侯善策,沈玉君,王惠惠,周海賓,程紅勝,張宏圖,3,范盛遠
農(nóng)村戶用廁污堆肥反應(yīng)器設(shè)計與試驗
侯善策1,2,沈玉君1,2,王惠惠1,2,周海賓1,2,程紅勝1,2※,張宏圖1,2,3,范盛遠1,2
(1. 農(nóng)業(yè)農(nóng)村部規(guī)劃設(shè)計研究院農(nóng)村能源與環(huán)保研究所,北京 100121;2. 農(nóng)業(yè)農(nóng)村部資源循環(huán)利用技術(shù)與模式綜合性重點實驗室,北京 100121;3. 黑龍江八一農(nóng)墾大學(xué)工程學(xué)院,大慶 163319)
針對農(nóng)村戶用廁所環(huán)境條件差、廁污處理困難等問題,該研究研制了一種具有負壓抽吸進料-螺旋盤管曝氣-膜輔助加熱功能的110 L農(nóng)村戶用廁污堆肥反應(yīng)器。根據(jù)工程熱力學(xué)和生物學(xué)原理,設(shè)計了廁污負壓抽吸進料機構(gòu)、螺旋盤管曝氣系統(tǒng)和膜輔助加熱機構(gòu)等關(guān)鍵部件,集成反應(yīng)器控制單元,并開展反應(yīng)器性能試驗。試驗結(jié)果表明:堆肥高溫期(50 ℃)維持5 d,連續(xù)發(fā)酵15 d后,蛔蟲卵死亡率達到100%,大腸菌值檢測為46個/g(≤100個/g),種子發(fā)芽指數(shù)為88.4%,滿足《糞便無害化衛(wèi)生標準》要求。該研究可為農(nóng)村戶用廁污無害化處理及肥料化利用提供裝備支撐。
堆肥;糞;試驗;廁污;無害化;反應(yīng)器
廁污堆肥是農(nóng)村廁污資源化利用的主要途徑之一,對推進農(nóng)村廁所革命具有重要作用[1-2]。集約化堆肥裝備多針對規(guī)模化畜禽養(yǎng)殖場或有機肥工程設(shè)計,在堆肥工藝、處理能力、運行方式、環(huán)境友好方面與農(nóng)村戶廁堆肥需求差距較大[3-8]?,F(xiàn)有的農(nóng)村戶用廁污堆肥反應(yīng)器主要有臥式和微生物廁污堆肥反應(yīng)器等,臥式堆肥反應(yīng)器容積小,難以實現(xiàn)連續(xù)堆肥;微生物廁污堆肥反應(yīng)器需要定期更換菌種,操作技能要求高[9-11]。由于廁污含水率高、致病菌多、碳氮比低,處理不好極易導(dǎo)致糞口疾病傳播[12-13]。因此,本研究基于現(xiàn)有生態(tài)旱廁產(chǎn)品,提出農(nóng)村戶用廁污分層堆肥工藝,設(shè)計了一種移動式農(nóng)村戶用廁污堆肥反應(yīng)器(以下簡稱反應(yīng)器),以期為農(nóng)村廁所革命提供技術(shù)與裝備支撐。
反應(yīng)器結(jié)構(gòu)如圖1所示,主要由糞污收集單元、好氧發(fā)酵單元、增溫保溫單元和曝氣單元組成。收集單元主要包括坐便器、進污管和負壓風(fēng)機;好氧發(fā)酵單元主要包括反應(yīng)器腔體、篩板、導(dǎo)氣管和出料口等;增溫保溫單元主要包括加熱膜、保溫棉和密封蓋;曝氣單元主要包括曝氣風(fēng)機、曝氣管和流量計等。采用負壓風(fēng)機抽吸結(jié)構(gòu)自動收集廁污;采用環(huán)形盤管曝氣結(jié)構(gòu),配以定時器和曝氣風(fēng)機,對堆肥過程進行可控曝氣;采用“膜加熱+保溫棉”結(jié)構(gòu),對反應(yīng)器進行增溫保溫,滿足寒冷氣候條件下堆肥要求;堆肥反應(yīng)器整體可移動,便于安裝維護。
1.負壓風(fēng)機 2.排氣孔 3.密封蓋 4.排氣管 5.溫度傳感器 6.反應(yīng)器腔體 7.保溫棉 8.篩板 9.出料口 10.滲濾液出口 11.萬向輪 12.曝氣管 13.加熱膜 14.流量計 15.曝氣風(fēng)機 16.控制器 17.進污管 18.坐便器
根據(jù)廁污特點和糞污無害化處理需求,采用負壓進料-分層發(fā)酵-序批出料堆肥工藝。工作時,在篩板上預(yù)先鋪放一層粉碎至2~3 cm的玉米秸稈,啟動負壓風(fēng)機,將坐便器中的糞污抽吸至反應(yīng)器內(nèi)秸稈層上,抽吸完畢后,在糞污上方再鋪放一層碎秸稈。啟動曝氣風(fēng)機,根據(jù)廁污堆肥曝氣工藝設(shè)定曝氣參數(shù),空氣通過曝氣盤管吹入反應(yīng)器腔體內(nèi),為堆肥物料提供發(fā)酵所需氧氣。根據(jù)堆肥環(huán)境,適時啟動加熱單元,并調(diào)整加熱功率。發(fā)酵周期結(jié)束后,將物料從底部出料口排出。新糞污再通過負壓風(fēng)機抽吸至反應(yīng)器內(nèi),進行新一批次發(fā)酵。
反應(yīng)器參數(shù)主要根據(jù)堆肥物料質(zhì)量和實際工作條件進行確定。反應(yīng)器容積為110 L、工作環(huán)境溫度不低于-20 ℃、反應(yīng)器最大功率為1.29 kW、堆肥周期15 d。
反應(yīng)器腔體用于盛裝堆肥物料,為堆肥物料提供好氧發(fā)酵環(huán)境。根據(jù)前期預(yù)試驗,廁污與玉米秸稈質(zhì)量比為4:1時發(fā)酵效果較好。根據(jù)現(xiàn)有生態(tài)旱廁產(chǎn)品技術(shù)參數(shù),采用批次抽糞工藝,每5 d抽吸1次,每次糞污抽吸量約為8 kg。根據(jù)堆肥經(jīng)驗,堆肥周期設(shè)為15 d,為使第1批次物料滿足發(fā)酵周期要求,反應(yīng)器有效容積應(yīng)能滿足3批次抽吸的廁污堆肥體積,經(jīng)測量堆肥物料容重為375 kg/m3,故反應(yīng)器有效容積應(yīng)大于80 L,同時考慮負壓風(fēng)機的安裝空間,物料高度不應(yīng)超過負壓風(fēng)機進氣口位置(負壓風(fēng)機高0.15 m)。結(jié)合現(xiàn)有堆肥反應(yīng)器研究[5],反應(yīng)器腔體選用圓柱形,參照常見攪拌容器常用裝料高徑比[14](一般為1~2),設(shè)計反應(yīng)器腔體內(nèi)徑為0.45 m,反應(yīng)器腔體高度為0.7 m,總?cè)莘e為110 L,其中堆肥物料堆高為0.5 m(其中每層秸稈高約0.12 m,每層廁污高約0.047 m,共4層秸稈,3層廁污。),有效容積為80 L,反應(yīng)器結(jié)構(gòu)如圖2所示。
1.反應(yīng)器腔體 2.負壓風(fēng)機 3.秸稈 4.廁污
2.2.1 曝氣管路
為減小曝氣阻力,提高曝氣均勻性,曝氣管按阿基米德螺旋線排布,通氣孔均布于管上,在通氣主管上設(shè)置單向閥以防止氣體回流,為便于加工,通氣管采用硬質(zhì)抗腐蝕膠管,管路結(jié)構(gòu)如圖3所示。管路總長度為2 m,根據(jù)堆肥系統(tǒng)設(shè)計經(jīng)驗,選擇曝氣管內(nèi)徑選20 mm,曝氣孔的孔徑為2 mm,孔間距200 mm[15]。
1.曝氣管 2.曝氣孔 3.反應(yīng)器內(nèi)壁 4.單向閥
2.2.2 曝氣頻率和速率
曝氣頻率和速率是好氧發(fā)酵過程中的關(guān)鍵參數(shù),需依據(jù)理論曝氣量最大值進行設(shè)計[3]。曝氣量與脫水量和有機降解量密切相關(guān),對于農(nóng)村廁污堆肥,以無害化處理為主要目標,以有機質(zhì)降解量作為理論曝氣量的計算依據(jù)。
根據(jù)褚蓮清等[16]研究,向1 kg干物料中通入480 L空氣,微生物可降解0.125 kg有機質(zhì),根據(jù)堆肥經(jīng)驗,發(fā)酵物料初始含水率一般為65%[15],則氧化1 kg物料所需空氣量為168 L,以堆肥物料質(zhì)量30 kg(按廁污與玉米秸稈質(zhì)量比4:1,3批次廁污共24 kg,秸稈6 kg)計算,則總曝氣量為5 040 L。
堆肥反應(yīng)器采用間歇式曝氣工藝,已有研究表明,堆體好氧發(fā)酵過程中氧體積分數(shù)低于8%時,會抑制好氧發(fā)酵進程[3],為穩(wěn)定堆體內(nèi)含氧量,按每30 min一個曝氣周期計算,曝氣頻率為間隔26 min曝氣4 min[3],計算得出曝氣速率為1.75 L/min。
2.2.3 曝氣風(fēng)機選型
曝氣風(fēng)機作為曝氣系統(tǒng)的動力源是堆肥裝置重要組成部件,不同的使用條件對曝氣風(fēng)機的要求不同,合理選擇曝氣風(fēng)機既能滿足堆肥需求,又可節(jié)約運行成本。曝氣風(fēng)機選擇依據(jù)為反應(yīng)器曝氣風(fēng)量和風(fēng)壓。風(fēng)壓與壓力損失密切相關(guān)。壓力損失包括空氣穿透堆肥物料所產(chǎn)生的堆體壓力損失和穿過管路產(chǎn)生的管路壓力損失。
好氧發(fā)酵過程中,空氣透過物料間空隙為堆體提供發(fā)酵所需氧氣,氣體通過堆體過程中會產(chǎn)生壓力損失[16]:
氣體在管路中的壓力損失主要為沿程壓力損失2,其計算公式為[16]
由此得出整個曝氣系統(tǒng)的壓力損失為1.33 kPa??紤]到物料對曝氣孔可能產(chǎn)生的堵塞因素,對照風(fēng)機壓力曲線選擇最大風(fēng)壓20 kPa、最大曝氣量為25 L/min 的AC0-001型空氣壓縮泵。
2.2.4 負壓風(fēng)機選型
負壓風(fēng)機的型號依據(jù)抽吸廁污所需風(fēng)壓確定,負壓風(fēng)機的壓力損失主要包括廁污遷移過程中克服重力而引起的壓力損失和導(dǎo)污管路壓力損失。其中廁污重力損失根據(jù)公式(3)計算
導(dǎo)污管路壓力損失主要由沿程壓力損失和局部壓力損失組成,其計算公式為[16]
計算得沿程壓力損失為4.8 kPa,局部壓力損失為0.01 kPa,故管路總壓力損失為4.81 kPa。負壓風(fēng)機所需壓力為10.63 kPa。結(jié)合風(fēng)量和風(fēng)壓,對照風(fēng)機壓力曲線選擇最大風(fēng)壓14 kPa、最大風(fēng)量2 416 L/min的HG310-AS3型負壓風(fēng)機。
堆肥溫度是影響堆肥工藝和堆體中微生物活動的重要因素,堆體溫度高于30℃比較適合微生物發(fā)酵[17]??紤]到中國北方冬季氣溫最低可達-20℃,堆肥發(fā)酵過程需采取輔助升溫措施,根據(jù)公式[18]6計算發(fā)酵所需外部提供熱量
考慮有機質(zhì)降解產(chǎn)熱、反應(yīng)器外壁散失熱量和曝氣帶走熱量等其他熱量損失,若使整個堆肥周期維持熱平衡,計算得出加熱膜最小產(chǎn)熱值為12 321.9 kJ,換算得膜加熱器最小加熱功率為34.2 W。
圖4為加熱膜結(jié)構(gòu)圖,為避免加熱器過載,選擇型號JK-002、最大功率為100 W的膜加熱器。加熱功率通過功率調(diào)節(jié)器進行調(diào)節(jié),同時為提升加熱、保溫效果,采用“膜加熱+保溫棉”組合結(jié)構(gòu),將加熱膜貼敷于反應(yīng)器外壁。為提升加熱均勻性,采取雙膜對稱布置,貼附于反應(yīng)器外壁上。
1.控溫開關(guān) 2.電源線 3.加熱膜 4.電阻絲
本試驗于2019年9月在農(nóng)業(yè)農(nóng)村部規(guī)劃設(shè)計研究院(雙橋院區(qū))實驗室進行,環(huán)境溫度為17~22 ℃。以廁污、玉米秸稈為原料,廁污取自化糞池進糞口固體糞樣,糞便含水率為83.2%,碳氮比為2.94,pH值為7.4,玉米秸稈購自黑龍江省,含水率9.65%,碳氮比為64.17,pH值為7.1,粉碎粒徑為1~2 cm。
采用自主研發(fā)的堆肥反應(yīng)器進行靜態(tài)堆肥試驗(見圖5),采用序批式分層發(fā)酵方法,將糞便和玉米秸稈按照質(zhì)量比4:1分層平鋪于反應(yīng)器中,設(shè)置曝氣頻率為間隔26 min曝氣4 min,曝氣速率為1.75 L/min。分別在第0、3、6、9、12、15 d采樣,采集到的樣品置于-4 ℃保存?zhèn)溆谩?/p>
1.反應(yīng)器 2.曝氣風(fēng)機 3.控制器 4.加熱膜 5.溫度傳感器
堆肥過程中,反應(yīng)器內(nèi)發(fā)酵物料溫度采用在線監(jiān)測,將溫度傳感器安置在發(fā)酵物料中心位置,監(jiān)測發(fā)酵物料中心溫度;pH值和種子發(fā)芽指數(shù)取樣后實驗室分析測定,測定方法參照《堆肥工程實用手冊》[15];蛔蟲卵和糞大腸菌值委托華測檢測認證集團北京有限公司檢測,反應(yīng)器能耗委托農(nóng)業(yè)農(nóng)村部農(nóng)業(yè)機械試驗鑒定總站檢測。
如圖6所示。堆體在好氧發(fā)酵前2 d,秸稈與廁污分層排布,臭味重。隨著好氧發(fā)酵過程進行,廁污逐漸融入秸稈縫隙,與秸稈混成一體,堆體顏色由黃色逐漸呈深褐色,臭味減弱,好氧發(fā)酵10 d后,堆體呈現(xiàn)淺黑色,臭味消失,物料表面分布有白色絲狀物,堆體松散、濕潤。
圖6 堆肥溫度變化曲線
堆體溫度可間接反應(yīng)堆體中菌群活動的強弱和發(fā)酵所屬階段。根據(jù)《畜禽糞便堆肥技術(shù)規(guī)范》(NYT 3442—2019)[19],高溫好氧堆肥處理有機廢棄物堆體溫度大于50 ℃的時間應(yīng)持續(xù)5~7 d。如圖6所示,試驗過程中,物料發(fā)酵溫度高于50℃的時間持續(xù)5 d。第15天堆肥物料蛔蟲卵死亡率100%,糞大腸菌值為46個/g(≤100個/g),滿足糞污無害化處理要求[20]。
堆肥腐熟度通過種子發(fā)芽試驗進行評價[21-23]。如圖7所示,堆肥第15天的種子發(fā)芽指數(shù)達到88.4%,與現(xiàn)有30 d堆肥周期的廁污堆肥反應(yīng)器相比[24],反應(yīng)器可以實現(xiàn)堆肥快速腐熟。
圖7 種子發(fā)芽指數(shù)變化曲線
處理周期和運行能耗是影響農(nóng)村戶廁推廣應(yīng)用的關(guān)鍵因素。為便于比較分析,選擇與目前農(nóng)村常見的三格式和生物凈化槽戶廁對比分析,比較不同類型廁所的處理周期和管護費用。其中處理周期是指廁污進入反應(yīng)器至完成無害化處理所消耗的時間;管護費用是指農(nóng)村戶廁維持穩(wěn)定運行所需支付的運行管理費用。本研究所設(shè)計的廁污堆肥反應(yīng)器實現(xiàn)廁污無害化處理的周期為15 d,經(jīng)第三方檢測日均耗電量為0.08 kW·h。三格式戶廁最短處理周期為60 d[24],每年需清掏2次,由于養(yǎng)分濃度低、處理費時費力,一般采用第三方機構(gòu)處理,清理費用約50元/次。生物凈化槽式戶廁處理周期為90 d[25],每年需清掏3次,處理費用每次約50元。三格式戶廁每年管護費用約100元[26],生物戶廁約150元,本研究設(shè)計的廁污堆肥反應(yīng)器無廢液產(chǎn)生,處理后的剩余物為堆肥產(chǎn)品,可直接還田應(yīng)用,無需第三方處理,運行維護費僅為電費,堆肥升溫期加熱器連續(xù)工作,其余時間間斷性工作,廁污堆肥反應(yīng)器每年耗電費用為84元。廁污堆肥反應(yīng)器每年運行費用相比三格化糞池節(jié)約16%,比生物凈化槽式戶廁節(jié)約44%。因此,廁污堆肥反應(yīng)器具有堆肥周期短、管護費用低等優(yōu)勢。
1)設(shè)計了一種具有負壓抽吸進料-螺旋盤管曝氣-膜輔助加熱功能的農(nóng)村戶用廁污堆肥反應(yīng)器,最大容積為110 L,反應(yīng)器功率為1.29 kW,堆肥周期為15 d,采用負壓進料-分層發(fā)酵-序批出料堆肥工藝,曝氣頻率為間隔26 min通氣4 min,曝氣速率為1.75 L/min。
2)通過農(nóng)村戶用廁污堆肥反應(yīng)器性能試驗得出,堆體溫度維持5 d高于50℃。堆肥結(jié)束后,蛔蟲卵死亡率達到100%,糞大腸菌值為46個/g(≤100個/g),種子發(fā)芽指數(shù)達到88.4%,滿足堆肥物料無害化和腐熟要求。農(nóng)村戶用廁污堆肥反應(yīng)器每年管護費用較三格化糞池節(jié)約16%,較生物凈化槽式戶廁節(jié)約44%,表明該農(nóng)村戶用廁污堆肥反應(yīng)器可實現(xiàn)廁污無害化處理和快速堆肥,具有堆肥周期短、管護費用低等優(yōu)勢。
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Design and experiment of composting reactor for rural household toilet sewage
Hou Shance1,2, Shen Yujun1,2, Wang Huihui1,2, Zhou Haibin1,2, Cheng Hongsheng1,2※,Zhang Hongtu1,2,3, Fan Shengyuan1,2
(1.,,100121,; 2.,100121,;3.,,163319,)
Toilet waste composting is one of the main ways of rural toilet sewage resource utilization, which plays an important role in promoting the rural toilet revolution. In order to solve the problems of difficult disposal of rural toilet manure and poor environmental sanitation in rural toilets, a 110 L rural household composting reactor with negative pressure suction, spiral feeding- spiral coil aeration-membrane auxiliary heating was designed in this paper. The reactor structure included manure collection unit, aerobic fermentation unit, heat preservation unit and aeration unit. According to the principle of biological and thermodynamic, the negative pressure fan suction was used to collect manure automatically. In order to reduce the pressure loss of aeration fan, the aeration pipe was arranged Archimedean spiral structure, and the timer and aeration fan were used to realize controllable ventilation in composting process and improve composting quality. Insulation cotton membrane heating structure was adopted to achieve the heating and insulation of the reactor. The power of the reactor was 1.29 kW, the composting cycle was 15 d, the aeration frequency was 4 min per 26 min interval, the aeration rate was 1.75 L/min. The performance tests of composting reactor were conducted in September 2019. The manure and corn stalks with 1-2 cm particle size were placed in the reactor layer by layer according to the mass ratio of 4:1, and the samples were taken at 0, 3, 6, 9, 12 and 15 d after composting, respectively. The physical and chemical properties, such as temperature, water content, volatile solids, reliable content, seed germination index, the number of worm eggs and fecal coliforms of the samples during the aerobic fermentation process were tested, respectively. The results showed that the stalks and manure were layered with a strong odor during the first 2 d of aerobic fermentation. With the progress of aerobic fermentation, the manure gradually integrated into the gap between stalks and mixed with stalk. The color of the manure turned progressively dark brown and the odor faded. After 10 d of aerobic fermentation, the pile was dark brown, odorless, fluffier and moister with white filaments distributed on the surface. The high-temperature period lasted for 5 d. After 15 d of continuous fermentation, the fecal coliform bacteria was 46 MPN/g (≤100 MPN/g), the mortality rate of worm egg was 100%, and the seed germination index was 88.4%, which met the sanitary standard of harmless manure. The annual maintenance cost was saving 16% compared to the three-slot septic tank and 44% compared to biological purification tank household toilets.
composting; manures; experiments; sewage; harmless; reactor
侯善策,沈玉君,王惠惠,等. 農(nóng)村戶用廁污堆肥反應(yīng)器設(shè)計與試驗[J]. 農(nóng)業(yè)工程學(xué)報,2020,36(14):237-242.doi:10.11975/j.issn.1002-6819.2020.14.029 http://www.tcsae.org
Hou Shance, Shen Yujun,Wang Huihui, et al. Design and experiment of composting reactor for rural household toilet sewage[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2020, 36(14): 237-242. (in Chinese with English abstract) doi:10.11975/j.issn.1002-6819.2020.14.029 http://www.tcsae.org
2020-02-27
2020-07-10
農(nóng)業(yè)農(nóng)村部規(guī)劃設(shè)計研究院自主研發(fā)項目-寒旱區(qū)生態(tài)旱廁及糞污農(nóng)用技術(shù)研究(ZZYFXKFZ201901)
侯善策,博士生,主要從事農(nóng)業(yè)廢棄物處理裝備研究。Email:hou_shance@163.com
程紅勝,博士,高級工程師,主要從事農(nóng)業(yè)廢棄物資源化利用技術(shù)研究。Email:steerfeng@163.com
10.11975/j.issn.1002-6819.2020.14.029
S141.4;X705
A
1002-6819(2020)-14-0237-06