Biological N and P removal in activated sludge processes

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1 Biological N and P removal in activated sludge processes Sara Hallin Department of Microbiology, SLU Sara Hallin

2 Metabolism

3 Oxidation: KOLFÖRENING KOLDIOXID + ELEKTRONER + VÄTEJONER Reduktion: SYRE + ELEKTRONER + VÄTEJONER VATTEN Fullständig reaktion: KOLFÖRENING + SYRE KOLDIOXID + VATTEN BIOKEMISKT BUNDEN ENERGI

4 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).

5 Traditionell ASP Organiskt material bryts ner av mikroorganismer i luftningsbassängen. Slammet (biomassa och organiskt material)avskiljs från det renade vattnet i sedimenteringsbassängen..

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7 Microbiological reactions in the N cycle ATMOSPHERE Denitrification N 2 SOIL/WATER Nitrogen fixation N 2 O Organically bound nitrogen orgnh 2 NO Assimilation Mineralization/ Ammonification Assimilation NO 2 NH 4 + NO 2 NO 3 Nitrification Dissimilatory nitrate reduction to ammonium

8 Nitrogen removal Achieve N removal by combining the processes Nitrification and Denitrification: + NH 4 NH NO 2 OH NO NO NO N 2 O N 2

9 Nitrification a two step oxidation process Ammonia oxidation Nitrite oxidation NH 3 NO 2 NO 3

10 Ammonia oxidation: NH 3 + 1,5O 2 NO 2 + H + + H 2 O

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12 Nitrite oxidation: NO 2 + ½ O 2 NO 3 Periplams OH

13 Carbon metabolism Cell constituents Growth

14 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

15 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

16 Ammonia Denitrifier oxidizer Diversity diversity in soil Bacteria Eukarya Archaea Ammonia oxidizers

17 NH 3 oxidizers Nitrosomonas Nitrosococcus Nitrosospira NO 2 oxidizers Nitrobacter Nitrospira Thaumarchaeota Nitrosopumilis Nitrosomonas europeae

18 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 )

19 Denitrification: anaerobic respiration ATP Organic compound CO 2 Carbon flow Electron flow Biosynthesis NO 3, (NO 2, N 2 O)

20 Denitrification Pathway pathway 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 ):

21 Denitrifier diversity Diversity Bacteria Eukarya Archaea Denitrifiers

22 Denitrification in ecosystems Oceanic OMZ; 14% (81 Tg) Terrestrial; 22% (124 Tg) Continental Shelf; 44% (250 Tg) Groundwater; 8% (44 Tg) Lakes; 5% (31 Tg) Rivers; 6% (35 Tg) Estuaries; 1% (8 Tg) Annual N exported to atmosphere via denitrification (Seitzinger et al., 2006)

23 Nitrogen removal Achieve N removal by combining the processes Nitrification and Denitrification: + NH 4 NH NO 2 OH NO NO NO N 2 O N 2

24 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 NO 3 NO 2 NO N 2 O N 2

25 Nitrifierande bakterier Denitrifierande bakterier Nitrifierare finns i mark och vatten Denitrifierare finns nästan överallt Bara några få arter Nitrifikation är två energigivande processer som utförs av två olika grupper av bakterier Nitrifierare växer långsamt Många bakteriesläkten Denitrifikation är en alternativ andningsprocess i frånvaro av syre Denitrifierare är växer oftast snabbt

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30 Nitrogen reduction (%) Denitrification rate (mg N 2 ON g 1 VSS h 1 ) Effekt av extern kolkälla på kvävereningen a Kvävereningsgrad (%): 2. Denitrifikastionskapacitet: b E 60 E R R Time (days) Tid (dagar) Time (days) Tid (dagar) R = Fördenitrifikation utan extern kolkälla E = Fördenitrifikation med etanoltillsats

31 Intermittent dosering av etanol i en fördenitrifikationsprocess Hasselblad & Hallin Wat. Sci.Technol.

32 Nitrogen cycling N 2 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!

33 Nitrogen removal Achieve N removal by combining the processes Nitrification and Denitrification: + NH 4 NH NO 2 OH NO NO NO N 2 O N 2

34 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

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36 World greenhouse gas emissions by sector

37 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).

38 PHB synthesis & degradation Acetic acid AcetylCoA AcetoacetylCoA Acetoacetate ßhyroxybutyrylCoA ßhydroxybutyrate Polyßhyroxybutyrate (PHB)

39 Denitrification Biological phosphorus removal Recirculation of NO 3 ANAEROBIC REACTOR AEROBIC REACTOR SEDIMENTATION Organics Energy PO 4 3 O 2 CO 2 +H 2 O Energy PO 4 3

40 Other perspectives

41 Constructed wetlands Downstream WWTPs Nitrification and Denitrification Habitat for birds and frogs

42 µg N/g DW/h Plants affect denitrification Ruiz et al., 2009, FEMS Microbiol. Ecol.

43 Wetland plants effects Rhizospehere Sediment DGGE of nosz Low rates High rates Typha and Fragmites select nosz communities Seasonal differences Ruiz et al., 2009, FEMS Microbiol. Ecol.

44 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?

45 Ekeby wetland in Eskilstuna Ekeby Constructed Wetland Total area: 36 ha Flow: ~45000m 3 /day

46 Waterflow paths Kjellin et al., 2007, Wat. Res.

47 Denitrification rates Multiple regressions: PDA T R CN Kjellin et al., 2007, Wat. Res.