How it works
Dirty water is poured from the top and passes through different layers: mesh, gravel, sand and cloth/cotton. Each layer traps particles of different sizes, and gravity moves the water through the filter.

Results

• The filtered water was visibly clearer than the original muddy water.

• Large debris was stopped by the mesh and gravel.

• Finer particles were retained by the sand and cloth layers.

• The system works without electricity, only using gravity.

Limitations
The water looks cleaner but is not drinkable, because microorganisms and dissolved substances are not removed. The filter also needs cleaning after several uses.

CEIP Na Caragol, Artà, Mallorca, Spain.

Teacher: Iolanda Carrillo Flores

Students built a floating barrier using corks, straws and mesh to stop trash in a mini-river.

most floating waste was successfully trapped.
What worked: corks kept the barrier floating and the mesh stopped small plastics.
What failed: some trash escaped from the sides.
Improvement: better side sealing and a V-shaped design to guide waste more effectively.

Teacher: Helena Pires

In this activity, we created a sand filter using cotton, sand, and gravel. The gravel trapped large dirt particles, the sand filtered smaller particles, and the cotton helped make the water clearer. After filtration, the water looked cleaner and clearer, but it was not completely transparent. The best results were achieved when cotton and sand were used together. To improve the filter, more layers could be added, finer sand could be used, or different filter materials such as activated carbon could be tested. This activity helped us understand how water filtration works.

A Multi-Stage Bio-Filter

The students evaluated a gravity-fed filtration system designed to remove sediment and organic pollutants from a simulated runoff sample.

WE FOUND THAT ;

* Effective Retention: The vertical column successfully cleared the water's turbidity, specifically targeting larger debris like leaf litter and sand.

* Structural Success: The layering of activated charcoal was pivotal in neutralizing odors, while the coarse gravel provided a sturdy base that prevented the filter media from compacting too tightly.

* Trapping Efficiency: The fine-weave cloth at the outlet was highly effective at catching micro-sediments that bypassed the upper layers.

Limitations: Soil, sand and tiny particles entered the water barrier.

Improvement: A thicker barrier might have better sealing effects for the small particles.