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Sewage 2.0

San Jose’s sewage plant is a wonder of old-school science and technology. And it’s falling apart.

by Alastair Bland on May 20, 2009
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The collective habits and trends of South Bay society are easily apparent at the San Jose–Santa Clara Water Pollution Control Plant. For example, employees there have noticed that baby wipes have become popular in recent years. Locals, too, have evidently eased up on dietary corn in the past decade—at least the whole-kernel variety. From May through September, carbon coalesces as oily black grit on the surface of the slow-moving settling ponds. It’s the undigested residue of overcooked meat and summertime barbecues.

Longtime plant workers have witnessed changes related to the area’s economy. Before the fruit-canning industry left town in 2000, the sewage plant’s water intake periodically grew syrupy, as tons of peaches, plums, cherries and pears underwent processing just up-current. And trace heavy metals became a substantial problem in the early 1990s as the tech industry grew.

Workers at the plant tell an interesting sports story: As the Super Bowl draws toward the end of the second quarter, plant operators know it’s coming. An hour into the game, the water flow begins to increase. And as the victors take to the press room—and as Santa Clara County unseats itself from couches countywide—the phenomenon arrives in full force. The dark brown current swells perceptibly until the volume has increased by a full 10 million gallons—but it only lasts an hour. And just as suddenly and just as predictably, the waters subside again. It happens every year. They call it “the halftime flush.”

But most of what comes down the pipe at the plant is, frankly, crap. The 53-year-old facility, which occupies 2,600 acres of former marshland on the southern shore of San Francisco Bay, serves eight cities and receives the toilet flushings of some 1.4 million people.

An average rate of more than 100 million gallons of water enters every day, guided through a conceptually simple yet technologically advanced system of screens, filters, microbial cleansers and digesters. The water is black as a swamp when it enters, but not 24 hours after each flush arrives, it rushes out again, clear as tap water and just about as clean.

The water flows into a large wildlife sanctuary—the Don Edwards San Francisco Bay National Wildlife Refuge—and here birds thrive and fish sometimes swarm. Meanwhile, a 600-acre grid of levee-lined ponds is reserved for the fecal matter itself, which spends several years drying in the sun. By the time it’s 90 percent dehydrated, it is Class A stuff. This means that trace toxins are so scant that it could legally be used as farm fertilizer. But with few growers nearby and Newby Island Landfill just across Los Esteros Road, the crumbly detritus is gifted to the dump managers, who use it to cover their trash heaps.

The entire treatment process, from start to finish, illustrates the leaps and bounds by which society has improved its own hygiene in the past half-century, to say nothing of the past 500 years. But there’s still room to improve, and today the sewage facility is looking at a massive makeover.

Billed as the “Plant Master Plan,” the project aims to correct five decades of infrastructural decay as well as advance the system into an ambitious program of 100 percent energy self-sufficiency and zero-waste operations.

The project could also prevent an ecological disaster. As inflow volume increases with the South Bay’s growing population, the chances that the facility will someday experience a devastating overflow are growing more likely.

The last near-disaster was in February 1998. After several weeks of torrential rains, a surge of rainwater leaked into the sewage lines and flooded down the pipes faster than it could flow through the four entrance screens at the head works, where the county’s wastewater first enters the plant.

To imagine the excitement of what followed, picture yourself flushing a toilet—a toilet in a public space, like a restaurant. Now, imagine that the toilet water does not drop, and that it appears to be clogged. The dirty water rises, slowly, yet fast enough to incite rapid panic. You whirl about, looking for a plunger. There isn’t one, and you next wonder if you’d dare dunk your hand through the mire to free the clogged sludge, but before you can work up the nerve, the evil water has risen to the rim, where it seems to hang for a terrible moment.

Multiply this minor disaster by a million times, and you’ve got the picture of the 1998 event.

Fortunately, the levee that surrounds the treatment plant kept the waste from escaping outward into the marshland. But the incident served as a wakeup call and sparked the decision to build a second headworks adjacent to the old. This addition is now fully built and in experimental use, but still other changes must be made as the population grows and as the plant begins to show its age.

The electrical system is wearing out, and the concrete walls are wearing thin. A consulting firm hired in 2007 to diagnose the sewage plant’s ailments came up with a grim figure; no less than $1 billion is needed to put the facility in top-notch working order, and that leaves plant managers face to face with one of the greatest logistical challenges faced by engineers today: to seamlessly swap pipelines and tanks in a massive sewage system that cannot be halted, ever—24 hours a day, seven days a week, every day of the year. </p> <br> <p> A Sullied Past

Prior to 1956, all the vile bodily wastes of roughly a half-million locals flowed directly into the south end of San Francisco Bay. Not so much as a screening system separated the bay’s waters from the community’s garbage and sewage—not to mention occasional doses of typhoid, cholera and hepatitis that surely passed through.

The 20-odd fruit canneries that operated locally in the 1940s screened their own outflow to keep organic waste from reaching the bay and sparking the sort of microbial activity that expends all available oxygen in an ecosystem, but during World War II these operations removed the barriers to facilitate outflow and allow for a faster rate of production.

The accumulation of organic refuse in the South Bay destroyed what had been until the early 1900s a favored marshland for clammers, fishermen, duck hunters and naturalists in general. The horrific odors steered visitors away, while the scum and slime that washed in and out with the tides made life a misery and a hazard for residents of Alviso, who lived in constant risk of contracting mosquito-borne diseases.

In San Jose, many residents were blissfully ignorant of the problems downstream, and for several years the populace resisted a proposal to increase utility rates to fund construction of a sewage-treatment program.

But in 1956, the wheels of progress began to roll. The city installed a screen at the sewage outflow. It didn’t change much, though; the problems of microbial pollution and oxygen depletion persisted, and only the big solids, like dead cats, condoms, hair clods, scrap metal, lumber and other refuse, were kept from the bay. The system was essentially still as archaic as anything to be found then or now in the Third World.

In 1964, city planners installed the secondary treatment stage, in which the swamp-black water moved slowly through a series of settling ponds as heavier solids dropped out and floating matter was skimmed from the top. The remainder—things both mushy and microscopic—still drained into the bay.

Finally, in 1979, the biological treatment stage was implemented. This is where the real magic happens in a process that mimics exactly what happens naturally in any stream or aerated body of water, only in a highly accelerated and intensified way.

A steady stream of screened sewage enters a series of cement basins, each 20 feet deep, about as wide, 100 yards long and churned from below by air jets. Here, microorganisms cultivated precisely for the job latch onto the swirling debris and particulates from humans and from soaps, detergents and various pollutants—and they feast, breaking down the corruptions of our digestive tracts.

These bugs and the waste they produce meanwhile clump together into a coagulated gunk of microbes and grit called floc. The water is ushered into circular swimming-pool-like basins, flanked by olive trees, where the heavy floc precipitates out. The material is later dredged from the bottom, most of it sent to the three-story-high anaerobic digesters, and the rest is streamed back into the aerated basins, roiling nonstop with the endless flow of sewage created by 1.5 million residents of a 300-square mile area encompassing San Jose, Santa Clara, Milpitas, Campbell, Cupertino, Los Gatos, Saratoga, and Monte Sereno.

The sludge is pumped out of the digesters, which cook methane out of the waste, and the brown mush moves onward to the drying ponds on the property’s east side, just a friendly wave from the residents of Milpitas. Each pond contains sludge in its own respective stage of dehydration; some ponds are still layered with 2 feet of water, fresh from the digesters, while others, three years into the process, are caked with detritus as crumbly as pie crust.

Meanwhile, the hazy water enters its last stage of treatment: filtration. It is drizzled through 2 feet of coal and a foot of sand, finishing its 20-hour circuit through the facility as clear as tap water and almost clean enough to drink.

The treated water flows northward and by gravity for the last quarter-mile of its journey. Once polluted with industrial toxins and human filth, it now meets the open water of San Francisco Bay as pure as many natural streams that flow to the sea.

A footbridge crosses the 30-foot-wide current of water at the property boundary. Just upstream of the bridge, steep banks of earth and vegetation meet the water in a scene resembling that of an Irish trout stream. Just downstream, in a pool of whitewater below a 3-foot drop, sea lions sometimes appear. Gulls stand on the shore. Striped bass occasionally swirl under the surface.

A handful of employees once spent their lunch breaks casting plugs for the stripers. The fishing was excellent, remembers Dale Ihrke, the plant’s manager of 19 years, but he had to impose a no-fishing-during-lunch policy about a decade ago when enthusiasm for bass fishing began to distract workers from their duties.

But among this vibrancy of life at the outflow, of human waste in the water there is, miraculously, none.



by Alastair Bland on May 20, 2009
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