How Does Soil Filter Water

How Dirt Cleans Water

A purified project from Science Buddies

Cardinal concepts
Filtration
Aquifers
Permeable and impermeable soil
Groundwater

Introduction
Have y'all ever noticed the claim on a bottle of water that information technology contains "spring water"? More than half of the bottled h2o sold in the U.Southward. is labeled this way, only only a fraction of this water really flowed naturally from a bound. Almost is from groundwater that is sucked up by pumps (which are installed well-nigh a bound). In 2014 this was well-nigh 22.7 billion liters of h2o. That is a lot of water! You might wonder how water is stored undercover—and what replenishes these reservoirs. In this action you will create a model, fill up iii reservoirs and evaluate how clean the water in these reservoirs becomes. Will your "groundwater" be as tasty as jump water? Effort this activeness to find out!

Groundwork
Imagine a rainstorm has just come through; some h2o runs down the pavement and into a patch of grass where some of it soaks into the ground. Where does that water become? When h2o soaks—or infiltrates—into a permeable soil, it makes its way through the spaces betwixt the particles in the soil. Soil with larger particles has larger holes, resulting in fast-draining water. Soil with small particles drains water more than slowly. Some soils, such equally clay, go far very hard for h2o to seep through and are almost impermeable. Ground such as granite is impermeable. Water flows over the particles into cracks but cannot get through the particles.

Every bit water seeps deeper into the ground, it will eventually attain an impermeable layer and either collect or flow sideways. This creates secret layers of permeable soil that are saturated with water. Saturated ground has all its holes or pores filled with water. These layers are called aquifers, and they can be pocket-sized or massive. The largest aquifer in North America (the Ogallala) runs from Southward Dakota all the way s to Texas.

Unlike surface water nerveless in rivers and lakes, groundwater is oft clean and ready to potable. This is because the soil actually filters the water. The soil can hold onto pollutants—such as living organisms, harmful chemicals and minerals—and only permit the clean water through.

Materials

About 500 milliliters (i pint) of water
Pot that tin agree a little more than than 500 milliliters
Red nutrient coloring, preferably liquid (Red, flavored-potable pulverisation also tin can exist used.)
Cacao pulverisation (one tablespoon)
Fibroid ground black pepper (one half tablespoon)
Spoon
Three empty 500-milliliter disposable water bottles with lids
Scissors
Popping corn kernels (unpopped)
Cornmeal
Cornstarch
Three tall spectacles (Preferably they should exist spectacles with a rather narrow opening so that an upside-down water bottle tin can rest in each glass'due south opening.)
One-quarter cup measuring loving cup
Workspace that tin tolerate some liquid splashes
An adult helper

Preparation

Pour almost 500 milliliters of water into a pot. Add two drops of red food coloring or some of the crimson, flavored-drink pulverisation, i tablespoon of cacao powder and half a tablespoon of fibroid footing black pepper. Mix well. This will serve as your "dirty" h2o.
To create your 3 soil containers, have an adult carefully assistance you cut off and discard the bottoms of three empty h2o bottles. Plow the tops upside down so they expect similar elongated funnels. Leave the canteen caps on and let the funnels rest in the glass openings.
Fill the funnel part of each soil container with popping corn kernels. The kernels represent pebbles in nature.
Add together a ii.5-centimeter (ane-inch) layer of cornmeal on pinnacle of the layer of popping corn in one soil container, which represents fibroid sand in nature.
Add a two.five-centimeter layer of cornstarch on acme of the layer of popping corn in the 2d soil container, which represents claylike soil in nature.
Add a 2.v-centimeter layer of popping corn to the third container. All 3 containers should now have the same level of "soil". Which "soil" do you expect volition allow the h2o to seep through fastest?

Process

Stir your muddy water well.

Showtime, wet the surface of the soils by pouring iv tablespoons of dirty h2o over the soil in each of the three containers. Look at the side of the soil containers. Tin can yous see how high this h2o reaches? Is it the same for all three containers?

Scoop out ane-quarter loving cup of dingy water and pour information technology over the soil in i container. Lookout what happens. Does water collect at the bottom of the funnel? Does it run fast or slowly through this soil?
Repeat the previous pace for the 2nd soil container and then for the 3rd one. Remember you predicted which "soil" would let water to seep through fastest. Was your prediction correct? Why practice you call back this soil drains water fastest?
The water will collect at the bottom of the funnel, where it is stopped past the canteen cap (an impermeable layer). This is similar an aquifer, an underground layer of soil saturated with water. Soil in which all the holes between particles are filled with h2o is chosen saturated. Compare how fast the aquifer grows in the three containers.
While you expect for the water to seep through the "soil," reflect on the following questions: Which of the three "soil" types has bigger holes between the particles, the corn kernels (pebbles), the cornmeal (sand) or the cornstarch (clay)? Could that explain why some "soils" allow water to seep through more quickly than others?
Yous poured the aforementioned corporeality of water on the three soil containers. Practise you think that if yous await long enough, the iii aquifers will somewhen hold the aforementioned corporeality of water or will ane concord more than than some other? Why practice you lot recollect this is the example?
In a moment you will (or a helper an adult to) unscrew the bottles and collect the water gathered in the aquifer in the glasses. What practise you look the dirty water to be like subsequently it runs through each type of "soil"? Would whatever pollutants get stuck in the dirt and thus be filtered out? Would the different "soils" have different abilities in filtering your muddied water?
Now, unscrew (or enquire an adult helper to unscrew) the bottle cap at the bottom of the corn kernel just soil container. Pay attention; your aquifer volition instantly deplete. Inquire the developed to collect as much of the water as possible in the tall glass on which the container was resting. When done, replace the unscrewed container on the alpine glass so more water tin can baste out. Note some corn kernels might drip out; this is fine.
Now repeat (or ask an adult helper to echo) the previous stride for the other two containers.
Examine the water that ran through the "soils." Did running the muddy water through "soil" remove the red food coloring?
Sense of taste the original dirty water and the post-filtered water. Does it gustatory modality dissimilar? Did any of the "soil" filters remove the cacao powder?
Await carefully at the lesser of the glasses for signs of blackness pepper. Did whatsoever of the "soil" filters remove the black pepper?

Extra: Let your bottles drain over a longer menstruation of fourth dimension. Did more than water bleed through one "soil" blazon compared with another? Would this imply that some types of soils retain more water than others?
Extra: Try a thicker layer of soil. Would a thicker layer of soil be able to filter out more pollutants?
Extra: Echo the activity with gravel, sand and clay. Wash the gravel before you start, but definitively do not taste the h2o collected in the glasses!

Observations and results
Did y'all notice how the aquifer in the container with only corn kernels (pebbles) filled almost instantly whereas the 1 with a layer of cornmeal (sand) filled slower and the ane with a layer of cornstarch (clay) took a long fourth dimension?

This is to be expected. The larger holes between the kernels (or pebbles) let h2o to seep through quickly—the water drains fast. Cornmeal has smaller particles, just like sand. These particles pack close together and get out lilliputian holes in between. The water can however seep through but takes a little longer. Cornstarch is similar to dirt. It consists of very small-scale particles packed closely together. The water has a very hard fourth dimension getting through this material.

Did you too notice the kernels merely filtered out black pepper whereas the cornmeal filtered out virtually of the cacao pulverisation and a little scrap of the food coloring, also? If you were patient, you could run across that the cornstarch filtered out all the cacao ability and more than food coloring. This is similar to what happens when dirty rainwater seeps through the soil and gathers in an aquifer. The soil filters the dirty water. Contaminants go stuck in the soil, and make clean water reaches the aquifer.

Although groundwater is commonly make clean, soils are non perfect filters. Some contaminants still make their manner through the soil and contaminate the groundwater. This is a serious problem; once polluted, it is difficult to clean an aquifer.

Cleanup
The content of the soil containers can go into the composting bin. The plastic bottles can be recycled.

More than to explore
Capable Carbon Filter, from Scientific American
Aquifer, from National Geographic Society
Pollution of Ground Water, from Water Encyclopedia

This activity brought to you in partnership with Scientific discipline Buddies

Science Buddies

ABOUT THE Writer(S)