Biodegradable pollutants are natural organic substances that can be broken down by biological processes into simple, non-toxic products. These processes are carried out by microorganisms, such as bacteria and fungi, which are known as decomposers. While biodegradable pollutants can break down naturally, they are still not considered safe in water systems because their decomposition process can rapidly deplete oxygen levels in the water, leading to issues like fish kills, disrupt the ecosystem balance, and potentially harbour harmful pathogens if not managed properly; essentially, the rapid breakdown can create a high demand for oxygen by decomposing microbes, leaving less available for other aquatic life.