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The City of Angels Does Its Dirty Work Well

March 05, 2000|JAMES RICCI

The city of Los Angeles is such a multifarious organism, 32 miles long and a couple of mountain ranges wide, that it's impossible to say what constitutes its heart. City Hall? Hollywood? Olvera Street?

No such uncertainty exists about its bowels, composed essentially of the Hyperion sewage treatment plant on the beach south of LAX and the 6,500 miles of sewer lines that radiate from it to points as distant as Sunland and Woodland Hills.

Whatever might be wrong with the city's heart (or head), its digestive tract is a model of efficiency. More than anything else of human devising, it allows about 4 million of us to live more or less civilly on this overburdened landscape.

Every day, each of us bathes, flushes toilets and otherwise generates between 75 and 100 gallons of waste water without poisoning our surroundings. We should pause once in a while to contemplate the sheer wonder of this.

What is a matter of unthinking expectation to us is Charles B. Turhollow's passion and life's work. The 40-year-old bachelor is a senior sanitary engineer at Hyperion, where he has labored for 16 years. A precisely spoken man with an engineering master's from UC Berkeley, he walks his 144-acre workplace with a proud, proprietary air, ears tuned to the city's alimentary peristalsis, eyes shining as he assays waste-activated sludge thickening, anaerobic bacterial digesters and biosolid dewatering centrifuges.

"Whenever I start in on it," he says, "my friends always say to me, 'No, no more, no more.' "

Hyperion, thanks to a $1.6-billion upgrade completed a little more than a year ago, is gleaming, tidy and largely silent, its dirty work tucked away below ground in giant airtight tanks. Even its odors are charcoal-filtered before they are released into the atmosphere; the smell is perfectly tolerable. Once the major culprit in the degradation of Santa Monica Bay, it is now a paragon of restraint.

Each day, about 360 million gallons of waste water flow into the plant, 85% of it via gravity, thanks to the mindful construction of sewer lines over the years. This means the system doesn't depend on electric power to continue working after, say, an earthquake. The inflow, teeming with our viruses and intestinal bacteria, arrives via five main trunk lines up to 12 feet in diameter. It is 99.7% water, and the entire $47-million-a-year operation is dedicated to getting rid of as much as possible of the remaining three-tenths of a percent.

Nineteen-foot-tall bar screens, with vertical members set three-quarters of an inch apart, filter the flow into the plant. Giant mechanical rakes remove whatever catches on the screens, such as the five tons of wet rags that catch there daily and are sent to landfills.

Afterward, the effluent rests in giant grit-removal tanks, where every day between five and 10 tons of sand settle out to be landfilled.

The stuff then passes into large underground tanks for a couple of additional hours of settling. Oil and grease are skimmed. Solids sink to the bottom.

At this point, the effluent and the solids part company. The former goes into one of 27 270-foot below-ground tanks where fresh water-, warmth- and oxygen-loving bacteria go to work on it. A steady flow of pure oxygen spurs the bacteria on. As they eat, they multiply, displacing 95% of their foodstuffs in about two hours.

The effluent then flows into giant outdoor clarifying tanks, which attract sea gulls--a sign, Turhollow says, of the stuff's relative purity. The bacteria that now makes up nearly all of the "biomass" in the water sinks to the bottom. The water on top is pumped five miles away into Santa Monica Bay, beneath 190 feet of cold salt water, which effectively kills the remaining bacteria.

The solids settled out earlier in the process are sent to egg-shaped "anaerobic digesters," the newest of which are 110 feet tall. There they are attacked by oxygen-hating bacteria that date to when the earth was airless and waterless. These consume about half of the organic matter in the sludge and belch out a gas, mostly methane, that has two-thirds the heating value of natural gas. Each day, 7 to 8 million cubic feet of this gas are scrubbed and piped to the city's adjacent Scattergood Steam Generating Plant for use as fuel.

The solids are centrifuged to spin out as much of their remaining water as possible. What's left resembles black cow patties and is, Turhollow assures, "a little drier than toothpaste." Rich in nitrogen, phosphorous and remnants of fats, proteins and carbohydrates, it is excellent for organically conditioning otherwise unfarmable soil. Each day, 35 tarp-covered trucks ferry 850 tons of it to farms in Kern, Kings, San Diego and Riverside counties, where it is tilled into soil used to grow non-food crops such as cotton and animal fodder.

I might be making a fatuous association here, but I wonder how it is that Los Angeles handles this most vital and distasteful aspect of overpopulation with such elegance, but can't seem to keep the buses from breaking down or put enough books in the schools. If the will and skill exist for the one, why not for the others?

That's the downside of dwelling on the sewage treatment system. It could lead a person to think that Los Angeles really is of a piece, manageable and movable toward becoming a shining city on a hill.


James Ricci's e-mail address is

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