Which type of soil aids significantly in the purification of water?

Clay plays a crucial role in the purification of water due to its fine particles and high plasticity, which allow it to effectively filter impurities and contaminants. When water passes through clay, its small pore spaces inhibit the movement of larger particles and pathogens, trapping them and thus enhancing the purity of the water. The ability of clay to retain water can also aid in removing soluble pollutants through chemical processes such as adsorption, where contaminants adhere to the clay particles.

In contrast, while sand, silt, and gravel can contribute to the filtration process, they do not possess the same level of effectiveness in removing pathogens and fine particles as clay does. Sand has larger pore spaces that may allow some contaminants to pass through, and gravel typically serves more as a structural component in filtration systems rather than a purifying agent. Silt, although finer than sand, doesn’t have the adsorption capacity of clay and can still let smaller pathogens slip through.