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Wastewater

Page history last edited by Cameron 11 years, 5 months ago

What is “Wastewater”?  (revision)

 

“Wastewater” probably doesn’t bring to mind the pleasantest of images, but if you’re in Las Vegas, you’re drinking it.

 

                     

 

 

 

What may sound like a nice science experiment for a snickering, toilet-minded third grader is actually a complex process that cleanses and reuses our valley’s most precious resource. Due to this development, one spokesman for the local water authority in Las Vegas claims that his facility is able to “recapture and recover virtually every indoor drop of water in the valley.”

 

The Clark County Reclamation District has the chore of de-junking the Vegas valley’s water supply. Located on the far northeast of the city, the Reclamation District utilizes two methods to clean the water. ‘Primary treatment’ uses physical, inorganic (or nonliving) means to sift out the filthiness; the other employs biological means to remove dissolved solids and other pollutants. It is dubbed, unsurprisingly, ‘secondary treatment’. 

 

Primary Treatment

Water from toilets, baths, showers, sinks, washing machines, dishwashers, and storm drains all come together in a mixture referred to as influent. By volume it is 99% water. The remainder is sand and other larger debris, such as cans, cloth, sticks, and other flushed objects. ‘Primary treatment’ is similar in method to using a colander to strain the water from your spaghetti, and the waste your pasta, albeit slightly smellier. Large drains, grates, filters, and tanks physically separate liquid from trashy solid. The garbage is eventually sent to the dump.

 

 

After the initial filtering, the water is divvied up among several large swimming pool-size ponds called grit tanks. The water here is slowed and aerated. Incoming air is injected at a rate and angle which creates a rippling effect, lifting lighter materials while allowing grit and heavier solids to sink to the bottom. The pools are kept underground, and the neighbors are grateful. 

 

The water next heads into large basins called clarifiers. The water here is kept nearly still, allowing gravity to settle the heavier solids. Large rakes and skimming devices gather the sludge that settles to the bottom of the clarifiers and is collected and sent to a facility that processes it into biosolids. ‘Biosolid’ (also sometimes monikered ‘humanure’ or ‘black gold’) is the intentionally neutered euphemism for treated fecal material. It can be used as fertilizer to raise crops after meeting federal safety guidelines (it stops stinking then, too). Because of the increasing number of wastewater facilities and the improving quality of biosolids, the EPA cites that farmers are increasing use of this nutrient-rich organic compound.  

 

 

Secondary Treatment 

By the start of secondary treatment, or chemical cleanse, 35-60% of pollutants have been eliminated (Anne Arundel County, 2008). Once finished in the clarifiers, the water heads to activated sludge basins. Oddly, sludge from previous tanks is actually re-used, injected (‘activated’) with good bacteria, and partially put back into the tanks- it’s kind of like yogurt, except slightly more overpowering. Microorganisms are released into the tank and mixed with oxygen, where they feed on the remaining sludge. After another round of clarifiers is used to settle the floaties, the water starts to look and smell like water again. 99% of the waste is eliminated once through with these methods. 

 

 

The Return Journey 

By the end of this cleansing, the water has been altered enough that a name change is deemed appropriate: effluent. The effluent passes through another series of very fine filters, is exposed to ultraviolet rays which kill any harmful organisms leftover from activated sludge and finally enters the Las Vegas Wash awaiting you to turn on the tap water.

 

A nice cold glass may never be the same.

 

 

 

 

Bibliography

 

Anne Arundel County, M. (Director). (2008). What happens when you flush? http://www.youtube.com/watch?v=-bjbW1-lXaU&feature=related [Motion Picture].

Clark County Water Reclamation District. (n.d.). Retrieved March 7, 2009, from Clark County Water Reclamation District: http://www.cleanwaterteam.com/virtualtours6_rev.html

EPA. (n.d.). Biosolids - FAQ. Retrieved 28 February, 2009, from US EPA: http://www.epa.gov/owm/mtb/biosolids/genqa.htm

P. Aarne Vesilind, I. W. (2003). Wastewater Treatment Plant Design. London: IWA Publishing.

Schoenmann, J. (2009, February 13). Using less — but why? Las Vegas Sun.

Sewage. (n.d.). Retrieved March 7, 2009, from How Stuff Works: http://science.howstuffworks.com/sewage-info1.htm

Water Environment Federation. (n.d.). Wastewater Treatment. Retrieved February 21, 2009, from wef.org: http://www.wef.org/NR/rdonlyres/59E69C35-0E6F-4593-A4B8-D420AA9C4819/0/WastewaterTreatment912.pdf

 

 


 

 

 

Wastewater

 

 

 

Mayor Goodman:

 

Thank you for your interest in our facility. I know that a more complete understanding of what we do here will be essential for you in your endeavor to politick for increase in the valley’s allocation of Colorado River water. This document will strengthen your case, showing that our valley already manages our portion efficiently, we just need more.

 

I know that these are dire economic times for our city. Water and its intelligent usage is fundamental to our valley’s survival and growth. The City of Las Vegas could survive without neon (negating economic impact, of course), but its people could not survive much more than a long weekend without water. 

 

Southern Nevada Water Authority estimates that the average Southern Nevada household uses 144,000 gallons of water annually. J.C. Davis, spokesman for the Authority, was recently quoted in the Las Vegas Sun explaining that SNWA can “recapture and recover virtually every indoor drop of water in the valley. It hits a drain, we get it” (Schoenmann, 2009).

 

At our facility, the focus is on wastewater treatment: water cleansing and re-use.  We use both primary and secondary treatments. Primary treatment is using inorganic, or nonliving, processes to clean the water. These methods include large drains, filters, and tanks which physically separate liquid from solid. Secondary treatment employs biological means to remove dissolved solids. The most important force we harness here is gravity. It should be noted that our location sits near the bottom of our valley. Without gravity, the cost of pumping water would very nearly eliminate the cost-saving benefits of re-using water in the first place!

 

Primary Treatment

 

When water from toilets, baths, showers, sinks, washing machines, dishwashers, and storm drains all come together, this amalgamation is generally referred to as influent. By volume, this creation is 99% water, while the remainder is sand and larger debris, such as cans, cloth, sticks, and other flushed objects (see figure 1). Our primary treatment begins as the influent is filtered through large grates or screens which collect this refuse. As occurs as several points of the wastewater’s journey, this garbage is sent to landfill (Water Environment Federation).

 

 

After the initial filtering, the water is divided among several large swimming pool-size ponds called grit tanks. The water in these tanks is slowed, but also aerated at a rate such that the incoming aeration perpendiculates through the water, suspending lighter materials and allowing grit and heavier solids to sink to the bottom (P. Aarne Vesilind, 2003). This process is one of the many that can get fairly smelly. For this reason, the pools are kept underground. The water next heads into large basins called clarifiers (see figure 2). The water here is kept nearly still, allowing gravity to settle the heavier solids to the bottom of the tank. Large rakes and skimming devices gather the sludge that settles to the bottom of the clarifiers and is collected and sent to a facility that processes it into biosolids. ‘Biosolid’ is a neutered word for treated fecal material, which, when meeting federal safety guidelines, can be used as fertilizer to raise crops. After treatment, biosolids generally lose their native odor. Because of the increasing number of wastewater facilities and the improving quality of biosolids, more growers are using this nutrient-rich organic compound, including, I hear, the Gilcrease Orchard on the far Northwest end of Las Vegas (EPA).

 

 

Secondary Treatment

 

Now for the strange part. Once finished in the clarifiers, secondary treatment begins at the activated sludge basin (see figure 3). 35-60% of pollutants have now been eliminated by primary treatment (Anne Arundel County, 2008). By ‘activated sludge’, I mean that the sludge from previous tanks is actually re-used, inoculated with bacteria, and partially put back into the process. Microorganisms are released into the tank and mixed with oxygen. The microorganisms in the sludge then basically feed on the remaining sludge (Sewage).The process is repeated with the secondary clarifiers, which, similar to the first clarifiers, circulate the water through settling tanks. At this point, water starts to look and smell like water again because 99% of the waste is eliminated once through these second clarifiers (Clark County Water Reclamation District).

 

 

Sludge smells worse than rotten gin, but still contains some water. This mess is sent to a filter press, where any excess water is coerced out of the sludge. We call this dry sludge ‘cake’. Believe it or not, it has a nice, earthy smell at this point. Cake is often used at our local landfill as fill material, and is sold as a soil conditioner to farmers (Anne Arundel County, 2008).

 

Once finished at the activated sludge stage, we refer to the water as effluent. The effluent passes through another series of fine media filters, and is then finally exposed to ultraviolet rays that kill any harmful organisms that have made it to the end our process (see figure 4). It is here that the water sets on its way to the Las Vegas wash, and we bid it farewell, until another day (Clark County Water Reclamation District).

 

 

This process of reclaiming water is of such a value to our valley that the numerous benefits it stems seem self-evident. Personally, I feel the greatest value our facility gives to Southern Nevada, besides converting utter waste into drinking water, is the encouragement that comes from participating in a sustainable lifestyle.  Many find this newfound ‘green’ push nothing more than a passing zeitgeist; I firmly believe that any other option is actually not an option. We must not be enslaved by our environment, but we should be wise stewards; serving, respecting, and caring for what we cannot create on our own. What we do here isn’t particularly glamorous, considering our water’s nativity to toilets, its commingling of and with toothpaste, trash, storm water, and anything else that gets flushed, but, Mr. Mayor, any process turning slurry into (nearly) Sparkletts is truly a beautiful thing.

 

Should you have any further questions, please feel free to contact me at my office, (702) 234-1102. Thank you for your time, and good luck before the Water Commission.

  

Sincerely,

 

 

Cameron Dixon

 

 

Cameron Dixon

camerondixon@ccwrd.gov

Water Reclamation Facilities Manager

 


Comments (4)

Melissa said

at 9:06 am on Mar 31, 2009

This is amazing. This helps me understand the process of waste-water. Perhaps you should re-format this to a different audience and change the language. The description process is explained really well, but if it is going to be directed at a different/broader audience you should dumb down the language a bit.

Jenna said

at 9:08 am on Mar 31, 2009

Great process description, Cameron! You laid out everything in a chronological order and it's easy to follow what you're talking about from start to finish.

To make your description better suited for the wiki project, you need to address your document to a broad audience rather than just Mayor Goodman. He also obviously has a much higher reading level than the people you'll be appealing to in your wiki project. Other than that, I think you've got it covered.

Jenna said

at 8:56 am on Apr 21, 2009

Wow Cameron! I really don't have any criticism. I think you simplified your description enough so that it's suitable for a general internet audience, and the humor you inserted made it very interesting. The only thing I would recommend is changing your sentence on aeration under the "Primary Treatment" section - maybe combine that sentence with the one that immediately follows it for more clarity.

Melissa said

at 9:10 am on Apr 21, 2009

Hey, what's up Cameron?

This is Melissa.

I think your description is really well written. You have definitely dumb-downed the language, though it still sounds extremely intelligent. The process is clearly explained and I do not feel confused or baffled by anything you have described. I think you also did a good job of keeping your target audience in mind throughout the description so there is a nice even flow of information from start to finish.

Everything is nicely organized under it's appropriate heading, making it easier for the reader [well, me actually] to understand what I am about to learn.

I think you should include the graphics directly in this revision, however. The pictures will help the reader acquire a better image of what the process really is (though I think the whole smelly yogurt description does a pretty good job.)

All in all, high fives for you.

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