Sewage plant phasing out its odorous method of treatment

Two million dollars over budget, 18 months behind schedule, and about 30 years later than nose-plugging neighbors would have liked, San Mateo’s sewage treatment plant is finally ridding itself of its unique reek.

The plant, which treats 13 million gallons of raw sewage a day from San Mateo, Foster City, Belmont and Hillsborough, will transition next month from its famously stinky sludge-cooking system to a new — and hopefully less offensive to the nostrils — bacterial treatment system.

The transition will be complete in October — more than 18 months behind schedule, Public Works Director Larry Patterson said. The delays, caused by a series of expensive breakdowns in the old, decaying treatment system, has cost the city more than $2 million extra to extend the contract with its construction management team, Patterson said.

The delays also come at the expense of the plant’s neighbors, which include a school and a residential neighborhood, separated by a mere fence from the facility. Residents have protested the plant’s distinctly noxious odors after its installation in 1976.

The current system, known by brand name Zimpro, is unusually foul because it pressure-cooks the sewage, explained Public Works Deputy Director Darla Reams.

In a tour of the facility recently, Reams explained that there’s nothing that can mask the smoldering-chemical-toilet smell of the plant.

“That’s Zimpro,” she said. “It’s the only one still working west of the Mississippi, that I’m aware of.”

The new treatment method, which uses anaerobic bacteria to treat the sludge, will be much less odiferous — and cheaper to run, Reams said.

The project has cost more than $30 million, and has beenpaid for with sewage fees, which were increased about fourfold last year.

The fix couldn’t come a day too soon for Zakir Ali, who moved into the neighborhood about three years ago. He said his family has considered moving because they find the odor so noxious.

“Every time you walk outside or open the window, it’s there,” he said. “When family comes over, they ask, ‘Why does it smell like that in here?’”

kworth@examiner.com

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