Q1: The factor responsible for purification of sewage in river is

ANS:E - All the above.

1. Hydrology: Hydrology refers to the study of the movement, distribution, and quality of water on Earth. In the context of sewage purification in rivers, hydrology plays a crucial role in diluting and transporting sewage effluent downstream. Adequate flow rates and sufficient water volume help in dispersing and diluting pollutants from sewage, thereby reducing their concentration and impact on aquatic ecosystems.
2. Dissolved oxygen in water: Dissolved oxygen (DO) is vital for aquatic life and the self-purification of rivers. Aquatic organisms, such as fish and bacteria, rely on dissolved oxygen for respiration and decomposition processes. Sewage and organic pollutants can deplete dissolved oxygen levels in rivers, leading to hypoxic (low oxygen) conditions that harm aquatic life. Monitoring and maintaining adequate dissolved oxygen levels in rivers are essential for supporting healthy ecosystems and facilitating the natural breakdown of organic matter.
3. Temperature: Temperature influences the rate of biological and chemical reactions in aquatic environments. Warmer temperatures generally increase the metabolic rates of aquatic organisms and microbial activity, which can enhance the decomposition of organic matter and the self-purification capacity of rivers. However, excessively high temperatures can stress aquatic organisms and reduce dissolved oxygen solubility, negatively impacting water quality and ecosystem health.
4. Turbulence: Turbulence refers to the chaotic and irregular movement of water in rivers, which can result from various factors such as channel geometry, flow velocity, and obstructions. Turbulence helps in mixing and oxygenating water, facilitating the diffusion of gases like oxygen and carbon dioxide. It also aids in the dispersion and dilution of pollutants, promoting the natural self-cleaning processes of rivers.