Identification of cadmium (Cd2+) bioremediation potential algal species in Beira Lake, Sri Lanka

Abstract

Algae have been shown to be capable of removing a wide variety of pollutants from water, including harmful heavy metal ions. The research gap in the identification of cadmium-degrading algal species in wastewater in Sri Lanka is the lack of comprehensive studies or knowledge specifically focused on this topic in Sri Lanka. While research on wastewater treatment and algal bioremediation exists, there is limited research specifically addressing the identification of algal species capable of effectively degrading cadmium in Beira Lake, Sri Lanka. Algal species growing in Beira Lake, Sri Lanka, were identified in this study, and their potential to remove Cd (II) was studied. Based on morphological characteristics, 21 algae species were identified by using Light microscope and scanning electron microscope. Out of the identified 21 algae species, two algae species of them (Spirulina plantensis and Chlorella vulgaris) were further analyzed for bioremediation against 20-mg/L Cd (II) solutions. For selection of most suitable culture media for algae culturing algal culture media were selected as the most suitable algal culture media for algae culturing and growth than the MS medium and artificial seawater medium. The mean of Cd (II) removal abilities/percentages of algae species varied: Algae mix (Spirulina plantensis, Chlorella vulgaris, Beira Lake wastewater) > Spirulina plantensis sp. > Beira Lake Wastewater > Chlorella vulgaris sp. Within 72 hours, Spirulina plantensis algae demonstrated higher tolerance for Cd (II) concentrations of 20 mg/L than Chlorella vulgaris algae and Beira Lake effluent. Biofilm formation was demonstrated by Spirulina plantensis algae species and Beira Lake wastewater algae species. Furthermore, the one-way ANOVA and Tukey tests revealed a positive correlation between algae species' ability to remove Cd (II) and live cell percentage. In conclusion, Spirulina plantensis algae species showed high tolerances for Cd (II) and demonstrated strong Cd (II) removal abilities. As a result, Spirulina plantensis algae species and a combination of algae species (Spirulina plantensis, Chlorella vulgaris, Beira Lake wastewater) can be identified as promising sorbents for the development of ecologically acceptable, and appropriate adsorption systems for the removal of Cd (II) from aqueous solutions.