Hauv kev kho dej khib nyiab, kev hloov pauv roj ntsha ntawm nitrogen yog cov txheej txheem tseem ceeb rau kev ua tiav cov nitrogen thiab phosphorus tshem tawm thiab ua raws li cov qauv emission. Cov txheej txheem no tsis yog ib qho tshuaj tiv thaiv nkaus xwb, tab sis yog kev sib koom ua tiav ntawm peb kauj ruam tseem ceeb: ammonification, nitrification, thiab denitrification. Ua ke, cov kauj ruam no maj mam hloov cov organic nitrogen thiab inorganic nitrogen nyob rau hauv cov dej khib nyiab mus rau hauv cov pa nitrogen uas tsis muaj teeb meem, txo cov nitrogen load hauv dej.
Taw qhia
Nitrogen hauv dej phwj feem ntau muaj nyob rau hauv cov ntaub ntawv ntawm cov organic nitrogen (xws li cov protein thiab urea) thiab ammonia nitrogen. Kev tso tawm ncaj qha tuaj yeem ua rau muaj teeb meem ib puag ncig xws li eutrophication ntawm cov dej hauv lub cev. Cov kev kho mob lom neeg, nrog rau lawv qhov zoo ntawm kev ua haujlwm siab thiab kev lag luam, tau dhau los ua cov thev naus laus zis tseem ceeb rau kev tshem tawm nitrogen los ntawm cov dej phwj tuaj. Lub hauv paus ntsiab lus tseem ceeb yog siv cov kev ua ub ua no ntawm cov kab mob sib txawv nyob rau hauv ib puag ncig tshwj xeeb kom maj mam hloov cov ntsiab lus nitrogen, thaum kawg ua tiav kev tshem tawm gaseous ntawm lub cev dej mus rau qhov chaw. Cov nram qab no yuav systematically dissect lub ntsiab mechanism ntawm tus txheej txheem no.
I. Ammonification: hloov cov organic nitrogen rau hauv ammoniacal nitrogen
Ammonification yog thawj kauj ruam hauv kev tshem tawm nitrogen los ntawm cov dej khib nyiab, xa mus rau kev hloov pauv ntawm cov organic nitrogen tebchaw rau hauv
Cov txheej txheem yog yooj yim los ntawm ammonifying kab mob. Nyob ntawm cov ntsiab lus oxygen ntawm ib puag ncig, nws tuaj yeem faib ua ob txoj hauv kev: aerobic transformation thiab anaerobic transformation
1. Kev hloov pauv ntawm aerobic
Nyob rau hauv aerobic tej yam kev mob, cov kab mob xws li Aeromonas hydrophila, Bacillus cereus, thiab facultative Proteus vulgaris koom rau hauv cov tshuaj tiv thaiv, feem ntau degrading organic nitrogen los ntawm ob lub ntsiab mechanisms:
• Oxidative deamination: Nyob rau hauv lub catalysis ntawm oxidases, cov amino acids maj mam poob lawv cov amino pawg los tsim keto acids thiab ammonia.
Siv alanine ua piv txwv:
CH3CH(NH2)COOH → CH3C(NH2)COOH → CH3COCOH + NH3
(Alanine → Iminopropionic acid → Pyruvic acid + Ammonia)
• Hydrolysis ntawm ammonia: Raws li kev ua ntawm hydrolytic enzymes, nitrogen-muaj cov organic tebchaw xws li urea yog hydrolyzed los tsim ammonia.
Urea hydrolysis tshuaj tiv thaiv:
(NH2) 2CO + 2H2O → 2NH3 + CO2 + H2O
Cov kab mob koom nrog hauv cov txheej txheem no suav nrog cov kab mob aerobic xws li Enterococcus faecalis thiab Bacillus urea.
2. Kev hloov pauv anaerobic
Hauv anaerobic lossis oxygen- ib puag ncig tsis txaus, anaerobic thiab facultative anaerobic microorganisms ua tiav ammonification los ntawm peb txoj hauv kev:
• Txo thiab deamination:
RCH(NH2)COOH + 2H → RCH2COOH + NH3
• Dej- raws li ammonia tshem tawm:
RCH(NH2)COOH + 2H2O → RCH(OH)COOH + NH3
• Lub cev qhuav dej thiab deamination:
CH2(OH)CH(NH2) → CH3COCOOH + NH3+H2O
II. Nitrification: Oxidation ntawm ammonia nitrogen rau nitrate nitrogen
Nitrification yog qhov thib ob tseem ceeb cov tshuaj tiv thaiv uas oxidizes NH3-N rau NOx-N, uas yog synergistically ua tiav los ntawm cov kab mob nitrite thiab cov kab mob nitrate, thiab muab faib ua ob theem: nitritation thiab nitrification.
1. Cov tshuaj tiv thaiv mechanism
• Nitrition cov tshuaj tiv thaiv (tswj los ntawm cov kab mob nitrite):
NH3 + 1.5O2 → NO2− + H+ + H2O + 273.5kJ
• Nitrification cov tshuaj tiv thaiv (tswj los ntawm nitrobacteria):
NO2− + 0.5O2 → NO3− + 73.19kJ
• Cov qauv tshuaj tiv thaiv tag nrho:
NH3 + 2O2 → NO3− + H+ + H2O + 346.69kJ
2. Cov txheej txheem tseem ceeb
• Cov pa oxygen siab heev: Kev siv theoretical noj ntawm 4.2g ib qhov kev tshem tawm ntawm 1g, yog li cov tshuaj nitrification yuav tsum tau ua raws li qhov muaj peev xwm aeration.
• Kev loj hlob tsawg: cov kab mob Nitrifying muaj cov txiaj ntsig ntawm tes tsis tshua muaj txiaj ntsig, thiab lawv muaj kev ua haujlwm tsis txaus thaum lub caij ntuj no txias. Yog li ntawd, nws yog ib qho tsim nyog yuav tsum tswj kom muaj cov sludge siab kom ntseeg tau tias kev kho mob zoo.
• Kev noj alkalinity: Cov tshuaj tiv thaiv ua rau muaj ntau ntawm H+. Txoj kev xav, 7.54g ntawm alkalinity (xws li CaCO3) yog noj rau txhua 1g ntawm oxidation. Nws yog ib qho tsim nyog los tswj xyuas qhov system pH stability los ntawm kev ntxiv cov tshuaj alkaline.
III. Denitrification: Txo cov nitrate nitrogen rau nitrogen gas
Denitrification yog cov kauj ruam kawg hauv kev tshem tawm nitrogen los ntawm cov dej khib nyiab. Nws hais txog cov txheej txheem uas denitrifying cov kab mob txo NOx-N thiab lwm cov nitrogen oxides rau nitrogen gas los yog gaseous nitrogen oxides raws li electron txais nyob rau hauv anaerobic los yog oxygen -deficient (DO <0.3 ~ 0.5mg / L) tej yam kev mob.
1. Cov tshuaj tiv thaiv mechanism
𝑁𝑂3−→𝑁𝑂2−→>𝑁𝑂→𝑁2𝑂→𝑁2
Ua kom txo qis cov tshuaj tiv thaiv (siv cov organic tebchaw raws li cov neeg pub khoom siv hluav taws xob ua piv txwv):
NO3−+5[H] (electron donor) → 0.5N2 + 2H2O + OH−
NO2− {{1} [H] (electron donor) → 0.5N2 + H2O + OH−
2. Carbon qhov yuav tsum tau muaj thiab microbial yam ntxwv
• Cov pa roj carbon qhov chaw noj: Txoj kev xav, 2.86g ntawm cov pa roj carbon yuav tsum tau hloov 1g ntawm nitrate nitrogen rau hauv N2, thiab 1.71g ntawm cov organic teeb meem yog xav tau los hloov 1g ntawm nitrite nitrogen.
• Ntau haiv neeg ntawm cov neeg pub khoom siv hluav taws xob: [H] tuaj yeem muab los ntawm cov organic compounds, sulfides, thiab lwm yam., muab ntau qhov kev xaiv carbon rau cov txheej txheem optimization.
• Cov yam ntxwv ntawm microbial: Cov kab mob denitrifying feem ntau yog cov kab mob facultative, uas ua pa siv O2 ua lub davhlau ya nyob twg electron txais nyob rau hauv muaj oxygen, thiab siv NOx-N rau kev ua pa thaum tsis muaj oxygen. Cov yam ntxwv no yog lub hauv paus tseem ceeb ntawm cov txheej txheem anoxic denitrification.
Cov ntsiab lus
Kev hloov pauv lom ntawm nitrogen hauv cov dej phwj tuaj yog cov txheej txheem sib txuas sib txuas:
Ammonification rhuav tshem cov organic nitrogen molecules, tso ammonia nitrogen;
Nitrification yuav maj mam oxidation ntawm ammoniacal nitrogen rau nitrate nitrogen nyob rau hauv ib qho chaw aerobic;
Denitrification txo nitrate nitrogen rau nitrogen gas nyob rau hauv anoxic ib puag ncig, thaum kawg ua tiav cov kev tshem tawm ntawm nitrogen los ntawm dej lub cev mus rau cov huab cua.
Kev ua haujlwm tau zoo ntawm cov txheej txheem no tso siab rau kev tswj xyuas meej ntawm cov ntsiab lus tseem ceeb xws li cov ntsiab lus oxygen, alkalinity, carbon qhov chaw, thiab qhov kub thiab txias, thiab ua haujlwm tseem ceeb hauv kev txhawb nqa kom ua tiav qhov ruaj khov nitrogen tshem tawm hauv cov nroj tsuag dej khib nyiab niaj hnub hauv nroog thiab kev kho dej khib nyiab.