Tertiary Treatment Process 

After primary/secondary wastewater treatment, the effluent reaches a fork in the road. About 10 months out of the year, a portion of this secondary effluent forks to our tertiary facility—the Salinas Valley Reclamation Project. The facility utilizes a three-step chemical and filtration process to further treat secondary effluent:

  • Flocculation
  • Tertiary Filters
  • Chlorine Disinfection

The resulting recycled water meets all State standards for the unrestricted, safe use on freshly edible food crops. To ensure safety standards are consistently maintained, laboratory analysis continuously monitors water quality—for more information visit the Recycled Water Quality page.  

Take a virtual tour of the Tertiary treatment technologies below.


Flocculation Basins at the Regional Treatment Plant

After primary/secondary wastewater treatment, water heads up the hill to our tertiary facility. Here, a polymer, which acts like a glue, is added to the water. In the Flocculation Basins, large blades mix the polymer into the water which binds together remaining dissolved organic matter. These tiny clumps are called flocs and are filtered out in the next step.

Tertiary Filters

Multi media filtration units at the Regional Treatment Plant

Next, the flocs that were previously formed are filtered out of the water. Water flows into the top of the basin and filters down through a 6-foot bed of anthracite coal, sand, and pea gravel. Flocs get trapped in multi media filter.

Chlorine Disinfection

Chlorine Contact Basins at the Regional Treatment Plant

As a final protection, chlorine is added to the water. The water must spend at least two hours in the Chlorine Contact Basins. This will kill or disinfect any remaining disease-causing germs and bacteria. The final product water is now clear, odorless, and safe for the irrigation of conventional and organic food crops, like lettuce, broccoli, and strawberries. It also meets public contact standards for swimming pools.

Storage Pond

Recycled water storage pond at the Regional Treatment Plant

After treatment, the recycled water is held temporarily in an 80-acre-foot storage pond before it is distributed to 12,000 acres of farmlands in northern Monterey County. Throughout the distribution area, you can spot the purple pipes, the international color for recycled water, that deliver the final water to the fields.