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Learn about the efficient water treatment methods like adsorption, flocculation, and filtration for safe drinking water production. Explore the role of activated carbon in removing contaminants and ensuring water quality.
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CE3503 Environmental Engineering Water Treatment Dr. Martin T. Auer MTU Department of Civil & Environmental Engineering
Charge Neutralization
Chlorine Distribution sorption
Carbon Adsorption Organic chemicals are typically removed from a water supply prior to distribution through the process of adsorption: the physical-chemical attraction of a solid material for a chemical in solution. In adsorption, the chemical being adsorbed is termed the adsorbate and the solid to which it sorbs is the adsorbent. Effluent stream Influent stream
6 (mg/L) 4 2 Concentration 0 0 2 4 6 8 Time (d) … tendency to sorb For adsorption to be effective, the chemical must sorb strongly. Poorly soluble (hydrophobic) compounds (e.g. the components of gasoline) adsorb more strongly than highly soluble (hydrophilic) compounds (e.g. table salt). Poorly sorbed Strongly sorbed
… activated carbon The most commonly used adsorbent is granular activated carbon (GAC). These irregular particles, 0.2-5 mm in diameter, are a char of carbon material (wood or coal). They are ‘activated’ or made more porous by exposure to steam at high temperature. Activated carbon has 1000 m2 of adsorbing surface area per gram (~ 1 teaspoon) or equivalent to that of a 40 acre farm in one handful! Source: Sontheimer et al. 1988 Source: Chemviron Carbon Source: Millenium Inorganic Chemicals
… application in water treatment In drinking water treatment, adsorption with GAC is accomplished using a packed bed column. The untreated water is introduced at the top of the column and trickles down through the GAC. Contaminants are removed en route and clean water emerges at the bottom of the column. In application, columns 6 feet in diameter and 30 feet in height are not uncommon. Carbon Bed GAC columns
… column operation Water flows thru the column and contaminants are adsorbed. With time, the GAC becomes saturated (sorption capacity is reached) and contaminants exit the bed (breakthrough). The exhausted carbon must then be replaced. Cin exhaustion Cout Ceq breakthrough
Asbestos/Arsenic/Metals Removal Ferric sulfate: asbestos, arsenic, cadmium, chromium ,copper, lead, mercury, molybdenum, selenium, silver Alum: asbestos, nickel, uranium
Ultrafiltration polypropylene fiber 300 µm ID 500 µm OD
Ultrafiltration 0.2 µm nominal pore size
permeate flow epoxy seal Ultrafiltration Technology raw water in
Ultrafiltration banks of fiber bundles
Ultrafiltration contaminants backwashing
Home Water Treatment Reverse osmosis unit (salt) Softening by ion exchange (hardness)
Home Water Treatment • Three step process: • sieve and bottom filter – rust, sand, turbidity • activated carbon filter – chlorine and SOCs • ion exchange resin – metals Bottled Water: $8 /gallon Tap Mount: $0.25 / gallon Municipal: $0.0015 / gallon Achieves 99.99% removal of Giardia and Cryptosporidium cysts, but does not remove all pathogenic organisms.