喬 瑋,任征然,李晨艷,熊林鵬,李玉友,董仁杰,4
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自攪拌厭氧折流板反應(yīng)器連續(xù)處理豬場(chǎng)廢水的效果
喬 瑋1,2,任征然1,2,李晨艷1,2,熊林鵬1,2,李玉友3,董仁杰1,2,4※
(1. 中國農(nóng)業(yè)大學(xué)工學(xué)院,北京 100083; 2. 國家能源生物燃?xì)飧咝е苽浼熬C合利用技術(shù)研發(fā)(試驗(yàn))中心,北京 100083; 3. 日本東北大學(xué)土木與環(huán)境工程系環(huán)境保全研究室,仙臺(tái) 980-8579; 4. 中國農(nóng)業(yè)大學(xué)煙臺(tái)研究院,煙臺(tái) 264670)
該研究以豬場(chǎng)廢水為處理對(duì)象,采用自攪拌厭氧折流板反應(yīng)器(self-agitation anaerobic baffled reactor,SaABR)開展200 d的連續(xù)中溫厭氧消化試驗(yàn),考察在水力停留時(shí)間(hydraulic retention time,HRT)3、2、1和0.5 d梯度縮短的過程中,SaABR截留微生物的效果以及反應(yīng)器的產(chǎn)氣性能、穩(wěn)定性和污泥比產(chǎn)甲烷活性(specific methanogenic activity,SMA)。同時(shí),該研究還開展了全混式反應(yīng)器(completely stirred tank reactor,CSTR)78 d的連續(xù)對(duì)比試驗(yàn)。試驗(yàn)發(fā)現(xiàn),SaABR具有良好的截留微生物的作用,在HRT 3 d時(shí)SaABR第1至第4取樣口污泥揮發(fā)性固體(volatile solid,VS)濃度分別為10.2、4.1、44.2和2.5 g/L,而CSTR污泥VS質(zhì)量濃度僅為2.6 g/L。較高的微生物量顯著提高了有機(jī)物的降解率并降低了出水的有機(jī)酸濃度。隨著HRT的縮短,SaABR的降解率也呈現(xiàn)下降。在HRT 1 d時(shí),SaABR的單位VS產(chǎn)甲烷率為0.43 L/g,即使在HRT 縮短到0.5 d時(shí),仍然可實(shí)現(xiàn)穩(wěn)定的發(fā)酵產(chǎn)氣(單位VS產(chǎn)甲烷率為0.24 L/g),而CSTR反應(yīng)器由于微生物洗出不能在HRT 1 d時(shí)連續(xù)產(chǎn)氣。該研究的結(jié)果顯示,SaABR反應(yīng)器所具有截留微生物的良好特性,為養(yǎng)殖糞水的處理提供參考。
廢水;發(fā)酵;厭氧折流板反應(yīng)器;自攪拌
養(yǎng)豬業(yè)是中國養(yǎng)殖業(yè)中的重要產(chǎn)業(yè)之一,2016年全國肉豬出欄頭數(shù)為68 502萬頭[1]。據(jù)統(tǒng)計(jì),一個(gè)年出欄萬頭的規(guī)?;i場(chǎng)年排泄糞尿量為400萬t,若采用水沖清糞的方式,則豬場(chǎng)廢水年排量達(dá)到550多萬t[2]。豬場(chǎng)廢水COD 質(zhì)量濃度高達(dá)6.9~18.1 g/L[3-5],若不能有效處理,將會(huì)對(duì)環(huán)境造成嚴(yán)重的危害。厭氧消化處理豬場(chǎng)廢水在降解有機(jī)物的同時(shí)產(chǎn)生沼氣[6],是一種經(jīng)濟(jì)有效的廢水處理方法。
在眾多厭氧反應(yīng)器中,厭氧折流板反應(yīng)器(anaerobic baffled reactor,ABR)能夠分離水解酸化和產(chǎn)甲烷階段,反應(yīng)器具有兩相系統(tǒng)的優(yōu)點(diǎn),同時(shí)能夠截留微生物,大幅度的縮短水力停留時(shí)間(HRT)[7]。然而,折流板反應(yīng)器沒有攪拌系統(tǒng),反應(yīng)器內(nèi)微生物和有機(jī)物不能很好的混合接觸,傳質(zhì)較差[8]。為強(qiáng)化反應(yīng)器的混合和傳質(zhì),研究者們?cè)贏BR內(nèi)部設(shè)置可實(shí)現(xiàn)反應(yīng)器氣體循環(huán)的U型管,使反應(yīng)器可以實(shí)現(xiàn)無動(dòng)力攪拌[9-11]。這種自攪拌厭氧折流板反應(yīng)器(self-agitation anaerobic baffled reactor,SaABR)已在餐廚垃圾的厭氧處理中被發(fā)現(xiàn)有良好的性能[12-13]。目前,關(guān)于SaABR在養(yǎng)殖廢水的厭氧處理的研究還鮮有報(bào)道。
為此,本研究開展SaABR處理豬場(chǎng)糞水的連續(xù)試驗(yàn),考察反應(yīng)器連續(xù)運(yùn)行下逐級(jí)縮短HRT下的性能。為研究SaABR截留微生物的作用,采用與全混式反應(yīng)器(completely stirred tank reactor,CSTR)進(jìn)行比較。本研究結(jié)果將為SaABR反應(yīng)器處理養(yǎng)殖廢水的研究和應(yīng)用提供有意義的借鑒。
豬場(chǎng)廢水取自北京市北郎中種豬場(chǎng),取回后過40目篩去除大顆粒和樹葉等雜質(zhì)后備用;接種污泥取自該養(yǎng)殖場(chǎng)運(yùn)行良好的豬糞中溫厭氧發(fā)酵罐新鮮出料。豬場(chǎng)廢水和接種污泥的基本性質(zhì)如表1所示。
SaABR反應(yīng)器結(jié)構(gòu)由日本東北大學(xué)環(huán)境保全研究室設(shè)計(jì),反應(yīng)器的運(yùn)行方案參考該試驗(yàn)室以往研究發(fā)表的論文[9-12]。試驗(yàn)裝置如圖1所示,圖1a為SaABR裝置系統(tǒng),圖1b為CSTR裝置系統(tǒng)。SaABR系統(tǒng)主要包括基質(zhì)罐和發(fā)酵罐兩部分,發(fā)酵罐總?cè)莘e16 L,有效容積10 L。SaABR從左至右設(shè)置有4個(gè)隔室,第1隔室和第2隔室之間設(shè)置1個(gè)U形管,第2隔室上部完全密封,產(chǎn)生的沼氣儲(chǔ)存在第1隔室并將第1隔室液面壓低,當(dāng)液面低于U形管底部時(shí)迅速完成一次攪拌;第2到第4隔室上方連通,產(chǎn)生的沼氣可以直接排出后經(jīng)氣袋收集。該反應(yīng)器設(shè)有4個(gè)取樣口,從左到右為取樣口1至取樣口4(如圖1a所示)。進(jìn)、出料口與蠕動(dòng)泵(申辰BT100N)連接,通過定時(shí)器每天自動(dòng)進(jìn)出料,HRT為5和3 d時(shí)每天進(jìn)出料2次,HRT為2 d時(shí)每天進(jìn)出料4次,HRT為1和0.5 d時(shí)每天進(jìn)出料8次。CSTR總?cè)莘e為3 L,有效容積為2 L,HRT為5和3 d時(shí)該反應(yīng)器每天進(jìn)出料1次,HRT為2 d時(shí)每天進(jìn)出料2次,HRT為1 d時(shí)每天進(jìn)出料4次。2個(gè)反應(yīng)器浸置于(37±1)℃恒溫水箱中。產(chǎn)生的沼氣使用氣袋收集。反應(yīng)器啟動(dòng)期HRT均為5 d,反應(yīng)器的運(yùn)行方案如表2和表3所示。
表1 豬場(chǎng)廢水與接種污泥的基本性質(zhì)
注:TS:總固體;VS:揮發(fā)性固體;SS:懸浮固體;VSS:揮發(fā)性懸浮固體;TCOD:總化學(xué)需氧量;/:未檢測(cè)。
Note: TS: Total solid; VS: Volatile solid; SS: Suspended solids; VSS: Volatile suspended solid; TCOD: Total chemical oxygen demand; /: No detect.
圖1 SaABR和CSTR試驗(yàn)裝置
表2 SaABR運(yùn)行方案
表3 CSTR運(yùn)行方案
TS,VS,SS和VSS采用烘干法測(cè)定[14];COD采用重鉻酸鉀法[14];堿度采用滴定法[14];氨氮采用水楊酸-次氯酸鹽光度法[15]。pH值采用玻璃電極(Orion 5-Star pH)pH計(jì)測(cè)定。VFAs采用島津GC-2010Plus氣相色譜儀測(cè)定,采用30 m ×0.25 mm ×0.25m 的毛細(xì)柱 Rtx-wax色譜柱和FID檢測(cè)器,載氣(氮?dú)猓┓謮簽?.4 MPa,流速40 mL/min,氫氣流速為20~30 mL/min,進(jìn)樣口、色譜柱和檢測(cè)口溫度分別為230、60和250 ℃。沼氣成分(N2、CH4與CO2)采用島津GC-8A氣相色譜儀測(cè)定,色譜柱采用10 m×2 mm不銹鋼的,載氣(氫氣)分壓為0.38 MPa,流速為20~30 mL/min,進(jìn)樣口、色譜柱和檢測(cè)口溫度分別為120、50和120 ℃。每3 d取SaABR和CSTR反應(yīng)器出料測(cè)試各項(xiàng)指標(biāo)。沼氣量采用濕式氣體流量計(jì)(LML-1)測(cè)量。
在反應(yīng)器穩(wěn)定運(yùn)行3個(gè)HRT后,開始進(jìn)行產(chǎn)甲烷活性試驗(yàn)(specific methanogenic activity,SMA)[16]。每個(gè)血清瓶中加入90 mL營養(yǎng)液[17]并置于水浴鍋中預(yù)加熱至37 ℃,然后向血清瓶中加入10 mL從SaABR各取樣口取出的污泥;再向血清瓶中加入1 mL質(zhì)量濃度為240 g/L的乙酸鈉溶液,血清瓶中的乙酸質(zhì)量濃度為2 000 mg/L。立即向血清瓶中充入氮?dú)?0 s排出空氣,蓋上硅膠塞,用鋁蓋密封。每組試驗(yàn)設(shè)置2個(gè)平行。根據(jù)產(chǎn)氣量每1~3 d用玻璃注射器測(cè)沼氣產(chǎn)量,并分析沼氣成分。實(shí)際的SMA通過將線性甲烷積累速率的初始斜率除以血清瓶中加入的揮發(fā)性固體來計(jì)算[18]。
SaABR反應(yīng)器的運(yùn)行性能如圖2和圖3所示,CSTR反應(yīng)器性能如圖4所示。本試驗(yàn)的啟動(dòng)期較長,SaABR反應(yīng)器在第40天時(shí)產(chǎn)氣逐漸穩(wěn)定至0.56 L/(L·d),隨著HRT縮短容積產(chǎn)甲烷率逐漸升高,單位VS產(chǎn)氣率逐漸降低(如圖3所示)。在HRT為3和2 d時(shí)甲烷容積產(chǎn)氣率分別為0.85和1.14 L/(L·d)。當(dāng)HRT縮短至1和0.5 d時(shí),甲烷容積產(chǎn)氣率分別達(dá)到1.62和1.71 L/(L·d)。
圖2 SaABR連續(xù)運(yùn)行系統(tǒng)性能
如圖3所示,SaABR在HRT由3 d縮短到0.5 d的過程中,單位VS的甲烷產(chǎn)率分別是0.69、0.58、0.43和0.24 L/g。隨著HRT的縮短有機(jī)物降解率呈明顯的降低。本研究啟動(dòng)HRT為5 d,沒有測(cè)試更長HRT下的甲烷產(chǎn)率。有研究報(bào)道,折流板反應(yīng)器處理TS質(zhì)量濃度為50 g/L的豬糞在HRT為14 d時(shí)VS甲烷率產(chǎn)為0.59 L/g[19],與本研究HRT 3 d時(shí)的結(jié)果相近。
圖3 SaABR不同HRT條件下產(chǎn)甲烷情況
據(jù)此推測(cè),在中溫條件下SaABR在較短的HRT下即可取得較好的有機(jī)降解效果。CSTR隨著HRT由3 d縮短到2 d,容積產(chǎn)甲烷率從0.25 L/(L·d)提高至0.44 L/(L·d)。在HRT為1 d時(shí)CSTR產(chǎn)氣不穩(wěn)定,在運(yùn)行了14 d后,反應(yīng)器趨近于不產(chǎn)氣。CSTR停止產(chǎn)氣時(shí)pH值為7.51,VFAs質(zhì)量濃度為2 022 mg/L,反應(yīng)器未出現(xiàn)酸化現(xiàn)象。這個(gè)濃度的VFAs也不會(huì)對(duì)甲烷菌產(chǎn)生顯著的抑制作用[20]。產(chǎn)甲烷菌的倍增期為25 h[21],倍增期為65 h[22]。有研究發(fā)現(xiàn)HRT短于1 d時(shí),由于大部分產(chǎn)甲烷菌生長緩慢[23],反應(yīng)器內(nèi)微生物會(huì)被洗出而導(dǎo)致發(fā)酵失敗[24]。據(jù)此推測(cè)HRT為1 d時(shí)CSTR內(nèi)的微生物由于停留時(shí)間過短而被洗出,導(dǎo)致發(fā)酵失敗。表4對(duì)本研究及關(guān)于豬糞厭氧發(fā)酵產(chǎn)氣情況進(jìn)行了對(duì)比。
文獻(xiàn)報(bào)道的氨氮抑制濃度差異很大為1 700~14 000 g/L[25],大多數(shù)產(chǎn)甲烷菌最適pH值范圍為6.5~8.2[26],堿度需要在1~5 g/L以下[26]。如圖2e至g和f至h,本研究中SaABR出料氨氮質(zhì)量濃度在474~1 158 mg/L之間波動(dòng),CSTR氨氮質(zhì)量濃度在741~1 234 mg/L波動(dòng),沒有達(dá)到文獻(xiàn)中的抑制濃度。兩反應(yīng)器pH值均在7~8之間波動(dòng),在適合產(chǎn)甲烷菌生長范圍內(nèi)。兩反應(yīng)器堿度也在合適范圍內(nèi),均具有一定的緩沖能力。
表4 本研究的結(jié)果與文獻(xiàn)的對(duì)比
注:SPAG為懸浮顆粒附著生長反應(yīng)器。
Note: SPAG is suspended particle-attached growth reactor.
如圖2c,當(dāng)HRT為3、2、1 d時(shí),SaABR出液VFAs質(zhì)量濃度分為143、195和388 mg/L。當(dāng)HRT為0.5 d時(shí)VFAs質(zhì)量濃度達(dá)到了1 610 mg/L。CSTR反應(yīng)器中VFAs濃度在HRT為3、2和1 d時(shí)VFAs質(zhì)量濃度分別為793、1370和2 022 mg/L(圖4c)。圖5為HTR 3 d時(shí)SaABR各取樣口和CSTR出料污泥的VFAs和TS質(zhì)量濃度。SaABR反應(yīng)器從第1至第4取樣口取樣測(cè)得VFAs質(zhì)量濃度分別為375、327、64和70 mg/L。SaABR反應(yīng)器內(nèi)污泥大部分被截留在第3隔室,第3取樣口污泥TS質(zhì)量濃度最高為86.2 g/L,VFAs質(zhì)量濃度最低。CSTR污泥TS質(zhì)量濃度僅為5.4 g/L,VFAs質(zhì)量濃度為786 mg/L。
圖5 HRT 3 d時(shí)SaABR和CSTR內(nèi)VFAs和TS質(zhì)量濃度
有研究報(bào)道,采用SaABR反應(yīng)器處理TS質(zhì)量濃度為99 g/L的餐廚垃圾時(shí),HRT為15 d時(shí)取樣測(cè)試前3隔室VFAs質(zhì)量濃度逐漸從1 156 mg/L逐漸降低到708 mg/L,第三隔室底部VFAs質(zhì)量濃度降低至239 mg/L[12],與本研究變化趨勢(shì)相近。
圖6a至6e別為不同HRT條件下,SaABR反應(yīng)器內(nèi)各取樣口污泥TS和VS濃度,圖6f為CSTR反應(yīng)器不同HRT條件下出料污泥TS和VS濃度以及VS去除率。SaABR反應(yīng)器的取樣口如圖1a所示。SaABR反應(yīng)器內(nèi)污泥分布不均勻。隨著HRT縮短,SaABR下部2個(gè)取樣口(第1和第3取樣口)污泥的濃度呈現(xiàn)降低的趨勢(shì),上部2個(gè)取樣口(第2和第4取樣口)污泥的濃度呈現(xiàn)上升的趨勢(shì)。HRT為5、3、2、1和0.5 d時(shí)SaABR污泥的TS平均質(zhì)量濃度分別為34.1、30.1、27.2、23.6和19.7 g/L。這說明HRT的縮短降低了SaABR截留微生物的能力。CSTR反應(yīng)器的VS去除率隨著HRT縮短逐漸降低,HRT為5、3和2 d時(shí)VS去除率分別為49.4%、35.7%和33.7%。HRT為1 d時(shí),試驗(yàn)進(jìn)行14 d后,CSTR進(jìn)出料的濃度基本相同,說明微生物被洗出,已經(jīng)沒有微生物降解作用。SaABR相比于CSTR可以有效的截留微生物。
表5為HRT 3 d時(shí)SaABR各取樣口污泥在乙酸濃度為2 000 mg/L時(shí)的產(chǎn)甲烷活性。SaABR 4個(gè)取樣口的污泥SMA分別為116、97、44和85 mL/(g·d)。由于第3取樣口污泥VS濃度較高,為44.2 g/L,大量微生物被截留在第3取樣口,但可提供其降解的VFAs有限,所以其SMA最低僅為44 mL/(g·d)。
圖6 SAABR和CSTR反應(yīng)器內(nèi)污泥TS和VS濃度
表5 HRT 3 d污泥產(chǎn)甲烷活性對(duì)比
SaABR具有良好的微生物截留能力,污泥主要分布在第3和第4隔室之間。SaABR在較短HRT條件下有較高的產(chǎn)氣率,HRT 0.5 d時(shí)SaABR仍可以正常產(chǎn)氣,單位VS產(chǎn)甲烷率為0.24 L/g,而CSTR在HRT 1 d時(shí)由于微生物被洗出而停止產(chǎn)氣。隨著HRT縮短,SaABR內(nèi)污泥濃度逐漸降低,同時(shí)有機(jī)物降解率逐漸降低,出水VFAs質(zhì)量濃度增加。本研究的結(jié)果顯示,SaABR反應(yīng)器處理豬場(chǎng)廢水可以在較短HRT條件下取得良好的運(yùn)行效果。
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Continuous anaerobic treatment of swine wastewater by using self-agitation anaerobic baffled reactor
Qiao Wei1,2, Ren Zhengran1,2, Li Chenyan1,2, Xiong Linpeng1,2, Li Yuyou3, Dong Renjie1,2,4※
(1.100083; 2.,,(),100083; 3.,,980-8579; 4.,264670)
With the development of pig industry in China, environmental pollution from such development has become more and more serious. One of the most important problems of pig breeding is the wastewater treatment. Swine wastewater is characterized by the high concentrations of organic matters. Anaerobic digestion has been regarded as a promising technology for swine wastewater treatment to remove the high-concentration organic materials. At the same time, renewable energy in the form of biogas was produced through anaerobic degradation. Previous studies have reported that anaerobic baffled reactor (ABR) can achieve good performance in treating swine wastewater. However, due to the absence of agitation system, the mass transfer is an ABR is unsatisfactory. In order to improve the performance of an ABR, the self-agitation anaerobic baffled reactor (SaABR) was proposed. In the SaABR, a U tube was assembled inside the reactor. SaABR is previously studied in the anaerobic treatment. However, fewer its application in treating swine wastewater was found. The current study therefore investigated the performance of a long term operated SaABR in treating swine wastewater. The total and working volume of SaABR in this study were 16 and 10 L, respectively. Anaerobic treatment of swine wastewater for a period of 200-day was continuously conducted. Mesophilic condition was maintained at 37 ℃ while hydraulic retention time (HRT) was gradual shortening from 5, 3, 2, 1, to 0.5 days. The effects of HRT on the biomass retaining, biogas gas production, process stability, and specific methanogenic activity (SMA) was investigated. At the same time, in this study, we also conducted a 78-day continuous experiment by using a parallel continuous stirred tank reactor (CSTR) as control test. The results derived from this study indicated that SaABR significantly retained high biomass concentration. At the HRT 3 d period, the volatile solid (VS) concentration of the first to fourth sampling ports of SaABR was 10.2, 4.1, 44.2 and 2.5 g/L, respectively. The concentration of VS in the CSTR was as low as 2.6 g/L. The higher microbial biomass significantly increased the degradation efficiencies of organic and reduced the VFAs concentration of SaABR effluent. The degradation efficiency of SaABR also decreased with the shortening of HRT. The specific methane yield of the SaABR was 0.43 L/g at the HRT 1 d period. At the HRT 0.5d period stable biogas production can still be achieved. Through the long term experiment, an increase of volumetric gas production rate was observed: 0.85, 1.14, 1.62 and 1.71 L/(L·d) at HRTs 3, 2, 1 and 0.5 days, respectively. Specific methane gas yield decreased from 0.69 to 0.24 L/g when HRT was reduced from 3 to 0.5 d. These values were slightly higher than results of a previous study using ABR treating swine manure at 40 ℃, which reported specific methane yield was 0.59 L/g. The CSTR ceased to produce biogas at HRT 1 d due to the washout of biomass. At HRT 3 d period, the sludge SMA from the first to the fourth sampling port were 116, 97, 44 and 85 mL/(g·d), respectively. Conclusively, the results obtained in this study showed that SaABR had the advantages of retaining high biomass and would be a promising technology for the anaerobic treatment of swine wastewater.
wastewater; fermentation; anaerobic baffled reactor; self-agitation
10.11975/j.issn.1002-6819.2018.20.027
X712
A
1002-6819(2018)-20-0210-06
2010-04-26
2018-08-17
“十三五”國家重點(diǎn)研發(fā)計(jì)劃課題(2016YFD0501403)、北京市自然科學(xué)基金(6182017)和北京市科技計(jì)劃課題(D1611000016003;D1611000016001)
喬 瑋,副教授,博士,博士生導(dǎo)師,主要從事廢水和廢棄物的厭氧生物處理研究。Email:qiaowei@cau.edu.cn
董仁杰,教授,博士,博士生導(dǎo)師,主要從事生物質(zhì)能源與環(huán)境保護(hù)方面研究。Email:rjdong@cau.edu.cn
喬 瑋,任征然,李晨艷,熊林鵬,李玉友,董仁杰. 自攪拌厭氧折流板反應(yīng)器連續(xù)處理豬場(chǎng)廢水的效果[J]. 農(nóng)業(yè)工程學(xué)報(bào),2018,34(20):210-215. doi:10.11975/j.issn.1002-6819.2018.20.027 http://www.tcsae.org
Qiao Wei, Ren Zhengran, Li Chenyan, Xiong Linpeng, Li Yuyou, Dong Renjie. Continuous anaerobic treatment of swine wastewater by using self-agitation anaerobic baffled reactor[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2018, 34(20): 210-215. (in Chinese with English abstract) doi:10.11975/j.issn.1002-6819.2018.20.027 http://www.tcsae.org