Background

The Heber Public Utility District (HPUD) owns and operates the water and wastewater treatment facilities. The wastewater treatment plant was constructed in 1981 and treats all of the wastewater produced within the township. Treated effluent is discharged into the Central Drain tributary of the Salton Sea.

This secondary treatment plant has reached its maximum hydraulic and biological treatment capacity. Influent flow rates often exceed the plant’s design capacity of 405,000 gallons per day. In 1997, the average influent wastewater flow to the plant was 431,000 gallons per day, with peak flows as high as 630,000 gallons per day. During periods of high
wastewater flows, the undersized influent line is overloaded, backing sewage up into the collection system and possibly into nearby homes, creating a health hazard.

In addition, deficient equipment and ineffective sludge drying beds reduce the quality of the effluent and expose plant operators to a serious health risk. Specifically, when the only comminutor (solids grinder) is out of service solids collect at the headworks, which must be manually removed. This means that the plant operator must descend into the screen
chamber with a rake, shovel and bucket to collect the screenings. Improperly aged sludge also tends to create additional treatment problems within the clarification units and can harbor greater concentrations of dangerous bacteria, as well as increase noxious odors
in the vicinity of the plant.

Description

To correct these deficiencies and bring the plant into compliance with state water quality and health regulations, the utility is undertaking a project to upgrade and expand the plant. The proposed project consists constructing a second oxidation ditch treatment system parallel to the existing one and includes:

• Improved headworks equipment.
• The addition of a second concrete oxidation ditch.
• The addition of two final clarifiers.
• Improvements to the sludge drying bed decant system.
• The addition of a chemical disinfection system for the treated
  effluent.

The capacity of the expanded treatment facility will be 810,000 gallons
per day.

Benefits

Improvements in the wastewater treatment system will correct current deficiencies thereby bringing the plant into compliance with state regulations, as well as reducing the likelihood of contamination and disease transmission from the discharge of improperly treated wastewater. System expansion will also ensure sufficient treatment capacity for the next 15 years.