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Water Filtering Ecological Device

“Water Filtering Ecological Device” is the name of a project developed by Rodica Stoian and Monica Ivancea, two 16- year-old students from Vasile Alecsandri High School in Galati, Romania with the collaboration of their biology teacher. This project, presented this year during the 8th edition of the National Environmental Designs Contest, has been awarded with the silver medal.

What this project is about?
Water pollution is a serious problem for the entire world. It threatens the health and well-being of humans, plants, and animals. How to find ways to tackle this issue? It was the question explored by these two pupils, who decided after carrying out some research to create a water filtering ecological device. The aim of the project was to make this device cheap, useful, practical, ecological and easy to make even in developing country.

Material used
Undrinkable water source, a decanter, a water pump, a mechanical filter, chemical filters, a biological filter, and one drinkable water accumulation can.

How to make the device?

  • The decanter
    The decanter needs to have a high capacity so that a large amount of water can decant in a short time. It may be made from metal (treated) or glass.
    - Take a plastic can and place it under the water source for an easier catch.
    - Put a hose in the container above the safety level and the alluvium layer, through which the water is taken to the mechanic filter via the pump.
    In the can, the decantation will take place without bringing any additional purification products.

Tip: As water source, any stream or backwater may be used as long as it is connected to the decanter through a bevel trench. The gradient must be big enough to let the water get into the decanter without electricity.


  • The water pump
    The water pump is made of a propeller, an eccentric, 2 hoses, a shaft and a rack built up from a stiff material.
    - 2 racks are used as follows: one for the propeller (picture on the left) and the other one for the pump (picture on the right).

    - Use a 20 cm diameter propeller fixed on a strong axle. In order to fix the axle, you can use 2 ball bearings attached to the rack.
    - On the other side of the axle, an eccentric should be placed which applies the screw to the pump when the propeller spins.
    - For the pump, use a plastic can connected to 2 hoses (see the above picture on the right). One of them drives the water from the decanter to the pump, whereas the other one takes the water from the pump to the mechanic filter.

Tip: The pump will function just as long as the wind blows with enough strength. If the wind doesn’t blow, the propeller can be connected to a generator and a battery, for catching the energy produced while the airscrew is running and release it when it’s necessary.

  • The mechanic filter
    The mechanic filter is based on gravel of different dimensions and riddles. It will clean the water from medium drainage. It may be built from metal, glass or Plexiglas. The gravel will be put in several filter beds, separated by different riddles.
    - The filter is made of 2 cylindrical and Plexiglas cans, which sustain the filtering layers. The density of the riddles varies. Use for the first gravel layer arras, and for the second one, canvas.
    - From the second filter can, the water goes directly into the chemical filter.

Tip: The filter can be placed on an inclined plane with a β angle big enough so that the water can go on to the following filter. Still β angle shouldn’t be too big; otherwise the pump would need too much energy to get the water across the hose, to the filter.

  • The chemical filter can
    The chemical filter can is located under the mechanic filter, ground-based. In this can, the chemical purification will take place, using the aluminum sulphate.

  • The chemical filter
    a) Aluminium sulphate Al2(SO4)3
     - Use a rectangular plastic can big enough to sustain the mechanic filter. The chemical filter (with aluminium sulphate) is acquired as it follows: for 1L dirty water, we add aluminium sulphate 10% in various amounts (from 0,12 to 0,15 mL). 
    - To mix the substance, you will need a glass rod. The admixture is homogenized for 3 min. at maximum speed or for 5 min. at a medium speed.
     - The decantation takes 30 min. During the decantation, we can see the accretion of some alluvium layers at the bottom of the can. On the can, at a safety level (above the alluvium layer), will be attached a valve for the drinkable water.

Tip: For a more efficient purification, a second filter in chlorine can be used. In industry, you can find  bottled chlorine but for ordinary customers, Chloramine 25% Cl may be used. It is added Chloramine 0,1% from the water volume.

b) The absorbent carbon
- the absorbent carbon is used to clear away the bad smell, taste and colour from the water;
- from here, the water goes to the accumulation can.

  • The accumulation can
    The can must have a smaller height than the height valve. If necessary, it may be located under the level of the ground. The can should be sterile, covered and sealed in order to prevent the contaminants from getting in.

The results

Action Decantation Pumping 100 ml water Manual mixing Decantation Entire filtering process
Time needed 30 min 15 min 5 min 30 min 1 h 15 min

The advantage of this device lies in the use of the mechanic power generated by the wind power. Transporting the electricity is thus no longer a problem. But the absence of wind in some areas can make this fitting inefficient. Another solution is to include batteries.

Through the following device, the students made a first step to re-establish the balance between the physical, chemical and biological factors while obtaining some necessary ecological products.

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