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Carbon filtration:
Carbon filtering is a method of water purification that uses a piece of activated carbon to remove contaminants and impurities, utilizing chemical adsorption. Each piece of carbon is designed to provide a large section of surface area, in order to allow contaminants the most possible exposure to the filter media. One pound of carbon contains a surface area of approximately 500.000 m² (125 acres). This carbon is generally activated with a positive charge and is designed to attract negatively charged water contaminants.
Carbon filters are most effective at removing chlorine, sediment, and volatile organic compounds (VOCs) from water. They are not generally effective at removing minerals, salts, and dissolved inorganic compounds.
Typical particle sizes that can be removed by carbon filtres range from 0.5 to 50 micrometres microns). The particle size will be used as part of the filter description. The efficacy of a carbon filter is also based upon the flow rate regulation. The slower water is able to flow through the filter, the more contaminants are exposed to the filter media.
There are two predominant types of carbon filters used in the filtration industry: powdered block filters and granular activated filters. In general, carbon block filters are more effective at removing a larger number of contaminants, based upon the increased surface area of carbon. Many carbon filters also use a secondary media, such as silver or KDF-55, to prevent bacteria growth within the filter.
Sediment filtration:
Sediment filtration is used to remove suspended matter such as sand, silt, loose scale, clay or organic material from the water. Untreated water passes through a filter medium and suspended matter is trapped on the surface or within the filter medium.
A sediment filter removes suspended material such as sand, silt, loose scale, clay or organic material from the water. These materials can be the cause of turbidity or cloudiness in the water. Sediment filters also can remove insoluble (not dissolvable) or suspended iron and manganese. Sediment filters often are used in combination with another drinking water treatment method for removal of contaminants such as dissolved iron, manganese or hydrogen sulfide. For instance, sediment filters often are used after aeration, ozonation or chlorination. These treatments oxidize dissolved iron, manganese or hydrogen sulfide into solid particles that the filter then traps. Sediment filters also are used as pre-treatment for other processes such as activated carbon (AC) filtration and reverse osmosis (RO) in order to increase their effectiveness
Sediment filters alone do not effectively remove dissolved organic or inorganic material that may be harmful. They do not effectively remove nitrate, heavy metals, pesticides or trihalomethanes (by-products sometimes formed during drinking water chlorination). Cartridge sediment filters are not generally recommended for removing microbial contaminants. Occasionally drinking water may contain very fine suspended material, sometimes referred to as "flour sand," or very fine clay particles, which may be too small to be removed by typical sediment filtration but may be more effectively removed by another process.
Ion exchange:
Ion exchange is defined as an exchange of ions between two electrolytes. During ion exchange processes ions are exchanged between a solution and an ion exchanger, a non-aqueous solid or gel. Typical ion exchangers are ion exchange resins, zeolite, montmorillonite, clay, and humus. Ion exchangers are either cation exchangers for positively charged cations or anion exchangers for negatively charged anions. There are also amphoteric exchangers that are able to exchange both cations and anions simultaneously. However, the simultaneous exchange of cations and anions is more efficiently performed in ion exchange reactors called mixed beds which contain mixed anion and cation exchange resins. Ion exchange is a reversible process and the ion exchanger can be regenerated or loaded with desirable ions by washing with an excess of these ions.
Ion exchange is a method widely used in household and industrial water purifications to produce soft water. This is accomplished by exchanging calcium Ca2+ and magnesium Mg2+ cations against sodium Na+ or hydrogen H+ cations (see Water softening). However, the field where ion exchange is the most economically efficient is ionic separations where a product of highest purity must be obtained, an ion contained in a low concentration must be extracted, or streams of varying composition must be treated. Thus a typical example of application is preparation of high purity water for electronic and nuclear industries.
Ion exchange chromatography is a chromatographical method that is widely used for chemical analysis and separation of ions. For example, in biochemistry it is widely used to separate charged molecules such as proteins.
Ion Exchange is also widely used in the food & beverage, hydrometallurgical, metals finishing, chemical & petrochemical, pharmaceutical, sugar & sweeteners, ground & potable water, nuclear, softening & industrial water, semiconductor, power, and a host of other industries.
Reverse osmosis:
Diffusion is the movement of molecules from a region of higher concentration to a region of lower concentration. Osmosis is a special case of diffusion in which the molecules are water and the concentration gradient occurs across a semipermeable membrane. The semipermeable membrane allows the passage of water, but not ions (e.g., Na+, Ca2+, Cl-) or larger molecules (e.g., glucose, urea, bacteria). Diffusion and osmosis are thermodynamically favorable and will continue until equilibrium is reached. Osmosis can be slowed, stopped, or even reversed if sufficient pressure is applied to the membrane from the 'concentrated' side of the membrane.
Reverse osmosis occurs when the water is moved across the membrane against the concentration gradient, from lower concentration to higher concentration. To illustrate, imagine a semipermeable membrane with fresh water on one side and a concentrated aqueous solution on the other side. If normal osmosis takes place, the fresh water will cross the membrane to dilute the concentrated solution. In reverse osmosis, pressure is exerted on the side with the concentrated solution to force the water molecules across the membrane to the fresh water side.
Ultraviolet:
Ultraviolet radiation is a type of light, unlike visible light, that cannot be seen. Its wavelengths, expressed in Angstrom units (one Angstrom unit wavelength equals one hundred-millionth of a centimeter), are shorter than the wavelengths of visible light and carry more energy. Because of this high concentration of energy, UV radiation has the unique ability to kill microorganisms with which it comes in contact.
Ultraviolet radiation sterilizes water. Sterilization implies that life such as bacteria, viruses, yeasts, molds, and algae are destroyed. For UV radiation to work, a 2537 Angstrom unit (254 nanometers) wavelength must come in contact with the microorganism to inactivate it. When ultraviolet rays reach the microorganism, they strike the heart of the organism destroying the DNA (deoxyribonucleic acid) and preventing it from reproducing. Table I give the amount of UV necessary to kill various microorganisms. The Public Health Service does not require water to be completely sterilized to be potable, but water must conform to the departments drinking water standards or those of the agency governing your supply. To meet drinking water standards, the supply must contain less than 2.2 coliforms per 100 ml. The microorganisms in the coliform group are usually associated with fecal matter or human and animal wastes and suggest the presence of pathogenic (disease-causing) organisms such as typhoid and dysentery. If 100% sterilization is required, a different sizing formula must be used.
There are two main factors affecting the ability of UV light to sterilize water; they are energy and exposure. The amount of power delivered by the lamp and the amount of time the water is exposed to the UV radiation are principal factors in UV water sterilization. The germicidal spectrum of the ultraviolet wavelength, which peaks at 2537 Angstroms, ranges from 2000 to 3000 Angstroms. The total UV energy emitted from all sides of the UV lamp is expressed in watts. Over time, a lamps intensity decreases, and as a result, the UV output gradually decreases. Because of this, lamps must be replaced periodically for optimum efficiency. The performance of various types of lamps is shown in Table II. As options, ATS sterilizers have light detectors or UV monitors. Light detectors detect if a bulb is on (light), and monitors detect if there are enough Angstroms to kill the most significant amount of waterborne pathogenic microorganisms.
The total exposure of the liquid is measured in micro-watt seconds per centimeter square ( Microwatts/CM2). In other words, exposure is a product of the energy produced by the lamp over a certain amount of time and within a given area. A short exposure at a high intensity UV and a long exposure at a low intensity UV produce the same number of micro-watt seconds per centimeter square.
The amount of energy available to any microorganism from a given ultraviolet source is dependent on the UV transmittability of the liquid. The transmission of UV rays is effected by the waters depth (the amount of water through which the UV travels) and the waters absorption coefficient (the amount and type of dissolved and suspended matter in the water which absorbs the UV before it reaches the microorganism). Because the efficiency of the sterilizer is determined by the quality of the water, the physical requirements of less than 10 NTU of turbidity, 15 TCU of color, and 0.2 ppm of iron should be met before an ATS water sterilizer is installed. Table III illustrates the percentage of transmission of ultraviolet for water at various absorption coefficients. The absorption coefficient must be known for proper sizing.
The amount of ultraviolet energy the UV lamp produces is also dependent upon the primary voltage output and the lamp wall temperature. The effect of temperature is that the lamp will be only about 22% efficient in generating bactericidal radiation at 56.6F° (12 deg. C°). We use high intensity UV lamps inside a high-transmission clear fused quartz jacket so that an optimum temperature of 104 F° (40 C°) is maintained for 100% UV output.
Ozone:
Ozone is formed naturally by the Ultra-Violet Rays of the sun (photochemical reaction) and by lightning (bio-electrical reaction). Ozone also formed synthetically by passing air or oxygen over a Ultra-Violet lamp (photochemical reaction). Some of the oxygen molecules split into two separate oxygen atoms. These single atoms then form semi-unstable bonds with the oxygen molecules (O2+O1=O3/Ozone). These oxygen molecules are highly reactive. This reactivity is because of the third atom of oxygen, also know as a 'Hungry Atom'. This atom being very eager to break away from this semi-unstable bond and react with any oxidizable compound (organic or inorganic). Also due to its reactivity, Ozone has a very short life span (about 20 min.).
Ozone has been known for almost a century now, and quite a lot has been known about it. When used correctly, like any other oxidizer, ozone is safe. A properly implemented and operated ozone system poses no health hazards at low level exposure. Ozone is much less a danger than regular household bleach and many other chemicals found in the average home. Approved by FDA for microbial treatment, ozone is used to purify drinking water, fresh produce and meat decontamination processing.
Ozone is the safest and second most powerful oxidant known to man. It performs 3,125 times faster than chlorine as a bactericide, and the strongest oxidant commercially available for air and water treatment. Ozone as an oxidant neutralizes contaminants or chemically alters them so that they can be more easily eliminated. Ozone while very powerful doesn't last long, just does its job and reverts to oxygen.
Ozone is extremely active. When it encounters a bacteria, virus or fungi, it ruptures the cell of the micro-organism. When it is faced with a compound like odors and pesticides, the extra atom of oxygen consumes them completely by oxidation reactions. Instead of masking the effect of unpleasant odors, ozone destructs the odor causing compounds chemically. Thereafter, the rest of ozone naturally reverts to oxygen very quickly.
Ozone is sparingly soluble in water. In water, there are two modes of action by ozone, direct oxidation and oxidation by hydroxyl radicals. This oxidation reaction in water causes it to sterilize, kill bacterium, refresh, whiten and deodorize. In water, ozone decomposes rapidly and the only residual is dissolved oxygen.
Ozone is non-carcinogenic (cancer-causing) and no denaturalization, but it may affect the respiratory system when the concentration is too high. The security of ozone has been proven by ozone drinking water in Europe and USA, and by food procession in Japan, France, and Australia.
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