雞糞高固體濃度進(jìn)料厭氧消化連續(xù)運(yùn)行性能

宋亞朋，喬 瑋，胡婉蓉，董仁杰

雞糞高固體濃度進(jìn)料厭氧消化連續(xù)運(yùn)行性能

宋亞朋1,2，喬 瑋1,2※，胡婉蓉3，董仁杰1,2

（1. 中國農(nóng)業(yè)大學(xué)工學(xué)院，北京 100083； 2. 中國農(nóng)業(yè)大學(xué)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. 中國地質(zhì)大學(xué)（北京）水資源與環(huán)境學(xué)院，北京 100083）

以雞糞為處理對(duì)象，進(jìn)料總固體（Total Solids, TS）濃度控制在15%，進(jìn)行雞糞高固體濃度進(jìn)料厭氧消化試驗(yàn)，在水力停留時(shí)間（Hydraulic Retention Time, HRT）為 60 d的條件下，連續(xù)運(yùn)行155 d考察發(fā)酵性能。試驗(yàn)結(jié)果表明，在有機(jī)負(fù)荷（Organic Load Rate, OLR）為1.5 g/(L·d)（以Volatile Solids, VS計(jì)算）和總氨氮（Total Ammonia Nitrogen, TAN）濃度7.5 g/L的條件下，甲烷產(chǎn)率達(dá)到326 mL/g，總揮發(fā)性脂肪酸（Total Volatile Fatty Acids, TVFA）濃度在0.5 g/L左右，pH值在8.3以上，實(shí)現(xiàn)了低有機(jī)酸殘留的雞糞高固體濃度進(jìn)料厭氧消化的穩(wěn)定運(yùn)行。雞糞的水解率、酸化率以及產(chǎn)甲烷率分別為61%、47%和47%。厭氧污泥的比產(chǎn)甲烷活性（Specific Methanogenic Activity, SMA）為0.042 g/(g·d)，顯示有較好的代謝活性，利用一級(jí)動(dòng)力學(xué)模型進(jìn)行模擬，動(dòng)力學(xué)常數(shù)為0.202 d-1，相關(guān)性系數(shù)為0.982。該研究驗(yàn)證了通過延長HRT適當(dāng)降低OLR的方式，雞糞高固體濃度進(jìn)料厭氧消化可以耐受極高的氨氮濃度，為工程應(yīng)用提供了可能性。

糞；厭氧消化；高固體；SMA；物料平衡

0 引 言

雞糞中含有大量易降解有機(jī)物，適合用厭氧消化的方式處理，產(chǎn)甲烷潛能達(dá)到300～370 mL/g[1-2]。但是，雞糞總氮含量占干質(zhì)量的 3.2%～4.9%[1, 3-4]，直接進(jìn)行厭氧消化易受高濃度氨氮的抑制[2, 5-6]，通常需要在厭氧處理前加水稀釋至總固體濃度低于10%。但是，加水稀釋增加了進(jìn)料體積及后續(xù)沼液產(chǎn)量，加劇了沼氣工程“沼液出路難”的壓力。另一方面，加水稀釋也減少了沼液中的氮含量，降低了沼肥營養(yǎng)價(jià)值。高固體濃度進(jìn)料厭氧消化具有減少反應(yīng)器體積，提高體積產(chǎn)氣量，降低加熱能耗，減少沼液產(chǎn)量，降低原料運(yùn)輸成本等優(yōu)勢[7-8]。如何減少稀釋用水，提高進(jìn)料物質(zhì)濃度，緩解氨抑制，實(shí)現(xiàn)高固體濃度進(jìn)料厭氧消化是雞糞處理的一個(gè)瓶頸問題。研究發(fā)現(xiàn)在高固體濃度進(jìn)料厭氧條件下，雞糞發(fā)酵很難成功。當(dāng)雞糞進(jìn)料總固體濃度為15%～20%，HRT （Hydraulic Retention Time）為20 d條件下，總揮發(fā)性有機(jī)酸最高達(dá)到25.0 g/L，甲烷產(chǎn)率最低下降至20 mL/g，厭氧消化過程處于崩潰狀態(tài)[9-10]。目前，高濃度雞糞進(jìn)料厭氧消化研究較少，進(jìn)料固體濃度、有機(jī)負(fù)荷、氨氮濃度以及它們的協(xié)同作用對(duì)厭氧消化性能的影響尚不明確，是否能建立穩(wěn)定運(yùn)行的雞糞高固體濃度進(jìn)料厭氧消化工藝還有待長期試驗(yàn)的證明。

本研究考察了進(jìn)料TS（Total Solid）濃度為15%、HRT 60 d條件下的高固體濃度雞糞進(jìn)料厭氧消化性能，通過反應(yīng)器長期運(yùn)行的試驗(yàn)為基礎(chǔ)，分析了物料平衡、污泥乙酸產(chǎn)甲烷活性等，以期為雞糞高固體濃度進(jìn)料厭氧消化的應(yīng)用提供試驗(yàn)支撐。

1 材料與方法

1.1 接種及物料

接種污泥取自試驗(yàn)室連續(xù)穩(wěn)定運(yùn)行100 d以上的中溫雞糞厭氧消化反應(yīng)器，該反應(yīng)器的進(jìn)料總固體濃度為10%，水力停留時(shí)間為20 d，攪拌均勻后接種到反應(yīng)器中。雞糞原料取自北京某養(yǎng)雞農(nóng)場，使用攪拌機(jī)（JYLC012，中國九陽）將雞糞進(jìn)行破碎、勻漿并于4℃環(huán)境下冷藏，使用時(shí)用去離子水將其TS稀釋至15%，接種污泥和進(jìn)料雞糞的理化性質(zhì)如表1所示。

1.2 試驗(yàn)設(shè)計(jì)

1.2.1 連續(xù)試驗(yàn)裝置

試驗(yàn)采用全混式連續(xù)攪拌反應(yīng)器，總體積6 L，有效容積4 L，放置在水浴槽中，水浴槽使用加熱器（AS ONE亞速旺，TMK-2K）控制溫度在(37±1)℃。每天手動(dòng)進(jìn)料一次，采用蠕動(dòng)泵（BT100N，保定申辰）出料保持反應(yīng)器相同液位高度，反應(yīng)器及其試驗(yàn)裝置流程如圖1所示。

表1 接種污泥和雞糞性質(zhì)

注：TS：總固體；VS：揮發(fā)性固體；TCOD：總化學(xué)需氧量；SCOD：溶解性化學(xué)需氧量；TVFA:總揮發(fā)性脂肪酸；TAN：總氨氮；FAN: 游離氨。

Note: TS: Total Solid; VS: Volatile Solid; TCOD: Total Chemical Oxygen Demand; SCOD: Soluble COD；TVFA: Total Volatile Fatty Acids; TAN: Total Ammonia Nitrogen; FAN: Free Ammonia Nitrogen.

1. 厭氧消化反應(yīng)器 2. 攪拌器 3. 進(jìn)料口 4. 出料泵 5. 沼液儲(chǔ)存罐 6. 取樣針 7. 沼氣取樣口 8. 水封瓶 9. H2S吸收瓶 10. 濕式氣體流量計(jì) 11. 水浴加熱器 12. 水浴槽 13. 溫度控制器 14. 平衡氣袋

1.2.2 比產(chǎn)甲烷活性測試

比產(chǎn)甲烷活性試驗(yàn)中，首先取發(fā)酵罐新鮮出料，在 8 000 r/min下離心20 min后去除上清液，然后加入營養(yǎng)液后混合均勻重復(fù)上述離心步驟，制備接種污泥，營養(yǎng)液成分見預(yù)試驗(yàn)[1]。將上述制備的接種污泥20 mL置于發(fā)酵瓶（120 mL）中，再次加入80 mL營養(yǎng)液，乙酸添加濃度設(shè)置為2 000 mg/L（試驗(yàn)組），未添加乙酸的發(fā)酵瓶為對(duì)照組，每組設(shè)置2個(gè)平行。使用氮?dú)獯祾甙l(fā)酵瓶中空氣營造厭氧環(huán)境，并使用橡膠塞密封，置于恒溫 （37±1）℃ 振蕩水槽（一恒科技，DKZ-3B）中，每2～4 d用玻璃注射器測定產(chǎn)氣量。

1.3 分析方法

TS、揮發(fā)性固體（Volatile Solids, VS）和揮發(fā)性懸浮固體（Volatile Suspended Solids, VSS）采用重量法、氨氮利用納什分光光度法、化學(xué)需氧量（Chemical Oxygen Demand, COD）采用重鉻酸鉀法、連續(xù)長期發(fā)酵實(shí)驗(yàn)沼氣產(chǎn)量采用濕式流量計(jì)（LML-1，北京金志業(yè)）、揮發(fā)性脂肪酸采用日本島津氣相色譜儀（GC-2010Plus），色譜柱為RTX-WAX毛細(xì)色譜柱，氮?dú)夥謮簽?.4 MPa，流速為40 mL/min，分流比30，進(jìn)樣口溫度設(shè)為230℃，F(xiàn)ID檢測器溫度250℃，進(jìn)樣體積10L、沼氣成分采用日本島津氣相色譜（GC-8A），色譜柱為10 m×2 mm不銹鋼色譜柱，氫氣分壓為0.6 MPa，載氣流速為20 mL/min，進(jìn)樣口溫度120℃、柱溫50℃，檢測器溫度120℃，進(jìn)樣體積為0.5 mL、pH值采用pH計(jì)（梅特勒-托利多，F(xiàn)E28）。

1.4 計(jì)算方法

污泥產(chǎn)甲烷活性測定中，產(chǎn)氣量以及產(chǎn)氣速率使用修正的Gompertz模型以及一級(jí)動(dòng)力學(xué)模型進(jìn)行擬合，分別如式（1）～（2）所示。比產(chǎn)甲烷活性值（Specific Methanogenic Activity, SMA）參照文獻(xiàn)[11-12]計(jì)算，如式（3）所示。

式中為時(shí)刻的累積產(chǎn)甲烷量，mL；0為最大產(chǎn)甲烷潛能，mL；max為最大產(chǎn)甲烷速率，mL/d；為遲滯期，d；為試驗(yàn)時(shí)間，d；e為自然常數(shù)，e≈2.7183。

式中C0最大產(chǎn)甲烷量，mL；C為最大產(chǎn)甲烷量減去時(shí)刻的產(chǎn)甲烷量，mL；為速率常數(shù)，d-1；1為消化時(shí)間，d。

公式（3）中CH4是累積產(chǎn)甲烷量，mL；V是接種污泥添加量，L；是與COD轉(zhuǎn)化系數(shù)（350 mL/g），每g COD產(chǎn)甲烷350 mL；VSS 是接種污泥生物量，g/L；2是具有最大產(chǎn)甲烷速率消化時(shí)間，d。

厭氧消化過程中的物質(zhì)轉(zhuǎn)化性能通過測定原料、沼液以及沼氣中的COD值，然后根據(jù)原料水解率、酸化率以及產(chǎn)甲烷率公式進(jìn)行計(jì)算，計(jì)算公式見文獻(xiàn)[13]。

2 結(jié)果與討論

2.1 長期厭氧消化性能

高固體濃度雞糞進(jìn)料厭氧消化反應(yīng)器運(yùn)行155 d，反應(yīng)器發(fā)酵性能見圖2及表2序號(hào)8。運(yùn)行初期0～40 d，容積產(chǎn)氣量由0.27 L/(L·d)逐漸上升至0.65 L/(L·d)（圖2a），甲烷產(chǎn)率也由150 mL/g上升至405 mL/g，隨后開始下降，60 d后甲烷產(chǎn)率穩(wěn)定維持在315～330 mL/g左右（圖2b）。整個(gè)運(yùn)行周期的甲烷含量均在70% 以上，運(yùn)行前40 d的甲烷含量達(dá)到81%，隨后甲烷含量降至76%（圖2c）。

另外，本文中采用長期運(yùn)行的雞糞發(fā)酵罐的沼液進(jìn)行接種，該發(fā)酵罐的雞糞進(jìn)料TS濃度 10%, HRT 20 d，OLR 3 g/(L·d)。本試驗(yàn)中進(jìn)料TS濃度升高至15%，OLR降低至1.5 g/(L·d)，運(yùn)行負(fù)荷比接種污泥之前所在的環(huán)境要低一些，這導(dǎo)致在進(jìn)料運(yùn)行初期，氨氮濃度還沒有明顯上升的情況下，有機(jī)物降解更加充分，有機(jī)酸濃度出現(xiàn)降低的趨勢。隨著發(fā)酵時(shí)間的延長，微生物系統(tǒng)進(jìn)入持續(xù)穩(wěn)定的發(fā)酵狀態(tài)，有機(jī)酸濃度略有升高，并維持了穩(wěn)定。在前40 d，TVFA平均濃度為420 mg/L，其中乙酸濃度為360 mg/L，占85%（圖2d）。運(yùn)行穩(wěn)定期（40～150 d），TVFA濃度穩(wěn)定在470 mg/L左右，仍以乙酸為主（85%），還有少量的丙酸（48 mg/L，10%），整個(gè)發(fā)酵過程的TVFA濃度均在較低水平。采用TS濃度低于10% 的雞糞原料作為發(fā)酵基質(zhì)，HRT設(shè)置為20～40 d，有機(jī)負(fù)荷為2.5～4 g/(L·d)，TAN 為2.5～6.5 g/L，消化系統(tǒng)TVFA達(dá)到0.65～6.7 g/L之間[9-10, 14-19]，可以看出，本試驗(yàn)設(shè)置進(jìn)料TS為15%、HRT 60 d達(dá)到了與進(jìn)料TS小于10%的雞糞濕式厭氧消化系統(tǒng)接近的發(fā)酵性能。對(duì)于高固體濃度雞糞進(jìn)料厭氧消化，采取延長HRT 適當(dāng)降低OLR的方式，能夠?qū)崿F(xiàn)發(fā)酵系統(tǒng)長期穩(wěn)定運(yùn)行。

由于接種污泥的TAN濃度較低（5.1 g/L），運(yùn)行初期反應(yīng)器中的TAN濃度也較低，0～40 d，反應(yīng)器TAN濃度為5.8 g/L，隨著反應(yīng)器周期性進(jìn)料，TAN濃度升高至7.5 g/L（圖2e）。厭氧消化中，TAN主要以銨離子（NH4+）和游離氨（NH3, Free Ammonia Nitrogen, FAN）兩種形式存在，發(fā)酵系統(tǒng)的TAN、pH值以及溫度等影響著FAN的濃度，F(xiàn)AN被認(rèn)為是對(duì)厭氧消化產(chǎn)生氨抑制的主要因 素[14-16]，其濃度超過0.6 g/L就會(huì)對(duì)厭氧消化產(chǎn)生抑制作用[17]。本試驗(yàn)中，發(fā)酵液的FAN濃度由運(yùn)行初期的1.5 g/L逐漸升高至2.6 g/L，pH值維持在8.3以上（圖2f），消化系統(tǒng)有充足的堿度保障，發(fā)酵系統(tǒng)未出現(xiàn)氨抑制。表2比較了高固體濃度雞糞進(jìn)料中溫（37℃）厭氧消化在不同TAN、FAN、OLR以及HRT條件下的發(fā)酵性能，HRT為20～30 d、有機(jī)負(fù)荷3.5～7.5 g/(L·d)、TAN 在6.0～ 12 g/L，甲烷產(chǎn)率普遍低于250 mL/g，VFA濃度積累超過25 g/L，發(fā)酵過程產(chǎn)生嚴(yán)重的氨抑制[9-10]。高固體濃度進(jìn)料雞糞厭氧消化，較短的HRT易造成氨抑制，發(fā)酵過程不易正常進(jìn)行。

圖2 容積產(chǎn)氣量、甲烷產(chǎn)率、沼氣成分、TVFA濃度、氨濃度以及pH值變化

表2 雞糞中溫厭氧消化性能對(duì)比

2.2 長期運(yùn)行的物質(zhì)轉(zhuǎn)化及物料平衡

通過高固體濃度雞糞進(jìn)料長期連續(xù)厭氧消化試驗(yàn)，基于物料平衡分析雞糞原料的物質(zhì)轉(zhuǎn)化及利用情況，如圖3所示。雞糞原料水解率、酸化率以及產(chǎn)甲烷率分別為61%、47%和47%（圖3a），原料酸化率和產(chǎn)甲烷率基本一致，證明TVFA保持較低的濃度，經(jīng)過酸化階段產(chǎn)生的揮發(fā)性脂肪酸基本都被轉(zhuǎn)化為了甲烷。而當(dāng)酸化率大于產(chǎn)甲烷率時(shí)，有機(jī)酸會(huì)大量積累，進(jìn)一步抑制產(chǎn)甲烷菌活性，導(dǎo)致惡性循環(huán)[20-22]。雞糞原料經(jīng)過水解，酸化，乙酸化過程形成供產(chǎn)甲烷菌利用的代謝基質(zhì)乙酸和氫氣，而VFAs是厭氧消化過程物質(zhì)轉(zhuǎn)化重要的中間產(chǎn) 物[23-24]，它是衡量水解、酸化過程的重要指標(biāo)。有研究表明，當(dāng)乙酸濃度高于2.3 g/L，丙酸濃度高于0.3 g/L或者丁酸濃度高于2.0 g/L時(shí)，產(chǎn)甲烷菌的活性就會(huì)受到抑制[25]。本試驗(yàn)中，TVFA的濃度為470 mg/L左右，殘余TVFA占進(jìn)料有機(jī)物總量0.5%以下，乙酸、丙酸是最主要的TVFA的組分，分別占85%和10%，其余組分僅占5% 左右（圖3b）。另外，原料水解率較酸化率高14% 左右，證明部分雞糞原料經(jīng)過水解后沒有被有效轉(zhuǎn)化為有機(jī)酸，這部分未被酸化的有機(jī)物增加了出料的有機(jī)物濃度。高固體濃度雞糞進(jìn)料厭氧消化中，氨抑制影響著雞糞原料的水解轉(zhuǎn)化效率[26]，有研究表明通過原位氨吹脫的處理方式降低雞糞原料氨氮濃度，水解轉(zhuǎn)化率能夠達(dá)到70%以上[27]。進(jìn)料TS含量也是影響雞糞原料水解、酸化轉(zhuǎn)化率的因素，在TS 5%和7.5%的進(jìn)料條件下，雞糞原料中超過60%的有機(jī)物能夠被轉(zhuǎn)化為CH4，水解轉(zhuǎn)化率能夠達(dá)到70%以上，酸化轉(zhuǎn)化率和產(chǎn)甲烷率均可達(dá)到60%以上[28]。而對(duì)于高固體濃度雞糞厭氧消化過程有機(jī)物質(zhì)的轉(zhuǎn)化情況，需要進(jìn)一步考察雞糞原料TS，TAN濃度與厭氧消化水解、酸化、產(chǎn)甲烷轉(zhuǎn)化率的關(guān)系。

注：PCOD為固體中的化學(xué)需氧量 (chemical oxygen demand, COD)；VFAs-COD是出料中VFAs對(duì)應(yīng)的COD；CODCH4是根據(jù)標(biāo)準(zhǔn)條件下COD與產(chǎn)甲烷轉(zhuǎn)化率系數(shù)計(jì)算得出的COD (350 mL/g)；SCOD* = SCOD - VFAs-COD；PCOD = TCOD - SCOD。

根據(jù)對(duì)進(jìn)出物料TS、VS以及COD的測定，計(jì)算發(fā)酵罐性能穩(wěn)定時(shí)期（41～153 d）的物料平衡。進(jìn)料中TCOD濃度為171 g/L，其中SCOD和PCOD的占比分別為26.5% 和73.5%。每日進(jìn)料雞糞TS和VS量分別為 10 g、6.1 g（VS/TS = 0.61)，出料TS、VS量分別為3.8 g、2.3 g，TS和VS的去除率分別為62% 和66%（圖3c），處理效果高于其他畜禽糞污（豬糞、牛糞等）厭氧消化VS的去除率[29]。連續(xù)發(fā)酵過程，PCOD、VFAs-COD、CODCH4分別占38.9%、0.3% 和47.4%（圖3d）。在較短HRT條件下的雞糞厭氧消化工藝中，雞糞進(jìn)料TS 為15%、HRT 20 d，PCOD、VFAs-COD、CODCH4分別占35%，8%和44%，VFAs-COD占比相比于本實(shí)驗(yàn)結(jié)果顯著提 高[30]。每日沼氣產(chǎn)量為2.5 L，其中CH4和CO2的含量分別為76.3%和23.7%（圖4a）。所以，采用適當(dāng)延長HRT適當(dāng)降低發(fā)酵體系OLR的方式能夠提高雞糞物料的利用效率，緩解氨抑制程度，實(shí)現(xiàn)高固體濃度雞糞進(jìn)料發(fā)酵體系的穩(wěn)定運(yùn)行。

從進(jìn)料物質(zhì)平衡的角度來看，高固體濃度雞糞進(jìn)料厭氧消化過程與傳統(tǒng)濕法厭氧消化相比，顯著降低了原料的稀釋用水和沼液產(chǎn)量，為工程應(yīng)用提供了可能性[12,31]，如圖4b所示。雞糞常被稀釋到較低的TS（＜10%）以避免氨抑制。將雞糞從25% 稀釋至8%（常規(guī)濕式厭氧消化），所需稀釋水量約為2.13 m3/t，這在以前的文獻(xiàn)中也有類似描述[31]。相比之下，在本研究中，TS稀釋為15% 時(shí)，稀釋用水量為0.67 m3/t，相應(yīng)減少了69%的稀釋水量和47%的沼液排放量，經(jīng)濟(jì)與環(huán)境效益顯著。

a. 雞糞代謝平衡圖a. Chicken manure metabolism balance diagramb. 不同固體含量雞糞厭氧消化物料平衡圖b. Material balance diagram with different solid contents

2.3 乙酸產(chǎn)甲烷活性

乙酸是產(chǎn)甲烷菌可以直接利用的前體物質(zhì)，污泥的乙酸產(chǎn)甲烷能力是反應(yīng)污泥活性的重要參數(shù)。本試驗(yàn)采用乙酸鈉為發(fā)酵基質(zhì)，進(jìn)行污泥產(chǎn)甲烷活性測試，并利用Gompertz模型擬合累積沼氣產(chǎn)量、甲烷產(chǎn)量和產(chǎn)甲烷速率，同時(shí)利用一級(jí)動(dòng)力學(xué)方程進(jìn)行污泥活性的表征，如圖5所示。乙酸濃度設(shè)置為2 000 mg/L，SMA值為0.042 g/(g·d)，高于其他高固體濃度雞糞進(jìn)料厭氧消化的SMA值[11,30]（0.032～0.042 g/(g·d)）。用Gompertz模型計(jì)算（圖5a），測得的累積沼氣產(chǎn)量和累積甲烷產(chǎn)量分別為412、286 mL/g，模型決定系數(shù)2為0.998，擬合結(jié)果與實(shí)際值相吻合。另外，Gompertz模型顯示產(chǎn)甲烷速率在5.1 d時(shí)達(dá)到最大35 mL/(g·d)，發(fā)酵遲滯期為1.34 d，主要因?yàn)榉磻?yīng)器長期運(yùn)行時(shí)乙酸濃度較低（500 mg/L以下），污泥活性測試中乙酸濃度設(shè)置為2 000 mg/L，微生物需要適應(yīng)一段時(shí)間才能夠發(fā)揮較好的乙酸代謝作用。圖5b 為乙酸產(chǎn)甲烷活性的一級(jí)動(dòng)力學(xué)模擬結(jié)果，動(dòng)力學(xué)常數(shù)為0.202 d-1，決定系數(shù)為0.982，擬合度也較高，說明乙酸降解過程符合一級(jí)動(dòng)力學(xué)特征，產(chǎn)甲烷速率與乙酸濃度呈正相關(guān)。

圖5 累積沼氣產(chǎn)量和沼氣產(chǎn)率以及一級(jí)動(dòng)力學(xué)模型

3 結(jié) 論

1）通過采取延長水力停留時(shí)間（60 d）適當(dāng)降低有機(jī)負(fù)荷的方式，在總氨氮為7.5 g/L的條件下實(shí)現(xiàn)了高固體濃度進(jìn)料（TS 15%）雞糞厭氧消化的長期穩(wěn)定運(yùn)行，甲烷產(chǎn)率達(dá)到326 mL/g。

2）雞糞原料水解率、酸化率以及產(chǎn)甲烷率分別為61%、47% 和47%，TVFA低于500 mg/L，系統(tǒng)未出現(xiàn)氨抑制和有機(jī)酸積累。污泥SMA值為0.042 g/(g·d)，具有良好的乙酸代謝活性。

3）高固體濃度雞糞進(jìn)料厭氧消化與常規(guī)濕式厭氧消化相比具有稀釋水量少、沼液產(chǎn)量小等優(yōu)點(diǎn)，具備經(jīng)濟(jì)效益和環(huán)境效益的雙重優(yōu)勢。

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Continuously operated process performance of anaerobic digestion of chicken manure with feeding high solid concentration

Song Yapeng1,2, Qiao Wei1,2※, Hu Wanrong3, Dong Renjie1,2

(1.College of Engineering, China Agricultural University, Beijing 100083, China;2 .Research & Development Center for Efficient Production and Comprehensive Utilization of Biobased Gaseous Fuels, Energy Authority, National Development and Reform Committee, China Agricultural University, Beijing 100083, China; 3. School of Water Resources and Environment, China University of Geosciences(Beijing), Beijing 100083, China)

Chicken manure contains a lot of easily degradable organic matter suitable for anaerobic digestion (AD). But, a high concentration of ammonia nitrogen has posed a great challenge to the AD process. Diluting with water can be used to increase the influent volume. Correspondingly, the subsequent digestate yield can be reduced with the decrease of the nitrogen content, as well as the nutritional value of organic fertilizer. It is very necessary to balance between the dilution water and the solid concentration of feedstock for a higher solid AD process. However, only a few studies are reported on the high solid chicken manure AD at present. It is still lacking on the performance of AD under the feedstock with solid concentration, organic load, ammonia nitrogen concentration, and their synergistic effects. In this study, a long-term experiment was carried out to establish the stable and operational high solid AD process of chicken manure. The chicken manure with a high total solid (TS 15%) was also disposed of by the AD process under the hydraulic retention time (HRT) of 60 d through 155 days. The experimental results showed that the methane yield was 326 mL/g (Volatile Solids, VS) under the organic load rate (OLR) of 1.5 g/(L·d) and the total ammonia nitrogen (TAN) concentration of 7.5 g/L. The concentration of total volatile fatty acids (TVFA) was about 470 mg/L, and the pH was above 8.3, indicating the stable operation with low TVFA residues. The hydrolysis, acidogenesis, and methanogenesis efficiencies of chicken manure were 61%, 47%, and 47%, respectively. Among them, the same acidogenesis and methanogenesis efficiencies indicated that the TVFA maintained a low concentration because the TVFA production through the acidogenic phase was been mostly converted into methane. The relationship was also determined between the concentration of TS and TAN chicken manure with the conversion efficiencies of the hydrolysis, acidogenesis, and methanogenesis. The AD performance was also evaluated under different chemical oxygen demand (COD) concentrations of the influent and effluent. The total COD (TCOD) concentration of the feedstock was 171 g/L. The proportions of soluble COD (SCOD) and particulate COD (PCOD) were 26.5% and 73.5%, respectively. In the long-term AD process, the PCOD, VFA-COD, and CH4-COD accounted for 38.9%, 0.3%, and 47.4%, respectively. The biogas production was 2.5 L/d, including 76.3% CH4and 23.7% CO2. The specific methanogenic activity (SMA) of the anaerobic sludge was 0.042 g/(g·d), indicating superior metabolic activity. The accumulation biogas yield and accumulation methane yield were 412 mL/g and 286 mL/g, respectively. The model fitting coefficient2was 0.998 by the Gompertz model. The kinetic constant was 0.202 d-1and the correlation coefficient was 0.982 by the first-order model. Consequently, the degradation process of acetate was in line with the first-order kinetic characteristics, where the methane production rate was positively correlated with the concentration of acetate. The high solid AD of chicken manure can be widely expected to tolerate the extremely high concentration of ammonia nitrogen. Therefore, the improved AD can be used to greatly reduce the dilution water of feedstock and the digestate yield, compared with the conventional. This finding can also provide a promising potential for the engineering application of AD chicken manure in biogas plants.

manures; anaerobic digestion; high total soild concentration; SMA; mass balance

10.11975/j.issn.1002-6819.2021.21.027

X712

A

1002-6819(2021)-21-0237-07

宋亞朋，喬瑋，胡婉蓉，等. 雞糞高固體濃度進(jìn)料厭氧消化連續(xù)運(yùn)行性能[J]. 農(nóng)業(yè)工程學(xué)報(bào)，2021，37(21)：237-243.doi：10.11975/j.issn.1002-6819.2021.21.027 http://www.tcsae.org

Song Yapeng, Qiao Wei, Hu Wanrong, et al.Continuously operated process performance of anaerobic digestion of chicken manure with feeding high solid concentration[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2021, 37(21): 237-243. (in Chinese with English abstract) doi：10.11975/j.issn.1002-6819.2021.21.027 http://www.tcsae.org

2021-07-19

2021-10-10

北京市自然科學(xué)基金（6182017）

宋亞朋，博士生，研究方向?yàn)殡u糞厭氧處理。Email：1053097879@qq.com

喬瑋，博士，教授，研究方向?yàn)閺U水和廢棄物的厭氧生物處理。Email：qiaowei@cau.edu.cn; wayqiao@sina.cn