Explanation

Eichhornia and certain phytoplanktons have capacity of purification of water. Cells of these plants uptake and accumulate heavy metals and other toxicants of polluted water. Organic pollutants of water like petroleum can be degraded with the help of bacteria Pseudomonas. Beggiatoa is a sulphur bacteria which oxidizes hydrogen sulphide to sulphar. Chlorella and Spirogyra are green algae, which do not help in purification of water.