Greenhouse Gas Emissions From Biological Nutrient Removal at Fields Point

Wastewater Treatment Plant

Elizabeth Brannon1, Serena Moseman-Valtierra1, Ph.D. James McCaughey2

1University of Rhode Island 2Narragansett Bay Commission

Outline 1.  Background

1.  Greenhouse gases 2.  Field’s Point WWTP 3.  Biological nutrient removal at Field’s Point

2.  Methods 1.  Real time greenhouse gas analyzer 2.  Flux calculations

3.  Results/Discussion 4.  Summary 5.  Future work

Greenhouse Gases

GHG GWP CO2 1 CH4 21 N2O 300

Background

•  Contribute to climate change •  Increases since about 1750 are attributed to human activities1

•  Need inventories to determine areas for reduction

Forster et al. 20071

Forster et al. 20071

Field’s Point WWTP Operations

•  Receives combined wastewater and stormwater

•  65 MG CSO storage tunnel •  4 Pumping stations •  45 MGD (170.1 MLD) average •  65 MGD (246 MLD) design average •  123 MGD (756 MLD) primary during

storm events •  Chlorination/de-chlorination •  On-site biosolids gravity thickeners/

offsite biosolids management •  BNR upgrade completed 2013 •  5 ppm total nitrogen discharge limit

May – October

Background

FP  WWTP  

NBC, Facilities2

Necessity of Nitrogen Removal

•  Prior to upgrades WWTPs were responsible for 73% of nitrogen loads into Narragansett Bay3

•  Excess nitrogen loads to the bay can lead to eutrophication which may cause: •  Macroalgae accumulation •  Low oxygen •  Eelgrass decline •  Fish kills – in very extreme cases

•  In 2004 RI legislation was passed to reduce nitrogen loadings from WWTP by 50% 4

•  NBC Field’s Point - Seasonal nitrogen limit of 5 mg/L

Background

University  of  Maryland  Center  for  Environmental  Science  

Biological Nutrient Removal at Field’s Point •  Upgraded 10 existing aeration basins for Integrated Fixed Film

Activated Sludge process •  Hybrid between suspended growth and attached growth •  Came online in March 2013

Background

Integrated Fixed Film Activated Sludge (IFAS)

Advantages •  Increases treatment

capacity in a smaller space •  Increase in effective mixed

liquor concentration without sufficient increase in solids to secondary clarifier

•  Have ability to improve treatment performance by adding media

•  More stable nitrification community due to high attached growth inventory

Disadvantages •  Higher energy demand •  Need to use media •  Hydraulic profile head loss

due to flow through the media screening devices

Pre-­‐Anoxic  Zone   Aerated  IFAS  Zone   Post-­‐Anoxic  Zone  Re-­‐Aera@on  Zone  

Wastewater  Flow  

Plas@c  Media  at  7.8x  

Photo  Credit:  Maria  Briones  

Volume = 0.9 MG Retention Time = 0.3 hours

Volume = 3.6 MG Retention Time = 1.2 hours

Volume = 1.5 MG Retention Time = 0.5 hours

Volume = 0.4 MG Retention Time = 0.1

hours Plastic media:

•  25 mm diameter, 10 mm long •  Reactor fill rate: 52% •  Effective surface area of 500 m2/m3

IMLR  

Pre-­‐Anoxic  Zone   Aerated  IFAS  Zone   Post-­‐Anoxic  Zone  Re-­‐Aera@on  Zone  

Wastewater  Flow  

Denitrifica@on  

Nitrifica@on  

Nitrogen  Fixa@on  

N2  

NH4+  

NO3-­‐  

N2O  

NO3-­‐  

NH4+  

N2  

NH4+  

NO3-­‐  NH4

+   N2  NO3-­‐  

N2O  

N2O  

N2O N2O N2O

Possible CH4 and CO2 Production Background

•  CH4

•  Produced upstream and stripped in aerated tanks5,6

•  Produced in anoxic zones of BNR5,6

•  CO2

•  Heterotrophic bacteria respire in aerobic zones7

Clarifiers at Field’s Point WWTP

RIGIS  

Objectives

1.  Quantify the magnitude of N2O, CH4, and CO2 emissions from BNR at Field’s Point

2.  Examine spatial, daily, and seasonal variability in the emissions

3.  Investigate potential relationships between tank conditions and N2O, CH4, and CO2 emissions

Methods Measurements 2x a month June 2014 – January 2015: •  N2O, CO2, CH4 fluxes •  Dissolved N2O, CO2, CH4 concentrations •  Ammonium •  Nitrate •  Nitrite •  COD •  Air temperature •  DO profile •  TKN

GHG Measurements Methods

Picarro cavity ring down spectrometry (CRDS) Analyzer

Chamber deployed in post-anoxic zone

Flux Calculations Methods

Slope = ppm/s Ideal Gas Law: PV = nRT Fick’s Law: Flux = dC/dt x (Volume/Area) Flux = mmol m-2 hr-1

y = 0.068x - 1.954 R² = 0.94211

0

10

20

30

40

0 100 200 300 400 500 600

N2O

(ppm

)

Time (seconds)

RESULTS + DISCUSSION

CO2 Results Results  

0

1000

2000

3000

4000

5000

6000

6/30

7/14

7/28

8/11

8/25

9/8

9/22

10/6

10/2

0

11/3

11/1

7

12/1

12/1

5

12/2

9

1/12

Aver

age

CO

2 (m

mol

m-2

hr-1

)

Date

Pre-Anoxic Aerated IFAS Post-Anoxic Re-Aeration

CH4 Results Results

0

20

40

60

80

100

120

140 6/

30

7/14

7/28

8/11

8/25

9/8

9/22

10/6

10/2

0

11/3

11/1

7

12/1

12/1

5

12/2

9

1/12

Aver

age

CH

4 (m

mol

m-2

hr-1

)

Date

Pre-Anoxic Aerated IFAS Post-Anoxic Re-Aeration

Thick Sludge

Appeared

N2O Results

Potential relationships to tank conditions: Aerated IFAS: Internal ML Recycle NO3

-

Re-Aeration: Returned Activated Sludge Flow

0

5

10

15

6/30 7/31 8/31 9/30 10/31 11/30 12/31

N2O

Flu

x (m

mol

m-2

hr-1

)

Date

Pre-Anoxic Aerated IFAS Post-Anoxic Re-Aeration

Results  

Results + Discussion

Study  %  of  TKN  emi7ed  as  N2O  

Min.   Max   Average  

This  Study   0.001   0.195   0.064  

Other  Studies8-­‐13   0.000   1.800   NA  

How does Field’s Point Compare?

Study  g  CH4  m-­‐2  d-­‐1  

Min.   Max   Average  

This  Study   0.01   93.00   3.55  

Other  Studies6,14   0.11   7.50   NA  

Study  g  CO2  m-­‐2  d-­‐1  

Min.   Max   Average  

This  Study   11   6165   1693  

Other  Studies6   79   1862   NA  

Emission Sources at Field’s Point

0 10 20 30 40 50 60 70 80 90

All Other Sources

N2O from Secondary Treatment

CO2 from Secondary Treatment

CH4 from Secondary Treatment

% o

f Tot

al C

O2 E

mis

sion

s

Emission Source

N2O from Secondary Treatment

CO2 from Secondary Treatment

CH4 from Secondary Treatment

Results + Discussion

Summary •  N2O, CH4, and CO2 fluxes are variable •  No season variability but instead single events

with high emissions •  Potential causes of large emission events:

•  CO2: More data needed •  CH4: Thick sludge on Post-Anoxic Zone •  N2O: Internal recycled nitrate and returned

activated sludge flow •  Zones responsible for highest emissions:

•  N2O and CO2: IFAS Aeration Zone and Re-Aeration Zone

•  CH4: IFAS Aeration Zone and Post-Anoxic Zone

Future Work

•  Continue current data collection

•  Investigate potential relationships between tank conditions and GHG emissions

•  Isotope methods to investigate N2O mechanisms

•  Model N2O emissions in aerated zones

•  Measurements from other tanks in the treatment process

•  Compare to other BNR systems

Acknowledgments Adviser: Dr. Serena Moseman-Valtierra Committee: Dr. Jose Amador, Dr. Vinka Craver, Dr. Bethany Jenkins Moseman-Valtierra Lab Members: Melanie Garate, Rose Martin, Ryan Quinn Narragansett Bay Commission: Dave Aucoin, Brendan Cunha, Barry Wenskowicz Craver Lab Members: Maria Briones, Jessica Damicis Funding provided by: Narragansett Bay Commission and USDA Hatch Grant (Moseman Start Up)

Questions?

References 1.  Forster, P., V. Ramaswamy, P. Artaxo, T. Berntsen, R. Betts, D.W. Fahey, J. Haywood, J. Lean, D.C. Lowe, G. Myhre,

J. Nganga, R. Prinn, G. Raga, M. Schulz and R. Van Dorland, 2007: Changes in Atmospheric Constituents and in Radiative Forcing. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

2.  Narragansett Bay Commission (NBC). Facilities. Retrieved April 2, 2014 from:: http://www.narrabay.com/About%20Us/Facilities.aspx.

3.  Pryor, D.; Saarman, E.; Murray, D.; Prell, W. (2007). Nitrogen Loading From Wastewater Treatment Plants to Upper Narragansett Bay. Narragansett Bay Estuary Program Report NBEP-2007-126.

4.  RI DEM. Plan for Managing Nutrient Loadings to Rhode Island Waters.(2005). 5.  Aboobakar, A.; Jones, M.; Vale, P.; Cartmell, E.; Dotro, G. (2014). Methane Emissions from Aerated Zones in a Full-Scale

Nitrifying Activated Sludge Treatment Plant. Water Air Soil Pollution, 225, 1814. 6.  Czepiel, P.; Crill, P.; Harriss, R. (1993). Methane Emissions from Municipal Wastewater Treatment Process. Environmental

Science Technology, 27, 2472-2477. 7.  Grote, B. (2010). Biological Nutrient Removal (BNR) Technology in New and Upgraded WWTPs. 35th Annual Qld Water Industry

Operations Workshop. 8.  Ahn, J.; Kim, S.; Park, H.; Rahm, B.; Pagilla, K.; Chandran, K. (2010). N2O Emissions from activated sludge process,

2008-2009: Results of a national monitoring survey in the United States. Environmental Science Technology, 44, 4505-4511. 9.  Ahn, J.; Kim, S.; Pagilla, K.; Katehis, D.; Chandran, K. (2010). Spatial and Temporal Variability in Atmospheric Nitrous Oxide

Generation and Emission from Full-Scale Biological Benckiser, G., Eilts, R., Linn, A., Lorch, H., Sumer, E., Weiske, A., Wenzhofer, F. (1996). N2O emissions from different cropping systems and from aerated, nitrifying and denitrifying tanks of a municipal waste water treatment plant. Biol. Fertil. Soils, 23, 257-265.

10.  Foley, J.; Hass, D.; Yaun, Z.; Lant, P. (2010). Nitrous Oxide Generation in Full-Scale Biological Nutrient Removal Wastewater Treatment Plants. Water Research, 44, 831-844.

11.  Kampschreur, M.; Temmink, H.; Kleerebezem, R.; Jetten, M. van Loosdrecht, M. (2009). Nitrous Oxide Emission During Wastewater Treatment. Water Research 43: 4093-4103.

12.  Kimochi, Y.; Inamori, Y.; Mizuochi, M.; Xu, K.; Matsumura, M. (1998). Nitrogen removal and N2O emission in a full-scale domestic wastewater treatment plant with intermittent aeration. Journal of Fermentation and Bioengineering, 86, 202-206.

13.  Sumer, E.; Weiske, A., Benckiser, G., Ottow, J. (1995). Influence of environmental conditions on the amount of N2O released from activated sludge in a domestic waste water treatment plant. Experienctia, 51.

14.  Wang, J.; Zhang, J.; Xie, H.; Qi, P.; Ren, Y.; Hu, Z. (2011). Methane emissions from a full –scale A/A/o wastewater treatment plant. Bioresource Technology, 102, 5479-5485.

EXTRA SLIDES FOR POTENTIAL QUESTIONS

Cavity Ring Down Spectroscopy (CRDS)

Photos courtesy of Piccaro.com

Tank  Conditions  Parameter   Min.   Max.   Avg.  

Water  Temp.  (°C)   11.21   20.12   14.96  

DO  in  IFAS  Zone  (mg/L)   2.86   5.53   4.57  

Internal  recycle  pH   5.39   6.36   6.12  

Zone DO (mg/L)

Surface 10ft. Min. Average Max. Min. Average Max.

Pre-Anoxic 0.17 0.31 0.50 0.10 0.15 0.20 IFAS 4.20 5.18 7.00 4.20 5.18 7.00

Post-Anoxic 0.20 0.42 1.30 0.10 0.15 0.20

Re-Aeration 0.60 0.92 1.40 0.20 0.51 0.80

Statistics  N2O

Date*Zone F(24,35) = 15.6, p-value <0.001 Date F(8,35) = 16.8, p-value < 0.001 Zone F(3,35) = 80.1, p-value < 0.001

CH4 Date F(9,39) = 9.8266, p-value < 0.001 Zone F(3, 39) = 45.4906, p-value < 0.001 Date*Zone F(27, 39) = 4.0537, p-value < 0.001

CO2 Date F (8,35) = 3.1, p-value = 0.005 Zone F (3,35) = 198.2, p-value <0.001 Date*Zone F (24, 35) = 1.0, p-value =0.5313

IFAS Zone and Internal ML Recycle NO3

- (0.8386) Re-Aeration Zone and RAS Flow (0.7823)