Advances in Environmental Technology

Advances in Environmental Technology

Enhancing nitrate removal and CO2 fixation in groundwater through microalgal precultivation strategies

Document Type : Research Paper

Author
Department of Biotechnology, Iranian Research Organization for Science and Technology (IROST), P. O. Box 3353‑5111, Tehran, Iran
Abstract
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.

Graphical Abstract

Enhancing nitrate removal and CO2 fixation in groundwater through microalgal precultivation strategies
Keywords
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Volume 12, Issue 4
Autumn 2026
Pages 420-429

  • Receive Date 07 February 2026
  • Revise Date 01 July 2026
  • Accept Date 11 August 2026