Dublin San Ramon Services District has been busy recently and making headway on its largest capital improvement project in two decades.
Crews have been working since April at the Regional Wastewater Treatment Facility in Pleasanton to partially demolish and replace a sedimentation tank and build another, helping reduce energy costs and improve the wastewater treatment process.
It’s the largest project for the district since a treatment plant expansion in 2000, costing a total of about $19 million. The primary treatment capacity, which is currently “undersized for the facility’s average dry weather flow of more than 10 million gallons a day” will increase by about 33% when everything is done, according to DSRSD.
This will also help minimize or eliminate adding any stress in the next steps of the wastewater treatment process.
Work entails adding a fifth primary sedimentation tank to the site’s current four and replacing one of the existing tanks. The two new tanks will be 100 feet long, 20-1/2 feet wide and 15 feet deep, five feet deeper than the old ones. The internal mechanisms of the three remaining tanks and the motor control tank are also being replaced. An additional grit tank is also being added; grit tanks help protect equipment and prevent clogged pipes at the facility by removing small material like sand and gravel.
When the wastewater finally arrives at the primary sedimentation step, scum is skimmed from the surface of the water while solid particles are scraped from the bottom of the tanks. The sewage is then separated into different treatment streams, depending on whether liquid or solid.
Having two deeper tanks and upgrading the internal mechanisms will let the wastewater sit longer in the primary tanks, helping improve separation of liquids and solids. Removing solids earlier in the process helps reduce energy use in later treatment and lets the plant send more solids to digesters that create biogas, a renewable fuel used to generate electricity to operate the plant.
The expansion and upgrades will also allow for future buildout in addition to providing the primary treatment capacity required for both current flows. DSRSD has also been working since April to replace a 405-foot-long foul air pipe running from the site and along Interstate 680.
The foul air line rehabilitation should wrap up by the end of July, according to DSRSD, while the primary sedimentation tanks project is estimated to last through fall 2021.