Answer: By introducing pollutant-consuming microorganisms.
Bioremediation is a process which belongs to the branch of biotechnology. It deals with the application of living organisms like microbes, plants, plant enzymes to degrade or utilize the organic waste from contaminated ground water, sewage sources, soil and other polluted sites.
The introduction of microorganisms will lead to the consumption of the organic waste present in water of lake or other source and sewage waste management. Hence, it will improve the quality of water and will help in getting rid off the sewage waste.