What is the primary function of algae in sewage treatment?

In sewage treatment processes, algae play a crucial role in facilitating the oxygenation of the water. They perform photosynthesis, using sunlight to convert carbon dioxide and water into glucose and oxygen. This process not only contributes to the reduction of carbon dioxide in the water, making it more hospitable for aquatic life, but also significantly increases the dissolved oxygen levels. Higher oxygen levels are essential for the survival of aerobic microorganisms that break down organic pollutants in the sewage, thereby enhancing the overall efficiency of biological treatment processes.

Additionally, algae contribute to nutrient removal, particularly nitrogen and phosphorus, by assimilating these nutrients into their biomass, further improving water quality. This synergy between algae and microorganisms fosters a balanced ecosystem that is vital for effective sewage treatment.

In contrast, the other choices refer to functions that are less characteristic of algae in conventional sewage treatment. The removal of heavy metals, production of methane gas, and filtration of solids are typically handled by different processes or organisms within wastewater treatment systems, such as chemical treatments, anaerobic digestion or mechanical filtration, rather than the primary function of algae.