Ammonia Electrolysis in a Municipal Wastewater Treatment Plant
Authors: Botte Gerardine G 
Published: February 2020

Background

Ammonia emissions into air (ambient ammonia) and water represent an environmental challenge. Ambient NH3 not only contributes to inorganic PM2.5 (particulate matter with an aerodynamic diameter of less than 2.5 microns) directly but also plays an important role in secondary organic aerosol formation by interacting with gaseous phase organic acids and forming condensable salts.1 Various industries and other operations are considered ammonia emitters. These are fertilizer manufacture industry, livestock management, coke manufacture industry, fossil fuel combustion, and refrigeration methods.2 On the other hand, ammonia emissions in water are associated with environmental problems such as algae bloom.3

Methods for the removal of ammonia include biological and physicochemical methods. Currently, wastewater treatment solutions for ammonia (biological and chemical treatments) consume a significant amount of energy (4.5 to 50 kWh per kg of ammonia removed); have high operational costs ($4 per lb of ammonia removed); require significant capital investment ($658,000 per MGD –million gallons per day- for retrofit and $9,000,000 per MGD for grassroots plants –new constructions), are not easily adaptable to tighter emissions regulations; take a long time to start-up (in order for the micro-organisms to stabilize in the biological reactors), and are large in size.4

An alternative for efficient ammonia water treatment is the ammonia electrolysis technology. This technology has been under development at the Center for Electrochemical Research (CEER) at Ohio University for the treatment of wastewater.5-11 In this process, the direct oxidation of ammonia takes place at the anode of the electrochemical reactor in alkaline media producing nitrogen gas, while hydrogen is produced at the cathode of the cell. Ammonia can be removed from water while energy can be recovered from the hydrogen by-product produced.

In this work, we developed a mobile system that was tested at the Athens Ohio Wastewater Treatment Facility to evaluate the performance of the process in a municipal wastewater treatment plant.

Results

A partnership between CEER and the City of Athens Ohio Wastewater Treatment Plant12 was established to evaluate and demonstrate the performance of a pilot scale ammonia electrolysis system. The components of the system were installed in a mobile trailer and connected to the water treatment plant as an electrical appliance (with minimum plumbing and direct connection to power). The water treatment system was tested and evaluated at different intervals totalizing over six months of operation. Successful removal of ammonia was demonstrated. Energy from the hydrogen was recovered using a fuel cell. Further results will be presented at the meeting.

References

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City of Athens Ohio Wastewater Treatment Plant, http://www.ci.athens.oh.us/index.aspx?NID=225 (accessed April 2017).