The City of Rockville’s Water Treatment Plant was put into service in 1958 and, at that time, was capable of producing four million gallons per day (MGD) of treated water. The plant was upgraded in 1965 to increase production to eight MGD. In the mid-1990’s additional upgrades to the plant were carried out in order to meet U.S. Environmental Protection Agency (EPA) and Maryland Department of the Environment regulations. Since that time, an average of five MGD per day of raw (untreated) water has been withdrawn from the Potomac River, treated by the water plant and distributed to the City’s water customers. Once at the plant, the water is put through a six-step treatment process to ensure the drinking water meets Safe Drinking Water Act standards. Once treated, the water is sent through a series of underground water lines to your faucet. The river water is treated to remove suspended sediments, algae, parasites, bacteria and metals through the following process: – Water from the Potomac is pumped through a screen to remove large debris such as sticks, leaves and rocks. If algal blooms are present in the raw water withrawn from the River, it is treated with a chemical containing potassium (Potassium Permanganate KMnO4). 
Water from the Potomac is pumped through a screen to remove large debris such as sticks, leaves and rocks. If algal blooms are present in the raw water withrawn from the River, it is treated with a chemical containing potassium (Potassium Permanganate KMnO4).
Water is treated with compounds that make small suspended particles stick together and settle out of the water. This particle conglomerate is removed from the water prior to filtration.
Water is passed through a settling basin or clarifier allowing time for mud, sand, metals and other sediment to settle out.
Water is passed through a dual media (sand and anthracite) filter, which removes many remaining pollutants.
Chlorine is added to the water to kill and/or inactivate any remaining pathogens. Fluoride is added to prevent tooth decay and a rust inhibitor is added to preserve the pipes that deliver the water to homes and businesses.
The treated water is stored in three storage tanks and is gravity-fed to houses and businesses when needed. The water is sampled at the plant, in the distribution system and at the tap in homes and businesses for lead, copper, other potential harmful chemicals, bacteria and residual chlorine.
For more information visit EPA’s Safe Drinking Water Act (SDWA) web page or the State of Maryland Water Supply program. View a full-size PDF of the water treatment process. | 
