Tuesday, August 25, 2009

A Pollution Revolution

by Tom Emch

In the Diamond Valley of Alpine County is a sparkling new 165-acre lake.  It looks ideal for swimming, boating, camping and fishing - and it is.  Majestic mountains form the backdrop for this pristine jewel, alive with rainbow trout.

But those trout aren't swimming in an ordinary Sierra lake.  There isn't another like it in the world.  Every drop of that beautiful blue water comes from sewage.

The lake, known as Indian Creek Reservoir; is filled entirely with reclaimed water from the South Tahoe Public Utilities District.  One billion gallons of it.  

If you can stomach the idea, what goes into the utilities district treatment plant as a six-letter word comes out as a five-letter word - water.  Good water.  It meets U.S. Public Health Service drinking water standards, tastes slightly flat but mixes well with scotch.

This effluent of the affluent, from some 8000 buildings along Lake Tahoe's south shore, from Emerald Bay to Stateline, is purified and pumped 27 miles by pipeline over Luther Pass and to the reservoir where it serves three purposes.

*  It supplies irrigation for farmers with pasture land or bay and alfalfa.  
*  It is a receptacle for unwanted effluent from nearly one-third of the Tahoe Basin.
*  It provides a new Sierra recreation facility, approved by the State for water contact sports.

Boating and swimming in what was once sewage?  Just how pure is the water?

It's comparable in quality to the drinking water from your tap in The City, according to the Purification Division of the San Francisco Water Department.  Accepted water quality tests indicate San Francisco drinking water is slightly higher in turbidity than that at the reservoir, but slightly lower in detergents, phosphorous and alkalinity.  The coliform bacterial count is almost identical.

If that doesn't tell you much, listen to Bob Tharatt of the State Fish and Game Department, who stocked the reservoir last August with 8000 rainbow trout.  "The water's fine - or the trout wouldn't be thriving."

Two and a half months after the stocking, the fingerlings had doubled in size.  "We expect they'll be a foot long by opening day of the season, May 2.  It's a good test of the water quality.

"Rainbows require a pollution-free environment, unlike carp or catfish.  We stocked the lake as an experiment, but the results are so good that we plan more stocking to replenish what the fisherman take out."

The lake, man-made from reclaimed wastewater, was made possible by one of the world's most advanced sewage treatment plants.

The $28 million plant is the engineering answer to water pollution.  Because it was a prototype, nearly half of the funding came from government agencies, including the U.S. Public Health Service, the Economic Development Administration, the U.S. Forest Service and the State of California.  Residents of South Lake Tahoe provided the rest through revenue bonds, and they provide operating money through sewer assessments.

The reclamation plant, which has been visited by engineers from all 50 states and from 31 foreign countries, was completed in March of 1968.  Eight months later, an ammonia stripping tower was added to removed nitrogen from the effluent.  And in April, 1969, exportation began.

Pumps lift the water 1700 feet to the summit of Luther Pass from where it flows by gravity into Alpine County and to the reservoir hidden in the mountains, five miles from Woodfords.  

Lakeside development plans, according to Hubert Bruns, chairman of the Alpine County Board of Supervisors, include an access road from Hwy. 89.  And the State Bureau of Land Management will spend $100,000 to erect 35 campsites, 20 picnic sites, restrooms and a boat launching ramp.

Alpine County supervisors, reluctant at first to take the effluent, now know the quality and the value of the water they are getting free.  (The Federal government and the South Tahoe Public Utilities District maintain the pipeline.)  They almost didn't.

Export routes considered but prohibited by various agencies included one over Echo Summit to the South Fork of the American River, a route over Dagget Pass to Douglas County, Nevada, another into the Hope Valley.  

Location of the reservoir in Diamond Valley was finally approved in late 1965 by the Lahontan Regional Water Quality Control Board.  The reservoir with its two dams and spillway was completed in December, 1967.

Solving the export problem was simple compared to the task of producing potable water from raw sewage.  And the District had guaranteed water of drinkable quality at the point of discharge.  

Jerry Wilson, quality watchdog for the District's consulting engineers, Claire A. Hill & Associates of Redding, explains how it's done.

"First you must realize that there is only one wastewater reclamation plant in the world anything like this.  It's in Pretoria, South Africa.  And when they get through treating the water there, they feed it back into the city water system for drinking.

"The effluent comes in over there, almost 99 per cent liquid and about body temperature.  Solids are ground up, and removed by sedimentation in these tanks."  You don't have to look where he's pointing because you can smell it.

"Then it goes into these sludge aeration tanks where diffused oxygen is pumped in for the bacteria, or bugs, that eat the sewage.  The waste, solid sludge, is settled out and pumped in the incinerator where it is cooked and reduced to sterile, insoluble ash and burned off.  Please note there is no steam or smoke or air pollution from the incinerator.

"This is a primary and secondary sewage treatment.  And this is where conventional treatment stops.  All major cities have this and pump the secondary effluent directly into rivers.  Seattle pumps it into Puget Sound.  The Ohio, Illinois and Mississippi rivers all get this sort of effluent."

At this point you notice it still smells plenty.  And it's muddy colored.  You don't believe even with the wildest imagination, that it will ever be fit to drink.

"Over here," says our tour guide, "we add lime to remove phosphorous. And in the next tank we take out the lime floc by sedimentation.  From these secondary clarifiers ,  the overflow  is pumped to the ammonia stripper or nitrogen tower where the effluent becomes droplets and the ammonia is dissolved as a gas.  Here, carbon dioxide is added to reduce the pH factor, or alkalinity.

"The re-carbonated water flows to ballast ponds.  These are control tanks for the timing of the whole three-day process.  Then, the effluent flows to the tertiary treatment plant where it is filtered in sand, anthracite and garnet.  This removes the last of the solids.  

"The, it is pumped through eight carbon columns containing 25 tons of charcoal each.  Here, the color is removed; also remaining chemicals, detergents and dissolved organics.  "Now the effluent is clear," says the guide, "clear as Tahoe water."

And by this time you are almost convinced the water is good enough to drink.  For somebody else to drink.  But there is one more step.

The final touch is simple chlorination.  "To kill any coliform bacteria." he explains.

The magician of wastewater reclamation then leads you to an artificial mountain spring outside the plant.  Clear, inviting, bubbly, cool water cascades from the rocks.  "Here, try some," he says and smiles.

"You mean drink it?"  says the guest, knowing that to refuse would be a gross error of etiquette.  So you take a sip of the reclaimed wastewater and say "Hmmm, marvelous."

Later noting few bad effects, you even begin to fee good.  Daring.  After all, what's good enough for rainbow trout is good enough for you.

And later still, after two martinis, you suddenly remember with a shock that in the lobby of the South Tahoe Public Utilities District building, there was a bottled water tap.  The label read "Diamond Springs Water Co., Reno, Nevada."

San Francisco Examiner/Chronicle  Jan. 1970