Final answer:
Contamination from a septic tank's sewage outfall is best filtered through soil, which acts as a natural purifier, rather than through cavernous limestone which lacks adequate filtration properties.
Step-by-step explanation:
The contamination from the sewage outfall of a septic tank will be filtered if it passes into an area of soil rather than an area of cavernous limestone. This is because soil acts as a natural filter, where the clarified water seeps into the ground and undergoes further purification by bacteria present in the soil. On the other hand, cavernous limestone can have large cracks or spaces that allow for rapid movement of water and contaminants, potentially leading them to quickly reach the groundwater without adequate natural filtration.
Proper sewage treatment is crucial for removing organic matter and killing harmful bacteria. Water pollution can be a significant issue, particularly when wastewater systems are established in the wrong type of soil or are poorly maintained. The goal of treatment processes is to protect water quality and prevent the spread of waterborne diseases, which is why the right soil conditions are essential for filtering effluents from septic systems effectively.