- Minor spelling change(in literature connections)
- Materials: Charcoal in what form?; clay also?
Duct tape or packaging tape?
A photograph of the assembled filter would be ideal.
What's the cheese cloth for? In what order are materials added? I think the fabric is essential and we need a clear description of it's use. It needs to be larger than the bottle diameter to contain each layer like a cup. Otherwise you will wash material out. Also, I think you need to rinse the setup with tap water before use or the fine particles from the dry materials will make the water murkier. In general this section is the weakest and needs substantial work and photographs.
You need some way to judge the effectiveness of filtration. How can you cheaply do this? One approach would be a visual comparison of the filtrate to a series of samples diluted from the murky water so that you can estimate that you removed x% of the murkiness
Why not suggest dropping filtered water onto one of these cheap bacterial culture techniques: Your_Body:_A_Bacteria_Incubator! or Ew!_Gross!_Germs! These links are easily made and you don't need to re-write the culture part of the exercise. Come up with a data-recording template and or graphing and you will have made a strong math connection.