1、污水深度處理與回用 (2)生物脫氮原理及工藝,污水中氮的存在形式,Subdivision of Nitrogen in Wastewater (Influent),COD related,SI*iN,SI (3%),XI*iN,XI (10%),SF*iN,SF+XS*iN,XS (12%),iN,BM=0.07 gN/gCODBM,Nitrogen Removal: N in WastewaterN2 (into atmosphere),氮的轉化途徑,Nitrogen Conversion Pathways (N Cycle),生物脫氮過程,Nitrification and denitri

2、fication,生物脫氮過程,Nitrification,NH4+,NO2-,NO3-,NO2-,NO(g),N2O(g),N2(g),Denitrification,Aerobic (DO);,Autotrophic,Anoxic;,Heterotrophic (Organic Carbon),tG=ln2/max,生物脫氮過程,硝化反應計量系數(shù)(Stoichiometry),不考慮合成,(1）硝化需氧量（NOD）,1.5*32/14=3.43 mgO2/mgNH4+-N,0.5*32/14=1.14 mgO2/mgNO2-N,=4.57 mgO2/mgNO3-NProduced,(2）消

3、耗堿度（Alkalinity）,Ex. alk. = 200 mg/L as CaCO3; nitrate production = 24 mg N/L. Expected alk. = 200 - 7.1424 = 29 mg/L as CaCO3. If alkalinity 40 mg/L as CaCO3; then dangerous.,pH decreases,生物脫氮過程,硝化反應計量系數(shù)(Stoichiometry),考慮合成,產(chǎn)率系數(shù)（Yield coefficient）:,生物脫氮過程,硝化反應動力學（Kinetics）,Growth Rate:,Decay Rate :,

4、Net Growth Rate:,XA: Nitrifiers Concentration (mg VSSL-1); : Specific growth rate of nitrifiers (d-1); max: Maximum specific growth rate of nitrifiers (d-1); SNH: Ammonium-N concentration (mgL-1); KNH: Half saturation coefficient for ammonium (mgNL-1); bA: Decay rate of nitrifiers (d-1),mg VSS/(Ld),

5、mg VSS/(Ld),mg VSS/(Ld),生物脫氮過程,硝化反應影響因素（Factors Influencing Nitrification）,(1). Minimum SRT,Sludge Wastage Rate = XA/SRT (mg VSS/(Ld),生物脫氮過程,硝化反應影響因素（Factors Influencing Nitrification）,(1). Minimum SRT,Waste Sludge Qw, Xr,Effluent,Influent,Secondary clarifier,Aeration basin,Q,Qeff, Xeff,X, V,Sludge

6、Return Qr, Xr,Net Growth Rate Sludge Wastage Rate,生物脫氮過程,硝化反應影響因素（Factors Influencing Nitrification）,(1). Minimum SRT,At steady state:,SRTmin,Question: 1) Calculate SRTmin; SRT for SNH=1 mg/l.,生物脫氮過程,硝化反應影響因素（Factors Influencing Nitrification）,(2). Temperature,For every 6C drop, the value will halve

7、. Design for nitrification plant should be based on the minimum expected temperature.,生物脫氮過程,硝化反應影響因素（Factors Influencing Nitrification）,(3). Alkalinity and pH,Optimal pH: 7.2-8.5,For 5pH7.2:,1) Lack of inorganic carbon source; 2) Decrease of pH.,生物脫氮過程,硝化反應影響因素（Factors Influencing Nitrification）,(4

8、). Dissolved Oxygen (DO) Concentration,SO: DO Concentration, mg/L; KO: Half saturation coefficient for DO, 0.5 mgO2/L,生物脫氮過程,硝化反應影響因素（Factors Influencing Nitrification）,(5). Inhibition and Toxicity,Complete inhibition to Nitrosomonas Nickel0.25 3.0 mg/L Chromium0.25 mg/L Copper0.1 0.5 mg/L Zinc3.0 m

9、g/L NH4+ and NO2- concentration range for Nitrobacter pH NH4+-N, mg/L NO2-N, mg/L 6.0 210 2100 30 330 6.5 70 700 88 1050 7.0 20 210 260 3320 7.5 7 70 8.0 2 20,生物脫氮過程,反硝化反應Denitrification (P310),Conditions for denitrification:,1) Presence of a facultative bacterial mass (Denitrifiers);,2) Presence of

10、 Nitrate/Nitrite (electron acceptor) and absence of DO (Anoxic Condition);,3) Presence of an electron donorReducing Power (Organic Carbon Source);,生物脫氮過程,反硝化反應Stoichiometry,Oxygen equivalent（氧當量）: when nitrate serves as the electron acceptor, the equivalent mass of oxygen (as O2) is: 1 mg NO3-N=2.86

11、 mg O2 （硝酸氮接受電子的能力是氧氣的2.86倍)（P310）,2) Alkalinity Change:,NO3-,OH-,CaCO3,1,1,1/2,3.57 mg as CaCO3 alkalinity is recovered per 1 mg NO3-N denitrified During nitrification, 7.14 mg as CaCO3 alkalinity is consumed per 1 mg NH4+-N nitrified. Hence, for low alkalinity wastewater, denitrification is strong

12、ly recommended to prevent the pH drop.,生物脫氮過程,反硝化反應Stoichiometry,3) COD Requirement:,SF/SNO3=2.86/(1-YH)=2.86/(1-0.63)=7.73 gCOD/gNO3-N,YH: Heterotrophic yield for growth on substrate, 0.63 gCODXH/gCOD,生物脫氮過程,反硝化反應Kinetics,Theoretical (Influencing factors),S: Readily biodegradable COD concentration,

13、 mg/L,SNO3: NO3-N Concentration, mg/L,KS: Half saturation coefficient, 4.0 gCOD/L,KNO3: Half saturation for nitrate-N, 0.5 gN/L,KiO2: Inhibition coefficient for oxygen, 0.2 gO/L,c: DO concentration, mgO/L,生物脫氮過程,反硝化反應Kinetics,In practice,生物脫氮工藝,基本構型Post denitrification,好氧,缺氧,NH4+NO3-,CODCO2,NO3- + C

14、ODN2,External Carbon Source (Methanol),后置反硝化（P312）,優(yōu)點：完全反硝化 缺點：1）外加碳源 ；2)可能需要補充堿度；3）浪費了NO3-的氧化能力,Qin COD TN,Return Sludge (r),生物脫氮工藝,基本構型Pre-denitrification,缺氧,好氧,NH4+NO3-,NO3- + CODN2,優(yōu)點：1）利用進水碳源；2）利用了 NO3-的氧化能力；3）補償一半堿度 缺點：1) 硝化液回流（R: 200-300%）；2）不能實現(xiàn)完全反硝化,Nitrified Liquid Recirculation (R),Qin CO

15、Din TNin,缺氧/好氧脫氮工藝；Modified Ludzack-Ettinger (MLE) (P313),Return Sludge (r),生物脫氮工藝,基本構型Pre-denitrification,硝化液回流比的影響,Assumption: 1) Complete nitrification in aerobic reactor; 2) Complete denitrification in anoxic reactor.,Then:,TNEff.=NO3-Neff=TKNAn,Eff,Mass Balance for Anoxic Reactor:,IN: Qin*TKNin

16、,OUT: (Qin+R*Qin+r*Qin)*TKNAn,Eff,Qin*TKNin=(Qin+R*Qin+r*Qin)*TKNAn,Eff,TKNAn,Eff/TKNin=1/(1+r+R),TNEff/TNin=1/(1+r+R),Removal(%)=100*(1-TNEff/TNin) =100*1-1/(1+r+R),r=100%,- Seldom produce effluent 5 mg/L TN for municipal wastewater - Removal depends on influent COD/TN ratio,生物脫氮工藝,Four-Stage Bardenpho Process,缺氧(An1),好氧(A1),NH4+NO3-,NO3- + CODN2,Nitrified Liquid Recirculation (R*Qin),Qin COD TN,缺氧(AN2),好氧(A2),Incorporation of pre- and post denitrification; Effective utilization of influent carbon so