Treating water to meet the standards of the Safe Drinking Water Act involves a number of steps, most of which involve chemicals. Whether the water source is groundwater (wells) or surface water (rivers, lakes, streams), the same general steps apply but there is a difference in the chemicals used. The specific chemical chosen for a step in the process will largely be determined by cost and the makeup of the particular water source. (Desalination of seawater for drinking purposes is a different process and will not be discussed here).