Iranian Research Organization for Science and Technology Advances in Environmental Technology 2476-6674 12 4 2026 10 01 Enhancing nitrate removal and CO2 fixation in groundwater through microalgal precultivation strategies 420 429 1721 10.22104/aet.2026.8135.2287 EN Fariba Rezvani Department of Biotechnology, Iranian Research Organization for Science and Technology (IROST), P. O. Box 3353‑5111, Tehran, Iran Journal Article 2026 02 07 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 CO2 fixation. Chlorella vulgaris and Scenedesmus sp. were precultured in Blue-Green 11 and Bold’s Basal Medium and subsequently cultivated in nitrate-contaminated groundwater (50 mg NO3⁻–N/L) using photobioreactors. Both species effectively removed nitrate; however, treatment performance was strongly dependent on species and precultivation medium. BG-11–precultured Scenedesmus sp. demonstrated the highest and fastest nitrate removal, reducing NO3⁻–N below the drinking water standard (10 mg/L) within 78 h and achieving 99% removal after 96 h. BG-11–precultured Chlorella vulgaris reached 83.4% removal over the same period. BBM-precultured Scenedesmus sp. also achieved high nitrate removal (96%), but with slower kinetics, while BBM-precultured Chlorella vulgaris showed the lowest removal efficiency (87.8%). Enhanced nitrate removal was directly associated with increased biomass accumulation and CO2 fixation, with BG-11–precultured Scenedesmus sp. attaining the highest biomass (0.45 g/L) and CO2 fixation rate (20.68 g/L/d). This study demonstrates that the precultivation strategy is a critical control parameter for microalgal groundwater remediation and identifies BG-11–conditioned Scenedesmus sp. as a highly effective candidate for integrated nitrate removal and carbon sequestration in real groundwater systems.

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