Electrolysis of post hydrothermal liquefaction wastewater for cyclic nitrogen conversion for hydroponics

Post hydrothermal liquefaction wastewater (PHW) is the aqueous product of a thermochemical conversion process and its nutrients’ have been previously recycled for algal growth and plant growth, but due to the potentially toxic compounds present, the reutilization of the wastewater is limited. Since some treatments may decrease the concentration of nutrients useful for plant growth, a tertiary treatment that can mineralize organic forms of nitrogen into inorganic forms of nitrogen such as nitrate NO3-, and nitrite NO2- is necessary to add value to the high volume of wastewater. This work utilized an electrochemical reactor to investigate the response of PHW to the electrolysis process to enhance the accumulation of NO3- in the PHW by converting the available cyclic nitrogenous compounds. To test the effectiveness of increasing the concentration of inorganic forms of nitrogen in the PHW an electrochemical method was utilized in which different current densities were applied to conductive materials to breakdown organic materials in the wastewater inside an electrochemical cell. Through electrolysis, the NO3- content increased 24 times and 30 times in the PHW with the utilization of the BDD anode and the DSA anode respectively. The current density range that enabled the highest production of nitrate was between 10 mA/cm2 -30 mA/cm2. The higher current densities enabled the removal of organic carbon compounds in the PHW utilizing the BDD anode during the first five hours of the experiment achieving up to 71% of removal. On the other hand, Graphite enabled a 94% removal of nitrogen compounds without formation of nitrate. With the utilization of a model compound called 2-pyrrolidinone, data showed that nitrogen cyclic compounds were converted into inorganic nitrogen forms through oxidation through electrolysis by increasing the NO3- content 28 times utilizing the BDD anode. To utilize this treatment as a future tertiary treatment, it is suggested to utilize the most resistant conductive anode material (BDD) for nitrate formation through electrolysis or carbon removal by adjusting the current density in-put. Graphite has the potential to achieve complete mineralization of nitrogen compounds/ denitrification of the PHW. As it was possible to achieve an increase of NO3- in a low nitrogen content PHW, electrolysis has the potential to be a promising tertiary water treatment method for PHW.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Agricultural & Biological Engr

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2023

Author dc:creator

• Bogarin Cantero, Barbara Camila

Contributors dc:contributor

• Zhang, Yuanhui
• Davidson, Paul
• Bhattarai, Rabin

• Anode
• Inorganic Nitrogen
• Current Density
• Cathode
• Electrolysis
• Nitrate
• Post-hydrothermal Liquefaction Wastewater
• Nitrogen Cyclic Compound

Statement dc:rights

• Copyright 2023 Barbara Camila Bogarin Cantero

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/120475

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F120475