菌-藻共生好氧顆粒污泥的穩(wěn)定性機(jī)理

劉 怡,張 冰,時(shí)文歆*,朱易春,劉祖文

菌-藻共生好氧顆粒污泥的穩(wěn)定性機(jī)理

劉 怡1,張 冰1,時(shí)文歆1*,朱易春2,劉祖文2

(1.重慶大學(xué)環(huán)境與生態(tài)學(xué)院,三峽庫區(qū)生態(tài)環(huán)境教育部重點(diǎn)實(shí)驗(yàn)室,重慶 400045；2.江西理工大學(xué)土木與測繪工程學(xué)院,江西 贛州 341000)

在非曝氣條件下接種好氧顆粒污泥(AGS)和綠藻藻種,經(jīng)過18d的培養(yǎng),成功構(gòu)建了菌-藻共生好氧顆粒污泥系統(tǒng)(ABGS).研究表明,在非曝氣條件下,與傳統(tǒng)的AGS相比,ABGS具有更高的生物活性、除污染效能和機(jī)械強(qiáng)度,說明ABGS的穩(wěn)定性更優(yōu).對(duì)ABGS的穩(wěn)定性機(jī)理進(jìn)行分析,發(fā)現(xiàn)在顆?；^程中,胞外聚合物(EPS)特別是緊密結(jié)合層EPS(TB-EPS)中蛋白質(zhì)(PN)含量明顯增加,實(shí)驗(yàn)?zāi)┢谄浜吭黾又?14.4mg/g MLSS,約為AGS的2.8倍.采用三維熒光光譜進(jìn)一步分析EPS的組分,結(jié)果表明TB-EPS中氨基酸、色氨酸、芳香族蛋白質(zhì)、絡(luò)氨酸和色氨酸類物質(zhì)是維持顆粒結(jié)構(gòu)穩(wěn)定性的重要原因.在微生物群落結(jié)構(gòu)方面, ABGS的物種多樣性和群落豐富度更高,原核生物綠彎菌門(Chloroflexi)和浮霉菌門(Planctomycetes)、真核生物綠藻門(Chlorophyta)的富集有利于加強(qiáng)系統(tǒng)的穩(wěn)定性.

菌-藻共生好氧顆粒污泥(ABGS)；穩(wěn)定性；胞外聚合物(EPS)；微生物群落

好氧顆粒污泥(AGS)是在各種選擇壓的驅(qū)動(dòng)作用下形成的微生物聚集體,具有結(jié)構(gòu)致密、沉降性能優(yōu)良、可實(shí)現(xiàn)同步脫氮除磷以及抗沖擊負(fù)荷能力強(qiáng)等優(yōu)點(diǎn)[1],因而被譽(yù)為“21世紀(jì)最具發(fā)展?jié)摿Φ奈鬯锾幚砑夹g(shù)之一”[2-3].然而許多研究發(fā)現(xiàn)在長期運(yùn)行過程中,顆粒結(jié)構(gòu)易失穩(wěn)導(dǎo)致出水水質(zhì)惡化以及機(jī)械曝氣能耗過高等弊端制約了該技術(shù)的大規(guī)模應(yīng)用[4-6].

近年來,有研究提出將AGS技術(shù)與菌-藻共生系統(tǒng)的優(yōu)勢特征進(jìn)行耦合,構(gòu)建菌-藻共生好氧顆粒污泥(ABGS)體系,以克服AGS系統(tǒng)中存在的技術(shù)難題.在ABGS系統(tǒng)中,藻類通過光合作用同化CO2和水中污染物,產(chǎn)生的O2被好氧細(xì)菌用于氧化有機(jī)物,同時(shí)產(chǎn)生CO2供給藻類利用,“菌-藻”之間的共生關(guān)系有利于實(shí)現(xiàn)對(duì)廢水中有機(jī)物和氮磷的高效去除[7].劉琳等[8]在光照序批式反應(yīng)器中培養(yǎng)ABGS,發(fā)現(xiàn)該系統(tǒng)對(duì)于總氮和磷酸鹽的去除效率(50.2%和35.7%)明顯高于AGS系統(tǒng)(32.8%和25.6%).在非曝氣條件下, ABGS系統(tǒng)的除污效能仍然高于AGS系統(tǒng).季斌等[9]構(gòu)建的一種自耦合ABGS系統(tǒng),在非曝氣條件下,在6h內(nèi)對(duì)于有機(jī)物、氨和磷的去除率可達(dá)92.7%、96.8%和87.2%.上述研究表明,與AGS相比,ABGS的沉降性能更優(yōu),系統(tǒng)穩(wěn)定性更強(qiáng),能夠在高效去除污染物的同時(shí)減少曝氣能耗,降低運(yùn)行成本.然而,關(guān)于ABGS系統(tǒng)穩(wěn)定性的機(jī)理目前尚不明確,亟待進(jìn)一步研究.

本文通過探究非曝氣條件下ABGS和AGS的理化特性及污染物去除效能,系統(tǒng)分析ABGS和AGS的穩(wěn)定性差異,并通過考察EPS特性和微生物群落結(jié)構(gòu)的變化規(guī)律,揭示ABGS系統(tǒng)穩(wěn)定性的內(nèi)在機(jī)理.研究結(jié)果可為菌-藻共生好氧顆粒污泥技術(shù)的實(shí)際應(yīng)用提供理論指導(dǎo).

1 材料與方法

1.1 接種微藻與接種污泥

實(shí)驗(yàn)采用小球藻(FACHB-31)和柵藻(FACHB- 416)作為接種藻種,采用實(shí)驗(yàn)室前期培養(yǎng)的成熟AGS作為接種污泥.小球藻、柵藻和接種污泥三者接種體積比為1:2:7.接種后其混合液體積為400mL,藻細(xì)胞密度約為106cell/L,懸浮固體濃度(MLSS)約為3.50g/L,污泥體積指數(shù)(SVI5)為35.10mL/g,葉綠素a/MLSS比值為0.06mg/g.

1.2 實(shí)驗(yàn)裝置與操作條件

本實(shí)驗(yàn)在2個(gè)500mL的錐形瓶中進(jìn)行.實(shí)驗(yàn)組(Rp)為光照條件下培養(yǎng)的ABGS系統(tǒng),其光照強(qiáng)度約為200μmol/(m2·s),光照周期為12h亮相/12h暗相,對(duì)照組(Rc)為避光處理的AGS系統(tǒng).2個(gè)實(shí)驗(yàn)裝置放置于搖床上,振蕩速度為150r/min,溫度控制為(25± 2)℃.

采用模擬生活污水作為進(jìn)水,其組成成分為: 600mg/L COD,60mg/L NH4+-N(NH4Cl),10mg/L PO43--P(K2HPO4/KH2PO4),25mg/L Mg2+(MgSO4×7H2O), 30mg/L Ca2+(CaCl2),1mL/L微量元素[10].每天運(yùn)行2個(gè)周期(12h),運(yùn)行方式包括1min進(jìn)水、715min振蕩、2min沉降和2min排水.體積交換比為50%,水力停留時(shí)間為24h,污泥齡為27d.

1.3 分析項(xiàng)目和方法

取進(jìn)水和出水水樣沉淀分離后,上清液過0.45μm濾膜再進(jìn)行水質(zhì)指標(biāo)檢測,其中化學(xué)需氧量(COD)采用快速消解分光光度法, NH4+-N采用納氏試劑光度法,NO2--N采用N-(1-萘基)-乙二胺光度法, NO3--N采用紫外分光光度法, PO43--P采用鉬酸銨分光光度法.取曝氣末期混合均勻的污泥混合液按照標(biāo)準(zhǔn)方法[11]測定MLSS、混合液揮發(fā)性懸浮固體濃度(MLVSS)、SVI5等污泥指標(biāo).采用數(shù)碼相機(jī)拍攝污泥的表觀形態(tài),采用掃描電子顯微鏡(SEM, Quattro S,捷克)進(jìn)一步觀察顆粒污泥的微觀結(jié)構(gòu).

ABGS中藻類的富集程度通過葉綠素a(Chl-a)的含量進(jìn)行表征,按照Zhao等[12]方法測量.顆粒污泥的相對(duì)強(qiáng)度以污泥的完整性系數(shù)來表示,并根據(jù)Ghangrekar等[13]方法測量:取一定量的顆粒污泥樣品(25mL)置于150mL量筒中靜沉,收集1min內(nèi)沉降至量筒底部的污泥,并將其稀釋至150mL;然后將稀釋后的樣品置于200r/min的搖床震蕩5min;隨即置于150mL量筒中靜沉,測定1min內(nèi)因破碎而未沉于底部的污泥樣品質(zhì)量占顆粒污泥總質(zhì)量的百分比,即為完整性系數(shù).根據(jù)Li等[14]方法對(duì)接種顆粒污泥、Rc和Rp系統(tǒng)內(nèi)顆粒污泥的EPS進(jìn)行由外到內(nèi)的分級(jí)提取,分為松散結(jié)合型EPS(LB-EPS)和緊密結(jié)合型EPS(TB-EPS). EPS樣品中的蛋白質(zhì)(PN)和多糖(PS)分別采用BCA蛋白質(zhì)測定試劑盒(Sigma-Aldrich)和苯酚-硫酸法[15]進(jìn)行定量測定.采用三維熒光光譜儀(FP-6500,日本JASCO公司)記錄EPS樣品的激發(fā)-發(fā)射矩陣光譜圖(EEM),采用平行因子(PARAFAC)建模處理EEM數(shù)據(jù),并使用Matlab R2015a和N-way Toolbox(版本3.20)分析EPS中的熒光組分.

采用16s rRNA和18s rRNA基因高通量測序技術(shù)分析接種顆粒污泥、Rc和Rp成熟顆粒污泥中微生物和藻類群落結(jié)構(gòu)的多樣性.采用E.Z.N.A.?土壤DNA試劑盒(Omega,美國)提取接種顆粒污泥、Rc和Rp中成熟顆粒污泥樣品的DNA,然后按照Zhang等[10]的方法進(jìn)行測序處理和生物信息學(xué)分析.

本研究中的實(shí)驗(yàn)平行重復(fù)3次,結(jié)果以平均值和標(biāo)準(zhǔn)差表示.

2 結(jié)果與討論

2.1 污泥理化特性

如圖1(a)所示, Rp系統(tǒng)中葉綠素a含量呈現(xiàn)顯著增加后趨于穩(wěn)定的變化趨勢.葉綠素a/MLSS比值顯著增加,在第18d達(dá)到峰值0.41mg/g,隨后趨于穩(wěn)定(0.41 ± 0.05) mg/g.結(jié)果表明,接種藻類在Rp系統(tǒng)內(nèi)適應(yīng)良好,不需要補(bǔ)充接種藻類,18d后Rp反應(yīng)器內(nèi)藻類與細(xì)菌實(shí)現(xiàn)了良好的協(xié)同共生,形成了穩(wěn)定的ABGS[8,16],這與Zhang等[17]的研究結(jié)果相近.

圖1(b)為反應(yīng)器內(nèi)污泥MLSS和MLVSS/MLSS的變化情況.初始接種顆粒污泥MLSS為3.50g/L, MLVSS/MLSS比值為0.76,可生化性高.培養(yǎng)過程中,Rp系統(tǒng)內(nèi)MLSS不斷增加,隨后趨于穩(wěn)定(5.25～5.30g/L), MLVSS/MLSS比值增加至0.88; Rc系統(tǒng)內(nèi)MLSS在前3d略有增加,隨后顯著下降至2.04g/L, MLVSS/MLSS比值降低至0.66.分析認(rèn)為,在非曝氣條件下, Rc系統(tǒng)內(nèi)缺氧導(dǎo)致微生物大量死亡,顆粒污泥破碎解體、結(jié)構(gòu)松散,沉降性能較差的污泥易隨出水排出.相比之下,Rp系統(tǒng)內(nèi)顆粒結(jié)構(gòu)更加致密而穩(wěn)定.

圖1(c)為反應(yīng)器內(nèi)顆粒污泥SVI5的變化情況. Rp系統(tǒng)內(nèi)污泥的SVI5在接種初期存在小幅波動(dòng),隨后下降并穩(wěn)定在33.90～36.70mL/g之間.Rc系統(tǒng)內(nèi)的SVI5呈持續(xù)增加的趨勢,在實(shí)驗(yàn)?zāi)┢谏仙?1.85mL/g.結(jié)果表明, ABGS具有良好的沉降性能與可生化性,與之相反的是, AGS的沉降性能未見明顯的恢復(fù)跡象.

圖1(d)為反應(yīng)器內(nèi)顆粒污泥的完整性系數(shù)變化情況.完整性系數(shù)數(shù)值越低表示顆粒污泥的相對(duì)強(qiáng)度越大、結(jié)構(gòu)穩(wěn)定性越強(qiáng)[18]. Rp內(nèi)顆粒的完整性系數(shù)始終維持在2.9%～4.1%范圍內(nèi),在接種初期該值小幅上升后迅速降低至2.9%,說明ABGS系統(tǒng)對(duì)非曝氣的培養(yǎng)條件可以進(jìn)行快速調(diào)整和積極響應(yīng). Rc系統(tǒng)內(nèi)顆粒的完整性系數(shù)從接種時(shí)的3.8%持續(xù)增加到16.7%.以上結(jié)果表明,非曝氣環(huán)境對(duì)AGS顆粒穩(wěn)定性產(chǎn)生了一定負(fù)面影響,但ABGS顆粒污泥在非曝氣條件下仍具有良好的顆粒結(jié)構(gòu)穩(wěn)定性.

2.2 污泥形態(tài)特征

由圖2可知,運(yùn)行9d后Rp系統(tǒng)內(nèi)顆粒污泥逐漸變?yōu)榫G色(圖2(a)),說明綠藻在該反應(yīng)器內(nèi)適應(yīng)性良好,生長速率較快.而此時(shí)Rc系統(tǒng)內(nèi)顆粒污泥的邊緣變得模糊(圖2(e)),分析認(rèn)為在非曝氣條件下缺少適宜的水力剪切力導(dǎo)致了該現(xiàn)象發(fā)生.在實(shí)驗(yàn)進(jìn)行至第54d時(shí), Rp系統(tǒng)內(nèi)顆粒污泥結(jié)構(gòu)致密、形狀規(guī)則(圖2(b)).此時(shí), Rc系統(tǒng)內(nèi)顆粒污泥結(jié)構(gòu)松散、形狀不規(guī)則,部分顆粒污泥的結(jié)構(gòu)出現(xiàn)了解體現(xiàn)象(圖2(f)).

采用SEM進(jìn)一步觀察實(shí)驗(yàn)?zāi)┢趦蓚€(gè)系統(tǒng)內(nèi)顆粒污泥的微觀形態(tài).如圖2c所示, Rp中成熟ABGS具有清晰的球形輪廓和致密光滑的表面結(jié)構(gòu),原生動(dòng)物附著在顆粒污泥表面,表明出水水質(zhì)良好[19].由高倍SEM圖可以觀察到Rp中顆粒表面富集了大量的桿狀菌、鏈球菌和結(jié)構(gòu)完整的藻細(xì)胞,以及少量的絲狀菌,可見大量的孔隙和通道(圖2d),分析認(rèn)為孔隙和通道的存在有利于細(xì)菌的黏附,能夠促進(jìn)營養(yǎng)物質(zhì)、代謝產(chǎn)物和氧氣的傳遞,進(jìn)而有利于保持較高的生物活性[20].然而, Rc中的成熟AGS表面粗糙不平,中心出現(xiàn)裂解,呈現(xiàn)不規(guī)則的顆粒狀結(jié)構(gòu)(圖2g),這與其完整性系數(shù)最大的測量結(jié)果相一致.由高倍SEM圖(圖2h)可以觀察到Rc中顆粒表面存在短棒狀和球狀細(xì)菌,但被大量絲狀菌覆蓋,導(dǎo)致氧氣和營養(yǎng)物質(zhì)傳質(zhì)受阻,核心部位被內(nèi)源降解[21].

圖2 兩個(gè)反應(yīng)器中顆粒污泥的形態(tài)學(xué)觀察

2.3 污染物去除效能

在反應(yīng)器啟動(dòng)階段,兩個(gè)系統(tǒng)對(duì)于污染物的去除效率均存在波動(dòng),這是由于顆粒污泥對(duì)非曝氣條件需要一定的適應(yīng)期.隨后Rp系統(tǒng)中污染物的去除效率明顯提高,并在第18d趨于穩(wěn)定(圖3).與之相反的是, Rc反應(yīng)器的去除效率顯著降低.在相同的進(jìn)水基質(zhì)條件下(詳見1.2節(jié)), Rp中COD、NH4+-N、TN和PO43--P的平均去除效率分別為98.70%、89.81%、87.14%和76.19%,與對(duì)照組Rc相比,分別提高了31.08%、23.97%、30.47%、22.17%.以上結(jié)果表明,在非曝氣條件下,ABGS對(duì)有機(jī)物和氮磷等污染物的去除效果明顯優(yōu)于AGS.

2.4 EPS的變化

2.4.1 EPS含量的變化 由圖4可知,兩個(gè)系統(tǒng)內(nèi)EPS總含量的變化趨勢存在明顯差異. Rp系統(tǒng)中EPS總含量呈持續(xù)增長的趨勢,由最初的121.88mg/ g MLSS逐漸增加至155.99mg/g MLSS,其中LB- EPS含量基本維持穩(wěn)定, TB-EPS含量顯著升高(圖4a). Rc系統(tǒng)中EPS總含量呈持續(xù)下降的趨勢,下降至82.55mg/g MLSS,其中LB-EPS含量小幅度增加, TB-EPS含量急劇減少(圖4b).以上結(jié)果表明, LB- EPS含量增加、TB-EPS含量減少是顆粒污泥穩(wěn)定性出現(xiàn)差異的主要原因,并且TB-EPS對(duì)顆粒穩(wěn)定性的貢獻(xiàn)大于LB-EPS[22].進(jìn)一步分析發(fā)現(xiàn),兩個(gè)系統(tǒng)內(nèi)LB-EPS和TB-EPS中PS含量均未出現(xiàn)明顯變化,而TB-EPS中PN含量變化顯著. Rp中PN含量由最初的85.46mg/g MLSS增加至114.36mg/g MLSS,約為Rc(41.21mg/g MLSS)的2.8倍,研究表明PN在維持顆粒污泥穩(wěn)定性方面具有重要作用[23],當(dāng)顆粒污泥PN/PS值在3～8之間[24],顆粒污泥具有較好的穩(wěn)定性.本研究中, Rp的PN/PS從4.57增加至5.38,Rc的PN/PS由4.57降低至3.64.較高的PN/PS比值表明其污泥表面具有較高的表面疏水性和較低的表面電荷,有助于維持顆粒污泥結(jié)構(gòu)的穩(wěn)定性[25].

圖4 系統(tǒng)中顆粒污泥LB-EPS和TB-EPS含量及PN/PS的變化情況

2.4.2 EPS組分分析 圖5為接種顆粒污泥、Rc和Rp系統(tǒng)內(nèi)顆粒污泥的EPS提取物的熒光光譜圖.根據(jù)Chen等[26]的分類方法,將熒光光譜圖分成5個(gè)區(qū)域:區(qū)域A(Ex>250,Em>380)胡敏酸類物質(zhì);區(qū)域B(Ex>250,Em<380)溶解性微生物副產(chǎn)物,主要是蛋白質(zhì)衍生的氨基酸和色氨酸;區(qū)域C(Ex<250, Em>380)富里酸類物質(zhì);區(qū)域D(Ex<250, 330

圖5 顆粒污泥LB-EPS和TB-EPS的3D-EEM圖譜

如圖6(g-h)所示, TB-EPS中3種組分的熒光強(qiáng)度與LB-EPS相比均有所提高,其中組分1的熒光強(qiáng)度從824.56(LB-EPS)提高至2566.26(TB-EPS),增加了2.11倍,組分2的熒光強(qiáng)度從709.18(LB-EPS)提高至3066.35(TB-EPS),增加了3.32倍.該結(jié)果與前面三維熒光圖譜熒光強(qiáng)度對(duì)比結(jié)果相吻合.此外,可以觀察到在TB-EPS中, Rc中組分1和組分2的熒光強(qiáng)度均低于接種顆粒污泥和Rp中對(duì)應(yīng)組分的熒光強(qiáng)度.結(jié)合AGS和ABGS系統(tǒng)中顆粒污泥的理化特性,得出TB-EPS中組分1氨基酸、色氨酸和芳香族蛋白質(zhì)物質(zhì)、組分2絡(luò)氨酸和色氨酸類物質(zhì)含量的增加是維持顆粒結(jié)構(gòu)穩(wěn)定性的重要原因.

2.5 微生物群落結(jié)構(gòu)

3種顆粒污泥中微生物群落的豐富度和多樣性列于表1.3個(gè)樣品的物種覆蓋率均大于99%,表明測序結(jié)果能較好地反映樣品中微生物分類的真實(shí)性.在非曝氣條件下, Rc和Rp中獲得的具有97%聚類相似性的優(yōu)化序列分別為35805和42742,均大于初始接種顆粒污泥(33813).對(duì)比表1中不同污泥樣品ACE和Chao1指數(shù)可知, Rp系統(tǒng)中微生物種群豐富度高于Rc.此外, Rp系統(tǒng)中Shannon指數(shù)為4.54,高于Rc(4.06)和接種顆粒污泥(3.83), Rp的Simpson指數(shù)為(0.028)小于Rc(0.053)和接種顆粒污泥(0.063).以上結(jié)果可以得出, Rp系統(tǒng)內(nèi)物種多樣性、群落豐富度更高,說明ABGS的形成有利于提高物種多樣性和群落豐富度,進(jìn)而有利于抵御外界不良環(huán)境的干擾以及維持系統(tǒng)的穩(wěn)定性[17].

表1 基于97%相似度聚類的OTU數(shù)目以及微生物群落豐富度和多樣性

在門分類水平上,變形菌門(Proteobacteria)和擬桿菌門(Bacteroidetes)是3個(gè)污泥樣品中的主要優(yōu)勢菌群(如圖7所示).研究表明,這兩類細(xì)菌具有較強(qiáng)的降解有機(jī)物和氨氮的能力[28].ABGS中綠彎菌門(Chloroflexi)的相對(duì)豐度由初始接種污泥的2.31%增加至13.15%.綠彎菌門(Chloroflexi)可以與絲狀菌相互纏繞形成穩(wěn)定的聚合物結(jié)構(gòu),在污泥造粒過程中可作為核心或載體形成污泥顆粒的初始骨架,加固顆粒污泥的結(jié)構(gòu)穩(wěn)定性[29]. Rp的ABGS中浮霉菌門(Planctomycetes)的相對(duì)豐度由初始接種污泥的0.90%增加至1.85%,約是Rc中AGS(0.62%)的3倍.此類細(xì)菌可以亞硝酸鹽作為電子受體,以CO2作為碳源,通過厭氧氨氧化作用獲取能量[30].初始接種污泥中幾乎不存在藍(lán)藻門(Cyanobacteria),而ABGS中藍(lán)藻門(Cyanobacteria)含量約為1.75%.光照會(huì)誘導(dǎo)藍(lán)藻生長,但系統(tǒng)內(nèi)綠藻的生長以及交替的明暗條件限制了藍(lán)藻的過度生長[8,31].

在綱分類水平上,γ-變形菌綱(Gammaproteobacteria)、α-變形菌綱(Alphaproteobacteria)和擬桿菌綱(Bacteroidia)仍是兩個(gè)系統(tǒng)內(nèi)的優(yōu)勢菌群,但其相對(duì)豐度存在差異.其中, Rc中與EPS分泌有關(guān)的γ-變形菌綱(Gammaproteobacteria)的相對(duì)豐度由接種污泥的56.84%降低至32.59%,這可能是導(dǎo)致EPS含量下降的主要原因(圖4)[32].此外, ABGS中屬于綠彎菌門的厭氧繩菌綱(Anaerolineae)其相對(duì)豐度增加了4.7倍.這類細(xì)菌可以有效降解碳水化合物[33],同時(shí)該類細(xì)菌可參與到生物除磷過程中[34].以上結(jié)果可以得出,ABGS的形成在一定程度上改變了系統(tǒng)內(nèi)特征菌群的相對(duì)豐度,選擇性地促進(jìn)或者抑制某些特定的細(xì)菌種類,從而構(gòu)建了穩(wěn)定的菌藻共生環(huán)境.

圖7(c)顯示了Rp系統(tǒng)中的藻類在屬水平上的相對(duì)豐度.從屬分類水平上來看, Rp中真核藻類群落主要由綠藻綱的柵藻()和小球藻()組成.對(duì)比發(fā)現(xiàn),柵藻()的相對(duì)豐度(48.34%)高于小球藻()的相對(duì)豐度(37.95%),這與劉琳等[8]研究結(jié)果相似.這兩種藻類均具有高效同化氮、磷的能力[35],可在黑暗階段去除COD、氨和磷酸鹽等營養(yǎng)物質(zhì)[36].此外, Rp中硅藻門(Bacillariophyta)下菱形藻屬()的相對(duì)豐度為1.31%,有研究表明ABGS中的快速增長可以促進(jìn)營養(yǎng)物質(zhì)的去除[37].因此,ABGS具有良好的去除污染物效能,可能是由于這3種藻屬的富集和生長.本文 ABGS系統(tǒng)中有接近12%的藻類物種未分類,未分類的藻類物種是否影響菌-藻共生體系穩(wěn)定性,需要進(jìn)一步研究其種類和功能.

3 結(jié)論

3.1 在非曝氣條件下成功構(gòu)建了ABGS系統(tǒng),與傳統(tǒng)的AGS相比,ABGS的MLSS穩(wěn)定在5.25～5.30g/L、SVI5穩(wěn)定在33.90～36.70mL/g、完整性系數(shù)維持在2.9%～4.1%,此外, ABGS對(duì)COD、NH4+- N、TN和PO43--P的平均去除率與AGS相比提高了22%～31%,表明ABGS具有更加優(yōu)良的沉降性能、更致密的結(jié)構(gòu)、更高的生物活性,更優(yōu)異的除污效能以及更高的機(jī)械強(qiáng)度.

3.2 通過分析EPS的含量可知, ABGS中TB- EPS對(duì)顆粒結(jié)構(gòu)穩(wěn)定性的貢獻(xiàn)大于LB-EPS, TB- EPS中的PN含量明顯增加,從85.46mg/g MLSS增加至114.36mg/g MLSS,約為Rc(41.21mg/g MLSS)的2.8倍, PN含量的增加提高了污泥的表面疏水性,有助于微生物相互凝聚以及維持穩(wěn)定的顆粒結(jié)構(gòu).

3.3 進(jìn)一步分析EPS的熒光組分,TB-EPS中氨基酸和色氨酸及芳香族蛋白質(zhì)物質(zhì)、絡(luò)氨酸和色氨酸類物質(zhì)是維持顆粒結(jié)構(gòu)穩(wěn)定性的重要原因.

3.4 與AGS相比, ABGS的物種多樣性和群落豐富度更高,原核生物綠彎菌門(Chloroflexi)和浮霉菌門(Planctomycetes)、真核生物柵藻()和小球藻()是系統(tǒng)中富集的優(yōu)勢物種,菌藻之間的共生關(guān)系有利于加強(qiáng)系統(tǒng)穩(wěn)定性.

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The stability mechanism of algal-bacterial granular sludge.

LIU Yi1, ZHANG Bing1, SHI Wen-Xin1*, ZHU Yi-chun2, LIU Zu-wen2

(1.Key Laboratory of Three Gorges Reservoir Region’s Eco-Environment, Ministry of Education, College of Environment and Ecology, Chongqing University, Chongqing 400045, China；2.School of Civil and Surveying&Mapping Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, China)., 2022,42(4)：1696～1705

A stable algal-bacterial granular sludge (ABGS) system was established rapidly within 18 days by inoculating with aerobic granules and targeted algae (and) under non-aeration conditions. The results indicated that ABGS had higher biological activity, better nutrients removal performance, and higher mechanical strength than the conventional AGS, indicating the superior stability of ABGS. Moreover, the content of protein (PN) in extracellular polymeric substances (EPS), especially tightly bound layer EPS (TB-EPS), was found increasing significantly during the granulation. Specifically, the PN content of 114.4mg/g MLSS at the end of the operation was about 2.8 times higher than that of AGS. Further analysis of EPS components by three-dimensional fluorescence spectroscopy showed that amino acids, tryptophan, aromatic proteins, complex amino acids and tryptophan-like substances in TB-EPS were conducive to maintain the structural stability of granular sludge. In terms of microbial community structure, the ABGS had a higher microbial diversity and community richness than AGS. The enrichment of the prokaryotic Chloroflexi and Planctomycetes, and the eukaryotic Chlorophyta was beneficial to enhance the stability of the system.

algal-bacterial granular sludge (ABGS)；system stability；extracellular polymeric substances (EPS)；microbial community structure

X703

A

1000-6923(2022)04-1696-10

劉 怡(1997-),女,重慶合川人,重慶大學(xué)碩士研究生,研究方向?yàn)槲鬯锾幚砑夹g(shù).

2021-09-01

國家自然科學(xué)基金資助項(xiàng)目(51778172,52000014)

*責(zé)任作者, 教授, swx@hit.edu.cn