环境学院研究团队提出利用超声波技术实现处理废水脱氮过程控制的新方法
清华新闻网2月25日电 日前，清华大学环境学院博士后郑敏、汪诚文教授、刘艳臣副研究员和美国斯坦福大学高级研究员吴唯民等在国际环境科学与技术领域顶尖期刊《环境科学与技术》（Environmental Science and Technology）上发表了题为“Ultrasonic Treatment Enhanced Ammonia-oxidizing Bacterial (AOB) Activities for Nitritation Process”（超声波处理增强亚硝化工艺中氨氧化细菌（AOB）活性）的研究论文，首次提出一种利用超声波技术有效控制废水处理微生物群落组成从而实现高效、节能的短程硝化脱氮的新方法。
人类生活产生的污水含有大量的氮素污染物，排入水体可造成富营养化，因此除氮是废水处理过程中的重要环节。传统的废水生物脱氮是利用细菌先将水中的氨氮曝气氧化为亚硝酸盐，然后由另一类细菌将亚硝酸盐氧化为硝酸盐（全程硝化过程），最后在无氧条件下利用有机物将硝酸盐还原成氮气释放到大气（反硝化过程）。1975年Voet等学者提出了一种短程硝化—反硝化的工艺，即将氨氮氧化为亚硝酸盐（短程硝化），然后将亚硝酸盐还原为氮气。该方法较传统全程硝化脱氮方法可大大节省曝气所耗的能耗、节省反硝化所需碳源、减少污泥产量，缩短反应时间及减少相应反应器容积。近年来又开发了将半量氨氮曝气氧化为亚硝酸盐，再与另外半量氨氮反应生成氮气的厌氧氨氧化工艺，可进一步减少一半的曝气能耗。以上两种工艺，短程硝化是关键，但实施的难点是要控制废水处理的细菌仅将氧化氨氮至亚硝酸盐。迄今，国内外研究者一直在致力于寻找操作简便、具有大规模应用前景的短程硝化过程控制方法。
2011年，在环境学院攻读博士学位的郑敏在利用超声波技术进行污泥源头减量化的试验研究中发现，利用适宜的超声波条件处理活性污泥后的菌群可以在反应器内稳定地积累亚硝酸盐而使硝酸盐生成量大幅减小。此后，在导师汪诚文的指导下，郑敏开展了利用超声波控制细菌种群结构、获取高效稳定短程硝化的全面系统研究。本次发表的论文是其中的重要成果之一。该文章报道了研究组成功通过超声波的条件优化与控制，利用适当的超声波强度刺激短程硝化必需的好氧氨氧化细菌（Ammonia-oxidizing Bacteria，AOB）生长，同时抑制灭活产生硝酸盐的亚硝酸盐氧化细菌（Nitrite-oxidizing Bacteria，NOB），从而实现反应器的持续运行，并建立了评价超声波对不同细菌作用的动力学试验模型。此研究首次全面系统地证实了在超声波处理条件下，可以控制反应器的细菌种群、富集驯化出含高丰度AOB无NOB的微生物达到高效的短程硝化。该方法将为开发高效污水处理与污泥资源化组合新工艺提供一条全新思路。今后，研究人员将进一步探明系统控制的微生物生理学和生态学机理和实现从小型试验到生产示范过渡。
郑敏为论文第一作者，汪诚文为通讯作者。合作者中吴唯民参与试验设计和指导研究工作，刘艳臣参与了试验设计和微生物学的分析工作。
论文链接：http://pubs.acs.org/doi/abs/10.1021/acs.est.5b04178
Ultrasonic Treatment Enhanced Ammonia-Oxidizing Bacterial (AOB) Activity for Nitritation Process
Min Zheng†, Yan-Chen Liu*†‡, Jia Xinϕ, Hao Zuo†, Cheng-Wen Wang*†, and Wei-Min Wu§
† School of Environment, Tsinghua University, Beijing 100084, China
‡ State Key Joint Laboratory of Environment Simulation and Pollution Control, Beijing 100084, China
ϕ College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
§ Department of Civil & Environmental Engineering, the William & Cloy Codiga Resource Recovery Research Center, Center for Sustainable Development & Global Competitiveness, Stanford University, Stanford, California 94305, United States
Environ. Sci. Technol., 2016, 50 (2), pp 864–871
DOI: 10.1021/acs.est.5b04178
Publication Date (Web): December 17, 2015
Copyright © 2015 American Chemical Society
*(Y.-C.L.) E-mail: liuyc@mail.tsinghua.edu.cn., *(C.-W.W.) Phone: +86 10 6277 1551; fax: +86 10 6278 8148; e-mail:wangcw@tsinghua.edu.cn
Abstract
Oxidation of ammonia to nitrite rather than nitrate is critical for nitritation process for wastewater treatment. We proposed a promising approach by using controlled ultrasonic treatment to enhance the activity of ammonia-oxidizing bacteria (AOB) and suppress that of nitrite-oxidizing bacteria (NOB). Batch activity assays indicated that when ultrasound was applied, AOB activity reached a peak level and then declined but NOB activity deteriorated continuously as the power intensity of ultrasound increased. Kinetic analysis of relative microbial activity versus ultrasonic energy density was performed to investigate the effect of operational factors (power, sludge concentration, and aeration) on AOB and NOB activities and the test parameters were selected for reactor tests. Laboratory sequential batch reactor (SBR) was further used to test the ultrasonic stimulus with 8 h per day operational cycle and synthetic waste urine as influent. With specific ultrasonic energy density of 0.09 kJ/mg VSS and continuously fed influent containing above 200 mg NH3–N/L, high AOB reproductive activity was achieved and nearly complete conversion of ammonia-N to nitrite was maintained. Microbial structure analysis confirmed that the treatment changed community of AOB, NOB, and heterotrophs. Known AOB Nitrosomonasgenus remained at similar level in the biomass while typical NOB Nitrospira genus disappeared in the SBR under ultrasonic treatment and after the treatment was off for 30 days.
