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UV OFFERS RELIABLE DISINFECTION

 The term ultraviolet or “UV” light, as it is commonly referred to, is a proven means of addressing microbiologically contaminated water.  This simple, safe technology is suitable for both small flow residential applications as well as large flow commercial projects.

 Disinfection, in its literal sense, means free from infection.  The U.S. Environmental Protection Agency (EPA) and World Health Organizations (WHO) define water disinfection as having an absence of the indicator coliform bacteria.  Sterilization implies complete destruction of all forms of life.  For practical purposes, the term sterilizer is used as a generic term to describe ultraviolet technology.

 Ultraviolet is one energy region of the electromagnetic spectrum, which lies between the x-ray region and the visible region.  UV itself lies in the ranges of 200 nanometers to 390 nanometers. Since energy levels increase as the wavelength increases, x-rays have more energy than UV and UV has more energy than the visible light spectrum.

 The UV spectrum is divided into four regions, which are designated Vacuum UV, UV-A, UV-B, and UV-C.  We are particularly concerned with the latter three.

                 UV-Aor long-wave ultraviolet, which occurs between 325-390 nm bands, is represented by naturally occurring sunlight.  This range has little germicidal value.

                 UV-Bor middle-wave ultraviolet occurs between 295-325 nm and is best known for its use in sun tanning lamps.  These middle-waves may also be found in sunlight and provide some germicidal effect if exposure is sufficient.

                 UV-Cor short-wave ultraviolet occurs between 200-295 nm and is where the most effective germicidal action occurs.  The optimum UV germicidal action occurs at 265 nm.

 Since short-wave ultraviolet is screened out by the earth’s atmosphere, naturally occurring UV-C is rarely found on the earth’s surface.  For us to take advantage of the germicidal potential of UV-C, we must look to alternate means of producing UV light.  Production of radiant UV energy must therefore be accomplished through the conversion of electrical energy.  This conversion is accomplished with a low-pressure mercury vapor lamp.  UV light is produced as a result of the electron flow through the ionized mercury vapor between the electrodes of the lamp (it should be noted that the bluish glow given off by UV lamps is due to the starter gas inside the lamp and has no germicidal action itself).

 These UV lamps are similar in design to standard fluorescent lamps with a few notable exceptions.  UV lamps are typically manufactured with “hard glass” quartz as opposed to “soft glass” found in fluorescent lamps.  This quartz allows for a UV transmittance of over 90% of the radiated energy.  Fluorescent lamps also contain a thin coating of phosphor inside the lamp, which converts the UV to visible light.

 Microorganisms encompass a wide variety of unique structures and can be grouped into five basic groups: bacteria, virus, fungi, protozoa and algae.  In simplistic terms, a microorganism is made up of the cell wall, cytoplasmic membrane and the cell’s genetic material, nucleic acid.  It is this genetic material or DNA (deoxyribonucleic acid) that is the target for the UV light.  As UV penetrates through the cell wall and cytoplasmic membrane, it causes a molecular rearrangement of the microorganism’s DNA, which thus prevents it from reproducing.  If a cell cannot reproduce, it is considered dead. 

Due to individual cell makeup, different levels of UV energy are required for destruction.  UV lamps emit about 90% of their radiated energy at 253.7 nm, which, by coincidence, is very close to the peak germicidal effectiveness of 265 nm.

 The degree of microbial destruction is a product of both TIME, which is the actual residence, or contact time the water is within the sterilization chamber; and INTENSITY, which is the amount of energy per unit area (calculated by dividing the output in watts by the surface area of the lamp).  This product of intensity and time is known as the Dose and is expressed in microwatt seconds per centimeter squared (uwsec/cm2).

 

DESIGN

 The design of an ultraviolet sterilizer has an extremely important bearing on how the UV Dose is delivered.  As individual UV lamps emit a set amount of ultraviolet energy, it is important that a system be sized correctly.  Flow rates are the determining factor and must not be overstated.  The size of the reactor chamber is also of extreme importance since the delivered intensity decreases accordingly per the square of the distance from the lamp.

 Ballast selection must coincide with the correct operating current of the lamp since a loss in UV intensity will occur if the lamp is not driven at the correct output.  Optional solid-state ballasts offer the advantage of cooler operating temperatures, smaller space requirements and less weight, all with consistent power delivery.

 Quartz sleeves shield the actual water flow from the lamp, offer more uniform operating temperatures and allow for higher energy transmissibility into the water.

 The variety of optional features that may be built into the sterilizers include: UV monitoring devices that measure the actual UV output at 253.7nm, solenoid shut-off devices that will stop water flow in the event of system failure, flow control devices to properly limit the water flow in the units, audible and visual alarms (both local and remote) to warn of lamp failures, high temperature sensors to monitor excessive temperatures in the reactor chamber or control panel, and hour meters to monitor the running time of the UV lamps.

 

FACTORS AFFECTING UV

 The effectiveness of a UV system in eliminating microbiological contamination is directly dependent on the physical qualities of the influent water supply. 

Suspended Solidsor particulate matter cause a shielding problem in which a microbe may pass through the sterilizer without actually having any direct UV penetration.  This shielding can be reduced by the correct mechanical filtration of at least five microns in size.

 Iron/Manganesewill cause staining on the lamp or quartz sleeve at levels as low as 0.03 ppm of iron and 0.05 ppm of manganese.  Proper pretreatment is required to eliminate this staining problem.

 Calcium/Magnesiumhardness will allow scale information on the lamp or quartz sleeve.  This problem will be especially magnified during low flow (or no flow) times when the calcium and magnesium ions tie up with carbonates and sulfates to form hard scale buildup inside the sterilizer chamber and on the lamp or sleeve.

 Other Absorbing Compoundssuch as humic and fumic acids as well as tannins will reduce the amount of UV energy available to penetrate through the water to affect the genetic material, the DNA of the molecule.

 

ADDITIONAL FACTORS AFFECTING UV

 Temperature is a determining factor.  The optimal temperature of the UV lamp must be near 40oC (104oF).  UV levels will fluctuate with excessively high or low temperature levels.  A quartz sleeve is typically employed to buffer direct lamp – water contact thereby reducing any temperature fluctuations.  A typical method employed in a system without a quartz sleeve is to engineer the system to take into account these fluctuations and typically de-rate the regular flow rate by the corresponding amount.

  

Microorganism Destruction Levels

(Ultraviolet energy at 253.7 nm wavelength required for 99.9% destruction of virus microorganisms – in uwsec/cm2)

Bacillus anthracis

8,700

Corynebacterium diphtheriae

6,500

Dysentary bacilli (diarrhea)

4,200

Escherichia coli (diarrhea)

7,000

Legionella pneumophilia

3,800

Mycrobacterium tuberculosis

10,000

Pseudomonas aeruginosa

3,900

Salmonella (food poisoning)

10,000

Salmonella paratyphi (enteric fever)

6,100

Salmonella typhosa (typhoid fever)

7,000

Shigella dysentariae (dysentery)

4,200

Shigella flexneri (dysentery)

3,400

Staphylococcus epidermidis

5,800

Streptococcus faecaelis

10,000

Vibro commo (cholera)

6,500

Bacteriophage (E. Coli)

6,500

Hepatitis

8,000

Influenza

6,600

Poliovirus (poliomyelitis)

7,000

Baker’s yeast

8,800

 

 

SUMMARY

 The need for ultraviolet sterilization products can be found in virtually all areas in both residential and commercial water applications alike.  UV’s physical process makes it the ideal system component for those multiple water problems.  Its simplistic design, ease of maintenance and low capital and operating costs make UV the number one choice in contaminated water situations.  Next time, purify your water nature’s way…use ultraviolet light

 

 

 

These compact line of ultraviolet water disinfection systems are ideally suited for point-of-use filtration, reverse osmosis, pre or post disinfection or with a myriad of other applications.  The low-pressure germicidal lamps provide an economical way of treating water requiring a 99.9% reduction in bacteria and viruses.  This process is accomplished without adding any potentially harmful chemicals to your drinking water.  WPS 2000 disinfection system’s use of UV technology is the safest way of treating your water.

  

Features:

  • The high-energy efficient electronic ballasts features lamp failure detection, audible alarm, and power-on indicator.

  • Compact design incorporating 316 stainless steel reactor chambers with power supply.

  • 99.9% destruction of bacteria and viruses at rated flow.

  • Nature’s way to protect your water without the addition of harmful chemicals.

  • Versatile mounting of chamber.

  • Five-year warranty on reactor chamber for unparalleled protection.

 

Optional Features:

  • External power supply mounted beside the UV chamber

  • UV detection system with remote alarm and solenoid valve option for maximum performance.

  • UV chambers brilliantly polished for laboratory or medical applications.


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