Algal-bacterial process biotechnology is a recent low-cost method toward toxic pollutant removal from wastewater that has received more attention in the present scenario. The pollutants are mainly categorized into inorganic, organic, radioactive, acid/base, etc. The water pollutants mainly include SO2 from power plants, chemical waste, fertilizers from agricultural use, oil spillage, silt, harmful pesticides, detergents, harmful compounds in cosmetics, pathogenic bacteria from livestock operations and food processing wastes, and chemical compounds found in cosmetics products, effluent outfalls from factories, refineries, waste treatment plants, contaminants from improper disposal of industrial wastes running through rainwater, etc. The proper pretreatment of wastewater needs to be done before disposal to the water bodies unless it would cause serious damage to our entire ecosystem. Algae, mostly behaving as water-purifying agent acting as pollution indicator, can act as a better alternative toward bioremediation through low-cost approach. Due to certain limitations in the algal cell during toxic pollutant accumulation, sometimes it can remediate contaminants up to a certain level. So another emerging concept of algal-bacterial symbiotic system, a less energy consumption technology, was developed which gained much attention toward wastewater treatment in the present scenario. Introduction of cost-effective algal-bacterial consortia treatment technology is reported to treat toxic wastewater effluents from municipal, domestic, industrial, and agricultural activities by using many special unicellular microalgae and pollutant-specific-degrading bacteria. It has been found from recent studies that two important factors such as selection of suitable strain as well as cultivation are responsible for biodegrading toxic chemicals and compounds such as polycyclic aromatic hydrocarbons, phenolics, and organic solvents. The organic compounds released after algal photosynthesis can ultimately become a food source for a variety of heterotrophic microbes. The growth-promoting substance production by bacteria can promote microalgal growth, whereas few bacteria can promote algal growth by photosynthetic oxygen tension reduction inside the algal cell, e.g., Pseudomonas diminuta and P. vesicularis. The wastewater can be treated in an open system, i.e., by the construction of artificial ponds, or closed system, i.e., using a bioreactor. From the available reports, it was found that the algal-bacterial consortium may include mainly microalgae and bacteria, e.g., Flavobacteriia, Gammaproteobacteria, Bacteroidia, and β-proteobacteria. The harmful dissolved methane in anaerobically treated wastewater can effectively be treated by the methane-oxidizing bacteria and algae. It can be concluded that the conventional algal-bacterial system treatment technology acts as a natural biological treatment method as a viable alternative and is of great importance for achieving good wastewater treatment performance as well as the reduction in energy consumption cost.
Algal-bacterial culture system Wastewater treatment Toxic pollutants Bioreactor Low-cost alternative technology
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