Thursday, October 14, 2010

Blog Action Day 2010: Our water footprint

I walked my watershed for Blog Action Day 2007 to show where my water comes from and where it goes. This time, I will show one stop of our water cycle in detail.

Last November, I had the opportunity to chaperone my daughter's class when they visited the West Basin Water District's Edward C. Little Water Recycling Facility in El Segundo, California.

Here's a Google Earth view of the area.  Most of the waste water from western LA county goes to the Hyperion Sewage Treatment Plant for removal of solids and biological treatment with bacteria that eat the smaller particles before settling to the bottom of the holding tanks.  The water is then pumped to the water recycling plant marked by the red asterisk (*).
The world's second largest Whole Foods (marked with the red WF) is adjacent to the water recycling plant, proving that there is absolutely nothing smelly or off-putting about the place.   Some of this country's most expensive real estate is in the southwest corner of this picture.

Notice the density of the residential neighborhoods.  The small plots save tons of water, both because we use less for landscaping, and because of the embedded water in the gasoline we don't consume.

Here's one of the giant tanks on the site.  I am not sure if this is the beginning or the end for the water's sojourn here.

The water goes through a two-step filtration process, first traveling through hollow fibers held together in these rods to remove the larger bacteria and viruses.
It gets scummy looking during the process.
A dispersant agent is used in this step to keep things free-flowing.

The water then undergoes a second filtration, using reverse osmosis through these filters.  The water is pushed with high pressure from the outside to the inside.  The clean water flows out of the center tube.
Here are some filter rods awaiting use.

These are in use.
This removes the smaller bacteria and viruses as well as salt and some pharmaceuticals.  Yup, we collectively take a lot of drugs (both legal and the other kind), excrete them, and then flush them down the toilet.  It all ends up here.

The water is then treated with ultraviolet light to break up the pharmaceuticals and kill any viruses that survived the earlier processes.  UV treatment can create radicals, which are corrosive to pipes.  The water pH is adjusted with lime as a buffer agent to prevent that.  See the characteristic blue-green lime color of the treated water? 

It reminds me of the swimming holes at the base of the water falls in Havasu canyon.  (Havasupai means people of the blue-green water.)

OK, now let's talk about recycling.  The outflow is piped around the Southland for landscape irrigation, flushing and other industrial uses (like cooling water at the many refineries in our region).

It's no accident that the Chevron refinery and two golf courses are located so close to the water recycling plant.  They use reclaimed water.  In fact, many office buildings in our region use reclaimed water for both outdoor irrigation and flushing toilets.  LA Air Force Base and Toyota USA Headquarters are two notable sites.

We also sit upon a giant aquifer, which we pump for drinking water.  During the rainy season, rainwater percolates down to recharge the aquifer.  (Actually, too much of it runs off into the storm drains before they get a chance to percolate into the ground, but that's another discussion.)

At the coast, it is always a battle against salt water incursion into the fresh water aquifer.  That's why we have built a line of injection wells (blue dots) along the coast.
The treated waste water is injected at the bottom of the aquifers.  We also pump water from the top of the aquifers for drinking water.  About 30-40% of my local water supply comes from these wells and directly from the recycling plant. 

At the plant, they are careful to show the injection wells and water source wells on different pictures.  ;-)   Perhaps they think we will be grossed out?  I am not bothered by it.  In fact, I am proud of the ingenuity demonstrated in this water recycling plant.

Did you know that 20-25% of California's electricity usage is to move water around?  The more we recycle our water, the lower our carbon and water footprints.

As we walked around the plant, I found many golf balls
that had escaped the driving range next door.

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5 comments:

  1. Really cool post.
    Do you know what they do with the filters after they are used? It looks like the interiors could be composted, and the shells refilled with filter paper. I assume they need changing perodically so they don't become clogged.
    I don't know as much chemistry as you do, but I would guess that getting the organic chemicals, the bacteria and viruses are relatively easy to do with good filters, followed by charcoal, followd by UV. But I would think small, soluable, inorganic molecules like heavy metal salts might be harder to get. Of course there's very little reason for any of that get poured down a sanitary sewer. Presumably they monitor for that sort of stuff.

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  2. I was wondering the same thing about the filter disposal/recycling.

    Heavy metals can be removed with chelation and reverse osmosis. I don't think they mentioned chelation to the school kids, but I assumed that it is one step in the process.

    I will call the public information officer at the water plant to ask.

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  3. Does chelation take the heavy metals out of the water, or just bind them into nontoxic compounds? I could imagine that there is actually very little heavy metals in the waste stream. There shouldn't be any in human wastes, or in modern-day cleaning agents. Maybe in older cities where there the water still flows through lead pipes in some houses? That would probably be pretty small. Some wells are naturally high in arsenic, but I suppose an "off-water-grid" house that has its own well is likely also to have its own septic field. Maybe if water were used to pressure-strip lead paint were then allowed to run down a drain. Perhaps heavy metals are something they don't need to explicitly treat for, but just monitor to make sure there isn't a spike from some sudden source of contamination. At the levels you'd ever get in a highly diluted sysyem like our water supply, the risk is only over the very long term. Whereas bacteria and viruses can pose an acute risk.

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  4. You can precipitate out the chelates. But, if I recall correctly, reverse osmosis can remove salts and metals.

    http://en.wikipedia.org/wiki/Reverse_osmosis

    The solids are removed at the Hyperion plant, before it gets to the water recycling facility. The solids were sent to Kern county and spread on agricultural fields as fertilizer. But, then it was discovered that the biosolids actually contained dangerous wastes in higher concentrations than allowed. Kern county sued LA county to stop the shipping of biosolids to their county. Everything is complicated, even shit.

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  5. Very interesting post. Clearly, Southern Cal has good reason to do whatever it can to conserve water. I wonder what Mexico City is doing.

    On an entirely unrelated matter, can you tell me if chelation is a good alternative to salt for a residential water softener?

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