Heavy metal pollution of river water and eco-friendly remediation using potent microalgal species

Pollution of rivers is mainly caused by anthropogenic activities such as discharge of effluent from industrial facilities, maintenance of sewage/effluent treatment plants, and dumping of solid waste on river banks. This study dealt with the pollution issues of the Cooum River in the well-known city of Chennai in South India. Water samples from 27 locations were collected and analyzed for 12 elements, including Ba, B, and Al, as well as heavy metals such as Pb, Cr, Mn, Fe, Co, Ni, Cu, Zn, and Cd. The samples showed levels of these elements that exceeded World Health Organization recommendations. Pearson correlation analysis revealed the inter-dependency among elements, and the contribution of each element based on factor loadings showed its percentage contribution compared to others. Water samples from six significant locations were chosen for remediation with three algae: Chlorella vulgaris, Scenedesmus dimorphus, and Phormedium sp. The uptake of pollutants led to the continuous growth of algae during the incubation period of 15 d, effectively removing heavy metals from the river water. The increasing levels of algal counts and the chlorophyll a content confirmed the algal growth during the incubation period, followed by a declining stage after the incubation period. The scanning electron microscopic images of algae before and after the remediation showed no remarkable modification of morphological patterns. This study showed that the uptake of heavy metals using algae is an effective water pollution remediation measure, making the process practicable in the field on a large scale in the near future.