Water Down the Drain: Out of Sight, Not Out of Mind
Gilbert, Ariz.- You flush a toilet, you wash your hands, you take a shower. Then what?
All water that Gilbert residents, businesses, churches, schools, and hospitals use indoors is collected and transported to the water reclamation plant (sometimes referred to as a wastewater treatment plant) to be treated and purified.
The water reclamation process starts with the sewer collection system, a network of pipes and pumps. To safely collect and transport wastewater to the water reclamation plant for treatment, Gilbert maintains a network of:
- 20,122 sewer manholes to access, inspect, and repair sewer pipelines
- 897 miles of Gilbert-maintained sewer collection system pipelines
- 21 lift stations to pump wastewater
- 2 water reclamation plants where wastewater is treated and purified
Once the wastewater is delivered to the water reclamation plant, it is first screened to remove large trash and debris. This screening process collects enough trash to fill a huge dumpster every two weeks!
After the big trash is removed, the wastewater is sent to the “primary clarifier,” a large tank where smaller debris (such as sand) is settled out of the water by gravity. The settling process produces “primary sludge,” which is sent to the solids handling section of the plant for treatment.
The liquid stream that remains after the settling process then moves to the “aeration basin” where microorganisms (known as the good bugs) work hard to consume the material that remains suspended in the water. These bugs are the key to wastewater treatment and are tended to very carefully by plant operators to ensure they stay healthy and hungry.
After the bugs consume the remaining solids, the water is sent to the “secondary clarifier.” In this large tank the bugs, heavy from having consumed the solids that used to be in the water, are settled out by gravity, leaving the water free of solids and ready for filtration and disinfection. From here, the treated water is sent through several stages of disinfection while the settled bugs, which form a “secondary sludge,” are sent to the solids handling section of the plant.
The solids handling section of the water reclamation plant uses more specially-managed bacteria and microorganisms to further digest the solids. After breaking down as much material as possible, the plant uses centrifuges to dry the remaining biosolids. Then, they are hauled off to landfill or used as fertilizer on non-edible crops.
After wastewater is treated and purified at the water reclamation facility, it becomes effluent. Because this water meets A+ standards, it is considered reclaimed water, which allows it to be used for irrigation on golf courses or HOA landscapes, as well as for groundwater recharge purposes, such as at the Riparian Preserve.
You can see the physical components and processes that treat wastewater and move it through the plant in this diagram.
To ensure our system runs optimally, the only thing that should be sent down the drain besides human waste and water is toilet paper. That’s it.
As Gilbert grows, so too does the wastewater infrastructure. The Greenfield Water Reclamation Plant, co-owned by Mesa, Gilbert, and Queen Creek, is about to undergo an expansion and upgrade to keep up with growth in the three communities.
The Greenfield Water Reclamation Plant will be expanded from a treatment capacity of 16 million gallons per day to 30 million gallons per day. In part due to water conservation efforts inside homes and businesses (plumbing is more efficient today than it was 20 years ago), more concentrated wastewater is coming into the water reclamation plants. There will also be upgrades to the plant to account for this trend.
Gilbert reuses all of its reclaimed water generated at the water reclamation plant within its Town boundaries, nothing goes to waste. We know water is precious here in the desert.