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Harmful chemical prevented from entering water supply
Cup of water

Perfluorooctanesulfonic acid — a manmade chemical used in a wide array of industrial applications — has been detected in raw water source hundreds of feet below Manteca that a municipal well taps into.

Long-term exposure can result in significant health issues such as liver and thyroid problems, cancer, harm to a developing fetus or infant, or immune system issues.

As ominous as that might sound the chemical never made it past the well’s treatment system that employs granular activated carbons that remove the substance in question as well as other harmful materials.

The fact the perflurooctanesulfonic (PFOS) acid was detected and the public being made aware of its existence in a raw water source is the  result of California having what many consider to be the nation’s most thorough water testing requirements along with more restrictive acceptable  contamination thresholds often lower than the federal government’s that are coupled with robust reporting requirements.

The City Council last week, as required by state law, was made aware of the existence of PFOS within 30 days of the discovery in the raw water source when it exceeded the mandated reporting levels for PFOS. Details will be included in the annual state mandated consumer confidence report that will be distributed to all Manteca water customers in June 2022.

As for the continued used of the well in question, the levels of PFOS detected are substantially below levels that would require the city to stop using the water source.

The city has close to two dozen municipal wells in addition to securing treated surface water from the South San Joaquin Irrigation District.

During heavy water use months — mid-spring to late fall when water demand due to landscape irrigation is at its highest demand — the city obtains roughly 50 percent of its water supply from wells and the rest from SSJID. The rest of the year almost all water comes from SSJID.

That allows the city to rely on a water treatment system that is even more robust than the gold standard that granular activated carbon has become.

The surface water treatment plant employs dozens of panels the water passes through after solids are removed.

Each panel is jammed with 25,000 spaghetti-like strands of thin hollow fiber membranes.

As the water passes through, the hollow fiber membranes serve as a physical barrier to contaminants. The porous fibers are hollow at the center. The surface is covered with billions of microscopic pores that filter out all know substances. That allows the waste to be disinfected and treated white little or no chemicals.

The pores in question are 0.02 microns. A red hood cell is 0.07 microns.

As such the SSJID water treatment is state-of-the-art and even more effective than granular activated carbon

The city has been able to mix the treated surface water with treated well water to effectively further enhance the safety of drinking water.

 

To contact Dennis Wyatt, email dwyatt@mantecabulletin.com