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Going Underground with the Orange County Water District

Going Underground with the Orange County Water District

February 9, 2021
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Orange County is home to one of the largest coastal groundwater basins in Southern California. The Orange County Groundwater Basin contains roughly 162.9 billion gallons of water and extends to 4,000 feet below ground at its deepest point. The continuing drought in the State and growing demand for potable water have increased the importance of the basin’s aquifers-both for use and protection. Operational coordination between Orange County’s Water District (OCWD) and Sanitation District (OCSD) helps meet these needs.

World-renowned Innovation

The county’s groundwater replenishment system (GWRS) is the world’s largest water purification system for indirect potable reuse. Here’s how it works. The OCSD completes standard wastewater treatment, but instead of discharging the treated water to the Pacific Ocean it is pumped to the GWRS for even more treatment. The OCWD ultra-purifies the water using microfiltration, reverse osmosis, and ultraviolet light with hydrogen peroxide. The result is high-quality water that meets, and is routinely lower than, all state and federal drinking water limits. The purified water is then returned to the basin aquifers.

Approximately 35 million gallons per day of purified water are pumped into basin wells to create a seawater intrusion barrier. Another 65 million gallons are pumped to OCWD percolation fields where it filters down through sand and gravel layers into the basin aquifers.

Assuring Water Quality

Before the purified water can be returned to the basin, it must undergo rigorous analytical testing to confirm it meets state and federal drinking water standards. This is necessary to protect the aquifers and to continue providing high quality potable water to Orange County residents.

At the OCWD Advanced Water Quality Assurance Laboratory, 20,000 samples of the purified water undergo more than 400,000 analyses each year. Such high sample throughput along with reliable data generation are crucial to keep the GWRS up to speed.

The laboratory relies on PerkinElmer instrumentation and software, such as the NexION® 2000 ICP-MS, to keep up with the daily demand for sample analysis and data generation. As the laboratory’s chemists explain, the NexION can analyze a huge number of analytes in a short period of time. Their PerkinElmer instruments also enable them to meet ever lower detection limit requirements and readily incorporate new contaminants of concern into their workflow. In addition to monitoring regulated contaminants, the OCWD participates in the U.S. EPA’s Unregulated Contaminant Monitoring Rule (UCMR) program. The UCMR program collects data for contaminants suspected to be present in drinking water, but that do not have regulatory standards. The monitoring data are used to track emerging contaminants trends and evaluate the need for regulatory intervention. PerkinElmer helped OCWD achieve UCMR Round 4 certification, and the laboratory is relying on them to support Round 5 certification as well.

The Orange County GWRS is important on many levels: it enables OCWD to supply 2.5 million people with safe drinking water, it protects the vital basin aquifers from contamination and depletion, and it monitors the drinking water supply for emerging contaminants of concern.

Achieving and maintaining these important capabilities requires analytical instrumentation that provides high sample throughput and low detection limit technology. No wonder OCWD laboratory chemists say that PerkinElmer is such a great partner to work with in advancing their important work.



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