謝弘超,王曉東,王偉剛,張 姚,史 勤,王亞宜

曝氣策略調(diào)控CANON工藝降溫降基質(zhì)穩(wěn)定運(yùn)行

謝弘超,王曉東,王偉剛,張 姚,史 勤,王亞宜*

(同濟(jì)大學(xué)環(huán)境科學(xué)與工程學(xué)院, 污染控制與資源化研究國(guó)家重點(diǎn)實(shí)驗(yàn)室,上海 200092)

通過(guò)調(diào)整曝氣策略,研究了降溫降基質(zhì)(氨氮)運(yùn)行過(guò)程中實(shí)現(xiàn)全程自養(yǎng)脫氮(CANON)序批式生物膜反應(yīng)器(SBBR)穩(wěn)定運(yùn)行的可行性.結(jié)果表明,在中溫(35℃)高基質(zhì)[(446.47±43.77) mg NH4+-N/L]曝氣/停曝=60min/60min條件下,反應(yīng)器穩(wěn)定運(yùn)行223d,總氮去除負(fù)荷(TNRR)和總氮去除率(TNRE)分別為(0.49±0.07) kg N/(m3·d)和(84.3±4.6)%.溫度降至20~23℃,根據(jù)一個(gè)運(yùn)行周期內(nèi)NO2--N積累速率和去除速率之比調(diào)整曝氣工況為曝氣/停曝=40min/80min,運(yùn)行69d后TNRR和TNRE分別降至(0.43±0.04) kg N/(m3·d) 和 (69.5±5.7)%.而后逐步梯度降低基質(zhì)至(105.6±16.1) mg NH4+-N/L,采用相同策略分別調(diào)整曝氣/停曝時(shí)間為40min/80min、30min/90min和8min/32min,運(yùn)行93d后TNRR降至(0.16±0.02) kg N/(m3·d),TNRE升至(71.5±7.5)%.高通量測(cè)序結(jié)果從群落組成角度證實(shí)了降溫和降基質(zhì)過(guò)程中實(shí)施的曝氣調(diào)控策略維持了CANON系統(tǒng)脫氮功能菌的主導(dǎo)地位,亞硝酸鹽氧化菌NOB相對(duì)豐度一直被控制在0.1%以下.

CANON；生物膜反應(yīng)器；間歇曝氣工況；溫度；氨氮濃度；高通量測(cè)序

基于亞硝化的全程自養(yǎng)脫氮工藝(CANON)通過(guò)將短程硝化和厭氧氨氧化(Anammox)工藝耦合于一個(gè)反應(yīng)器中以實(shí)現(xiàn)全程自養(yǎng)脫氮[1-2].參與這兩個(gè)過(guò)程的功能菌分別為氨氧化菌(AOB)和厭氧氨氧化菌(AnAOB),均為自養(yǎng)型微生物[3].相比傳統(tǒng)硝化反硝化脫氮工藝,CANON工藝節(jié)省約60%的曝氣量,無(wú)需外加有機(jī)物且減少90%的污泥產(chǎn)量,極大降低污水處理能耗[4].目前CANON工藝主要適用于中溫(如>30℃)高氨氮(如>100mg NH4+-N/L)廢水處理,包括污泥消化液[5]和垃圾滲濾液[6-7]等,但其在市政污水處理的應(yīng)用仍存在若干問(wèn)題:(1)市政污水低氨氮濃度(30~100mg/L)[8]以及季節(jié)性溫度波動(dòng)(10~ 30℃),致使缺乏高游離氨(FA)?高游離亞硝酸(FNA)和中溫條件對(duì)亞硝酸鹽氧化菌(NOB)的抑制作用[9],維持穩(wěn)定的短程硝化較為困難[10-11].(2)AnAOB 最適生長(zhǎng)溫度為30~40℃[12],降溫會(huì)導(dǎo)致其活性顯著降低[13-15],溫度每降低5℃,其生長(zhǎng)速率下降30~ 40%[2],并最終導(dǎo)致反應(yīng)器失穩(wěn).這些問(wèn)題極大限制了其在低溫低基質(zhì)(氨氮)的市政污水處理工藝中的應(yīng)用.奧地利Strass污水處理廠利用水力旋流器分離污泥消化液自養(yǎng)脫氮處理系統(tǒng)中的AnAOB和AOB污泥,并將其補(bǔ)充到主流自養(yǎng)脫氮系統(tǒng)中,脫氮性能得到明顯提升[16],但同時(shí)也增加了污水處理廠長(zhǎng)期運(yùn)行管理的復(fù)雜程度.

目前已有較多研究利用序批式生物反應(yīng)器(SBR)成功啟動(dòng)了CANON工藝,并獲得了良好的脫氮效果[17-19],且多推薦采用間歇曝氣代替連續(xù)曝氣模式來(lái)提升反應(yīng)器脫氮穩(wěn)定性[20-21],但不合理的間歇曝氣工況往往會(huì)限制CANON優(yōu)勢(shì)的充分發(fā)揮[22]. 由于各研究中進(jìn)水水質(zhì)特征各異,致使提出的間歇曝氣工況不具備普適性,因此急需完善和優(yōu)化間歇曝氣策略以實(shí)現(xiàn)CANON工藝的穩(wěn)定運(yùn)行.

另一方面,AnAOB對(duì)氧氣十分敏感,超過(guò)0.5%空氣飽和度就會(huì)對(duì)其活性產(chǎn)生抑制[23-26].因此當(dāng)AnAOB與AOB共存于一個(gè)反應(yīng)體系時(shí),反應(yīng)器內(nèi)微生物需形成良好的生物膜生態(tài)位,即AOB分布于好氧表層,AnAOB分布于缺氧內(nèi)層以緩解曝氣過(guò)程溶解氧的抑制,同時(shí)利用基質(zhì)擴(kuò)散實(shí)現(xiàn)自養(yǎng)脫氮[27].由于生物膜(或顆粒污泥)具有微生物持留效果好的特性,尤其適用于富集AnAOB這類(lèi)生長(zhǎng)速率低、產(chǎn)率低的微生物[28].因此將生物膜應(yīng)用于CANON工藝中可在富集培養(yǎng)兩種功能菌的同時(shí),減小溶解氧等不利因素對(duì)AnAOB的影響,并減少AnAOB的流失.

本研究在SBR中投加機(jī)械強(qiáng)度較高的聚乙烯(PE)環(huán)作為生物填料,在中溫高基質(zhì)(35℃,3300mg NH4+-N/L)條件下接種高活性CANON污泥,啟動(dòng)運(yùn)行序批式生物膜反應(yīng)器(SBBR).隨后分階段逐步降低反應(yīng)器運(yùn)行溫度和基質(zhì)水平,同時(shí)根據(jù)一個(gè)運(yùn)行周期內(nèi)曝氣段NO2--N積累速率與停曝段NO2--N消耗速率之比進(jìn)行曝氣工況調(diào)整,以期實(shí)現(xiàn)降溫降基質(zhì)過(guò)程中自養(yǎng)脫氮系統(tǒng)的穩(wěn)定運(yùn)行,并結(jié)合不同階段生物膜中微生物群落組成的數(shù)據(jù),為CANON工藝在以低溫低氨氮為特點(diǎn)的城市污水處理領(lǐng)域的應(yīng)用推廣提供指導(dǎo)依據(jù).

1 材料與方法

1.1 實(shí)驗(yàn)裝置與運(yùn)行工況

SBBR實(shí)驗(yàn)裝置為圓柱形有機(jī)玻璃容器,有效容積2.5L,設(shè)計(jì)換水比為50%.利用恒溫循環(huán)水浴環(huán)控制反應(yīng)器反應(yīng)區(qū)溫度,液位計(jì)控制進(jìn)水量,自動(dòng)出水球閥控制出水.裝置內(nèi)部設(shè)攪拌器,攪拌速度為150r/min.填料選用PE環(huán)(規(guī)格K3,密度0.97~ 1.03kg/m3,比表面積300~700m2/m3),串聯(lián)后固定于反應(yīng)器攪拌槳上部,以減少攪拌槳在進(jìn)行混合攪拌時(shí)對(duì)填料掛膜的影響.填料填充率為40%.

反應(yīng)器共運(yùn)行385d.如表1所示,根據(jù)進(jìn)水氨氮濃度和溫度共分為3個(gè)階段.其中階段I代表中溫高基質(zhì),階段II代表常溫高基質(zhì),階段III代表常溫低基質(zhì),同時(shí),階段III又根據(jù)曝氣工況的不同分為A?B?C 3個(gè)小階段.階段I反應(yīng)器運(yùn)行周期初步設(shè)定為8h,其中進(jìn)水10min,間歇曝氣440min(曝氣/停曝時(shí)間= 60min/60min,共3個(gè)曝停周期,最后缺氧攪拌80min),沉淀20min,出水3min,閑置7min.曝氣階段 DO濃度控制在1.0~1.2mg/L.在日常反應(yīng)器維護(hù)中進(jìn)行pH值和DO的實(shí)時(shí)監(jiān)控,并及時(shí)做出工況調(diào)整.之后幾個(gè)階段則根據(jù)一個(gè)運(yùn)行周期內(nèi)曝氣段NO2--N積累速率與停曝段NO2--N消耗速率之比進(jìn)行曝氣工況調(diào)整(表1).

表1 反應(yīng)器不同階段的運(yùn)行工況

1.2 接種污泥與實(shí)驗(yàn)用水

本實(shí)驗(yàn)接種2L已在30~33℃馴化成功的CANON活性污泥, 污泥呈現(xiàn)部分顆粒和部分絮體形態(tài).接種后反應(yīng)器MLSS=3538mg/L,MLVSS= 3166mg/L.實(shí)驗(yàn)用水為人工配制的高氨氮廢水,進(jìn)水pH值控制在8.0~8.2.基質(zhì)濃度隨反應(yīng)器脫氮能力進(jìn)行調(diào)整,其主要成分如下(g/L): NH4HCO3(按需配制), NaHCO3[按需配制, NH4+:HCO3-=1:2, (mol/L):(mol/ L)]; KH2PO4, 0.025; CaCl2, 0.3; MgSO4·7H2O, 0.3; FeSO4·7H2O, 0.00625; Na2EDTA, 0.00625.微量元素濃縮液1.5mL/L.

微量元素濃縮液包括(g/L): H3BO3,0.014; CoCl2·2H2O,0.24;CuSO4·5H2O,0.25;ZnSO4·7H2O, 0.43, MnCl2·4H2O, 0.99; NiCl2·6H2O, 0.19; NaMoO4·2H2O, 0.22; Na2WO4·2H2O, 0.050; Na2SeO4·10H2O,0.21; EDTA,15.

1.3 分析測(cè)試方法

1.3.1 常規(guī)指標(biāo)檢測(cè)及計(jì)算方法 常規(guī)水質(zhì)指標(biāo)NH4+-N?NO3--N?NO2--N以及SS/VSS的檢測(cè)方法參考國(guó)家標(biāo)準(zhǔn)方法[29].DO使用WTW(Multi350i)DO測(cè)定儀監(jiān)測(cè).pH值使用WTW(Multi350i)pH值測(cè)定儀監(jiān)測(cè).

根據(jù)厭氧氨氧化代謝反應(yīng)方程式[30]以及對(duì)一個(gè)運(yùn)行周期內(nèi)各氮素存在形式(NH4+-N, NO2--N, NO3--N)的測(cè)定,分別計(jì)算出反應(yīng)器曝氣過(guò)程AOB氨氧化速率(AOR)?NOB亞硝酸鹽氧化速率(NOR)和曝氣段同步脫氮負(fù)荷(NRRa),用以表征反應(yīng)器的原位活性,并結(jié)合總氮去除負(fù)荷(TNRR) 和總氮去除率(TNRE),以反映反應(yīng)器脫氮性能.其中NRRa還可通過(guò)表征曝氣階段AnAOB的活性進(jìn)而反映生物膜中AnAOB生態(tài)位的穩(wěn)定性.計(jì)算公式分別如下:

式中:△NH4+為曝氣過(guò)程N(yùn)H4+-N去除量總和,mg/L;△NO3-為曝氣過(guò)程N(yùn)O3--N生成量總和,mg/L;△TN為曝氣過(guò)程總氮損失量總和,mg/L; △為一個(gè)運(yùn)行周期內(nèi)曝氣段時(shí)間總和,h; TNinf為進(jìn)水后反應(yīng)初期反應(yīng)器中的總氮濃度; TNeff為出水總氮濃度,mg/L;為一個(gè)周期的時(shí)間,d.AOR、NOR、NRRa單位均為g N/(m3·h), TNRR單位為kg N/(m3·d).

1.3.2 基于16S rDNA的Illumina平臺(tái)高通量測(cè)序 在運(yùn)行第31,220,290,385d分別從反應(yīng)器中取出適量填料,依次標(biāo)記為PE0, PE1, PE2, PE3.PE0代表中溫高基質(zhì)階段啟動(dòng)接種污泥,PE1、PE2、PE3則分別對(duì)應(yīng)中溫高基質(zhì)、常溫高基質(zhì)、常溫低基質(zhì)下穩(wěn)定脫氮的生物膜.參考鄭照明等[31]的方法對(duì)填料進(jìn)行超聲處理.隨后采用漩渦混勻儀(Scilogex MX-F)對(duì)填料進(jìn)行渦旋處理,時(shí)間為5min.收集脫落的生物膜存放于?20℃冰箱保存.待實(shí)驗(yàn)全部完成后將所有污泥樣品送至上海美吉生物科技醫(yī)藥公司進(jìn)行高通量分析測(cè)序.測(cè)序分析后,根據(jù)barcode序列區(qū)分各個(gè)樣本的數(shù)據(jù),進(jìn)行嵌合體過(guò)濾,得到可用于后續(xù)分析的有效數(shù)據(jù),即Clean reads.為了研究樣品的物種組成多樣性,對(duì)所有樣品的Clean reads進(jìn)行聚類(lèi),以97%的一致性(Identity)將序列聚類(lèi)成OTUs (Operational Taxonomic Units),然后對(duì)OTUs的代表序列進(jìn)行物種注釋.

2 結(jié)果與討論

2.1 中溫高基質(zhì)啟動(dòng)及穩(wěn)定運(yùn)行

如圖1階段I所示,反應(yīng)器在接種CANON泥后在中溫高基質(zhì)條件下共運(yùn)行223d,進(jìn)水氨氮控制在(446.5±43.8)mg/L.在經(jīng)歷了前10d較低水平的脫氮[ 全周期總氮去除負(fù)荷TNRR=(0.14±0.08) kg N/ (m3·d)]后,迅速進(jìn)入高效脫氮階段并維持穩(wěn)定,反應(yīng)器總氮去除率TNRE穩(wěn)定在(84.3±4.6)%,總氮去除負(fù)荷TNRR穩(wěn)定在(0.49±0.07) kg N/(m3·d).

圖1 不同溫度和基質(zhì)濃度下反應(yīng)器長(zhǎng)期脫氮效果

以第208d一個(gè)運(yùn)行周期內(nèi)脫氮情況及沿程pH值和DO變化(圖2)為例.計(jì)算得該周期TNRR為0.52kg N/(m3·d),AOR為32.44g N/(m3·h), NRRa為32.21g N/(m3·h),而NOR則繼續(xù)維持在0g N/(m3·h)左右.該周期中曝氣段積累的NO2--N在停曝段被AnAOB完全反應(yīng),限制了下一個(gè)曝氣階段NOB的增殖,使反應(yīng)器能在中溫高基質(zhì)下穩(wěn)定運(yùn)行,同時(shí)也為下一步降溫做好了準(zhǔn)備.

圖2 中溫高基質(zhì)下SBBR第208d一個(gè)運(yùn)行周期NH4+-N、NO2--N、NO3--N、pH值、DO的變化

2.2 常溫高基質(zhì)穩(wěn)定運(yùn)行

反應(yīng)器溫度直接降至20~23℃后共運(yùn)行69d(圖1階段II).在采用合理的曝氣工況調(diào)整策略后,反應(yīng)器也獲得了穩(wěn)定的脫氮效果,出水NO2--N除降溫第1d達(dá)到29.9mg/L,之后基本穩(wěn)定在0mg/L,總氮去除負(fù)荷穩(wěn)定在(0.43±0.04) kg N/(m3·d),總氮去除率為(69.5±5.7)%.

在反應(yīng)器降溫的第1個(gè)運(yùn)行周期,繼續(xù)采用曝氣/停曝時(shí)間=60min/60min的工況進(jìn)行試運(yùn)行,結(jié)果如圖3所示.推測(cè)一方面降溫使生物膜中好氧微生物活性下降, DO在生物膜傳質(zhì)過(guò)程中消耗速率降低,穿透能力上升,生物膜好氧區(qū)擴(kuò)大, 激發(fā)了生物膜內(nèi)層AOB的活性,因而反應(yīng)器曝氣段AOR并未下降,計(jì)算得該周期AOR為36.36g N/(m3·h),略高出階段I.但另一方面,DO穿透能力上升間接導(dǎo)致生物膜中AnAOB生態(tài)位被壓縮,加之降溫的影響, AnAOB活性明顯受到抑制,NRRa僅為20.29g N/(m3·h),低于階段I一個(gè)運(yùn)行周期的32.21g N/(m3·h).這也使得60min曝氣段NO2--N積累速率高達(dá)24.01g N/(m3·h),而60min停曝段的NO2--N去除負(fù)荷只有12.21g N/(m3·h),致使亞硝酸鹽嚴(yán)重積累,NO2--N濃度最高達(dá)60.6mg/L,出水濃度達(dá)29.9mg/L.因此根據(jù)一個(gè)運(yùn)行周期內(nèi)NO2--N的積累速率和去除速率之比(24.01:12.21),調(diào)整反應(yīng)器的曝氣工況為曝氣/停曝時(shí)間=40min/80min.

圖3 常溫高基質(zhì)下SBBR第224d一個(gè)運(yùn)行周期內(nèi)NH4+-N、NO2--N、NO3--N、pH值、DO的變化

圖4 常溫高基質(zhì)下SBBR第276d一個(gè)運(yùn)行周期內(nèi)NH4+-N、NO2--N、NO3--N?pH值?DO的變化

以調(diào)整曝氣工況后第276d一個(gè)運(yùn)行周期內(nèi)脫氮情況及沿程pH值和DO變化(圖4)為例.進(jìn)水后反應(yīng)器初始NH4+-N濃度250.6mg/L,出水NH4+-N為101.5mg/L,保證了FA對(duì)NOB的持續(xù)抑制.與曝氣工況調(diào)整前相比,該周期AnAOB活性已經(jīng)恢復(fù),曝氣段同步脫氮負(fù)荷NRRa回升至30.61g N/(m3·h).同時(shí)AOR升至38.10g N/(m3·h),而NOR則被抑制在0g N/(m3·h)左右.反應(yīng)器TNRR為0.43kg N/(m3·d),未出現(xiàn)NO2--N和NO3--N的積累.由此可見(jiàn),降溫過(guò)程合理縮短曝氣時(shí)間并未對(duì)反應(yīng)器AOR產(chǎn)生不利影響,反而有利于生物膜中AnAOB的活性恢復(fù).曝氣工況的合理調(diào)整有利于生物膜抵御降溫的影響,反應(yīng)器在該溫度條件下維持穩(wěn)定運(yùn)行,為下一步降基質(zhì)做好了準(zhǔn)備.

2.3 常溫低基質(zhì)穩(wěn)定運(yùn)行

如圖1階段III所示,進(jìn)一步降低基質(zhì)后,反應(yīng)器共運(yùn)行了93d.階段III-A中反應(yīng)器經(jīng)歷了第一個(gè)梯度的基質(zhì)降低.進(jìn)水NH4+-N降至(235.2±25.8)mg/L,但反應(yīng)器仍維持在較高脫氮水平.TNRE升至 (82.8±10.7)%,相比階段II有明顯回升,并達(dá)到階段I水平,TNRR則穩(wěn)定在(0.25±0.04) kg N/(m3·d).但同時(shí)AnAOB活性也受到了一定的抑制,逐漸出現(xiàn)了亞硝酸鹽的積累.Gilbert等[32]在利用PE填料啟動(dòng)常溫低基質(zhì)MBBR的時(shí)候遇到了同樣的問(wèn)題.因此在階段III-B保持進(jìn)水基質(zhì)濃度,調(diào)整曝氣工況為曝氣/停曝時(shí)間=30min/90min,通過(guò)延長(zhǎng)單個(gè)曝停周期中停曝時(shí)間以提高反應(yīng)器脫氮能力.反應(yīng)器穩(wěn)定運(yùn)行48d,TNRR為(0.22±0.04)kg N/(m3·d),TNRE為(76.9±2.9)%.在階段III-C進(jìn)行第2梯度的基質(zhì)降低,進(jìn)水NH4+-N降至(105.6±16.1) mg/L.為防止過(guò)度曝氣,重新調(diào)整曝氣工況為曝氣/停曝時(shí)間=8min/ 32min,以維持反應(yīng)器在常溫低基質(zhì)下的穩(wěn)定脫氮.反應(yīng)器在38d穩(wěn)定運(yùn)行過(guò)程中, TNRR為(0.16±0.02) kg N/(m3·d), TNRE穩(wěn)定在 (71.5±7.5)%,未出現(xiàn)過(guò)度曝氣的情況.

圖5(a)中,在III-A運(yùn)行周期內(nèi),進(jìn)水NH4+-N為248.5mg/L,進(jìn)水后反應(yīng)器初始NH4+-N濃度為102.4mg/L,計(jì)算該周期TNRR為0.27kg N/(m3·d), TNRE為88.7%,AOR為24.87g N/(m3·h),NOR約為0,但曝氣段亞硝酸鹽積累速率:停曝段亞硝酸鹽消耗速率=16.34g N/(m3·h):6.11g N/(m3·h) ,這使得反應(yīng)器在40min:80min的曝停工況下無(wú)法將NO2--N反應(yīng)完全,為NOB復(fù)蘇留下隱患.因此延長(zhǎng)單個(gè)曝停周期的停曝時(shí)間,使NOB在每次曝氣開(kāi)始時(shí)都處于低基質(zhì)環(huán)境,如圖5(b)所示.該周期中TNRR為0.25kg N/(m3·d),TNRE為75.3%,AOR為23.78g N/(m3·h), NOB未表現(xiàn)出活性.

反應(yīng)器運(yùn)行至階段III-C,隨著基質(zhì)的進(jìn)一步降低,階段III-B的曝停工況已無(wú)法保證穩(wěn)定脫氮,極易出現(xiàn)過(guò)量曝氣的情況.因此縮短運(yùn)行周期,并根據(jù)曝氣段亞硝酸鹽積累速率:停曝段亞硝酸鹽消耗速率=13.71g N/(m3·h):3.76g N/(m3·h),最終確定反應(yīng)器曝氣工況為曝氣/停曝時(shí)間=8min/32min(圖5(c)),利用頻繁曝停對(duì)NOB進(jìn)行選擇性抑制[16].在該運(yùn)行周期中,TNRR為0.15kg N/(m3·d),TNRE為75.0%,AOR為17.37g N/(m3·h),而NOR為1.91g N/(m3·h),依舊維持在低水平,且未出現(xiàn)NO2--N的積累.反應(yīng)器在常溫低基質(zhì)條件下達(dá)到了較理想的自養(yǎng)脫氮效果并維持穩(wěn)定.

圖5 不同曝氣工況下SBBR一個(gè)運(yùn)行周期NH4+-N、NO2--N、NO3--N、pH值、DO變化

2.4 微生物群落組成分析

從門(mén)、屬兩個(gè)水平分析反應(yīng)器內(nèi)微生物群落組成變化,結(jié)果分別如表2和圖6所示.表2中4個(gè)生物膜樣本中共檢出38個(gè)菌門(mén).其中相對(duì)豐度較高的5個(gè)菌門(mén)為變形菌門(mén)(Proteobacteria)?浮霉菌門(mén)(Planctomycetes)?擬桿菌門(mén)(Bacteroidetes)?綠菌門(mén)(Chlorobi)?綠彎菌門(mén)(Chloroflexi),在各個(gè)樣本中均占據(jù)了80%以上.在這5種主要菌門(mén)中,變形菌門(mén)(Proteobacteria)和浮霉菌門(mén)(Planctomycetes)分別為CANON系統(tǒng)中AOB和AnAOB的所屬菌門(mén),且在每個(gè)生物膜樣品中均占據(jù)了最大的相對(duì)豐度,其中浮霉菌門(mén)最高達(dá)42.61%,與報(bào)道的CANON脫氮系統(tǒng)中該菌門(mén)的相對(duì)豐度相近[33].推測(cè)在中溫高基質(zhì)條件下(PE0→PE1),隨著無(wú)機(jī)環(huán)境的延續(xù)[34]、生物膜掛膜以及反應(yīng)器中絮體逐漸外排[33],變形菌門(mén)相對(duì)豐度下降,而浮霉菌門(mén)則通過(guò)生物膜作用被截流下來(lái).溫度和基質(zhì)的降低對(duì)其他菌門(mén)的脅迫作用逐漸減小[35-36],變形菌門(mén)和浮霉菌門(mén)所占比例隨之減小,但依然占據(jù)著最大的相對(duì)豐度.

表2 各樣本中主要菌門(mén)相對(duì)豐度(%)

圖6a顯示了在屬分類(lèi)水平上微生物群落組成變化.其中與CANON系統(tǒng)脫氮直接相關(guān)的菌屬為Jettenia、Kuenenia、Brocadia以及.Jettenia?Kuenenia?Brocadia為3種AnAOB菌屬[37],其中以Jettenia為主,在4個(gè)生物膜樣品中相對(duì)豐度分別為25.93%, 28.02%,13.74%,12.96%.為AOB的一種菌屬[38-39],其在4個(gè)生物膜樣品中的相對(duì)豐度分別為16.89%、9.98%、2.65%、3.56%.而疑似為NOB的unidentified Nitrospiraceae在整個(gè)反應(yīng)器運(yùn)行過(guò)程中都只占有極小的相對(duì)豐度(￡0.1%),這一結(jié)果從群落組成角度揭示了反應(yīng)器在運(yùn)行過(guò)程中幾乎未出現(xiàn)全程硝化并保持很好的脫氮性能的生物學(xué)原因.

如圖6b所示,將各樣品中主要自養(yǎng)脫氮功能菌Jettenia、Kuenenia、Brocadia以及的相對(duì)豐度與相應(yīng)工況階段下反應(yīng)器脫氮性能相結(jié)合,可以看出,脫氮功能菌相對(duì)豐度降低主要發(fā)生在降溫階段(PE1→PE2),與此同時(shí)TNRR也略有降低.而在降基質(zhì)階段(PE2→PE3) TNRR出現(xiàn)了顯著降低,但該階段除Kuenenia相對(duì)豐度顯著增加外,其余功能菌相對(duì)豐度均未發(fā)生明顯變化.Kuenenia被認(rèn)為因具有更強(qiáng)的基質(zhì)親和力而在低基質(zhì)環(huán)境中更具競(jìng)爭(zhēng)優(yōu)勢(shì)[40-41].由此可見(jiàn),降溫對(duì)功能微生物相對(duì)豐度影響更大,但曝氣工況的合理調(diào)整能很好地維持反應(yīng)器自養(yǎng)脫氮性能的穩(wěn)定,避免NO2--N的積累和NOB的復(fù)蘇.而降基質(zhì)階段由于進(jìn)水負(fù)荷的限制,致使AOR和TNRR顯著下降,但除對(duì)基質(zhì)親和力更強(qiáng)的Kuenenia相對(duì)豐度有所增加外,其余功能菌相對(duì)豐度變化不大.反應(yīng)器TNRE維持在70%左右,自養(yǎng)脫氮性能依舊保持穩(wěn)定,未出現(xiàn)向全程硝化轉(zhuǎn)變的趨勢(shì).

3 結(jié)論

3.1 SBBR反應(yīng)器在中溫(35℃)高基質(zhì)[(446.5± 43.8) mg NH4+-N/L]曝氣/停曝=60min/60min條件下穩(wěn)定運(yùn)行223d,總氮去除負(fù)荷(TNRR) 和總氮去除率(TNRE)分別為(0.49±0.07) kg N/(m3·d)和(84.3± 4.6)%.

3.2 溫度降至20~23℃,根據(jù)一個(gè)運(yùn)行周期內(nèi)NO2--N積累速率和去除速率之比調(diào)整曝氣工況為曝氣/停曝=40min/80min, 避免了NO2--N的積累.反應(yīng)器運(yùn)行69d后TNRR和TNRE分別降至(0.43±0.04) kg N/(m3·d)和(69.5±5.7)%.

3.3 分3個(gè)階段逐步降低基質(zhì)至(105.6±16.1) mg NH4+-N/L,采用相同策略分別調(diào)整曝氣/停曝時(shí)間為40min/80min?30min/90min和8min/32min,反應(yīng)器運(yùn)行93d后TNRR降至(0.16±0.02) kg N/(m3·d),TNRE升至(71.5±7.5)%.

3.4 16S rDNA高通量測(cè)序結(jié)果表明,樣品中自養(yǎng)脫氮功能微生物始終占據(jù)主導(dǎo)地位.AnAOB主要有Jettenia?Kuenenia?Brocadia 3個(gè)屬,AOB主要為.脫氮功能菌相對(duì)豐度降低主要發(fā)生在降溫階段,但依舊占據(jù)主導(dǎo)地位,反應(yīng)器TNRR僅略有下降.降基質(zhì)階段由于進(jìn)水負(fù)荷的限制影響了反應(yīng)器總氮去除負(fù)荷,但未威脅AOB和AnAOB的優(yōu)勢(shì)地位,對(duì)基質(zhì)親和力更強(qiáng)的Kuenenia相對(duì)豐度甚至有所增加.生物膜中NOB相對(duì)豐度則一直被抑制在0.1%以下.

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Stable operation of CANON system during temperature and substrate decreasing process via aerobic regime adjustment.

XIE Hong-chao, WANG Xiao-dong, WANG Wei-gang, ZHANG Yao, SHI Qin, WANG Ya-yi*

(State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China)., 2019,39(7)：2781~2788

The feasibility of the stable operation of a sequencing biofilm batch reactor (SBBR) for completely autotrophic nitrogen removal over nitrite (CANON) was investigated using aeration condition adjusting strategy, along with decreasing temperature and influent substrate (anammonia). The SBBR operated steadily for 223 days at 35°C and high substrate [(446.47±43.77) mg NH4+-N/L] with the aeration regime of aeration/non-aeration=60min/60min; the total nitrogen removal rate (TNRR) and total nitrogen removal efficiency (TNRE) reached (0.49±0.07) kg N/(m3·d) and (84.3±4.6)%, respectively. After temperaute decreasd to 20~23°C, the intermittent aerobic condition was changed to aeration/non-aeration=40min/80min based on the ratio of NO2--N accumulation rate to NO2--N removal rate in the single-cycles. The TNRR and TNRE decreased to (0.43±0.04) kg N/(m3·d) and (69.5±5.7)% for 67days of operation, respectively. With gradual decreasing ammonia to (105.6±16.1) mg NH4+-N/L, the aeration/non-aeration time was regulated to 40min/80min, 30min/90min and 8min/32min in sequence. For 67days operation, the TNRR decreased to (0.16±0.02) kg N/(m3·d); nevertheless, the TNRE increased to (71.5±7.5)%. High-throughput sequencing results confirmed that the regulation strategy applied herein ensured the dominance of nitrogen removal functional bacterias in CANON system during decreasing temperature and substrate while the relative abundance of nitrite oxidizing bacteira was always below 0.1%.

CANON；biofilm reactor；intermittent aerobic conditions；temperature；ammonium concentration；high-throughput sequencing

X703.5

A

1000-6923(2019)07-2781-08

謝弘超(1995–),男,江西吉安人,同濟(jì)大學(xué)碩士研究生,主要從事污水生物處理理論與應(yīng)用研究.

2018-12-04

國(guó)家自然科學(xué)基金資助項(xiàng)目(51522809)

* 責(zé)任作者, 教授, yayi.wang@#edu.cn