Which filtration method utilizes a large surface area for effective filtering?

The correct answer is Slow Sand Filtration. This method involves a filter bed composed of fine sand, which is designed to remove impurities from water as it slowly percolates through the sand layer. The large surface area provided by the layers of sand allows for effective biological processes and the capture of particulate matter, leading to high-quality filtration over time.

Slow sand filters operate at a lower flow rate compared to other filtration methods, increasing the interaction time between the water and the sand, which enhances the removal of contaminants through both physical and biological mechanisms. As the water flows through the sand, microorganisms, including bacteria and protozoa, often form a biofilm on the surface of the sand grains, contributing further to the filtration process and improving water quality.

While other options such as Rapid Sand Filtration and Ultra Filtration are effective methods, they do not rely on the same extensive surface area dynamics and biological activity as Slow Sand Filtration to achieve water purification. Rapid Sand Filtration, for example, involves a larger volume of sand but functions on the principle of higher flow rates, which limits the contact time for biological treatment.