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BUILDING UTILITIES 1HANDOUT # 3

Arch. John C. Ong

TYPES OF WATER TREATMENT

SEDIMENTATIONThis process removes some suspended matter from water simply by allowing time and the inactivity of water to do the

work of settling out heavier suspended particles.

COAGULATION (Flocculation)This process removes some suspended matter, along with some coloration. A coagulant such as alum (hydratedaluminum sulfate) is added to form a gelatinous substance called floc.

AERATION (Oxidation)This process can improve the taste and color of water, remove iron and manganese and decrease in corrosiveness. Inaeration, as much of the water surface as possible is exposed to air.

The methods used are rich in esthetic possibilities:

Spraying of water into air, the fall of a turbulent stream of water over a spillway, and flow forms, sculptural water fallsdesigned to carry water in a rhythmical, pulsating pattern

OZONATIONOzonation is a water treatment process that destroys bacteriaand other microorganisms through an infusion of ozone, a gasproduced by subjecting oxygen molecules to high electrical

voltages.Ozone is a very strong disinfectant, but it does not remain inwater very long. For that reason, chlorine is still added to protectthe water while it is in the distribution system.

FILTRATIONis the process of using a filter to mechanically separate amixture of solids and fluids.

http://en.wikipedia.org/wiki/Filter_(chemistry)http://en.wikipedia.org/wiki/Separation_of_mixtureshttp://en.wikipedia.org/wiki/Mixturehttp://en.wikipedia.org/wiki/Solidhttp://en.wikipedia.org/wiki/Fluidhttp://en.wikipedia.org/wiki/Filter_(chemistry)http://en.wikipedia.org/wiki/Separation_of_mixtureshttp://en.wikipedia.org/wiki/Mixturehttp://en.wikipedia.org/wiki/Solidhttp://en.wikipedia.org/wiki/Fluid

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TYPES OF FILTRATION

Slow Sand filtersUsed for rainwater application, low maintenance, easily constructed devices that should be cleaned as often as theturbidity of water demands. They are cleaned by the removal of filters, which are either washed for reuse or discarded.

Pressure Sand FiltersIt requires control and the attention of the operator, and thus are rarely used for individual water systems

Diatomaceous Earth FiltersAlso known as percoat or diatomite filtration, it relies on a layer of diatomaceous earth of a minimum 1/8 in. thickfilter element. This can be either vacuum or pressure type. They require periodic attention (1-4 days) to make iteffective. Diatomaceous earth, a substance composed of fossil diatoms, is used in filters, insulation, abrasives, paints,and varnishes.

Porous Stone, Ceramic or Unglazed Porcelain Filters (Pasteur Filters)These are usually made in small sizes so that they can be attached to water faucets

Nanofiltration (Fine Filtration)

These membrane sizes start with pore sizes of 0.2 to 0.3 microns. It is a combined process that removes iron, calcium,and/or manganese from water. With such extremely small pores sizes, this process requires very high water pressures.

Activated Carbon FiltersThese are particularly effective for removing tastes and odor. Water is passed through granular carbon, which attractslarge quantities of dissolved gases, soluble organics and fine solids.

Reverse OsmosisA widely use method for desalinating seawater, sometimes used to reduce the mineral content in water. An inert, semi-permeable membrane has higher pressure (30-1000psi) supply water on one side, as the pressure slowly forces waterthrough this filtering membrane, most of the minerals (dissolved solids) are removed. Dissolved chemicals, however

remain.

DISINFECTIONThis is the most important health-related water treatment. Although chlorination has become the standard approach toremoving harmful organism from water, there are other alternatives.

CHEMICAL DISINFECTANTSChlorineIt is the most widely used disinfectant in the world, though care must be taken because excessive amounts ofchlorine can cause corrosion as a result of its strong oxidation characteristics. Chloride is readily removed byactivated carbon filters and easily rinsed out from the system.ChloraminesThese compounds resulting from the reaction of ammonia with chlorine in water solution are used due to itssuperior chemical stability over chlorine.IodineThis common relative of chlorine has been used for years by campers in disinfecting unknown waters, thoughsome gram-negative bacteria can become resistant to iodine.Chlorine DioxideChlorine dioxide exhibits stronger disinfecting characteristics than chloramines, but there is little evidence ofextensive use of the disinfectant.

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An example of an excellent adsorbent

is the charcoal used in gas masks toremove poisons or impurities from astream of air.

COAGULATION SEDIMENTATION FILTRATION DISINFECTION

DISTILLATIONIn this process, water is heated to allow condensation. As the water turns to vapor, virtually all pollutants are leftbehind.

FLUORIDATIONFluoride may help in minimizing tooth decay but excessive amounts are toxic and caused mottled teeth. Fluoride levelsmust be carefully monitored.

CORROSION CONTROLIt is the control of concentration of elements in corroding supply and discharge lines. Corrosion is a slow degradation ofa metal by a flow of electric current from the metal to its surroundings.

NUISANCE CONTROLAlgae growths, the most prevalent nuisance, can usually be controlled by applying copper sulfate (blue stone or vitriol)to the water body. Cooling towers are an especially difficult water treatment problem. To treat cooling towers watersuccessfully, a method is used for microbial control, removing organics and precipitating organics.

ADSORPTION

Adsorption is a mechanism of contaminant removal making use of theadsorption phenomenon, the act of physical adhesion of molecules orcolloids to the surface of the medium w/o chemical reaction. Some porousmaterials have the ability to attract contaminants.

ULTRAVIOLET RADIATIONExposure to UV radiation is used in small-scale water supplies. Water is exposed to the rays after filtration becauseparticles of sediment in water might shield the bacteria.

WATER DESALINATIONThe procedure is done by heating seawater then pumping water into a low pressure tank, where the water vapor is

condensed and removed as pure water. The remaining liquid is called brine.

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Chlorine gas, a poison, was the first gas used in chemical warfare in World War I. It causes suffocation, constriction ofthe chest, tightness in the throat, and edema of the lungs.

BrineSalt water, particularly a highly concentrated water solution of common salt (sodium chloride). Natural brines occurunderground, in salt lakes, or as seawater and are commercially important sources of common salt and other salts,

such as chlorides and sulfates of magnesium and potassium.Brine is used as a preservative in meat-packing (as in corned beef) and pickling. In refrigeration and cooling systems,brines are used as heat-transfer media because of their low freezing temperatures or as vapour-absorption agentsbecause of their low vapour pressure. Brine is also used to quench (cool) steel.

Slow sand filter illustration