Toilet-To-Tap....

[Darian]

Interesting article in todays SacBee reports that there's a little known plant in the San Diego area is treating waste water using long existing technologies to produce potable (drinking grade) water at a cost of $13 million. It's reported that this plant produces 1 million gallons of cleaned water a day. The National Academy of Sciences said, in a recent report, that if coastal communities used the advanced techniques involved, they could achieve an increase of 27% in available water. Obviously, the cost involved in using this process has reached the point where buying water from resellers costs more than producing cleaned water. 8) I was unable to find a link to the article on the Bee's website. :\\

Once again, the southern California area is ahead of us in exploring technologies for water conservation. 8)

Most recycled water is used for application to golf courses and recharging groundwater, etc. One of the reasons that treated drinking water has not caught on is the "YUK" factor. Most people are put off by the thought of drinking recycled water no matter how clean it is. :neutral:

One area of potential for this process is cleaning agricultural drainage and groundwater that is unusable for irrigation due to contamination (salts in the soil), as in the aquifers under Aera Energy oil and adjoining agricultural fields. It won't happen unless the current cost to benefit ratio changes to provide some type of incentive. :)

[Larry S]

Plant has been there for some years now. Located just NE of where Miramar Rd
crosses I-805. From time to time, businesses to the east experience a noticeable
"dairy-air" aroma. Some is used for irrigation in the area; purple fixtures note the
usage. I think most of it still heads to the ocean, which is a shame. Just across Miramar
Road, is the new Miramar National Cemetery. They've really done a nice job on this
facility. Pt Loma's Rosecrantz(sp?) Nat'l Cemetery is now at full capacity.
On another note, construction still hasn't started on the desalinization plant at
Carlsbad. We should be building more of these. Yeah, they do require lots of energy.
Still, the water should be the issue.
Best to all,
Larry S

[Darian]

Hmmm,.... I guess the methane (gas :puke: ) produced would make it necessary to live upwind from the plant.... ;-)

I agree that water is the issue. The Poseidon DeSal project, slated for that area, was designed to co-locate with an existing power generation plant using the intake/cooling/outlet pipes. That seems like a doable solution. However, that facility has been opposed. The main (among several) objection has been the briny by-product. Don't know what the current status of it is.... :confused:

It's a bit confusing to see that objections are raised to DeSal in part because of the brine produced from sea water. Yet, nobody's objecting to the salt flat evaporators in the south-east side of SF Bay. People put sea salt produced through that process on their food as a gourmet item. :confused:

Oh Well,....

[Mike O]

I gots an idear...
Mix the grey water from the recycled poopy water (which iggerant people won't drink) with the salt brine from the desal, THEN pump it to the ocean at a better salinity. Two pobs solved.

But in reality, the ocean overcomes a lot...as evidenced by the thermal plumes from coastal power plants up and down the coast

[Darian]

I can understand the objection to the potential destruction of sea life thru being pulled into the sea water intakes but am confused by the objection to discharge of a natural by-product of desalinization of sea water back into sea water. :confused:

It seems like the remaining brine, in concentrated form, can be easily discharged further offshore and spread over a large area, resulting in dilution to normal PH levels.

DeSal has a lengthy history of use in other countries (Israel, etc.). There should be some information available about how they've dealt with the problem.... 8-)

[Mike O]

I gotta believe that the cost of spreading the brine over a large area, far offshore would be pretty expensive. Since the brine would be most likely pumped out along the seafloor at considerable depth, it may not go back into solution due to pressure and temperature. If you send it far enough offshore to get it into the abyssal plain (pretty far out) it most likely would never mix well. If one pumped it out shallower, unless it was spread out considerably, I gotta believe that it would wreak havoc with the life found there.

This is all my .02

[Darian]

A bit of history/perspective may be in order here. According to the International Desalination Association, there're 14,451 desalination plants in operation worldwide; producing 59.9 million cubic meters (15.8 billion gallons) per day.

The largest plant in the US is located at Tampa Bay, FLA and is operated by Tampa Bay Water. As of December 2007, the plant produces 34.7 million cubic meters of water per year.

Some of the technologies involved are low temperature thermal DeSal (evaporation and condensation currently used in greenhouses to irrigate some crops), a thermo ionic process and membrane osmosis. There're more but I'm not sure I understand them well enough to write about them. An outcome of the DeSal process is that there will be less briny water to discharge than the volume taken in.

Of major concern in all plants is the brine produced during the DeSal process. A couple of the solutions used to address this have been reducing the amount of salt in the discharge by retaining it for table use and discharging the brine in to the sea.

The first is already done thru evaporators along the SF Bay shoreline. The condensation just isn't captured but tends to prove viability. The second is already done by using pipelines with a diffuser(s) and/or branches that end in areas of the sea floor with enough current (tidal or otherwise) to cause dispersal. Yet another method is to dilute the brine discharge with grey water. Haven't found anything yet discussing the impact of these methods on the ocean.

Destruction of fish thru intakes is addressed by screening or reducing the speed of the intake water to a level that will allow fish to swim away (33' per second was mentioned). Of course, this doesn't address the smaller forms of sea life that could be taken in....

That should settle the concern that DeSal is relatively new technology (mentioned in other threads) and is enough for now.... :|