(2)生物脱氦工艺 a.三段生物脱氮工艺 将有机物氧化,硝化及反硝化段独立开来,每一部分 都有其自己的沉淀池和各自独立的污泥回流糸统。 CH, OH 圆 污泥回流 污泥回流 污泥回流 剩余汁 图18-4Bah三段生物脱氮工艺 前两段可合并,吏为西段后置反萌化: Mixe Nitrification Secondary clarifier Influent Effluent Denitrification tank
11 (2) 生物脱氮工艺 a. 三段生物脱氮工艺 将有机物氧化，硝化及反硝化段独立开来，每一部分 都有其自己的沉淀池和各自独立的污泥回流系统。 前两段可合并，变为两段后置反硝化：
b.前置反硝化工艺 PTeanoxic Aerobic The first concept of a preanoxic BNR was an anoxic -aerobic operating uence by Ludzock ond Etinger(1962). The influent wastewater was ho an anoxic zone, which wos followed by an aerobic zone. The process reies on the nitrate formed in the aerobic zone being returned via the RAS to the anoxic zone. Because the only nitrate fed to the anoxic zone is that in the rAs, denitrification is limited greatly by the RAS recycle noto. However, more recently, this process has been used le rates to prevent rising sludge in the dary darifiers due to deni MLE工艺【(AO)生物脱氪工艺】 缺氧段同样位于樂统前面,从曝气池末端回流含有大 量硝酸盐的混合漩,在缺氧池中进行反硝化脱氪,反 硝化反应以原污水中的有机物为碳源,这是目前通称 的缺氧好氧(AO)反硝化生物脱氮工艺 内循环(硝化液回流) 沉淀池 原废水 处理水 (好氧) 缺氧) 回流污泥 剩余污泥 图18-6缺氧一好氧生物脱氮工艺
12 b. 前置反硝化工艺 缺氧段同样位于系统前面，从曝气池末端回流含有大 量硝酸盐的混合液，在缺氧池中进行反硝化脱氮，反 硝化反应以原污水中的有机物为碳源，这是目前通称 的缺氧好氧（AO）反硝化生物脱氮工艺。 MLE工艺【（AO）生物脱氮工艺 】：
One of the most commonly used BNR processes is the modified Ludzack Etinger( MlE) process. Bamar(1973)in wdrock-Ettinger design by providing the internal recycle nitre bo the anoxic zone directly from the aerobic zone. Both t ore denitrification role and overall nitrogen removal efficiency are increased The inernal recyde flow ratio(recycle flowrate divided by influent RowTate)typically ranges from 2 bo 4. with sufficient infuent BOD and anoxic contact time, these recycle ratios result in ON concentration from 4 to 7 mg/ when treating domestic wastewater. The MlE process is very adaptable to exishing activate <10mg/L total nitrogen A BOD/KN rtio of 4: I in the infuent wastewater is usually sufficient for nitrate reduction by preanoxic processes. Typical anoxic tank anoxic zone is divided into 3 to 4 stages in series, denitrification kinet tes are increased and the tolal detention time needed may then be 50 to 70 percent of the single -soge design. Another modification of the MLE process, termed'eMLEuses on additional set of anoxic/aeration basins Aerobic Erens Retum activated sludge
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Preanoxic(Continued Aer。b Retum activated suoge Sludge Preanoxic zones can olso be used in a step-feed BNR process. Because step-feed BNR processes are usually adapted to existing mulfiple-pass full scole tanks, symmetrical anoxic/ aerobic stages are generally used. How- ever, nonsymmetrical designs with smaller initial anoxic/aerobic stages can take better a vontoge of the higher MLSS concentration in the early due bo less RAS dilution, resulting in greater treatment copacity. A possible aunt Aow spliting percent distribution for a 4- pass sy 15: 35: 30: 20. The final ow portion to the last anoxic/aerobic zone is criti reduced and w f thus determine the final eluent NO N concentrotion EfRuent NOx-N concentrations of less than 8 mg/L are possib
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(d) Sequencing batch reactor (SBR) 已地时 The SBR system(see Table 8-15) also employs preanoxic denitrification using BOD in the invent wastewater. Mixing is used during the fill riod to contact the mixed liquor with the invent wastewater. Fo many domestic applications, depending on the wastewater strength, sufficient bod and fill time are available to remove almost oll of the nitrate remaining in the mixed liquor after the setle and decant steps ome nitrate removal also occurs during the nonaerated sede and anaerobic or anoxic contacting during the fi shoving sih os,,.@nd is periods. Separate mixing provides operating Flexibility and is for anoxic operation during the aeration period,as In eeling properties in addition to nitrogen removal. Many facilities he ave repore effluent NO N concentrations of less than 5 mg/L nedved sunye The Bio-denitro TM process has also been referred to as a phased isolation oxidation ditch technology. the process was developed in Denmark for nitrogen removal and has been installed in over 75 full- scale focilities producing effluent total nitrogen concentrations of less than 8 mg/L(Stonsel and Coleman, 2000). The technology uses ot least to oxidation ditches in a series configuration in which the operating sequence of the ditches and operation of the aeration and anoxic zones is varied. Submerged mixers are installed in the ditches so that for some operating phe continues to receive in Aunt wastewater and operates as a preanoxic cone. Similor to the SBR operation, nitrate is available from a previous erobic nitrification operation. Besides denitrification in the preanoxic cone, nitrate reduction is also possible during the aerobic operation vef. A typical duration for phe 5.日.5.1.5.do.5h
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