曾淦寧,張茹霞,高露露,沈江南,屠美玲,阮慧敏,張 鵬
(1.浙江工業(yè)大學(xué)海洋學(xué)院,杭州 310014;2.浙江工業(yè)大學(xué)海洋研究院,杭州 310014;3.浙江工業(yè)大學(xué)化學(xué)工程學(xué)院,杭州 310014;4.浙江省海洋水產(chǎn)養(yǎng)殖研究所,溫州 325005)
浸沒式膜生物反應(yīng)器協(xié)同活性炭處理海產(chǎn)養(yǎng)殖廢水效果
曾淦寧1,2,張茹霞2,3,高露露1,沈江南1,屠美玲3,阮慧敏1,張 鵬4
(1.浙江工業(yè)大學(xué)海洋學(xué)院,杭州 310014;2.浙江工業(yè)大學(xué)海洋研究院,杭州 310014;3.浙江工業(yè)大學(xué)化學(xué)工程學(xué)院,杭州 310014;4.浙江省海洋水產(chǎn)養(yǎng)殖研究所,溫州 325005)
該文結(jié)合海產(chǎn)養(yǎng)殖廢水的鹽度效應(yīng)特點,開展了浸沒式膜生物反應(yīng)器(membrane bioreactor,MBR)協(xié)同粉末活性炭(powder activated carbon,PAC)處理含鹽廢水的試驗??疾炝送都覲AC對于MBR污染物去除性能及膜污染的影響;鹽度變化過程中(0~35 g/L)MBR對化學(xué)需氧量(chemical oxygen demand,COD)、氨氮(ammonia nitrogen,NH+4-N)、亞硝酸鹽氮(nitrite nitrogen,NO2-N)處理效果;以及含鹽廢水長期作用下微生物性能、膜通量、絮體粒徑的變化情況。重點分析0~5 g/L的鹽度變化,本體溶液中的溶解性有機(jī)物(soluble microbile products,SMP)和污泥絮體中胞外聚合物(extracellular polymeric substances,EPS)組成及含量的變化情況。結(jié)果表明:MBR-PAC對COD的去除效率比MBR高7.3%,對NH+4-N、NO2-N去除的穩(wěn)定性優(yōu)于MBR;兩工藝條件下膜通量隨鹽度變化呈現(xiàn)類似的趨勢,即敏感期衰減,穩(wěn)定期得到一定程度的恢復(fù)。養(yǎng)殖廢水長期作用下,MBR-PAC膜通量是MBR的1.5倍,MBR-PAC的污泥粒徑相對于MBR增加了52 μm。鹽度變化過程中,PAC由于其吸附性能及絮凝能力,能吸附本體溶液中的溶解性微生物代謝產(chǎn)物,相對于MBR,蛋白質(zhì)的含量減少了34.0%。MBR-PAC適用于海產(chǎn)養(yǎng)殖廢水的處理。
膜生物反應(yīng)器;活性污泥;鹽度沖擊;粉末活性炭;海產(chǎn)養(yǎng)殖廢水
曾淦寧,張茹霞,高露露,沈江南,屠美玲,阮慧敏,張 鵬.浸沒式膜生物反應(yīng)器協(xié)同活性炭處理海產(chǎn)養(yǎng)殖廢水效果[J].農(nóng)業(yè)工程學(xué)報,2016,32(6):248-253.doi:10.11975/j.issn.1002-6819.2016.06.034 http://www.tcsae.org
Zeng Ganning,Zhang Ruxia,Gao Lulu,Shen Jiangnan,Tu Meiling,Ruan Huimin,Zhang Peng.Effect of coordinated treatment of membrane bioreactor and powder activated carbon on marine aquaculture wastewater[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2016,32(6):248-253.(in Chinese with English abstract)doi:10.11975/j.issn. 1002-6819.2016.06.034 http://www.tcsae.org
膜生物反應(yīng)器處理含鹽廢水面臨的技術(shù)難題主要來自于其較高的鹽度[1],一方面抑制微生物的生長、導(dǎo)致污泥性能變差;另一方面,也影響膜生物反應(yīng)器對污染物的去除能力,進(jìn)而加快膜生物反應(yīng)器的污染速率[2-3]。研究表明,當(dāng)鹽濃度增加到2 g/L時,反應(yīng)器內(nèi)的溶解性有機(jī)物中蛋白質(zhì)濃度增加幅度較大,相對于鹽濃度未改變時含量增加了72%,多糖增加了18%[4];在較高的鹽度下,微生物為了維持自身的生物活性,會釋放更多的胞外聚合物維持自身生命。溶解性有機(jī)物和胞外聚合物是造成膜污染的主要因素[5]。
海水本身的的鹽度效應(yīng),養(yǎng)殖廢水污染成分如可溶有機(jī)物、無機(jī)物含量高等污染結(jié)構(gòu)的特殊性能,加大了其處理難度,導(dǎo)致膜污染加重,縮短了其使用周期,進(jìn)而導(dǎo)致該項技術(shù)一直未得以有效推廣。如何有效的將MBR廣泛的運(yùn)用于該領(lǐng)域,減緩膜污染,延長膜的使用周期已成為本領(lǐng)域的研究前沿。改善膜生物反應(yīng)器污泥混合液可濾性是其中最為有效的一種方案[6],尤其是利用活性炭穩(wěn)定膜通量已成為非常有前景的膜污染控制策略之一[7]?;钚蕴恳蚓咂溆休^大的比表面積,其內(nèi)部孔隙結(jié)構(gòu)比較發(fā)達(dá),適合一些微生物在其表面及其內(nèi)部生長繁殖,活性炭可以吸附有機(jī)物,為有機(jī)物提供能量,供微生物細(xì)菌生長,依靠微生物的降解作用除去可溶有機(jī)物[8]。在MBR中投加粉末活性炭可以有效提高臨界通量?;钚蕴坎粌H能改善污泥的混合液特性,還可以在膜表面形成一層具有動態(tài)過濾性能的粉末活性炭層,能夠定期清洗沉積在膜表面的污染物,防止水中的污染物沉積到膜的表面[9]。此外,粉末活性炭(powder activated carbon,PAC)的投加能夠增加活性污泥的平均粒徑,吸附溶液中溶解性有機(jī)物(soluble microbileproducts,SMP)和絮凝作用降低污泥絮體中胞外聚合物(extracellular polymeric substances,EPS)的含量,由于活性炭多孔結(jié)構(gòu),沉積在膜表面的濾餅層結(jié)構(gòu)疏松,減緩了膜通量的衰減,進(jìn)而減緩膜污染速率[10]。
本文著重考察了添加活性炭前后MBR的處理效果,著重考察了粉末活性炭的投加對膜污染的改善狀況。通過分析污染物化學(xué)需氧量(chemical oxygen demand,COD)、氨氮(ammonia nitrogen,NH+4-N)的去除情況,溶解性有機(jī)物的組成及含量分析,絮體結(jié)構(gòu)中的胞外聚合物含量及組成分析,考察PAC的作用,對膜通量的改善情況,以期為MBR-PAC處理海產(chǎn)養(yǎng)殖廢水技術(shù)提供更對的理論依據(jù)。
1.1 試驗裝置與運(yùn)行條件
污泥取自杭州七格污水處理廠二沉池,實驗室對其進(jìn)行培養(yǎng),直至COD、NH+4-N的去除率穩(wěn)定。
試驗于2015年3月-6月在浙江工業(yè)大學(xué)實驗室展開。采用浸沒式膜生物反應(yīng)器,生物反應(yīng)器內(nèi)置有聚偏氟乙烯(poly(vinylidene fluoride),PVDF)中空纖維超濾膜,膜孔徑為0.03 μm,膜絲內(nèi)徑為0.7 mm,外徑為1.3 mm;生物反應(yīng)器內(nèi)中添加有1 g/L粉末活性炭(粒度200目左右),比表面積為1 500 m2/g;污泥濃度(mixed liquor suspended solids,MLSS)3~4 g/L左右;在運(yùn)行期間進(jìn)行連續(xù)曝氣,使反應(yīng)器內(nèi)的活性污泥混合均勻。
圖1為MBR工藝流程圖,模擬的海產(chǎn)養(yǎng)殖廢水由泵打入反應(yīng)器A和B中,處理完成的污水在隔膜泵抽吸作用下經(jīng)中空纖維膜過濾后打入儲水池中。試驗中的膜組件采用間歇方式運(yùn)行,即抽吸時間10 min,停3 min,進(jìn)行不斷循環(huán),由自己購買的時間繼電器進(jìn)行控制。曝氣泵在膜組件正下方連續(xù)進(jìn)行曝氣,一方面,為微生物細(xì)菌提供氧氣;另一方面,使活性污泥混合均勻,減輕污泥在膜表面的積累。
圖1 工藝流程圖Fig.1 Process flow chart of MBR
反應(yīng)器運(yùn)行工況為:1)2套裝置(MBR-PAC,MBR)在相同操作條件下進(jìn)行試驗;2)調(diào)整進(jìn)水鹽度為0、5、15、25、35 g/L每個鹽度變量維持在15 d左右即MBR出水穩(wěn)定;3)進(jìn)水水質(zhì)為模擬海產(chǎn)養(yǎng)殖廢水,其中濃度20mg/L、 COD濃度100 mg/L左右。
1.2 分析和測定方法
SMP采用離心分離法提取;EPS采用熱提取法提??;多糖(polysaccharide)和蛋白質(zhì)(protein)含量測定采用蒽酮比色法和考馬斯亮藍(lán)法[11]。污泥相對疏水性(related hydrophobic,RH):以烴類為指標(biāo),以處理前后活性污泥濃度進(jìn)行測定[12]。COD、NH+4-N、NO2-N均采用海洋監(jiān)測規(guī)范GB17378.4-2007進(jìn)行測定。
2.1 污染物去除特性
圖2顯示了2套MBR運(yùn)行過程中污染物去除率情況。2套系統(tǒng)對COD、去除率都達(dá)75%、95%以上。在鹽度沖擊過程中,MBR-PAC系統(tǒng)對COD去除效率比MBR的高7.3%左右(圖2b);對的去除比MBR要好,增加了0.7%;對NO2-N的影響較小,恢復(fù)周期短,恢復(fù)之后水質(zhì)穩(wěn)定。MBR系統(tǒng)的NO2-N出水波動大,水質(zhì)穩(wěn)定性差。(圖2b,2c)。2套系統(tǒng)對的去除效果均要明顯好于對COD的去除效果,這表明當(dāng)MBR受含鹽廢水沖擊時,鹽度對硝化菌的影響要小于對有機(jī)物降解菌的影響。
圖2 MBR-PAC及MBR運(yùn)行情況Fig.2 Performance of MBR-PAC and MBR
2.2 污泥性狀變化及微生物活性分析
鹽度沖擊下污泥混合液特性變差,無論是否在MBR中添加PAC,污泥體積指數(shù)(sludge volume index,SVI)隨鹽度所占比例的增加而逐漸降低,但是SVI的值仍維持在50~150左右,說明污泥仍表現(xiàn)出良好的絮凝性和沉降性。MBR的SVI值相對較低,說明污泥顆粒細(xì)小緊密,微生物數(shù)量少,污泥活性較低(圖3)。在鹽度變化過程中,活性污泥中菌膠團(tuán)數(shù)量都有一定程度的減少。MBR-PAC中菌膠團(tuán)較為不開放,彼此相連比較明顯,在緊密較強(qiáng)的菌膠團(tuán)有時形成尺寸較大、結(jié)實的顆粒狀絮體;相較而言,MBR中污泥顆粒粒徑相對較小,活性污泥中菌膠團(tuán)是不規(guī)則的;菌膠團(tuán)緊密度較弱,缺乏中心體。這表明,粉末活性炭的添加造成活性污泥顆粒性能的變化,形成更加穩(wěn)定的菌膠團(tuán)結(jié)構(gòu)和粒徑較大的污泥,因而有利于減緩膜污染。
圖3 MBR-PAC及MBR微生物活性Fig.3 Microbial activity of MBR-PAC and MBR
2.3 鹽度變化(0~5 g/L)對溶解性有機(jī)物(SMP)和胞外聚合物(EPS)的影響
選擇鹽度在0~5 g/L的變化過程,細(xì)化考察SMPpr(蛋白質(zhì))及SMPpo(多糖)在此過程中的含量變化(圖4)。在高鹽度沖擊下,SMPpo更容易被釋放至本體溶液中。MBR系統(tǒng)中,敏感期SMPpo濃度增加明顯,SMPpr濃度增加緩慢。高鹽會加速微生物的內(nèi)源性呼吸作用,高鹽作用下,會釋放更多的SMP,同時會強(qiáng)化EPS的水解速率,使更對的EPS轉(zhuǎn)化成本體溶液中的SMP[13]。與處于敏感期的MBR相比,MBR-PAC中SMPpo及SMPpr的濃度均有所降低,對SMPpr的去除能力高于SMPpo,去除率分別提高了34.0%、11.5%。這是由于SMPpr具有較小的相對分子量,在本體溶液中更易于被粉末活性炭吸附去除[14]。
圖4 鹽度變化過程中溶解性有機(jī)物中的多糖、蛋白質(zhì)含量Fig.4 Content of polysaccharide(protein)in dissolved organic matterin process of salinity Changes(Salinity:S=0~5 g/L)
EPS濃度及組成直接決定了絮體或細(xì)胞表面物化特性,對膜污染起到了至關(guān)重要的作用。EPS粘附在膜表面,會加速膜的污染速率,導(dǎo)致膜通量下降;此外,EPS的存在使得本體溶液向膜面的對流傳遞作用受限,水力剪切力作用對污染層的脫除能力減弱,使污泥濾餅層阻力增大[15]。MBR系統(tǒng)中,EPSpo(多糖)濃度、EPSpr(蛋白質(zhì))濃度均呈現(xiàn)出敏感期下降而恢復(fù)期濃度增加的趨勢,前者更為顯著;MBR-PAC系統(tǒng)中,EPSpo呈現(xiàn)下降的趨勢,EPSpr(蛋白質(zhì))在敏感期呈現(xiàn)增加的趨勢,其中EPSpr比正常期增加了14.7%,由于PAC的投加加強(qiáng)了對SMPpr的去除情況,PAC的添加加強(qiáng)了污泥的絮體性能,使絮體中EPSpr含量增加;同時,以粉末活性炭為骨架形成的污泥絮體,可以吸附較小分子的有機(jī)物,因此增加了對EPSpo(多糖)的去除能力,如圖5所示。
圖5 鹽度變化中胞外聚合物中多糖、蛋白質(zhì)含量Fig.5 Contentofpolysaccharide(protein)inExtracellularpolymeric substanceinprocessofsalinityChanges(Salinity:S=0~5g/L)
2.4 鹽度變化(0~5 g/L)對污泥絮體疏水性的影響
選擇鹽度在0~5 g/L的變化過程,細(xì)化考察污泥絮體的疏水性能(圖6)。相比MBR-PAC而言,MBR反應(yīng)器中的污泥對鹽度波動更加敏感。對于MBR而言,RH由正常期的93.4%下降至敏感期的63.0%,恢復(fù)期RH增加明顯。對于MBR-PAC,由于粉末活性炭的加入使得MBR-PAC絮體RH相對于MBR增加了20%左右。這表明,在鹽度變化過程中,活性炭的添加增加了活性污泥的相對疏水性,與Shin[16]研究結(jié)果一致。
圖6 鹽度變化中污泥疏水性及其與多糖/蛋白質(zhì)之間的關(guān)系Fig.6 Relative hydrophobicity of slugeand the relative between relative hydrophobicity and polysaccharide/protein in the process of salinity Changes(Salinity:S=0~5 g/L)
絮體疏水性的增加一定程度上增加微生物的絮凝能力,絮體粒徑增加,最終會增加混合液的可濾性能。一般來講,蛋白質(zhì)相對于多糖具有更強(qiáng)的疏水性,多糖與蛋白質(zhì)的比值越小,污泥疏水性越強(qiáng)。MBR-PAC系統(tǒng)中污泥的相對疏水性整體優(yōu)于MBR系統(tǒng)(圖6a),這與MBR-PAC系統(tǒng)中多糖、蛋白質(zhì)含量相對較低的結(jié)果是一致的,與多糖與蛋白質(zhì)的比值越小結(jié)果是一致。與溶解性有機(jī)物、胞外聚合物中二者的比例也是吻合的(圖4,圖5)。絮體疏水性的增加降低了絮體與親水性膜的親和作用能力,一定程度上起到減緩膜污染的作用[17]。因此,在鹽度變化過程中,添加活性炭能很好地改善膜的污染性能。
2.5 鹽度變化對污泥粒徑的影響
分別對原泥和35 g/L鹽度作用75d后的活性污泥進(jìn)行取樣分析。結(jié)果顯示,原泥平均粒徑210 μm,2種膜組件運(yùn)行下的活性污泥平均粒徑分別為709 μm(MBR-PAC)、657 μm(MBR),添加活性炭的污泥平均粒徑比未投加的粒徑增大52 μm,如圖7所示。在PAC的投加作用下,由于PAC的絮凝作用,使活性污泥中的小顆粒物質(zhì)聚集起來,以PAC為核心會形成更大的絮體粒徑,增加了絮體尺寸,在相同的曝氣作用下,會減少單位體積內(nèi)大顆粒污泥粒徑之間碰撞的可能,弱化了小顆粒的形成,降低混合液粘度。這是因為污泥粒徑越大,在曝氣強(qiáng)度不變的作用下,膜表面錯流提升作用得到加強(qiáng),大粒徑越不易在膜表面沉積,弱化了濾餅層的形成;由Carmen-Kozeny公式可知,粒徑越大,產(chǎn)生的污泥濾餅層比阻就越小,過濾過程中產(chǎn)生的阻力也就越小[18]。此外,MBR-PAC系統(tǒng)中因其混合液粘度低,污泥粒徑較大,改善其水力學(xué)性能,從而提高膜本身的滲透性能[19-20]。
圖7 活性污泥粒徑分析(原樣、MBR-PAC、MBR)Fig.7 Particle size of activated Sludge(original sludge、MBR-PAC、MBR)
2.6 PAC對膜污染的影響
圖8顯示了整個鹽度變化過程中,2套反應(yīng)器膜通量的變化情況。相對于MBR-PAC而言,MBR的恢復(fù)期較長,且膜通量穩(wěn)定性差。MBR-PAC膜通量由最初的340 L/m2.h降到147 L/m2.h左右,而MBR降到100 L/m2.h左右。表明鹽度沖擊惡化了污泥混合液可濾性,造成膜污染加劇。表明投加粉末活性炭顯著提高了污泥混合液的可濾性,膜表面形成的污泥濾餅層結(jié)構(gòu)相對較疏松;同時由于活性炭的對親水性小分子有機(jī)物有更大的吸附性能,減少了污染物在膜表面的積累,有效延緩了膜污染。
圖8 MBR-PAC及MBR的膜通量Fig.8 Flux of MBR-PAC and MBR
在新膜的膜表面,可以觀察到多孔(圖9)。鹽度沖擊結(jié)束后,MBR-PAC膜的表面的濾餅層相對疏松,膜表面未被污染物完全的覆蓋,清洗過程很容易;而MBR中膜表面被污染物均勻的覆蓋,堵塞了膜的孔結(jié)構(gòu),清洗過程相對較難。說明MBR中的膜污染較嚴(yán)重,添加活性炭之后的膜污染得到相對改善。
圖9 膜的外表面的掃描電鏡圖Fig.9 SEM of membrane
1)鹽度沖擊降低了MBR工藝對傳統(tǒng)污染物的去除能力,添加PAC的MBR有助于海產(chǎn)養(yǎng)殖廢水的處理。運(yùn)行結(jié)果顯示MBR-PAC系統(tǒng)對COD、的去除率分別增加了7.3%、0.7%,出水中的NO2-N平均小于0.05 mg/L,出水更加穩(wěn)定,鹽度沖擊下恢復(fù)周期短。
2)鹽度變化過程中,對于MBR,SMP在高鹽度沖擊后在本體溶液增加明顯,尤其是SMPpo濃度;MBR-PAC系統(tǒng),多糖和蛋白質(zhì)濃度都有不同程度的降低,相對于MBR來說,SMPpr的去除率增加了34.0%;SMPpo去除率增加了11.5%。對于MBR-PAC,EPSpr濃度在敏感期呈現(xiàn)增加趨勢,比正常期增加了14.7%,絮體中EPS含量增加,使污泥顆粒尺寸增大,污泥疏水性增強(qiáng),更有利于減緩膜污染。
3)在鹽度變化過程中,活性炭的添加增加了活性污泥的相對疏水性?;钚蕴康奶砑釉黾恿嘶钚晕勰嗟牧6?,相對于未投加的增加了52 μm,很大程度地改善了膜的抗污染性能。
4)MBR在高鹽沖擊下污泥混合液特性變差,污泥體積指數(shù)逐漸減小,但是SVI的值在50~150左右,說明污泥仍表現(xiàn)出良好的絮凝性和沉降性。在含鹽廢水的長期作用下,PAC投加減緩了膜通量的衰減,MBR-PAC膜通量(147 L/m2h)高于MBR(100 L/m2h)。
[1]Johir M A H,Vigneswaran S,Kandasamy J,et al.Effect of salt concentration on membrane bioreactor(MBR)performances: detailed organic characterization[J].Desalination,2013,322:13-20.
[2]Pendashteh A R,LuqmanChuah A,Fakhru’l-Razi A.Evaluation ofmembrane bioreactorforhypersaline oily wastewater treatment[J].Process Safe and Environmental protection,2012, 90:45-55.
[3]Jang D,Hwang Y,Shin H,et al.Effects of salinity on the characteristics of biomass and membrane fouling in membrane bioreactors[J].Bioresource Technology,2013,141:50-56.
[4]Reid E,Liu X,Judd S J.Effect of high salinity on activated sludge characteristicsand membrane permeability in an immersed membrane bioreactor[J].Journal of Membrane Science, 2006,283:164-171.
[5]De Temmerman L,Maere T,Temmink H,et al.Salt stress in a membrane bioreactor:Dynamics of sludge properties,membrane fouling and remediation through powdered activated carbon dosing[J].Water research,2014,63,112-124.
[6]高元,李紹峰,陶虎春.MBR污泥混合液特性變化及膜污染關(guān)系研究[J].環(huán)境工程學(xué)報,2011,5(1):28-32. Gao Yuan,Li ShaoFeng,Tao HuChun.Research on membrane fouling and the changes of sludge mixed liquor characteristics in MBR[J].Journal of Environmental Engineering,2011,5(1):28-32.(in Chinese with English abstract)
[7]Jing J,Qiu J,Wai N,et al.Enhancement of filterability in MBR achieved by improvement of supernatant and floc characteristics via filter aids addition[J].Water research,2008,42(14):3611-3622.
[8]Fenu A,Guglielmi G,Jimenez J,et al.Activatedsludge model (ASM)based modelling ofmembrane bioreactor;(MBR) processes:a critical review with special regard to MBR specificities[J].Water research,2010,44:4272-4294.
[9]Iversen V,Mehrez R,Horng R Y,et al.Fouling mitigation through flocculants and adsorbents addition in membrane bioreactors:comparing lab and pilot studies[J].Journalof Membrane Science,2009,345:21-30.
[10]Jamal Khan S,Visvanathan C,Jegatheesan V.Effect of powdered activated carbon (PAC)and cationic polymer on biofouling mitigation in hybrid MBRs[J].Bioresource Technology,2012, 113:165-168.
[11]Lin H,Zhang M,Wang F,et al.A critical review of extracellular polymeric substances (EPSs) in membrane bioreactors: characteristics,roles in membrane fouling and control strategies [J].Journal of Membrane Science,2014,460:110-125.
[12]Wilen B M,Jin B,Lant P.The influence of key chemical constituents in activated sludge on surface and flocculating properties[J].Water research,2003,37(9):2127-2139.
[13]Reid E,Liu X,Judd S J.Effect of high salinity on activated sludge characteristicsand membrane permeability in an immersed membrane bioreactor[J].Journal of Membrane Science, 2006,283,164-171.
[14]Pan J R,Su Y,Huang C.Characteristics of soluble microbial products in membrane bioreactor and its effect on membrane fouling[J].Desalination,2010,250:778-780.
[15]Sheng G P,Yu H Q,Li X Y.Extracellular polymeric substances (EPS)of microbial aggregates in biological wastewater treatment systems:a review[J].Biotechnology advances,2010,28:882-894.
[16]Shin H S,Kang S T.Characteristics and fates of soluble microbial products in ceramic membrane bioreactor at various sludge retention time[J].Water Research,2003,37(1):121-127.
[17]Damayanti A,Ujang Z,Salim M R.The influenced of PAC, zeolite,and Moringaoleifera as biofouling reducer(BFR)on hybrid membrane bioreactor of palm oil mill effluent(POME)[J]. Bioresource Technology,2011,102(6):4341-4346.
[18]Hong H,Peng W,Zhang M,et al.Thermodynamic analysis of membrane fouling in a submerged membrane bioreactor and its implications[J].Bioresource Technology,2013,146:7-14
[19]Genkin G,Waite T D,Fane A G,et al.The effect of vibration and coagulant addition on the filtration performance of submerged hollow fiber membranes[J].Journal of Membrane Science,2006, 281:726-734
[20]Aziz S Q,Aziz H A,Yusoff M S.Powdered activated carbon augmented double react-settle sequencing batch reactor process for treatment of landfill leachate[J].Desalination,2011,277: 313-320.
Effect of coordinated treatment of membrane bioreactor and powder activated carbon on marine aquaculture wastewater
Zeng Ganning1,2,Zhang Ruxia2,3,Gao Lulu1,Shen Jiangnan1,Tu Meiling3,Ruan huimin1,ZhangPeng4
(1.Ocean College,Zhejiang University of Technology,Hangzhou 310014,China;2.Academy of Marine Science&Technology,Zhejiang University of Technology,Hangzhou 310014,China;3.College of Chemical Engineering,Zhejiang University of Technology,Hangzhou 310014, China;4.Zhejiang Mariculture Research Institute,Wenzhou 325005,China)
With the rapid development of marine aquaculture industry,the amount of wastewater discharged is increasing and the water environment in the coastal areas is seriously deteriorated.Because of high concentration of total suspended matter;the content of soluble organic matter and inorganic matter in marine aquaculture wastewater is huge,whichresult indifficulties for treatment.In order to protect the marine environment and reduce the disease spread,the treatment of intensive aquaculture wastewater has become an inevitable trend.However,mariculture wastewater is more difficult to treat than that of freshwater,because of the effects of salinity,especially on membrane′s microbeeinhibition and contamination mitigation.In this paper,activated sludge within membrane bioreactor(MBR)disturbed by mariculture wastewater was investigated,during and after salt shock,meanwhile,effect of powdered activated carbon(PAC),was examined in parallel lab-scale MBR,particularly on their contaminant removal performance and membrane fouling influence,within the salinity ranging from 0 g/L to 35 g/L.Concentration of chemical oxygen demand(COD),ammonia nitrogen(NH+4-N)and nitrite nitrogen(NO2-N)were analyzed emphaticallyunder the long-term effect of macriculture wastewater,besides,variation of microorganism properties,membrane flux,and floc particle size were studied.Particularly,salinity changes range from 0 g/L to 5 g/L were selected to analyze corresponding,composition and concentrationchanges of the dissolved organic matter in bulk solution soluble microbileproducts,SMP and sludge flocs extracellular polymers substances(extracellular polymeric substances,EPS),which could help to explain the relationship between the hydrophobicity of sludge and polysaccharide, protein.The results showed that PAC could improve the anti-fouling ability of membrane,i.e.For MBR-PAC,The COD removal efficiencyis 7.3%higher than that of MBR,combined with better removal stability of NH+4-N and NO2-N.For MBR, the fluctuation of removal of NH+4-N and NO2-N was more obvious.In the process of salinity changes,the membrane flux of two parallel lab-scales presented a similar trend,in detail,the flux declined in the sensitive period andrecovered to a certain extent in stationary phase.However,the recovery period of MBR-PAC system was shorter than that of MBR,the change of flux is moreobvious in MBR.In result,the membrane flux under MBR-PAC system could be improved remarkable,which showed about 1.5 times than that of MBR,in the end,the flux of MBR was lower,and the membrane of MBR could be damaged.During the salinity changing process,PAC could increase the sludge relatively hydrophobic(RH) and average floc sludge particle size,at the same time,adsorption and flocculation ability of PAC would contribute the reduction of microbial metabolites,particularly for small molecular protein,obtaininga 34%reduction.At the end of operation,the sludge mean particle size of MBR-PAC waslarger,and the value increased 52 μm than that of MBR. Conclusions could be made that introduction of PAC is a useful mitigation strategy for MBR.Slow down membrane fouling rate.MBR-PAC is suitable for mariculture wastewater treatment,and the treatment effect is superior to MBR.
membranes bioreactor;activated sludge;salt shock;powder activated carbon;mariculture wastewater
10.11975/j.issn.1002-6819.2016.06.034
S959
A
1002-6819(2016)-06-0248-06
2015-08-04 2016-01-25
浙江省科技廳公益項目(2013C33005);浙江省海洋經(jīng)濟(jì)創(chuàng)新發(fā)展區(qū)域示范成果轉(zhuǎn)化及產(chǎn)業(yè)化項目(2015-83)
曾淦寧(1977-),男,博士,副教授;主要研究方向:海洋生化資源開發(fā)與環(huán)境保護(hù),杭州 浙江工業(yè)大學(xué)海洋學(xué)院,310014。
Email:gnzeng@zjut.edu.cn