The Role of Microalgae in Wastewater Treatment

Cyanobacteria, also named as blue-green algae, are the only known prokaryotes capable of oxygenic photosynthesis. Treatments of both industrial and domestic wastewater through physico-chemical methods are invariably cost-intensive to be employed in industries especially in developing and underdeveloped countries. Therefore, in recent years, the importance of low-cost biological wastewater treatment by using the cyanobacteria compared to the conventional wastewater treatment plants has attracted the attention of the researchers. It has been reviewed that there is a reduction of about 70% calcium, 46% chloride, 100% nitrate, 88% nitrite, 100% ammonia, 92% total phosphorus, 12.5% magnesium, 85% BOD and 85% COD from different wastewater by application of different species of cyanobacteria. Further, the metals like Cu, Al, Cd, Zn, Hg, Cr, Ni, Pb, etc. play an important role in the growth and development of cyanobacteria under laboratory culture conditions. Toxicity on growth, effect on photosynthesis, damage of cell, algaecide effect, toxicity at sublethal concentration, ultrastructural changes, cell division and movement, changes in cellular components, etc. are some of the observations in cyanobacteria under laboratory bioassay for metal toxicity study. Besides these, cyanobacteria also show growth effect when grown in wastewater containing different types of pesticides, herbicides and other toxic chemicals. In the present review, an attempt has been made to review the role of different