任武昂,曹鋒鋒,鞠 愷,金鵬康,李思敏,柴蓓蓓,雷曉輝

間歇曝氣-內(nèi)循環(huán)生物濾池效能及生物膜特性

任武昂1,曹鋒鋒1,鞠 愷1,金鵬康2,李思敏3,柴蓓蓓4,5*,雷曉輝5

(1.西安科技大學(xué)建筑與土木工程學(xué)院,陜西 西安 710054；2.西安交通大學(xué)人居環(huán)境與建筑工程學(xué)院,陜西 西安 710049；3.河北省水污染控制與生態(tài)修復(fù)技術(shù)創(chuàng)新中心,河北 邯鄲 056038；4.河北工程大學(xué)水利水電學(xué)院,河北 邯鄲 056038；5.河北省智慧水利重點(diǎn)實(shí)驗室,河北 邯鄲 056038)

針對間歇曝氣耦合內(nèi)循環(huán)生物濾池的強(qiáng)化脫氮作用機(jī)制尚不明確的問題,探究了反應(yīng)器沿程污染物去除特性,運(yùn)用多項測試手段解析系統(tǒng)沿程生物量、生物活性、硝化及反硝化速率,并對反應(yīng)器內(nèi)沿程微生物種群特性進(jìn)行分析.試驗結(jié)果表明:沿程類蛋白熒光強(qiáng)度逐漸減弱,最終出水并未檢測到類蛋白峰;反應(yīng)器沿程10～50cm區(qū)段NH4+-N的降低并沒有引起NO3--N大幅增長,并且在50cm處NO3--N含量有所下降,該段反硝化作用明顯;沿程溶氧環(huán)境和生物量也顯示,該區(qū)域具備較為明顯的缺/厭氧的環(huán)境以及富集了充足的生物量;此外,50cm處的好氧速率(OUR)低但TTC-脫氫酶活性高以及反硝化速率明顯強(qiáng)于硝化速率,均可表明系統(tǒng)在該區(qū)域強(qiáng)化了反硝化脫氮過程.另外,16S rRNA高通量測序分析顯示:系統(tǒng)在門水平上涉及反硝化功能的微生物有更高的豐度,主要有Firmicutes (厚壁菌門:10.64%)和Bacteroidetes (擬桿菌門:22.29%);在屬水平上也明顯存在反硝化功能的(叢毛單胞菌屬:3.11%)和(2.43%).上述研究均表明間歇曝氣耦合內(nèi)循環(huán)的BAF系統(tǒng)強(qiáng)化了底部區(qū)域的反硝化作用進(jìn)而提升了脫氮效能.

生物濾池；間歇曝氣；內(nèi)循環(huán)；污染物；微生物響應(yīng)

曝氣生物濾池(BAF)是集生物降解和濾料物理截留為一體的生物膜處理工藝,具有抗沖擊負(fù)荷能力強(qiáng)、不易發(fā)生污泥膨脹、管理簡便等特點(diǎn)[1-3],對COD和NH4+-N有較高的去除效率[4].由于傳統(tǒng)BAF具有推流反應(yīng)器的特征,很難在反應(yīng)器內(nèi)形成硝酸鹽氮與有機(jī)物同步富存的環(huán)境,限制了系統(tǒng)的反硝化作用導(dǎo)致總氮的去除效率較低[5].為強(qiáng)化BAF脫氮功能,一般采用構(gòu)建硝化和反硝化兩級曝氣生物濾池的方式來實(shí)現(xiàn)對水中總氮的削減[6-7].在單級BAF中增加內(nèi)回流,可將富含硝酸鹽氮的處理水引入反應(yīng)器底部區(qū)域與原水混合,為反硝化反應(yīng)提供的必要的基質(zhì)條件[8];此外,田兆龍等[9]改變傳統(tǒng)BAF的供氧策略,通過間歇曝氣的方式可以在反應(yīng)器內(nèi)創(chuàng)造好氧/缺氧交替的環(huán)境. 因此,構(gòu)建間歇曝氣耦合內(nèi)循環(huán)生物濾池理論上可以提高單級BAF的總氮脫除效率.課題組前期的研究成果顯示, BAF間歇曝氣耦合內(nèi)循環(huán)的技術(shù)措施將系統(tǒng)總氮去除效果從41.8%提升至75.23%[10],證實(shí)了該思路與工藝的可行性與有效性.

BAF作為一種典型的生物膜反應(yīng)器,改變運(yùn)行工況來提升系統(tǒng)處理效率的本質(zhì)是通過創(chuàng)造適宜的基質(zhì)條件與環(huán)境條件,在系統(tǒng)內(nèi)富集功能微生物并使其充分發(fā)揮作用[11-12].本文以間歇曝氣耦合內(nèi)循環(huán)生物濾池實(shí)驗裝置為研究對象,通過檢測反應(yīng)器沿程水質(zhì)指標(biāo)變化情況,并運(yùn)用多項測試手段解析系統(tǒng)沿程生物量、生物活性、硝化及反硝化速率;借助高通量測序技術(shù)對反應(yīng)器內(nèi)沿程微生物種群特性比對分析,以期揭示間歇曝氣耦合內(nèi)循環(huán)生物濾池反應(yīng)器提升脫氮效能的作用機(jī)理.

1 材料與方法

1.1 實(shí)驗裝置

圖1 實(shí)驗裝置示意

a BAF實(shí)驗裝置;b 好氧速率裝置

構(gòu)建的間歇曝氣耦合內(nèi)循環(huán)的BAF實(shí)驗裝置如圖1a所示,反應(yīng)器主體為圓柱形,內(nèi)徑為15cm,外徑為25cm,總體高度為240cm.底部是高為20cm的均勻配水區(qū),上方高為30cm的襯托層,填料層高為140cm,并以20cm等距設(shè)置7個直徑為8mm的采樣口;頂部高為50cm的靜水區(qū),各分區(qū)之間用法蘭連接.好氧速率檢測裝置如圖1b,錐形瓶置于恒溫磁力攪拌器上,DO電極穿過橡膠塞插入掛膜填料和充氧飽和的生活污水中,待DO穩(wěn)定后從溶解氧儀上讀取數(shù)值.

1.2 運(yùn)行工況

維持BAF反應(yīng)器在最佳工況條件下連續(xù)運(yùn)行[10],主要的運(yùn)行參數(shù)為:硝化液回流比為100%、曝氣停曝比為1:1(曝氣30min,停曝30min)、HRT為6h、氣水比為6:1、整個反應(yīng)器溫度控制為(22±2)℃、采用的反沖洗流程為:氣洗2～5min、氣水混合洗4～6min、水洗8～10min,沖洗強(qiáng)度均為8～16L/(m3·s),反沖洗周期為4d.此外,在填料層高為10, 50, 130cm處設(shè)置沿程取樣點(diǎn)(A1、A2和A3).

1.3 檢測項目與方法

1.3.1 常規(guī)指標(biāo)檢測方法 水質(zhì)參數(shù)如COD、NH4+-N、NO3--N、TN等常規(guī)指標(biāo)均采用《水和廢水監(jiān)測分析方法》(第四版)方法測定[16],DO測定選用便攜式溶解氧儀.

1.3.2 三維熒光光譜分析 待測水樣取自原水、填料層高為50cm取樣口和出水,測定前用0.45μm濾膜進(jìn)行過濾.儀器參數(shù)設(shè)置:激發(fā)波長為200～450nm,發(fā)射波長為250～550nm,步長2nm,狹縫寬度為1.11mm,對應(yīng)熒光譜分辨率為2nm.

1.3.3 生物量和活性測定 系統(tǒng)沿程濾料生物量采用MLVSS法測定[17];生物活性分別以O(shè)UR[18]和TTC-脫氫酶活性測定[19].

1.3.4 硝化速率和反硝化速率測定 硝化速率測定需調(diào)節(jié)曝氣量以維持溶解氧濃度在2mg/L以上,反硝化速率測定需充入N2創(chuàng)造缺氧環(huán)境.分別在30, 60, 90, 120min取樣,混合液經(jīng)0.45μm濾膜過濾后測其NO3--N和NO2--N濃度,并計算單位重量填料的硝化和反硝化速率[20].

1.4 DNA提取和高通量測序

采用16S rRNA高通量測序技術(shù)研究BAF系統(tǒng)沿程微生物多樣性和群落結(jié)構(gòu).樣品取自在間歇曝氣耦合內(nèi)循環(huán)生物濾池系統(tǒng)穩(wěn)定條件下的生物填料,依據(jù)沿程DO和水質(zhì)變化情況選取填料層高為10, 50和130cm為微生物采樣口,測試時分別將其編號為A1、A2、A3.DNA提取采用試劑盒(E.Z.N.ATM Mag-Bind Soil DNA Kit),利用1%瓊脂糖凝膠電泳檢測抽提樣品總的DNA.選擇341(CCTACGGG- NGGCWGCAG)和805R(GACTACHVGGGTATCT- AATCC)作為引物,對V3-V4高變區(qū)域16S rRNA序列進(jìn)行擴(kuò)增[21].在上海生工生物工程股份公司的Illumina MiSeq測序平臺進(jìn)行高通量測序.

2 結(jié)果與討論

2.1 污染物變化特性

如圖2a所示,在間歇曝氣耦合內(nèi)循環(huán)生物濾池系統(tǒng)穩(wěn)定條件下,根據(jù)COD降解速率的不同,反應(yīng)器沿程水質(zhì)變化情況大致分為a(0～50cm)、b(50～ 110cm)、c(110～150cm)3段,各段填料層生物對COD的去除率分別為46.98%、27.75%、12.79%,逐漸降低.該現(xiàn)象主要是由于進(jìn)水端有機(jī)物充沛,加之氧氣供給有利于微生物的生長繁殖,因此在a段有機(jī)物降解消耗的速率最快;這與之前李燕飛等[22]的研究結(jié)論相似.沿程至110cm處,COD已降低至36.39mg/L,此時有機(jī)物相對匱乏,已然成為限制異養(yǎng)菌增殖的主要原因,導(dǎo)致COD的去除速率降至最低.

如圖2b所示,生活污水中的TN濃度主體是NH4+-N,因此兩者的沿程濃度呈現(xiàn)出一致的變化規(guī)律.就硝化速率而言,在填料層高為70cm處可分為前后2段;在前段NH4+-N平均去除率為79.64%,遠(yuǎn)高于后段13.75%的平均去除率.可見,在前段基本可完成NH4+-N轉(zhuǎn)化,說明此區(qū)域硝化細(xì)菌代謝能力強(qiáng).進(jìn)水NO3--N濃度幾乎為0,隨著水流的上升,沿程N(yùn)O3--N含量逐步富集,直至出水濃度的10.61L/(m3·s);在10～50cm區(qū)域,NH4+-N大幅降低并沒有導(dǎo)致NO3--N過快增長,并且在50cm處NO3--N含量有所下降,推測10～50cm區(qū)域存在較強(qiáng)的反硝化作用.

從圖3a可以看出,原水的三維熒光光譜圖中有2個比較明顯的特征熒光峰,其中峰Ａ中心位置為x/m=280nm/340nm,屬于高激發(fā)波長色氨酸熒光峰,主要是蛋白質(zhì)的熒光貢獻(xiàn);峰B中心位置為x/m=225nm/340nm,屬于低激發(fā)波長色氨酸熒光峰; 填料層高為50cm的出水三維熒光光譜圖(圖3b)在x/m=320nm/410nm處還存在1個較弱的峰C,其與可見區(qū)的類腐殖酸有關(guān).系統(tǒng)出水的三維熒光光譜圖(圖3c)基本已檢測不到峰A.峰C強(qiáng)度變化不大,這與其代表較難被微生物降解的類腐殖質(zhì)有關(guān).峰A和峰B則有一定程度的削弱,峰A的消減強(qiáng)度最大,這是因為該峰常被認(rèn)為是污水中易被生物降解組分[23].

a為原水;b為填料層高為50cm的出水;c為系統(tǒng)出水

進(jìn)水中三維熒光光譜可觀察到強(qiáng)烈的類蛋白峰,而類蛋白與COD具有較好的正相關(guān),表明進(jìn)水富含有機(jī)碳源與營養(yǎng)物質(zhì).沿程出水過程中類蛋白熒光強(qiáng)度逐漸減弱,最終并未檢測到類蛋白峰,這也佐證了該系統(tǒng)對COD的處理效果好,碳源匱乏也是限制反硝化脫氮的主要因素[24].

2.2 DO和生物量變化規(guī)律

如圖4所示,對曝氣30min和停曝氣30min后的沿程DO濃度進(jìn)行測定,2種不同曝氣條件下BAF填料層沿程DO均呈山谷型分布.在填料層高為10cm處DO較高(DO>2mg/L),這是由于回流的硝化液DO>4mg/L,與進(jìn)水混合后仍保持較高的DO.在30～70cm區(qū)段,不同曝氣階段DO都顯著下降,出現(xiàn)了低谷,最低DO<0.5mg/L;分析認(rèn)為底部有機(jī)物充沛,加之系統(tǒng)內(nèi)部富集了大量活躍狀態(tài)的好氧菌,可迅速實(shí)現(xiàn)對DO的消耗.之后在90～150cm區(qū)段內(nèi)DO持續(xù)升高并至3mg/L之上;這是由于系統(tǒng)推流式的特性和高溶解氧的內(nèi)部回流所致.由曝氣與停曝氣階段的沿程DO比對可知,在30～70cm區(qū)段擁有較高NO3--N濃度和有機(jī)物,這些都是強(qiáng)化反硝化過程的基礎(chǔ);加之停曝氣階段形成的缺氧環(huán)境為生物脫氮提供了有利條件,提高了該區(qū)域的反硝化效率.

如圖4b所示,進(jìn)水端填料區(qū)和出水端填料區(qū)可MLVSS平均含量分別為9.19, 2.59mg/g,進(jìn)水端的生物量是出水端的3倍.這是由于底部的填料能夠截留大量的懸浮物,有機(jī)物濃度高,可供異養(yǎng)菌生長繁殖所需,使得該區(qū)域可富集更多的生物量[17].出水端生物量低的主要原因是水體中易被生物降解的有機(jī)物質(zhì)在底部區(qū)域被消耗殆盡所致.MLVSS在沿程高度為50cm處有小幅升高,這與劉俊峰等[25]研究的沿程生物量與有機(jī)物濃度呈正相關(guān),沿水流方向均是下降態(tài)勢的結(jié)果有所差異性.分析原因,一方面是此處水力剪切較為適當(dāng),既能吹脫老化的生物膜,促進(jìn)微生物的生長富集,又不會破壞原本的生物膜導(dǎo)致生物大量流失.另一方面,底部相對充足的有機(jī)物與交替的好氧/缺氧環(huán)境,有利于刺激大量活性生物代謝繁殖.

2.3 生物活性變化規(guī)律

如圖5a所示,填料層高在a區(qū)段(10～50cm)OUR值分別為6.64,4.75, 3.25mg/(g·h),降幅較大;結(jié)合該區(qū)域生物量的監(jiān)測結(jié)果推測,濾料上附載微生物以兼性硝化菌以及反硝化菌為主,在飽和的溶解氧模擬水中檢測的OUR值呈下降態(tài)勢[26].濾料深度在b區(qū)段 (70～90cm)OUR值依次為3.51, 4.23mg/(g·h),又表現(xiàn)出小幅上升趨勢;在濾層末端c區(qū)段(110～ 150cm) OUR逐步降低,監(jiān)測結(jié)果為3.55, 3.26, 2.64mg/(g·h);由于出水端微生物較少,且可利用的有機(jī)物質(zhì)被消耗殆盡,進(jìn)而影響了生化反應(yīng)速率,好氧速率值降為最低[27].

TF為等位的TTC-脫氫酶活性與MLVSS比值

a為OUR;b為TF

由圖5b可知,底部填料區(qū)的脫氫酶活性最高,頂端附近生物活性較低,與OUR的監(jiān)測結(jié)果保持一致.值得注意的是,濾料深度在50cm處微生物好氧速率較低,但該段TTC-脫氫酶活性有所上升;這也可以推測出該段富集有兼氧/厭氧細(xì)菌,可進(jìn)行反硝化作用.此外,在近出水端130cm處, 活性有小幅上升,該結(jié)果與王曦曦等[28]的研究結(jié)果一致,即認(rèn)為是生物膜相對較薄,導(dǎo)致生物活性升高.

2.4 沿程硝化和反硝化速率

如圖6所示,就硝化速率而言,隨著填料層厚度的增加硝化速率逐步降低.沿程的硝化速率可大致分為a(10～70cm)和b(70～150cm)2個區(qū)段;在a階段,硝化速率均值為28.87mg/(kg·h),表明該段具有良好的硝化性能,是由于此處高氨氮濃度,富含溶解氧,使得生物膜中的硝化細(xì)菌得以穩(wěn)步增長,進(jìn)而硝化速率高.b段硝化速率相對于a段有較大幅度下降,均值僅為3.86mg/(kg·h),表明此段的硝化反應(yīng)不明顯,原因在于該段氨氮濃度較低,硝化細(xì)菌生長缺乏基質(zhì),致使硝化速率減小.該現(xiàn)象也與沿程氨氮濃度的變化特征相符.

圖6 沿程硝化和反硝化速率分析

反應(yīng)器內(nèi)沿程反硝化速率與消化速率的變化情況不同,呈現(xiàn)出先升高再減小的過程,并在50cm處達(dá)到約31mg/(kg·h)的最高值.在濾層高度10～ 50cm處(c階段)反硝化速率均值為21.56mg/(kg·h);表明間歇曝氣耦合內(nèi)循環(huán)的操作條件在該區(qū)域為脫氮微生物提供了良好的基質(zhì)條件,使反硝化作用得以充分發(fā)揮.在70～140cm處(d階段)反硝化速率遞減直至最低0.13mg/(kg·h),基本喪失了反硝化作用.一方面是由于沿水流方向易于被生物利用的有機(jī)物逐漸被消耗,導(dǎo)致各生物濾池沿程反硝化速率逐漸下降,甚至在濾池末尾段速率基本趨于0;另一方面,出水端完全呈現(xiàn)好氧的環(huán)境,反硝化細(xì)菌難以富集,限制了反硝化的進(jìn)行.

除濾層高度50cm外,同位置的硝化速率始終優(yōu)于反硝化速率,說明系統(tǒng)內(nèi)部硝化反應(yīng)始終占優(yōu)勢,這也是系統(tǒng)最終脫氮效果良好效果的主要原因.結(jié)合圖4,系統(tǒng)內(nèi)部僅在沿程30～50cm的停曝氣階段存在一定的缺氧環(huán)境;加之氧的傳遞在生物膜內(nèi)形成溶解氧梯度,填料內(nèi)層因而存在微觀的缺氧環(huán)境,為反硝化菌富集提供了優(yōu)勢條件[28].

2.5 沿程微生物群落結(jié)構(gòu)物

圖7a表明,系統(tǒng)各樣本菌群數(shù)量均大于1.00%的優(yōu)勢菌群主要有Proteobacteria (變形菌門: 37.74%)、Bacteroidetes (擬桿菌門:22.29%)、Firmicutes (厚壁菌門:10.64%)、Planctomycetes (浮霉菌門:9.08%)、Acidobacteria (酸桿菌門:2.84%)等5種.

從脫氮細(xì)菌來看,Proteobacteria被認(rèn)為是BAF反應(yīng)器中的優(yōu)勢門,這一門廣泛分布于土壤、廢水和污泥中[29-30].該細(xì)菌在沿程A1～A3方向所占比例分別為47.56%、22.87%和42.87%,同樣保持著較高豐度.Nitrospirae是硝化作用的主要實(shí)踐者,Nitrospirae的存在說明了亞硝酸鹽氧化細(xì)菌的存在[31];沿程各取樣點(diǎn)的Nitrospirae占總細(xì)菌比例低,為0.32%～ 3.02%,僅在填料層的末端A3處有較高水平,分析原因可能是此段的DO較高,為其富集提供了有利條件.這與Ma等[32]研究結(jié)論類似,其認(rèn)為曝氣條件下,Nitrospirae是占優(yōu)勢的系統(tǒng)發(fā)育群.擬桿菌門和厚壁菌門是參與反硝化脫氮過程的主要菌種,二者常見于實(shí)際污水廠和模擬實(shí)驗研究的反應(yīng)器中[33-34].在本系統(tǒng)中厚壁菌門沿程豐度依次為7.91%、14.43%和9.57%,在填料層中部出現(xiàn)了峰值,這種變化趨勢與之前的研究類似[35],分析原因是中后層條件穩(wěn)定,氧氣和水力剪切擾動較小,為其富集創(chuàng)造了便利條件.系統(tǒng)的擬桿菌門沿程豐度依次為11.91%、32.05%和22.93%,變化情況與DO負(fù)相關(guān),在A2區(qū)域的溶解氧環(huán)境和相對充足的底物為其富集提供了有利環(huán)境,進(jìn)而該取樣點(diǎn)出現(xiàn)了峰值.間歇曝氣耦合內(nèi)循環(huán)的工況優(yōu)化會顯著改變生物膜中微生物的種群結(jié)構(gòu),尤其是在濾層50cm處有效提高厚壁菌門和擬桿菌門等反硝化菌的豐度.

圖7 沿程微生物群落分析

a門水平;b屬水平

由圖7b可知,在屬水平上,沿程相對豐度均值大于2.00%的優(yōu)勢菌群主要有(弓形桿菌屬:3.53%)、(叢毛單胞菌屬:3.11%)、(紫單細(xì)胞菌屬:4.78%)、(3.41%)、(2.43%)等5種.此外,同樣發(fā)現(xiàn)了能夠進(jìn)行缺氧代謝的細(xì)菌,如、和表明即使在反應(yīng)器的曝氣區(qū)也存在著缺氧的環(huán)境.已有研究證明,和細(xì)菌屬在缺氧條件下可進(jìn)行反硝化[37].而傳統(tǒng)的BAF受限于內(nèi)部環(huán)境條件,難以富集缺氧代謝和反硝化功能細(xì)菌,王琳等[28]的研究指出Biostyr系統(tǒng)菌群并未檢測出能夠反硝化的優(yōu)勢細(xì)菌,該結(jié)果也可佐證上述結(jié)論.

綜上,間歇曝氣耦合內(nèi)循環(huán)濾池內(nèi)具有豐富的微生物群落,且硝化和反硝化等功能性種群豐度賦存較為明顯,結(jié)合出水回流、間歇曝氣的運(yùn)行方式,為反硝化細(xì)菌的代謝提供良好的基質(zhì)條件,強(qiáng)化了系統(tǒng)的反硝化脫氮效率,實(shí)現(xiàn)了單級BAF反應(yīng)器對總氮的高效去除.

3 結(jié)論

3.1 系統(tǒng)沿填料層高度方向水中NH4+-N、TN遞減,而NO3--N逐漸積累,但 50cm處NO3--N濃度有小幅度的小降,表明此處的反硝化過程占優(yōu).進(jìn)水在沿程出水過程中類蛋白熒光強(qiáng)度逐漸減弱,最終出水并未檢測到類蛋白峰.

3.2 在沿程30～70cm區(qū)段具有強(qiáng)化反硝化作用的優(yōu)勢溶解氧環(huán)境和充沛的有機(jī)物;此外,該段的生物數(shù)量也明顯優(yōu)于其它區(qū)域.生物膜沿程的OUR和TTC-脫氫酶活性沿水流方向逐漸降低,在濾池深度50cm附近出現(xiàn)了峰谷.該段的OUR速率低但脫氫酶活性高,表明低DO區(qū)主要進(jìn)行反硝化脫氮.反硝化速率在濾料底部區(qū)域較高.

3.3 16S rRNA高通量測序分析顯示:系統(tǒng)在門水平上涉及反硝化功能的微生物有較高的豐度,主要有Firmicutes (10.64%)和Bacteroidetes (22.29%);在屬水平上也明顯存在反硝化功能的(3.11%)和(2.43%).

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Intermittent aeration-internal circulation biological filter performance and biofilm characteristics.

REN Wu-ang1, CAO Feng-feng1, JU Kai1, JIN Peng-kang2, LI Si-min3, CHAI Bei-bei4,5*, LEI Xiao-hui5

(1.School of Architecture and Civil Engineering, Xi’an University of Science and Technology, Xi’an 710054,China；2.School of Human Settlement Environment and Civil Engineering, Xi’an Jiaotong University, Xi’an 710049,China；3.Hebei Water Pollution Control and Ecological Restoration Technology Innovation Center, Handan 056038, China；4.School of Water Conservancy and Hydroelectric Power, Hebei University of Engineering, Handan 056038, China；5.Hebei Key Laboratory of Intelligent Water Conservancy, Handan 056038, China)., 2022,42(2)：629～636

The mechanism of enhanced denitrification by intermittent aeration-coupled internal circulation biofiltration is still not clear. We therefore investigated the pollutant removal in a biofiltration reactor. Several methods were used to analyze the biomass, biological activity, and nitrification and denitrification rates of the system, and the microbial population in the reactor was analyzed. The intensity of protein-like fluorescence gradually decreased throughout the system, and no protein-like peak was detected in the effluent. The decrease of NH4+-N along the 10-50cm section of the reactor did not cause a significant increase in NO3--N, and the NO3--N content decreased at 50cm. This section showed obvious denitrification. The dissolved oxygen and biomass levels throughout the system indicated an anoxic/anaerobic environment and significant denitrification. In addition, the low oxygen uptake rate (OUR) but high TTC-dehydrogenase activity at 50cm and the significantly higher denitrification rate compared to the nitrification rate indicated enhanced denitrification in this region. Based on 16S rRNA high-throughput sequencing analysis, the system had a higher abundance of microorganisms involved in denitrification at the phylum level, mainly Firmicutes (10.64%) and Bacteroidetes (22.29%). Denitrification was also evident at the genus level in(3.11%) and(2.43%). Our results suggest that the BAF system with intermittent aeration coupled with internal circulation enhanced denitrification in the bottom zone and thus improved the denitrification efficiency.

biofilter；intermittent aeration；internal circulation；pollutants；microbial response

X703.5

A

1000-6923(2022)02-0629-08

任武昂(1986-),男,陜西西安人,講師,博士,主要從事污水處理與資源化研究.發(fā)表論文10余篇.

2021-06-03

陜西省重點(diǎn)研發(fā)計劃(2019ZDLNY01-08);陜西省重點(diǎn)研發(fā)計劃(2020ZDLNY06-07);國家自然科學(xué)基金資助項目(NSFC 52070065);河北省自然科學(xué)基金創(chuàng)新研究群體(Grant No.E2020402074)

* 責(zé)任作者, 副教授, cbb21@163.com