印染廢水開題報告教材

1、本科畢業(yè)設(shè)計 （ 論文） 開題報告題目： 蠟印廢水處理工藝技術(shù)課 題 類 型： 設(shè)計 實驗研究 論文 學(xué) 生姓 名：許軒學(xué)號：31204060213專 業(yè)班 級：環(huán)境工程 122學(xué) 院：生化學(xué)院指 導(dǎo) 教 師： 魏翔開 題 時 間： 2016 年 3 月 4 號2016 年 3 月 15 日一、本課題的研究內(nèi)容及意義 在紡織工業(yè)中會產(chǎn)生各種廢水，其中以印染廢水污染較為嚴(yán)重，其排放量約 占工業(yè)廢水總量的 1/10 ，我國每年約有 67億t 印染廢水排入水環(huán)境中，是當(dāng)前 最主要的水體污染源之一， 因此印染廢水的綜合治理已成為一個迫切需要解決的 問題。印染廢水主要由退漿廢水、煮練廢水、漂白廢水、絲光

2、廢水、染色廢水和 印花廢水等組成，其特點是成分復(fù)雜，色度高，有毒物質(zhì)多，屬于含有一定量有 毒物質(zhì)的有機(jī)廢水， 主要含有殘留染料、 印染助劑、 酸堿調(diào)節(jié)劑和一些重金屬離 子，化學(xué)需氧量 COD較高，而生化需氧量 BOD5相對較小，可生化性差，是當(dāng)前國 內(nèi)外公認(rèn)的較難處理的工業(yè)廢水之一 1 。印染廢水含大量的有機(jī)污染物，排入水 體將消耗溶解氧， 破壞水生態(tài)平衡， 危及魚類和其它水生生物的生存。 沉于水底 的有機(jī)物，會因為氧分解而產(chǎn)生硫化氫等有害氣體， 惡化環(huán)境。 印染廢水的色澤 深，嚴(yán)重影響受納水體外觀， 用一般的生化法難以去除， 有色水體還會影響日光 的透射，不利于水生物的生長。 水是一種易受污

3、染而可以再生的自然資源。 為了 使這個自然水循環(huán)能夠持續(xù)地為人類服務(wù)， 水在使用后回歸自然界前， 必須進(jìn)行 廢水的再生處理， 使水質(zhì)達(dá)到自然界自凈能力的承受水平， 恢復(fù)其作為自然資源 的屬性。 2二、蠟印廢水處理工藝的研究現(xiàn)狀和發(fā)展趨勢（文獻(xiàn)綜述）2.1 研究現(xiàn)狀20 世紀(jì) 90年代以來，我國經(jīng)濟(jì)高速發(fā)展，人民生活水平不斷提高，但環(huán)境 污染問題并未得到有效控制， 在有些地區(qū)反而呈現(xiàn)加重的趨勢。 據(jù)報道， 我國每 年污水的排放量約為 3. 9 1010t ，其中工業(yè)廢水占 51%，并以 1%的速率逐年遞 增3 。隨著工業(yè)化進(jìn)程的不斷深入，全球性環(huán)境污染日益破壞著地球生物圈幾億 年來所形成的生態(tài)平

4、衡， 并對人類自身的生存環(huán)境造成了嚴(yán)重威脅。 由于逐年加 重的環(huán)境壓力， 世界各國紛紛制定各自的環(huán)保法律、 法規(guī)和采取不同的措施， 我 國政府對環(huán)境問題也高度重視， 并向國際社會全球性環(huán)境保護(hù)公約做出了自己的 承諾。我國是紡織印染的第一大國， 而紡織印染行業(yè)又是工業(yè)廢水的大戶， 故有 此而造成的生態(tài)破壞及經(jīng)濟(jì)損失是不可估量的， 因而要實現(xiàn)印染行業(yè)的可持續(xù)發(fā) 展，必須首先解決印染行業(yè)的污染問題。 42.2 發(fā)展趨勢目前印染廢水的處理逐漸向膜法和其它處理技術(shù)相結(jié)合發(fā)展。 工程師與研究 人員不斷開始研制新的超濾膜， 改善超濾膜的材質(zhì)， 孔徑大小等方面性能， 主要 為了降低膜的制作成本， 提高過濾效能

5、。 然而膜法仍然具有它的缺點， 只采用透 過液反沖洗的清洗方法已不能保持膜的通量穩(wěn)定， 需采用藥劑清洗， 膜的污染比 較嚴(yán)重，這一問題尚未很好的解決。 而且，國內(nèi)目前還未開發(fā)出高質(zhì)量的超濾膜 裝置，需從國外引進(jìn)成套的工藝設(shè)備，價格必然不菲。因此如何降低成本，保持 膜的穩(wěn)定性能是未來研究的重點 5 。2.3 印染廢水的處理方法吸附法吸附法是應(yīng)用較多的物理處理方法。 該方法采用多孔狀物質(zhì)的粉末或顆粒與 印染廢水混合，或使廢水通過由顆粒狀物質(zhì)組成的濾床 , 使廢水中染料、助劑等 污染物質(zhì)吸附于多孔物質(zhì)表面等而除去。 吸附技術(shù)特別適合低濃度印染廢水的深 度處理,在工藝上具有投資小 ,方法簡便易行 ,成

6、本較低的優(yōu)點。吸附法在實際應(yīng) 用過程中應(yīng)重點考慮吸附劑的選擇、吸附劑的再生以及廢吸附劑的后處理 , 以提 高處理效果 , 降低處理成本和減少二次污染。常用的吸附劑主要有活性炭、離子 交換纖維、爐灰、各種天然礦物、工業(yè)廢料及天然植物廢料等，一些合成無機(jī)吸 附劑也被應(yīng)用于處理印染廢水，如含有 SiO2 的復(fù)合氧化物、合成 Mg(OH2) 吸附 劑等。由于印染廢水的水質(zhì)復(fù)雜， 單一的吸附處理無法達(dá)到理想的處理效果， 實 際應(yīng)用中需進(jìn)一步開發(fā)適用性較廣的吸附劑同時必須開發(fā)吸附技術(shù)與其它技術(shù) 的組合工藝 6,7 ?；瘜W(xué)氧化法化學(xué)氧化是目前研究較為成熟的方法。 借助氧化還原作用破壞染料的共軛體 系或發(fā)色基

7、團(tuán)是印染脫色處理的有效方法。 除常規(guī)的氯氧化法外， 國內(nèi)外研究重 點主要集中在臭氧化、超聲波氧化、過氧化氫氧化、電解氧化和光氧化方面。氧 化劑一般采用 Fenton 試劑、臭氧、氯氣、次氯酸鈉等。按氧化劑的不同，可將 化學(xué)氧化分為： 臭氧化法和芬頓試劑氧化法。 氧化法是一種優(yōu)良的印染廢水脫色 方法，但如果氧化程度不足， 染料分子的發(fā)色基團(tuán)可能被破壞而脫色， 但其中的 COD仍未除盡；若將染料分子充分氧化，能量、藥劑量消耗可能會過大，成本太 高。臭氧化法不產(chǎn)生污泥和二次污染， 但是處理成本高， 不適合大流量廢水的處 理，而且 COD去除率低。 通常很少采用單一的臭氧法處理印染廢水， 而是將它與

8、其它方法相結(jié)合， 彼此互補達(dá)到最佳的廢水處理效果。 所以氧化法一般用于氧化 絮凝或絮凝氧化工藝 8,9 。2.3.3 生物處理法生物處理法是利用微生物酶來氧化或還原有機(jī)物分子， 通過一系列氧化、 還 原、水解、 化合等生命活動， 最終將廢水中有機(jī)物降解成簡單無機(jī)物或轉(zhuǎn)化為各 種營養(yǎng)物及原生質(zhì)。 生物法具有運行成本低、 處理效果穩(wěn)定等優(yōu)點， 在印染廢水 處理中得到了較為廣泛的應(yīng)用。 常用的印染廢水生物處理方法有厭氧法、 好氧法、 厭氧好氧組合法。好氧生物處理是在有氧條件下，利用好氧微生物的作用來去除印染廢水中 的有機(jī)物?；钚晕勰喾?、生物濾池、生物轉(zhuǎn)盤、氧化溝、生物塘和膜生物反應(yīng) (MBR) 等都

9、屬于廢水好氧生物處理法。強化生物鐵活性污泥法， 通過采取向曝氣池中投加氫氧化鐵， 延長難降解物質(zhì)的 停留時間等措施， 能大幅提高曝氣池的活性污泥濃度和抗沖擊負(fù)荷能力， 降低污 泥負(fù)荷，使單位數(shù)量菌團(tuán)承擔(dān)的有機(jī)物降解量減少， 使菌膠團(tuán)表面的有機(jī)物得到 及時! 充分的氧化降解，從而提高系統(tǒng)的脫色率和 COD去除率。生物膜法是將微生物細(xì)胞固定在填料上， 微生物附著于填料上生長、 繁殖， 在其上形成膜狀生物污泥。 與常規(guī)活性污泥法相比， 生物膜法具有生物體體積濃 度大，存活世代長， 微生物種類繁多等優(yōu)點， 尤其適合于特種菌在印染廢水體系 中的投加使用。常用的生物膜法包括 生物轉(zhuǎn)盤、生物接觸氧化法、生物

10、濾池。 厭氧生物法不僅可用于處理高濃度有機(jī)廢水， 也可用于處理中、低濃度有機(jī)廢水， 對染料中的偶氮基、 蒽醌基和三苯甲烷基均可降解， 但還不能完全分解一些活性 染料的中間體，如致癌的芳香胺等。 由于厭氧生物法的出水水質(zhì)往往達(dá)不到排 放標(biāo)準(zhǔn)，因而單純使用厭氧生物法的處理工藝較少， 通常與好氧生物法串聯(lián)使用。 厭氧好氧組合處理工藝， 能在一定程度上彌補好氧生物處理工藝的不足。 難降解 染料分子及其助劑在厭氧菌的作用下水解 ! 酸化而分解成小分子有機(jī)物，接著被 好氧菌分解成無機(jī)小分子。 通常厭氧段采用 USB反應(yīng)器，好氧段目前大多采用生 物接觸氧化法。間歇曝氣活性污泥 SBR工藝，采用間歇運行方式，

11、廢水間歇地進(jìn) 入處理系統(tǒng)并間歇地排出， 充分利用兼性菌的作用， 在同一反應(yīng)器內(nèi)程序地進(jìn)行 缺氧- 厭氧- 好氧過程，抗負(fù)荷與毒物沖擊能力顯著增強，可實現(xiàn)高進(jìn)水濃度 ! 高容積負(fù)荷和高有機(jī)物去除率，在處理高濃度印染廢水方面獨具特色而且對氮、 磷、硫的脫除效果亦十分顯著 9.10 。2.3.4 光化學(xué)氧化法光催化氧化法是利用某些物質(zhì)在紫外光的作用下產(chǎn)生自由基 , 氧化染料分子 而實現(xiàn)脫色。 TiO2 光催化氧化法在 PH值為 3-11 時產(chǎn)生 O和OH，使染料分子迅 速分解而獲得很好的脫色效果。鐵羧酸配合物光催化氧化法，以鐵-草酸、鐵 -檸檬酸或鐵 - 丁二酸絡(luò)合物作催化劑，在紫外光照射下，光解生

12、成烷基、羥基等 多種自由基， 使印染廢水氧化脫色。 光催化氧化技術(shù)以其具有常溫常壓操作、 有 害物質(zhì)分解徹底、 能耗及材料消耗低、 無二次污染等優(yōu)點， 具有良好的應(yīng)用前景 11,12。2.3.5 膜分離技術(shù)膜分離技術(shù)處理印染廢水是通過對廢水中的污染物的分離、 濃縮、回收而達(dá) 到廢水處理目的。具有不產(chǎn)生二次污染、能耗低、可循環(huán)使用、廢水可直接回用 等特點。膜分離技術(shù)雖然具有如此多的優(yōu)點， 但也存在著尚待解決的問題， 如膜 污染、膜通量、膜清洗、以及膜材質(zhì)的抗酸堿、耐腐蝕性等問題，所以，現(xiàn)階段 運用單一的膜分離技術(shù)處理印染廢水， 回收純凈染料， 還存在著技術(shù)經(jīng)濟(jì)等一系 列問題?，F(xiàn)在膜處理技術(shù)主要有

13、超濾膜， 納米濾膜和反滲透膜。 膜處理對印染廢 水中的無機(jī)鹽和 COD都有很好的去除作用 13 。2.3.6 高能物理法線輻照下產(chǎn)生一系列高活性粒子 , 有害物質(zhì)得到降解 . 技術(shù)的特點是有機(jī)物 的去除率高 ,備占地面積小 ,作簡便,由于用來產(chǎn)生高能粒子的設(shè)備昂貴 ,術(shù)要求 高,耗大,量利用率低 ,真正投入實際應(yīng)用還有大量的問題需要解決 14。三、課題研究方案及工作計劃印染廢水處理工藝中的厭氧水解處理工藝是利用產(chǎn)甲烷菌與水解產(chǎn)酸菌生 長速度不同，在反應(yīng)器中以水流動的淘洗作用，使甲烷菌在反應(yīng)器中難以繁殖， 將厭氧處理控制在反應(yīng)時間短的第一階段，即在大量水解細(xì)菌、產(chǎn)酸菌作用下， 將不溶性有機(jī)物水解

14、為可溶性有機(jī)物， 將難生物降解的大分子物質(zhì)轉(zhuǎn)化為易生物 降解的小分子物質(zhì)。 將厭氧水解處理作為各種生化處理的預(yù)處理， 可提高污水生 化性能， 降低后續(xù)生物處理的負(fù)荷， 因而被廣泛運用在難生物降解的化工、 造紙 及有機(jī)物濃度高的食品廢水處理中。 此外，厭氧水解處理亦可用于城市污水處理 廠，以水解池代替初沉池， 減少后續(xù)處理構(gòu)筑物曝氣池的停留時間， 從而降低工 程投資。本課題采用厭氧水解處理， 蠟染印染廢水的處理工藝包括以下步驟： 將污 水收集至調(diào)節(jié)池；在調(diào)節(jié)池內(nèi)設(shè)置曝氣裝置，調(diào)節(jié) PH值至 89；在平流沉 淀池前分別投加聚合氯化銨（ PAC）和聚丙烯酰胺（ PAM）；在厭氧池內(nèi)進(jìn)行厭 氧處理，

15、并外加間歇式內(nèi)循環(huán)回流； 在接觸氧化池內(nèi)進(jìn)行供氧； 在沉淀池內(nèi) 進(jìn)行泥水分離； 將污泥濃縮池的污泥壓縮采用水壓式隔膜壓濾機(jī)過濾， 形成泥 餅15 。如圖：工作計劃：（1）、第 12 周：查閱相關(guān)資料，了解研究內(nèi)容及現(xiàn)狀，制訂研究方案，擬訂 初步的工作計劃；（ 2）、第 34 周：開題，完善研究方案；（3）、第 514 周：查閱相關(guān)資料和文獻(xiàn)，進(jìn)行相關(guān)圖紙的繪制及計算；（ 4）、第 1517 周：編寫畢業(yè)論文（5）、第 18 周：畢業(yè)論文答辯四、主要參考文獻(xiàn)1 孫政.印染廢水水質(zhì)特征及生物處理技術(shù)綜述 .煤礦現(xiàn)代化 .2007 年第一期2 戴日成，張統(tǒng)，郭茜，曹健舞，蔣用印染廢水水質(zhì)特征及處理技

16、術(shù)綜述 . 工業(yè) 給排水3 耿云波，劉永紅，趙鵬飛印染廢水處理技術(shù)的應(yīng)用及研究進(jìn)展，工業(yè)用水與 排水 Vo1.41 No.4 Aug.20104 周瑤，郭超，楊波，前夕印染廢水處理工藝，黑龍江環(huán)境通報 Vo1.34 No.2 Jun.20105 肖冬雪，王兆慧，郭耀光，柳建設(shè)印染廢水的處理方法及其發(fā)展趨勢的探討 CHINA POPULATION,RESOUCES AND ENVIRONMENT Vo1.21 20116 趙宜江,張艷,嵇鳴,等.印染廢水吸附脫色技術(shù)的研究進(jìn)展 j .水處理技 術(shù),2000,26（6）:315-3197 張建英,梁緣東,陳曙光,等,染色廢水吸附混凝效應(yīng)研究 j ,

17、環(huán)境污染與防 治,1998,20（3）:9-128 張艷,趙宜江,嵇鳴,等.印染廢水物理化學(xué)脫色方法的研究進(jìn)展 j .水處理技 術(shù),2001,27（6）:311-3149 鄭冀魯,范娟,阮復(fù)昌,印染廢水脫色技術(shù)與理論技術(shù) j .環(huán)境污染治理技術(shù)與 設(shè)備,2000,1（5）:29-3510 魏建斌, 付永勝, 朱杰,等.印染廢水生物脫色研究現(xiàn)狀及展望 j. 污染防治技 術(shù),2003,16（4）:87-9111 劉長春, 張峰, 畢學(xué)軍.TiO 2光催化氧化技術(shù)在廢水處理中的應(yīng)用 j. 污染防治 技術(shù),2003,16(4):111-11412 羅凡,吳峰, 鄧南圣, 等, 鐵()羧酸配合物對水溶性

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19、,ScienceDirect,Separation and Purifcation Technology 60(2008)64-721718 .Biotechnology & Bioprocess Enfineering Feb2014, Vol. 19 Issue 1, p191-200. 10p.19 Wool Textile Journalapr2015, Vol. 43 Issue 4, p41-44. 4p.20 Journal of the Serbian Chemical Society.2015, Vol. 80 Issue 1,p115-125. 11p.外文文獻(xiàn)翻譯英文部分

20、Abstract In this study, the bacterial dynamics and structure compositions in the two-stage biological process of a full-scale printing and dyeing wastewater (PDW) treatment system were traced and analyzed by terminal restriction fragment length polymorphism (T-RFLP) and 454 pyrosequencing techniques

21、. T-RFLP analysis showed that the microbial communities experienced significant variation in the process of seed sludge adaptation to the PDWe nvironments and were in constant evolution during the whole running period of the system, despite the constant CODa nd color removal effects. Pyrosequencing

22、results indicated that the two-stage biological system harbored rather diverse bacteria, with Proteobacteria being the predominant phylum during the steady running period, although its microbial compositions differed. The firststage aerobic tank was dominated by -Proteobacteria (89.05% of Proteobact

23、eria), whereas in the second-stage aerobic tank, - and -Proteobacteria,besides16 -Proteobacteria, were the dominant bacterial populations.1. IntroductionPrinting and dyeing wastewater (PDW) has long been considered as an important and difficult-to-treat effluent due to its toxic, frequently changing

24、, and bio-recalcitrant components such as dyes and dyeing additives, low ratio of BOD5/COD (around 20%), and high pH value (10 13). The current PDW treatment employed in China is a combination of physical-chemical and biological processes, in which various biological methods play principal roles and

25、 are capable of removing 40 50% of COD and 50 60% of color. However, during system startup or system running period, important problems such as reduced oncentration of activated sludge, sludge expansion, and formation of large amounts of foam frequently occur, resulting in a serious decrease in trea

26、tment efficiency or even collapse of the system. Bacteria are the dominant population in the activated sludge, and it is hypothesized that the dominant microorganisms play the most important roles in each stage of the system. Therefore, determination of the bacterial compositions corresponding to th

27、e stages of the system will be helpful for understanding and solving the above-mentioned problems. In recent years, various molecular biological techniques have been used for the analysis of microbial communities in various wastewater treatment systems. However, most of the previous studies had focu

28、sed more on the relationship between functional stability and microbial community stability or the effects of running parameters on microbial compositions under the conditions of lab-scale bioreactors normally fed with synthetic wastewater. Only a few reports had examined fullscale industrial wastew

29、ater treatment systems, and even fewer had analyzed PDWtr eatment systems. Due to the frequently changing characteristics and complex compositions of PDW, understanding of the relationship between the microbial community dynamics and startup and stable running of the system is important for the desi

30、gn and operation of a PDWt reatment system. The molecular biological techniques have some limitations in completely revealing the microbial compositions or tracking the evolution process of the microbial community in a wastewater treatment system. In our previous study on the dynamic changes in the

31、microbial community in the PDW treatment system, PCR-DGGE (denaturing gradient gel electrophoresis) method was used. However, with the development of sequencing techniques, it has been noted that DGGE indicates only a minor part of the microbial population in an environment. Furthermore, some recent

32、ly developed techniques such as terminal restriction fragment length polymorphisms (T-RFLP), real-time PCR, 454 pyrosequencing, etc., provide a possibility to obtain dynamic information or more accurate compositions of a microbial community. Therefore, in this study, T-RFLP and 454 pyrosequencing me

33、thods were used to trace and reveal the evolution processes of bacteria in a full-scalePDW biologicaltreatment system during the establishment and commissioning periods. The results of this studyare expected to form the basis of further researchon the functions of the microbial populations in wastew

34、ater treatment systems17 .2. Materials and Methods2.1. PDW treatment system and wastewater characteristicsThe PDW treatment system was established by Xinxiang Lianda Printing & Dyeing Co., Ltd (Xinxiang, China) in October 2009 for treating 1,000 tons of effluent everyday. The system consisted of aco

35、agulation precipitation unit and a two-stage biological treatment process, including process 1 (an anaerobic hydrolytic and acidification unit (H1), an aerobic activated sludge treatment unit (O1), and a settling tank 1) and process 2 (an anaerobic hydrolytic and acidification unit (H2), an aerobic

36、bio-contact oxidation unit (O2), and a settling tank 2), as shown in Supplementary Fig. 1. The seed sludge was collected from a municipal wastewater treatment plant and was first inoculated into O1 at the beginning of the system startup. H2 was started 23 days after O1 operation by inoculating a par

37、t of sludge from the settling tank 1 and a part of sludge from the same municipal wastewater treatment plant as that used for inoculating O1.The characteristics of PDW and the performance of the biological wastewater treatment system were continuously monitored for more than 6 months. The concentrat

38、ions of COD, BOD5, colority, suspended solids (SS), total nitrogen (TN), total phosphates (TP), NH4+ -N, and pH were determined using standard methods 12. The characteristics of the wastewater are shown in Supplementary Table 1.2.2. Sludge samplesSludge samples were collected from the above-mentione

39、d biological treatment units at different periods of operation, i.e., seed sludge (day 1 and day 23 for O1 and H2, respectively), after system startup (day 23 for both O1 and H1; day 29 for O2), and in the middle of operation (day 29 and day 185 for O1 and H1, respectively; day 185 for both O2 and H

40、2).The samples from different treatment tanks were centrifuged at 12,000 rpm for 10 min at 4o C. The pellets were washed twice (each were centrifuged for 10 min at 12,000 rpm) with phosphate buffer (pH 7) and stored at-20 for molecular analysis.2.3. DNA extractionThe total DNA was extracted from the

41、 sludge pellets by using the cetyltrimethylammonium bromide (CTAB) method 13. The yield and fragmentation of the crude or purified DNAw ere determined by agarose gel electrophoresis (1% w/v agarose) and UV visualization after ethidium bromide (EB) staining. The purified DNA was then stored at- 20 fo

42、rT-RFLP and pyrosequencing.2.4. PCR amplification of 16S rRNA genes for T-RFLPFor T-RFLP analysis, labeled forward primer 63F (labeled with 6-FAM( blue) (5-CAG GCC TAA CAC ATG CAA GTC-3) and unlabeled reverse primer 1389R (5-ACG GGCG GTG TGT ACA AG-3) were used 10. The PCRw as conducted under the fo

43、llowing conditions: 95for 5 min, followed by 30 cycles of 94for 1 min, 55 for 1 min, and 72 for 2 min, and a final extension at72 for 10 min. The 1.3-kb 16S rRNA gene fragments obtained by PCR were purified from 1% agarose gels with a UNIQ10 column DNA purification kit (Sangon, China) according to t

44、he manufacturer s recommendations 18.2.5. T-RFLP analysisThe labeled PCR products (10L) were digested at 37 for 16 h withAluI(AG/CT) and MspI(C/CGG), respectively. The reaction mixtures contained 2 L of 10 restriction enzyme buffer, 10 L of template, 1 L of AluI or MspI, and ultrapure water to a fin

45、al volume of 20L. Thereactions were inactivated by incubation at 80 for 20 min for AluI and 65 for 20 min for MspI. The digested DNAwas precipitated with 75Lof 95% ice-cold ethanol and 3 L of 3 M sodium acetate at-20 for 12h, followed by spinning at 4,000 rpm and 4 in a micro centrifuge for60 min. T

46、he DNA pellet was washed with 70% ice-cold ethanol, dried, and suspended in 9 L of sterile water foranalysis 14. The TRFs wereanalyzed by Shanghai Gene Core Bio-Technologies Co., Ltd (Shanghai, China). The T-RFLP profiles were aligned by inspecting the electrophore to grams and by manual grouping of

47、 the peaks into categories. The presence or absence of peaks in the T-RFLP profiles was the basis for the construction of a pair wise Dice distance matrix for use in a non-parametric multidimensional scaling (NM-MDS)a nalysis utilizing the PC-Ord 5.0 software.2.6. High-throughout 454 pyrosequencingT

48、he composition of the PCRp roducts of the V3 region of 16S rRNA gene was determined by 454 pyrosequencing by BGI (Shenzhen, China). The bacterial universal primer pair,27F (5-AGAGTTTGATCCTGGCTCAG-3a) nd 534R (5-ATTACCGCGGCTGCTGG-3), was used 15, and the samples used in this study were individually b

49、arcoded to enable multiplex sequencing. Following pyrosequencing, Python scripts were written to: (1) remove sequences containing more than one ambiguous base; (2) check the completeness of the barcodes and the adapter; and (3) remove sequences shorter than 150 bp 16. The effective sequences were an

50、alyzed by using RDP(Ribosomal Database Project, ) to construct the distance matrices, assign sequences to operational taxonomic units (OTUs, 97%s imilarity),and calculate Chao1 richness estimators 17. Thesequences of the dominant OTUs were extracted to run BLAST and search relatives against “nr” dat

51、abase using the Internet automatically (). A phylogenetic tree was constructed using the neighbor joining method in MEGA version 4.1 using 1,000 bootstrap replications. The archaeon Methanobacterium formicicum was used as an out-group 19 .3. Results and Discussion3.1. Performance of the PDW treatmen

52、t systemThe COD and color of the PDW were 646 5,056 mg/L and 80 650 dilutes, respectively. After coagulation and precipitation by using FeSO4 and poly-aluminum chloride (PAC), the COD and color reduced to 417 3,750 mg/L and 40 550 dilutes, with an average removal rate of 43.9 and 38.5%, respectively

53、. At the same time, the pH of the PDW was significantly reduced from 10.96 to 13.89 to around 8.50, which was necessary for the subsequent biological treatment. After the first-stage biological process, the CODa nd color were reduced to 174 902 mg/ L and 30 80 dilutes, with removal efficiencies of 2

54、5 83.4% and 25 89.1%, respectively. Green was the most difficult color to decolorize, whereas black and blue were easier to remove. Subsequently, for further treatment, the effluents from the first-stage biological treatment process were fed into the second-stage treatment process that was composedo

55、 f a hydrolysis tank and a biofilm contact oxidation tank. A further 10.8 53.9 and 25 66.7% reduction in COD and color were noted after this process, respectively, resulting in a final COD of 500 mg/L and color of 40 dilutes. After coagulation and the two steps of biological treatment, the total ave

56、rage removal rates of COD and color reached 85%, with the final color of the effluents satisfying the local discharge standards ( 50 dilutes). However, a residual CODo f 146 492 mg/L was noted, which could be resolved through further treatment by using Fenton oxidation method.3.2. Dynamic changes in

57、 the bacterial community structure with system operationThe dynamic variation in the bacterial community was traced by using T-RFLP method (as shown in Supplementary Figs. 2 and 3). The T-RFLP profiles indicated diverse and fluctuating dominant bacterial populations in the collected samples. Analysi

58、s of Shannon diversity index on the T-RFLP profiles indicated that different treatment tanks of the system harbored diverse bacteria, with H = 0.83 1.20 and 0.71 1.07 for AluI and MspI restriction enzyme digestion maps, respectively. Samples from the first biological treatment process (O1 and H1) showed higher bacterial diversity than those from the second one (O2 and H2). The dominant peaks changed both in height and peak time among the seed sludge samples and steady running stage samples,