Water Quality

Water Quality 

The final quality of West Basin’s five designer waters is dictated by either regulatory permits issued by the Los Angeles County Regional Water Quality Control Board, or contractual obligations to our customers.

Permitted Qualities

Two types of West Basin’s designer waters are permitted by the Los Angeles County Regional Water Quality Control Board.

Indirect Potable Reuse: Groundwater Replenishment - Surface Application

Along with several other requirements, West Basin’s seawater intrusion barrier injection water is required to remain below 5.0 mg/L of Total Nitrogen and 0.5 mg/L of Total Organic Carbon, when divided by the maximum average Recycled Water Content in the Barrier.  

Disinfected Tertiary Recycled Water

There are several requirements written into the permit for West Basin’s Title 22 Disinfected Tertiary recycled water. Among those, the Disinfected Tertiary recycled water must be disinfected such that the 7-day median of total coliform bacteria does not exceed 2.2 MPN per 100 mL. Additionally, the Disinfected Tertiary recycled water must not exceed a turbidity of 2 NTU, based on a 24-hour average.

Contractual Obligations for Industrial Users

For West Basin’s customers that require a specific water quality, West Basin has added additional treatment technology in order to achieve that quality.

Nitrified Recycled Water

Three of West Basin’s large industrial customers use recycled water for refinery cooling tower applications. An additional biological treatment step is applied to the Disinfected Tertiary stream in order to reduce ammonia concentrations and prevent corrosion of the refinery equipment.

Boiler Feed Supply

Three of West Basin’s large industrial customers use recycled water for boiler feed applications.  In this application, recycled water is used for generating steam to be used within the refining process. Additional treatment steps, including microfiltration and reverse osmosis are utilized to reduce the Total Dissolved Solids and other inorganic constituents such as Total Hardness and Silica, to levels acceptable for steam generation.

West Basin produces two types of this recycled water, low pressure and high pressure boiler feed supplies. High pressure boiler fed water is produced by treating the low pressure boiler feed product with a second pass of reverse osmosis. The low pressure boiler feed treatment system reduces the Total Dissolved Solids in the recycled water to approximately 35 mg/L, whereas the high pressure boiler feed treatment system reduce the Total Dissolved Solids ever further, to approximately 3 mg/L.


Water Quality Reports

West Basin takes seriously our responsibility to provide safe, high quality water to our customers. Our water quality is better than required by state and federal drinking water standards.  As a wholesale agency, West Basin does not conduct water quality tests on potable water but monitors Metropolitan Water District's testing and reporting. Click on the following link for MWD's water quality reports or visit www.mwdh2o.com.

Since 1991, California water utilities have been providing information annually on water served to its consumers, according to state law. A 1996 federal law similar to California's also required water utilities across the country to provide information to their consumers on the water served. The reports describe the water quality, sources of water, and other information to inform consumers on their water supply. For more information, contact your water provider for details on the annual consumer water quality report.