Secondary Treatment Is Not a Perfect System
Doug Korthof’s July 8 letter regarding treatment of Orange County’s sewage is misleading in that it may cause readers to believe secondary treatment completely eliminates live bacteria.
Secondary treatment removes some bacteria but not all. In fact, it is not the purpose of secondary treatment to remove bacteria.
Typically, primary and secondary treatment may remove up to 99.9% of bacteria, meaning if raw sewage contains 100 million total [coliform counts] per 100 milliliters, which is a typical level, there will still be at least 1 million live [coliform counts] per 100 milliliters in the full secondary effluent, compared to 5.5 million under the present practice with half primary and half secondary treatment.
Considering the high bacterial counts that have been reported at our beaches in recent years, full secondary treatment may have avoided some beach closures, but not all.
Korthof is beating the wrong horse. If Orange County’s sewage outfall is proved to be the cause of our beach closures, measures more drastic than merely rescinding the full secondary treatment waiver will probably be needed.
Going to full secondary treatment will be an expensive experiment with little or no guarantee that it will solve our beach contamination problems.
David M. Carlberg
Long Beach
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