This document discusses sources of water supply, water pollution, and methods of water purification. It describes the main sources of water as rainwater, surface water, groundwater, and seawater. Surface water sources include reservoirs, rivers, and tanks, while groundwater sources are wells and springs. Water pollution can be from urbanization, industry, biology, and chemicals. Purification methods on small and large scales include boiling, chemicals, filtration, slow sand filtration, and rapid sand filtration. The goal is to prevent waterborne diseases by purifying water.