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.
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
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.