Enhancing nitrate removal and CO_۲ fixation in groundwater through microalgal precultivation strategies

Nitrate contamination of groundwater poses serious risks to drinking water safety, particularly in agriculturally impacted regions, while conventional treatment technologies remain costly and energy intensive. This study evaluates microalgae-based nitrate removal from groundwater, with particular emphasis on the role of precultivation strategy in controlling nitrate removal kinetics, biomass productivity, and CO۲ fixation. Chlorella vulgaris and Scenedesmus sp. were precultured in Blue-Green ۱۱ and Bold’s Basal Medium and subsequently cultivated in nitrate-contaminated groundwater (۵۰ mg NO۳⁻–N/L) using photobioreactors. Both species effectively removed nitrate; however, treatment performance was strongly dependent on species and precultivation medium. BG-۱۱–precultured Scenedesmus sp. demonstrated the highest and fastest nitrate removal, reducing NO۳⁻–N below the drinking water standard (۱۰ mg/L) within ۷۸ h and achieving ۹۹% removal after ۹۶ h. BG-۱۱–precultured Chlorella vulgaris reached ۸۳.۴% removal over the same period. BBM-precultured Scenedesmus sp. also achieved high nitrate removal (۹۶%), but with slower kinetics, while BBM-precultured Chlorella vulgaris showed the lowest removal efficiency (۸۷.۸%). Enhanced nitrate removal was directly associated with increased biomass accumulation and CO۲ fixation, with BG-۱۱–precultured Scenedesmus sp. attaining the highest biomass (۰.۴۵ g/L) and CO۲ fixation rate (۲۰.۶۸ g/L/d). This study demonstrates that the precultivation strategy is a critical control parameter for microalgal groundwater remediation and identifies BG-۱۱–conditioned Scenedesmus sp. as a highly effective candidate for integrated nitrate removal and carbon sequestration in real groundwater systems.

کلیدواژه ها:

Microalgae ، Nitrate removal ، Groundwater treatment ، CO₂ fixation ، Precultivation