The aim of the Wastewater & Sewer Services division is to provide a safe water supply for the City while protecting the area’s precious natural assets.

Sierra Vista doesn’t have a municipal water supply, but it does treat all of the City’s wastewater. All wastewater flows to the City’s wastewater treatment plant at the Environmental Operations Park.

Wastewater Treatment Facility

The wastewater treatment facility uses screening equipment, equalization basins, anoxic and aerobic basins, clarifiers, and sludge handling and processing equipment. The treatment that occurs uses a biological nutrient removal process to eliminate nitrogen from the water, resulting in clean effluent that is recharged to the aquifer.

The incoming wastewater is screened during preliminary treatment. Larger inorganic materials are removed from the treatment process including plastics, rags, and heavy paper. Smaller, secondary screens remove organic and inorganic particles from the waste stream, followed by grit removal which further eliminates inorganic material like sand, egg shells, and coffee grounds, which cannot be treated biologically, and can cause damage to pumps and motors in the treatment process.

After preliminary treatment, the wastewater flows by gravity to the anoxic and aeration basins. In the aeration basin, the water is mixed using forced air, which provides the bacteria in the treatment process with sufficient oxygen to oxidize the incoming carbon supply. Ammonia nitrogen is converted to nitrate nitrogen and then converted to nitrogen gas in the anoxic basin. The denitrified water then flows to the clarifiers, which acts as a settling tank. Here, solids settle to the bottom and the clear effluent flows to the wetlands.

The wetlands provide further uptake of any remaining nitrogen, and serve as a habitat for many species of birds, mammals, and amphibious creatures.

Biosolids removed from the treatment process are dewatered and delivered to the City’s composting facility where it is mixed with green material. After treatment, the finished compost meets the U.S. EPA Class A Exceptional Quality standard under 40 CFR Part 503. This level of treatment imposes the strictest requirements for pathogen reduction and vector attraction reduction. By meeting this standard, the City of Sierra Vista is able to distribute the Class A composted biosolids to farmers, park agencies, and the general public to use as fertilizer, or as a soil amendment.

The Results

The EOP has been recharging water into the aquifer since 2001. To date, more than 9 billion gallons of clean water have been sent to the aquifer.

How You Can Help

You can help the EOP work better by disposing of household products wisely.

• Don’t dump solvents, pesticides, and other hazardous chemicals down the drain
• Recycle  fat, oil, and grease instead of pouring them down the drain.
• Don’t flush hair, diapers, sanitary products, or “flushable” wipes down the toilet. Regardless of what the packaging says, these products do not readily break down in the wastewater treatment process and must be removed by hand.

You can also help by conserving water! Learn more about water conservation.

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