Harnessing Chlorella vulgaris for Mucilage Mitigation and Wheat Growth on Fluvisol: A Study on Wastewater Treatment Efficacy

Abstract This study aimed to determine the phytoremediation efficiency of Chlorella vulgaris microalgae as a circular bioeconomic approach using wastewater samples from deep-sea discharge points at the Ambarlı and Pasakoy Wastewater Treatment Plants (WWTPs) in Istanbul, where mucilage formation has been a significant concern Furthermore, the potential of the produced microalgae biomass as a biofertilizer for wheat ( Triticum aestivum L.) growth on fluvisol was assessed.Wastewater samples were collected from each WWTPs for analysis. Chlorella vulgaris was cultivated in BG-11 medium and used to evaluate nutrient removal efficiency over time. A greenhouse experiment was conducted to assess the effects of Chlorella vulgaris biomass as a biofertilizer on wheat growth, with treatments including microalgae and Diammonium Phosphate (DAP) fertilizer combinations. The results indicated that Chlorella vulgaris achieved the highest nitrogen (N) reduction (43.65% and 17.63%) within the first 30 min at the respective stations, while the maximum phosphorus (P) removal (75.42% and 19.16%) occurred at the end of 300 min. A 30-minute treatment period was found optimal for nutrient removal, after which the greenhouse experiment commenced. In the greenhouse experiment, microalgae treatments (0.01 g kg⁻¹ and 0.04 g kg⁻¹) combined with DAP fertilizer (Chemical Fertilizer, CF: 150 kg ha⁻¹) significantly improved soil properties and plant growth parameters. However, these treatments also caused an increase in heavy metal content in soils and plants.The findings highlight that while biomass from wastewater treatment is a promising biofertilizer alternative, pre-treatment to remove adsorbed heavy metals is crucial to minimize environmental risks and unlock its agricultural potential.