溶解氧對(duì)HLB-MR反應(yīng)器內(nèi)有機(jī)物的生物絮凝影響

萬(wàn)立國(guó),林 巧,張麗君,張文華*,劉紅波,龍北生,熊 玲

溶解氧對(duì)HLB-MR反應(yīng)器內(nèi)有機(jī)物的生物絮凝影響

萬(wàn)立國(guó)1,2,林 巧1,張麗君1,張文華1,2*,劉紅波1,2,龍北生1,2,熊 玲1

(1.長(zhǎng)春工程學(xué)院水利與環(huán)境工程學(xué)院,吉林 長(zhǎng)春 130012；2.長(zhǎng)春工程學(xué)院,吉林省城市污水處理重點(diǎn)實(shí)驗(yàn)室,吉林 長(zhǎng)春 130012)

為了研究溶解氧(DO)對(duì)高負(fù)荷生物絮凝-膜反應(yīng)器(HLB-MR)內(nèi)有機(jī)物生物絮凝規(guī)律的影響,采用平行對(duì)比實(shí)驗(yàn),考察了不同DO條件下反應(yīng)器內(nèi)有機(jī)物的生物絮凝效果、胞外聚合物(EPS)含量、金屬陽(yáng)離子濃度和微生物群落結(jié)構(gòu).結(jié)果表明:DO濃度分別為1~2mg/L和6~8mg/L時(shí), HLB-MR反應(yīng)器的絮凝效率分別為83%和89%,兩反應(yīng)器內(nèi)上清液的濁度差別也進(jìn)一步證實(shí),較高的DO濃度下,反應(yīng)器的生物絮凝效果更好.DO濃度在6~8mg/L時(shí),HLB-MR反應(yīng)器內(nèi)結(jié)合態(tài)EPS和自由態(tài)EPS的含量分別為15.64mg /(g?VSS)和8.71mg/L,兩者均顯著高于DO為1~2mg/L時(shí)的11.83mg /(g?VSS)和6.56mg/L,反應(yīng)器濃縮液中鎂和鋁的濃度也均明顯高于低DO濃度時(shí)所對(duì)應(yīng)的值,這說(shuō)明在高DO條件下,有更多的EPS與金屬陽(yáng)離子結(jié)合而固定在污泥基質(zhì)中,促進(jìn)了生物絮凝.高通量測(cè)序表明,DO濃度分別為1~2mg/L和6~8mg/L時(shí),HLB-MR反應(yīng)器內(nèi)細(xì)菌的群落結(jié)構(gòu)差異明顯,高DO濃度反應(yīng)器底泥中Actinobacteria和Saccharibacteria的相對(duì)豐度較高,可能對(duì)生物絮凝有促進(jìn)作用.

膜反應(yīng)器；生物絮凝；溶解氧；胞外聚合物；金屬陽(yáng)離子；微生物群落

隨著人口的快速增長(zhǎng)和城鎮(zhèn)化水平的不斷提高,城市污水的產(chǎn)生量急劇增加.城市污水中蘊(yùn)含大量的能源,據(jù)報(bào)道每m3城市污水中通常含有1.9kWh的有機(jī)化學(xué)能[1],然而城市污水中有機(jī)物的濃度較低,難以直接實(shí)現(xiàn)其經(jīng)濟(jì)高效能源化,城市污水中有機(jī)物的高效濃縮富集技術(shù)成為了保障污水有機(jī)能源經(jīng)濟(jì)回收的關(guān)鍵[2-3].一般城市污水中約70%的有機(jī)物以懸浮或膠體形態(tài)存在,因而膜分離濃縮污水中有機(jī)物的方法受到很多研究者的青睞,但直接膜過(guò)濾城市污水存在膜污染嚴(yán)重和膜通量急劇下降的問(wèn)題[4-5],本研究構(gòu)建了高負(fù)荷生物絮凝-膜反應(yīng)器(HLB-MR),其理念為在膜分離濃縮污水中的有機(jī)物時(shí),利用微生物產(chǎn)生的胞外聚合物生物絮凝污水中的懸浮和膠體物質(zhì),降低膜污染,保證工藝的穩(wěn)定性.生物絮凝對(duì)HLB-MR反應(yīng)器回收污水中有機(jī)物、緩解膜污染和降低整個(gè)系統(tǒng)的運(yùn)行能耗均有重要影響.溶解氧(DO)是微生物與底物反應(yīng)的重要生化參數(shù),對(duì)微生物的活性、菌膠團(tuán)的形成以及污泥絮體特性都有重要的影響,是反應(yīng)器內(nèi)有機(jī)物生物絮凝過(guò)程的重要控制參數(shù),但關(guān)于DO對(duì)高負(fù)荷膜反應(yīng)器內(nèi)生物絮凝影響的研究報(bào)道較少,本研究采用中空纖維超濾膜反應(yīng)器,以中國(guó)北方實(shí)際的城市污水為處理對(duì)象,對(duì)比分析了HLB-MR反應(yīng)器在1~2mg/L和6~8mg/L 2個(gè)DO濃度條件下的生物絮凝效果,并對(duì)2反應(yīng)器內(nèi)濃縮液的胞外聚合物(EPS)濃度、絮體粒徑分布、有關(guān)金屬陽(yáng)離子濃度和微生物種群結(jié)構(gòu)進(jìn)行了檢測(cè)和對(duì)比分析,以期闡明DO對(duì)這種新型結(jié)構(gòu)的HLB-MR反應(yīng)器生物絮凝的影響及機(jī)制,為將來(lái)該技術(shù)的實(shí)際應(yīng)用提供理論支撐.

1 材料與方法

1.1 實(shí)驗(yàn)裝置與運(yùn)行

實(shí)驗(yàn)裝置如圖1所示,實(shí)驗(yàn)過(guò)程中控制2組相同HLB-MR反應(yīng)器的DO濃度分別為1~2mg/L和6~8mg/L,分別記為L(zhǎng)DO反應(yīng)器和HDO反應(yīng)器,并保持2個(gè)反應(yīng)器在20℃平行運(yùn)行.實(shí)驗(yàn)中選擇1~ 2mg/L的DO濃度是認(rèn)為該濃度對(duì)微生物的有氧生長(zhǎng)還沒(méi)有限制,考察是否存在降低HLB-MR反應(yīng)器運(yùn)行能耗的可能性;選擇6~8mg/L相對(duì)高的DO濃度是避免在污泥絮體中產(chǎn)生厭氧區(qū)域,排除厭氧對(duì)生物絮凝的抑制作用.每組HLB-MR反應(yīng)器的容積為1.87L,內(nèi)配備1束中空纖維膜組件(天津膜天膜科技股份有限公司,聚偏氟乙烯(PVDF)),膜面積為0.28m2,膜孔徑為0.03μm,扣除膜組件所占的體積后反應(yīng)器的有效容積為1.70L.HDO反應(yīng)器完全采用空氣曝氣,用氣體流量計(jì)調(diào)節(jié)曝氣流量DO濃度為6~8mg/L.LDO反應(yīng)器采用氮?dú)夂涂諝饣旌蠚怏w曝氣,通過(guò)調(diào)整混合比例使反應(yīng)器內(nèi)的溶解氧濃度為1~2mg/L,為了保證2個(gè)反應(yīng)器的氣體剪切力相同, LDO反應(yīng)器混合氣體流量與HDO反應(yīng)器的空氣流量相同. 2個(gè)反應(yīng)器均采用蠕動(dòng)泵抽吸的方式出水,時(shí)間繼電器控制蠕動(dòng)泵每抽吸8min,停止2min,蠕動(dòng)泵采用恒通量模式運(yùn)行,通過(guò)控制出水通量保證2個(gè)反應(yīng)器的水力停留時(shí)間(HRT)為1h,通過(guò)蠕動(dòng)泵控制濃縮液排出量保證2個(gè)反應(yīng)器的污泥停留時(shí)間(SRT)為0.6d.

實(shí)驗(yàn)原水取自吉林省長(zhǎng)春市某城市污水處理廠的沉砂池出水,每次取來(lái)的污水在4℃下儲(chǔ)存且最多不超過(guò)3d,在進(jìn)原水箱之前將污水通過(guò)3mm孔徑的篩網(wǎng)過(guò)濾并將其溫度調(diào)至室溫(20℃左右).

1.2 樣品與分析

反應(yīng)器通常在運(yùn)行3倍的SRT時(shí)長(zhǎng)后才會(huì)趨于穩(wěn)定,本研究中2個(gè)反應(yīng)器平行運(yùn)行了15d,分別在第13、14、15d對(duì)反應(yīng)器進(jìn)水、濃縮液和出水進(jìn)行取樣分析, 每個(gè)樣品取3個(gè)平行.

在對(duì)樣品COD進(jìn)行檢測(cè)時(shí),將其分級(jí)為4類(lèi),即總COD(CODTO)、懸浮COD(CODSS)、膠體COD(CODCO)、溶解COD(CODSO).CODTO為樣品直接測(cè)定的COD,CODSS為CODTO與樣品經(jīng)過(guò)濾紙(12~25μm)過(guò)濾后濾液的COD之差,CODCO為濾紙過(guò)濾后濾液的COD與濾液經(jīng)濾膜(0.45μm)過(guò)濾后的COD之差,CODSO為濾膜(0.45μm)過(guò)濾后所得濾液的COD.COD參照標(biāo)準(zhǔn)方法[6]測(cè)定.

EPS測(cè)定:取30mL的反應(yīng)器濃縮液置于離心管中,在離心力12000×g下離心5min,然后將上清液通過(guò)0.45μm濾膜過(guò)濾,所得濾液測(cè)定的EPS即為自由態(tài)EPS.用純水將離心管中剩余污泥重新定容至原體積,混勻后置于80℃水浴30min,待離心管冷卻后再次于離心力12000×g下離心5min,將上清液通過(guò)0.45μm的濾膜,所得濾液測(cè)得的EPS即為結(jié)合態(tài)EPS.對(duì)自由態(tài)EPS和結(jié)合態(tài)EPS中的蛋白質(zhì)和多糖進(jìn)行測(cè)定,EPS-蛋白質(zhì)采用改進(jìn)的Lowry法測(cè)定[7],EPS多糖采用蒽酮比色法測(cè)定[8].

金屬離子測(cè)定:濃縮液樣品經(jīng)30min沉淀后取其上清液,上清液經(jīng)過(guò)0.45μm濾膜過(guò)濾后,利用ICP-OES(Perkin Elmer,Optima 5300DV)測(cè)量金屬離子(鎂、鈣、鋁).一定量的濃縮液沉淀物經(jīng)冷凍干燥后,取已知重量的凍干固體至聚四氟乙烯管中,加入10mL 65% HNO3并置于石墨消解儀(SCP,DigiPREP MS)上在180℃條件下消解45min,去酸,使剩余液體積約1mL,冷卻至室溫后用2% HNO3淋洗,過(guò)濾后定容至50mL,并利用ICP-OES(Perkin Elmer,Optima 5300DV)測(cè)量金屬離子(鎂、鈣、鋁).

濃縮液沉淀30min后收集上清液,采用濁度儀(HACH,2100Q)測(cè)定其濁度.采用溶解氧儀(WTW, OXI 3310-SET1)測(cè)定兩反應(yīng)器內(nèi)的DO濃度.采用激光粒度粒形分析儀(EyeTech)測(cè)量濃縮液樣品的絮體粒徑,其測(cè)量結(jié)果以個(gè)數(shù)粒度分布的數(shù)據(jù)形式記錄.

在反應(yīng)器運(yùn)行第15d時(shí),對(duì)2個(gè)反應(yīng)器內(nèi)的濃縮液和進(jìn)水進(jìn)行取樣,為了保證反應(yīng)器內(nèi)濃縮液取樣的代表性,取樣時(shí)將膜組件拿出反應(yīng)器,將反應(yīng)器內(nèi)的濃縮液充分混勻后取出濃縮液,對(duì)濃縮液進(jìn)行30min的沉淀分離,分別取上清液和底泥與進(jìn)水一起進(jìn)行DNA提取及高通量測(cè)序.利用 DNA 提取試劑盒 Fast DNA Spin Kit for Soil(QBIOgen Inc.,Carlsba, CA,美國(guó))提取樣品的總DNA.采用338F(ACTC CTAC GGGA GGCA GCAG)和806R (5'-GGAC TACH VGGG TWTC TAAT-3')引物對(duì)樣品進(jìn)行V3和V4區(qū)16S rRNA基因擴(kuò)增[9],采用20 μL的PCR擴(kuò)增體系,配置如下:5×FastPfu Buffer,4μL、2.5mM dNTPs,2μL、Forward Primer(5μM),0.8μL、Reverse Primer (5μM),0.8μL、FastPfu Polymerase,0.4μL、BSA,0.2μL、樣品DNA,10ng并用ddH2O補(bǔ)齊至20μL.在PCR儀(ABI GeneAmp? 9700型)中的反應(yīng)條件為:95℃預(yù)加熱3min,隨后進(jìn)行30周期擴(kuò)增反應(yīng)(95℃變性30s,55℃退火30s,72℃延伸45s,72℃延伸10min,72℃直至終止).DNA 擴(kuò)增樣品送上海某生物技術(shù)公司采用 Illumina MiSeq 測(cè)序儀測(cè)序,通過(guò)序列比對(duì)和數(shù)據(jù)統(tǒng)計(jì),分析細(xì)菌在門(mén)水平上的相對(duì)豐度.

2 結(jié)果與討論

2.1 生物絮凝效果

如表1和圖2所示.進(jìn)水中CODSS和CODCO百分比分別為73.5%和13.7%,LDO和HDO反應(yīng)器濃縮液中它們的比例分別為94.9%和3.2%,96.7%和1.8%.而對(duì)CODSO而言,它在進(jìn)水、LDO和HDO反應(yīng)器濃縮液中比例分別為12.8%、1.9%和1.5%.基于CODCO在進(jìn)水中和濃縮液中的質(zhì)量負(fù)荷所計(jì)算出的LDO和HDO反應(yīng)器的絮凝效率分別為83%和89%.由此可見(jiàn),在2個(gè)反應(yīng)器中,有大量的CODCO轉(zhuǎn)化為CODSS.相比LDO反應(yīng)器,HDO反應(yīng)器內(nèi)這種生物絮凝程度較高、絮凝效果較好.LDO和HDO兩反應(yīng)器內(nèi)濃縮液沉淀的上清液的濁度分別為32NTU和27NTU,HDO反應(yīng)器上清液中較低的濁度值也證實(shí)了在該反應(yīng)器中生物絮凝效果較好.

表1 進(jìn)水、濃縮液和出水中各分類(lèi)COD濃度

LDO和HDO 2個(gè)反應(yīng)器內(nèi)濃縮液中顆粒的個(gè)數(shù)濃度均為2.2×105/mL,兩反應(yīng)器內(nèi)濃縮液中不同粒徑范圍的顆粒所占百分比如圖3所示.HDO反應(yīng)器中濃縮液所含的0~1μm區(qū)間段的顆粒百分比為26.2%,明顯高于LDO反應(yīng)器中所對(duì)應(yīng)區(qū)間段的值(19.0%),但在1~10μm和10~30μm 2個(gè)區(qū)間段, HDO反應(yīng)器中濃縮液所含的顆粒百分比分別為58.4%和14.3%,均低于LDO反應(yīng)器中所對(duì)應(yīng)區(qū)間段的值(64.4%和15.6%).兩反應(yīng)器內(nèi)濃縮液中30~100μm區(qū)間段的粒徑數(shù)量均較少,而且它們所占百分比在兩反應(yīng)器中差別不大.相對(duì)LDO反應(yīng)器而言,HDO反應(yīng)器內(nèi)濃縮液中0~1μm區(qū)間段的顆粒比例較高,而10~30μm區(qū)間段的顆粒比例較低.這可能因?yàn)檫^(guò)高的DO濃度條件下HLB-MR產(chǎn)生了解絮凝效應(yīng),導(dǎo)致反應(yīng)器內(nèi)濃縮液中較大顆粒解體為更加細(xì)小的顆粒,從而出現(xiàn)細(xì)小顆粒的比例增大的現(xiàn)象.DO是影響污泥絮體性質(zhì)的重要參數(shù),已有相關(guān)學(xué)者進(jìn)行了大量研究[10-12],但關(guān)于5mg/L以上的DO濃度對(duì)污泥絮體大小的影響機(jī)制尚不十分清楚,需要進(jìn)一步研究.

圖2 不同DO下反應(yīng)器內(nèi)各類(lèi)COD比例及絮凝效率

圖3 2反應(yīng)器濃縮液濃中不同粒徑范圍的顆粒占比

關(guān)于DO對(duì)絮凝效率的影響,Faust等[13]報(bào)道了類(lèi)似的結(jié)果,高負(fù)荷膜生物反應(yīng)器在DO濃度為4mg /L時(shí)的絮凝效率為92%,明顯高于DO濃度為1mg/ L時(shí)的69%.與本研究不同的是,DO濃度為6~8mg/L和1~2mg/L條件時(shí),HLB-MR反應(yīng)器的絮凝效率差別不明顯,且均在80%以上.但其所報(bào)道的DO對(duì)反應(yīng)器內(nèi)濃縮液顆粒尺寸大小分布的影響與本研究呈相反的規(guī)律,這可能由于進(jìn)水水質(zhì)和反應(yīng)器結(jié)構(gòu)形式不同所致.低DO濃度下活性污泥系統(tǒng)有機(jī)物絮凝效果較差的原因文獻(xiàn)提供了以下幾種解釋:1)在低DO濃度下有氧活性的降低可能導(dǎo)致了作用于生物絮凝的EPS的產(chǎn)生速率降低或者在厭氧條件下降解的速率加快[14-16],2)低DO濃度水平下微生物能將Fe3+還原成Fe2+而出現(xiàn)反絮凝現(xiàn)象,因?yàn)镕e3+與微生物胞外聚合物之間能產(chǎn)生比Fe2+更強(qiáng)的陽(yáng)離子架橋作用[17-18],3)低DO濃度條件下開(kāi)始過(guò)度生長(zhǎng)的絲狀細(xì)菌對(duì)絮凝產(chǎn)生了的負(fù)面作用[19].鑒于上述報(bào)道中所控制的DO濃度水平不盡相同而且相關(guān)的環(huán)境因子(例如污泥濃度、溫度、pH值和底物成分)不同,導(dǎo)致最佳的DO濃度控制范圍也僅能只做參考,而在未經(jīng)刻意污泥接種的HLB-MR反應(yīng)器內(nèi),在極短的SRT和HRT條件下,DO濃度對(duì)生物絮凝過(guò)程的影響機(jī)制是否與上述相同尚需進(jìn)一步研究.

2.2 EPS與金屬陽(yáng)離子濃度

濃縮液沉淀部分和上清部分的EPS分別被稱(chēng)為結(jié)合態(tài)EPS和自由態(tài)EPS,總EPS由EPS-蛋白質(zhì)和EPS-多糖兩部分組成.如圖4所示, LDO反應(yīng)器內(nèi)的總EPS有77.0%以結(jié)合態(tài)形式存在,23.0% 以自由態(tài)形式存在;而HDO反應(yīng)器內(nèi)的總EPS有79.9%以結(jié)合態(tài)形式存在,20.1% 以自由態(tài)形式存在.可見(jiàn)2個(gè)反應(yīng)器中,結(jié)合態(tài)EPS的含量比自由態(tài)EPS含量高3倍以上,為總EPS的主要存在形態(tài).文獻(xiàn)報(bào)道污水中顆粒的生物絮凝主要緣于微生物分泌出的EPS[20],由于EPS的粘性作用,它可以在顆粒間形成互連的基質(zhì)[21].沉淀中結(jié)合態(tài)EPS含量較高,這正好能解釋LDO和HDO反應(yīng)器均發(fā)生了較廣泛的生物絮凝.HDO反應(yīng)器結(jié)合態(tài)EPS和自由態(tài)EPS的含量分別為15.64mg/(g·VSS)和8.71mg/L,兩者均顯著高于LDO反應(yīng)器內(nèi)所對(duì)應(yīng)含量(11.83mg /(g·VSS)和6.56mg/L),這表明較高DO濃度下,HLB-MR內(nèi)產(chǎn)生了更多的EPS.有研究報(bào)道EPS的功能基團(tuán),如氨基,羧基和磷酸基團(tuán),有助于絮凝污水顆粒和保持絮凝體的穩(wěn)定性[22-23].LDO和HDO兩反應(yīng)器內(nèi)自由態(tài)EPS中只存在EPS-多糖,沒(méi)有EPS-蛋白質(zhì),而兩反應(yīng)器在結(jié)合態(tài)EPS中EPS-蛋白質(zhì)的含量分別為12.3%和19.0%,均遠(yuǎn)小于50%,這表明EPS-蛋白質(zhì)含量低于EPS-多糖的含量,而且主要存在污泥基質(zhì)中.然而,一些研究文獻(xiàn)卻報(bào)道EPS-蛋白質(zhì)是污泥和生物膜中總EPS的主要成分[24-25],這可能是由于實(shí)驗(yàn)水質(zhì)和EPS提取方法的不同導(dǎo)致了不同的結(jié)論.

圖4 2個(gè)反應(yīng)器濃縮液結(jié)合態(tài)和自由態(tài)EPS含量及所含多糖和蛋白濃度

表2給出了多價(jià)金屬陽(yáng)離子Ca2+, Mg2+和Al3+在濃縮液沉淀物和上清液中的濃度.在濃縮液沉淀物中,鈣的濃度最高,其次是鋁和鎂,鈣和鋁的濃度超過(guò)鎂濃度的2倍.這3種陽(yáng)離子,在濃縮液沉淀物中,HDO反應(yīng)器中的鎂和鋁的濃度均明顯高于LDO反應(yīng)器中的濃度,鈣的濃度兩者相差不大;而在上清液中,鎂的含量極低而且兩反應(yīng)器中濃度差別極小,而鈣和鋁在HDO反應(yīng)器中的濃度均明顯低于LDO反應(yīng)器中的濃度.這些數(shù)據(jù)表明,與LDO反應(yīng)器相比,HDO反應(yīng)器中有更多的陽(yáng)離子分配到濃縮液的固體中,這與HDO反應(yīng)器有更高的結(jié)合態(tài)EPS濃度的結(jié)果相一致,這可能因?yàn)槎鄡r(jià)金屬陽(yáng)離子與EPS之間形成了橋連作用并嵌入到了濃縮液的污泥基質(zhì)中,常用雙電層相互作用理論、離子架橋理論和藻朊酸鹽理論來(lái)解釋其促進(jìn)生物絮凝的機(jī)理[26-27].多價(jià)金屬離子對(duì)生物絮凝的促進(jìn)作用已被研究者廣泛證明, jin等[28]通過(guò)對(duì)7個(gè)污水處理廠進(jìn)行研究,發(fā)現(xiàn)金屬陽(yáng)離子濃度的提高能改善污泥的沉降性和可壓縮性,Wen 等[29]報(bào)道Al3+濃度的增加能提高活性污泥的絮凝效果,Bruus等[30]發(fā)現(xiàn)Ca2+的排出導(dǎo)致了活性污泥絮凝體的分散.本研究上清液中鈣、鎂和鋁的濃度數(shù)據(jù)還說(shuō)明:鎂和鈣離子與固相污泥基質(zhì)結(jié)合較緊密,不易從沉淀中分離進(jìn)入上清液,而鋁離子則較易分配至上清液中,這可能與鋁離子絮凝形成的沉淀物容易受環(huán)境因素比如pH值、剪切力等的影響有關(guān).

表2 HLB-MRs內(nèi)濃縮液沉淀物和上清液中Ca2+、Mg2+和 Al3+的濃度

2.3 微生物群落結(jié)構(gòu)特性

對(duì)進(jìn)水(Wastewater)、LDO反應(yīng)器上清液(LDO- S)、HDO反應(yīng)器上清液(HDO-S)、LDO反應(yīng)器底泥(LDO-R)、HDO反應(yīng)器底泥(HDO-R)共5個(gè)樣品進(jìn)行了高通量測(cè)序分析.5個(gè)樣品中不同門(mén)水平細(xì)菌的相對(duì)豐度如圖5所示,圖中相對(duì)豐度低于1%的菌群合并為others.由圖5可知,DO濃度的不同導(dǎo)致了2個(gè)HLB-MR反應(yīng)器內(nèi)上清液和底泥中細(xì)菌的群落結(jié)構(gòu)出現(xiàn)了差異.Proteobacteria在所有樣品(進(jìn)水、底泥和上清液)中均為優(yōu)勢(shì)菌群,該現(xiàn)象與之前一些文獻(xiàn)報(bào)道一致[31-32].Proteobacteria在LDO-S和HDO-S樣品中相對(duì)豐度分別為49.6%和49.1%,在LDO-R和HDO-R樣品中的相對(duì)豐度分別為38.9%和32.8%.當(dāng)DO濃度升高時(shí),上清液中Proteobacteria的相對(duì)豐度幾乎無(wú)變化,僅降低了0.5%,而底泥中Proteobacteria的相對(duì)豐度則變化顯著,降低了6.1%,說(shuō)明隨著DO濃度的升高,污泥相中的其他種類(lèi)微生物開(kāi)始競(jìng)爭(zhēng)生長(zhǎng),Proteobacteria的相對(duì)豐度有所降低,而其在上清液中維持較高的相對(duì)豐度,說(shuō)明Proteobacteria容易呈現(xiàn)為游離狀態(tài)或者較易從污泥絮體或聚集體中脫離.

在上清液樣品LDO-S和HDO-S中, Actinobacteria的相對(duì)豐度分別為6.14%和4.84%,而在底泥樣品LDO-R和HDO-R中,其相對(duì)豐度分別為14.47%和21.08%.在上清液中相對(duì)豐度明顯小于其在底泥中的相對(duì)豐度,這說(shuō)明Actinobacteria更有可能形成污泥絮體或粘附在已經(jīng)形成的絮體上.隨著DO濃度的升高,Actinobacteria在反應(yīng)器底泥中的相對(duì)豐度增加,可能對(duì)有機(jī)物的生物絮凝有促進(jìn)作用.這與Agunbiade等[33]的研究相吻合,他們指出Actinobacteria能促進(jìn)生物絮凝,可以用其制備經(jīng)濟(jì)廉價(jià)的生物絮凝劑.Saccharibacteria在上清液和底泥樣品中的相對(duì)豐度則呈現(xiàn)出與Actinobacteria相反的現(xiàn)象,在上清液樣品LDO-S和HDO-S中, Saccharibacteria的相對(duì)豐度分別為14.49%和17.87%,而在底泥樣品LDO-R和HDO-R中其相對(duì)豐度分別為3.99%和4.77%,這說(shuō)明Saccharibacteria大部分呈現(xiàn)游離狀態(tài)或者較易從污泥絮體脫離.但隨著DO濃度的升高,HLB-MR反應(yīng)器內(nèi)Saccharibacteria相對(duì)豐度明顯增大,這可能也對(duì)有機(jī)物的生物絮凝有積極作用,其相關(guān)機(jī)制需進(jìn)一步研究.

圖5 5個(gè)樣品中細(xì)菌在門(mén)水平的相對(duì)豐度分布

3 結(jié)論

3.1 DO濃度在1~2mg/L和6~8mg/L時(shí), HLB-MR反應(yīng)器的絮凝效率分別為83%和89%, DO濃度越高,生物絮凝效果越顯著.

3.2 DO濃度在6~8mg/L時(shí),HLB-MR反應(yīng)器中結(jié)合態(tài)和自由態(tài)EPS的含量、濃縮液中的鎂和鋁的濃度均顯著高于低DO濃度所對(duì)應(yīng)的值,高DO條件下,有更多的金屬陽(yáng)離子與EPS結(jié)合固定在污泥基質(zhì)中,促進(jìn)了生物絮凝過(guò)程.

3.3 DO濃度的不同導(dǎo)致HLB-MR反應(yīng)器內(nèi)細(xì)菌的群落結(jié)構(gòu)出現(xiàn)了差異,隨著DO的提高, Actinobacteria和Saccharibacteria在反應(yīng)器底泥中的相對(duì)豐度增加,可能對(duì)生物絮凝有促進(jìn)作用.

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Effect of dissolved oxygen on bioflocculation of organic matter in high loaded bioflocculation membrane reactor.

WAN Li-guo1,2, LIN Qiao1, ZHANG Li-jun1, ZHANG Wen-hua1,2*, LIU Hong-bo1,2, LONG Bei-sheng1,2, XIONG Ling1

(1.School of Water Conservancy & Environment Engineering, Changchun Institute of Technology, Changchun 130012, China；2.Jilin Provincial Key Laboratory of Municipal Wastewater Treatment, Changchun Institute of Technology, Changchun 130012, China)., 2019,39(8)：3340~3346

In order to study the effect of dissolved oxygen (DO) on bioflocculation law of organic matter in high loaded bioflocculation membrane reactor (HLB-MR), parallel contrast experiments were conducted to investigate the bioflocculation effect of organic matter, the content of extracellular polymeric substance (EPS), the concentration of metal cations and the microbial community structure under different DO conditions. When the DO concentrations were at 1~2mg/L and 6~8mg/L, the flocculation efficiencies of HLB-MRs were 83% and 89%, respectively. The difference in turbidity of the supernatant in the HLB-MRs further confirmed that the higher DO concentration had induced a better bioflocculation effect. When the DO concentration was at 6~8mg/L, the content of bound EPS and supernatant EPS in the HLB-MR were 15.64mg/(g×VSS) and 8.71mg/L, respectively, both of which were significantly higher than 11.83mg/(g×VSS) and 6.56mg/L at 1~2mg/L of DO concentration, and the concentrations of magnesium and aluminum in the concentrate in the HLB-MR were also significantly higher than those at 1~2mg/L of DO concentration. Under high DO concentration conditions, more EPS are combined with metal cations to be immobilized in the sludge matrix, which promotes bioflocculation.High-throughput sequencing showed that when the DO concentrations were at 1~2mg/L and 6~8mg/L, the community structure of bacteria in the HLB-MRs were significantly different. The relative abundance of Actinobacteria and Saccharibacteria in the sediment of HLB-MR at higher DO concentration were higher, which might promote bioflocculation.

membrane reactor；bioflocculation；dissolved oxygen；extracellular polymeric substance；metal cation；microbial community

X703.1

A

1000-6923(2019)08-3340-07

萬(wàn)立國(guó)(1982-),男,湖北天門(mén)人,副教授,碩士,主要從事污水處理及其資源化研究.發(fā)表論文25篇.

2019-01-19

吉林省自然科學(xué)基金資助項(xiàng)目(20180101317JC);吉林省省級(jí)產(chǎn)業(yè)創(chuàng)新專(zhuān)項(xiàng)資金資助項(xiàng)目(2019C055);國(guó)家科技重大專(zhuān)項(xiàng)(2012ZX07202-009-01);吉林省重點(diǎn)科技攻關(guān)項(xiàng)目(20160204006SF);長(zhǎng)春工程學(xué)院種子基金資助項(xiàng)目(320180027)

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