A couple days ago on Morning Edition, I heard yet another story about how tap water is now dangerous. This time the story was about Congress starting a series of hearings on the findings that tap water in various cities was found to have minuscule amounts of multiple prescription drugs, and included a scientist who said that although tests had determined that people were not affected by such minute amounts of individual drugs, it was not clear what the results could be from ingesting the combination of all of them.
Now I'm normally concerned about pollution, and the idea that our water is laced with random medications is kind of scary. But the more I hear about it, the more I get frustrated. First of all, the proportions of chemicals they're finding are tiny - so much so that we are only able to trace them now with the latest equipment; just a few years ago we wouldn't have even known we had this problem. That doesn't make them safe, but it does mean we're in a media-induced frenzy over something that likely has been going on for a long time.
Second, water is one of the few truly recyclable resources, as many drought-ridden cities are starting to realize. Cleaning and filtering sewer water, while it definitely has the "yuck" factor, is much cheaper, takes less energy, and has fewer bad byproducts than de-salination, which somehow seems so much less gross. Desalination is extremely energy-intensive, which is why it's generally done only in oil-rich, water-pour Middle-Eastern countries. Furthermore, Ocean water isn't actually all that clean - there's a whole lot of raw sewage (thank you, Victoria and Mr. Floatie, among other places!), garbage, and salt. And after they de-salinate and remove that briny, gross stuff, what do plants generally do? Throw it back in the ocean, of course, so the problem just gets worse. Cities like San Diego are finally figuring this out and building sewage to tap plants despite public concern.
Clearly we're not going to get away from this problem. There's less "clean" (i.e. evaporated, rained down, and filtered through some rock into a stream or lake) water available and more people who want to drink it. We can do better at conserving by reusing our grey water for gardening and other non-potable needs, but ultimately we need to drink. The only alternative I can think of is for all of us to start drinking mead. Either the alcohol will kill off anything bad in the water, or if it can't, at least we'll all be happier.
Friday, April 18, 2008
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Several news articles on seawater desalination reveal that desalination technology is little understood by most journalists, local water managers, politicians and environmental groups. In searching for renewable potable water or supplementing current sources few are aware that there is more than one desalination technology.
When evaluating a desalination project Reverse Osmosis is typically the process considered. Yet, there is a viable and proven alternative in distillation with lower costs.
The Advanced Vapor Compression Desalination Process is an advanced and highly environmentally friendly desalination process, an alternative, single performance, and lower maintenance process compared to Reverse Osmosis. The system is based on proven flash distilling principles but features an innovative, highly efficient, and compact design. Additionally, it offers a unique advantage in the treatment of salt byproducts.
The system produces outputs of either valuable crystalline salt or concentrated brine. The
process is optimized for the desalination of seawater drawn from wells below the sea floor and not returning the brine to the sea. The process has modular abilities and can be expanded to meet future requirements in water demand or designed and built at the start for higher volume. A basic plant design can operate on solar, thermal, nuclear or traditional energy sources. Each unit is optimized from an initial engineering site study to account for different environmental and structural needs. A basic stand-alone unit of 1 acre-foot per day has a footprint of approximately twenty feet in diameter. The larger the plant water volume the lower the cost is per acre-foot. The plant energy consumption is on the order of about 4 to 20 kw per1000 gallons produced based on the design, volume produced and type of energy.
The system can also be used in industrial treatment and recovery of effluent water. The life cycle of the plant is based on a 25 year time line which can be extended through proper preventable maintenance and overhaul.
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