Hydrothermal liquefaction aqueous phase mycoremediation to increase inorganic nitrogen availability.

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Citation abstract

Hydrothermal liquefaction aqueous phase (HTL-AP) is a waste product from a thermochemical process where wet biomass is converted into biocrude oil. This nutrient-rich wastewater may be repurposed to benefit society by assisting crop growth after adequate treatment to increase inorganic nitrogen, especially NO 3 -. This study aims to increase HTL-AP inorganic nitrogen, specifically NH 3 /NH 4 + and NO 3 -, through fungal remediation for further use in hydroponic systems. Trametes versicolor, a white-rot fungus known for degrading a range of organic pollutants, was used to treat a diluted (5 %) HTL-AP for 9 days. No fungal growth was observed, but T. versicolor activity was suspected by laccase activity throughout cultivation time. NO 3 - -N and NH 3 /NH 4 + -N increased by 17 and 8 times after three days of fungal treatment, which was chosen as the appropriate time for HTL-AP fungal treatment as it resulted in the highest concentration of NO 3 - -N. The addition of nitrifying bacteria to the fungal treatment resulted in a twofold increase in NO 3 - -N concentration compared to the fungal treatment alone, indicating an enhancement in treatment efficacy. COD decreased by 51.33 % after 24 h, which may be related to the fungus' capacity to reduce the concentration of organics in the wastewater; nonetheless, COD increased in the following days, which may be related to the release of fungal byproducts. T. versicolor shows promise as a potential candidate for increasing inorganic nitrogen in HTL-AP. However, future studies should primarily address HTL-AP toxicity, reducing NH 3 /NH 4 + -N while increasing NO 3 - -N, and hydroponics crop production after fungal treatment.