安澤銘,丁 靜,高歆婕,彭永臻

AOA系統(tǒng)厭氧時(shí)間和溶解氧對(duì)內(nèi)源反硝化脫氮速率的影響

安澤銘,丁 靜,高歆婕,彭永臻*

(北京工業(yè)大學(xué),城鎮(zhèn)污水深度處理與資源化利用國(guó)家工程實(shí)驗(yàn)室,北京市污水脫氮除磷處理與過(guò)程控制工程技術(shù)研究中心,北京 100124)

為了探索提升基于內(nèi)源反硝化的厭氧/好氧/缺氧(Anaerobic/Oxic/Anoxic,AOA)工藝脫氮效率的方法,本研究分別考察了前置厭氧時(shí)間和好氧階段溶解氧(DO)對(duì)內(nèi)源反硝化脫氮速率的影響.結(jié)果表明:在進(jìn)水COD濃度為155.1mg/L時(shí),厭氧時(shí)間為60min,缺氧階段內(nèi)源反硝化速率(EDNR)最高;在不同的進(jìn)水COD條件下,控制適當(dāng)?shù)膮捬鯐r(shí)間,當(dāng)內(nèi)碳源中的聚羥基烷酸酯(PHAs)積累量達(dá)到峰值時(shí),EDNR最高; EDNR受到好氧階段DO過(guò)量或不足的影響,當(dāng)DO控制為1mg/L時(shí),EDNR最高.通過(guò)厭氧時(shí)間優(yōu)化與DO控制可將EDNR分別提高31.7％,18.4%.本研究為AOA工藝提高后置缺氧階段EDNR提供了可行策略,有利于AOA工藝設(shè)計(jì)與運(yùn)行策略優(yōu)化.

生物脫氮；內(nèi)源反硝化速率；厭氧時(shí)間；溶解氧

目前,傳統(tǒng)污水處理廠在處理低碳氮比(C/N)城市生活污水時(shí)面臨深度脫氮的瓶頸,由于缺乏反硝化所需的碳源導(dǎo)致處理效率受限,通過(guò)投加碳源可以提高處理效果,但同時(shí)也增加了污水處理廠成本[1-2].以厭氧/缺氧/好氧(A2/O)工藝為主的前置反硝化工藝,將好氧池中的混合液部分回流至缺氧池,利用原水中的有機(jī)物通過(guò)反硝化作用脫氮,但是其效果受到硝化液回流量的限制.通過(guò)提升回流量來(lái)提高處理效果,不僅會(huì)增加污水處理能耗,并且回流的硝化液中含有的大量溶解氧(DO)會(huì)影響缺氧環(huán)境與反硝化效果[3].而后置反硝化工藝?yán)碚撋显谔荚闯渥愕那闆r下能夠?qū)崿F(xiàn)完全的氮去除.然而后置反硝化往往缺乏碳源,難以實(shí)現(xiàn)經(jīng)濟(jì)高效的氮去除.近年來(lái),關(guān)于AOA工藝的提出與研究為后置反硝化脫氮提供了新的思路[4-6].

采用AOA工藝進(jìn)行脫氮的原理為:有機(jī)物在厭氧階段被微生物貯存為內(nèi)碳源進(jìn)行去除,能夠減少碳源在好氧階段的浪費(fèi);在好氧階段進(jìn)行硝化作用將氨氮轉(zhuǎn)化為硝酸鹽氮或亞硝酸鹽氮;最后在后置缺氧階段,液相中無(wú)外碳源的情況下微生物利用厭氧貯存的內(nèi)碳源,包括:糖原(Gly)和聚羥基烷酸酯(PHAs),兩者聯(lián)合驅(qū)動(dòng)內(nèi)源反硝化實(shí)現(xiàn)脫氮[7].在EBPR系統(tǒng)的缺氧階段,PHAs和Gly均可以作為反硝化的碳源[8].動(dòng)態(tài)的好氧/缺氧交替系統(tǒng)在缺氧階段優(yōu)先利用PHAs作為電子受體進(jìn)行反硝化,當(dāng)其儲(chǔ)備耗盡時(shí),微生物會(huì)利用Gly維持生長(zhǎng)代謝,從而進(jìn)行反硝化脫氮[8-9].之前的研究表明,AOA工藝能夠充分利用原水中的碳源,適合低C/N生活污水深度脫氮,并且由于后置反硝化工藝特點(diǎn),能夠穩(wěn)定實(shí)現(xiàn)超過(guò)90%的總氮去除效果[3].

然而相較于外源反硝化,內(nèi)源反硝化速率(EDNR)較低,理論上需要較長(zhǎng)的缺氧水力停留時(shí)間或較大的缺氧區(qū)體積,這增加了污水處理廠的建設(shè)成本,從而限制了該工藝的應(yīng)用[10].Wang等[11]研究發(fā)現(xiàn)適當(dāng)?shù)膮捬鯐r(shí)間有利于強(qiáng)化系統(tǒng)中磷的釋放和內(nèi)碳源的貯存,從而實(shí)現(xiàn)了在不添加外碳源的情況下同步脫氮除磷,Hu等[12]在SBR反應(yīng)器AOA運(yùn)行模式下發(fā)現(xiàn)低氧曝氣和間歇曝氣在維持短程硝化和好氧顆粒污泥方面發(fā)揮了重要作用,同時(shí)對(duì)硝化性能和內(nèi)碳源的轉(zhuǎn)化有一定影響,減少了內(nèi)碳源在好氧階段的消耗.因此,能否通過(guò)優(yōu)化厭氧時(shí)間以及控制DO提高EDNR,從而強(qiáng)化脫氮效果值得進(jìn)一步探究.

本研究以實(shí)際生活污水為研究對(duì)象,分別探究了AOA運(yùn)行模式中的前置厭氧階段對(duì)內(nèi)碳源貯存及其對(duì)后置缺氧階段EDNR的影響.以及好氧階段的DO對(duì)內(nèi)碳源消耗與轉(zhuǎn)化的影響,進(jìn)而對(duì)后置缺氧階段EDNR產(chǎn)生的影響.通過(guò)優(yōu)化厭氧與好氧階段的運(yùn)行參數(shù),以期提高內(nèi)源反硝化脫氮速率,討論了本優(yōu)化策略在污水處理廠中的應(yīng)用潛力,為AOA工藝的運(yùn)行優(yōu)化提供研究思路與應(yīng)用基礎(chǔ).

1 材料與方法

1.1 試驗(yàn)用水與接種污泥

試驗(yàn)用水取自北京工業(yè)大學(xué)西校區(qū)家屬區(qū)的實(shí)際生活污水,屬于典型的低C/N污水.試驗(yàn)所用活性污泥取自實(shí)驗(yàn)室長(zhǎng)期運(yùn)行的AOA連續(xù)流反應(yīng)器缺氧區(qū)末端[7],污泥濃度MLSS為5000～6000mg/L.

1.2 試驗(yàn)裝置與方法

圖1 實(shí)驗(yàn)裝置1

1.2.1 探究不同厭氧時(shí)間對(duì)EDNR的影響 為探究不同厭氧時(shí)間下后續(xù)缺氧階段的EDNR,設(shè)計(jì)了如下試驗(yàn):在厭氧條件下,將經(jīng)3次蒸餾水沖洗的1.1L污泥與同體積的生活污水混合,再通入N2去除DO后進(jìn)入?yún)捬踉囼?yàn)裝置(圖1).隨后分別經(jīng)過(guò)45min、60min、90min、180min的厭氧時(shí)間后,取0.5L泥水混合液,同樣進(jìn)行沖洗、通入N2后進(jìn)入缺氧試驗(yàn)裝置(圖1).在全過(guò)程中僅通過(guò)磁力攪拌裝置均勻攪拌,控制溫度為25℃,污泥濃度MLSS控制在3000mg/L左右.具體試驗(yàn)條件見(jiàn)表1.

1.2.2 探究不同COD濃度下厭氧時(shí)間對(duì)EDNR的影響 為探究不同COD濃度下厭氧時(shí)間對(duì)EDNR的影響,仍采用1.1L污泥,同時(shí)投加1.1L經(jīng)不同體積的蒸餾水稀釋后的生活污水,以實(shí)現(xiàn)不同的進(jìn)水COD濃度.其余操作條件與“1.2.1”相同,具體試驗(yàn)條件見(jiàn)表1.

1.2.3 探究好氧階段不同DO對(duì)EDNR的影響 為探究好氧階段不同DO對(duì)EDNR的影響,設(shè)計(jì)了如下試驗(yàn):通過(guò)控制厭氧階段時(shí)間均為90min,隨后進(jìn)入好氧裝置進(jìn)行曝氣(圖2),控制DO分別為:0.5,1,2,4mg/L,探究好氧階段不同DO對(duì)EDNR的影響.其余試驗(yàn)條件與1.2.1相同.具體試驗(yàn)條件見(jiàn)表1.

表1 試驗(yàn)條件

圖2 實(shí)驗(yàn)裝置2

1.3 計(jì)算公式

1.3.1 內(nèi)源反硝化速率 在缺氧條件下,微生物在外碳源匱乏的情況下可以利用內(nèi)碳源進(jìn)行反硝化.內(nèi)源反硝化速率計(jì)算公式如下:

式中:EDNR指內(nèi)源反硝化速率,mgN/(gVSS·h). NO3-1和NO3-2分別表示缺氧條件下反應(yīng)初始和結(jié)束時(shí)的NO3--N濃度,mg/L;MLVSS表示參與反應(yīng)的污泥濃度,mg/L.t1和t2分別指缺氧反應(yīng)初始和結(jié)束時(shí)的時(shí)間,h.

1.3.2 同步硝化反硝化率(SND率) 在好氧條件下,在氨氮被氧化為亞硝酸鹽氮和硝酸鹽氮,同時(shí)部分亞硝酸鹽氮和硝酸鹽氮被還原為氮?dú)?該過(guò)程為同步硝化反硝化.因此,SND率表示將好氧階段的總氮損失的效率,具體計(jì)算方法如下:

式中:SND率表示將好氧段的總氮損失的效率,%; NH4+eff、NO2-eff和NO3-eff分別指好氧出水的NH4+-N、NO2--N和NO3--N濃度,mg/L;NH4+Ai表示好氧進(jìn)水的NH4+-N濃度,mg/L.

1.3.3 厭氧階段的內(nèi)碳源儲(chǔ)存量(CODintra) 在厭氧階段,生活污水中的有機(jī)物部分被聚糖菌(Glycogen accumulating organisms,GAOs)和聚磷菌(Phosphorus accumulating organisms,PAOs)貯存為PHAs,伴隨著Gly和多聚磷酸鹽(僅PAOs)分解供能.該過(guò)程中聚磷菌分解1mol COD能夠合成1.33mol PHAs,同時(shí)0.5mol Gly和0.5mol多聚磷酸鹽分解提供能量;聚糖菌分解1mol COD能夠合成1.85mol PHAs,同時(shí)分解1.12mol Gly供能[13-14]. CODintra的計(jì)算公式如下:

1.4 試驗(yàn)分析方法

在實(shí)驗(yàn)過(guò)程中所取水樣均經(jīng)過(guò)定性濾紙過(guò)濾后再進(jìn)行水質(zhì)分析.NH4+-N、NO2--N、NO3--N、PO43--P采用流動(dòng)注射儀(Lachat Quick-Chem 8500型)進(jìn)行測(cè)定.COD采用連華快速測(cè)定法(重鉻酸鉀快速測(cè)定法)進(jìn)行測(cè)定.MLSS和MLVSS采用重量法測(cè)定.溫度、pH值和DO采用配備有 pH值和DO探頭的WTW Multi3420測(cè)定儀進(jìn)行在線檢測(cè).PHAs采用氣相色譜儀進(jìn)行測(cè)定[15-16], PHAs的成分通過(guò)聚β-羥基丁酸(PHB)和聚β-羥基戊酸(PHV)之和來(lái)表征.糖原采用蒽酮比色法進(jìn)行測(cè)定[17].

2 結(jié)果與討論

2.1 不同厭氧時(shí)間對(duì)內(nèi)源反硝化的影響

2.1.1 厭氧階段的內(nèi)碳源轉(zhuǎn)化途徑分析 由圖3可見(jiàn),在前45min內(nèi)PO43--P濃度升高,釋磷率為95.8%.同時(shí),伴隨著PHAs的合成,Gly與COD的降低,表明PAOs通過(guò)在分解多聚磷酸鹽(poly-P)為PO43--P和Gly糖酵解途徑中獲得能量,將外碳源吸收并轉(zhuǎn)化為PHAs[18].45～60min內(nèi),PO43--P濃度維持穩(wěn)定,而COD與Gly濃度繼續(xù)降低,PHAs濃度繼續(xù)升高.表明僅GAOs進(jìn)行內(nèi)碳源的貯存,其厭氧碳轉(zhuǎn)化模型與PAOs相似,但是沒(méi)有伴隨釋磷現(xiàn)象[11]. 60～180min內(nèi),COD與Gly濃度不再降低,PHAs濃度開(kāi)始降低.推測(cè)內(nèi)碳源的積累存在一定限度,且隨厭氧時(shí)間的繼續(xù)延長(zhǎng)內(nèi)碳源不僅不再貯存,還出現(xiàn)消耗現(xiàn)象.這可能是細(xì)菌通過(guò)降解細(xì)胞內(nèi)碳源補(bǔ)償饑餓[19].有研究表明,延長(zhǎng)厭氧時(shí)間有利于GAOs的內(nèi)碳源貯存,從而有利于內(nèi)源反硝化脫氮.然而,上述結(jié)果表明,厭氧時(shí)間也非越長(zhǎng)越好,過(guò)長(zhǎng)的厭氧時(shí)間消耗了內(nèi)碳源,可能會(huì)對(duì)后續(xù)的內(nèi)源反硝化脫氮產(chǎn)生不利影響.

由化學(xué)計(jì)量學(xué)公式可知,PRA與PAOs合成PHAs的量成正比,因此,PAOs合成PHAs的量隨厭氧時(shí)間的延長(zhǎng)先升高后基本保持不變,表明PAOs對(duì)內(nèi)碳源的貯存并非隨著厭氧時(shí)間的延長(zhǎng)而升高,也不會(huì)對(duì)內(nèi)碳源進(jìn)行降解[10].另外,厭氧階段的前60min內(nèi),?PHA/ ?Gly為1.60,這更接近于先前報(bào)道的糖原積累代謝(glycogen accumulating metabolism, GAM)模型值1.66,而不是多聚磷酸鹽積累代謝(polyphosphate accumulating metabolism,PAM)模型值2.66[13],這表明系統(tǒng)中部分PAOs的代謝途徑由PAM轉(zhuǎn)化為GAM,有利于強(qiáng)化后續(xù)內(nèi)源反硝化脫氮[20].因此,適當(dāng)?shù)膮捬鯐r(shí)間有利于加強(qiáng)GAM途徑的內(nèi)碳源貯存,從而有利于厭氧階段的總內(nèi)碳源貯存,綜上可見(jiàn)優(yōu)化系統(tǒng)的厭氧時(shí)間對(duì)內(nèi)碳源的貯存尤為重要.

圖3 厭氧階段的內(nèi)碳源轉(zhuǎn)化

2.1.2 厭氧時(shí)間對(duì)EDNR的影響 為了進(jìn)一步分析,在經(jīng)歷不同厭氧時(shí)間后,對(duì)缺氧階段EDNR進(jìn)行測(cè)定.如圖4(a)所示,缺氧階段EDNR隨厭氧時(shí)間的延長(zhǎng)先升高后降低,當(dāng)厭氧時(shí)間為60min時(shí)EDNR最高,為0.83mgN/(gVSS×h).這與厭氧結(jié)束時(shí)PHAs濃度的變化趨勢(shì)相同.進(jìn)一步進(jìn)行線性擬合(圖4(b))發(fā)現(xiàn),兩者呈現(xiàn)線性相關(guān),2=0.8273.表明厭氧時(shí)間過(guò)長(zhǎng)影響內(nèi)碳源的貯存同時(shí)會(huì)進(jìn)一步影響后續(xù)的EDNR.若控制厭氧階段在60min,PHAs濃度在最高時(shí)停止,則相比于厭氧時(shí)間為45min和90min,EDNR分別提高了17.7%和32.0%.

圖4 不同厭氧時(shí)間下的EDNR與PHAs濃度和厭氧階段EDNR與PHAs濃度的相關(guān)性

圖5 不同進(jìn)水COD下的EDNR與PHAs濃度的相關(guān)性及不同進(jìn)水COD下最佳厭氧時(shí)間和EDNR

控制厭氧階段時(shí)間有望提高EDNR,應(yīng)進(jìn)一步探究不同進(jìn)水COD濃度下最佳厭氧時(shí)間,闡明其規(guī)律,有助于優(yōu)化內(nèi)源反硝化系統(tǒng)的脫氮效果.如圖5所示,在不同的進(jìn)水COD濃度下,內(nèi)碳源(PHAs)貯存最高時(shí)對(duì)應(yīng)的厭氧時(shí)間不同,后續(xù)缺氧階段的EDNR也不同.并且隨著進(jìn)水COD濃度的提高, EDNR也有所提升,而最佳厭氧時(shí)間則縮短.進(jìn)而說(shuō)明系統(tǒng)的最佳厭氧時(shí)間因進(jìn)水有機(jī)負(fù)荷的波動(dòng)而變化,且進(jìn)水COD濃度較高時(shí),最佳厭氧時(shí)間較短,EDNR較快.但是都顯示出EDNR與PHAs濃度的正相關(guān)性.進(jìn)一步線性擬合發(fā)現(xiàn),兩者呈顯著正相關(guān)且相關(guān)系數(shù)均高于0.75,進(jìn)水COD濃度越高,相關(guān)性越強(qiáng).表明即使進(jìn)水COD濃度不同也同樣可使用PHAs濃度進(jìn)行厭氧時(shí)間設(shè)置的判斷.

在厭氧階段,PAOs和GAOs競(jìng)爭(zhēng)碳源,而PAOs并不表現(xiàn)脫氮功能.PAOs在厭氧階段貯存的PHAs需要Poly-P和Gly降解提供能量,同時(shí)在隨后的好氧或缺氧條件下消耗這部分貯存的PHAs以吸收磷[21].因而GAOs爭(zhēng)奪到更多的碳源用于貯存則更有利于內(nèi)源反硝化脫氮.由2.1.1研究結(jié)果可知, GAOs對(duì)內(nèi)碳源的積累往往比PAOs需要更長(zhǎng)的厭氧時(shí)間.這進(jìn)一步說(shuō)明了在PHAs濃度最高時(shí)與GAOs貯存內(nèi)碳源最多時(shí)保持一致,進(jìn)一步表明, PHAs濃度可作為在不同進(jìn)水COD濃度下選擇最佳厭氧時(shí)間的依據(jù)

2.2 不同DO濃度對(duì)內(nèi)源反硝化的影響

2.2.1 不同DO濃度對(duì)好氧階段內(nèi)碳源轉(zhuǎn)化的影響 AOA系統(tǒng)為常見(jiàn)的內(nèi)源反硝化系統(tǒng),經(jīng)歷前置厭氧后,好氧階段對(duì)碳源的影響值得進(jìn)一步探究.如圖6所示,探究了不同DO濃度下PHAs和Gly的沿程變化.好氧階段PHAs呈下降趨勢(shì),Gly呈上升趨勢(shì).在DO濃度為1mg/L時(shí),Gly合成量最高,PHAs降解量變化不大,Gly可能依賴更多外碳源貯存提供的中間體和ATP得到補(bǔ)充[22].在DO濃度為0.5mg/L時(shí),Gly合成速率最慢,合成量最少,不利于好氧階段內(nèi)碳源的儲(chǔ)存.同時(shí),在DO濃度分別為2mg/L和4mg/L時(shí),Gly合成量均有所降低,說(shuō)明DO過(guò)高或過(guò)低都會(huì)導(dǎo)致Gly合成受阻.因此,在AOA系統(tǒng)中,好氧段DO濃度為1mg/L時(shí)最有利于系統(tǒng)內(nèi)碳源儲(chǔ)存.

根據(jù)PAOs代謝模型,合成系統(tǒng)中Gly所需的PHAs含量遠(yuǎn)遠(yuǎn)高于實(shí)際PHAs的降解量,推測(cè)在好氧階段可能存在外碳源貯存,合成了Gly.進(jìn)而說(shuō)明在好氧階段有可能存在內(nèi)碳源積累的過(guò)程.因此好氧階段對(duì)于后續(xù)內(nèi)源反硝化效果同樣重要.同時(shí),在好氧段發(fā)生的同步硝化反硝化(SND)在污水脫氮中同樣發(fā)揮著重要作用[23],因此有必要同時(shí)結(jié)合好氧段SND和缺氧段EDNR進(jìn)一步研究分析.

圖6 不同DO濃度下PHAs和Gly的變化

2.2.2 不同DO濃度對(duì)SND及EDNR的影響 在AOA系統(tǒng)中,主要脫氮貢獻(xiàn)發(fā)生在好氧段和缺氧段,依靠好氧段的同步硝化反硝化作用和缺氧段的內(nèi)源反硝化作用協(xié)同脫氮[6-24].由圖7可見(jiàn),在低DO濃度(DO￡1.0mg/L)條件下,SND率能保持較高水平,原因是通過(guò)硝化作用與吸磷作用的競(jìng)爭(zhēng)在絮凝污泥微環(huán)境中為反硝化細(xì)菌提供DO梯度來(lái)觸發(fā)SND[25],還有文獻(xiàn)表明低DO濃度能有效提高好氧階段初期的SND[26-27].但是在DO濃度為0.5mg/L時(shí),EDNR僅為0.09mgN/(gVSS·h),推測(cè)原因可能是內(nèi)源反硝化菌的活性受到抑制,因此DO濃度為0.5mg/L不利于AOA系統(tǒng)的整體脫氮.高DO(DO32.0mg/L)濃度下EDNR較高,但是SND率較低,原因可能是由于缺乏微氧環(huán)境導(dǎo)致同步硝化反硝化難以發(fā)生[23].在DO濃度為1mg/L時(shí),好氧段SND率和缺氧段EDNR相比于其他DO濃度均為最高值, EDNR可達(dá)0.58mgN/(gVSS·h),可見(jiàn)該DO濃度是最有利于AOA系統(tǒng)脫氮的條件.

圖7 不同DO濃度下SND率及總氮損失和EDNR

2.3 實(shí)際意義

在實(shí)際污水處理廠中,進(jìn)水的COD濃度因季節(jié)變化而波動(dòng),微生物群落也隨著操作條件的變化而變化.雖然污水處理廠在不同時(shí)期的最佳厭氧時(shí)間可能不同,但它可以沿程監(jiān)測(cè)PHAs濃度進(jìn)行調(diào)控.在采用SBR工藝的污水處理廠中,當(dāng)PHAs濃度達(dá)到峰值時(shí),控制厭氧階段結(jié)束.圖8所示為本研究?jī)?yōu)化策略在AOA工藝實(shí)際污水處理廠的應(yīng)用.在該連續(xù)流工藝中,生化池進(jìn)水分別通過(guò)厭氧區(qū)、好氧區(qū)、缺氧區(qū)后進(jìn)入二沉池,二沉池污泥一方面回流至厭氧區(qū)維持系統(tǒng)污泥濃度,一方面回流至缺氧區(qū)強(qiáng)化內(nèi)源反硝化.依據(jù)本試驗(yàn)研究結(jié)果,可在厭氧區(qū)和好氧區(qū)之間建立一個(gè)可任意切換厭氧/好氧的復(fù)合區(qū),該區(qū)域的狀態(tài)可根據(jù)PHAs的濃度進(jìn)行切換.當(dāng)PHAs濃度在可切換區(qū)之前達(dá)到最高時(shí),可將其轉(zhuǎn)化為好氧區(qū).如果PHAs濃度持續(xù)增加,則可切換區(qū)將繼續(xù)作為厭氧區(qū)攪拌.根據(jù)可切換區(qū)域的體積和數(shù)量進(jìn)行靈活調(diào)整.這樣即可通過(guò)直接或間接的方式對(duì)最佳厭氧停留時(shí)間進(jìn)行靈活調(diào)整來(lái)應(yīng)對(duì)不同時(shí)期的水質(zhì)波動(dòng).同時(shí)在好氧區(qū)實(shí)時(shí)監(jiān)測(cè)DO濃度,保證氨氮被完全硝化的前提下調(diào)節(jié)曝氣量從而控制合適的DO濃度.通過(guò)以上聯(lián)合調(diào)控,可以提高AOA工藝的運(yùn)行效果,進(jìn)而有效節(jié)約污水處理廠的能源和成本,提高處理效率.

圖8 本研究?jī)?yōu)化策略在AOA工藝實(shí)際污水處理廠的應(yīng)用

3 結(jié)論

3.1 厭氧時(shí)間對(duì)內(nèi)碳源貯存和EDNR有重要影響.進(jìn)水水質(zhì)為生活污水時(shí),在厭氧時(shí)間為60min時(shí)的PHAs和CODintra貯存量最高.且PHAs與EDNR呈正相關(guān),當(dāng)PHAs達(dá)到峰值時(shí)EDNR最高.

3.2 不同COD濃度下,所對(duì)應(yīng)的最佳厭氧時(shí)間不同,但PHAs與EDNR均有較高的相關(guān)性(2>0.75). PHAs濃度可以作為在不同進(jìn)水COD濃度下選擇最佳厭氧時(shí)間的依據(jù).

3.3 在厭氧時(shí)間一定時(shí),好氧段的DO為1mg/L時(shí)(結(jié)束時(shí)間以硝化反應(yīng)完成時(shí)為準(zhǔn)),SND率最高,后置缺氧階段的EDNR最高.

3.4 合理優(yōu)化厭氧時(shí)間、控制DO濃度可以有效提高EDNR,基于內(nèi)源反硝化脫氮的AOA工藝在低C/N城鎮(zhèn)生活污水處理領(lǐng)域具有重要實(shí)際意義和應(yīng)用前景.

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Effects of anaerobic duration and dissolved oxygen on endogenous denitrification rate in AOA system.

AN Ze-ming, DING Jing, GAO Xin-jie, PENG Yong-zhen*

(National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, China)., 2023,43(2)：667～674

The Anaerobic/Aerobic/Anoxic (AOA) process based on endogenous denitrification gained widespread attention in recent years with the benefits of carbon saving and consumption reduction. Nitrogen is mainly removed via the endogeous denitrification occurred in the post-anoxic phase of the AOA process. Therefore, increasing endogenous denitrification rate (EDNR) is the crucial to enhance the nitrogen removal efficiency. To explore the methods to improve the nitrogen removal efficiency of AOA process, the effects of the anaerobic duration and dissolved oxygen (DO) concentration in the aerobic phase on EDNR were investigated in this study. Results showed that the EDNR was the maximum when the anaerobic duration was 60min at the influent COD concentration of 155.1mg/L. Under different influent COD concentration, the accumulation of polyhydroxyalkanoates (PHAs) (a kind of intracellular carbon) reached the peak by controlling the appropriate anaerobic duration, and the EDNR was maximized. The EDNR was affected by excessive or insufficient DO in aerobic phase, and the highest EDNR was achieved when DO was controlled at 1mg/L. The EDNR was increased by 31.7% and 18.4% through anaerobic duration optimization and DO control, respectively. This paper provided a feasible strategy to enhance the EDNR in the post-anoxic phase of the AOA process, which is conducive to the optimization of the AOA process designs and operation strategies.

biological nitrogen removal；endogenous denitrification rate；anaerobic duration；dissolved oxygen control

X703

A

100-6923(2023)02-0667-08

安澤銘(1999-),男,河南安陽(yáng)人,北京工業(yè)大學(xué),碩士,主要從事生活污水脫氮除磷研究.

2022-07-20

廣州市產(chǎn)業(yè)領(lǐng)軍人才集聚工程項(xiàng)目(CYLJTD-201607);污水生物處理與過(guò)程控制技術(shù)北京市國(guó)際科技合作基地資助;北京市教委資助項(xiàng)目

* 責(zé)任作者, 教授, pyz@bjut.edu.cn