呂 嬌,樓菊青,徐 帆

反硝化型甲烷厭氧氧化(DAMO)系統(tǒng)pH值耦合模型研究

呂 嬌,樓菊青*,徐 帆

(浙江工商大學(xué)環(huán)境科學(xué)與工程學(xué)院,浙江 杭州 310018)

對3個(gè)具有不同優(yōu)勢菌種反應(yīng)器中厭氧氧化(DAMO)過程與pH值進(jìn)行動力學(xué)耦合,結(jié)果表明,在25℃,Anammox-DAMO混培系統(tǒng)最大脫氮速率、硝酸鹽初始抑制濃度和銨鹽初始抑制濃度分別為3.95mg/(L·d),182.63,196.40mg/L;Nitrate-DAMO系統(tǒng)最大脫氮速率、硝酸鹽初始抑制濃度分別為4.30mg/(L·d), 367.69mg/L;Nitrite-DAMO系統(tǒng)最大脫氮速率、亞硝酸鹽初始抑制濃度分別為4.04mg/(L·d), 293.35mg/L.脫氮速率均隨pH值增加先增大后減小,3個(gè)系統(tǒng)最佳脫氮pH值分別為7.5±0.2,7.2±0.2,7.8±0.2.脫氮?jiǎng)恿W(xué)表明,3個(gè)不同系統(tǒng)DAMO反應(yīng)過程均可用Haldane-pH值耦合模型描述. Nitrate-DAMO系統(tǒng)、Nitrite-DAMO系統(tǒng)脫氮過程還可用Monod-pH值耦合方程描述,Nitrate-DAMO系統(tǒng)細(xì)菌生長速率、硝酸鹽親和常數(shù)和抑制常數(shù)分別為1291.21cfu/(L·d), 295.23, 72.63mg/L;Nitrite-DAMO系統(tǒng)細(xì)菌生長速率、亞硝酸鹽親和常數(shù)和抑制常數(shù)分別為4040.42cfu/(L·d), 264.51, 5.02mg/L.

反硝化型甲烷厭氧氧化；脫氮性能；Hanldane方程；Monod方程；pH值;耦合模型

反硝化厭氧甲烷氧化(DAMO)過程,是以硝酸鹽或亞硝酸鹽為電子受體,以溫室氣體甲烷為唯一電子供體的甲烷厭氧氧化耦合反硝化過程[1-2].研究表明,該過程在濕地[3]、河流[4]、深水湖泊[5]等大多數(shù)淡水沉積物深層和水稻田中均存在,是自然界偶聯(lián)碳氮循環(huán)的關(guān)鍵環(huán)節(jié)[6].主導(dǎo)該過程的功能微生物主要包括NC10門細(xì)菌的‘’()[1]和隸屬于厭氧甲烷氧化古菌(ANME)中的一個(gè)簇ANME-2d的‘’()[2].DAMO過程在自然環(huán)境中也常見與厭氧氨氧化(Anammox)過程共存,兩者可能會爭奪NO2-,但也有可能會形成一種協(xié)同作用[7]: Anammox細(xì)菌消耗NO2-使其轉(zhuǎn)化為NO3-,而后DAMO微生物還原NO3-[8].

數(shù)學(xué)模型是深入了解生物反應(yīng)過程, 幫助和支持生物處理系統(tǒng)設(shè)計(jì)以及參數(shù)優(yōu)化強(qiáng)有力的工具,現(xiàn)已被廣泛應(yīng)用于廢水處理過程[9-10]. Ni等[11]對Anammox脫氮?jiǎng)恿W(xué)模型的評價(jià)表明,格勞(Grau)二級基質(zhì)去除模型和改進(jìn)的斯托弗-金坎農(nóng)(Stover-Kincannon)模型較一級基質(zhì)去除模型、莫諾德(Monod)模型和康托斯(Contois)模型更適合描述Anammox脫氮過程;Rosenthal等[12]研究后發(fā)現(xiàn)Anammox細(xì)菌能夠耐受亞硝酸鹽濃度的升高,而亞硝酸鹽敏感性系數(shù)并不適用于Anammox細(xì)菌的生長建模;Hu等[13]基于Monod模型和擴(kuò)散反應(yīng)模型開發(fā)了一個(gè)-DAMO模型用于探討DAMO細(xì)菌的生長限制因素;Ni等[14]致力于模擬Anammox和DAMO微生物共培養(yǎng)系統(tǒng)模型,用以描述DAMO和Anammox微生物共培養(yǎng)系統(tǒng)生化過程.

目前未見有對硝酸鹽型反硝化甲烷厭氧氧化(Nitrate-DAMO)過程的模型探討.且已有的關(guān)于Nitrite-DAMO和Anammox的模型中也未考慮pH值這個(gè)對這些生化過程影響較大的因素.DAMO微生物與大多數(shù)傳統(tǒng)異養(yǎng)反硝化類細(xì)菌類似,更偏好弱堿性環(huán)境[15].Zhu等[7]研究發(fā)現(xiàn)當(dāng)pH值在5.9～7.4范圍內(nèi),DAMO系統(tǒng)活性與pH值呈正相關(guān).過往研究一般在pH值接近7.0的條件下培養(yǎng)DAMO微生物[2-3],過酸或過堿性環(huán)境可能會導(dǎo)致系統(tǒng)活性降低.然而目前未建立DAMO系統(tǒng)脫氮速率和系統(tǒng)內(nèi)pH值的耦合模型,本文以穩(wěn)定運(yùn)行2000多天的3個(gè)具有不同優(yōu)勢菌種的DAMO反應(yīng)器為研究對象,基于霍爾頓(Haldane)模型和Monod模型,建立pH值耦合模型,用以描述DAMO微生物和Anammox微生物混培系統(tǒng)、Nitrate-DAMO系統(tǒng)以及亞硝酸鹽型反硝化甲烷厭氧氧化(Nitrite-DAMO)系統(tǒng)的反應(yīng)動力學(xué)過程,探明電子受體與pH值對系統(tǒng)的協(xié)同影響,并確定該過程最佳脫氮速率和銨鹽、硝酸鹽、亞硝酸鹽對DAMO系統(tǒng)初始抑制濃度,為完善DAMO過程理論和提升系統(tǒng)性能提供參考.

1 材料與方法

1.1 試驗(yàn)材料

1.1.1 試驗(yàn)系統(tǒng) 3個(gè)含DAMO微生物的系統(tǒng)分別是:Anammox-DAMO系統(tǒng):以Nitrate-DAMO古菌(39.4%)和Anammox菌(45.8%)為優(yōu)勢菌種[16],以西溪河底泥、西湖底泥與農(nóng)田水稻土壤的混合污泥為接種物,供給CH4、NH4+、NO3-,反應(yīng)過程見圖1A.

Nitrite-DAMO系統(tǒng):以Nitrite-DAMO細(xì)菌(88.2%)為優(yōu)勢菌種[17],接種物與Anammox-DAMO系統(tǒng)相同,供給CH4、NO2-,反應(yīng)過程見圖1B.

Nitrate-DAMO系統(tǒng):以Nitrite-DAMO細(xì)菌(62.2%)和Nitrate-DAMO古菌(26.5%)為優(yōu)勢菌種[18],以西溪河底泥、杭州七格污水處理廠二沉池活性污泥與儲泥池厭氧消化污泥的混合污泥為接種物,供給CH4、NO3-,反應(yīng)過程見圖1C.

各試驗(yàn)系統(tǒng)內(nèi)部始終保持厭氧狀態(tài),結(jié)合經(jīng)高純N2曝氣30min的以去離子水為溶劑配制的新鮮營養(yǎng)液[19],KH2PO4、CaCl2×2H2O、MgSO4分別為0.05,0.30, 0.10g/L,微量元素液為1.25mL/L,利用0.1mol/L HCl或0.1mol/L NaOH使pH值維持在7.0±0.2,在25℃環(huán)境溫度下運(yùn)行穩(wěn)定.

A. Anammox-DAMO系統(tǒng);B. Nitrite-DAMO系統(tǒng);C. Nitrate-DAMO系統(tǒng)

1.1.2 試驗(yàn)裝置 如圖2,反應(yīng)器:直徑16cm,高30cm,有效容積3.5L.取樣口與排氣口均設(shè)有閥門,所有閥門關(guān)閉時(shí),反應(yīng)器呈全封閉狀態(tài),內(nèi)部環(huán)境厭氧.

圖2 試驗(yàn)裝置示意

a.排氣口;b. 頂蓋;c. 第一取樣口;d. 第二取樣口;e. 進(jìn)樣口;f. 攪拌子

1.2 試驗(yàn)方法

反應(yīng)器已連續(xù)運(yùn)行2547d,第1995～2367d的實(shí)驗(yàn)數(shù)據(jù)被用于校準(zhǔn)和驗(yàn)證本文建立的DAMO反應(yīng)過程動力學(xué)模型.第1995d開始作第1階段,pH值控制在5.5±0.20,將Anammox- DAMO、Nitrate-DAMO系統(tǒng)內(nèi)硝酸鹽濃度控制為(10.0±0.50)mg N/L, Nitrite-DAMO系統(tǒng)內(nèi)亞硝酸鹽濃度控制為(10.0± 0.50)mg N/L,試驗(yàn)周期為7d,此后逐步將Anammox- DAMO系統(tǒng)硝酸鹽濃度提升為(20.0±0.50), (30.0± 0.50), (50.0±0.50), (100.0±0.50), (150.0±0.50)mg N/L;Nitrate-DAMO系統(tǒng)硝酸鹽濃度提升為(20.0± 0.50), (30.0±0.50), (50.0±0.50), (250.0±0.50) mg N/L; Nitrite-DAMO系統(tǒng)亞硝酸鹽濃度提升為(20.0± 0.50), (30.0±0.50), (50.0±0.50)mg N/L.隨著生物反應(yīng)器性能的提高,在超過2054d的試驗(yàn)期間, Anammox-DAMO系統(tǒng)進(jìn)水硝酸鹽濃度從150.0mg N/L逐步提升至(250.0±0.50), (400.0±0.50), (500.0± 0.50), (800.0±0.50)mg N/L;Nitrate-DAMO系統(tǒng)進(jìn)水硝酸鹽濃度從250.0mg N/L逐步提升至(500.0±0.50), (750.0±0.50), (1000.0±0.50), (1250.0±0.50), (1500.0± 0.50)mg N/L;Nitrite-DAMO系統(tǒng)亞硝酸鹽濃度從50.0mg N/L逐步提升至(100.0±0.50), (200.0±0.50), (350.0±0.50),(500.0±0.50),(650.0±0.50),(800.0±0.50)mg N/L.自第2085d開始,將Anammox- DAMO系統(tǒng)內(nèi)銨鹽濃度控制為(10.0±0.50)mg N/L,試驗(yàn)周期為7d,逐步將Anammox-DAMO系統(tǒng)進(jìn)水銨鹽濃度提升為(20.0±0.50), (30.0±0.50),(50.0±0.50), (100.0± 0.50),(150.0±0.50),(250.0±0.50),(400.0±0.50),(500.0±0.50),(800.0±0.50)mg N/L.此后2、3、4、5階段控制pH值分別在6.0±0.20, 7.0±0.20, 8.0± 0.20, 8.5±0.20.

試驗(yàn)期間,每24h取水樣3.0mL,經(jīng)0.22μm微孔濾膜過濾后測定NH4+-N、NO3--N、NO2--N濃度以及pH值,同時(shí)監(jiān)測系統(tǒng)中甲烷含量.利用普析TU-1901雙光束紫外可見分光光度計(jì)測定NH4+- N、NO3--N、NO2--N的濃度[20].通過裝配有FID的氣相色譜儀(GC2030,島津)測定頂空甲烷氣體含量[21].利用梅特勒FG2便攜式pH值計(jì)監(jiān)測反應(yīng)器在試驗(yàn)期間的pH值.

1.3 反應(yīng)動力學(xué)模型

選用Haldane方程[式(1)][14]、Monod變型方程[式(2)、式(3)][13,22]為基礎(chǔ)模型,利用Origin軟件模擬氮素對DAMO過程的影響動力學(xué).

式中:max為系統(tǒng)的最大脫氮速率, mg/(L·d);為硝酸鹽、亞硝酸鹽、銨鹽濃度, mg/L;s為飽和系數(shù), mg/L;K為硝酸鹽、亞硝酸鹽、銨鹽對系統(tǒng)的初始抑制濃度,mg/L;max為微生物最大生長速率,cfu/(L·d);DA表示微生物產(chǎn)量系數(shù);DA為微生物活性生物量,u/L;(NO2)為微生物對亞硝酸鹽親和常數(shù), mg/L;'(NO2)為微生物對亞硝酸鹽抑制常數(shù),mg/L;(NO3)為微生物對硝酸鹽親和常數(shù),mg/L;'(NO3)為微生物對硝酸鹽抑制常數(shù), mg/L.

N-DAMO系統(tǒng)脫氮速率在酸性環(huán)境隨pH值升高而升高,在堿性環(huán)境隨pH值的升高而降低[23],因此pH值對N-DAMO系統(tǒng)脫氮速率的影響可以看作一個(gè)近似一段的正弦函數(shù)方程[式(4)].

式中:為系統(tǒng)內(nèi)pH值(取值范圍0.0～14.0),、、、均為固定系數(shù).

將式(1)、(2)、(3)與式(4)耦合建立反硝化型甲烷厭氧氧化系統(tǒng)脫氮速率-pH值耦合模型[式(5)、(6)、(7)]

2 結(jié)果與討論

2.1 Anammox-DAMO系統(tǒng)脫氮擬合分析

由圖3可知,在同等pH值條件下,0～800mg/L銨鹽、硝酸鹽影響Anammox-DAMO系統(tǒng)的脫氮速率均隨鹽濃度的增加呈先增加后下降趨勢;在同等鹽濃度條件下,5.5～8.5pH值影響下脫氮速率也隨pH值的增加先增加后下降.Anammox-DAMO系統(tǒng)脫氮速率擬合參數(shù)見表1.

由圖3a可知,Haldane-pH值耦合方程的擬合度(2)和殘差平方和(SSE)分別為0.890和9.559, Anammox-DAMO系統(tǒng)的最佳脫氮速率為3.74mg/ (L·d),硝酸鹽對系統(tǒng)的初始抑制濃度為182.63mg/L, 0～800mg/L NO3--N條件下系統(tǒng)脫氮速率符合Haldane-pH值方程.由圖3b可知,Haldane-pH值耦合方程的2和SSE分別為0.867和12.330, Anammox-DAMO系統(tǒng)的最佳脫氮速率為3.95mg/ (L·d),銨鹽對系統(tǒng)的初始抑制濃度為196.40mg/L,0～ 800mg/L NH4+-N影響下系統(tǒng)脫氮速率也符合Haldane-pH值方程.

由圖3可知,硝酸鹽濃度高于182.63mg/L,銨鹽濃度高于196.40mg/L將限制DAMO古菌和Anammox細(xì)菌的生長,最佳鹽濃度是圖中擬合曲面的最高點(diǎn).研究表明[24-25],隨著鹽度的增加,反硝化速率會受到抑制.因此當(dāng)銨鹽和硝酸鹽濃度持續(xù)升高達(dá)到一定濃度后,Anammox-DAMO反應(yīng)器反硝化速率下降.本文擬合結(jié)果中,硝酸鹽對Anammox- DAMO系統(tǒng)脫氮抑制濃度為182.63mg/L,而Li等[26]發(fā)現(xiàn)在50～400mg/L,硝酸鹽濃度增加對Anammox過程暫沒有抑制作用,這可能是由于Li等[26]所使用的上流式污泥床-過濾器(UBF)反應(yīng)器內(nèi)微生物受到馴化,進(jìn)水硝酸鹽、銨鹽濃度(300～400mg/L)較高,Anammox菌的耐受性相應(yīng)提高;銨鹽影響下的脫氮速率擬合結(jié)果低于Ni等[11]研究當(dāng)銨濃度從210mg/L增加到380mg/L,氮負(fù)荷率(NLR)由0.43kg/ (m3×d)增加到0.72kg/(m3×d),反應(yīng)器對基質(zhì)濃度沖擊具有良好的耐受性.這可能是由于Anammox細(xì)菌細(xì)胞產(chǎn)率低(0.08～0.11g/g,以VSS/NH4+-N計(jì)),生長緩慢且在高細(xì)胞濃度(1010～1011個(gè)/mL)時(shí)才具有活性[27],本試驗(yàn)所用反應(yīng)系統(tǒng)內(nèi)污泥生物量較Ni等[11]生物量低,導(dǎo)致Anammox細(xì)菌活性相對較低.

a. NO3--N-pH值影響;b. NH4+-N-pH值影響

表1 Anammox-DAMO系統(tǒng)動力學(xué)參數(shù)

圖3中所示pH值對Anammox-DAMO系統(tǒng)脫氮速率的影響可以近似看作一段正弦曲線方程,在酸性范圍內(nèi)隨pH值增大,脫氮速率逐步提升, 7.5± 0.2達(dá)到最佳脫氮速率,在堿性范圍內(nèi)隨pH值增大,脫氮速率逐漸受到抑制.Achlesh等[28]通過構(gòu)建二維等高線圖和三維響應(yīng)面圖可視化溫度和酸堿度對Anammox系統(tǒng)的交互影響結(jié)果表明, Anammox系統(tǒng)最佳pH值8.0～8.5,相較本文擬合結(jié)果更大,證明在Anammox-DAMO體系中,脫氮速率受DAMO古菌與Anammox菌共同作用,因此推測DAMO古菌更傾向于酸性環(huán)境,這與Lou等[17]推論相似.研究表明,游離氨(FA)對厭氧氨氧化系統(tǒng)有負(fù)面影響[29],且FA與pH值有關(guān)[21].本研究中堿性條件(7.0～8.5)下,隨著pH值升高,FA濃度升高,脫氮速率下降.當(dāng)pH=8.5,氨氮濃度為87.61mg/L時(shí),FA濃度為13.34mg/L,此時(shí)脫氮速率不到最大脫氮速率的一半,而在酸性條件下(pH值5.5～7.0),對脫氮速率進(jìn)行單因素方差分析發(fā)現(xiàn)并無顯著性差異.說明在堿性條件下, Anammox- DAMO系統(tǒng)限制性抑制因子是FA.而在酸性條件下,抑制效果與FA濃度無關(guān),只與離子化氨氮的濃度相關(guān),離子化氨氮是限制性抑制因子.這與文獻(xiàn)報(bào)道的最佳pH值范圍(7.0～8.5)一致[30].

2.2 Nitrate-DAMO系統(tǒng)脫氮擬合分析

由圖4可見,在相同pH值條件下,0～1500mg/L硝酸鹽影響Nitrate-DAMO系統(tǒng)的脫氮速率隨硝酸鹽濃度的增加呈先增加后下降趨勢;在相同硝酸鹽條件下, pH值5.5～8.5范圍內(nèi)脫氮速率也隨pH值的增加先增加后下降.Nitrate-DAMO系統(tǒng)脫氮速率擬合參數(shù)見表2.

由圖4a可知,Haldane-pH值耦合方程的2和SSE分別為0.823和12.098, Nitrate-DAMO系統(tǒng)的最佳脫氮速率為4.30mg/(L·d),硝酸鹽對系統(tǒng)的初始抑制濃度為367.69mg/L,0～1500mg/L NO3--N條件下系統(tǒng)脫氮速率符合Haldane-pH值方程.由圖4b可知,Monod-pH值耦合方程2和SSE分別為0.822和12.098,Nitrate-DAMO系統(tǒng)的最佳脫氮速率為4.28mg/(L·d),細(xì)菌生長速率為1291.21cfu/(L·d),硝酸鹽親和常數(shù)和抑制常數(shù)分別為295.23,72.63mg/ L.0～1500mg/L NO3--N條件下系統(tǒng)脫氮速率也符合Monod-pH值方程.用這2個(gè)模型擬合后得到的結(jié)果吻合程度非常高.

a. Haldane-pH值耦合模型;b. Monod-pH值耦合模型

表2 Nitrate-DAMO系統(tǒng)動力學(xué)參數(shù)

由圖4可知,低濃度硝酸鹽(0～350mg/L)影響下,Nitrate-DAMO系統(tǒng)脫氮能力與鹽濃度呈正相關(guān),這與Li等[31]發(fā)現(xiàn)的亞熱帶河口沉積物中DAMO速率與沉積物NO3--N呈正線性關(guān)系相類似.當(dāng)硝酸鹽濃度高于367.69mg/L時(shí)對系統(tǒng)產(chǎn)生抑制效應(yīng), Nitrate-DAMO系統(tǒng)脫氮性能隨鹽濃度升高而降低.鹽度是決定DAMO細(xì)菌多樣性和豐度的關(guān)鍵因素,高鹽度對DAMO細(xì)菌和DAMO古菌的菌群結(jié)構(gòu)、豐度以及活性產(chǎn)生抑制作用[21,32].Shen等[4]觀察到鹽度與杭州灣沉積物中DAMO細(xì)菌的豐度和活性呈負(fù)相關(guān).這些結(jié)果證實(shí)了鹽度會對DAMO過程產(chǎn)生一定的負(fù)面影響.隨著鹽度的增加,DAMO過程脫氮速率下降,也可能歸因于鹽度對反硝化作用的抑制[26].Li等[31]研究發(fā)現(xiàn)鹽度也通過限制和抑制反硝化作用而間接影響DAMO系統(tǒng)反應(yīng)速率.本研究也發(fā)現(xiàn),當(dāng)硝酸鹽濃度達(dá)到一定濃度時(shí),也對系統(tǒng)產(chǎn)生了負(fù)面作用,Nitrate-DAMO系統(tǒng)脫氮速率受到抑制.硝酸鹽對Anammox-DAMO系統(tǒng)初始抑制濃度為182.63mg/L,對Nitrate-DAMO系統(tǒng)初始抑制濃度為367.69mg/L,這可能是由于DAMO細(xì)菌與DAMO古菌對高鹽廢水可以表現(xiàn)出更強(qiáng)的抗沖擊負(fù)荷能力[33].

由圖4可知,Nitrate-DAMO系統(tǒng)脫氮速率受pH值影響,先增高后降低,在pH7.2±0.2達(dá)到最佳. Nitrate-DAMO系統(tǒng)由62.2% Nitrite-DAMO細(xì)菌與26.5%Nitrate-DAMO古菌組成,脫氮速率受細(xì)菌與古菌協(xié)同影響,其中細(xì)菌起主導(dǎo)作用.與Nitrite-DAMO系統(tǒng)相比,由于偏弱酸性古菌影響, Nitrate- DAMO系統(tǒng)更適應(yīng)中性環(huán)境,脫氮速率達(dá)到最佳,與Anammox-DAMO系統(tǒng)相比, Nitrate- DAMO系統(tǒng)內(nèi)不含偏堿性的Anammox菌,最適pH值更低.

2.3 Nitrite-DAMO系統(tǒng)脫氮擬合分析

由圖5可見,在相同pH值條件下,在0～800mg/L亞硝酸鹽影響下,Nitrite-DAMO系統(tǒng)的脫氮速率隨亞硝酸鹽濃度的增加呈先增加后下降趨勢;在同等亞硝酸鹽條件下, pH值5.5～8.5時(shí),脫氮速率也隨pH值的增加先增加后下降.Nitrite-DAMO系統(tǒng)脫氮速率擬合參數(shù)見表3.

a. Haldane-pH值耦合模型;b. Monod-pH值耦合模型

表3 Nitrite-DAMO系統(tǒng)動力學(xué)參數(shù)

由圖5a可知,Haldane-pH值耦合方程的2和SSE分別為0.954和1.629, Nitrite-DAMO系統(tǒng)的最佳脫氮速率為3.61mg/(L·d),亞硝酸鹽對系統(tǒng)的初始抑制濃度為293.35mg/L, 0～800mg/L NO2--N條件下系統(tǒng)脫氮速率符合Haldane-pH值方程.由圖5b可知,Monod-pH值耦合方程的2和SSE分別為0.955和1.591,Nitrite-DAMO系統(tǒng)的最佳脫氮速率為4.04mg/(L·d),細(xì)菌生長速率為4040.42cfu/(L·d),亞硝酸鹽親和常數(shù)和抑制常數(shù)分別為264.51, 5.02mg/ L.0～800mg/L NO2--N條件下系統(tǒng)脫氮速率也符合Monod-pH值方程.

Nitrite-DAMO系統(tǒng)脫氮趨勢與其他研究的亞硝酸鹽對活性污泥中多種微生物的抑制范圍相比,表現(xiàn)出對高濃度亞硝酸鹽更強(qiáng)的抗沖擊負(fù)荷的能力.Dapena-Mora等[33]發(fā)現(xiàn),當(dāng)亞硝酸鹽濃度為5～40mg/L時(shí),會嚴(yán)重抑制厭氧氨氧化反應(yīng).亞硝酸鹽積累濃度達(dá)到140～700mg/L時(shí),會對反硝化細(xì)菌的活性產(chǎn)生抑制作用[34].由圖4b可知,Monod-pH值耦合模型能夠較好地描述Nitrite- DAMO系統(tǒng)脫氮過程,這與Hu等[13]擬合結(jié)果相似,且該模型可以在一定時(shí)間內(nèi)很好地預(yù)測廢水中亞硝酸鹽的濃度.亞硝酸鹽消耗率在達(dá)到最大值后下降[35-36]也與本文擬合結(jié)果相符.

如圖5,Nitrite-DAMO系統(tǒng)脫氮速率在各濃度下均隨pH值增大先提升后降低,在7.8±0.2達(dá)到最佳.這與He等[21]的擬合結(jié)果類似:pH7.6左右修正方程的最佳擬合值.與大多數(shù)異養(yǎng)反硝化菌類似, Nitrite-DAMO細(xì)菌更傾向于pH7.0～9.0的弱堿性環(huán)境[37].過往研究對于N-DAMO的培養(yǎng)大多保持在6.8～7.6[38-39],7.6左右的pH值脫氮速率優(yōu)于7.0,以上結(jié)論均與本文擬合結(jié)果相符.He等[40]認(rèn)為,游離亞硝酸鹽氮(FNA)是反硝化過程的抑制因子.Chen等[41]發(fā)現(xiàn),當(dāng)pH8.0～8.9時(shí), FNA濃度較低,即使亞硝酸鹽氮濃度高達(dá)2000mg/L,也未對系統(tǒng)產(chǎn)生抑制作用.Puyol等[42]發(fā)現(xiàn),膨脹顆粒污泥床(EGSB)厭氧氨氧化工藝對pH值沖擊非常敏感,亞硝酸鹽在反應(yīng)器中積累產(chǎn)生的高FNA濃度的抑制作用在酸性pH值沖擊后惡化了反應(yīng)器性能.本實(shí)驗(yàn)中當(dāng)溫度為25℃, pH6.0,亞硝酸鹽氮濃度74.72mg/L時(shí),FNA濃度74.72mg N/L,Nitrite- DAMO系統(tǒng)脫氮率不到最佳脫氮速率的1/2.單因素方差分析表明,在酸性條件下,亞硝酸鹽氮對體系的影響與FNA值有關(guān),FNA是限制性抑制因子.在堿性條件下,亞硝酸鹽對體系的抑制作用與FNA值無關(guān),此時(shí)離子化的亞硝酸鹽是限制性抑制因子.該結(jié)果與Puyol等[42]的研究結(jié)果一致.

3 結(jié)論

3.1 Anammox-DAMO、Nitrate-DAMO、Nitrite- DAMO系統(tǒng)耦合pH值反應(yīng)動力學(xué)皆符合Haldane- pH值方程.其中,Anammox-DAMO系統(tǒng)最大脫氮速率為3.95mg/(L·d),硝酸鹽初始抑制濃度為182.63mg/L,銨鹽初始抑制濃度為196.40mg/L; Nitrate-DAMO系統(tǒng)最大脫氮速率為4.30mg/(L·d),硝酸鹽初始抑制濃度為367.69mg/L;Nitrite-DAMO系統(tǒng)最大脫氮速率為4.04mg/(L·d),亞硝酸鹽初始抑制濃度為293.35mg/L.

3.2 Nitrate-DAMO系統(tǒng)和Nitrite-DAMO系統(tǒng)也符合Monod-pH值耦合模型,且擬合結(jié)果與Haldane-pH值方程擬合結(jié)果具有很高的吻合程度. Nitrate-DAMO細(xì)菌生長速率為1291.21cfu/(L·d),硝酸鹽親和常數(shù)為295.23mg/L,硝酸鹽抑制常數(shù)為72.63mg/L;Nitrite-DAMO細(xì)菌生長速率為4040.42cfu/(L·d),亞硝酸鹽親和常數(shù)為264.51mg/L,亞硝酸鹽抑制常數(shù)為5.02mg/L.

3.3 各系統(tǒng)脫氮速率受pH值影響皆呈一段正弦曲線分布,其中Anammox菌、Nitrite-DAMO細(xì)菌適應(yīng)弱堿環(huán)境,Nitrate-DAMO古菌更傾向于弱酸環(huán)境,在3類微生物的協(xié)同作用下Anammox-DAMO系統(tǒng)最佳脫氮速率pH值為7.5±0.2, Nitrate-DAMO系統(tǒng)為7.2±0.2,Nitrite-DAMO系統(tǒng)為7.8±0.2.

[1] Ettwig K F, Butler M K, Le Paslier D, et al. Nitrite-driven anaerobic methane oxidation by oxygenic bacteria [J]. Nature, 2010,464(7288): 543-548.

[2] Haroon M F, Hu S, Shi Y et al. Anaerobic oxidation of methane coupled to nitrate reduction in a novel archaeal lineage [J]. Nature, 2013,500(7464):567-570.

[3] Hu B L, He Z F, Geng S, et al. Cultivation of nitrite-dependent anaerobic methane-oxidizing bacteria: impact of reactor confgurafion [J]. Applied Microbiology and Biotechnology, 2014,98(18):7983-7991.

[4] Shen L D, Liu S, He Z F, et al. Depth-specific distribution and importance of nitrite-dependent anaerobic ammonium and methane- oxidising bacteria in an urban wetland [J]. Soil Biology and Biochemistry, 2015,83:43-51.

[5] Deutzmann J S, Stief P, Brandes J, et al. Anaerobic methane oxidation coupled to denitrification is the dominant methane sink in a deep lake [J]. Proceedings of the National Academy of Sciences of the United States of America, 2014,111(51):18273-18278.

[6] 翟 俊,馬宏璞,陳忠禮,等.濕地甲烷厭氧氧化的重要性和機(jī)制綜述 [J]. 中國環(huán)境科學(xué), 2017,37(9):3506-3514.

Zhai J, Ma H P, Chen Z L, et al. Review on the importance and mechanisms of anaerobic oxidation of methane in wetlands [J]. China Environmental Science, 2017,37(9):3506-3514.

[7] Zhu G, Jetten M S M, Kuschk P, et al. Potenial roles of anaerobic ammonium and methane oxidation in the nitrogen cycle of wetland ecosystems Interactions between denitrifying anaerobic methane oxidizing bacteria and anammox bacteria [J]. Applied Microbiology and Biotechnology, 2010,86(4):1043-1055.

[8] Strous M, Heijnen J J, Kuenen J G et al. The sequencing batch reactor as a powerful tool for the study of slowly gr owing anaerobic ammonium-oxidizing microorganisms [J]. Applied Microbiology and Biotechnology, 1998,50(5):589-596.

[9] Amand L, Carlsson, B. Optimal aeration control in a nitrifying activated sludge process [J]. Water Research, 2012,46(7):2101-2110.

[10] Young M N, Marcus A K, Rittmann B E. A Combined Activated Sludge Anaerobic Digestion Model (CASADM) to understand the role of anaerobic sludge recycling in wastewater treatment plant performance [J]. Bioresource Technology, 2013,136:196-204.

[11] Ni S Q, Sung S W, Yue Q Y, et al. Substrate removal evaluation of granular anammox process in a pilot-scale upflow anaerobic sludge blanket reactor [J]. Ecological Engineering, 2012,38(1):30-36.

[12] Rosenthal A, Ramalingam K, Beckmann K, et al. Experimental evaluation of the nitrite sensitivity coefficient in granular anammox biomass [J]. Water Science and Technology, 2013,68(9):2103-2110.

[13] Hu B L, He Z F, Cai C, et al. Mdodeling a nitrite-dependent anaerobic methane oxidation process: Parameters identification and model evaluation [J]. Bioresource Technology, 2013,147(2013):315-320.

[14] Ni B J, Yuan Z G, Hu S H, et al. Modeling of simultaneous anaerobic methane and ammonium oxidation in a membrane biofilm reactor [J]. Environmental Science & Technology, 2014,48(16):9540-9547.

[15] Shen L D, Huang Q, He Z F, et al. Vertical distribution of nitrite-dependent anaerobic methane-oxidising bacteria in natural freshwater wetland soils [J]. Applied Microbiology and Biotechnology, 2015,99(1):349-357.

[16] Lou J Q, Wang X L, Li J P, et al. The short- and long-term effects of nitrite on denitrifying anaerobic methane oxidation (DAMO) organisms [J]. Environmental Science and Pollution Research, 2018, 26(5):4777-4790.

[17] Lou J Q, Li J P, Wang X L, et al. Response mechanism of denitrifying anaerobic methane oxidation microorganisms to ammonia [J]. Environmental Chemistry, 2019,17(1):17-27.

[18] Li J P, Lou J Q, Lv J. The effect of sulfate on nitrite-denitrifying anaerobic methane oxidation (nitrite-DAMO) process [J]. Science of the Total Environment, 2020,731(3/4):139-160.

[19] Raghoebarsing A A, Pol A, Pas-Schoonen K T, et al. A microbial consortium couples anaerobic methane oxidation to denitrification [J]. Nature, 2006,440(7086):918-921.

[20] 魏復(fù)盛.水和廢水監(jiān)測分析方法(第4版) [M]. 北京:中國環(huán)境科學(xué)出版社, 2002.

Wei F S. Analytical methods for water and wastewater monitoring (4th Edition) [M]. Beijing: China Environmental Science Press, 2002.

[21] He Z F, Geng S, Shen L D, et al. The short- and long-term effects of environmental conditions on anaerobic methane oxidation coupled to nitrite reduction [J]. Water Research, 2015,68:554-562.

[22] 徐 富,繆恒鋒,任洪艷,等.低濃度廢水厭氧處理中不同動力學(xué)模型對比研究 [J]. 中國環(huán)境科學(xué), 2013,33(12):2184-2190.

Xu F, Miao H F, Ren H Y, et al. Comparative study of different kinetic models in anaerobic treatment low-strength wastewater [J]. China Environmental Science, 2013,33(12):2184-2190.

[23] Lou J Q, Lv J, Yang D Y, et al. Effects of environmental factors on nitrate-DAMO activity [J]. Water Air and Soil Pollution, 2020,231(6): 263-270.

[24] Rysgaard S, Sloth N P. Effects of salinity on NH4tadsorption capacity, nitrification, and denitrification in Danish estuarine sediments [J]. Estuaries and Coasts, 1999,22(1):21-30.

[25] Liu C, Hou L J, Liu M, et al. Coupling of denitrification and anaerobic ammonium oxidation with nitrification in sediments of the Yangtze Estuary: importance and controlling factors [J]. Estuar. Estuarine Coastal and Shelf Science, 2019,220:64-72.

[26] Li Z X, Peng Y Z. Biphasic effect of nitrate on anaerobic ammonium oxidation (anammox) and related kinetic modeling [J]. Chemosphere, 2020,238:124654.

[27] Isaka K, Date Y, Sumino T, et al. Growth characteristic of anaerobic ammonium-oxidizing bacteria in an anaerobic biological filtrated reactor [J]. Applied Microbiology and Biotechnology, 2006,70(1):47-52.

[28] Achlesh D, Pang C C, Kasturi D, et al. Statistical analysis to evaluate the effects of temperature and pH on anammox activity [J]. International Biodeterioration & Biodegradation, 2015,102:89-93.

[29] Coma M, Verawaty M, Pijuan M, et al. Enhancing aerobic granulation for biological nutrient removal from domestic wastewater [J]. Bioresource Technology, 2012,103(1):101-108.

[30] Strous M, Van Gerven E. Effects of aerobic and microaerobic conditions on anaerobic ammonium-oxidizing (Anammox) sludge [J]. Applied & Environmental Microbiology, 1997,63(6):2446-2448.

[31] Li X F, Laic D Y F, Gao D Z. Anaerobic oxidation of methane with denitrification in sediments of a subtropical estuary: Rates, controlling factors and environmental implications [J]. Journal of Environmental Management, 2020,273:111151.

[32] Chen J, Zhou Z C, Gu J D. Occurrence and diversity of nitrite dependent anaerobic methane oxidation bacteria in the sediments of the South China Sea revealed by amplification of both 16SrRNA and pmoA genes [J]. Applied Microbiology and Biotechnology, 2014, 98(12):5685-5696.

[33] Dapena-Mora A, Fernández I, Campos J L, et al. Evaluation of activity and inhibition effects on Anammox process by batch tests based on the nitrogen gas production [J]. Enzyme and Microbial Technology, 2007,40(4):859-865.

[34] Valenzuela E I, Prieto-Davó A, López-Lozano N E, et al. Anaerobic methane oxidation driven by microbial reduction of natural organic matter in a tropical wetland [J]. Applied Environment Microbiology, 2017,83(11):1-15.

[35] Ettwig K F, Shima S, Pas-Schoonen K T, et al. Denitrifying bacteria anaerobically oxidize methane in the absence of Archaea [J]. Environmental Microbiology, 2008,10(11):3164-3173.

[36] Vadivelu V M, Yuan Z G, Fux C, et al. The inhibitory effects of free nitrous acid on the energy generation and growth processes of an enriched nitrobacter culture [J]. Environmental Science and Technology, 2006,40(14):4442-4448.

[37] Kampman C, Hendrickx T L, Luesken F A, et al. Enrichment of denitrifying methanotrophic bacteria for application after direct low-temperature anaerobic sewage treatment [J]. Journal of Hazard Materials, 2012,227:164–171.

[38] Tang Y, Zhou C, Ziv-El M, et al. A pH-control model for heterotrophic and hydrogen-based autotrophic denitrification [J]. Water Research, 2011,45(1):232-240.

[39] Ettwig K F, van Alen T, van de Pas-Schoonen K T, et al. Enrichment and molecular detection of denitrifying methanotrophic bacteria of the NC10phylum [J]. Applied Environment Microbiology, 2009,75(11): 3656-3662.

[40] He S L, Zhang Y L, Niu Q G, et al. Operation stability and recovery performance in an Anammox EGSB reactor after pH shock [J]. Ecological Engineering, 2016,90:50-56.

[41] Chen S K, Juaw C K, Cheng S S. Nitrification anddenitrification of high-strength ammonium and nitritewastewater with biofilm reactors [J]. Water Science and Technology, 1991,23(79):1417-1425.

[42] Puyol J M, Carvajal-Arroyo R, Sierra-Alvarez J A. Nitrite (not free nitrous acid) is the main inhibitor of the anammox process at common pH conditions [J]. Biotechnology Letters, 2014,36(3):547-551.

pH coupling model of denitrifying anaerobic methane oxidation (DAMO) system.

LU Jiao, LOU Ju-qing*, XU Fan

(College of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310018, China)., 2022,42(2)：612～619

This study tried to couple the pH value with the reaction kinetics of the denitrification-type methane anaerobic oxidation process. The Denitrifying Anaerobic Methane Oxidation (DAMO) reaction rate and pH value were coupled and evaluated in three reactors with different dominant bacteria. The results show that the Anammox-DAMO maximum denitrification rate and the initial inhibition concentration of nitrate ammonium at 25℃ were 3.95mg/(L×d), 182.63mg/L and 196.40mg/L, respectively. The maximum denitrification rate and the initial inhibition concentration of nitrate in Nitrate-DAMO system were 4.30mg/(L×d) and 367.69mg/L, respectively. The maximum denitrification rate and the initial inhibition concentration of nitrite in Nitrite-DAMO system were 4.04mg/(L×d) and 293.35mg/L, respectively. The denitrification rate of the systems increased first and then decreased with the increase of pH. The optimum pH was 7.5±0.2, 7.2±0.2, 7.8±0.2, respectively. The bacterial growth rate, nitrate affinity constant and inhibition constant of Nitrate-DAMO system were 1291.21cfu/(L×d), 295.23mg/L and 72.63mg/L, respectively; The bacterial growth rate, nitrite affinity constant and inhibition constant of Nitrite-DAMO system were 4040.42cfu/(L×d), 264.51mg/L and 5.02mg/L, respectively. All the three DAMO systems could be described by the coupled Haldane pH model; the denitrification process of Nitrate-DAMO system and Nitrite-DAMO system could also be described by Monod-pH coupling equation.

denitrifying anaerobic methane oxidation；denitrification performance；Hanldane equation；Monod equation；pH；coupling model

X703

A

1000-6923(2022)02-0612-08

呂 嬌(1996-),女,浙江湖州人,浙江工商大學(xué)碩士研究生,主要研究方向?yàn)閺U水生物處理及資源化.發(fā)表論文1篇.

2021-05-21

浙江省自然科學(xué)基金資助項(xiàng)目(LY21D030003);浙江工商大學(xué)研究生科研創(chuàng)新基金一般項(xiàng)目(19020160029)

* 責(zé)任作者, 副教授, ljq7393@163.com