Bioremediation of Municipal Sewage Using Potential Microalgae

Rapid urbanization has resulted in an increase of municipal sewage discharge, which, in turn, has added load and cost to the conventional water treatment processes. The composition of municipal sewage mostly contains natural inorganic and organic minerals as well as synthetic compounds. Microalgae utilize these wastes as nutritional sources and hence could be used as an interesting step to improve the quality of sewage. Though there are some natural algal flora existing in sewage, few selective and efficient strains could be used in this purpose. They are non-pathogenic and have the potential to eliminate pathogens by competitive growth. Moreover, they could reduce biological and chemical oxygen demand of water as well as remove heavy metals by algal metabolism. Unlike conventional methods, it requires low operational and maintenance cost and no use of hazardous chemicals for water treatment. Additionally, the biomass could be utilized to generate value-added products such as bioenergy, pharmaceuticals, nutraceuticals, etc. However, land requirement, difficulties in the growth of pure strains, variation in environmental factors, eutrophication, self-shading and difficulties in the harvesting of biomass are some of the bottlenecks of this process. With recent advances in scientific knowledge, sophisticated techniques and environmental awareness, microalgae could offer a sustainable, environment-friendly solution to treat wastewater which could be further enhanced by the addition of other organisms and aquatic plants.