Filtering water and slowing water flow using different materials

Filtering dirty water and slowing water flow using different materials to help prevent floods and help filter water
Maxwell Van Vliet
Grade 5


Testable Question

What materials are best for filtering dirty water and slowing water flow?


I think the best combination of materials for filtering is going to be the test with the three layers of:

  • Sand
  • Gravel
  • Grass/Burlap

I think the best combination of materials for slowing the flow will be the test with the two layers and the add on wetland:

  • Sand
  • Gravel
  • plus the Sponge (wetland peat).



  • Trap and filter sediment (bits of dirt) that are washed off the land
  • Plants in a wetland slow down water flow and let sediment settle out
  • Slow down water flow
  • In heavy rain can prevent flooding
  • In times of drought can be a water source
  • May recharge underground water
  • Microorganisms break down chemicals or other things in the water
  • Plants in the wetland may suck up extra nutrients like nitrogen and phosphorus.
  • Some wetlands are naturally occurring
  • Some communities in Alberta have made wetlands to treat wastewater
  • Wetlands store water and slowly let it out 
  • Wetlands spread water out over big areas of land
  • The vegetation in a wetland acts like a sponge make more space for overflow 


  • Different media may be better at filtering different particles
  • Stacking filter media may be better
  • Activated carbon can remove really small things like food colouring

Erosion Fabric

  • People use types of fabrics erosion control fabric when they finish a construction site to prevent erosion.
  • Some types of erosion fabric has grass seeds in it so grass can grow, that type for erosion control fabric holds moisture so it helps the grass grow.
  • Some types of erosion fabrics are designed to decompose so that it does not affect the environment. 




Controlled Variables

  • Container holder filter media is the same size
  • Dirty water mix
  • Amount of dirty water poured into the top of the container
  • Pour rate approximately the same
  • Design of the sponge (wetland peat) section
  • Set of the base
  • Pairs of tests have same amounts of media
  • Type of sponge
  • Amount grass seed
  • Size of grass seed area

Manipulated Variables

  • Wetland peat (sponge) present (Group A only)
  • Filter media (materials) type and order (All)


Responding Variables

  • Water flow rate leaving the sponge (Group A only - wetland peat)
  • Water quality leaving the sponge (Group A only - wetland peat)
  • Water flow rate leaving the filter (Group B)
  • Water quality leaving the filter (Group B)


Materials List

Main Filter/Set Up

  • Sand
  • Gravel
  • Grass, dirt and burlap (see below for “grow the grass”)
  • Pop bottles (2L)
  • Scissors to cut the bottles
  • Wood, screws, drill and drill bits to build frame
  • Wax paper to send water into mason jars
  • 1L Mason jars to catch the runoff for each experiment
  • Sharpie and label maker to label the set up and mason jars
  • Paint swatches for comparing water before and after

Sponge (wetland peat) Filter

  • Small pop bottles (300mL)
  • Person made sponge
  • Paperclips
  • Tacks
  • Scissors to cut the bottles and sponge

Growing Grass

  • Four lasagna pans (ten inches by four inches)
  • Water
  • Spray bottle
  • Wax paper 
  • Dirt 2c per container (2 containers)
  • Mesh
  • Burlap 3 layers per container each piece cut into 10” x 4” (2 containers)
  • ¼ c grass seed per container (4 containers)

Dirty Water

  • Water
  • Dirt
  • Coffee grounds
  • Blue Food Colouring
  • Large metal bowl
  • Measuring cup and spoon

During the Experiment

  • Measuring cup
  • Stop watch
  • Mason jars to catch the “clean water”
  • Pencil and paper to record data and observations


  • Clay to stop bottles from wiggling/moving
  • Measuring cups
  • Scissors
  • Tables and stools to hold set up
  • Plastic cloth to protect floor


Building the set up

  1. Empty ten 2-liter pop bottles.
  2. Empty five 750-ml pop bottles
  3. Parents use an exacto knife to cut part of the 2-liter pop bottle off. Lay the bottle horizontally and cut the top half off but leave the spout intact.
  4. Parents use exacto knife to cut the bottom 3 inches off the five 750-mL bottles.
  5. Collect ten containers to catch the water from each of the ten set ups.
  6. Build a wooden support for each of the eight set ups so that the back end of the 1 L bottle laying horizontally is 1.5 inches above the ground (parent assisted).
  7. Put the 2-liter pop bottles in their supports with the spout of each bottle in the hole.
  8. Place a small piece of wax paper under each spout to direct water into the jar/wetland
  9. Trace the circumference of the smaller pop bottle on a sponge. Note the sponge needs to be bigger than the bottle
  10. Cut the sponge to make a sponge circle for each of the four smaller bottles – two layers of sponge per bottle.
  11. Put the sponges in the bottles.
  12. Punch two holes with hole punch in opposite sides of the five smaller bottles at the open end. This will be used to hang the smaller bottles upside down under the spout of four of the large bottles.
  13. Use two large paperclips to hang the five smaller bottles onto the box support. Secure with tacks.
  14. Place a 2L mason jar under each set up labelled with the set up number. Mark each mason jar with 0.5c, 1c, 1.5c and 2c.

Planting the grass

  1. Lay out 4 lasagna pans
  2. Cut burlap 6 times to the size of 2 lasagna pans
  3. Filled a spray bottle with room temperature water
  4. Get grass seed
  5. Put one layer of burlap in the bottom of two lasagna pans
  6. Sprinkled ¼ cup of grass seed on top of the one layer of burlap for both lasagna pans
  7. Put two more layers of burlap on the lasagna pans
  8. Repeat for two pans with soil
  9. Spray until moist   
  10. Put under grow light with clear plastic lid. Spray with water every two days and monitor grass growth
  11. Grow grass seed for 2.5 weeks

Layering the filter media

  1. Add 2c water to 6c dry sand, mix. Repeat to make 16c of wet sand. Layer 2c wet sand in bottom of each of the horizontal bottles (except the controls).
  2. Layer the filter media in order as described in the table.
  3. Transfer the seeded soil/burlap to the appropriate bottle
  4. Amounts for each test bottle are:
    • Wet Sand: 2c
    • Gravel: 1.25c
Test Filter Media

Making the dirty water

  1. Get a very large metal mixing bowl
  2. Fill bowl with 20 c clean tap water
  3. Get ½ c measuring cup
  4. Measure out ½ c coffee grinds (dry) and dump in bowl
  5. Measure out ½ c dirt (moist) and dump in bowl
  6. Add 10 drops of blue food colouring
  7. Mix well – check for lumps and squish out
  8. Take photo of dirty water and compare to paint swatches for “before colour”

Running the Test

  1. Prepare dirty water (see above)
  2. Pre-moisten each of the tests using ½ c of clean water – add very slowly over the large rocks so that erosion does not occur. This represents recently melted snow / spring wet conditions. Do this before adding the grass.
  3. Each test will have 2c of dirty water run through it starting at the upper end poured at a steady rate onto the big rocks.
  4. Start timer and pour the 2c of dirty onto the rocks over 15s so the water rate controlled so it is the same for each set up.
  5. Measure and record how long it takes for the water to fill the mason jar at each line (0.25c, 0.5c, 0.75c and final volume/time). There may not be full water recovery.
  6. Look at the colour and what is in the water for each mason jar. Record observations of water colour and content. Compare to paint swatches and match if possible.
  7. Record observations of what the filter media looks like as well as what the wetland sponge looks like



Observations and Raw Data


Dirty Water (Before Test)

  • The dirty water looks very brown and smells like coffee
  • You can see a light bit of blue/green in the water
  • It has lots of small bits in it

Test Observations

Note - a lot of photos and videos were taken during this experiment. 

Observation Summary Table

Raw Data

Time in seconds was recorded for different water amounts to flow through each set up and into the mason jar at the bottom.

Raw Data Summary Table




Data Analysis

Speed of Water Flow

  • Each test was run three times.
  • Times and volumes recorded for each test were averaged (Table 1).
  • This was put on a graph to compare (Graph 1).

From this graph, the test set ups were put in order from fastest water flow to slowest water flow:

  • 1B (sand)
  • 2B (gravel)
  • 5B (Control no media)
  • 3B (burlap/grass)
  • 4B (soil/grass)
  • 2A (gravel + wetland)
  • 1A (sand + wetland)
  • 3A (burlap/grass + wetland)
  • 5A (Control no filter + wetland)
  • 4A (soil/grass + wetland)
Table 1: Water Speed 
Graph 1: Water Speed Graph


As the three tests were run for each set up observations were made about the water that came out into the mason jars. These observations have been summarized and used to rank the set ups by how well they filter. The number 1 is the best with 6 being the worst. Some tied.

Table 2: Filter Ranking Table




Summary and Conclusions


Water Speed

For the tests with filter media only (1B/2B/3B/4B) (no wetland/peat sponge):

  • Out of all the media soil/grass (4B) had the slowest water flow followed by burlap/soil (3B).
  • Out of all the media sand with no wetland (1B) had the fastest water flow followed by the gravel with no wetland (2B).

Wetland Add On (1A/2A/3A/4A):

  • Wetland add on slowed water for all tests compared to the ones without wetland.

Water Filter

For the tests with filter media only (1B/2B/3B/4B) (no wetland/peat sponge):

  • Out of all the media the burlap/grass filter media (3B) removed the highest amount of particles.

Wetland Add On 1A/2A/3A/4A:

  • All tests with the wetland add on filtered the water better than all the tests without the wetland add on.
  • Out of the wetland tests soil/grass (4A) and burlap/Grass (3A) filtered the water the best.


  1. To slow water flow a site should have either soil or fabric and grass on top of the base material. To slow water flow even more run the water through a wetland.
  2. The best material to filter water at a site is fabric with grass on top of the base material. To filter water even more run the water through a wetland.




This project showed how amazing wetlands are. They slow water flow which help prevent flooding and they filter water! We should make sure to preserve wetlands. I would like to learn more about how human made wetlands can be designed to filter specific things. Specifically I am interested in how different plants can remove particular contaminants.

Filter Material

I also learned how important it is not to leave a construction site bare with sand or even just sand and gravel. This would cause runoff and erosion. The soil had the best seed growth but the fabric really worked well to prevent erosion. I would like to learn more about fabrics and geotextiles that can be used during construction to prevent erosion.

Sources Of Error

Sources of Error

  • Grass did not grow well on straight burlap – likely should have put some soil under the burlap
  • Inconsistent growth in the grass in the soil
  • Probably should have started the grass earlier
  • Each of the 1L bottles laying in its side pools water slightly
  • Tried using the funnel to control the release of flow but was too fast. Decided to use an amount of water poured over a certain amount of time instead
  • Needed to keep dirty water stirring until pour so particles didn’t settle out
  • Steepness of the 2L bottle angle affects the flow but I didn’t test this. They were all at the same height.
  • As the set ups had tests repeated the water saturated the soil and the sediment built up



Thank you to:

  • My parents for helping me build the set up, run the experiment and for helping with the technology to put this project on-line. That was hard!
  • Thank you to my teachers Sra. Styles and Srta. Rivas for their encouragement and for helping me with the CYSF requirements.