周洪政,劉 平, 張 靜,劉 春,陳曉軒,張 磊

微氣泡臭氧催化氧化-生化耦合處理難降解含氮雜環(huán)芳烴

周洪政,劉 平, 張 靜,劉 春*,陳曉軒,張 磊

(河北科技大學(xué)環(huán)境科學(xué)與工程學(xué)院,河北省污染防治生物技術(shù)重點(diǎn)實(shí)驗(yàn)室,河北石家莊 050018)

采用微氣泡臭氧催化氧化-生化耦合工藝對(duì)煤化工廢水生化出水進(jìn)行深度處理,考查了污染物去除性能,并分析了處理過(guò)程中含氮雜環(huán)芳烴類污染物降解和廢水可生化性變化.結(jié)果表明,微氣泡臭氧催化氧化對(duì)煤化工廢水生化出水COD平均去除率和去除負(fù)荷分別為26.4%和1.46kg/(m3·d),并將廢水BOD5/COD值由0.038提高至0.30,從而改善后續(xù)生化處理COD去除性能,使得COD總?cè)コ蔬_(dá)到62.4%,顯著優(yōu)于單獨(dú)生化處理.微氣泡臭氧催化氧化降解含氮雜環(huán)芳烴后釋放氨氮,其在后續(xù)生化處理中被有效去除.此外,耦合處理對(duì)廢水UV254的總?cè)コ士蛇_(dá)68.9%.對(duì)耦合處理過(guò)程中廢水GC-MS、紫外-可見(jiàn)吸收光譜和三維熒光光譜進(jìn)行分析,結(jié)果表明,含氮雜環(huán)芳烴是煤化工廢水生化出水中主要難降解污染物.同時(shí)證實(shí)微氣泡臭氧催化氧化可有效降解去除含氮雜環(huán)芳烴,生成小分子有機(jī)物,提高廢水可生化性.

微氣泡；臭氧催化氧化；生化處理；含氮雜環(huán)芳烴；煤化工廢水

煤化工廢水水量大、水質(zhì)復(fù)雜,含有大量難降解有毒有害物質(zhì).含氮雜環(huán)芳烴類有機(jī)物是煤化工廢水中典型難降解有機(jī)污染物[1-3],傳統(tǒng)生化處理難以對(duì)其進(jìn)行有效降解,使得煤化工廢水生化處理出水仍屬于典型有毒有害生物難降解工業(yè)廢水[4].因此,對(duì)煤化工廢水生化出水進(jìn)行深度處理,去除包括含氮雜環(huán)芳烴類有機(jī)物在內(nèi)的難降解有毒有害污染物,對(duì)于減輕煤化工廢水的環(huán)境危害極為重要[5-6].

近年來(lái),高級(jí)氧化技術(shù)(AOPs)在煤化工廢水深度處理中逐漸受到關(guān)注,包括Fenton氧化和臭氧催化氧化[7-9],以破壞和去除廢水中的難降解有毒有害污染物,并提高廢水的可生化性.同時(shí),工業(yè)廢水深度處理通?？紤]將臭氧氧化處理與生化處理相結(jié)合[10-12],以降低廢水處理成本,其中臭氧氧化處理是決定污染物去除效率的主要因素.目前,微氣泡技術(shù)在強(qiáng)化臭氧氣液傳質(zhì)和提高臭氧利用效率及氧化能力方面表現(xiàn)出一定優(yōu)勢(shì),因此基于微氣泡臭氧氧化處理難降解污染物日益受到關(guān)注.研究者采用微氣泡臭氧氧化處理染料、紡織、化纖等難降解工業(yè)廢水,均證實(shí)臭氧利用率可達(dá)到99%以上,且微氣泡臭氧可促進(jìn)產(chǎn)生羥基自由基,從而顯著增強(qiáng)氧化能力[13-17].

本研究采用微氣泡臭氧催化氧化-生化耦合工藝,對(duì)某實(shí)際煤化工廢水生化出水進(jìn)行深度處理.水質(zhì)分析表明,該廢水生化出水存在大量含氮雜環(huán)芳烴類污染物,可生化性極差,傳統(tǒng)曝氣生物濾池(BAF)對(duì)其COD去除率僅6.4%,難以采用生化工藝直接處理.本研究采用微氣泡臭氧催化氧化含氮雜環(huán)芳烴類污染物,提高廢水可生化性并去除部分COD,而后采用生化處理進(jìn)一步去除COD和氨氮.此外,還考察了微氣泡臭氧催化氧化-生化耦合處理去除污染物性能,并分析了處理過(guò)程中含氮雜環(huán)芳烴類污染物降解和可生化性變化,以期為該耦合工藝應(yīng)用于煤化工廢水深度處理和含氮雜環(huán)芳烴類污染物去除提供參考.

1 材料與方法

1.1 實(shí)驗(yàn)裝置

實(shí)驗(yàn)裝置流程圖如圖1所示.實(shí)驗(yàn)系統(tǒng)包括不銹鋼微氣泡臭氧催化氧化反應(yīng)器(MOR)和有機(jī)玻璃生化反應(yīng)器(BR).MOR為密閉帶壓反應(yīng)器,內(nèi)部填充3層5′5mm煤質(zhì)柱狀顆粒活性炭床層作為催化劑,空床有效容積為25L,催化劑床層填充率為28.0%.BR內(nèi)部同樣填充3層5′5mm煤質(zhì)柱狀顆?；钚蕴看矊幼鳛樯锾盍?空床有效容積為42L,填料床層填充率為28.6%.試驗(yàn)系統(tǒng)以純氧為氣源,通過(guò)臭氧發(fā)生器(石家莊冠宇)產(chǎn)生臭氧氣體,與廢水和MOR循環(huán)水混合后,進(jìn)入微氣泡發(fā)生器(北京晟峰恒泰科技有限公司)產(chǎn)生臭氧微氣泡,從底部進(jìn)入MOR進(jìn)行微氣泡臭氧催化氧化反應(yīng).反應(yīng)后氣-水混合物在壓力作用下從底部進(jìn)入BR,進(jìn)一步進(jìn)行生化處理.BR內(nèi)生化處理由臭氧產(chǎn)生及分解過(guò)程所剩余氧氣提供溶解氧(DO),無(wú)需曝氣.

1.2 廢水水質(zhì)

表1 煤化工廢水生化出水水質(zhì)

本研究所處理廢水為實(shí)際煤化工廢水提取甲醇、乙醇等物質(zhì)后,經(jīng)“UASB+生物接觸氧化”工藝處理后的出水.處理過(guò)程中,廢水水質(zhì)見(jiàn)表1.

1.3 實(shí)驗(yàn)過(guò)程

MOR水力停留時(shí)間為1h,微氣泡臭氧進(jìn)氣流量為2L/min,臭氧濃度為30.3mg/L,平均進(jìn)水COD負(fù)荷為4.75kg/(m3·d),臭氧投加量和進(jìn)水COD量之比為0.73mg/mg,平均運(yùn)行溫度為26.7℃.BR接種該廢水處理生物接觸氧化池污泥,污泥接種量(MLSS)約為4g/L.采用排泥法掛膜,促進(jìn)填料上生物膜的形成,而后開(kāi)始連續(xù)穩(wěn)定運(yùn)行.BR水力停留時(shí)間為6h(MOR多余水量通過(guò)旁路排出),平均進(jìn)水COD負(fù)荷為0.58kg/(m3·d),平均運(yùn)行溫度為22.2℃.

運(yùn)行過(guò)程中,對(duì)MOR和BR進(jìn)出水COD、BOD5、氨氮以及UV254進(jìn)行檢測(cè),同時(shí)對(duì)MOR和BR進(jìn)出水GC-MS、紫外-可見(jiàn)吸收光譜和三維熒光光譜進(jìn)行分析,以評(píng)價(jià)系統(tǒng)污染物處理性能和典型難降解污染物去除.

1.4 分析項(xiàng)目及測(cè)定方法

MOR和BR進(jìn)出水COD、BOD5、氨氮濃度均采用國(guó)標(biāo)方法測(cè)定[18].UV254值和紫外-可見(jiàn)吸收光譜采用紫外-可見(jiàn)分光光度計(jì)(上海天美,U-3900)測(cè)定. MOR和BR進(jìn)出水使用環(huán)己烷在酸性和堿性條件下分別萃取3次后,將酸萃相和堿萃相混合,濃縮吹干后,以丙酮為溶劑,采用氣相色譜-質(zhì)譜聯(lián)用儀(GC-MS,Thermo DSQ II,美國(guó))進(jìn)行GC-MS分析[19].采用熒光分光光度計(jì)(HORIBA FluoroMax-4,日本)對(duì)MOR和BR進(jìn)出水進(jìn)行三維熒光光譜分析[20].

2 結(jié)果與討論

2.1 COD去除性能

由圖2可見(jiàn),耦合處理過(guò)程中,MOR進(jìn)水平均COD濃度為275.0mg/L,出水COD平均濃度為201.5mg/L,COD平均去除率和去除負(fù)荷分別為26.4%和1.46kg/(m3·d).對(duì)MOR處理中廢水BOD5/COD (B/C)值進(jìn)行監(jiān)測(cè),結(jié)果如圖3所示.可以看到,處理60min后,廢水B/C值可由0.038提高至0.30,可生化性大大改善.

同時(shí),與相同條件下運(yùn)行初期MOR空床微氣泡臭氧化處理、空氣微氣泡活性炭床層吸附處理和傳統(tǒng)氣泡催化臭氧化處理過(guò)程進(jìn)行比較.結(jié)果表明,MOR空氣微氣泡活性炭床層吸附處理過(guò)程COD平均去除率僅2.7%,可見(jiàn)活性炭床層對(duì)污染物的吸附去除效果極其有限;MOR空床微氣泡臭氧化處理過(guò)程COD平均去除率12.3%,可見(jiàn)顆?；钚蕴看呋瘜?duì)提高微氣泡臭氧化去除COD作用明顯;MOR傳統(tǒng)氣泡催化臭氧化處理運(yùn)行過(guò)程COD平均去除率為9.6%,可見(jiàn)微氣泡技術(shù)能顯著提高催化臭氧化COD去除性能.微氣泡催化臭氧化可通過(guò)臭氧微氣泡類催化效應(yīng)[21-22]和催化劑催化的協(xié)同作用強(qiáng)化×OH氧化反應(yīng),可能是其有效去除COD并提高可生化性的原因.

如圖2所示,BR運(yùn)行20d后,隨著生物膜生長(zhǎng)成熟,COD去除性能趨于穩(wěn)定,此后其出水平均COD濃度為103.5mg/L,COD平均去除率和去除負(fù)荷分別為45.4%和0.26kg/(m3·d).可見(jiàn),微氣泡臭氧催化氧化處理降解廢水中難降解有機(jī)污染物,提高廢水可生化性,大大改善BR生化處理COD去除性能.耦合處理COD總?cè)コ?2.4%,顯著優(yōu)于直接生化處理(COD去除率僅6.4%).

同時(shí),MOR出口氣液混合物中存在臭氧殘留,氣體臭氧平均濃度為2.3mg/L,溶解臭氧平均濃度為2.5mg/L;而B(niǎo)R出口氣體和出水中均未檢測(cè)到殘留臭氧.可見(jiàn),盡管MOR出口混合物中存在臭氧殘留,但不會(huì)對(duì)BR中COD去除性能造成明顯影響;而所投加臭氧均消耗于處理系統(tǒng)中,無(wú)需進(jìn)行臭氧尾氣處理.

2.2 氨氮和總氮(TN)去除

由圖4可見(jiàn),MOR進(jìn)水氨氮平均濃度為4.3mg/L,出水氨氮平均濃度為8.9mg/L.可見(jiàn),經(jīng)過(guò)微氣泡臭氧催化氧化處理后,出水氨氮濃度顯著高于進(jìn)水氨氮濃度.MOR進(jìn)出水氨氮濃度變化表明,廢水中存在大分子含氮有機(jī)污染物,其被微氣泡臭氧催化氧化降解后,釋放出氨氮,使得出水氨氮濃度增加.盡管微氣泡臭氧催化氧化處理后氨氮濃度升高,但后續(xù)生化處理可實(shí)現(xiàn)對(duì)氨氮的有效去除.BR運(yùn)行穩(wěn)定后,進(jìn)出水平均氨氮濃度分別為8.9,3.6mg/L,平均去除率為52.2%.

耦合處理過(guò)程中,MOR和BR進(jìn)出水氨氮濃度如圖5所示.可以看到,MOR進(jìn)水平均TN濃度分為13.3mg/L,微氣泡臭氧催化氧化處理對(duì)TN沒(méi)有去除作用,出水平均TN濃度為13.3mg/L,與進(jìn)水TN濃度基本一致.生化處理后出水TN濃度略有降低,出水平均TN濃度分別為10.3mg/L.生化處理中TN去除主要依靠硝化反硝化過(guò)程,考慮到BR中高DO濃度不利于形成反硝化環(huán)境,因此TN去除有限,細(xì)胞同化作用可能是TN去除的主要原因.

2.3 UV254去除

254nm波長(zhǎng)下的吸收值UV254可以用來(lái)指示廢水中難降解芳香族有機(jī)污染物[23],其通常被認(rèn)為與芳香族有分子中的不飽和C=C鍵和芳香環(huán)有關(guān)[24-25].耦合處理過(guò)程中,MOR和BR進(jìn)出水UV254值變化如圖6所示.可以看到,經(jīng)過(guò)微氣泡臭氧催化氧化處理后,MOR出水UV254值明顯降低,進(jìn)出水平均UV254值分別為0.90和0.41, UV254值平均去除率為53.7%.此結(jié)果表明,微氣泡臭氧催化氧化均能夠破壞廢水中芳香族污染物不飽和鍵和芳香環(huán)結(jié)構(gòu),并產(chǎn)生小分子有機(jī)物.經(jīng)過(guò)生化處理后,BR出水UV254值進(jìn)一步降低,進(jìn)出水平均UV254值分別為0.41和0.28.可見(jiàn), 微氣泡臭氧催化氧化處理后,生化處理能夠進(jìn)一步去除部分剩余芳香族污染物,但去除效率相對(duì)較低.耦合處理對(duì)UV254的總?cè)コ士梢赃_(dá)到68.9%.

2.4 GC-MS分析

對(duì)煤化工廢水生化出水(MOR進(jìn)水)進(jìn)行GC-MS檢測(cè)分析,廢水GC圖譜如圖7所示.可以看到,保留時(shí)間為17~24min的物質(zhì)峰面積最大,是廢水中的主要有機(jī)污染物.經(jīng)MS分析,此保留時(shí)間范圍內(nèi)的物質(zhì)均為含氮雜環(huán)芳烴類有機(jī)物,如表2所示.此外,保留時(shí)間24min以上的物質(zhì)多為長(zhǎng)鏈烷烴類物質(zhì).含氮雜環(huán)芳烴類有機(jī)物和長(zhǎng)鏈烷烴類物質(zhì)均為煤化工廢水典型有機(jī)污染物,煤化工廢水生化出水中殘留大量難降解含氮雜環(huán)芳烴類污染物,是其可生化性極差的主要原因[26].

同時(shí),對(duì)MOR出水和BR出水進(jìn)行GC-MS檢測(cè)分析,其GC圖譜如圖8所示.可以看到,經(jīng)過(guò)微氣泡臭氧催化氧化處理后,MOR出水中保留時(shí)間為17~24min之間的物質(zhì)峰基本消失,表明微氣泡臭氧催化氧化能夠高效降解含氮雜環(huán)芳烴類有機(jī)物,使得廢水可生化性提高,UV254值降低,且釋放出氨氮.同時(shí),MOR出水仍存在少量保留時(shí)間24min以上的長(zhǎng)鏈烷烴類物質(zhì).經(jīng)過(guò)生化處理后,BR出水中保留時(shí)間24min以上的物質(zhì)峰亦明顯下降,表明長(zhǎng)鏈烷烴類物質(zhì)在生化處理中亦得到有效去除.

表2 煤化工廢水生化出水中含氮雜環(huán)芳烴類污染物

2.5 紫外-可見(jiàn)吸收光譜分析

對(duì)MOR進(jìn)水、MOR出水和BR出水進(jìn)行紫外-可見(jiàn)吸收檢測(cè)分析,其紫外-可見(jiàn)吸收光譜如圖9所示.可以看到,MOR進(jìn)水在200~370nm波長(zhǎng)范圍內(nèi)有較強(qiáng)的紫外吸收帶,其與存在大分子含氮雜環(huán)芳烴類有機(jī)物有關(guān)[20].MOR出水中250~370nm波長(zhǎng)范圍內(nèi)紫外吸收強(qiáng)度顯著下降,同樣證實(shí)微氣泡臭氧催化氧化能夠有效破壞含氮雜環(huán)芳烴類有機(jī)物.BR出水中250~370nm波長(zhǎng)范圍內(nèi)紫外吸收強(qiáng)度進(jìn)一步小幅下降.同時(shí),MOR和BR出水中200~250nm波長(zhǎng)范圍內(nèi)紫外吸收強(qiáng)度仍然較高,其與存在小分子單環(huán)芳香族化合物有關(guān)[27].

紫外-可見(jiàn)吸收光譜中,250nm和365nm吸光度的比值與分子大小存在負(fù)相關(guān)關(guān)系,其比值越小,表明大分子有機(jī)物所占比例越高[28].MOR進(jìn)水、MOR出水和BR出水250nm和365nm吸光度的比值分別為6.55、9.54和9.03.可見(jiàn),微氣泡臭氧催化氧化降解大分子有機(jī)物生成小分子有機(jī)物,使得大分子有機(jī)物所占比例明顯下降;而生化處理更易去除小分子有機(jī)物,使得大分子有機(jī)物比例又有所升高.

2.6 三維熒光光譜(EEM)分析

對(duì)MOR進(jìn)水、MOR出水和BR出水進(jìn)行三維熒光檢測(cè)分析,其三維熒光光譜如圖10所示.可以看到,MOR進(jìn)水三維熒光光譜中存在1個(gè)強(qiáng)熒光峰(峰1)和2個(gè)弱熒光峰(峰2和峰3).峰1(X/m=240/350~380nm)與類色氨酸(芳香族蛋白質(zhì)類,即含氮雜環(huán)芳烴類)物質(zhì)有關(guān),屬于生物難降解物質(zhì);峰2(X/m=330/410nm)與類腐殖酸物質(zhì)有關(guān);峰3(X/m=275/340nm)與類溶解性微生物產(chǎn)物有關(guān),屬于生物可降解物質(zhì)[6,20].其中,峰3/峰1的熒光強(qiáng)度比值為0.39,表明廢水可生化性差[6].

經(jīng)過(guò)微氣泡臭氧催化氧化處理后,MOR出水三維熒光光譜中峰1和峰2熒光強(qiáng)度明顯減弱,表明進(jìn)水中含氮雜環(huán)芳烴類和類腐殖酸物質(zhì)被降解去除;同時(shí),峰3的相對(duì)熒光強(qiáng)度升高,峰3/峰1的熒光強(qiáng)度比值提高至1.18,表明MOR出水可生化性顯著提高.生化處理后,BR出水三維熒光光譜中峰1和峰3熒光強(qiáng)度進(jìn)一步減弱,表明生化處理可進(jìn)一步降解剩余芳香族污染物,并有效去除可生物降解污染物.

3 結(jié)論

3.1 采用MOR-BR耦合工藝深度處理煤化工廢水生化出水,MOR中COD平均去除率和去除負(fù)荷分別為26.4%和1.46kg/(m3·d),并將廢水B/C值由0.038提高至0.30,從而改善后續(xù)BR中COD去除性能,得COD總?cè)コ蔬_(dá)到62.4%,顯著優(yōu)于直接生化處理. MOR降解含氮雜環(huán)芳烴后釋放氨氮,其在BR中被有效去除.此外,MOR-BR對(duì)UV254的總?cè)コ士蛇_(dá)68.9%.

3.2 GC-MS、紫外-可見(jiàn)吸收光譜和三維熒光光譜分析表明,含氮雜環(huán)芳烴是煤化工廢水生化出水中主要難降解污染物.微氣泡臭氧催化氧化可有效降解去除含氮雜環(huán)芳烴,生成小分子有機(jī)物,提高廢水可生化性.

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Removal of refractory nitrogen-containing heterocyclic aromatics by combination treatment of microbubble catalytic ozonation and biological process.

ZHOU Hong-zheng, LIU Ping, ZHANG Jing, LIU Chun*, CHEN Xiao-xuan, ZHANG Lei

(Pollution Prevention Biotechnology Laboratory of Hebei Province, School of Environmental Science and Engineering, Hebei University of Science and Technology, Shijiazhuang 050018, China)., 2017,37(8)：2978~2985

A combination of microbubble catalytic ozonation and biological process was used for advanced treatment of bio-treated coal chemical wastewater (BCCW). Contaminant removal performance in the combination system was investigated. Degradation of nitrogen-containing heterocyclic aromatics and biodegradability variation of BCCW were discussed during combination treatment. The average COD removal efficiency of 26.4% and the average COD loading rate removed of 1.46kg/(m3·d) could be achieved in microbubble catalytic ozonation treatment. Moreover, the BOD5/COD value of BCCW increased from 0.038 to 0.30 after microbubble catalytic ozonation treatment, which could improve COD removal performance in the following biological process. The total COD removal efficiency of the combination system reached to 62.4%, which was much better than that of biological treatment alone. The nitrogen-containing heterocyclic aromatics in BCCW could be degraded efficiently by microbubble catalytic ozonation treatment, releasing ammonia nitrogen which could be removed further in the following biological treatment. In addition, the total UV254removal efficiency in the combination system was 68.9%. The GC-MS, UV-Vis spectra and fluorescence excitation-emission matrix (EEM) spectra of BCCW were analyzed during combination treatment. The nitrogen-containing heterocyclic aromatics were identified to be the main refractory contaminants in BCCW, and microbubble catalytic ozonation was effective for degradation of nitrogen-containing heterocyclic aromatics, to generate low-molecular-weight organics and improve BCCW biodegradability.

microbubbles；catalytic ozonation；biological treatment；nitrogen-containing heterocyclic aromatics；coal chemical wastewater

X703

A

1000-6923(2017)08-2978-08

周洪政(1988-),男,河北衡水人,河北科技大學(xué)碩士研究生,主要從事廢水處理技術(shù)研究工作.

2017-01-22

河北省自然科學(xué)基金項(xiàng)目(E2015208140)

* 責(zé)任作者, 教授, liuchun@hebust.edu.cn