Haberler

Waste water reinjection at The Geysers with positive environmental impact

Alexander Richter 30 May 2009

Waste water reinjection for the sustainability of geothermal reservoirs seems to have a very positive impact on the local river system at The Geysers in California, and is claimed to be "the biggest reason the Russian River is free of Santa Rosa's wastewater this past year.

With the over-utilization of the geothermal resources at The Geysers in the eighties, the power plants have not produced as much electricity as the technically could. The reservoirs simply didn´t provide enough water. So in 2003 a “wastewater-to-electricity” project was completed that would “refuel” the reservoirs.

So recently reported in California, this seems to have a very positive impact on the local river system and claimed to be “the biggest reason the Russian River is free of Santa Rosa’s wastewater this past year.”

The article goes on describing that “the steam fields, which convert wastewater into steam to generate electricity, consumed 65 percent of the highly treated effluent generated by Santa Rosa, Rohnert Park, Cotati and Sebastopol and pumped to The Geysers over the past year, city records show.

Before The Geysers’ wastewater-to-electricity project was completed in late 2003, most of that effluent would have gone down the river during winter months.

“I had a gut feeling when the city picked The Geysers project it would be a really good thing,” said Brenda Adelman of Guerneville, a river activist. She has been at the forefront of demands by river residents that the city dramatically reduce its river discharges.

“It’s turned out better than I anticipated. It’s so much better putting it there than in the river,” she said.

Since the US$300 million project, a partnership between the city and Calpine Corp., became operational, the city has pumped 21 billion gallons of effluent from its Llano Road sewage treatment plant to the steam fields high in the Mayacmas Mountains northeast of Healdsburg. The water is injected deep underground to produce steam to generate electricity.

Dennis Gilles, Calpine’s senior vice president, said the effluent now generates 96 megawatts of steam-generated electricity, or about 10 percent of the 1,000 megawatts the geothermal area generates.

That’s enough to power 96,000 homes or the combined daily residential needs of Santa Rosa, Rohnert Park and Petaluma.

Gilles said the wastewater has done one more important thing: It has re-energized the steam fields, which literally had been losing steam because of the lack of sufficient rainwater to replenish underground aquifers.

“It’s been a win-win,” said Gilles, whose company spent more than $100 million to develop a series of injection wells, distribution pipelines, storage and generating facilities to handle the flows within the 30-square-mile steam field area, the largest concentration of steam fields on Earth.

The city originally signed a contract to provide Calpine with 11 million gallons of wastewater a day, or 4 billion gallons a year, but upped that amount two years ago when it reached a new agreement.

That contracts require the city to provide Calpine with 12.6 million gallons of effluent on average per day but calls for a gradual increase up to 16 million gallons, or 6 billion gallons a year, over the next two to three decades.

By then, Gilles expects the increased flows will produce up to 150 megawatts of electricity, roughly enough to power the residential needs of all of Sonoma County.”

So this sounds like a win-win situation for this beautiful wine area of California.

Source: The Press Democrat