What a Thorny Devil and Camel Nose Can Teach Us About Water
What a Thorny Devil and Camel Nose Can Teach Us About Water
Within our bodies and our societies we use water as a solvent, transporter, heat conductor, coolant, buffer, lubricant and structural component. Adapting to a new conservation-based prosperity will mean figuring out ways to make water work more efficiently.
Adapting is something that nature does very well, and because organisms have occurred in water for billions of years, there are many examples of clever tactics. Here are some:
Doing without: When it comes to cost cutting, the most effective way to save material is to not use it at all. Tardigrades, or water bears, are the supreme champions at doing without. These common, 1-milimeter long invertebrates have developed a way to survive virtually without water by a process called cryptobiosis.
In one type, the water content of their bodies decreases to less than 1 percent and their metabolism rate becomes undetectable. They are thus able to withstand extreme cold, heat and radiation and still survive for a decade or more in this suspended state.
One reason is that they possess a special type of sugar, trehalose, within their cells that, instead of crystallizing during desiccation, becomes a gel. This gel keeps the cell walls and organelles from being damaged until water returns. Researchers in the field of cryobiology are now investigating this ability in order to preserve medical vaccines, food, sperm, blood or even organisms.
Collecting: There seem to be as many ways of collecting water in nature as there are organisms on the planet. As water becomes scarcer we may want to learn some of these micro-harvesting techniques. The marsh crab (right) is a crustacean with very hairy legs that serve a purpose. The tiny setae are hydrophilic and therefore suck water out of the interstices of the mud that the crab lives in so the animal can drink it.
The Namibian Desert beetle captures fog by collecting it on hydrophilic bumps and then running it down hydrophobic channels to its waiting mouth. The Thorny Devil of Australia (above) captures dew in a similar fashion but with the tips of its protective scales, grooved to run the liquid to the right place.
Storing: Smarter water systems may require more adaptive storage methods and nature has some lessons to impart. The barrel cactus for instance, uses a pleated design to expand and contract as conditions dictate. The Baobab tree, the world's largest succulent at over 20 meters, is a prodigious collector of water, up to 120,000 liters in some cases, in thin-walled cells within its soft, pithy interior. This plant also expands and contracts with the amount of water available.
Both of these plants also exhibit a common trait in the natural world, multi-tasking. Most plants use water for structural integrity as well as other benefits. “Hydraulic architecture” seems, for now, to be a term limited to botanical parts and diversion ditches, but water has also been used as a structural component in some cofferdams. It possesses qualities of thermal capacity, mass and pressure that could be simultaneously capitalized on.
Transporting: The circulatory systems in plants and animals are wonders of engineering, as is the exchange of water through your skin to cool you through evaporation. Interestingly enough, your sweat ducts are not straight, but helically shaped tubes. One sees the spiral in fluids at all scales, from the drain in your bathtub to spiral nebulae, and this is what inspired Jay Harman to invent his line of highly efficient fluid mixers. Harman is the founder of Pax Scientific, a maker of fans, propellers and impellers, all based on the spiral geometry that he observed in nature.
Reacting: Substituting information for energy or material is a common survival strategy in nature. The tactic of “just-in-time information” is the refinement that makes this work, particularly in the cellular to organism scales.
As just-in-time delivery of parts reduces the need for warehousing in the manufacturing world, just-in-time information, (coupled with on-site manufacture) reduces the need for energy in nature. Your body, for instance, doesn't transmit the information to your brain that you are thirsty until the chemical balance in your fluid systems triggers this response.
Agricultural systems that employ grids of buried sensors operate on a similar principle. Researchers at Iowa State University have developed a grid that can register temperature and moisture content precisely and then beam the information via low-frequency radio waves to a central controller. In future operations, GPS-controlled machinery or a framework of pipes will then be able to deliver water and nutrients to the areas in need when they need it. Coupled with a solar-powered satellite weather station, this type of feedback system will save water, expensive and potentially polluting fertilizer, and money.
Reducing: Plants don't get around much and therefore have countless ways of reducing the need for water. Waxy coatings; minute, insulating or water-trapping hairs; reflective colors; folding leaves; and time-managed openings and closings are some of the clever ways plants reduce their water needs and loses.
These techniques include how a plant makes its sugars in photosynthesis. Corn and sorghum plants, in their adaptation to hot and dry climates, are able to photosynthesize using less CO2 than other grains like rice and wheat. Less CO2 needed means that the plant's leaf stomata are open less often and therefore losing less water.
Researchers at the International Rice Research Institute in Manila, the Philippines, are investigating which genes create this advantageous leaf structure to create a larger rice grain with less water, research that could have a global effect since approximately half the world depends on rice for food.
Reusing and recycling: Your body is a wonderful example of how reuse saves you water everyday. Your blood plasma, for instance, is squeezed out of capillaries constantly and this leaks into the interstitial fluid flowing around your tissues. Some of this flows into your lymph system and gets put to work transporting antibodies around. After flowing through the lymphatic system, lymph flows back into the blood stream to be used as plasma again. If it were not for mechanisms like this in your body you would need about 100 times more water a day (about 50 gallons) than you do now.
Singapore and Orange County, Calif., lead the world in municipal water recovery systems development. Singapore gets its water from four sources, including rainwater catchment, recycled water and desalination. Recycled wastewater, branded under the name NEWater, now supplies approximately 15 percent of the country's needs.
Orange County has a similar system for triple-treating its used water with microfilters, reverse osmosis, and ultraviolet radiation before it is injected back into an underground aquifer.
Individual building greywater systems will become more and more common as communities strive to husband their resources. The California Building Standards Commission relaxed the rules for direct application of laundry water to landscaping in August 2009, acquiescing to what had become common practice in many rationed communities. Arizona, Texas, and New Mexico had already done so years earlier. In June 2010, all new commercial construction in Tucson, Ariz., will need to have greywater system capabilities.
Cooling and heating: Water in its liquid state is a good conductor of heat, and in its gaseous state, as water vapor, more of it can be contained in hot air than cool. Both camels and elephant seals have refined water and heat exchange systems in their noses. So-called turbinate structures of spongy nasal bone are covered in mucous and will hydrate the air coming into the animal, and dehydrate the air being exhaled. In this way, the animal is able to save as much as 60 percent of its water.
That process is an elegant example of a simple structure responding to different conditions strictly because of physical properties. In the camel's case, whenever the air passing over the plates is hotter, the plates will take some of its moisture; whenever the air is cooler, the plates will give up some moisture. This seems like a phenomenon begging for an application from some eager beaver at MIT.
Filtering: Filtering is a fact of life for almost every organism on the planet at all scales. Wise water use will continue to demand filtering, and doing so in smarter ways will help save resources. Your kidneys are a marvel of efficiency, but so are intertidal plants like salt meadow grass and mangroves. Our world will need more water than current freshwater supplies can sustain and therefore, in many areas, we will have to turn to the sea. Mangroves have a unique ability to filter the salt out of seawater, as do seabirds, which use their nasal glands to excrete the brine.
Mangroves can either exclude the salt entirely at their root surfaces through a type of reverse osmosis, or excrete the mineral through leaf pores and lenticels; all species do both to varying degrees. Desalination plants, like Singapore's, also use reverse osmosis. They are not new, but they are not widespread either because of cheaper competition. This may change as groundwater becomes more polluted with agricultural runoff and traditional supplies become scarcer.
A typical reverse osmosis system pretreats seawater or brackish water to remove debris and large particles and then runs it, under pressure, through a membrane into a lower pressure tank. The brine that cannot go through the membrane is periodically siphoned off. The membrane can typically remove 98 percent of the dissolved salts from the water and the harvested liquid is adjusted for pH and aerated before storage.
These systems could be improved, although they have many advantages for coastal areas. The chief shortcomings are membranes that require constant monitoring and frequent replacement, and the cost of energy to create the pressure in the feedwater. It's possible that the mangrove has lessons about durable membranes, and no-energy pumps that we could use. Certainly the approach would be different: a passive negative pressure system would be slower and require more surface area, but something powered by evaporation, rather than transpiration, could add a final distillation step to the purification process while reducing energy costs.
An evaporative desalination system is being tested in three African coastal locations by Charlie Paton of the Seawater Greenhouse project. Water is pumped to a two chamber greenhouse where it is first run down a trickle wall to evaporate and the resultant water vapor is then condensed and collected into a storage tank. It is an elegantly simple and seemingly effective system. Combining it with a reduced energy water delivery system, inspired by the mangrove, might make it even better.
The issue of water and how best to use it touches every aspect of our lives. As varied as the challenges are, many of them have already been faced by the other organisms on the earth and many of their solutions are worth studying.
Tom McKeag teaches bio-inspired design at the California College of the Arts and University of California, Berkeley. He is the founder and president of BioDreamMachine, a nonprofit educational institute that brings bio-inspired design and science education to K12 schools.