環(huán)境學院研究團隊提出利用超聲波技術實現(xiàn)處理廢水脫氮過程控制的新方法
清華新聞網2月25日電 日前，清華大學環(huán)境學院博士后鄭敏、汪誠文教授、劉艷臣副研究員和美國斯坦福大學高級研究員吳唯民等在國際環(huán)境科學與技術領域頂尖期刊《環(huán)境科學與技術》（Environmental Science and Technology）上發(fā)表了題為“Ultrasonic Treatment Enhanced Ammonia-oxidizing Bacterial (AOB) Activities for Nitritation Process”（超聲波處理增強亞硝化工藝中氨氧化細菌（AOB）活性）的研究論文，首次提出一種利用超聲波技術有效控制廢水處理微生物群落組成從而實現(xiàn)高效、節(jié)能的短程硝化脫氮的新方法。
人類生活產生的污水含有大量的氮素污染物，排入水體可造成富營養(yǎng)化，因此除氮是廢水處理過程中的重要環(huán)節(jié)。傳統(tǒng)的廢水生物脫氮是利用細菌先將水中的氨氮曝氣氧化為亞硝酸鹽，然后由另一類細菌將亞硝酸鹽氧化為硝酸鹽（全程硝化過程），最后在無氧條件下利用有機物將硝酸鹽還原成氮氣釋放到大氣（反硝化過程）。1975年Voet等學者提出了一種短程硝化—反硝化的工藝，即將氨氮氧化為亞硝酸鹽（短程硝化），然后將亞硝酸鹽還原為氮氣。該方法較傳統(tǒng)全程硝化脫氮方法可大大節(jié)省曝氣所耗的能耗、節(jié)省反硝化所需碳源、減少污泥產量，縮短反應時間及減少相應反應器容積。近年來又開發(fā)了將半量氨氮曝氣氧化為亞硝酸鹽，再與另外半量氨氮反應生成氮氣的厭氧氨氧化工藝，可進一步減少一半的曝氣能耗。以上兩種工藝，短程硝化是關鍵，但實施的難點是要控制廢水處理的細菌僅將氧化氨氮至亞硝酸鹽。迄今，國內外研究者一直在致力于尋找操作簡便、具有大規(guī)模應用前景的短程硝化過程控制方法。
2011年，在環(huán)境學院攻讀博士學位的鄭敏在利用超聲波技術進行污泥源頭減量化的試驗研究中發(fā)現(xiàn)，利用適宜的超聲波條件處理活性污泥后的菌群可以在反應器內穩(wěn)定地積累亞硝酸鹽而使硝酸鹽生成量大幅減小。此后，在導師汪誠文的指導下，鄭敏開展了利用超聲波控制細菌種群結構、獲取高效穩(wěn)定短程硝化的全面系統(tǒng)研究。本次發(fā)表的論文是其中的重要成果之一。該文章報道了研究組成功通過超聲波的條件優(yōu)化與控制，利用適當?shù)某暡◤姸却碳ざ坛滔趸匦璧暮醚醢毖趸毦ˋmmonia-oxidizing Bacteria，AOB）生長，同時抑制滅活產生硝酸鹽的亞硝酸鹽氧化細菌（Nitrite-oxidizing Bacteria，NOB），從而實現(xiàn)反應器的持續(xù)運行，并建立了評價超聲波對不同細菌作用的動力學試驗模型。此研究首次全面系統(tǒng)地證實了在超聲波處理條件下，可以控制反應器的細菌種群、富集馴化出含高豐度AOB無NOB的微生物達到高效的短程硝化。該方法將為開發(fā)高效污水處理與污泥資源化組合新工藝提供一條全新思路。今后，研究人員將進一步探明系統(tǒng)控制的微生物生理學和生態(tài)學機理和實現(xiàn)從小型試驗到生產示范過渡。
鄭敏為論文第一作者，汪誠文為通訊作者。合作者中吳唯民參與試驗設計和指導研究工作，劉艷臣參與了試驗設計和微生物學的分析工作。
論文鏈接：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.
