Since 2009 the online Gray-B-Gon construction guide has helped people build over seventy evapotrons, in both home shops and public workshops. Below is the introductory section. You can view the entire document at http://www.instructables.com/id/Gray-B-Gon-wind-powered-evapotron-for-graywater-di/ . You can download the pdf from there, if you're a paying member of Instructables; or you can download it from the Documents page of this website.
Gray-B-Gon Construction Guide
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 the two performance killers of passive evapotrons: loss of wick absorbency, and loss of heat-absorbing black surfaces due to accumulated playa dust.
As well as useful, 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 seen it turn, 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 and a new plastic liner and towel, 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 30 discusses periodic disinfection with chlorine bleach. The subassemblies you take home are unsanitary too; but so is a handshake, or sharing eating utensils. If 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 $180.
Alternatively, join a one-day construction workshop, where we provide most of the parts at cost (around $60 including wheels) and the wood parts are precut. The construction time is about six hours, less if you have friends helping.