Purification Technology

After wastewater goes through primary and secondary treatment, it flows to our Advanced Water Purification Facility where a multi-barrier process separates water from pollutants. The state-of-the-art, four-step advanced purification process consisting of 1) ozone pre-treatment, 2) membrane filtration, 3) reverse osmosis, and 4) ultraviolet light with hydrogen peroxide. The product water is near-distilled-quality and is stabilized with minerals before its roughly 10-mile commute to the Seaside Groundwater Basin. At the Basin, it is injected into the aquifer where it naturally filters through sand and gravel to support the local drinking water supply.

Explore the four purification steps by clicking on the links below.

Advanced Water Purification Facility

Advanced Water Purification Facility aerial

Instead of mixing into the ocean, secondary effluent feeds into the Advanced Water Purification. The facility is located at Monterey One Water’s Regional Treatment Plant just north of the city of Marina. Construction of the facility occurred from mid-2017 through 2019 and purified water production for groundwater replenishment began in 2020.

1) Ozonation

Ozone purification equipment

Ozone gas is infused into the water where it destroys microorganisms, breaks down contaminants, and improves filterability of the water. In addition to being a powerful disinfect, the ozonation process helps protect the integrity of the filters in steps two and three.
The water takes about three minutes to pass though this pipeline. 

2) Membrane Filtration

Membrane filtration purification equipment

Membrane filtration (MF) uses hollow fibers, similar to straws, with tiny pores or holes in the sides that are 0.1 micron in diameter—that’s 1/500 the diameter of a human hair! By drawing water through the pores into the center of the fibers, suspended solids, protozoa, bacteria and some viruses are filtered out of the water.
It takes the water approximately 1 minute to flow through these membranes.

3) Reverse Osmosis (RO)

Reverse osmosis purification equipment

Reverse osmosis (RO) removes dissolved chemicals, viruses, salts, metals, and pharmaceuticals from the water. Each membrane is created by layering flat sheets of a semi-permeable material and rolling them into units. During the RO process, water is forced through the molecular structure of the membranes under high pressure. About 81% of the water will pass through the membrane and move to the final purification step. The remaining 19% leaves as a concentrate that is discharged into the ocean.
It takes water approximately one minute to flow through the reverse osmosis membranes.

4) UV Disinfection + Hydrogen Peroxide

UV plus advanced oxidation purification equipment

In the final purification step, the water is exposed to high-intensity ultraviolet (UV) light. Hydrogen peroxide (H2O2) is added to the water where the UV light breaks it apart into oxidants. This process disinfects and destroys any trace organic compounds that may have passed through the reverse osmosis membranes.
This process destroys 99.9999% of protozoa, bacteria, and viruses present within approximately 18 seconds.

Stabilization, Conveyance, and Injection

Injection wells for groundwater replenishment

The combination of primary/secondary wastewater treatment plus advanced purification keeps harmful compounds from reaching the drinking water supply. The resulting product water is actually so pure, we need to add minerals back into to stabilize it. To balance the water, we add calcium and remove carbon dioxide. The stabilized product water is now ready for its 5-hour and approximately 10-mile commute to the Seaside Groundwater Basin for replenishment of this key drinking water source.