Environmental Sciences Fair Project
Ultraviolet Light and Activated Carbon Treatment for Water Purification


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Project Information
Title:Cheap and Portable Ultraviolet (UV) Light and Activated Carbon Treatment System for Water Purification
Subject: Environmental Sciences
Subcategory: Water Treatment
Grade level: Middle School - Grades 7-9
Academic Level: Ordinary
Project Type: Experimental
Cost: Low
Awards: Google Science Fair Finalist
Affiliation: Google Science Fair
Year: 2012
Description: In this project were compared three water treatment methods: UV treatment, activated carbon treatment, and UV together with activated carbon treatment - in order to develop a portable cheap water treatment system for poor countries.
Link: sites.google.com...
Background

Activated Carbon Water Treatment

Granular activated carbon has a relatively larger particle size compared to powdered activated carbon and consequently, presents a smaller external surface. Diffusion of the adsorbate is thus an important factor. These carbons are therefore preferred for all absorption of gases and vapors as their rate of diffusion are faster. Granulated carbons are used for water treatment, deodorization and separation of components of flow system and is also used in rapid mix basins.

Bead activated carbon is made from petroleum pitch and supplied in diameters from approximately 0.35 to 0.80 mm. Similar to EAC, it is also noted for its low pressure drop, high mechanical strength and low dust content, but with a smaller grain size. Its spherical shape makes it preferred for fluidized bed applications such as water filtration.

Porous carbons containing several types of inorganic impregnate such as iodine, silver, cations such as Al, Mn, Zn, Fe, Li, Ca have also been prepared for specific application in air pollution control especially in museums and galleries. Due to its antimicrobial and antiseptic properties, silver loaded activated carbon is used as an adsorbent for purification of domestic water. Drinking water can be obtained from natural water by treating the natural water with a mixture of activated carbon and Al(OH)3, a flocculating agent. Impregnated carbons are also used for the adsorption of Hydrogen Sulfide(H2S) and thiols. Absorption rates for H2S as high as 50% by weight have been reported.

Iodine number is defined as the milligrams of iodine adsorbed by one gram of carbon when the iodine concentration in the residual filtrate is 0.02 normal. Basically, iodine number is a measure of the iodine adsorbed in the pores and, as such, is an indication of the pore volume available in the activated carbon of interest. Typically, water treatment carbons have iodine numbers ranging from 600 to 1100. Frequently, this parameter is used to determine the degree of exhaustion of a carbon in use. However, this practice should be viewed with caution as chemical interactions with the adsorbate may affect the iodine uptake giving false results. Thus, the use of iodine number as a measure of the degree of exhaustion of a carbon bed can only be recommended if it has been shown to be free of chemical interactions with adsorbates and if an experimental correlation between iodine number and the degree of exhaustion has been determined for the particular application.

Granular activated carbon filtering utilizes a form of activated carbon with a high surface area, and adsorbs many compounds, including many toxic compounds. Water passing through activated carbon is commonly used in concert with hand pumped filters to address organic contamination, taste, or objectionable odors. Activated carbon filters aren't usually used as the primary purification techniques of portable water purification devices, but rather as secondary means to complement another purification technique. It is most commonly implemented for pre- or post-filtering, in a separate step than ceramic filtering, in either case being implemented prior to the addition of chemical disinfectants used to control bacteria or viruses that filters cannot remove. Activated charcoal can remove chlorine from treated water, removing any residual protection remaining in the water protecting against pathogens, and should not, in general, be used without careful thought after chemical disinfection treatments in portable water purification processing. Ceramic/Carbon Core filters with a 0.5 m or smaller pore size are excellent for removing bacteria and cysts while also removing chemicals.

UV Water Treatment

Solar ultraviolet water disinfection, also known as SODIS, is a method of disinfecting water using only sunlight and plastic PET bottles. SODIS is a free and effective method for decentralized water treatment, usually applied at the household level and is recommended by the World Health Organization as a viable method for household water treatment and safe storage.[1] SODIS is already applied in numerous developing countries. Educational pamphlets on the method are available in many languages, each equivalent to the English-language version.

See also:
Portable Water Purification
Powdered Activated Carbon Treatment
Activated Carbon
Carbon Filtering
Water Purification
Solar Water Disinfection

Source: Wikipedia (All text is available under the terms of the Creative Commons Attribution-ShareAlike License)

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