Water Treatment Process

To ensure that your drinking water is always safe, a process is used to treat millions of gallons of raw water that arrive daily at the two water treatment facilities serving Mesa. 

The City and its water treatment plants must meet rigorous standards established by the Environmental Protection Agency and the Arizona Department of Environmental Quality (ADEQ), and must be free of coliform bacteria. The Brown Road Water Treatment Plant (BRWTP) is capable of processing 72 million gallons per day, and the facility is operated by ADEQ-certified operators. The raw water for the BRWTP comes from the  Central Arizona Project. The City also gets a portion of its drinking water from the Val Vista Water Treatment Plant, which is owned jointly by the cities of Phoenix and Mesa. Salt River Project supplies the raw water to Val Vista.

The raw water is processed according to the following steps: 

Taste and Odor Removal
Taste and odors occur in the water in the late summer or fall.  Naturally occurring organic matter decomposes in the raw water source, and causes taste and odors.  Carbon or potassium permanganate is added to the water to remove or reduce unpleasant taste and odor.    


Disinfection

As the water enters the treatment plant, chlorine dioxide is added for disinfection.  Disinfection destroys bacteria and viruses.  Chlorine is added to the water as it leaves the treatment plant to ensure that the water that enters your home is safe to drink.  


Flocculation


flocculation basin

Aluminum sulfate (alum) is mixed into the water.  The alum causes small impurities to stick together and form "floc". 


Sedimentation

settling tank

The floc settles to the bottom of the basin, and is removed.  Chlorine is also added during this process for further disinfection.  


Filtration

filters

Water flows through filters that are made of layers of sand and coal.  These filters remove the fine particles that did not settle out during sedimentation.


Final Backwash

final backwash

To remove particles from the filters, the filters are backwashed to remove sediment every 60 - 72 hours.  Approximately 200,000 gallons of water is used to backwash a filter.  This water is then recycled back into the raw water supply.  


Fluoridation
The raw water has naturally occurring fluoride, however, the Center for Disease Control (CDC) recommends an optimum fluoride level.  This requires the city to add supplement fluoride.  


Storage

water storage tank

Water is stored in reservoirs throughout the City.  The distribution system brings the water to consumers.