As such, the infrastructure Phoenix maintains is substantial. Phoenix’s water and wastewater infrastructure is crucial for maintaining public health, supporting economic development, and ensuring environmental sustainability. Phoenix’s infrastructure is broken into those two main categories: water and wastewater.
Our Infrastructure
Phoenix is one of the largest municipal Water and Wastewater utilities in the western United States.
Water Infrastructure
While raw surface water reservoirs and canals are maintained by either Salt River Project or Central Arizona Project, Phoenix takes the water from those canals and manages and treats it all the way to the tap at your home or business. Phoenix also maintains drinking water wells that supplement the surface water when necessary. Well water enters the distribution system that also connects to your tap, but because well water is already of high quality, it doesn’t need to be treated.
Below is listing of the various components of water infrastructure – some seen, some unseen – that comprise Phoenix’s water infrastructure.
Water Treatment Plants
Phoenix maintains five water treatment plants, with the oldest being built in the early 1950s, and the most recent being completed in 2007, although the older plants have been renovated and modernized over the years. Each plant works in mostly the same manner, following a specific phased approach, even if the technology is slightly different. All water goes through pretreatment, where large particles are removed from the water, then the water goes through a coagulation and flocculation process, where chemicals are added to help the particles clump together and settle, so additional filtration can be achieved. The next phase is filtration, where the water is filtered through granular activated carbon and other filtration media to achieve a degree of clarity. Then the water is disinfected with a small amount of chlorine, then the water is stored in a large reservoir before being sent to the distribution system. Learn more about the water treatment process.
Phoenix has five plants (treatment capacity indicated in million gallons per day/MGD):
- 24th Street Water Treatment Plant: 140 MGD: Treats Salt River Project water
- Deer Valley Water Treatment Plant: 100 MGD: Treats Salt River Project water.
- Val Vista Water Treatment Plant: 130 MGD: Treats Salt River Project water (plant shared with City of Mesa).
- Union Hills Water Treatment Plant: 160 MGD: Treats Colorado River water.
- Lake Pleasant Water Treatment Plant: 80 MGD: Treats Colorado River water.
Wells
Drinking water wells in Phoenix are used in support of the main distribution system and provides water to areas of the city furthest away from water treatment plants and are used as a means of storing a large supply of water underground. They are connected to the distribution system much like the plants. Only about 3 to 5 percent of the water in Phoenix comes from drinking water wells.
Total capacity of treatment plants and wells combined is 646 MGD, although the average daily delivery to customers is between 260 and 300 million gallons. The maximum amount of water delivered to customers took place in July of 2020, was 455 Million Gallons. The treatment plants and wells are operated to meet the demand and are constantly operated to prevent demand shortfalls and to maintain water pressure systemwide.
Water Distribution System
The water distribution system is where everything takes place between the treatment phase and you turning on the tap. The water distribution system is comprised of the following components:
Transmission Mains: The largest of water pipelines that transport water from the treatment plants to the reservoirs and smaller distribution mains. The largest main in service in Phoenix is 108-inches in diameter.
Distribution Mains: From medium size mains down to 8-inches, that ultimately connect to service lines that serve homes, apartment complexes and businesses.
Service Lines: These are the smallest lines, from as small as 5/8-inch up to 6-inches. Service lines are the lines that are connected to water meters, that are used to measure water use by the customer.
Water Valves: Water valves can be as big as the largest transmission mains, and as small as eight inches. They are used to shutdown or isolate water lines so leaks can be repaired, or lines can be replaced. They also connect to fire hydrants so they can be properly maintained.
Fire Hydrants: Hydrants are mostly used by the fire department to fight fires but are also used by a water utility to flush lines after a water main repair.
Storage Tanks and Reservoirs: Large reservoirs and smaller storage tanks are used to store water during off-peak demand hours.
Pump Stations: Also known as booster pumps, are used to add pressure to the distribution system when water is being pumped to a higher elevation against the force of gravity.
Pressure Reduction valves (PRVs): PRVs are used to reduce pressure in the distribution system when water is traveling from higher to lower elevations, and pressure needs to be reduced to prevent damage to infrastructure.
Wastewater Infrastructure
Where drinking water ends its journey at your home or business, wastewater starts its journey at your home or business then travels to a wastewater treatment plant. Below is a listing of components of the wastewater system managed by the City of Phoenix.
Wastewater/Sewage Collection System
Sewer Mains: Sewer lines connect to and collect sewage from homes and businesses, and the sewage travels through various size pipes to the wastewater treatment plants. The largest sewer main managed by Phoenix is 90-inches in diameter. Most sewage systems are designed to utilize gravity to reduce electrical costs.
Force Mains: Force mains are sewer mains that are under pressure due to being pumped to a higher elevation.
Lift Stations: Lift Stations are pump stations that are used to help move wastewater to a higher elevation against the force of gravity. Lift stations use force mains to move sewage until a great enough slope or angle is achieved and gravity can again be utilized.
Manholes and Cleanouts: Manholes and cleanouts are used by utility staff to access sewer lines for the purpose of inspection, cleaning, and treatment for cockroaches. Staff in Phoenix televise a good percentage of sewer lines every year to make sure the integrity of the collection system is at its best. Staff also uses large vacuum trucks (known as vactors) to remove grease, tree roots, and other debris that may have grown into the system.
Keeping the sewer lines clear of debris is critical to prevent sewage spills in the street and any backing up of the lines into homes and businesses.
Wastewater Treatment Plants: Phoenix maintains two wastewater treatment plants Wastewater treatment plants take the sewage that comes from residences and businesses and sends it through a multi-step process to clean the water to a very high standard so it can be reused for non-drinkable purposes, such as cotton crops and for cooling the nuclear reactors at the Palo Verde Nuclear Generating Station. The treatment process at Phoenix’s two plants follows this general process:
Primary Treatment: The first stage that removes large solids through screening and settling tanks.
Secondary Treatment: Biological processes through aeration and adding activated sludge by which organic matter and nutrients are removed.
Tertiary Treatment: Advanced treatment to remove specific pollutants like nitrogen, phosphorus, or pathogens.
Final Filtration and Disinfectant: the final process before the water is released back to the environment. Carbon filtration is generally used but at the 91st Avenue Wastewater Treatment plant the water travels through the Tres Rios Wetlands, part of the 91st Avenue plant infrastructure, to achieve a natural filtration process.