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Carrousel氧化溝的脫氮除磷工藝設(shè)計(jì)
摘要： 設(shè)置厭氧、缺氧段的Carrousel氧化溝(文中簡(jiǎn)稱：A2/C氧 化溝)具有生物脫氮除磷功能，是目前城市生活污水處理的主流工藝之一。結(jié)合工程實(shí)例，從工作原理、工藝設(shè)計(jì)等方面對(duì)A2/C氧化溝進(jìn)行了詳細(xì)介紹，可供從事污水處理工程設(shè)計(jì)的技術(shù)人員參考。
關(guān)鍵詞： 脫氮除磷 厭氧 缺氧 Carrousel氧化溝
中圖分類號(hào)：X703
文獻(xiàn)標(biāo)識(shí)碼：C
文章編號(hào)：1000-4602(2002)01-0067-04
在污水脫氮除磷的工藝設(shè)計(jì)中必須具備厭氧、缺氧、好氧3個(gè)基本條件，但是在實(shí)施過程中由于所需的處理構(gòu)筑物多、污泥回流量大，從而造成投資大、能耗多、運(yùn)行管理復(fù)雜。A2 /C氧化溝將厭氧、缺氧、好氧過程集中在一個(gè)池內(nèi)完成，各部分用隔墻分開自成體系，但彼此又有聯(lián)系。該工藝充分利用污水在氧化溝內(nèi)循環(huán)流動(dòng)的特性，把好氧區(qū)和缺氧區(qū)有機(jī)結(jié)合起來(lái)，實(shí)現(xiàn)無(wú)動(dòng)力回流，節(jié)省了去除硝酸鹽氮所需混合液回流的能量消耗。
1 工藝流程及設(shè)計(jì)
1.1 工藝流程
A2/C氧化溝的平面布置如圖1所示。
流經(jīng)沉砂池的生活污水與二沉池回流污泥在A2/C氧化溝內(nèi)設(shè)置的圓形混合井進(jìn)行充分混合后進(jìn)入?yún)捬鯀^(qū)Ⅰ。該區(qū)分為3格，每格都設(shè)有水下攪拌器 以防止污泥沉淀。經(jīng)厭氧反應(yīng)后的混合液進(jìn)入缺氧區(qū)Ⅱ，并與由氧化溝Ⅲ 經(jīng)回流 通道Ⅳ進(jìn)入缺氧區(qū)的回流液充分混合，進(jìn)行反硝化脫氮和除磷反應(yīng)。缺氧區(qū)Ⅱ的中間部位設(shè)導(dǎo)流隔墻，并在適當(dāng)位置安裝水下攪拌器，使該區(qū)具有良好的混合與循環(huán)條件。經(jīng)厭氧、缺氧反應(yīng)后的混合液流入氧化溝Ⅲ 進(jìn)行氧化、硝化、反硝化反應(yīng)，氧化溝Ⅲ的充氧機(jī)械采用倒傘形曝氣葉輪，可根據(jù)池內(nèi)DO測(cè)定儀控制調(diào)節(jié)堰出水、改變曝氣葉輪浸水深度以達(dá)到調(diào)節(jié)供氧的目的。處理后的水經(jīng)排出口Ⅴ進(jìn)入二沉池沉淀，其出水中氨氮含量＜15 mg/L，磷含量＜1.0 mg/L。如果要求出水磷含量＜0.5 mg/L，需在工藝流程的適當(dāng)位置投加混凝劑。
1.2 工藝設(shè)計(jì)
A2/C氧化溝主要由3部分組成，即厭氧區(qū)Ⅰ、缺氧區(qū)Ⅱ、 氧化溝區(qū)Ⅲ。其工作原理、計(jì)算方法、設(shè)計(jì)參數(shù)、容積大小等因素的確定是設(shè)計(jì)中要解決的主要問題。
1.2.1 厭氧區(qū)Ⅰ
在沒有溶解氧和硝態(tài)氮存在的厭氧條件下，兼性細(xì)菌將溶解性BOD轉(zhuǎn)化成低分子發(fā)酵產(chǎn)物，生物聚磷菌將優(yōu)先吸附這些低分子發(fā)酵產(chǎn)物，并將其運(yùn)送到細(xì)胞內(nèi)、同化成胞內(nèi)碳源存貯物，所需能量來(lái)源于聚磷的水解以及細(xì)胞內(nèi)糖的水解，并導(dǎo)致磷酸鹽的釋放。經(jīng)厭氧狀態(tài)釋放磷酸鹽的聚磷菌在好氧狀態(tài)下具有很強(qiáng)的吸磷能力，吸收、存貯超出生長(zhǎng)需求的磷量，并合成新的聚磷菌細(xì)胞、產(chǎn)生富磷污泥，通過剩余污泥的排放將磷從系統(tǒng)中除去。根據(jù)其工作原理，在A2/C氧化溝厭氧區(qū)Ⅰ的設(shè)計(jì)中分3格，第1 格的功能在于使混合液中的微生物利用進(jìn)水中的有機(jī)物去除回流污泥中的硝態(tài)氮，消除硝態(tài)氮對(duì)厭氧區(qū)的不利 影響，保證第2、3格中磷酸鹽的正常釋放。厭氧區(qū)Ⅰ的主要設(shè)計(jì)參數(shù)是混合 液停留時(shí)間。泥水混合液在厭氧區(qū)的停留時(shí)間一般為1～2 h(釋磷量就已達(dá)到可釋磷總量的80%左右)，過長(zhǎng)的厭氧停留時(shí)間可導(dǎo)致沒有低分子發(fā)酵產(chǎn)物的磷釋放，使得碳源貯存量不足，不能在好氧區(qū)產(chǎn)生足夠的能量來(lái)吸收所有釋放的磷。對(duì)一般城市生活污水(BOD /TP≥20～25 mg/L、出水磷濃度≤1.0 mg/L)，厭氧區(qū)的停留時(shí)間取1.5 h，據(jù)此可計(jì)算厭氧區(qū)的容積。
1.2.2 缺氧區(qū)Ⅱ
泥水混合液由厭氧區(qū)Ⅰ進(jìn)入缺氧區(qū)Ⅱ，一部分聚磷菌利用后續(xù)工藝的混合液(內(nèi)回流帶來(lái)的)中硝酸 鹽作為最終電子受體以分解細(xì)胞內(nèi)的PHB(聚β羥基丁酸)，產(chǎn)生的能量用于磷的吸收和聚磷的合成，同時(shí)反硝化菌利用內(nèi)回流帶來(lái)的硝酸鹽，以及污水中可生物降解的有機(jī)物進(jìn)行反硝化，達(dá)到部分脫碳與脫硝、除磷的目的。缺氧區(qū)容積包括脫硝、除磷兩部分。
a.除磷所需容 積：在缺氧條件下聚磷菌吸收磷的速度大于好氧區(qū)的速度，為充分利用這一有利條件，在缺氧區(qū)磷被吸收所需停留時(shí)間一般為0.5～1.0 h；b.脫硝所需容積：缺氧區(qū)反硝化菌利用污水中的有機(jī)物作反硝化碳源，但是其快速生物降解有機(jī)物在厭氧區(qū)已被利用，而在缺氧區(qū)所能 利用的大部分有機(jī)物只能是慢速生物降解有機(jī)物，因此其反硝化速率可參照后續(xù)氧化溝中所采用的數(shù)據(jù)。通過反硝化速率和確定的混合液MLVSS濃度及要去除的NO3-N量，可求得脫硝所需容積。
1.2.3 氧化溝區(qū)Ⅲ
氧化溝兼有推流型和完全混合型反應(yīng)池兩者的特性，完成一次循環(huán)所需時(shí)間約為5～20 min，而總的停留時(shí)間卻很長(zhǎng)。氧化溝中有好氧、缺氧交替出現(xiàn)的區(qū)域，具有硝化、生物除磷、反硝化的條件。在氧化溝好氧區(qū)聚磷菌除了吸收、利用污水中的可生物降解有機(jī)物外，主要是分解體內(nèi)貯積的PHB，產(chǎn)生的能量可供自身生長(zhǎng)繁殖，此外還可主動(dòng)吸收周圍環(huán)境中的溶解磷，并以聚磷的形式在體內(nèi)超量貯積。在剩余污泥中含有大量能超量聚磷的聚磷菌，大大提高了A2/C氧化溝系統(tǒng)的除磷效果。同時(shí)污水中的氨氮被亞硝酸菌、硝酸菌轉(zhuǎn)化為亞硝酸鹽和硝酸鹽，氧化1.0gNH4+-N為NO3-N共耗氧4.57 g，消耗堿度為7.14 g(以CaCO3 計(jì))。在缺氧區(qū)反硝化菌利用亞硝酸鹽和硝酸鹽中的N3+和N5+(被還原為N2) 作為能量代謝中的電子受體，O2-作為受氫體生成H2O和OH-堿度，有機(jī)物作為碳源及電子供體提供能量并得到氧化穩(wěn)定。將1.0gNO2-N轉(zhuǎn)化為N2時(shí)消耗有機(jī)物(以BOD計(jì))1.71 g，將1.0gNO3-N轉(zhuǎn)化為N2時(shí)消耗有機(jī)物(以BOD計(jì))2.86 g，與此同時(shí)產(chǎn)生3.57 g堿度(以CaCO3計(jì))。氧化溝區(qū)Ⅲ的容積由好氧區(qū)和缺氧區(qū)組成，通過計(jì)算好氧區(qū)有機(jī)物的去除速率q0和缺氧區(qū)的反硝化速率q1，并根據(jù)已確定的MLVSS濃度可求得好氧和缺氧區(qū)所需容積。
?、?好氧區(qū)有機(jī)物去除速率q0的確定
q0=(μ+k)/y (1)
式中 q0——有機(jī)物去除速率，kgBOD5/(kgVSS·d)
μ——硝化菌比增長(zhǎng)率，d-1，μ=1/θ，θ為污泥齡，d
k——異養(yǎng)微生物內(nèi)源衰減系數(shù)，一般取0.05d-1
y——異養(yǎng)微生物的產(chǎn)率系數(shù)，一般取0.6kgVSS/kgBOD5
?、?缺氧區(qū)反硝化速率q1的確定
q1=μ1/y1 (2)
式中 q1——反硝化速率，一般取0.02 kgNO3-N/kgVSS·d
μ1——脫硝菌的生長(zhǎng)率，d-1
y1——脫硝菌的產(chǎn)率系數(shù)，kgVSS/kgNO3-N
2 設(shè)計(jì)實(shí)例
某城市生活污水量Q=15 000m3/d，原水COD=300 mg/L、BOD5=150 mg/L、SS=200 mg/L、TKN=30 mg/L、TP=4.0 mg/L、pH=7～9；設(shè)計(jì)出水水質(zhì)為COD=60 mg/L、BOD5=20 mg/L、SS=20 mg/L、NH+4-N≤5.0 mg/ L、NO3-N≤10.0 mg/L、TP≤1.0 mg/L。
2.1 氧化溝區(qū)Ⅲ容積的確定
?、?好氧區(qū)容積
V1=好氧區(qū)需要的污泥量/混合液濃度
硝化菌的比增長(zhǎng)速率可用下式計(jì)算：
μ=0.47 e0.098(T-15)×［N/(N+100.051T-1.158)］×［DO/(K0+DO)］ (3)
當(dāng)最低溫度T=15 ℃、出水NH3-N=5.0 mg/L、DO=2.0 mg/L、K0=1.3時(shí)，μ=0.28d-1，θ=1/μ=3.6 d，安全系數(shù)取2.5，則設(shè)計(jì)污泥齡為9 .0 d。為保證污泥穩(wěn)定，確定污泥齡為25 d，μ=0.04d-1。
好氧區(qū)有機(jī)物的去除速率
q0=(μ+k)/y=0.15 kgBOD5/(kgVSS·d)
通過計(jì)算，則MLSS=4.0kg/m3，MLVSS=2.8kg/m3，好氧區(qū)需要的污泥量 為13 000 kg，好氧區(qū)的容積V1=4 643m3，水力停留時(shí)間t=V1/Q =7.4 h。
?、?缺氧區(qū)容積
V2=脫硝需要的污泥量/混合液濃度
假設(shè)生物污泥含12.4%的氮，則每日用于生物合成的N合=每日產(chǎn)生的污泥量×12.4%，而污泥產(chǎn)量=y×Q×ΔBOD5/(1+kθ)=585 kg/d，則N合=72.54 kg/d，進(jìn)水中用于生物合成的氮為4.8mg/L、被氧化的NH+4-N=30-4.8-5.0=20.2 mg/L。
脫硝所需NO3-N=20.2-10.0=10.2 mg/L；在15 ℃時(shí)反硝化速率q1=0.02×10-5=0.013 6kgNO3-N/(kgVSS·d)，需還原的NO3-N=10.2×0.8×(15 000×10-3)=122.4 kg/d，脫硝所需MLVSS=122.4/0.0136=9000 kg。
通過計(jì)算，缺氧區(qū)容積V2=3 214m3，氧化溝區(qū)Ⅲ容積=V1+V2=7857m3，水力停留時(shí)間t1
=12.57 h。
2.2 缺氧區(qū)Ⅱ容積的確定
① 除磷所需容積V3：若缺氧區(qū)水力停留時(shí)間取40 min，則V3=417m3。
② 脫硝所需容積V4：若需還原的NO3-N=30.6 kg/d，脫硝所需的MLVSS=2250kg，則V4=804m3，缺氧區(qū)Ⅱ容積=V3+V4=1221 m3，水力停留時(shí)間t2=1.95 h。
2.3 厭氧區(qū)Ⅰ容積的確定
生物除磷系統(tǒng)的厭氧區(qū)水力停留時(shí)間取1.5 h，所需容積V5=150000×1.5/24=938m3。
2.4 污泥回流比的確定
① 外回流比R
假設(shè)二沉池排放污泥濃度XR=8 000 mg/L，A2/C氧化溝混合液濃度X=4000 mg/L，則R=X/(XR-X)=100%。
② 內(nèi)回流比r
由氧化溝Ⅳ的通道回流到缺氧區(qū)Ⅱ的回流量為Qr，通道寬度為1.0m、水深為4.0m、流速為0.3 m/s，則Qr=1.2m3/s，最大回流比 r=(1.2×86 400/15 000)×100%=691%，內(nèi)回流量可以通過安裝在回流通道上的閘板控制。
通過上述計(jì)算可知，A2/C氧化溝總?cè)莘e為10 016m3，水力停留時(shí)間為16 h，混合液濃度為4 000 mg/L，污泥負(fù)荷為0.05kgBOD5/(kgMLSS·d)，污泥齡為25d。污泥外回流比R=100%，混合液內(nèi)回流比r=400%～600%。
3 結(jié)語(yǔ)
① A2/C氧化溝利用溝內(nèi)的水力循環(huán)、無(wú)動(dòng)力回流等特點(diǎn)，實(shí)現(xiàn)了類似于A2/O工藝，以達(dá)到脫氮除磷的目的。一般城市生活污水若采用A2/C氧化溝處理，可使出水磷濃度＜1.0 mg/L，其他指標(biāo)可達(dá)到GB 8978—1996的一級(jí)排放標(biāo)準(zhǔn)。
?、?主要設(shè)計(jì)參數(shù)的確定如下：
a.厭氧區(qū)容積一般按1.0～2.0 h的水力停留時(shí)間確定。
b.缺氧區(qū)容積包括脫硝和除磷兩部分，除磷所需容積一般按0.5～1.0 h水力停留時(shí)間確定，脫硝量可按總脫硝量的15%～20%計(jì)算，反硝化速率計(jì)算可采用后續(xù)好氧區(qū)的數(shù)據(jù)以確定脫硝所需容積。
c.氧化溝區(qū)Ⅲ容積包括氧化、硝化、反硝化所需容積。好氧區(qū)有機(jī)物去除速率可用公式
q0=(μ+k)/y計(jì)算，反硝化區(qū)的脫硝速率可用公式q1= μ1/y1計(jì)算。
d.A2/C氧化溝混合液的濃度一般取3000～4 000 mg/L，污泥負(fù)荷為0.05～0.08kgBOD5/(kgMLSS·d)，污泥齡為15～30d。
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天津市某污水處理廠設(shè)計(jì)的技術(shù)要點(diǎn)
摘要： 天津市某污水處理廠設(shè)計(jì)的技術(shù)要點(diǎn)
關(guān)鍵詞： 污水處理廠 處理廠設(shè)計(jì) 技術(shù)要點(diǎn)
建設(shè)某污水處理廠是海河流域天津污水治理項(xiàng)目的重點(diǎn)工程.對(duì)于改善天津市西部地區(qū)和大沽口渤海海域的環(huán)境質(zhì)量，對(duì)于開發(fā)利用污水資源，促進(jìn)工、農(nóng)、漁業(yè)的健康發(fā)展，具有重要作用，將會(huì)產(chǎn)生顯著的社會(huì)效益和經(jīng)濟(jì)效益。
工程的內(nèi)容包括廠內(nèi)和廠外兩部分。廠內(nèi)工程的主體是規(guī)模為45萬(wàn)T/d的二級(jí)污水處理廠，配套一座720m3/d的污泥填埋廠；廠外工程包括雨污水管道21km和兩座2.0T/S的污水泵站。工程估算12億人民幣，部分建設(shè)資金利用日本政府貸款。
進(jìn)水水質(zhì)指標(biāo)，根據(jù)多年監(jiān)測(cè)資料綜合分析定為：
CODCr：400mg/l
BOD5:220mg/l
SS:220mg/l
NH3-N:40mg/l
TP:3.5mg/l
出水水質(zhì)標(biāo)準(zhǔn)，根據(jù)出水滿足農(nóng)灌水質(zhì)指標(biāo)和排入渤?？谶_(dá)到三類海域的要求，執(zhí)行國(guó)標(biāo)〈污水綜合排放標(biāo)準(zhǔn)〉中二級(jí)水質(zhì)的規(guī)定。即：
CODCr：120mg/l
BOD5:30mg/l
SS:30mg/l
NH3-N:25mg/l
磷酸鹽（以P計(jì)）:1mg/l
1 污水處理工藝方案的選擇
目前城市污水生化處理技術(shù)發(fā)展很快，工藝類型較多。除廣泛采用的傳統(tǒng)活性污泥法外，近年來(lái)國(guó)內(nèi)外應(yīng)用較多的有氧化溝法、A/A/O法、A/O法、A-B法、SBR法等。為了使某污水處理廠能夠選擇到最合適的處理工藝，按照因地制宜的原則，先排除不適用的處理工藝后，再對(duì)可以采取的處理工藝方案進(jìn)行對(duì)比和優(yōu)選。。
某污水處理廠具有處理規(guī)模大，地處天津市西郊區(qū)冬季氣溫低，且收水范圍是已建成區(qū)，水量和水質(zhì)比較穩(wěn)定，沖擊負(fù)荷不大的特點(diǎn)，按照各種處理工藝的適用條件，可以將SBR法、氧化溝法和A-B法排除，從而擬定出三個(gè)處理工藝方案。
第一方案：采用“以傳統(tǒng)活性污泥法為基礎(chǔ)的生物硝化方法，降解有機(jī)物和NH3-N，同時(shí)采用以化學(xué)法除磷”的綜合處理工藝方案，簡(jiǎn)稱“傳統(tǒng)法”或“生物硝化法”。
生物硝化的工藝流程與傳統(tǒng)活性污泥工藝流程一樣，只是以去除BOD5為主的傳統(tǒng)活性污泥工藝是中等負(fù)荷，而生物硝化工藝系低負(fù)荷或超低負(fù)荷。在曝氣池內(nèi)，BOD5被分解轉(zhuǎn)化，有機(jī)氮同時(shí)被氨化成NH3-N，再與進(jìn)水原有的NH3-N一起被硝化成NO3-N。
同步的化學(xué)沉淀法除磷，是在含磷污水中投加溶解度大、渣物少、易于控制的硫酸鐵作為混凝劑，使正磷酸鹽被置換成難溶的磷酸鐵鹽，沉淀后隨剩余污泥排出，反應(yīng)方程如下：
Fe(SO4)3+2PO3-4→2FePO4↓+3SO42-
化學(xué)法除磷運(yùn)轉(zhuǎn)控制靈活，可根據(jù)污水中磷的超標(biāo)程度隨時(shí)調(diào)整鐵鹽投加量，從而既保證出水中磷的含量達(dá)標(biāo)也能節(jié)約污水廠運(yùn)行成本。工程中一般按去除lg磷投加12g硫酸鐵控制。
第二方案：生物除磷脫氮工藝（A2/O工藝）
以厭氧/缺氧/好氧即A/A/O系統(tǒng)為特征的生物除磷脫氮工藝。其中除磷是通過磷的厭氧釋放和好氧吸附兩個(gè)過程完成的，脫氮是通過好氧硝化和缺氧反硝化兩個(gè)過程完成的，有機(jī)物的降解是在好氧曝氣階段完成的。
A/A/O工藝具有處理效率高，污泥沉降性能好，可以不設(shè)沉淀池和污泥消化池等優(yōu)點(diǎn)。
第三方案；"A/O生物法除磷、生物硝化法脫氨、化學(xué)法降解濾液與上清液余磷"的處理工藝，簡(jiǎn)稱A/O法。
表1 三個(gè)方案主要設(shè)計(jì)參數(shù)對(duì)照表
參數(shù)
方案
第一方案
第二方案
第三方案
污泥負(fù)荷（kgBOD/kgMLSS.d）
0.14
0.105
0.18
泥齡(d)
12
28
10
回流比
75%
100%(內(nèi)回流比300%)
75%
水力停留時(shí)間(h)
6.6
14
7.5
MLSS(mg/L )
3.0
4.0
3.0
以上三種工藝方案均能滿足處理達(dá)標(biāo)的要求，都是可靠的。剖析三種方案的機(jī)理，有機(jī)物的降解都是在好氧曝氣階段完成。污染因子氮的降解，在第一和第三方案中是通過生物硝化反應(yīng)，利用它能自養(yǎng)微生物將污水中氨氮氧化成硝酸鹽的過程。在天津東郊污水處理廠已經(jīng)多次試驗(yàn)證明，在曝氣池中只要污泥負(fù)荷降到0.2kg BOD/kg MLSS.D以下，曝氣時(shí)間延長(zhǎng)到4.5h以上，有機(jī)氮和氨氮氧成化NO3-N的效率可以達(dá)到50%～60%以上；第二方案則是在硝化作用的基礎(chǔ)上增加了反硝化的生化過程，利用缺氧池將硝態(tài)氮還原成氮?dú)庖绯觯沟蒙锩摰磻?yīng)進(jìn)行得更加徹底；另一個(gè)污染因子磷的去除，在第一方案是采用化學(xué)法，利用投加硫酸鐵等混凝劑，將污水中正磷酸鹽置換成難溶解的磷酸鐵，隨即在二沉池通過剩余污泥排除；而第二和第三方案則是以生物法為主，設(shè)置厭氧池，先使混合液中的聚磷菌處于壓抑狀態(tài)，釋放細(xì)胞內(nèi)的聚磷而蓄存能量，再在后續(xù)的好氧池中通過聚磷菌貯存的能量大量吸收污水中的磷，并在細(xì)胞內(nèi)將磷轉(zhuǎn)化為聚磷酸鹽，最后以剩余污泥的形式從污水中排出，從而完成除磷過程。在污泥處理過程中產(chǎn)生的含磷濾液與上清液則通過化學(xué)法進(jìn)行再處理。
脫氮工藝的選擇是只依靠硝化作用還是后加反硝化作用來(lái)完成，除磷工藝的選擇是依靠化學(xué)法還是生物法來(lái)完成，兩者各有利弊。根據(jù)天津市已建污水處理廠的運(yùn)行經(jīng)驗(yàn)，必須把降低運(yùn)行管理費(fèi)用作為污水處理方案選擇的主要因素，因此推薦第三方案。采用生物硝化脫氮，既可以不設(shè)缺氧池，減少占地和工程造價(jià)，又能節(jié)省提升回流液的設(shè)備和能耗，出水也能達(dá)標(biāo)；采用以生物法為主除磷，可以節(jié)省能源，節(jié)省投藥量，減少運(yùn)行費(fèi)用。在投產(chǎn)以后，還應(yīng)該根據(jù)不同情況及時(shí)調(diào)整運(yùn)行工況，如出水用于農(nóng)灌時(shí)，對(duì)氮磷的指標(biāo)可以放寬，有進(jìn)一步降低運(yùn)行成本的余地。第三方案污水處理流程如下圖。
2 污泥處理和處置工藝方案的選擇
污水處理過程中產(chǎn)生的大量活性污泥必須通過適當(dāng)?shù)墓に嚧胧档推溆袡C(jī)物含量及含水率，減少污泥體積，同時(shí)殺滅大部分致病菌和寄生蟲卵，達(dá)到化學(xué)性質(zhì)穩(wěn)定和衛(wèi)生防疫無(wú)害化，避免形成二次污染，保證污水處理廠的正常運(yùn)行。污泥處理方案流程如下圖。
污水處理廠建成投入正常運(yùn)行后，每天要產(chǎn)生相當(dāng)數(shù)量的剩余污泥，從目前東郊和紀(jì)莊子污水處理廠的情況看，傳統(tǒng)的用作農(nóng)肥的處置方法，已無(wú)可靠出路，所以污泥的最終處置也成為國(guó)內(nèi)多數(shù)污水處理廠的重大難題。處置是否妥當(dāng)直接關(guān)系污水處理廠能否生存的問題。矛盾相當(dāng)突出。綜合國(guó)內(nèi)外情況，采用污泥填埋手段處置市政污泥，在國(guó)外已得到較為廣泛的應(yīng)用，但在我國(guó)還沒有起步。設(shè)計(jì)中經(jīng)過對(duì)污泥處置的各種方案，包括堆肥、焚燒、填埋進(jìn)行反復(fù)比較后，決定了采取衛(wèi)生填埋的方案，填補(bǔ)國(guó)內(nèi)空白。為此隨某污水處理廠工程同時(shí)建設(shè)市政污泥填埋廠一座，日處理規(guī)模720T，計(jì)劃連同擴(kuò)建后的紀(jì)莊子污水處理廠及擬建的北倉(cāng)污水處理廠的污泥一并在此進(jìn)行填埋處置。
3 工藝處理設(shè)計(jì)的技術(shù)措施
為了使某污水處理廠建成后能具有二十世紀(jì)現(xiàn)代化的水平達(dá)到國(guó)內(nèi)一流，國(guó)際先進(jìn)的標(biāo)準(zhǔn)。除了精心設(shè)計(jì)，精心施工，精心管理外，還要在設(shè)計(jì)中采取一系列先進(jìn)技術(shù)措施。
1、進(jìn)水泵房及回流污泥泵房，采用變速拖動(dòng)技術(shù)，既能適應(yīng)進(jìn)廠污水量和回流污泥量不時(shí)變化的特定條件，保持前池水位的穩(wěn)定，同時(shí)水泵維持在最高效率區(qū)工作，實(shí)現(xiàn)最大限度的節(jié)能運(yùn)行。
2、沉砂池在總結(jié)天津東郊和紀(jì)莊子兩座污水處理廠現(xiàn)有沉砂池使用經(jīng)驗(yàn)的基礎(chǔ)上，某采用了具有簡(jiǎn)單、可靠、管理方便的旋流沉砂池。通過自動(dòng)沉砂、吹砂、洗砂、提砂、輸砂以達(dá)到既能高效率除砂，同時(shí)也能夠徹底分離砂粒上的有機(jī)物送至后續(xù)處理的效果。但是如此大型處理廠采用旋流沉砂的方法，國(guó)內(nèi)沒有先例。經(jīng)過精心設(shè)計(jì)，將六旋流沉砂池精巧緊湊地布置成梅花形：配水井置于中央，保證進(jìn)出水順暢、配水均勻。
3、為了保證厭氧/好氧工藝的除磷效果，吸收國(guó)外先進(jìn)經(jīng)驗(yàn)采取了活性污泥分段回流的嶄新工藝。即：約25～30%回流污泥可回流到厭氧池，以保持池內(nèi)理想的厭氧工況，提高除磷效果，其余回流污泥回流到曝氣池，同時(shí)提高生物硝化處理效果。目前這種工藝在國(guó)內(nèi)還只處在起步階段。
4、由于市政污水的水量和水質(zhì)具有不穩(wěn)定的特點(diǎn)，設(shè)計(jì)的處理工藝流程也具有相應(yīng)的可調(diào)整性，以便同來(lái)水的變化相適應(yīng)。當(dāng)來(lái)水有機(jī)物指標(biāo)偏低時(shí)，為保證除磷脫氮效果可以超越初沉池；當(dāng)初期雨水量偏大時(shí)，部分來(lái)水可以超越二級(jí)處理設(shè)施；當(dāng)受納污水河道在枯水季節(jié)時(shí)，可以超越二級(jí)泵房自流排出廠外。
5、由于天津市是嚴(yán)重缺水的城市，污水回用勢(shì)在必行。廠內(nèi)經(jīng)二級(jí)處理的出水，除大量用于農(nóng)業(yè)灌溉外，還設(shè)置規(guī)模2萬(wàn)T/d的深度處理設(shè)施，計(jì)劃采用先進(jìn)的流動(dòng)性砂過濾器，達(dá)到市政雜用水以上的標(biāo)準(zhǔn)，為市政和工業(yè)用水提供水源。
6、隨著某污水處理廠工程的建設(shè)，將建成國(guó)內(nèi)第一座市政污泥填埋場(chǎng)。污泥填埋的操作需要在實(shí)踐中逐步規(guī)范化。目前已經(jīng)注意到污泥填埋技術(shù)的關(guān)鍵是保證污泥有足夠的含固率。根據(jù)國(guó)外資料介紹污泥含固率必須在30%以上、有機(jī)成份應(yīng)該盡量降低、污泥抗剪強(qiáng)度應(yīng)≥25KN/m2才適合于填埋。所以填埋的污泥需要經(jīng)過良好的污泥消化，使用高干度的機(jī)械脫水，必要時(shí)還得添加石灰進(jìn)行衛(wèi)生處理。為了保證污泥填埋場(chǎng)能夠正常工作，先期將進(jìn)行試驗(yàn)研究。
7、為了探討采用填埋以外的其他辦法處置污泥，也為了延長(zhǎng)污泥填埋場(chǎng)的使用年限，并且給污泥資源化奠定基礎(chǔ)，將對(duì)100T/d的污泥采用干燥方法處置，將經(jīng)過消化、機(jī)械脫水后的污泥在多重盤式干燥爐中干化后，使含固率達(dá)90%以上，可以用作裝袋的高級(jí)農(nóng)肥，
也可以作為建筑材料的輔料利用。
8、充分利用消化池產(chǎn)生的沼氣能源，配置閉路的沼氣攪拌、沼氣鍋爐、污泥熱交換器和沼氣驅(qū)動(dòng)鼓風(fēng)機(jī)。使沼氣能源的綜合利用率達(dá)80%以上。根據(jù)沼氣發(fā)電時(shí)能源利用回收率低、發(fā)電并網(wǎng)困難的經(jīng)驗(yàn)，暫不采取沼氣發(fā)電的方法。
9、各主要的處理單元作到準(zhǔn)確、可靠的閉路自控。包括沉砂池與砂水分離機(jī)自動(dòng)按程序操作；鼓風(fēng)機(jī)根據(jù)各曝氣池內(nèi)工況變化、自動(dòng)調(diào)節(jié)供風(fēng)量，保證曝氣池穩(wěn)定的溶解氧值。以及消化池的污泥攪拌、加熱系統(tǒng)的全自動(dòng)控制。
10、中央控制室采用模擬屏和投影儀相配合的顯視設(shè)備，達(dá)到靜態(tài)與動(dòng)態(tài)的有機(jī)結(jié)合；自動(dòng)控制系統(tǒng)采用總線型拓樸結(jié)構(gòu)，提高布線和擴(kuò)展的靈活性。
11、污水處理設(shè)備的選型是污水處理廠能否實(shí)現(xiàn)科學(xué)經(jīng)濟(jì)運(yùn)行的關(guān)鍵問題，也是污水處理廠技術(shù)水平是否先進(jìn)的重要標(biāo)誌。設(shè)備選型將遵循"先國(guó)內(nèi)，后國(guó)外"的要求。將進(jìn)口設(shè)備壓縮到最低限度。但是處理廠的關(guān)鍵設(shè)備，國(guó)內(nèi)制造技術(shù)尚不過關(guān)的設(shè)備必須進(jìn)口。進(jìn)口設(shè)備選擇的原則是用超前的標(biāo)準(zhǔn)，精心挑選具有技術(shù)含量高、有創(chuàng)造性、有特點(diǎn)、并且在使用中證明效果可靠的，屬于世界一流水平的設(shè)備，再通過競(jìng)標(biāo)決定。一定要把住技術(shù)關(guān)，為污水處理廠建成投產(chǎn)后保持國(guó)內(nèi)前沿水平奠定基礎(chǔ)。初步擬定進(jìn)口設(shè)備包括：泵、鼓風(fēng)機(jī)、細(xì)格柵、旋流沉砂機(jī)、曝氣器、污水回用、污泥消化、沼氣利用、污泥干化及儀表自控等方面的設(shè)備。個(gè)別設(shè)備也將采取引進(jìn)國(guó)外先進(jìn)技和主機(jī)，在國(guó)完成配套的方法，如刮泥機(jī)等。
目前廠內(nèi)外工程已全面開始進(jìn)行施工前的準(zhǔn)備工作，預(yù)計(jì)2004年建成投產(chǎn)。
筑龍網(wǎng)給排水所有資料全都免費(fèi)
Oxidize the ditch craft in dirty water handle of application and development
Summary: This text expatiated primarily the Carrousel oxidizes the construction, craft mechanism of the ditch and circulate the problem exsited in the process with the homologous the method of solution.Finally, introduce the Carrousel oxidize the latest research progress of the ditch and pointed out the future and main research direction.
Key phrase: The Carrousel oxidizes the ditch divideds by the phosphor takes off the nitrogen construction mechanism
Application and Development of Carrousel Oxidation Ditch Process on Wastewater Treatment
Abstract: The structure and the techniques of carrousel oxidation ditch process on nitrogen and phosphor removal are introduced in this paper. The problems inrunning and their corresponding resolvent are also pointed. At last, The authorshowed the up to date research improvement and the mainly future research dire-ction.
Key words: Carrousel; oxidation ditch; nitrogen and phosphor removal; structure;techniques
1. Foreword
Oxidize the ditch( oxidation ditch) again a continuous circulation spirit pond( Continuous loop reactor), is a live and dirty mire method a kind of to transform.Oxidizing the dirty water in ditch handles the craft be researched to manufacture by the hygiene engineering graduate school of Holland in the 50's of 20 centuries success.Since in 1954 at Dutch throw in the usage for the very first time.Because its a water fluid matter good, circulate the stability and manage convenience etc. technique characteristics, already at domestic and
international and extensive application in live the dirty water to is dirty to manage aqueously with the industry[1].
Current application than oxidize extensively the ditch type include:The ( Pasveer) oxidizes the ditch, the ( Carrousel) oxidizes the ditch, ( Orbal) oxidizes the ditch, the type of T oxidizes the ditch( three ditch types oxidize the ditch), the type of DE oxidizes the ditch to turn to oxidize the ditch with the integral whole.These oxidize the ditch because of the difference of esse in construction with circulating, therefore each characteristics[2].This text will introduce construction, mechanism, existent problem and its latest developments that Carrousel oxidize ditches primarily.
2. The Carrousel oxidizes the construction of the ditch
The Carrousel oxidize the ditch to be researched to manufacture by Dutch DHV company development in 1967.Oxidize the last the company of DHV in foundation of the ditch in the original Carrousel to permited specially the company EIMCO to invent again with its patent in the United States Carrousel 2000 system( see the figure ), realizes the living creature of the higher request takes off the nitrogen with divided by the function of .There has been in the world up to now more than 850 Carrousels oxidize the ditch with the Carrousel 2000 system are circulating[3].
From diagram therefore, the Carrousel oxidizes the ditch the usage the spirit of that definite direction control with shake up the device, face to mix with the liquid deliver the level speed, from but make drive the liquid of admixture that shake up is in oxidize ditch shut match outlet circulate flow.Therefore oxidize the ditch have the special hydraulics flows the , current complete mix with the characteristics of the type reactor, have the characteristics that push the flow type reactor again, the ditch inside exsits obviously of deliquescence oxygen density steps degree.Oxidizing the ditch cross
section is rectangle or trapezoids, the flat surface shape is many for oval, the ditch internal water is deep general for 2.5 ～ 4.5 ｍ , the breadth is deep compare for 2:1, also have the deep water amount to 7 ms of, ditch inside average speed in water current is 0.3 ms/ s.Oxidize ditch spirit admixture equipments contain surface spirit machine, the spirit of turn to brush or turn the dish and shoot to flow the spirit machine, pipe type spirit machine with promote take care of type spirit machine etc., match with in recent years usage still contain underwater push machine[4~6].
3. The Carrousel oxidizes the mechanism of the ditch
3.1 The Carrousel oxidizes the ditch handles dirty and aqueous principle
The at the beginning common Carrousel oxidizes the dirty water in inside in craft of the ditch direct with dirty mire in reflux together enter oxidize the ditch system.The surface spirit machine makes fuse in the liquid of admixture the density of the oxygen DO increases about 2 the 3 mgs/ L.Under this kind of well the term of the oxygen , the microorganism gets the enough deliquescence oxygen comes and go to divided by the BOD;At the same time, the ammonia were too oxidized nitrate with second nitrate, this time, mix with the liquid be placed in the oxygen appearance.In the spirit machine downstream, after water current be become by the swift flow appearance of the spirit District of even flow the appearance, the water current maintains in the minimum current velocity, guaranteeing the live and dirty mire be placed in the floats the appearance.( average current velocity>0.3 ms/ s)Oxidize microbially the process consumed to fuse the oxygen in the water, until the value of DO declines for zero, mixing with the liquid report the anoxia appearance.Versa nitric that turn the function through anoxia area, mix with the liquid enter to have the oxygen area, completing once circulating.That system inside, the
BOD declines the solution is a continuous process, the nitric turns the function to turn with the versa nitric the function take place in same pond.Because of structural restrict, this kind of oxidize the ditch although can then valid whereabouts BOD, divided by the phosphorus take off the nitrogenous ability limited[7].
For the sake of the acquisition better divided by the phosphorus take off the nitrogenous result, Carrousel 2000 systems increased a oxygen District before common Carrousel oxidize ditch with the unique oxygen area.( call again that the versa nitric in front turns the area)The dirty mire in all refluxes enters the anaerobic District with 10-30% dirty water, can under the anoxia with 10-30% carbon source term complete remaining of dirty mire in reflux inside nitric acid nitrogen to versa nitric to turn, creates for the unique oxygen pond of hereafter unique oxygen term.At the same time, anaerobic District inside of concurrently the sex germs convert the dissolubility BOD VFA, the germ acquire the VFA its assimilation PHB, the energy source needed solves in the phosphoric water and cause phosphatic releasing.The anaerobic District a water enters the inner part installs the unique oxygen area that have the mixer, the so-called unique oxygen is a pond inside to mix with liquid since have no the numerator oxygen, also have no the compound oxygen( nitric acid root), the here unique oxygen environment is next,70-90% dirty water can provide the enough carbon source, can make the germ of released the phosphorus well.The unique oxygen area connects behind the common Carrousel oxidizes the ditch system, further completing to do away with the BOD and take off the nitrogen with divided by the phosphorus .Finally, mix with the liquid transfer the dirty mire inside in oxidize ditch enrich oxygen area eject, while enriching the oxygen environment germ surfeit, phosphorus from the water, ejecting the system with the dirty mire in surplus.Like this, in Carrousel 2000
systems, than completed to do away with the BOD, COD with take off at the same time goodly the nitrogen divided by the phosphorus .
Synthesizing and dirty water in the river City , long sand City decontamination center[s of the dirty the factory of water in the first in Kunming of adoption that crafts handles the movement result of the factory therefore:Through Carrousel 2000 system after handling, the BOD, COD, SS does away with the rate to all come to a 90% above, the TN does away with the rate comes to a 80%, the TP does away with the rate to also come to a 90%.
3.2 The Carrousel oxidizes the ditch divideds by the phosphorus takes off the nitrogenous influence factor.
Affecting the Carrousel oxidizes the ditch divideds by the phosphoric factor is dirty mire , nitrate density and quality densities primarily.The research expresses, being total and dirty mire as 11% that a hour biggest phosphorus 4% with deal is its fuck dirty mire deal within live and dirty mire, keep for the the germ physical endowment measures, but when dirty mire over 15 d hour dirty mire the inside is biggest to contain the obvious descent in deal in phosphorus , canning not reach the biggest divideding by the result of phosphorus on the contrary.Therefore, prolong persistently the dirty mire ( for example 20ds,25ds,30ds) is to have no necessary, proper choose to use within the scope of 8~15 d.At the same time, high nitrate density with low quality density disadvantage in divided by the process of phosphorus .
Affecting the Carrousel oxidizes the ditch takes off the nitrogenous and main factor is DO, nitrate density and carbon source densities.The research expresses, oxidizing the ditch inside exsits deliquescence oxygen density steps degree namely the good oxygen area DO attains 3~3.5 mgs/ L, the anoxia area DO attains 0~0.5 mgs/ L is a prior condition to take place nitric turn reaction and versa nitrics
turn the reaction.At the same time, ample carbon source and higher C/ the N ratio benefits to take off to complete nitrogenously[7].
4. The Carrousel oxidizes problem and solution methods of the ditch esse.
Though the Carrousel oxidizes the ditch has a water fluid matter good, the anti- pounds at the burthen ability strong, divided by the phosphorus take off the nitrogen efficiency. But, in physically of movement process, still exsits a series of problem.
4.1 Dirty mire inflation problem
When discard the aquatic carbohydrate more, the N, P contains the unbalance of deal, the pH value is low, oxidizing the dirty mire in inside in ditch carries high, fuse the oxygen density the shortage, line up the mire not etc. causes easily dirty mire in germ in form in silk inflation;Not the dirty mire in germ in form in silk inflation takes place primarily at the waste water water temperature is lower but the dirty mire carries higher hour.The microbial burthen is high, the germs absorbed the large quantity nourishment material, is low because of the temperature, metabolism the speed is slower, accumulating the rises large quantity is high to glue sexual and many sugar materials, making the surface of the live and dirty mire adhere to the water to increase consumedly, SVI the value is very high, becoming the dirty mire inflation.
Cause that aim at the dirty mire inflation, can adopt the different counterplan:From the anoxia, water temperature high result in of, can enlargement tolerance or lower into the water measures to alleviate burthen, or the adequacy lowers the MLSS( control dirty mire reflux measure), making need the oxygen measures decrease;If the dirty mire carries high, can increase MLSS, to adjust the burthen, necessity the hour can stop into the water, stuffy a period of time;Can pass the hurl add the nitrogen fertilizer, phosphorus fatty, adjust the admixture
nourishment in the liquid material equilibrium( BOD5:N:P=100:5:1);The value of pH over low, can throw to add the lime regulate;Bleach the powder with the liquid chlorin( press to fuck 0.3% of the dirty mire~0.6% the hurl adds), can repress the silk form germ breed, controling the dirty mire in combinative water inflation[11].
4.2 Foam problem
Because entering to take the grease of large quantity in the water, handling system can't completely and availably its obviation, parts of greases enriches to gather in in the dirty mire, through turn to brush the oxygen agitation, creation large quantity foam;The mire is partial to long, the dirty mire is aging, and also easy creation foam.Spray to pour the water or divided by with the surface the of do away with the foam, in common use divided by the an organism oil, kerosene, the oil of silicon, throw deal as 0.5~1.5 mgs/ L.Pass to increase dirty mire in pond in spirit in density or adequacies let up the tolerance of , also can control the foam creation effectively.When contain the live material in surface in the waste water more, separate with the foam easily and in advance method or other methods do away with.Also can consider to increase to establish a set of divideding by the oil device moreover.But enhance most importantly the headwaters manage, reducing to contain the oil over the high waste water and other poisonous waste water of into[12].
4.3 Float the problem on the dirty mire
When contain in the waste water the oil measures big, whole system mire quality become light, can't like to control very much in operate process its at two sink the pond stop over time, resulting in the anoxia easily, producing the corrupt and dirty mire ascend to float;When spirit time over long, take place in pond the high degree nitric turn the function, making nitrate density high, at two sink the
versa nitric in easy occurrence in pond turn the function, creation nitrogen spirit, make dirty mire ascend float;Moreover, contain the oil in the waste water?
Take place the dirty mire ascend after floating should pause enter water, broke off or dirty mire in clearance, judge the clear reason, adjust the operation.The dirty mire sinks to decline the sex bad, can throw to add of oagulate or sloth materials, the improvement precipitates the sex;Such as enter the water carries big let up into the water measures or the enlargement reflux measures;Such as the dirty mire grain small lower the spirit machine turn soon;If discovers versa nitric turning, should let up the tolerance , enlarge the reflux or row the mire measures;If discover the dirty mire is corrupt, should enlargement tolerance, the clearance accumulates the mire, and try the ameliorative pond internal water dint term[12].
4.4 Current velocity is not all and the dirty mire sinks to accumulate the problem
In Carrousel oxidize ditch, for acquiring its special admixture with handles result, mix with liquid must with certain current velocity is in ditch circulate flow.Think generally, the lowest current velocity should should attain for an average current velocity for, doing not take place sinking accumulating 0.3~0.5 ms/ s.The spirit equipments that oxidize the ditch is general to turn to brush for the spirit of to turn the dish with the spirit of , turning to brush of immerse to have no depth for 250~300 mms, turn the dish immerse to have no depth for 480~530 mms.With oxidize the ditch water the deep(3.0~3.6 ms) comparing, turn to brush occupied the deep 1/10~ in water 1/12, turned the dish to also occupy the 1/6~ only 1/7, therefore result in to oxidize the ditch upper part current velocity bigger( roughly 0.8~1.2 ms, even larger), but the bottom current velocity is very small( especially at the water is deep 2/3 or 3/4 below, mix with the
liquid has no current velocity almost), causing ditch bottom large quantity accumulate the mire( sometimes accumulate the mire thickness amount to a 1.0 ms), the valid capacity that reduced to oxidize the ditch consumedly, lowered to handle result, affected a water fluid matter.
Adding the top, downstream leads to flow the plank is a valid method that ameliorative current velocity distribute, increases the oxygen ability with the most convenient measure.The upper stream leads to flow the plank installs at be apart from to turn the 4.0 places( upper stream) ： dish( turn to brush) axis, lead to flow plank high degree as the deep 1/5~ in water 1/6, combine the perpendicularity install in the surface;The downstream leads to flow the plank installs at be apart from to turn dish( turn to brush) axis 3.0 ms.Leading to flow knothole material can use metals or glass steels, but regard glass steel as good.Lead to flow the plank compares with other ameliorative measure, can't not only increase the motive consumes with revolves cost, but also can still than significantly exaltation 充 oxygen ability with theories motive efficiency[13].
Moreover, pass in the spirit on board swim to establish the underwater push machine can also turn to the spirit of the liquid of admixture that brush the bottom low speed area circulates to flow to rise positive push function, from but the solution oxidizes the problem that low and dirty mire in current velocity in bottom in ditch sink accumulates.Establish the underwater push machine useds for exclusively the push mixs with the liquid can make movement method that oxidize the ditch much more vivid, this for economy energy, lift the high-efficiency having the very important meaning[14].
5. The Carrousel oxidizes the development of the ditch
Because the dirty water handles standard inside to divided by the phosphorus take off the nitrogenous request more and more strict,
the development that Carrousel further oxidized the ditch to also get.Current, the research and application includes morely below two category type:Tiny bore spirit type Carrousel 2000 systems, Carrousel 3000 system.
5.1 Tiny bore spirit type Carrousel 2000 system
Tiny bore spirit type Carrousel 2000 tiny bore in adoption in system spirit( provide oxygen equipments as the drum breeze machine), the tiny bore spirit machine can produce the diameter of large quantity as a surface for or so and small spirit steeping, this consumedly increases spirit bubble accumulates, undering the certain circumstance in capacity in pond make the oxygen transfer the gross measures aggrandizement.( if deep increment in pond, its spread the quality efficiency will be higher)Produce the technique ability of the factory house according to the current drum breeze machine, the valid water of the pond is deep biggest amounting to a 8 ms, therefore can select by examinations according to the different craft request the fit water is deep.The tradition oxidizes the ditch pushes to flow is to make use of to turn to brush, turn a disc or pour the umbrella type form machine realizes of, its equipments utilization is low, the motive consumes big.Tiny bore spirit type Carrousel 2000 systems then adopted the underwater pushes the way that flow, rises to dive the propeller the leaf the motivation that round creation the direct function namely in the of water, at push to flow the function to can keep dirty mire from sinking to decline effectively again at the same time.As a result, the adoption dives the propeller since lower the motive consume, making mire water got again to mixs with adequately.
Seeing from water power characteristic, tiny bore spirit type Carrousel 2000 systems are wreaths form the fold flows the pond type, concurrently pushing the flow type with complete mix with the type
flows .In regard to whole oxidize ditch, can think that oxidize the ditch is a complete mix with spirit pond, its density variety coefficient smallest even can neglect to do not account, enter the water will get the dilution quickly, therefore it have the very strong anti- pounds at the burthen ability.But have oxidize ditch inside of a certain very much the some pushing the characteristic of the flow type, in the nearby district in downstream in machine in spirit inDO density higher, but along with increase with spirit machine distance continuously then the density of DO lowers continuously.( appear the anoxia area)This kind of structure method makes friendly oxygen in area in anoxia area exsited to build the thing inside , making use of its water power characteristic well, coming to an efficiently the living creature takes off the nitrogenous purpose.
Tiny bore spirit type Carrousel 2000 system though have the oxygen ability strong, divided by the phosphorus take off the nitrogen effective, cover the area little