Biological N and P removal in activated sludge processes Sara Hallin Department of Microbiology, SLU Sara Hallin
Metabolism
Oxidation: KOLFÖRENING KOLDIOXID + ELEKTRONER + VÄTEJONER Reduktion: SYRE + ELEKTRONER + VÄTEJONER VATTEN Fullständig reaktion: KOLFÖRENING + SYRE KOLDIOXID + VATTEN BIOKEMISKT BUNDEN ENERGI
Fermentation: GLUKOS ETANOL + KOLDIOXID BIOKEMISKT BUNDEN ENERGI Fermentation av socker till etanol och koldioxid. En del av kolet i sockret har oxiderats till koldioxid medan en del har reducerats till etanol (vanlig sprit).
Traditionell ASP Organiskt material bryts ner av mikroorganismer i luftningsbassängen. Slammet (biomassa och organiskt material)avskiljs från det renade vattnet i sedimenteringsbassängen..
Microbiological reactions in the N cycle ATMOSPHERE Denitrification N 2 SOIL/WATER Nitrogen fixation N 2 O Organically bound nitrogen org-nh 2 NO Assimilation Mineralization/ Ammonification Assimilation NO 2 - NH 4 + NO 2 - NO 3 - Nitrification Dissimilatory nitrate reduction to ammonium
Nitrification in water treatment Nitrification lowers BOD load in recipient Nitrification coupled to denitrification lowers N load in recipient Nitrogen removal systems: - natural wetlands - constructed wetlands - wastewater treatment plants Process problems with inhibition: Microbial sensors for detecting nitrification inhibitors
Nitrification Nitrification involves several reactions and two different bacteria: 1. Dissociation of ammonium 2. Oxidation of ammonia Ammonia monooxygenase (AMO): Integral membrane protein Can oxidize methane Cometabolize halogenated compounds Inhibited by acetylene 3. Oxidation of hydroxylamine Hydroxylamine oxidoreductase (HAO): Soluble, periplasmic protein Nitrosomonas 4. Oxidation of nitrite
Ammonia oxidation: NH 3 + 1,5O 2 NO 2- + H + + H 2 O
Nitrite oxidation: NO 2- + ½ O 2 NO 3 - Periplams OH -
Carbon metabolism Cell constituents Growth
Energetic constraints... Energetic constraints are severe, particularly for NO 2- oxidizers. Many NO 2- also grow chemoorganotrophically on glucose or other substrates. 1. ATP and NADPH (reducing power) requirements in Calvin cycle 2. NAD(P)H formed by reverse e - flow: 2e - Cyt c e - e - Cyt c NAD(P) + O 2
Ammonia oxidizing archaea and bacteria (AOA and AOB) The organisms
NH 3 oxidizers Nitrosomonas Nitrosococcus Nitrosospira NO 2- oxidizers Nitrobacter Nitrospira Crenarchaeota (Nitrosopumilis) Nitrosomonas europeae
Denitrifikation är en andningsprocess som där nitrat omvandlas till kvävgas i flera komplicerade steg inom en och samma bakteriecell: nitrat nitrit kväveoxid lustgas kvävgas (NO 3 - NO 2 - NO N 2 O N 2 )
Denitrification: anaerobic respiration ATP Organic compound CO 2 Carbon flow Electron flow Biosynthesis NO 3-, (NO 2-, N 2 O)
Denitrification Denitrification is a respiratory process where oxidized nitrogen compounds (NO 3-, NO 2 ) are reduced stepwise to gaseous end products (NO, N 2 O, N 2 ): Cytoplasma NO 2 - NO 3 - NADH 2 NAD + nar 2e- 2e- 2enor e- NO 3 - Periplasma H + Proton motive force nir NO 2 - NO NO N 2 O nos N 2 O N 2
More than 50 genera and 130 species of denitrifying bacteria Archaea: Extreme halophiles, Halobacterium Proteobacteria (α, β, γ): Phototrophic bacteria, Rhodobacter Budding bacteria, Hyphomicrobium, Blastobacter Helical bacteria, Azospirillum, Campylobacter Nitrogen fixing bacteria, Rhizobium Ammonia oxidizing bacteria, Nitrosomonas Gram negative cocci, Paracoccus, Neisseria Chemoautotrophs, Thiobacillus, Beggiatoa Others, Alcaligenes, Pseudomonas, Moraxella, Flavobacterium Gram positives: Spore forming, Bacillus Non-spore forming, Corynebacterium
Nitrifikation Redox - Denitrifikation Glukos Glukolys 2 Pyruvat 2 ATP 2 NADH 8 NADH 2 FADH Citronsyra cykeln 2 GTP 6 CO 2 NH 4 + NO 2 - ATP NADH FADH ATP ATP O 2 H 2 0 + NO 3 - NO 2 - NO N 2 O N 2
Nitrifierande bakterier Nitrifierare finns i mark och vatten Bara några få arter Nitrifikation är två energigivande processer som utförs av två olika grupper av bakterier Nitrifierare växer långsamt Denitrifierande bakterier Denitrifierare finns nästan överallt Många bakteriesläkten Denitrifikation är en alternativ andningsprocess i frånvaro av syre Denitrifierare är växer oftast snabbt
Effekt av extern kolkälla på kvävereningen 1. Kvävereningsgrad (%): 2. Denitrifikastionskapacitet: 100 15 80 E 60 E 10 40 5 20 R R 0 0 10 20 30 40 50 60 Tid (dagar) 0 0 10 20 30 40 50 60 Tid (dagar) R = Fördenitrifikation utan extern kolkälla E = Fördenitrifikation med etanoltillsats
Intermittent dosering av etanol i en fördenitrifikationsprocess Hasselblad & Hallin. 1998. Wat. Sci.Technol.
Biological phosphorus removal ANAEROBIC AEROBIC Short chain fatty acids Energy Phosphate O 2 CO 2 +H 2 O Energy Phosphate Energy consumption for uptake of soluble organics. ATP and PO43- is released. Energy is conserved as polyphosphate granules. Uptake of PO 4 3-. Consumption of stored products (PHB).
PHB synthesis & degradation Acetic acid Acetyl-CoA Acetoacetyl-CoA Acetoacetate ß-hyroxybutyryl-CoA ß-hydroxybutyrate Poly-ß-hyroxybutyrate (PHB)
Biological phosphorus removal Recirculation of NO 3 - ANAEROBIC REACTOR AEROBIC REACTOR SEDIMENTATION Organics Energy PO 4 3- Denitrification CO 2 +H 2 O Energy PO 3- O 2 4
Other perspectives
Downstream WWTPs Constructed wetlands Nitrification and Denitrification Habitat for birds and frogs
Plants affect denitrification µg N/g DW/h Ruiz et al., 2009, FEMS Microbiol. Ecol.
DGGE of nosz Wetland plants effects Typha and Fragmites select nosz communities Rhizospehere Sediment Low rates High rates Seasonal differences Ruiz et al., 2009, FEMS Microbiol. Ecol.
Conclusions and outlook Typha and Phragmites select nosz communities Typha and Phragmites increase denitrification activity Seasonal differences Is increase in rhizosphere enough for increased capacity of wetland? What about the abundance of denitrifiers?
Ekeby wetland in Eskilstuna Ekeby Constructed Wetland Total area: 36 ha Flow: ~45000m 3 /day
Water-flow paths Kjellin et al., 2007, Wat. Res.
Denitrification rates Multiple regressions: PDA = 4 0.13 1.11 2.3 10 T R CN Kjellin et al., 2007, Wat. Res.
N 2 Nitrogen cycling NH 3 Nitrification Assimilation + others NO 3-1. Nitrogen cycling necessary! 2. Nitrogen removal good! 3. Nitrogen loss bad! 4. Nitrous oxide (GHG) emission really bad!
D I E T A G R I C U L T U R E E N V I R O N M E N T
World greenhouse gas emissions by sector