Sandra Dibble’s latest on the proposed Rosarito Beach desalination plant highlights a point that’s central to the introductory water policy and management class I help teach (/me waves to WR571 students!). Getting the technical stuff right in water management only gets you part way down the road. Getting the institutions right can be a bigger challenge.
If you look at a satellite image of the greater Tijuana-San Diego metropolitan area, you see a huge blob of a city. Add in a map layer that shows the legal geography, and suddenly there’s a sharp line down the middle – the U.S.-Mexico border. Managing natural resources across such boundaries is an extraordinary challenge. You have resources in common. You often have populations in common (less so since we’ve gotten all wall-obsessed, but until recently moving back and forth in these big border twin cities was the norm). But you have very different institutional structures bumping up against one another.
(The 1995 study of the twin cities of Nogales by Helen Ingram and her colleagues, summarized in the book Divided Waters, is a great example of this stuff.)
Dibble’s story talks about the effort underway on the Mexican side of the border to build a really big desal plant. I don’t know enough about the technical and financial details to know whether this makes sense. But what caught my eye, in terms of the institutional arrangements, was this:
The desalination plant would ensure the Tijuana-Rosarito Beach region’s water needs are met for the next 50 years, said Oscar Gracia Valencia, who heads the public-private partnership unit in the Secretariat of Infrastructure and Urban Development.
North of the border, the Otay Water District has been closely following the project’s progress. The water agency, which has more than 220,000 customers in southeastern San Diego County, is hoping to purchase some of the water to diversify its supply.
I pay attention to this stuff because all these communities, on both sides of the border, are heavily dependent on Colorado River water. Which, y’know, is a hobby of mine. So the potential for new sources of supply that reduce the pressure on our beloved, beleaguered river tend to catch my eye.
Moving water across an international border like this is an extraordinary institutional challenge. It will be interesting to watch the progress of these discussions.
I agree with your words regarding the institutional challenge. A concern on my part, however, is: what technology will be used for desalinization? I worked as an R.O. Maintenance-Operator for a major beverage producer, and one of our biggest challenges was, what to do about the brine (concentrate) produced by the process? We installed and operated a Recovery R.O. skid, which recovered upwards of 60% of our concentrate discharge, but the consequence was a brine much higher in mineral salts as part of TDS. Disposal of the effluent was not entirely problematic for the company, as it was returned to the municipal wastewater treatment system, but a larger operation could present some issues of greater significance. Thoughts?
Kevin – I haven’t followed his plant closely enough to be sure of the answer to your question, but past discussions of the plant, and practice elsewhere in these big coastal desal plants, suggests probably RO with brine returned to the ocean.
Kevin,
You raise an important question: What to do with RO concentrate? As a postdoc at UNM in the Civil/Environmental department researching RO, this is one of my biggest questions as well. As John mentioned, costal desalination facilities typically discharge to the ocean because it is inexpensive and convenient but this approach is being phased out in Florida. More states may do away with ocean discharge in the coming years, but don’t hold your breath. Problems are most dire for inland facilities where ocean disposal is not an option. These facilities typically dispose of brine via deep well injection. As long as RO exists, brine will also exist.
There are some novel ideas about brine management that give hope though. Something I am curious in using a technology called bipolar membrane dialysis. With the use of a very novel membrane and some electricity, acids (like HCl) and bases (like NaOH) can be generated from just salt water. As you’re probably familiar with, RO operation and maintenance consumes quite a lot of acid and, depending on the system, even bases. Generating acids/bases onsite would (theoretically) lower treatment costs as they wouldn’t need to be trucked in. Currently though, the technology is in its infancy. Membranes are unstable leading to short lifetimes and high costs.
Other ideas are to precipitate and recover salts (through a proprietary process). This concept has been scaled up and the company Enviro Water Minerals Company has been contracted by the El Paso Water Utilities and will operate next to the Kay Bailey Hutchison Desalination plant in El Paso, TX (http://www.epwu.org/public_information/news_releases/nr_150608-01.html).
Hope this helps!