Materials in Water Filtration

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From environmental advantages to personal protection against harmful toxins, the use of water filtration systems continue to rise. Contaminants within drinking water, such as disease-causing microorganisms, toxic metals, as well as organic and inorganic chemicals, pose hazardous health effects that can cause developmental delays in children, birth defects, and even cancer.

While community water treatment facilities are useful, they cannot guarantee complete control over the contamination of our drinking water sources. Natural materials such as carbon, ceramic, and sand are some of the most efficient water filtration systems to protect against these deleterious effects.

The most common type of water filter, particularly of those for household use, is activated carbon based on charcoal. Factors such as molecular weight, pH, particle size, surface area, and flow rate significantly determine carbon’s purification ability.

Within carbon’s molecular surface area, several attractive forces exist to attract other molecules. These forces function similarly to that of a gravitational force, where contaminants within the water adhere to the large surface area of carbon1. The interaction of these forces depends upon carbon’s non-polar nature, where the electrical charges surrounding a single molecule of carbon are evenly distributed, canceling out any charge to the molecule2.

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Toxins that are not successfully removed by carbon can include arsenic, copper, fluoride, and some viruses. Due to these restrictions, carbon filters can be made with iron, manganese, hydrogen sulfide, or a sediment pre-filter in order to enhance the removal of certain harmful particles within water.Chlorine, along with other deleterious chemicals such as benzene, radon, solvent trihalomethane compounds, and volatile organic chemicals such as pesticides, are all successfully filtered out of drinking water in the presence of a carbon filter3. However, carbon filters are not particularly effective in removing compounds that exceed the size of carbon itself.

Ceramic water filters offer an inexpensive and effective method of filtration throughout the world. While there are numerous styles and forms, the most widely implemented ceramic filter is a known design by Potters for Peace. With a cost ranging from $7.50-$30, ceramic water filters have proven to be particularly useful in preventing early childhood diarrhea (ECD) in developing countries4.

It is estimated that 1.6 million children die each year worldwide as a result of ECD, which can be attributed to poor access to water, sanitation, and hygiene infrastructure. Often produced locally, this flowerpot shaped filter holds approximately 8-10 liters of water as it sits above a plastic or ceramic storage receptacle.

Filters are often impregnated with colloidal silver in order to ensure the complete removal of bacteria, viruses, and protozoa5. While effective at removing larger protozoan and bacterial organisms, smaller viral organisms are often unable to pass through the pores of a ceramic water filter.

There are two types of sand filtration; rapid sand filtration and slow sand filtration. Most often used in conjunction with other water purification methods, rapid sand filtration uses the mechanism of physical straining to trap large particles between the sand grains.

Within the slow sand filter, microorganisms such as bacteria, viruses, and parasites are able to travel through the sand and are absorbed onto the sand particles6. Often referred to as a bio-sand filter for its presence of biological activity, slow sand filters contain very find sand, allowing for the removal of particles that are smaller than the spaces between the sand grains.

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The term “bio-sand filter” comes from the dense biological zone that forms within the top layers of the sand following water filtration. While slow sand filtration is often used in the treatment of groundwater, its principal use is in the removal of pathogenic organisms and organic matter in surface waters7. The World Health Organization claims that slow sand filters offer the greatest quality in the improvement in the physical, chemical, and bacteriological of treated surface water.

Depending on certain factors, such as the cost and efficacy of removal, each type of water filtration system holds certain advantages and disadvantages. Regardless of which method of filtration is chosen, it is imperative to utilize one of the various options available, to ensure that our water, particularly drinking water, is safe and free from any potential contaminants.

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