Anaerobic nitrifier denitrification for energy recovery and reuse

ANDERRs Nitrogen Conversion Success

NO

₂ NH₄+

NO

₃

-NH

₄+

Partial

Aeration

14 Day Reaction Period

 100% Ammonia

Removal

 80% as Nitrite

 < 1% as Nitrate

 20% Nitrite Removal

as Nitrous Oxide*

Sequencing Batch Reactor

*

Nitrifier Denitrification

Test Reactor

16 Day Reaction Period

 50% Nitrite

Removal as Nitrous

Oxide*

N₂0

Anaerobic Nitrifier Denitrification for Energy Recovery and Reuse

Ethel Coolidge

and Linda Figueroa

‡

‡

_{Department of Civil and Environmental Engineering, Colorado School of Mines}

Background

Anaerobic Carbon and Nitrogen to Energy

Energy Positive System Diagram

References

Conclusion

Future

Work

1. UNEP 2013. Drawing Down N2O to Protect Climate and the Ozone Layer. A UNEP Synthesis Report. United Nations Environment Programme (UNEP), Nairobi, Kenya.

2. Wrage, N., Velthof, G. L., van Beusichem, M. L., Oenema, O. Role of Nitrifier Denitrification in the production of nitrous oxide. Soil Biology & Biochemistry. 2001, 33 (2001) pp 1723-1732.

3. Scherson, Y. D.; Woo, S. G.; Criddle, C. S. Production of Nitrous Oxide From Anaerobic Digester Centrate and Its Use as a Co-oxidant of Biogas to Enhance Energy Recovery. Environ. Sci. Technol. 2014, 48 (10), pp 5612-5619.

• Nitrous oxide (N₂O) has a global warming potential (GWP) 310 times greater than CO₂.

• Global N₂0 emissions are expected to nearly double by 2050 unless nitrogen use efficiency is achieved.

• Sequencing Batch Reactor

 Continue performance monitoring • Anoxic Experiments

 Headspace analysis to confirm N₂O production

• Further Optimization of N₂0 production with Genetic Engineering

 Increasing the activity of Nitric Oxide Reductase. Engineer Ammonia-oxidizing bacteria with Ammonia Monooxygenase Inactivated.

Alternative Energy Source

• When methane (CH₄) is combusted with N₂O rather than with oxygen the heat of combustion increases by 329 kJ/mol.

CH₄ + 4N₂O  CO₂ + 2H₂0 +4N₂ ΔH ͦ= -1,219 kJ/mol CH₄ + 2O₂  CO₂ + 2H₂0 ΔH ͦ= -890 kJ/mol

• Energy uses for N₂O:

• Monopropellant in rocket engines • Auto racing engine booster

• Biological Nitrogen Removal Process: Ammonia Oxidizing Bacteria (AOB)

• Improving Efficiency of Biological Nutrient Removal (BNR) processes for simultaneous improvement of WWTPs Efficiency and Regeneration of Renewable Sources of Energy:

A. Primary and secondary treatment combined in anaerobic conditions to capture CH₄ for Reuse

B. Anaerobic Nitrifier Denitrification for Energy Recovery and

Reuse (ANDERRs). Optimization of the Nitrifier Denitrification pathway for effluent nitrogen removal and to capture N₂O for

Reuse

• The focus of Current Research on the Mitigation of WWTPs N₂O emissions is on the inhibition of Nitrifier Denitrification.

• Enhancing the Operational Parameters to Promote this N₂O producing pathway, combining anaerobic Primary/Secondary

treatment, and capturing the produced Alterative Energy, has the potential to turn wastewater treatment plants into Energy

Production Plants.

Acknowledgments

Thank you to Linda Figueroa, Ryan Hort, and Lee Landkamer for a summer of inspiration, great advice, and hope for the future. Support for this research was generously provided by the Colorado School of Mines Department of Civil and

Environmental Engineering, the Renewable Energy Materials Research Science and Engineering Center, and the National Science Foundation.

Successful Lab Demonstration of ANDERRs

0 100 200 300 400 500 600 700

10-Jul 12-Jul 14-Jul 16-Jul 18-Jul 20-Jul 22-Jul 24-Jul

Ni tr og en (mM ) Time (day)

Partial Aerobic ANDERRs Nitrogen Conversion

Nitrite

Nitrate

Ammonia

New Cycle -Decant/Refill

NH

₄+

+ 1.5O

₂

 NO

₂-

+ H

₂

O + 2H

+

NH

₄+

_+2NO

2-

 1.5N

2

O + 3H

+

+ 0.5H

2

O

0 400 800 1200 1600 0 2 4 6 8 10 12 14 16 Ni tr og en (m g /L) Time (day)

Anaerobic ANDERRs Nitrogen Conversion

Nitrite

Ammonia

Nitrous Oxide

(Theoretical) ANOXIC NO₂- NH₄+

Anaerobic

Primary/Secondary

ANDERRs

ANDERRs

Anaerobic Digester Biosolids O₂ Thicken

CH

₄

N

₂

0

Tertiary

Reclaimed Water

Energy

Biogas P Recovery

AOB

Anoxic

AOB

Influent

NH

₃

NH

₂

OH

NO

₂ -

_NO

_N

2

O

N

2 Ammonia monooxygenase Hydroxylamine oxidoreductase Nitrite reductase Nitric Oxide reductase Nitrous oxide reductase Nitrification Denitrification

• Approximately 3% of global nitrous oxide emissions come from wastewater treatment plants (WWTPs).

Wastewater Treatment Kandahar International Airport, Afghanistan

N₂0

NO₂

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