Solution: Domestic sewage is the waste generated by households, including waste from the toilet, kitchen, laundry, and other sources. It comprises disease-causing germs, suspended solids (clay, silt, sand), colloidal matter (bacteria, plastic, cloth fiber, feces), and dissolved matter (phosphate, nitrate, ammonia, sodium, calcium). Organic wastes from sewage entering aquatic bodies provide food for microbes such as bacteria and algae, encouraging these microbes to grow and increase their population. They need nearly all of the dissolved oxygen for their metabolism, causing the Biological Oxygen Demand (BOD) levels in river water to rise, resulting in the mortality of aquatic organisms. Furthermore, nutrients in water stimulate planktonic algal development, resulting in an algal bloom, which lowers water quality and increases fish mortality.