Here is a wind-powered graywater evaporation device for your Burning Man camp. It will eliminate, legally and responsibly, all the wastewater produced in a medium-size camp, or several small camps. (Except for what belongs in a porta-potty.)

Burners dispose of their graywater in many ways, from "pack it out" to black-plastic-lined evaporation ponds to fullblown water-purification systems designed by professionals (who make coffee using their secondhand water!)

This device, the Gray-B-Gon evapotron, is the result of many years of using and improving. With typical winds, it evaporates or disperses fifteen to twenty gallons of water a day. (Maximum measured: 2 gallons per hour in high wind. Don't try this at home.) The rotating drum design avoids two performance killers of passive evapotrons: loss of wick absorbency, and reduced performance due to accumulated playa dust. Dust just washes off the Gray-B-Gon's drum, in a single rotation.

It's useful, and it's attractive! The flashing propeller blades and the slow-moving drum catch people's attention. The (almost always) excess capacity lets you offer graywater disposal to nearby camps, forming a neighborhood center the way village wells have done for millennia, only backward.

There are five subassemblies: the tray, two masts, the drum, and the propeller. During construction, you will assemble a complete evapotron (except for the black plastic tray liner and the panty-hose filter.) Once you've tested it in some wind, and it works, you can dismantle it (dismount the propeller and masts, and collapse the drum) for transporting to the playa. There, setting it up and putting it into operation takes under an hour.

As you prepare to leave the playa you dismantle it again, then lift the muddy plastic liner from the tray and dump it into your trash bag. With a water-spray cleaning, another old towel and a new plastic liner, your evapotron should be ready to go next year.

A word of caution

While you're enjoying watching and using your evapotron, keep in mind that graywater is unsanitary and can be hazardous to your health. Step 32 describes periodic disinfection with chlorine bleach. The subassemblies you take home are unsanitary too; but so is a handshake, or sharing eating utensils. If thinking about this makes you want to wash your hands, do it.

Time and Money

On your own, construction takes about a day or three. It uses common tools that are probably in your garage or shop, plus two or three you might want to buy. Materials cost varies, depending on what you have on hand, up to about $225.

Alternatively, join one of our one-day construction workshops, where we provide most of the parts at cost (around $75 including bike wheels) and the wood parts are precut. The construction time is one full day, less if you have friends helping. You provide a bucket and panty-hose.

Further Information
This guide has recently been revised to correspond to construction improvements and simplifications. Many of the illustrations have not yet been revised to match.
Please visit evapotrons.info , which contains discussions, workshop dates, and other useful information. 8/14/13, 8/14

Step 1: Varnish -- the Secret of Long Life

A coat of varnish on wood parts will greatly extend their lifetimes. The desert is tough on wood, especially end grain and plywood edges. Your evapotron will last years longer if, before it's assembled, every wood part is sealed inside a plastic skin.

The finish I use is a water-based exterior polyurethane with a matte or satin finish (non-glossy). Water-based Varathane is one such product; it costs about $23 for a quart can (enough to cover three evapotrons). It's easy to apply, and doesn't require a skilled hand. You can coat all sides of a piece at one go, resting the piece on points or edges (just not a face) to dry. It dries rapidly to the touch; if you do your varnishing just before lunch, when you return the surfaces will be dry and workable. Water-based polyurethane has very little odor, and brush cleaning is easy. Do rinse out the brush thoroughly, several times, in clear or soapy water. Or,if you're going to do more varnishing the same day, you can put an unrinsed brush and a damp paper towel in a plastic bag, squeeze out the air, and refrigerate it.

Newly coated pieces will feel even rougher than before; that's because the surface fibers of the wood are now stiffer. A few strokes with sandpaper or a sanding block will smooth them down nicely.

<p>Hi!</p><p>I just completed one! I did something a little different for balancing the propeller. I cut the length of copper wire and then coiled it tightly around the spoke at the lightest point on the wheel. Then I slid it along the spoke, lightly spinning and waiting for the wheel to stop, until I found the balance. Then I put a very tiny drop of gorilla glue on the ends to hold it in place and re-spun the wheel to ensure the balance remained. I must add that this wheel was not far from balanced to begin with. It is going out to the Playa this year!</p>
when i first saw the picture of your work i was like is this a self sustaining morbigyro but then i saw the word burning man now i understand its use i would guess that it is extremely effective especialy using the twine as an absorbancy medium very nice
Hi Larry, <br>I am constructing the drum with two rims, both with free hubs and both used as connection points to the PVC. The two rims rotate freely in opposite directions. Is there something else I am supposed to do to the rims or is this the correct orientation? <br>-Bryce
Bryce, on the drum, freehubs are useful not because they rotate, but because they hold the pvc axle pointing in the right direction. The next construction steps, diagonal bracing and then lacing, eliminate independent rotation. You say what's diagonal bracing? It's a new construction step that tripped over an Instructables cache malfunction. All ok now, but viewers had to wait a while to read about it. Check the date at the end of the &quot;Intro&quot; step; it should be no earlier than August 2013.
Gonna give this one a try, thanks Larry for sharing. I did a few extra steps on mine. I sealed all the inside joints with window calk and then sprayed the inside of the tray with flex-seal to give a little extra protection against leakage on the playa. Thanks again.
Thanks, pintoc2. Did you build yours from scratch? Should I mail you your own laminated &quot;Gray-B-Gon lady&quot;? <br>Are you doing the sealing so you won't need a plastic sheet liner? The virtue of the liner is that when you lift it out by its corners, you carry away all the playa mud and moop picked up in a week of operating. Without the liner, you've got the icky job of scraping clean the tray's inside. If you're protecting against pinhole leaks, if you can get your device dried out and the leak wiped clean, a duct tape patch serves surprisingly well.
Larry, Aurum and I &quot;kevlar&quot; used this Gray-B-Gon system last year. Thank you so much for the instructable. Even though the wind was not as persistent as we may have wanted we still were able to evaporate plenty of water out on the playa. Due to the fact that we were near a busy street at the corner of AEZ we even had people dropping off some of their gray water into our system. We cannot make it out to black rock this summer due to moving etc, but we will be back with our system next year. Hope to see you there. If anyone is deciding on a water evap project for burning man just stop and build this. It works great.
Well, thanks much, Aurum and Kevlar! 2011 was the most un-windy year I've ever seen, and I'm glad you got enough breeze. Being on a street, or a corner, certainly helps.<br><br>How can it be that your note, dated 8/21/2012, just showed up on my comment list? Very strange.
I just realized after beginning to attach my blades to my pulley wheel that I used a 24-spoke wheel up there! Would a six-blade fan be sufficient or do I need to go wheel hunting again? <br>Thanks! ChristopherO
No, you're fine. Turning the drum requires such a small amount of wind-power, practically any blade shape will work well. Try placing one blade using just thumb pressure, making sure it gets along with the spokes and has a suitable angle, about 1-1/2&quot; out of the spoke plane. <br> <br>I just built a 24-spoke propeller with widened blades. I used my standard blade pattern to draw one side, then slid the pattern about an inch sideways and drew the other side. <br> <br>Make sure the blade's outer edge lies within the wheel rim. That helps keep blades from snagging during storage or shipping. The propeller in Step 7 looks great, but is also highly impractical.
Thanks, Larry! I will try all your suggestions.
I built this thing three years ago, and it's been mixed blessing on the Playa. Our main challenge is that the axle nuts tend to &quot;wind up&quot; and lock down on the axle, preventing the drum from turning - definitely a bummer! Looking for a solution to this challenge. Any suggestions?
It sounds like the axle bearings are adjusted too tight. The axles should rotate freely, with some &quot;play&quot;. In other words, rather sloppier than you would want a wheel on your bike to be. <br><br>Focusing on one wheel at a time, try putting wrenches on the axle nuts on both sides, and turn them counterclockwise a quarter-turn. If you're lucky, the cone nuts will turn with the lock nuts, and you've created some play. If you're not lucky, the cone nuts stay unmoving on the axle. Take the drum to a bike mechanic, who has cone wrenches, or invest in one yourself. (Cone wrenches look like very flat, thin open-end wrenches, and come in 4 widths.)<br><br>Try mounting the drum without using the &quot;extra&quot; axle nuts. The axle is (almost always) caged by the two metal angles, and can't fall out. The extra nuts were mostly to hold the wheels while you're building the drum.<br><br>
Thank you for displaying your evapotron at the Noobie Picnic. I am very excited about building this. jay jay@houseman.org www.houseman.org
Would it be easier to melt through the plastic with a piece of 1-3/8&quot; pipe to make the hole?<br />
Interesting!&nbsp;&nbsp;If you try it, please let me know how it works.&nbsp; I've settled on using the 1-3/8&quot; hole saw, applied delicately.<br />
The instructables membership pay-wall prevents me from accessing the full plans, despite the creative commons license of the plans / project specifying non-commercial use.<br /> <br /> So which is it? <br />
Please contact me:&nbsp; livember at earthlink dot net.<br />
<div id="main_content"> <div style="padding: 0.0px;z-index: 10;"> <div class="txt">&quot;Watch out for my favorite error: drilling a body hole through both top and bottom pieces of wood, rather than just the top piece. The bottom piece gets <strong>only</strong> a pilot hole.&quot;<br /> <br /> mine too. What I try do do now is clamp the&nbsp; pieces I want to join, drill the pilot hole through both, separate them and then drill the body hole on just the one.<br /> &nbsp;</div> </div> <table style="width: 1.0px;height: 1.0px;"> <tbody> <tr> <td>&nbsp;</td> <td>&nbsp;</td> </tr> </tbody> </table> </div>
This is a great job, I like it, but I don't totally understand the principle of gray water evaporation. Can you add an explanation about that?
One of the rules at Burning Man is, don't dump untreated graywater on the ground. Doing so leaves food particles, toothpaste, body paint, etcetera on the ground, messing up the "Leave No Trace" ethic we work so hard at. The ground itself is dried alkaline lake-bottom, and water turns it into sticky, slippery mud -- a nasty surprise for anyone who walks by before it dries up. So, what to do with graywater? Some people pack it out; a few pay the porta-potty contractor to take it away. Some people devise contraptions to evaporate it, and the Gray-B-Gon evapotron is one of the successful contraptions. For three reasons, it's a contraption that makes sense at Burning Man and almost nowhere else: 1. The humidity is extremely low, so evaporation is fairly rapid. 2. The rules, for good reason, prohibit dumping graywater. 3. We have lots of wind. The site is between two mountain ranges, so the prevailing wind is always up or down the valley, never across it. A propeller pointed in the right direction will always catch the wind, and it doesn't matter to the drum which way the propeller turns.
What a great project!&nbsp; Photo's and descriptions are great. You probably had a lot of fun doing this. I noticed above in the 3rd part you say &quot;A propeller pointed in the right direction will always catch the wind,&quot; I have been researching wind devices for a small wind powered water pump I am working on to build. One that comes to mind to possibly improve your design is a savonius wind turbine.<br /><a href="http://www.reuk.co.uk/Savonius-Wind-Turbines.htm">http://www.reuk.co.uk/Savonius-Wind-Turbines.htm</a><br />It does not matter which direction the wind comes from,it will always catch it, they are high torque and have a maximum built in&nbsp;speed. &nbsp;Keep up the good work!
Chrisnotap, the VAWTs (Vertical Axis Wind Turbines) has only a 50% m&aacute;x of efficience, because they can't use all profile. (pardon my Google Translator English) <br />
Thanks very much, Larry.
<strong>Very nice job making your blades. Do you have a template I can get for this pattern?</strong> I see the holes you made for securing the vanes to the wheel, obviously with the zip ties you mention. I may wish to use a 26 inch wheel and secure 4 cogs to catch another set on another shaft, to crank a small low powered 12 volt generator to trickle charge my scooter battery when needed.<br/>
The image in step 22 will help. Hand-sketch a shape you like, and cut it out. Variations in blade shape don't seem to affect performance much. The locations of the holes depend on the wheel's spoking -- you don't drill holes until you're confident you've found a good blade position. Steps 23 and 24 describe the constraints and the sequence of actions. About your generator idea -- the Gray-B-Gon runs on very low power, and my propeller design probably isn't up to driving a real load, like a generator. But, give it a try. There must be a description somewhere of what a high-performance propeller looks like. Note that commercial wind-powered generators have very few, very slim propeller blades.
<strong>Thanks for the recent update. My version of this as a wind generator is simply to drive a small dynomotor just like the small generators used for lights on bicycles, but at least cranking out one amp, at 12 volts. This would easily do that. This would allow me to trickle charge my battery while not driving the scooter, as it goes dead easily if I don't drive it everyday. Here in Missouri, it is not uncommon for straight line winds from storms to come through at 60 to 100 mph. Your typical wind generators can't continue to crank power in that stong of a wind. A friend of mine has a very large wind generator with a 3 ft. dia. concrete tower. With his brake set knowing a very storng storm was coming in, the wind snapped his tower. Based on past experience, my 68 inch wind generator using 12 blades made of six strips of fabric, ripstop nylon, survived that very same storm that destroyed his 40,000 dollar wind generator. I'm not cranking out 10 kW like he was, but it works in lower wind speeds his doesn't, and could handle higher winds easier. After he rebuilt it, he had his brake set just before another storm came in. He heard a loud shot, went outside to see what was going on, and he saw a power company truck driving off down the highway, alone. We have net metering here in MO, good luck collecting what you put back into the grid.</strong><br/>The meters clearly mark, plus or minus 20% accuracy... he eventually noticed that shot, took a large chunk out of one of his 3 blades. His brake has been set ever since.<br/><br/>I like the idea and how you presented this potential, as I may use it myself if I return to a rural lifesyle. Nice job you have done here.<strong></strong><br/>
Correction to step numbers: The helpful image is now in step 21. Steps 22 and 23 describe the constraints and the sequence of actions.
<strong>Thanks for the reply. I especially liked the pattern you used, but I plan to make it from stainless steel up to a 6 ft. dia. I'll have to design a strong hub for it, and I plan to build my own brushless AC generator. I mostly liked the appearance of your blades and wanted to scale them up for my project.</strong><br/><br/>I'm working on one now that has 12 blades of flashing secured to a hub and an outer ring that is 3 ft. dia. The last one I built stood up to 70 mph winds, but when the micro burst hit us at 100 mph wind, the blade assembly came off and I found it two blocks away, undamaged. Needless to say I secured it stronger after that. I liked another guys 3 bladed design, but he used pvc and I don't believe it will take the stresses of storms we get here in Missouri. I can see that small section with only two bolts snapping under stress. I would be hard pressed to be able to bend stronger metal brackets in a shape that would strengthen them along the vertical axis of the blade assembly.<strong></strong><br/>
Hi Larry! I heard you on the BMR last week talking about the Gray-B-Gon and I am hoping to build one of these fantastic contraptions for next year! Thanks for getting the word out there about your design! Where are your construction workshops held?
Glad you were listening! Keep an eye on the Jack Rabbit Speaks and other Burning Man news sources. Or just cut to the chase and invite me and your Burner friends to a Gray-B-Gon construction workshop in your driveway, back yard, garage, rec room, etc. Building one or more takes about four hours, and the parts cost is under $50 -- far less than if you bought the materials yourself in retail quantities. I bring the parts, you provide the space, builders provide bike wheels and pantyhose. A good thing to do early is to round up the bicycle wheels. A friendly bike shop will hold onto throwaway wheels for you, but it can take time before a trashed but salvageable wheel comes into their shop. See Instructable steps 3 and 4 for specs on the wheels. BM 2009 was hugely successful for Gray-B-Gons -- seven or more running in various camps, each consuming about 20 gallons/day rather than the 10 gallons I'd claimed, and getting lots of interest from passersby.
Test comment, to see if there's still a bug that keeps me from receiving email alerts when comments arrive.
What is tulle mesh?
Tulle is fine mesh of nylon or polyester, sold in fabric stores for $1.50 to $2.00 per yard. It's completely nonabsorbent, but when dipped in water holds onto a water film the same way window screen does. The nonabsorbency may contribute to a valuable property -- even with gunk in the water, and dust caking onto it, the mesh cleans itself every time it dips into the water in the tray. The gunk and dust eventually settle to the bottom of the tray. At the end of your stay, when you let the evapotron run dry and dismantle it for the trip home, just fold up the liner and put it in your trash. The pantyhose filter and the tulle mesh can either be trashed or taken home for a trip through the clothes washer. (Some vinegar added to the wash water will help.)
I don't get it, what's the wind power do?
The wind turns the propeller which rotates the mesh-covered drum through the water in the tray, and up into the air again, where the water filling the mesh can evaporate.
Since the propeller apparatus is fixed in place, when the winds shift, what is the effect? Do you rotate the entire unit, or did you find that unnecessary? We're very interested in adding this type of wind-driven movement to our existing pond to speed the process up from last year. Also, in light of 2008 dust storms, did you find any problems with sediment build-up? Last year we had plexi walls which helped, but we would lose those if we followed your plan.
Almost invariably, playa winds blow NE or SW -- down or up the valley between the Granite and Selenite ranges. The device works no matter which way the propeller spins. I've discovered that unlike all other evaporative techniques I've tried, the Gray-B-Gon is practically immune to playa dust. Rather than having water and dust dry in place, the drum rotating through the pond washes the mesh clean. The "pond" does receive playa dust, but the pond's relatively undisturbed so dust settles to the bottom. At the end of the week there's typically an eighth to a quarter of an inch of dried mud on the plastic liner.

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