Heavy metals (copper and iron) and nutrients (nitrate and phosphate) removal from aqueous medium by microalgae Chlorella vulgaris and Scendesmus obliquus, and their biofilms.

Microalgae have been discovered as an environmental-friendly and cost-effective solution for heavy metal treatment issues. This study illustrated the bioremediation of two heavy metals (e.g. copper and iron) and nutrients (e.g. nitrate and phosphate) uptake by freshwater microalgae Chlorella vulgaris (C. vulgaris) and Scendesmus obliquus (S. obliquus), and their 50-50% mix culture under the suspension and biofilm conditions. After one week of culture in 1L Erlenmeyer flasks, under the Organization for Economic Co-operation and Development (OECD) guideline, various concentrations of copper and iron were added to the culture bioreactors and their concentrations changes were studied. The results obtained showed that C. vulgaris, S. obliquus, and mix culture removed 98.25-99.9%, 98.75-99.1%, and 98.61-99.9% of copper and 90.22-94.05%, 85.68-99.19%, and 91.67-97.85% of iron, respectively. The results suggested that copper has more toxicity effects than iron. C. vulgaris showed to be the most vulnerable among cultures. S. obliquus showed to be more resistant to copper and iron stress situations. Mix culture showed better efficiency in iron uptake. It also demonstrated that there is a limit to nitrate uptake. Increasing heavy metal concentrations may increase nutrient uptake as long as it doesn't reach a toxic amount. Also, biofilm structure showed an effective role in heavy metal resistance.