The presence of these substances in drinking water does not necessarily mean that the water poses a health risk. Each source of water, be it lake water or groundwater, has its own unique characteristics and the type of treatment varies. The treatment process uses chemical and physical means to remove impurities from municipally supplied water. Lake sources rely on long, deep intakes to obtain the best possible raw water. Raw water is screened before the addition of chemicals called coagulants that cause very small particles to group together so they can be more easily removed.
Sedimentation allows larger particles to settle out before filtration.
Filters remove finer levels of impurities. Chlorine is used to remove any hazardous bacteria. Groundwater is naturally filtered as it moves through the earth. It too requires the use of chlorine as a disinfectant. As well, groundwater commonly has higher levels of dissolved minerals like iron and manganese.