Evaporation Ponds
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Grey water (any waste water) from dishes, showers, etc. shouldn't be dumped on the playa surface. Evaporation ponds are the best way to dispose of gray water. They're simple and cheap to build.
Contents |
[edit] Building a Basic Evaporation Pond
Materials
- Four 8 foot long 2x3's (or similar).
- Heavy black plastic, preferably 6mil or thicker, and at least 10'x10'. It needs to be strong enough to resist punctures and tears.
Both the lumber and the plastic will get very nasty by the end of the event. The lumber may need disposing, but the plastic is incredibly durable. It can withstand laying it out on the sidewalk or street when you get home. Then run a trickling hose on it as you wipe it down with sponges or towels. The tarp can last you at least three times on the Playa.
Construction
- Lay out the black plastic on the ground where you plan to build your evaporation pond. Be sure the sheets are at least 10'x10' so the edges extend well beyond the end of your 2x3's'. To be safe, lay down two sheets to be sure the nasty gray water doesn't leak out onto the playa.
- Use the 2x3's to build a square frame centered on top of the black plastic sheet(s).
- Fold the edges of the black plastic up the outside of the square, and staple to the top. Cut off the excess, or fold it up and staple it to the top or side. There's a reason for putting the wood frame on top of the plastic, and wrapping the plastic edges up around the outside. This creates a very flat surface inside. If the black plastic were placed on top of the frame and stapled down, it tends to bow into the center, creating a small puddle. The object of the evaporator is to maximize the surface are of the pond, maximizing evaporation.
[edit] Keep Away the Stink: Add a Strainer
Evaporation ponds tend to collect lots of nasty bits of food and such from washing dishes. This slows the evaporation, tends to produce odor, and gets gross. An easy solution is to build a strainer for waste water poured into the pond. The strainer will catch large particles, which will then quickly dry out in the air and sun. A strainer can be made out of just about anything:
- Punch small holes into the bottom of a water jug
- Mount some window screen over a small frame
- Stretch some nylons over a wide piece of PVC pipe or duct
[edit] Evaporate Faster
There are several methods of increasing the effeciency of an evaporation pond. However, they can also take a good deal more work:
Fountains
Create a fountain, which will increase your gray water's contact with the air, and thus increase the evaporation rate:
Wicks
Hang lightweight fabric wicks into your pond. Use light fabrics such as old t-shirts. Heavier fabrics don't work as well. If you use cotton, you'll be able to burn the wicks.
[edit] Dealing with Leaks
It's very possible to develop leaks in your pond liner. Be safe by using a couple of layers of black plastic. However, if leaks to develop:
- If you have water in your pond, place something very heavy and flat over the puncture. This will at least reduce the leak rate.
- If your pond is dry, clean the area around the leak and patch the hole:
- Duct tape will do in a dire emergency. However, it doesn't do super well underwater and will eventually separate.
- If you can get some good waterproof glue such as Gorilla Glue, hot glue, or rubber cement, glue down a patch. Be sure not to add water until the glue cures.
- If it is a tiny puncture, a bike tube patch may work. (This is just a suggestion - it's untested.)
[edit] Capacity
Theoretical capacity for an 8'x8' evaporation pond is 15 gallons a day[1]. This comes out to about 1 gallon for every 4 square feet. Plan on needing about one gallon of capacity per person per day.
However, that is the theoretical capacity. A great many things will reduce the evaporation rate and leave you with a full pond at the end of the event. Capacity can be dramatically reduced by a number of factors:
- Excess shade falling on the pond. This can come from excessively tall sides, nearby structures, a shower platform built over a corner, or even a full shower stall.
- It gets too deep. Anything more than an inch deep won't heat up enough and will evaporate less water.
- It fills up with dust. You will get playa dust in the water, even if there's never a major windstorm.
- It fills with food waste. Filter your dish water before you pour it in (see below.)
- Or basically, anything that covers the black bottom, However, this can be remedied by adding a layer of black plastic into the pond when necessary.
- The bottom is uneven, creating a series of puddles rather than a single flat surface.
- Oil or grease in the pond (from food waste) will collect on the surface and prevent evaporation.
[edit] Placement & Safety
Evaporation ponds get gross and a little smelly. Nobody wants them near their tent. Since they're dark and low, they can also create a nighttime hazard, so keeping them away from high traffic areas is a good idea.
[edit] What Not to Do
- Don't fill your evaporation pond too deeply. The water will not evaporate in time, and the weight of the water is more likely to puncture your liner. If you find you have more than a couple of inches of water, try and find the supplies to build a larger evaporation pond.
- Don't use a kiddie pool for an evaporation pond. It's too easy to fill deeply, and the high sides shade too much of the water surface, and reduce airflow over the surface.
- Stop adding to your evaporation pond 24 hours before you leave. This will give it time to dry out.
[edit] Showers
Showers are commonly mounted on the corner of an evaporation pond. Often, it's just a platform made from a few pieces of wood placed over a corner of the pond frame. The one thing to be careful of is that a large shower platform and/or privacy screen can shade the pond throughout much of the day.
[edit] Cleanup
Evaporation ponds don't always dry up by the time they need to be packed up. Stop adding water to it 24 hours before you leave. Scooping up the water is slow and nasty, but must be done if there's any left. It's a good idea to keep your empty water jugs in good shape and with lids, so you can scoop waste water into them. It's also a good idea to have some heavy duty contractor bags on hand, into which you can stuff the still wet black plastic. You don't want that to leak onto your back seat.
