For our design project we are designing a water
filter that will filter out heavy metals, bacteria, and will decrease the
turbidity. The filter will have three layers; one with activated carbon, one with
zeolite, one with sand. The water will flow through the filter, layer by layer,
and the water bottle will collect the freshly purified water.
Before deciding on the ingredients
of the filter we looked into other widely known water purifying systems. The
Brita® Pitcher filters out chlorine, copper, cadmium, and mercury through the
use of activated carbon. Activated carbon is specially
manufactured so that there are more bonding sites for organic impurities. When
contaminated water passes through the carbon filter, molecules such as heavy
metals are more attracted to the carbon bonding sites than they are to water.
As water passes through the carbon the impurities are removed. Since
several heavy metals are found in creek water, activated carbon was a necessary
choice for our filtering system.
The second
layer in the filter is zeolite. Zeolites are hydrated aluminosilicate minerals
made from AlO4 and SiO4. Zeolites have an open
3-dimensional crystalline structure with open pores. This special structure
allows for zeolite to trap other molecules within the pores. This property
makes zeolite a good water softener. The manufactured zeolites can be designed
to have the pores be filled with sodium ions and to have the pores be a certain
size so that it can trap a molecule of a very specific size. The creek water
that contains calcium and magnesium will flow through the zeolite layer, the
calcium and magnesium ions will be trapped in the pores, and sodium will be
released into the water.
The final
layer of the filter will be sand. This layer will decrease the turbidity in the
water. The turbidity is the overall cloudiness in the water sample, which can
be caused by many types of particles. In the water sample that we took we
expect that there will be small amounts of silt. The suspended particles in the
water will get trapped in between the fine grains of sand. Sand has also been
used to filter out some levels of bacteria.
The last
step of the water purification system is to leave the water bottle out in the
sunlight for six hours after all of the water has been filtered. It is
important that the water is filtered before left out in the sun because
suspended particles can inhibit the sunlight from contacting all of the water
molecules. Exposing contaminated water to ultraviolet rays kills a wide variety
of the bacteria living in the water. The UV rays harm the DNA within the
bacteria, causing it to be unable to reproduce. UV rays are highly effective in killing E. coli, salmonella, dysentery, typhoid, and more. Though this method does not account for all of the potential bacteria that would be in our water sample, it will get rid of the most common microorganisms by using solely the sun.
Sources:
http://www.ewb-usa.org/files/GeneralInformationHandoutonUVDesinfection.pdf
Please write a literature review and cite references, which support your design.
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