Controlling Eutrophication of Aquaculture Production Water Using Biochar: Correlation of Molecular Composition with Adsorption Characteristics as Revealed by FT-ICR Mass Spectrometry

This study aims to construct a novel and sustainable approach for remediating aquaculture-generated water contamination using various engineered biochars. Particularly, this study focuses on capturing nitrogen and phosphorus from downstream water of commercial fish farms in Magic Valley, Idaho, containing approximately 2.26 mg/L of nitrogen and 0.15 mg/L of phosphorous. The results indicate that the proposed approach can improve downstream waters by adsorbing micronutrients (e.g., nitrogen-ammonia, nitrate-n + nitrite-n, and total phosphorus). Water treatment time and biochar pH are two key parameters strongly associated with adsorbed compounds. Molecular-level characterization of solvent-extracted organics from biochar materials (before and after water treatment) suggests increased levels of highly oxygenated molecules as a function of increasing water treatment time. Also, the results show the enrichment in organic species with higher molecular weight and increased double bond equivalents, with a compositional range similar to that of dissolved organic matter. Upon water treatment, extracted organics revealed higher abundances of compounds with higher H/C and O/C ratios. The engineered biochars, after water treatment, can be reused as nutrient-rich fertilizers. This study concluded that the engineered biochars could sequester more nitrogen and phosphorous over time. Also, the proposed approach can simultaneously increase fish production capacity and support the aquaculture industry in different regions by improving water quality and enabling aquaculture expansion.