錢飛躍,王 琰,王建芳*,王書永,沈耀良(.蘇州科技學(xué)院環(huán)境科學(xué)與工程學(xué)院,江蘇 蘇州25009;2.江蘇省環(huán)境科學(xué)與工程重點實驗室,江蘇 蘇州 25009;3.江蘇省水處理技術(shù)與材料協(xié)同創(chuàng)新中心,江蘇蘇州 25009)
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長期儲存亞硝化顆粒污泥的活化及菌群結(jié)構(gòu)變化
錢飛躍1,2,3,王 琰1,王建芳1,2,3*,王書永1,沈耀良1,2,3(1.蘇州科技學(xué)院環(huán)境科學(xué)與工程學(xué)院,江蘇 蘇州215009;2.江蘇省環(huán)境科學(xué)與工程重點實驗室,江蘇 蘇州 215009;3.江蘇省水處理技術(shù)與材料協(xié)同創(chuàng)新中心,江蘇蘇州 215009)
摘要:采用無機(jī)人工配水,通過逐級提高進(jìn)水氨氮負(fù)荷(0.32~0.64kg/(m3?d))和設(shè)定合適的初始游離氨濃度(3.7~7.2mg/L),在SBR反應(yīng)器中對常溫(24~29℃)下儲存1a的亞硝化顆粒污泥(NGS)進(jìn)行了活化,并使用Miseq高通量測序技術(shù)分析了污泥中微生物多樣性的變化情況.結(jié)果表明, NGS的亞硝化性能可在短時間內(nèi)恢復(fù).運行8d后,反應(yīng)器的氨氮去除率達(dá)到95%以上,亞硝態(tài)氮累積率超過了80%,但污泥粒徑持續(xù)減小,胞外聚合物(EPS)含量明顯降低.活化至第20d,NGS的氨氮比去除速率和亞硝態(tài)氮比累積速率分別達(dá)到24.6mg/(gVSS?h)、23.8mg/(gVSS?h),平均粒徑穩(wěn)定在0.5mm左右.在活化期間,絕大部分厭氧、異養(yǎng)菌屬被洗脫,污泥的微生物多樣性顯著降低.Nitrosomonas等氨氧化菌的相對豐度由活化前的1%上升至約58%,同時,Nitrospira等硝化菌的生長受到了選擇性抑制.這意味著即使經(jīng)歷長期的常溫儲存,NGS仍可作為SBR的接種污泥,實現(xiàn)反應(yīng)器的快速啟動.
關(guān)鍵詞:亞硝化顆粒污泥;活化;微生物多樣性;優(yōu)勢菌群
* 責(zé)任作者, 副教授, wjf302@163.com
有研究表明,通過培養(yǎng)具有規(guī)則三維結(jié)構(gòu)、優(yōu)良沉降性能和極高氨氧化菌(AOB)豐度的亞硝化顆粒污泥(NGS),可獲得高效的亞硝態(tài)氮累積,有助于實現(xiàn)OLAND、CANON等新型生物脫氮工藝的穩(wěn)定運行[1-3].由于AOB等自養(yǎng)菌的世代時間較長,自凝聚能力偏弱,對環(huán)境變化較為敏感,因此,基于絮狀污泥培養(yǎng)高性能的NGS存在很大難度[4-5].相比之下,利用存儲污泥的快速活化,可顯著縮短反應(yīng)器的啟動周期,有效突破限制NGS工程化應(yīng)用的技術(shù)瓶頸[6-7].然而,好氧顆粒污泥經(jīng)歷長期閑置或儲存后,會出現(xiàn)優(yōu)勢菌衰減、厭氧內(nèi)核水解、絲狀菌過度生長等功能結(jié)構(gòu)的破壞性變化,該過程受到儲存時間、營養(yǎng)基質(zhì)和環(huán)境溫度等因素的影響[8-9].與冷藏(4℃)和冷凍(<-25℃)條件相比,好氧顆粒污泥在常溫下儲存更易發(fā)生解體和失活,活化難度更高[10-11].
為進(jìn)一步探明儲存污泥的活化性能,本研究將常溫下儲存1a的NGS作為接種污泥,并選取合適的運行工況啟動SBR反應(yīng)器,在系統(tǒng)考察污泥亞硝化性能恢復(fù)、外觀形態(tài)與胞外聚合物(EPS)組成變化的同時,采用Miseq高通量測序技術(shù)對活化前后NGS的菌群結(jié)構(gòu)進(jìn)行了分析.
1.1 實驗裝置與運行條件
實驗裝置采用圓柱形SBR反應(yīng)器,有效容積為4L(高徑比10/1),由有機(jī)玻璃制成.反應(yīng)器底部裝有曝氣頭,反應(yīng)期間控制曝氣量為3L/min(表面上升流速1cm/s),以提供充足的溶解氧(DO)和水力剪切力.反應(yīng)器排水比設(shè)為1/2,接種污泥量(MLSS)約4100mg/L.采用時間程序控制器實現(xiàn)對間歇操作的自動控制,單個周期為3h,其中,7min進(jìn)水,排水和閑置共3min,曝氣時間和沉降時間的設(shè)置如表1所示.活化期間,SBR始終置于恒溫水浴箱中,溫度控制在28~30℃.
1.2 接種污泥性質(zhì)
接種污泥為常溫條件下長期儲存的亞硝化顆粒污泥.NGS在儲存前呈規(guī)則的棕黃色顆粒,氨氮容積負(fù)荷2.0kg/(m3·d),亞硝態(tài)氮累積率可達(dá)(85±5)%,形態(tài)特征如表2所示[12].以無機(jī)磷酸鹽緩沖溶液(pH約7.6)為基質(zhì),NGS在24~29℃下儲存1a后,大部分顆粒依舊呈現(xiàn)光滑的圓球狀結(jié)構(gòu),但平均粒徑和MLVSS/MLSS均明顯下降,污泥體積指數(shù)(SVI)略有增加,顏色由存儲前的棕黃色變?yōu)榛疑?上層)和黑色(下層).污泥經(jīng)歷長時間內(nèi)源呼吸和厭氧消化后,無機(jī)化程度提高,可能會產(chǎn)生甲烷、硫化氫等氣體,因而帶有輕微的臭雞蛋氣味[11,13].

表1 SBR反應(yīng)器的操作運行參數(shù)Table 1 Operating parameters of SBR reactor

表2 不同狀態(tài)下,亞硝化顆粒污泥的性狀特征Table 2 Characteristics of the nitrosation granular sludge under different conditions
1.3 反應(yīng)器進(jìn)水
進(jìn)水采用人工配制的無機(jī)含氮廢水,以氯化銨為氮源(80~160mgN/L).通過投加碳酸氫鈉,調(diào)節(jié)溶液pH至8.0.其他成分還包括磷酸二氫鉀/磷酸氫二鉀(18mgP/L)、硫酸鎂(49mg/L)、氯化鈣(60mg/L)、氯化鐵(1.5mg/L)及必需微量元素.
1.4 常規(guī)分析方法
MLSS、MLVSS、SVI、NH4+-N、NO2--N、NO3--N等指標(biāo)采用國標(biāo)法測定.溶液pH、DO分別使用PB-10型pH計(Sartorius,Germany)和H1946N型溶解氧測定儀(WTW,U.S.)測定.污泥形態(tài)通過CX41型顯微鏡(OLYMPUS,Japan)進(jìn)行觀察.
粒徑分布采用篩分法測算.定期從反應(yīng)器中取出污泥樣品,經(jīng)生理鹽水反復(fù)清洗后,依次通過孔徑2.50mm,1.60mm,1.25mm,0.80mm,0.50mm 和0.30mm的分樣篩,并計算各粒徑區(qū)間樣品占總質(zhì)量的百分比.
采用甲醛-NaOH法[14]對顆粒污泥的EPS進(jìn)行提取,其主要包含蛋白質(zhì)(PN)和多糖(PS)組分.PN、PS含量分別采用苯酚-硫酸法和改進(jìn)Lowry法測定.
1.5 微生物高通量測序分析
取適量污泥樣品,使用E.Z.N.A Soil DNA 試劑盒(Omega Bio-tek,Norcross,GA,U.S.)提取微生物總DNA.以16S rRNA V3~V4區(qū)內(nèi)338F (5'-ACTCCT ACGGGAGGCAGCA-3')和806R (5'-GGACTAC HVGGGTWTCTAA T-3')為特征引物, 采用20μL混合反應(yīng)體系,在GeneAmp 9700 (ABI) 型PCR擴(kuò)增儀上完成目標(biāo)片段擴(kuò)增.反應(yīng)程序為95℃預(yù)變性2min,95℃變性30s, 55℃退火30s, 72℃延伸30s,25個循環(huán)后,72℃延伸5min.每個樣品重復(fù)3次.
使用AxyPrepDNA凝膠回收試劑盒(Axygen,Union City,CA,U.S.)對PCR擴(kuò)增產(chǎn)物進(jìn)行回收.基于Illumina Miseq PE300平臺,委托上海美吉生物醫(yī)藥科技有限公司完成對PCR擴(kuò)增產(chǎn)物的高通量測序.在多樣性評估的基礎(chǔ)上,采用Qiime軟件進(jìn)行微生物分類學(xué)分析.
2.1 亞硝化性能的恢復(fù)
考慮到接種污泥中微生物長期處于內(nèi)源代謝狀態(tài),活性較低,因此,采用較低的進(jìn)水氨氮負(fù)荷(0.32kg/(m3·d))啟動SBR反應(yīng)器,不投加任何有機(jī)物,保持DO在4mg/L以上,水溫為28℃.同時,控制進(jìn)水pH值為8.0~8.1,確保各周期初始的游離氨(FA)濃度在3.7~6.4mg/L之間,以選擇性抑制Nitrobacter、Nitrospira等硝化菌(NOB)的生長[15-17].如圖1所示,在第1~8d內(nèi),反應(yīng)器對氨氮去除率逐漸增大,最終達(dá)到95%以上,亞硝態(tài)氮累積率超過80%.此后,分階段將進(jìn)水氨氮負(fù)荷提高至0.64kg/(m3·d),初始FA濃度升至約7.2mg/L,反應(yīng)器出水中亞硝態(tài)氮濃度逐級增大,剩余氨氮和硝態(tài)氮濃度分別低于0.5mg/L和15mg/L, 亞硝態(tài)氮累積率穩(wěn)定在90%以上.

圖1 顆粒污泥亞硝化性能的變化Fig.1 Ammonia oxidizing performance of nitrosation granular sludge

圖2 活化20d后,NGS在批次實驗中的氮轉(zhuǎn)化性能Fig.2 Nitrogen transformation after 20days reactivation of NGS
氨氮比去除速率、亞硝態(tài)氮比累積速率等是表征污泥亞硝化性能的重要參數(shù).本研究通過批次試驗(初始NH4+-N 85mg/L,pH 8.0,水溫28℃),對活化20d后的NGS性能進(jìn)行了考察,結(jié)果如圖2所示.反應(yīng)75min后,NGS對氨氮的去除率接近100%.在此期間,氨氮去除與亞硝態(tài)氮、硝態(tài)氮累積過程符合零級動力學(xué)特性,這與Cydzik-Kwiatkowska[18]的研究結(jié)果一致.NGS的氨氮比去除速率[μ(NH4+-N)]、亞硝態(tài)氮比累積速率[μ(NO2--N)]和硝酸氮比累積速率[μ(NO3--N)]分別為24.6mg/(gVSS·h)、23.8mg/(gVSS·h)、1.5mg/ (gVSS·h),亞硝態(tài)氮累積率達(dá)到95%.這意味著NGS的亞硝化性能已得到良好的恢復(fù).需要指出的是,本研究采用無機(jī)人工配水作為NGS的活化基質(zhì),更有利于實現(xiàn)AOB的高度富集,其氨氮去除效能要遠(yuǎn)優(yōu)于鄭照明等[19]基于城市生活污水培養(yǎng)的亞硝化顆粒污泥[μ(NH4+-N)=9.8mg/ (gVSS·h)].
2.3 污泥形態(tài)與EPS組成的變化
在活化過程中,顆粒污泥的外觀形態(tài)也發(fā)生了顯著變化.反應(yīng)器啟動僅2d,污泥顏色便由長期放置后的黑灰色變?yōu)榈攸S色.如圖3所示,顆粒解體現(xiàn)象明顯,在第0~12d內(nèi),污泥平均粒徑由1.50mm迅速降至0.80mm以下,隨后穩(wěn)定在0.5mm左右.

圖3 亞硝化顆粒污泥的形態(tài)變化Fig.3 Morphological variation of nitrosation granular sludge
由圖4可知,接種污泥中粒徑在1.25mm以上的顆粒質(zhì)量百分比為61.2%,粒徑小于0.3mm的污泥量極少.活化12d后,粒徑在0.3~0.8mm的污泥占到總量的69.4%,粒徑在1.6mm以上的顆粒基本消失.活化20d后,粒徑在0.3~0.5mm的污泥量超過了50%. Gao等[20]從改善氧傳質(zhì)條件的角度認(rèn)為,好氧顆粒污泥的最佳尺寸應(yīng)小于0.5mm.對于NGS而言,AOB等自養(yǎng)菌的生長速度緩慢,形成的顆粒結(jié)構(gòu)更加致密,傳質(zhì)受限更為嚴(yán)重,因此,最佳的粒徑尺寸相對較小[6].

圖4 亞硝化顆粒污泥粒徑分布的變化Fig.4 Variation of particle size distribution of nitrosation granular sludge

圖5 亞硝化顆粒污泥MLSS和SVI值的變化Fig.5 Variation of MLSS and SVI values of nitrosation granular sludge
Gao等[10]的研究表明,好氧顆粒污泥在常溫條件下儲存時,微生物較強(qiáng)的內(nèi)源呼吸會導(dǎo)致大量細(xì)胞水解,胞外聚合物含量增多,顆粒結(jié)構(gòu)變得松散.在水力剪切和高選擇壓的共同作用下,污泥解體產(chǎn)生的絮體和沉降性較差的顆粒將隨水流排出,反應(yīng)器內(nèi)MLSS在初始階段快速降至約3000mg/L,SVI值有所增大,見圖5.另外,洗脫過量的EPS(尤其是凝膠型多糖)將有助于降低基質(zhì)傳遞阻力,促進(jìn)AOB在顆粒表面的進(jìn)一步富集[21-22].隨著污泥活性的逐漸恢復(fù),EPS總量有所減少,最終將至初始值的72.6%,PN/PS約為1.4,如表3所示.與異養(yǎng)微生物相比,AOB等自養(yǎng)菌分泌EPS的能力較弱,因此,NGS的EPS總量勢必低于普通好氧顆粒污泥的水平[23-24].

表3 亞硝化顆粒污泥EPS組成的變化情況Table 3 Variation of EPS composition of nitrosation granular sludge
2.3 微生物菌群結(jié)構(gòu)的變化
利用Miseq高通量測序平臺對顆粒污泥中微生物多樣性進(jìn)行分析.高達(dá)99.89%的覆蓋率表明,測序結(jié)果能真實反映樣品中的菌群分布情況.在活化前后,NGS中的細(xì)菌分別從屬于24個門、47個綱、116個屬和18個門、40個綱、107個屬.由Chao1和ACE指數(shù)可知,活化20d的污泥擁有更高的微生物物種豐度.同時,隨著亞硝化性能的恢復(fù)與提升,NGS中微生物多樣性有所降低,表現(xiàn)為Shannon指數(shù)的減小和Simpson指數(shù)的增大,如表4所示.
由圖6可知,活性污泥中常見的Proteobacteria門在兩組樣品中均占居主導(dǎo)地位,但長期儲存的顆粒污泥中屬嗜鹽異養(yǎng)菌的α-proteobacteria綱和γ-proteobacteria綱比例更高,活化后NGS中β-proteobacteria綱則占到了真細(xì)菌總量的61.6%,后者幾乎覆蓋了所有類型的AOB[7,25].在活化過程中,接種污泥經(jīng)歷了由厭氧儲存到好氧反應(yīng)、內(nèi)源呼吸到硝化增殖的環(huán)境劇變,顆粒結(jié)構(gòu)發(fā)生了明顯解體,部分微生物以絮體的形式隨水流排出,優(yōu)勢菌群完成了更替.活化20d后,厭氧微生物Synergistia綱[26]、Anaerolineae 綱[27]、Phycisphaerae綱[28]、vadinHA17綱[29]和Acidobacteria綱[30]等的相對豐度大幅降低,甚至呈現(xiàn)未檢出狀態(tài),同時,與EPS分泌密切相關(guān)的Flavobacteria[7]明顯增多,豐度值由0.07%升至3.84%.

表4 活化前后,NGS中微生物豐度與多樣性情況(相似度97%)Table 4 Microbial abundance and diversity of NGS before and after the reactivation (similarity degree 97%)

圖6 活化前后,亞硝化顆粒污泥中各菌群在綱級別上的相對豐度Fig.6 Relative abundances of different microbial classes in NGS before and after the reactivation
在貧營養(yǎng)條件下,AOB、NOB等自養(yǎng)菌的維持能更低、酶活性更高、衰減速率更慢,有利于在與異養(yǎng)菌的生存競爭中占據(jù)優(yōu)勢[2].Wang等[21]發(fā)現(xiàn),當(dāng)C/N=200/80時,好氧顆粒污泥中氨氧化細(xì)菌Nitrosomonas和硝化細(xì)菌Nitrospira的活化速度明顯快于異養(yǎng)微生物,前者僅需11d即可完全恢復(fù)至儲存前的狀態(tài).表5給出了活化前后污泥樣品中主要菌屬的相對豐度.由于采用無機(jī)含氮配水,以Nitrosomonas和Nitrosomonadaceae_ uncultured為代表的AOB取代Synergistaceae、Pseudorhodobacter、Anaerolineaceae、Thiobacillus、Limnobacter和Comamonadaceae等厭氧異養(yǎng)型菌屬,成為顆粒污泥中的優(yōu)勢菌群. AOB的相對豐度由活化前的1%上升至58%左右,高于大多數(shù)硝化顆粒污泥中AOB的豐度值19.0%~ 60.6%[18,24,27,31].同時,Nitrospira等NOB的生長得到了有效抑制.

表5 活化前后,顆粒污泥中主要菌屬的相對豐度Table 5 Relative abundances of main microbial genera in NGS before and after the reactivation
總之,本研究通過采取逐級提高進(jìn)水氨氮負(fù)荷、設(shè)定合適的初始FA濃度、控制水力剪切和高選擇壓等措施,較好地實現(xiàn)了富集AOB功能菌、抑制NOB生長和優(yōu)化顆粒結(jié)構(gòu)等多重目標(biāo).
3.1 通過采取逐級提高進(jìn)水氨氮負(fù)荷(0.32~ 0.64kg/(m3·d))、設(shè)定合適的FA濃度(3.7~ 7.2mg/L)、控制水力剪切和高選擇壓等措施,在20d內(nèi)成功活化了常溫(24~29℃)下放置1a的亞硝化顆粒污泥.最終,NGS的氨氮比去除速率(μ(NH4+-N))和亞硝態(tài)氮比累積速率(μ(NO2--N))分別達(dá)到了24.6mg/(gVSS·h)、23.8mg/(gVSS·h),反應(yīng)器出水中亞硝態(tài)氮累積率超過了90%.
3.2 在活化過程中,顆粒污泥出現(xiàn)解體現(xiàn)象,EPS總量持續(xù)減少.活化20d后,污泥平均粒徑穩(wěn)定在0.50mm左右,粒徑在0.3~0.5mm的污泥量超過了50%,EPS總量減少至初始值的72.6%, PN/PS約為1.4.
3.3 隨著NGS亞硝化性能的恢復(fù)與提升,微生物多樣性顯著降低.在厭氧、異養(yǎng)菌洗脫和氨氧化菌增殖的共同作用下,Nitrosomonas成為了優(yōu)勢菌屬,其相對豐度由活化前的1%上升至58%左右,同時,Nitrospira等硝化菌的生長得到了有效抑制.
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Reactivation performance of nitrosation granular sludge after long-term storage and microbial community variation.
QIAN Fei-yue1,2,3, WANG Yan1, WANG Jian-fang1,2,3*, WANG Shu-yong1, SHEN Yao-liang1,2,3(1.School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou 215009, China;2.Jiangsu Key Laboratory of Environmental Science and Engineering, Suzhou 215009, China;3.Jiangsu Collaborative Innovation Center of Technology and Material of Water Treatment, Suzhou 215009, China). China Environmental Science, 2016,36(4):1052~1058
Abstract:The reactivation performance of nitrosation granular sludge (NGS), which had been stored at 24~29℃ for a long-term of 1a, was investigated in a sequencing batch reactor (SBR) fed with inorganic synthetic wastewater, via the gradually increasing of the influent ammonia nitrogen loading from 0.32 to 0.64kg/(m3·d) and initial concentration of free ammonia from 3.7 to 7.2mg/L. High throughput sequencing technology of Miseq was also employed to analyze the variation of microbial community before and after the reactivation. Results showed that the stored NGS could be reactivated in a short period of 8days, since the removal effciency of ammonia nitrogen and the accumulation ratio of nitrite nitrogen were higher than 95% and 80%, respectively. Meanwhile, both sludge particle size and extracellular polymer substances (EPS) contents decreased significantly. After 20days reactivation, the specific ammonia nitrogen removal rate of 24.6mg/(gVSS·h) and the specific nitrite accumulation rate of 23.8mg/(gVSS·h) were observed, while average particle size of NGS remained at 0.5mm. During this period, the microbial diversity of NGS decreased obviously, ascribed to the washing out of most of anaerobic and heterotrophic bacteria. The relative abundance of ammonia-oxidizing bacteria, such as Nitrosomonas ect., increased from 1% to 58%, and the growth of nitrite-oxidizing bacteria was inhibited selectively. It indicated that the NGS after a long-term storage could be inoculated in SBR to achieve its rapid start-up.
Key words:nitrosation granular sludge;reactivation;microbical diversity;dominant bacteria community
作者簡介:錢飛躍(1986-),男,江西省玉山縣人,講師,博士,主要從事水污染控制化學(xué)領(lǐng)域的研究.發(fā)表科技論文10余篇..
基金項目:國家自然科學(xué)基金(51308367);江蘇省高校自然科學(xué)研究基金(15KJB610013);校級研究生創(chuàng)新項目(SKCX14_031);校級科研基金(XKY201006);江蘇高校優(yōu)勢學(xué)科建設(shè)工程
收稿日期:2015-09-23
中圖分類號:X703
文獻(xiàn)標(biāo)識碼:A
文章編號:1000-6923(2016)04-1052-07