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Desalination Plant Begins Operation in Tampa
ambisinistral writes "The Tampa Tribune reports that the first commercial desalination plant in the U.S. is set to begin operations today. By March the plant is expected to be operating at full capacity, producing 25 million gallons of fresh water a day (10% of the water currently provided to the area from well fields).
There are ecological concerns about returning highly saline water from the plant back into Tampa Bay. Proponents of desalination claim the natural tide cycle will effectively flush the bay of the saline rich discharge, while opponents of the plant feel the ecology of the bay will be badly damaged. Both sides plan on strict monitoring of the situation."
Since the feds have strictly curtailed California's ability to take water from the Colorado River, California needs to build desalination plants like this one, and to do it quickly! Too bad they will take 10 or 20 years debating it.
How ya like dat?
Evaporating the brine might be cost efective if the city of Tampa has an in-house use for the salt. If they were located in the snow belt, for example, it might be used for snow/ice removal.
--we use solar PV here, and have three battery banks. Needing a lot of distilled water every month, we got a commercial solar distiller, which is mounted down by the panel arrays. It's roughly a 3 foot by 5 foot box with a glass top that is sealed to the sides. It worked pretty good for around a year,2-3 gallons a day output, then it stopped working, the glass developed some recurring film that stops the drips from falling into the collection tray. We tried adjusting the angle, etc, opened it up, cleaned the glass several times-nada. It evaporates water great,that part works as advertised, then the water that collects on the glass just sits there until the weight of the droplet causes it to fall right back into the pool of water, instead of sliding down the incline. So we switched to an electric distiller for now, next summer I'm going to make a hot water heater out of the thing and design and build my own distiller. The glass cleaning deal really stumped us, we tried vinegar, windex, you name it, that glass is spotless clean, but within a day or two it gets dirty enough to stop working-just unacceptable. There's probably some sort of application chemical like rain-x or something to use but it's a hassle to keep doing that, it should "just work" for at least a month without having to open it up for additional cleaning. I imagine on a bigger scale it would actually work better as you could have extremely steep sides for the collection efforts.
There's a neat deal that was invented, it uses rotating sails to collect moisture from the air, some places in south america are using it now. this was covered on slashdot before earlier this summer, here's a generic link to a page of links about fog collection. cool stuff.
As opposed to the crap they dump into the bay every time it rains hard?
I used to work for a research institute that monitored tidal conditions along the Texas coast. One thing we did was monitor salinity and dissolved oxygen levels in the Corpus Christi and Nueces bays. It wasn't from desal plants, but from the Nueces river being dammed in, limiting it's flow into the bays. This caused salinity to rise, and dissolved oxygen to decrease, putting the local wildlife in danger. They used our measurements to schedule releases--times when they would open the dams and dump X amount of fresh water into the bay in order to correct the levels. As far as I know, it worked just like it was supposed to.
I haven't looked up any maps of the area, but surely there are similar factors at play.
Your last point is the key to how very efficient distillation systems work.
You put the heat into the water to make the vapor.
Then you take the heat back out of the vapor to get pure water.
Using the heat from step 2 in step 1 is how you get high efficiency.
Since the two temperatures need only be on either side of the dew point, you can run the system at any average temperature you like. Instead of heating the water to make vapor, you can cool the vapor to make water.
One scheme pumped cold water from low ocean depths to chill air below the dew point. Pumping water is cheap compared to raising the temperature.
As for worrying about high salinity, that need not be a problem. You need only remove enough water that the salinity changes by one or two percent (i.e. from 0.0035 to 0.0036). The seawater can be continuously pumped through the system, with only a small amount of water removed at any one time.
Free book: Science Toys You Can Make
Proponents hyped both as solutions to the crisis, even though the CWP never delivers to full capacity when it is most needed (during a drought), is much more expensive than was originally stated, and the desalination plant was never used yet must still be maintained yearly.
In fact, the largest proponents of the addition of state water and the desal. plant were developers, who saw a way around the county's long-standing moratorium on new water hookups (the county essentially running Mulholland's famous "whoever brings the water brings the people" in reverse to keep development at bay).
In general, Marc Reisner's "Cadillac Desert" is a good review for those interested in the politics of water in the West. The issues faced by the semi-arid West are starting to appear elsewhere in the U.S. as our population grows, and we would do well to learn the lessons of the past.
Can't you see that everyone is buying station wagons?
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