5 ms·

I cannot understand why California has a water supply issue when they are located right next to the largest body of water on Earth. I think the public is much m

I cannot understand why California has a water supply issue when they are located right next to the largest body of water on Earth. I think the public is much more accepting of desalinized ocean water than they are of reclaimed municipal water.

timr 15y ago
Because it's much, much harder and energetically more costly to de-salinate water than it is to "de-poop" water. Biological contaminants can be removed using organic processes, settling and chlorination. Salts and ions form relatively strong bonds with water that are hard to separate.
joshAg 15y ago
from my survey engineering course (which engineering major should you choose?) it's because reverse osmosis is a bitch to do, especially compared to cleaning sewage or building dams. however, this isn't as huge of an issue as the article makes out because almost all of california's water goes to agriculture, and no one seems to have a problem with using grey-water for agriculture.
byoung2 15y ago
I think the public is much more accepting of desalinized ocean water than they are of reclaimed municipal water. It would be hard to justify the expense, increased energy usage, and damage to marine life that comes with desalination. It makes sense in places like Israel and Saudi Arabia, but in California there are more economical and environmentally friendly options.
wtracy 15y ago
Let's see: It takes 5kW/h to produce a cubic meter of fresh water from sea water via reverse osmosis.[0] The population of just LA is a bit over 3 million.[1] The average U.S. citizen consumes 2842 cubic meters of water per year. 5 kWh/m^3 * 8765 h/year * 3,000,000 people * 2842 m^3/person-year = 4863662 kW = 4863 MW. I will conservatively estimate that a nuclear power plant will produce 800 MW.[3] So: 4863 MW / 800 MW/plant = 6 That means we're talking about six full-size nuclear power plants running 24/7 with their entire energy output going toward desalinization to supply LA alone. Extrapolating further, I get that it would take twenty nuclear power plants running full-time to meet just half of the demand for the entirety of southern California. Does that answer your question? (I know my sources aren't all that authoritative--they are just what Google pulled up. Feel free to redo the calculations with more accurate numbers, or just to double-check my arithmetic.) [0] http://lightbucket.wordpress.com/2008/04/04/large-scale-desalination-is-there-enough-energy-to-do-it/ http://lightbucket.wordpress.com/2008/04/04/large-scale-desa... [1] http://en.wikipedia.org/wiki/Southern_California http://en.wikipedia.org/wiki/Southern_California [2] http://www.waterfootprint.org/ http://www.waterfootprint.org/ [3] http://wiki.answers.com/Q/What_is_the_average_output_MW_of_a_nuclear_power_plant http://wiki.answers.com/Q/What_is_the_average_output_MW_of_a...
- BrandonM 15y ago
  You've got the h on the wrong side of the fraction. A Watt is a rate of energy usage: 1 J/s. It requires an amount of energy that could power 100 50-watt light bulbs for an hour to desalinate a cubic meter of water. That is, the 8765 h/year in your calculation doesn't belong. From http://www.nei.org/resourcesandstats/nuclear_statistics/usnuclearpowerplants/ http://www.nei.org/resourcesandstats/nuclear_statistics/usnu..., a 90% capacity nuclear power plant can produce 7.9 billion KWh in a year. Let's round that down to 6 billion. The math is: 5 kWh/m^3 * 3,000,000 people * 2842 m^3/(personyear) / 6,000,000,000 kWh/(power-plantyear) = 7.1 power plants for LA. It looks like something funny happened in your math/numbers, but your final calculation and conclusion somehow ended up correct.

timr 15y ago

Because it's much, much harder and energetically more costly to de-salinate water than it is to "de-poop" water. Biological contaminants can be removed using organic processes, settling and chlorination. Salts and ions form relatively strong bonds with water that are hard to separate.

joshAg 15y ago

from my survey engineering course (which engineering major should you choose?) it's because reverse osmosis is a bitch to do, especially compared to cleaning sewage or building dams. however, this isn't as huge of an issue as the article makes out because almost all of california's water goes to agriculture, and no one seems to have a problem with using grey-water for agriculture.

byoung2 15y ago

I think the public is much more accepting of desalinized ocean water than they are of reclaimed municipal water. It would be hard to justify the expense, increased energy usage, and damage to marine life that comes with desalination. It makes sense in places like Israel and Saudi Arabia, but in California there are more economical and environmentally friendly options.

wtracy 15y ago

Let's see: It takes 5kW/h to produce a cubic meter of fresh water from sea water via reverse osmosis.[0] The population of just LA is a bit over 3 million.[1] The average U.S. citizen consumes 2842 cubic meters of water per year. 5 kWh/m^3 * 8765 h/year * 3,000,000 people * 2842 m^3/person-year = 4863662 kW = 4863 MW. I will conservatively estimate that a nuclear power plant will produce 800 MW.[3] So: 4863 MW / 800 MW/plant = 6 That means we're talking about six full-size nuclear power plants running 24/7 with their entire energy output going toward desalinization to supply LA alone. Extrapolating further, I get that it would take twenty nuclear power plants running full-time to meet just half of the demand for the entirety of southern California. Does that answer your question? (I know my sources aren't all that authoritative--they are just what Google pulled up. Feel free to redo the calculations with more accurate numbers, or just to double-check my arithmetic.) [0] http://lightbucket.wordpress.com/2008/04/04/large-scale-desalination-is-there-enough-energy-to-do-it/ http://lightbucket.wordpress.com/2008/04/04/large-scale-desa... [1] http://en.wikipedia.org/wiki/Southern_California http://en.wikipedia.org/wiki/Southern_California [2] http://www.waterfootprint.org/ http://www.waterfootprint.org/ [3] http://wiki.answers.com/Q/What_is_the_average_output_MW_of_a_nuclear_power_plant http://wiki.answers.com/Q/What_is_the_average_output_MW_of_a...

BrandonM 15y ago
You've got the h on the wrong side of the fraction. A Watt is a rate of energy usage: 1 J/s. It requires an amount of energy that could power 100 50-watt light bulbs for an hour to desalinate a cubic meter of water. That is, the 8765 h/year in your calculation doesn't belong. From http://www.nei.org/resourcesandstats/nuclear_statistics/usnuclearpowerplants/ http://www.nei.org/resourcesandstats/nuclear_statistics/usnu..., a 90% capacity nuclear power plant can produce 7.9 billion KWh in a year. Let's round that down to 6 billion. The math is: 5 kWh/m^3 * 3,000,000 people * 2842 m^3/(personyear) / 6,000,000,000 kWh/(power-plantyear) = 7.1 power plants for LA. It looks like something funny happened in your math/numbers, but your final calculation and conclusion somehow ended up correct.