Marin water board considers turning to bay for future needs (desalination)

[XemaSab]

For a mere $115 million, homes in Marin County could soon be sucking de-salted bay water through their taps, according to an environmental report scheduled for release this week.

The Marin Municipal Water District on Wednesday will present a draft environmental report on a proposed desalination plant, becoming the first water agency in the Bay Area to seriously consider using San Francisco Bay for drinking water.

The district's 190,000 customers in southern and central Marin will have considerable say over whether water district directors eventually decide to build the plant, in part because the ratepayers will likely end up financing the construction through taxes or higher water rates, officials said.

"It's a great deal of money. It's a great deal of energy. On the other hand, it's a reliable water supply," said Cynthia Koehler, the water district board president. "We need to have that kind of conversation with our community."

http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/11/05/BA52T5KUI.DTL

[Trillo]

1. A professor has proposed large-scale commercial solar desalination.

His theoretical figures indicate it would cost about half as much as Reverse Osmosis.

A theoretical proposal is outlined for large scale solar desalination using multi effect humidification. It involves the use of a large area solar collector, multi effect distillation and boiling at reduced pressure. The configuration devised is a circular tank of one kilometre diameter containing water to a depth of 10 metres with a sealed double glazed dome, operating at 0.1 atmosphere pressure with a working temperature below 50° C. A solar absorber placed just above the water level, abundantly perforated but covering the entire area, sets up convection currents that evaporate the sea water and condense the vapour. Incoming seawater recovers energy from outgoing clean water and brine in a counter current heat exchanger. Water flow is driven by solar distillation and hydrostatic pressure. It is estimated that the structure would have 95% energy efficiency and a gained output ratio of 20. In sunbelt countries with average isolation of 6kwh/m2/day the desalination plant would produce 100,000 m3/d distilled water at a speculative cost of $0.28/m3.
http://www.globalwarmingsolutions.co.uk/large_scale_solar_desalination_using_multi_effect_humidification.htm

[tom_paine]

2. Marin County is waterboarding. Those torturing bastards!

:silly: