactor in removing nitrogen after ultrasound radiated werestudied. And membrane fouling with ultrasound radiated was also investigated.Furthermore, the mechanism of ultrasound enhancing the biological nitrogenremoval at low temperature was mainly investigated.A lab-scale SMBR with effective volume of 28L operated at 10±1℃, andcontrolled HRT at 2.4h. The sewage was prepared artificially. The effectiveness ofSMBR treating low temperature urban sewage in start-up period was studied. Theresults showed that in treating low temperature urban sewage, the start-up period ofSMBR was as long as 27d.Low temperature had little effect on total COD removalrate, which can be maintained over 90%, while it had larger effect on NH₃-N removal.In the prophase of start-up period, NH₃-N had very low removal rate. It didn’t raiseup to the perfect level until nitro-bacteria started adapting the low temperature. Whenthe COD removal rate reached its steady state, NH₃-N biological removal and totalremoval rates were 59.7% and 64.9%, but they were still unstable. The biologicalremoval rate was 69.6%, stable at 65% to 70%.The ultrasound can improve the performance of SMBR treating low temperaturesewage at short HRT. Samples Irradiated by ultrasound within 48h were examinedevery 2 to 6 hours to study the strengthening effects on NH₃-N degradation underdifferent combinations of ultrasonic parameters. Results showed that ultrasound withpower densities of 0.21W/L at irradiation time of 20min and 0.28W/L at 15min,energy consumptions of 4.2W·min/L, were the optimum parameters. Under which,the improvement of NH₃-N biological removal efficiency was up to 32%. Nitrogencompounds in the effluent were mainly NH₃-N. NO2-N and NO3-N contents were verylow. The membrane cleaning cycle extended 2d when ultrasound radiation time wasreduced by half, meaning ultrasound can reduce membrane fouling at low temperature. With the system running, the total amount of EPS increased. And themain component was protein, which means protein was the reason of membranefouling. After ultrasound radiation, Sludge filamentous bulking didn’t happen during theexperiment.At last, the mechanism of ultrasound enhancing the biological nitrogen removalwas investigated. Changes of cell membrane permeability can explain therelationship between ultrasound parameters and increased NH₃-N removal ratesbetter than dehydrogenase activity increasing. When the power densities were0.14W/L and 0.21W /L, cell membrane permeability increased with the extension ofirradiation time and the increase of power densities. But if energy input wasexcessive, the membrane holes became so large that cells were unable to completeself-healing, changing cell membrane permeability irreversibly, and consequentlyinhibiting the improvement of metabolism.更多还原