Thursday, March 19

Hi-tech wastewater recycling: Can it save enough water to save California's agriculture?

Ocean water desalination, and other extreme measures such as towing giant bags of water across the oceans to drought-stricken regions from ones with plentiful water, tend to run up against human nature's weaker side. Instead of seeing these measures as a warning to trim water-gulping expansion plans, business and governments use the extra water supply to continue recklessly increasing their usage of it. While often not paying attention to the basics of water conservation, such as repairing or upgrading leaky water infrastructures and closely monitoring water usage. 

But the bottom line, as a California politician once noted, is that you can't conserve what you don't have.  If a region's water supply falls markedly, all measures to conserve water at most stave off the inevitable for a short time.    

This said, the most advanced method of purifying sewage water is amazing -- relatively simple in its technology and can save whopping amounts of water.  

Waste water recycling for limited use has been in use in San Jose, California since the late 1990s.  But last July the San Jose Mercury News reported on the opening of a hi-tech water purification plant that can actually transform raw sewage into very safe drinking water.  (The relevant California laws, created before the advances in technology, forbid this use of recycled water but this could be changing within a few years.  See the report.)

The report, written in nontechnical fashion. is a must-read for anyone interested in water conservation and drought issues.  But here I've posted only two graphics included in the report. They show at a glance how the hi-tech purification works and how much it costs relative to other water conservation measures.  

I've also included the link to the comments in response to the article; some are quite interesting and the first one is so funny I'm tempted to quote it in this post, except one has to know a little about California's salinity problems in the Sacramento San-Joaquin Delta estuary to fully appreciate the sarcasm.  I will get to a (short) discussion of those problems eventually in a future post.  

However, I do have one question after oohing and awing my way through the report.  The purified water produced by the hi-tech process is essentially distilled water, or very close to it. Distilled water doesn't contain minerals. I learned from visiting an 'Ask Us Any Dumb Question' website that rainwater doesn't contain much minerals, either. Snow, it turns out, is actually a mineral, although it's not the kind we generally think of as a mineral.  

Moving along, my question is whether huge amounts of distilled water poured into the soil in a very low rainfall region will over time dilute the soil's mineral content to the point where it doesn't support crops -- or produces crops so low in mineral content that they're not healthy.     

After trying for a half hour to find a website that dealt with my question, I came up dry. Maybe someone else will have better luck with keywords. 

And it's possible that even if the mineral content in soil would be greatly diluted, it would happen over a long period of time, and be offset by factors such as mineral-laden blowing sand and dust settling into the soil, and could be further offset by composting and chemical soil additives.  In such event it doesn't seem there would be negative effects of large-scale use of purified water for agricultural purposes.  

Although I would also want to know if pouring huge amounts of distilled water into freshwater sources and even salt water would over time create an imbalance in the salinity.  

Yes I'm being picky. But you know how we are as a race.  Once we get hold of an idea that looks like the new promised land we go hog wild. Then a quarter century or so down the line: 'Uh oh. We overlooked something.'

Now it could be that the simple fix for any such problem would be for the hi-tech recycling plant to add some minerals to the purified water. But to my knowledge this hasn't been done as yet.
California drought: San Jose's new high-tech water purification plant to expand recycled water use
POSTED:   07/17/2014 07:02:34 AM PDT 16 COMMENTS| UPDATED:   8 MONTHS AGO
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