Ultraviolet

It is proven scientifically that 85% of child sickness and 65% of adult diseases are produced by water-borne viruses, bacteria and intestinal protozoa such as Cryptosporidium and Giardia. Inappropriate water treatment can lead to heath problems – hepatitis B, tuberculosis, meningitis, typhoid fever, tricomoniasis, and cholera, glaucoma, gastrointestinal pain, salmonella, poliovirus, and diarrhea. In North America, E.coli O157:H7, an extremely dangerous strain of E.coli bacteria, infects more than 80,000 people annually. Fortunately, E.coli O157:H7 is easily inactivated by UV light.

Disinfecting your drinking water with ultraviolet light (UV) makes good sense. It’s environmentally safe, it’s well proven, and it’s the way of the future for water disinfection requirements around the globe.

Ultraviolet (UV) Disinfection

The Process

Ultraviolet (UV) disinfection uses a UV light source, which is enclosed in a transparent protective sleeve. It is mounted so that water can pass through a flow chamber, and UV rays are admitted and absorbed into the stream. When ultraviolet energy is absorbed by the reproductive mechanisms of bacteria and viruses, the genetic material (DNA/RNA) is rearranged and they can no longer reproduce. They are therefore considered dead and the risk of disease has been eliminated.

UV-rays are energy-rich electromagnetic rays that are found in the natural spectrum of the sunlight. They are in the range of the invisible short wave light having a wavelength ranging from 100 to 400 nm (1 nanometre = 10-9m).

UV, like distillation, disinfects water without adding chemicals, and therefore possesses some of the same benefits as distillation. It does not create new chemical complexes, nor does it change the taste or odor of the water, and does not remove any beneficial minerals in the water.

Ultraviolet devices are most effective when the water has already been partially treated, and only the cleanest water passes through the UV flow chamber. PWC+ UV Purifiers use both a sediment and a carbon filter to clean the water prior to passing it through the UV light, to provide complete water quality solutions.

Ultraviolet light is a natural, cost effective, environmentally friendly disinfection process for use in homes where healthy water is a concern.

UV Systems are sized according to application requirements.

What is U.V. light:

U.V. is a proven means of addressing microbiologically contaminated waters. This simple and safe technology is suitable for small flow rates i.e. domestic applications and large flows for commercial and industrial uses.

These units produce ultraviolet light of between 200 – 295 nanometers (nm) by converting electrical energy through the use of a low pressure mercury vapour lamps. (commonly called U.V. Bulbs or U.V. Lamps.) These lamps are similar in design to standard flourescent lamps with a few exceptions. The U.V. lamp is manufactured with Quartz glass which allows for the transmitting of 90% of radiated energy. Fluorescent lamps also contain a thin coating of phosphor inside the lamp which converts the U.V. to visible light.

Microorganisms encompass a wide variety of unique structures and can be grouped into five basic groups.

Bacteria

Virus

Fungi

Protozoa

Algae

In simplest 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 that is targeted by U.V. light. As the light penetrates the cell wall and cytoplasmic membrane it causes a molecular rearrangement of the microorganism’s DNA and prevents it from reproducing.

If a Cell cannot reproduce it is considered dead.

How a U.V. unit works:

Water enters through the inlet port in the reactor chamber and flows around a high output U.V. lamp, this lamp emits powerful ultraviolet energy at the 253.7 nm wave length and is protected from contact with the water by a quartz sleeve. The treated water then exits through the outlet port. The design of a U.V is critical to its performance, the flow rate through the unit must allow for proper contact time.

Factors affecting U.V.

Suspended solids:

This can cause a shielding problem in which a microbe may pass through the unit without having any direct U.V. penetration. this problem can be reduced be mechanical filtration down to at least five microns.

Iron/Manganese:

Iron will cause staining of the Quartz sleeve with levels as low as 0.03 ppm and levels of manganese should not exceed 0.05 ppm. This staining will inhibit the transmission of U.V.light through the water in the chamber. If these problems exist then pretreatment will be required.

Calcium/Magnesium:

These will cause scale to form on the quartz sleeve and will be magnified during times of low or no flow. This scale will inhibit the transmission of U.V. light through the water in the chamber. If these problems are present they can be easily remedied by the use of an ion exchange softener.

Other absorbing compounds:

Compounds such as hemic and formic acids as well as tannins will reduce the amount of U.V. energy available to penetrate through the water and alter the DNA of the molecule.

Advantages of UV lights include:

Environmentally friendly, no dangerous chemicals to handle or store, no problems of overdosing.

Low initial capital cost as well as reduced operating expenses when compared with similar technologies such as ozone, chlorine, etc.

Immediate treatment process works, no need for holding tanks, long retention times, etc.

Extremely economical, hundreds of gallons may be treated for each penny of operating cost.

No chemicals added to the water supply – no by-products (i.e. chlorine + organics = trihalomethanes).

No change in taste, odor, pH, or conductivity or the general chemistry of the water.

Automatic operation without special attention or measurement, operator friendly.

Simplicity and ease of maintenance, periodic cleaning (if applicable) and annual lamp replacement, no moving parts to wear out.

No handling of toxic chemicals, no need for specialized storage requirements, no WHMIS requirements.

Easy installation, only two water connections and a power connection.

More effective against viruses than chlorine.

Compatible with all other water processes (i.e. RO, filtration, ion exchange, etc.)

The UV system, mounted on the wall (above right) is used to maintain a bacteria-free water supply in this clean-room environment. Here, stored RO permeate is continuously recycled through the UV system to prevent biological growth.

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 Solids or 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 / Manganese will cause staining on the lamp or quartz sleeve at levels as low as 0.3 ppm of iron and 0.05 ppm of manganese. Proper pretreatment is required to eliminate this staining problem.

Calcium / Magnesium Hardness will allow scale formation 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 build-up inside the sterilizer chamber and be deposited on the lamp or sleeve.

Other Absorbing Compounds such 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, DNA of the molecule.

Additional Factors Affecting UV:

Temperature is a determining factor. The optimal operating temperature of the UV lamp must be near 40°C (104°F). 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.

Summary

The need for chemical-free disinfection of water can be found in all areas of water treatment whether it be residential, commercial, institutional or industrial applications. The utilization of UV light is not a cure-all for microbial contamination, nor is it the replacement for traditional cleaning and sanitizing methods. It is however, a useful tool that has proven successful in thousands of installations over a period of 50 years. UV light’s physical rather than chemical process makes it an ideal system component for ease of maintenance, low operating cost, and operator safety.

Table 1

Typical UV Applications

Commercial

Campgrounds

Recreational Vehicles

Resorts

Hotels

Restaurants

Institutional

Hospitals

Schools

Nursing Homes

Fish Hatcheries

Laboratories

Industrial

Electronics

Food Packaging

Breweries

Bottlers

Ultraviolet System for Water Treatment in Karachi, Pakistan

Introduction to UV Systems in Water Treatment

Water treatment is an essential aspect of ensuring public health and safety, especially in urban areas like Karachi, Pakistan. Among the advanced water purification technologies available today, Ultraviolet (UV) systems for water treatment have emerged as one of the most effective methods for eliminating harmful microorganisms. These systems leverage UV radiation to disinfect water without the use of chemicals, ensuring a safe and eco-friendly solution. In this article, we delve into the benefits, applications, and considerations for UV water treatment systems, focusing on their relevance in Karachi.

How UV Systems Work

UltraViolet systems operate by exposing water to UV-C light, a specific wavelength of ultraviolet radiation that penetrates the DNA of microorganisms such as bacteria, viruses, and protozoa. This process disrupts their genetic material, rendering them incapable of reproduction and effectively neutralizing their ability to cause harm. Unlike chemical methods such as chlorine, UV treatment does not alter the taste, odor, or chemical composition of the water, making it an ideal solution for drinking water purification.

Benefits of Ultraviolet Systems for Water Treatment

1. High Efficiency in Disinfection

UV systems provide a 99.99% inactivation rate for harmful pathogens, including E. coli, Salmonella, and Giardia. This level of efficacy ensures that water is safe for consumption and other uses.

2. Chemical-Free Process

One of the key advantages of UV systems is their chemical-free nature, eliminating the need for potentially harmful additives. This makes UV-treated water safer for sensitive applications such as drinking, food preparation, and medical uses.

3. Cost-Effective Operation

UV systems are low-maintenance and have minimal operational costs. With no need for chemicals or frequent part replacements, they offer long-term savings compared to traditional water treatment methods.

4. Eco-Friendly Technology

UV treatment is a green technology that does not produce by-products or contribute to environmental pollution. It supports sustainable water management practices, which are crucial for a city like Karachi facing water scarcity challenges.

5. Easy Installation and Maintenance

UV systems are compact and easy to integrate into existing water treatment setups. Regular maintenance typically involves replacing the UV lamp, which is both straightforward and affordable.

Applications of UV Water Treatment Systems in Karachi

1. Residential Water Purification

UV systems are increasingly popular in homes across Karachi, where access to clean drinking water is often a challenge. These systems ensure households receive safe and pathogen-free water directly from their taps.

2. Industrial and Commercial Use

Industries in Karachi, such as food and beverage, pharmaceuticals, and textiles, require high-quality water for their processes. UV systems help meet these stringent water quality standards.

3. Hospitals and Healthcare Facilities

In healthcare settings, water purity is critical. UV systems provide an effective solution for ensuring sterile water for medical procedures, laboratory use, and general sanitation.

4. Municipal Water Supplies

UV systems are also suitable for large-scale applications, such as treating municipal water supplies in Karachi. By integrating UV technology, water authorities can enhance the quality of water distributed to the public.

Choosing the Right UV System in Karachi

When selecting a UV system for water treatment in Karachi, consider the following factors:

1. Flow Rate Requirements

Ensure the UV system is capable of handling the required water flow rate for your application. Systems are available in various capacities, from residential units to large-scale industrial setups.

2. Quality of Incoming Water

UV systems are most effective with clear water, as suspended particles can shield microorganisms from UV radiation. Pre-treatment methods such as filtration may be necessary for optimal performance.

3. Certification and Standards

Choose UV systems that comply with international quality and safety standards, such as NSF/ANSI 55 certification. This guarantees reliable and effective performance.

4. Local Suppliers and Support

Partner with reputable suppliers in Karachi who offer after-sales support, including installation, maintenance, and replacement parts.

Top Suppliers of UV Systems in Karachi

Karachi is home to numerous suppliers specializing in water treatment solutions. Some leading providers of UV systems in the region offer customized solutions for residential, commercial, and industrial applications. Ensure you choose suppliers with a strong reputation and a proven track record in delivering high-quality products and services.

Cost of UV Water Treatment Systems in Karachi

The price of UV systems in Karachi varies depending on the size, capacity, and features of the unit. On average:

Residential UV systems range between PKR 15,000 to PKR 50,000.
Commercial systems may cost from PKR 75,000 to PKR 200,000.
Industrial-scale units can go beyond PKR 500,000.

While the initial investment may seem high, the long-term cost savings and health benefits make UV systems a worthwhile investment.

Conclusion

In a city like Karachi, where water quality issues are prevalent, investing in a UV water treatment system is a practical and effective solution. These systems not only provide safe and chemical-free water but also support sustainable water management practices. Whether for residential, industrial, or municipal use, UV systems offer unparalleled advantages that cater to the diverse needs of Karachi's population.

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