How to Recycle Water in Ecosystems

In natural ecosystems, vital materials such as carbon, nitrogen and water are continually recycled to maintain their flow and balance within the ecosystem. In the case of water, the hydrological cycle, a continually repeating process of evaporation and condensation, regulates many natural processes and ensures that the resource is constantly recycled and available. As fresh, drinkable water becomes an increasingly scarce resource, a close examination of the way nature recycles water can yield significant insights into ways in which we can recycle and better use water, imitating the natural processes of the water cycle.

Things You'll Need

• 5-gallon bucket
• Gravel
• Sand
• Knife
• Round 5-gallon plastic container
• 1-gallon container
• Plastic wrap
• Tape
• Glue
• Rock

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Instructions

Sand Filtration

• 1

  Make holes in the bottom of a 5-gallon bucket. Using the knife, make small holes in the bottom so water can filter through the bottom. You are designing a sand filter, a simple device based on the natural process by which ecosystems filter and recycle rainwater. When precipitation falls on the ground to begin the water cycle, it either runs off on the surface until reaching a body of water or slowly filters into the ground until reaching groundwater systems. During that slow process of moving through the earth, the earth itself, through multiple layers of sand and stone, acts as a filter that gradually removes impurities from rainwater, thus explaining the purity of most underground water deposits.

• 2

  Fill the bottom of the bucket with a layer several inches thick of gravel. This layer will allow water to pass through the final stage of filtration and out of the holes at the base of the bucket.

• 3

  Fill the rest of the bucket with sand, leaving only about 6 inches of space between the edge of the sand layer and the rim of the bucket. This sand layer will be the main filtration agent in the sand filter.

• 4

  Allow the contents of the filter to settle. Shake the bucket slightly and pour small amounts of water through the system.

• 5

  Pour water over the sand until you have filled the rest of the bucket. Water will slowly filter through the sand and gravel until it pours out of the base of the bucket. This technique is useful when recycling gray water (nonseptic household waste water).

Evaporation and Condensation

• 6

  Glue the 1-gallon container to the bottom of the inside of the larger 5-gallon container. You are securing the small container inside the large container so some room is left around the small container and the walls of the larger container. Be sure the large container is taller than the small container so the 1-gallon container fits entirely inside the larger container; use nontoxic glue and allow the glue to dry before beginning.

  Just as the water cycle relies on the evaporation of surface water (often fed by groundwater) to create new pure water, this simple evaporation purification method uses sunlight to filter water. Natural ecosystems need a regular supply of pure water to dissolve nutrients and initiate chemical and physical processes. Surface water that has already dissolved mineral compounds is subject to evaporation, which turns the water into a gas and causes it to rise into the atmosphere, leaving the dissolved minerals behind. When the water condenses at altitude and falls again as precipitation, it falls as pure water and reinitiates the process. Similarly, you can use a simple controlled evaporation tank to purify water, recreating the natural water cycle on a small scale.

• 7

  Fill the area between the walls of the small container and the large container with water. The small container should remain empty.

• 8

  Cover the top of the large container with plastic wrap and seal the wrap with tape.

• 9

  Place a rock or small weight over the center of the plastic wrap on the outside, weighing down the system so the plastic wrap sags toward the center of the small container.

• 10

  Place the system in the sun. Gradually, water from the large container will evaporate, condense on the plastic wrap, drip down the incline created in the wrap by the rock and fall into the small container. The water in the small container has been filtered and recycled by evaporation.