Short-Cut Nitrogen Removal: A State of the Art Review

Transcription

1 Short-Cut Nitrogen Removal: A State of the Art Review Jose Jimenez, Ph.D., P.E. Brown and Caldwell

2 Outline Introduction Overview of nitrogen (N) removal in wastewater Conventional N removal Nitritation-Denitritation/ Nitrite-Shunt Partial Nitritation- Deammonification Case studies potential savings 2

3 Introduction 3

4 Sidestream Short-Cut N Removal Established Technology 4

5 Sidestream Short-Cut N Removal Established Technology 5

6 Energy Savings 6

7 Carbon Requirements for Mainstream Biological Nitrogen Removal Processes Constituent Carbon required for nitrogen removal (mg COD /mg N) Net Process Oxygen Requirement (mg O2/mg N Converted to N2) Nitrification denitrification Nitritationdenitritation Partial nitritationdeammonificati on

8 Nitrogen Removal Short Cut Nitrogen Removal Processes 8

9 Conventional Nitrification-Denitrification Autotrophic Bacteria Aerobic Environment Heterotrophic Bacteria Anoxic Environment 75% O 2 (energy) ~100% Alkalinity 25% O 2 (energy) 1 mole Ammonia (NH 3 / NH 4 + ) 1 mole Nitrite (NO 2- ) Ammonia Oxidizing Bacteria (AOB) 1 mole Nitrate (NO 3- ) Nitrite Oxidizing. Bacteria (NOB) 40% Carbon (BOD) 1 mole Nitrite (NO 2- ) 60% Carbon (BOD) ½ mol Nitrogen Gas (N 2 ) Oxygen Required 3.3 lb O 2 /lb N Carbon Required 6.6 lb COD/lb N Yield 1.9 lb VSS/lb N 9

10 N Removal Process NITRITE OXIDIZING BACTERIA (NOB) AMMONIA OXIDIZING BACTERIA (AOB) OHO DENITRIFYING BACTERIA 10

11 Conventional Nitrogen Removal Processes Advantages WW carbon utilized for denitrification Alkalinity recovered Disadvantages Large BNR volume Nitrogen removal limited by IMLR 11

12 Conventional Nitrogen Removal Processes Effect of C:N Ratio on Denitrification Effluent NO3-N (mg/l) Influent BOD:TKN Ratio (mg BOD5/mg TKN as N) Jimenez et al. (2010) 12

13 Nitritation-Denitritation = Nitrite Shunt Autotrophic Bacteria Aerobic Environment Nitritation 75% O 2 (energy) ~100% Alkalinity 25% O 2 (energy) 1 mole Nitrite (NO 2- ) Ammonia Oxidizing Bacteria (AOB) 1 mole Nitrate (NO 3- ) Nitrite Oxidizing. Bacteria (NOB) 1 mole Nitrite (NO 2- ) Heterotrophic Bacteria Anoxic Environment 40% Carbon (BOD) 60% Carbon (BOD) Denitritation 1 mole Ammonia (NH 3 / NH 4 + ) ½ mol Nitrogen Gas (N 2 ) Advantages: 25% reduction in oxygen demand (energy) 40% reduction in carbon (e - donor) demand 40% reduction in biomass production 13

14 Nitrite-Shunt Inhibited by high ammonia conc. Grows faster than NOB NITRITE OXIDIZING BACTERIA (NOB) AMMONIA OXIDIZING BACTERIA (AOB) Compet e for nitrite HETEROTROPHIC DENITRIFYING BACTERIA At low to no DO OHO outcompete NOB for nitrite

15 Carbon Requirements for Mainstream Biological Nitrogen Removal Processes Effluent NO x -N (mg/l) Soluble COD:NH 4 Ratio SND Shunt Brown and Caldwell Internal Data 15

16 NOB Outselection Competition with OHOs for Nitrite at low DO operation AOB always at maximum growth rate (aerobic SRT control with excess NH4 available) Aggressive SRT control Oxygen affinity Free ammonia inhibition of NOB Specific growth rate (1/d) SNPR (mgn/gvss.d) AOB NOB Ammonia (AOB) or nitrite (NOB), mg-n/l A - AOB A - NOB AOB Monod NOB Monod DO (mg/l) 16

17 Nitrite-Shunt In a fully nitrifying system (no nitrite-shunt), the ratio of NOB/AOB should equal the ratio of the respective yield coefficients For example, if YNOB = 0.09 and YAOB = 0.15, then NOB/AOB = 0.6 The plant mixed liquor NOB/AOB ratio can be estimated from a fully-aerated SNR test NO3PR/NOXPR is linked directly to the ratio NOB/AOB If a lower value is measured in a fully-aerated SNR test on plant mixed liquor, then it is likely that the NOB population is suppressed and nitrite shunt is occurring 17

18 St. Petersburg FL Low DO Mainstream Nitrite Shunt 7000 Daily Average Airflow (scfm) Days Nitrification SND 10 Nitrogen Species, mg/l /28/13 8/4/13 8/11/13 8/18/13 8/25/13 9/1/13 Ammonia Nitrite Nitrate 18

19 St. Petersburg FL - Inorganic Nitrogen Profile Unaerated DO = 0.02 ± 0.01 mg/l Aerobic 1 DO = 0.22 ± 0.15 mg/l Aerobic 2 DO = 0.12 ± 0.08 mg/l Aerobic 3 DO = 0.08 ± 0.05 mg/l 0.8

20 HRSD Pilot Plant - AvN Control NH4-N DO = set point DO Controller/ PLC Aerobic Duration Controller/ PLC NH4-N - NOx-N = setpoint Nitrogen (mg/l) Aerobic Fraction NH4-N NOx-N Aerobic Fraction D.O. NO2-N NO3-N M S Air Regmi et al., Dissolved Oxygen (mg/l) Dissoved Oxygen (mg/l) hour 24-hour DO

21 AvN Aeration Advantage Model-based evaluation of mechanisms and benefits of mainstream shortcut nitrogen removal processes (2014), Ahmed Al-Omari, Bernhard Wett, Ingmar Nopens, Haydee De Clippeleir, Mofei Han, Pusker Regmi, Charles Bott, Sudhir Murthy. WWTMOD 21

22 Partial Nitritation-Anammox = Deammonification 22

23 Mainstream Deammonification Four Groups Of Bacteria Involved NITRITE OXIDIZING BACTERIA (NOB) HETEROTROPHIC DENITRIFYING BACTERIA AMMONIA OXIDIZING BACTERIA (AOB) ANAMMOX BACTERIA 23

24 Mainstream Deammonification Four Groups Of Bacteria Involved Inhibited by high ammonia conc. Grows faster than NOB at low DO NITRITE OXIDIZING BACTERIA (NOB) AMMONIA OXIDIZING BACTERIA (AOB) Compet e for nitrite HETEROTROPHIC DENITRIFYING BACTERIA ANAMMOX BACTERIA Requires process control to prevent growth of competing Favored by low DO Favored by no DO Inhibited by nitrite

25 Challenges of Nitrite Shunt/ Mainstream Deammonification 25

26 Approaches to Mainstream Nitrite Shunt/ Deammonification 26

27 Strass WWTP Single Stage Full Scale Mainstream Nitrite Shunt/ Deammonification 27

28 Strass WWTP Single Stage Full Scale Mainstream Nitrite Shunt/ Deammonification 28

29 HRSD Mainstream Nitrite-Shunt + Anammox Polishing 29

30 HRSD Mainstream Nitrite-Shunt + Anammox Polishing Brown and Caldwell 30

31 HRSD Mainstream Nitrite-Shunt + Anammox Polishing Nitrogen removal in nitrite-shunt Anammox Polishing 31

32 Presenter contact information Jose Jimenez Ph.D., P.E.