Watertec UV System

With over 10 years of experience in the design of disinfection and oxidation systems, Watertec is recognised internationally as a leader in Ozone and Ultraviolet (UV) disinfection systems.

Key Features

  • Provides effective barrier against parasites such as Cryptosporidium and
  • Medium Pressure
  • Cost-Effective Power
  • Low
  • Zero Residual Disinfection
  • UV Intensity

Major Applications

  • BiologicalControl
  • Potable WaterDisinfection
  • Municipal WasteTreatment
  • TOCControl
  • OzoneDestruction
  • AdvancedOxidation

Watertec UV Systems are the answer for demanding water disinfection applications that require consistent water quality and reliable performance.

  • Total Organic Carbon (TOC)Control
  • Potable WaterDisinfection
  • Waste & RecycleWater
  • BiologicalControl
  • RecreationalSwimming
  • Pool Treatment
  • Experienced field service support for installation, start-up and
  • Unique vortex contact design
  • Unique quartz tube cleaning

The use of ultraviolet (UV) light for the treatment of water has developed rapidly over recent years. This growth has been associated with a better understanding of the technology and the development of more efficient and higher energy mercury lamps.

The two main areas of growth are associated with are water disinfection and oxidation of water contaminants, such as Total Organic Carbon (TOC).

Although the basic UV treatment process is simple, selecting the most appropriate technology and applying it for water treatment applications is somewhat more complicated.

The following information has been presented in a question and answer format as this better provides an overall understanding of the technology, various equipment designs and treatment applications.

What is Ultraviolet Radiation?

Ultraviolet radiation is part of the spectrum of electromagnetic radiation, defined as energy waves with both electric and magnetic components produced by the vibration or acceleration of an electric charge. Electromagnetic radiation ranges from waves of extremely high frequency and short wavelength to extremely low frequency and long wavelength. In order of decreasing frequency this spectrum contains gamma rays, x-rays, ultraviolet radiation, visible light, infrared radiation, microwaves and radio waves.

Regardless of frequency or wavelength, Electromagnetic waves travel at the speed of light in a vacuum.

Ultraviolet radiation is often divided into categories based on wavelength, UV-A (400 to 300nanameters nm), UV-B (315 to 280nm), UV-C (280 to 15nm).

The human eye responds to light with wavelengths from about 790nm (red) to 430nm (violet). Light with wavelengths shorter than the human eye can see is called ultraviolet (beyond violet) light.

UV light is contained in the range of wavelengths produced by the sun, however most UV light is absorbed by the ozone layer or reflected back into space, therefore only a small amount reaches the surface of the earth.

UV-A is responsible for the familiar suntan. Being a normal component of sunlight and by virtue of its relatively longer wavelength, UV-A can penetrate the atmosphere.

UV-B is found in the middle ultraviolet spectrum with the principal uses being for the treatment of diseases and testing the aging/degradation cycles of products.

UV-C is the shorter ultraviolet radiation and is the principle spectrum used in water treatment applications.

How does a U V Lamp work?

The principle of operation of a UV lamp is very similar to a normal florescent lamp used for domestic and office lighting. A florescent lamp consists of a phosphor coated glass tube that  is filled with an inert gas (argon) plus a small amount of mercury, and tungsten filaments are positioned at each end. The other components for this type of lamp are a ballast, which is used to limit the amount of current, which can flow through the tube, and a starter, which energises the two filaments when the lamp is first turned on.

The filaments supply electrons to ionise the argon, forming plasma that conducts electricity. The plasma then excites the mercury atoms, which emit visible and ultraviolet light. The light strikes the phosphor coating on the inside of the lamp, which converts the ultraviolet light into more visible light.

A UV lamp differs in that the outer casing is quartz rather than glass, as most (90-95%) of the UV light is transmitted through quartz, whereby up to 90% of UV is not transmitted through glass. The starters are not generally used as sufficient voltage is applied to ionise the argon and start the lamp.

What is meant by low and medium pressure lamps?

There are three types of UV lamps that are used for water treatment applications.

  • Low pressure – lowintensity
  • Low pressure – mediumintensity
  • Medium pressure – high

Each of these systems has a different UV energy level and water treatment application criteria. To answer this question a more detailed description of each of the lamp types is necessary.

Low Pressure – Low Intensity Lamp

This is by far the most common type of UV lamp used. The term “low pressure” signifies the pressure of mercury vapour in the lamp, which is typically 10-2 torr. The term “intensity” refers to the lamp power.

A standard low pressure – low intensity lamp has an output power of approximately 65 watts.

By using a quartz envelope that has been engineered to block shorter wavelengths (185nm), these low pressure lamps will essentially emit UV light at 253.7nm, which is near the peak for disinfection efficiency. However, the quartz casing of these lamps can be engineered to produce a higher UV intensity at approximately 185nm, which is more efficient for photo- oxidation reactions.

With low pressure lamps approximately 85-90% of the energy is at 253.7nm, however the energy per lamp is quite low. Therefore, most installations require multiple lamps to be used  to obtain the required UV dose.

Low Pressure – Medium Intensity Lamps

Low pressure – medium intensity lamps are relatively new and have approximately double the lamp output as compared to low pressure – low intensity lamps. These use the same basic lamp as the low intensity systems, but the power supply ballast is modified to achieve up to 170watts per lamp. The number of lamps used is not half that would be required for low intensity equipment, because the UV-C germicidal efficiency is lower. The intensity reduction at 253.7nm is approximately 15%.

Low pressure lamps operate at very mild temperatures, being 40 to 50°C.

Medium Pressure, High Intensity Lamps

The term medium pressure, as with the low pressure systems refers to pressure of mercury in the lamp, which is typically 103 torr. As can be seen this is far higher than that of a low pressure lamp, which enables far higher output power per lamp. For example, a 5000watt medium pressure lamp would be less than half the length of a 65watt low pressure lamp.

Medium Pressure Lamps emit UV radiation at all wavelengths, although is concentrated in select peaks throughout the germicidal wavelength regent. Of the total light emissions from these lamps, up to 44% of the total energy is in the germicidal wavelength range.

The most significant advantage of medium pressure lamps is that the high emitted UV energy enables a single lamp to provide up to 80 times the UV dose as compared to low pressure lamps. Also, medium pressure lamps can provide a high transmitted UV energy in the lower wavelength range (185nm) thus enhancing photo-oxidation reactions.

To obtain these results and emit high UV energy, medium pressure lamps operate between 600 and 800°C.

What are the advantages of Medium Pressure UV Treatment Systems?

The most important benefit of medium pressure lamps is the high UV energy output that can be provided from a single lamp.

For many applications multiple low pressure lamps must be used to achieve satisfactory results, particularly where a high UV dose is required, such as TOC reduction.

While it is correct to say that low pressure lamps may be manufactured to produce a higher proportion of their UV energy at specific wavelengths e.g. 254 and 185nm, at between 65 and 160 watts per lamp there are several drawbacks as far as their practical application. These include;

  • where large numbers of lamps are required, the installation space and cost can be significant
  • if the water source produces scale or fouling of the lamps, then cleaning of the quartz sleeve can be a substantial maintenance cost

Although medium pressure lamps operate over a broader UV spectrum, the available radiated energy is many times that of low pressure lamps. Although for a given application the power consumption will most likely be higher, the other benefits such as equipment simplicity, small foot print, low installation cost and lower maintenance costs far outweigh the difference in power costs.

Generally speaking, for poor quality water sources medium pressure technology is far more viable and economical with large flow rates (1,000m3/h+).it can be gained from the first rule of UV disinfection,

UV dose = average germicidal intensity (Iave) within the reactor X retention time

Generally speaking, with medium pressure systems a higher average germicidal UV intensity is achieved when delivering any particular UV dose. The higher Iave can be accompanied by shorter retention time (RT) to produce the required UV dose. This means shorter and fewer lamps for a given flow rate rate of water.

For clean water systems, such as swimming pools, the transmissivity is in excess of 95%. In these cases a single medium pressure lamp is capable of achieving both disinfection and photo-oxidation to relatively high water flows (800m3/h)

What are the performance differences between low and medium pressure lamps?

Low pressure lamps emit essentially monochromatic UV light at a wavelength of 253.7nm in the germicidal region (200-300nm). Of the total light emission from low pressure lamps, approximately 88% of the output is at 253.7nm, which is used for disinfection and ozone destruction. As mentioned above, low pressure lamps can also be engineered to provided a higher percentage of their output at approximately 185nm which is a wavelength used more for photo-oxidation reactions.

Medium pressure lamps are polychromatic with UV emissions at all wavelengths, although concentrating in specific peaks. Depending on the mercury charge and power density, between 27-44% of the total energy from a medium pressure lamp is in the germicidal wavelength range. Medium pressure lamps typically used for disinfection emit up to 80 times the germicidal energy compared to low pressure lamps.

The strongest energy peaks for an MP lamp occurs at 254nm, and 265nm although significant energy is still emitted from 160 – 450nm. With the higher radiated energy capability of these lamps one can easily see why medium pressure lamps are able to achieve excellent disinfection and photo-oxidation work, with fewer lamp numbers.

Conventional LP lamps have optimum operating temperatures of around 40-50°C, whereby MP lamps operate at between 600-800°C. Although the surface temperature of the quartz sleeves surrounding MP lamps remains at the temperature of the process water, the higher operating lamp temperature allows these lamps to operate at their optimum UV outputs independently of fluctuations in water temperature. Therefore the lamp output is determined  by lamp current, which enables the lamp output to be manually or automatically varied to control the UV dose. As a result, the UV output intensity of MP lamps can be modulated to delivery the required usage dose even though the UV demand of the fluid fluctuates. This is achieved with LP lamps by turning lamps on or off.

Because the retention time in the UV chamber becomes very short for a medium pressure system, the hydraulic design of the chamber is critical. The design must ensuring that an even UV dose is applied to the entire body of water passing through the treatment chamber.

The Ionics Watertec vortex system is designed to optimise mixing and prevent short circuiting in the chamber.

 

What is meant by water transmissivity?

As the name implies transmissivity is the amount of UV light that is transmitted through a specific depth of water. In other words it is a measurement of the amount of UV that is absorbed by impurities in the water.

Transmissivity is measured by passing water through a 1cm test cell, which has UV light at 254nm pass through it. A UV discrete photosensitive diode measures the amount of UV light transmitted through the fluid and compared against a reference. Transmissivity is then determined in percentage. Obviously the higher the percentage the further UV will travel through the water.

What does The UV Dose Term “mWs/cm2really mean?

To gain a better understanding of this UV does rate terminology we should firstly break down the components of how it is derived.

Lamp Intensity

UV Lamps have an electrical power output, which is measured in watts (volts x amps). For any specific lamp, the lamp manufacturers will nominate the UV energy output, which is measured as UV watts. This output is then stated as µW/cm2 at 1 metre distance from the lamp (1 watt = 1000 microwatts).

Ultraviolet energy is emitted 360° from the lamp centre. Energy levels can therefore be calculated at radially known distances from the lamp.

Retention Time

The total volume of water passing through a contact chamber, while it is being exposed to UV radiation is measured in seconds. Individual chamber flow dynamics may create additional time.

Absorption Co-efficient

The ability of UV light radiation to be absorbed by suspended solids can be determined by a  coefficient. To determine the absorption coefficient, a typical water sample is placed in a 1cm quartz test cell. This is the measurement of transmissivity.

The retention time is the actual time that all particles in the water are directly in the radiated path from the lamp. One can see that the actual UV dose at the furthest point from the lamp is affected by the water transmissivity.

The surface area, at any given radial point from the lamp, is expressed as cm2. Therefore, the measurement mWs/cm2 is a mathematical calculation of the UV energy radiated from the lamp in a contact chamber.

Following are some common ways of expressing UV dose; 1 mWs/cm2 = 1000 µws/cm2 = 1 mJs/cm2

There are several recognised formulas for calculating the theoretical UV dose for any specific lamp and reaction chamber design.

How does UV Disinfect Water?

The destruction of micro-organisms peaks at a wavelength of 260nm, therefore both 254nm low pressure and medium pressure lamps, which have a substantial percentage of their energy at 254nm are effective for disinfection.

Proteins and DNA (deoxyribonucleic acid) readily absorb UV radiation energy.

At the correct wavelength, UV penetrates through the cell wall of cytoplasmic membrane, striking the DNA. Once the required amount of energy has been absorbed by the nucleic acids, the ability of the cell to reproduce has been affected to the stage where inactivation of the micro-organism occurs.

Specific micro-organisms require certain amounts of UV energy for their destruction. Ultraviolet equipment is designed to ensure 30mWs/cm2 at the end of lamp life, thus maintaining minimum dosage levels to effectively destroy micro-organisms.

UV is effective for a broad range of micro-organisms such as bacteria, yeast, mould, fungi, viruses etc. At practical dosages, UV is not effective on parasites such as cryptosporidium or giardia.

The dose of UV delivered within a UV reactor is the mathematical product of the average intensity of light within the reactor multiplied by the retention time of the water passing through the reactor. As discussed above, the UV dose is expressed as mWs/cm2.

Fecal coliforms require about 3.4 mWs/cm2 UV dose for each log of inactivated. Therefore a dose of 6.8 mWs/cm2 will inactive two log (99% of fecal coliforms). Specific micro-organisms require different doses of UV for effective inactivation, however, for all organisms of concern in general water treatment, the UV dose would not normally exceed 16 mWs/cm2. From the above comments, it becomes obvious that a dose of 30mWs/cm2 at the end of lamp life provides a considerable safety margin for effective disinfection.

How does the photo-oxidation process work?

When water (H2O) is exposed to enough UV energy, the water molecule is broken down resulting in the formation of hydroxyl free radicals (OH).

The formation of OH is only minor when UV is applied at normal disinfection doses, simply because there is insufficient energy. Low pressure lamps operating at 185nm are commonly used for photo-oxidation reactions. This is because at this wavelength the radiated energy is higher than at 254nm.

With medium pressure lamps the output is spread over the UV-C spectrum although the energy peaks play a major part in the formation of OH radicals and therefore photo-oxidation reactions.

Hydroxyl free radicals are very powerful oxidants and are responsible for photo-oxidation reactions. However, OH radicals are very unstable and therefore have a short half-life (microseconds). Even though the exposure time is low, significant chemical oxidation  reactions still occur.

With sufficient dose, UV is capable of destruction of chloramines, chlorine, ozone, organic carbon (TOC) but to name a few. The actual dose of UV required is dependent on the overall chemistry of the water, concentration of contaminants and final water quality desired.

Depending on the level of reduction of such contaminants a UV dose of several hundred mWs/cm2 may be required. Some examples are;

  • Reduction of chloramines in swimming pools – 60 to 200mWs/cm2
  • Deozonation – 90 mWs/cm2per mg/l ozone
  • TOC reduction – 300 to 400mWs/cm2

How is the UV dose varied?

To increase the UV dose you can either increase the retention time, increase the UV output of the lamp or a combination of both.

For a specific system design, the easiest way to increase the UV dose is to simply increase the contact time, by reducing the flow rate through the reaction chamber. For example, a system is designed for a water flow of 200m3/h at a UV dose of 30mWs/cm2. If the flow is reduced to 100m3/h, the UV dose is increased to 60mWs/cm2 .

The output of medium pressure lamps may be varied by changing lamp voltage, which decreases the lamp current therefore the UV output of the lamp.

There is a limit as to the minimum output a medium pressure lamp. The problem is that if the temperature drops too far, the mercury begins to condense which is very detrimental to the operating life of the lamp. As a guide, the lamp should not be turned down by more than 50%.

What is the expected life of UV lamps?

The UV intensity of all mercury lamps decreases over time due to solarization. Solarization is  a photo-chemical alteration of the lamp envelope, the rate of degradation of which is a factor of the amount of energy that is absorbed. Therefore, the life expectancy of a low pressure lamp is considerably longer than a medium pressure lamp.

The normal life expectancy of a low pressure lamp is between 8000 and 12000 operating hours, whereby a medium pressure lamp will be between 2000 and 4000 hours.

The end of lamp life is considered to be when the UV intensity is reduced by 30% from the new lamp intensity. Therefore, all UV dose calculations are based on providing the minimum UV dose at the end of lamp life.

Do quartz sleeves need replacing?

Eventually the quartz sleeves suffer the same fate as the mercury lamps, being the UV transmission efficiency through the quartz gradually deteriorates. A new quartz sleeve will pass between 90-95% of the radiated UV energy.

Experience has shown that the quartz sleeve of medium pressure lamps should be replaced every 16000 operating hours, however this will be less if the quartz sleeve is physically damaged by the action of a wiping system.

Is fouling of the quartz sleeve a problem?

Any deposit or coating on the quartz sleeve that reduces the UV light transmittance into the water will effect the performance of the treatment process.

This deposition can be a simple coating such as oil or a bio-film, or may be a chemical coating such as calcium carbonate, which could precipitate out of the water due to the elevated skin temperatures on the quartz sleeve.

Therefore it is critical that the quartz sleeves are maintained in a clean state, which if needed, may be achieved by using either the mechanical wiping system or the wiping system used in conjunction with the chemical cleaning option.

With very pure water systems, such as ultrapure water, a wiping system is not required. However, for applications where the water quality is lower, such as wastewater, many processed waters, and in some cases swimming pools, a wiping system is justified.

For a swimming pool that has a high bather load, and uses UV in conjunction with chlorine, the quartz sleeve can be deposited with oils or fats. Therefore a manual wiping system should be incorporated.

When should I include a quartz sleeve wiping system?

As detailed above, all water sources, which have the potential for depositing contaminants, should either have an automatic or manual wiping system. Alternatively, the quartz sleeves must be removed and cleaned on a regular basis.

For applications where the contaminant loading is low, such as swimming pools, a manual wiping system will be adequate. In this application the plant personnel could operate the manual wiping system once per day. If preferred by the client, this of course may be automated using the pneumatic wiping option.

The main areas where a wiping system would not be required are for very pure water sources, such as ultrapure water, high quality potable water and high quality water used in the pharmaceutical industry.

If there is any doubt as to whether a fouling problem may exist, it is always a good idea to include a manual wiping system, as this may be automated at a later stage.

When should I use a quartz sleeve chemical cleaning system?

The intention of the chemical cleaning system is to chemically assist the manual wiping technique. The chemical used to will depend on the actual contaminant.

Some examples of contaminants and cleaning solutions are;

  • Dilute sulphuric acid may be used for precipitated scales, such as calcium carbonate. In this instance the acid dissolves any small scale deposit, leaving the quartz sleeve
  • For oil or fat contamination, the wiping system may simply smear contaminant on the quartz sleeve and not actually remove it. In this instance the cleaning solution could be a surfactant, a caustic cleaning solution or a detergent

The choice of cleaning solution will of course depend on the actual contaminant and the acceptability of introducing a small quantity of the cleaning solution into the main body of water.

What are some viable applications for medium pressure UV systems?

Although high energy UV systems may be used for virtually all water sources, the specific application, which should be initially considered, are;

 

Swimming pools The use of UV for pools should primarily be for photo- oxidation reactions and be designed and optimised to control chloramines.
Ultrapure water Medium pressure UV is now being used and is very viable for TOC control and disinfection of ultrapure water. This is a very worthwhile market, particularly considering that the Ionics companies use a significant amount of UV for this application.
Ozone Destruction UV is very effective for removing ozone residuals and producing hydroxyl free radicals, thus providing advanced oxidation. Therefore, the use of ozone and UV for enhanced slip stream ozone systems of swimming pools is a worthwhile technology.

 

Other applications for which medium pressure UV technology is appropriate include;

  • Disinfection and legionella control in coolingtowers
  • Disinfection of the various processwaters
  • Disinfection and photo-oxidation inaquaculture
  • Disinfection inhydroponics
  • Disinfection of municipalwastewater
  • Disinfection of feedwater for ion exchange beds and membrane filtrationsystems
  • Micro-organism control in photographic processingfluids

How to I select correct Ionics Watertec UV Model?

A. Swimming Pools

For swimming pools the minimum UV dose should be 60mWs/cm2. To optimise photo- oxidation reactions this UV dose should be higher, 120mWs/cm2 being ideal.

One should be aware that disinfection is not a prime requirement of a supplementary treatment such as UV. The normal chlorine residuals are adequate to control disinfection, therefore the main aim of the UV is for oxidation of chloramines. This process is optimised at higher UV dose rates with the quantity of UV needed being directly related to the bather, and therefore contaminant loading. What this means is that the treatment may be improved by treating a percentage of the filtered water, at a higher UV dose.

For a normal indoor heated pool, the best approach would be to install a UV system to 50% of the flow with a dose of 120mWs/cm2.

For selection of the equipment, the standard models are based on a UV dose of 30mWs/cm2 with a UV transmissivity of 99%. The transmissivity in a well run pool will be in the order of 95- 98%, therefore the flow rates shown in our documentation are applicable.

To increase the UV dose to 60mWs/cm2, the nominated flow rate would need to be halved. Therefore, a model MPV300, which has a nominal flow rate of 400m3/h, would be suitable for  a water flow of 200m3/h. If this model was to be used at 120mWs/cm2, the flow would be 100 m3/h.

There are no problems with excessive heat as the UV dose is increased, as the water has more than adequate flow to remove the heat dissipated from the quartz lamp and sleeve.

If higher UV doses are selected, the inlet and outlet connection sizes should be modified to accommodate the designed flow rate.

Generally speaking, for an indoor heated pool, the equipment should be sized for the full filtered water flow at 60mWs/cm2 and incorporate a manual wiping system with an option for wiping automation.

With swimming pools there is little benefit in automating the system so that the UV output is modulated. If a specification has called for this, the advantages are, that the average power consumption is reduced and the lamp life will be extended by some 20-30%, however the power savings are small.

B. Ultrapure Water

For TOC control of ultrapure water, the UV dose needs to be 300-400mWs/cm2, which is approximately 10 times the disinfection level.

Because the actual contact time and geometry of the chamber becomes far more important, the standard models cannot be used. As one can appreciate, if we reduce the flow rate through the standard models to 10% of the nominated flow, the pipe size and hydraulic characteristics will be wrong. For TOC reduction, the vessel diameters and inlet and outlet connections must be reduced, however the vessel lengths will need to be relatively long to accommodate the larger kW lamps.

For TOC reduction wiping systems are not required due to the high quality of the water. Also, the transmissivity of ultrapure water will be 100%.

Due to the high energy involved, automation of the lamp power is a desirable feature. Also, any extension of the lamp life is worthwhile for these applications. Therefore, the power automation system should be included, if possible.

When should I include light traps?

High intensity UV light will degrade many plastics and other non-metallic components. Therefore, if the UV unit is connected to a pipework system where the light emitted is in the direct line of sight of materials that are degraded by UV, light traps are required. Light traps are simple elbows or ‘S’ bends designed to shield downstream components from the UV light.

What materials may be used with UV?

Materials that are generally resistant to UV, that are normally used in water systems include;

  • Stainlesssteel – Viton
  • Silicon -EPDM
  • PDVF -PTFE
  • Glass -Quartz

Any other materials should be treated with caution and investigations made as to its suitability for UV.

What are some typical UV dose rates for different applications?

The following UV dose rates are a guide based on practical experience of some industries.

Disinfection – 30-40mWs/cm2 Ultrapure Water TOC Reduction  – 300-400mWs/cm2

Ozone Destruction – 90mWs/ cm2 per mg/l of ozone

Swimming Pools – 60-120mWs/cm2

Please note that these dose rates are all based on a water with a transmissivity of better than 95%.

How do I determine the UV transmissivity of the water sample?

Most analytical laboratories have the facility for measuring UV transmissivity. The instrument needed is basically a spectrophotometer, although it must be set up for monitoring UV transmittance.

Most water analytical laboratories can perform this test, however one such company is Simmons and Bristow, in Brisbane, who will undertake a transmissivity test for a cost of $8-$10.

If there is any doubt as to the quality of the water, then a UV transmissivity test must be done before sizing UV equipment.

What are the maintenance requirements of UV systems?

One of the real advantages of a medium pressure UV system is that the maintenance is both simple and minimal.

The following maintenance requirements and frequency are generally applicable.

MAINTENANCE OPERATING HOURS
Replacement of mercury lamp 2000 – 4000
Replacement of quartz sleeve 16000
Replacement of wiper ‘O’ rings 16000*
Replacement of quartz sleeve ‘O’ rings 16000
Remove & clean UV monitor sensor 8000

 

*The frequency of servicing the wiper system is dependent on the operating frequency of the wiper.

What are the operating costs of the UV system?

The operating costs are obviously associated with power. The power nominated in the model information is the actual lamp energy. Therefore, a 5kW lamp will draw 5kW from the supply when operated at full capacity.

If an automation system is incorporated then the power consumed will be determined by the average turndown used.

What do I need to know to quote a UV system?

As with most water treatment processes, some specific information must be known to enable a quotation to be prepared. For a medium pressure UV system the following is important.

  • Maximum instantaneous water flow to betreated
  • The minimum and maximum watertemperature
  • A chemical analysis, if available. In particular the TDS, pH and calcium hardness level are important
  • What is the treatment objective? (e.g. disinfection, TOC reduction)
  • What level of contaminant reduction is required, particularly for TOCreduction?
  • What contaminants in the water are likely to form deposits or fouling of the quartz sleeve?

How do I determine the UV dose for a given water quality and UV equipment model?

There is proprietary UV dose calculation information packages that are used throughout the world. Most of these are not available on the open market, however a document published by the United States Environmental Protection Agency is. This is a user manual for UV system design.

Using these UV dose calculations, the UV treatment system may be tailor designed to satisfy a specific UV dose, taking into account such facts as water transmissivity.

The above questions cover most of general aspects associated with UV treatment technology, which is an in depth and complex subject. This document is designed to provide a base level of knowledge to enable sensible assessment of the more common applications for UV and an understanding the overall technology.

 

CHAMBER

Material: 316 SS, Electropolished to Ra 15 Finish

Welding Specification: Full welds, ground smooth Maximum Water Temperature: 80°C – Continuous Maximum Pressure: 5 Bar 75psi continuous

Number of UV arc tubes: One medium pressure arc tube

Number of Water Seals: One (one on each end)

UV Monitor: Yes, w/4-20 mA output

Drain/Vent: ¾ inch screw plug

CONTROL/POWER CABINET

Climate Conditions:  Min 0ºC Max 35ºC (non condensing humidity)

Cabinet: IP32 Epoxy Coated Carbon Steel – Special Weather Proofing to Order

Input Voltage: 380 to 480 Volt. 50/60Hz

Current Protection: Re-settable circuit breakers for incoming supply & full earth leakage protection on lamp supply circuit

Temperature Sensor: Yes, with fail-safe shutdown/alarm as standard

Lamp Interconnection Cable: Cable length to be specified at time of quotation – Max 15 meters

Controller: PLC

Operational Features:

Remote Stop/Start terminals (voltage free circuit), Switch Remote/Off/Local, Sensor Cables 10m Std 15m Maximum

Lamps 2.5kW 3.5kW up Alarm Outputs 2.5kW 3.5kW up
UV Lamp Operate UV Dose Low
Water Temp High Lamp Failure
Lamp Fail Water Temp High
UV Dose Low Transformer Temp High
Transformer Temp High System Operating
Choke Temp High System Shut Alarm
Wiper in Operation (if fitted)
Power

 

Screen Displays:

Percentage, hours run, and temperature etc

External Contacts:

4-20mA signals for UV dose and intensity plus volt-free outputs for ten status indicators

Options:

  • Manual or automatic quartz sleeve wipersystems
  • Data logging providing retrievable data on operations over 12 months using RS232interface
  • Dose related, microprocessor controlled, variable power output to arc tubes with status indication (3.5wup)
  • LightTraps
  • Strainers
  • ChemicalWipery
  • Manual or Automatic UV intensity monitor and sensorlamp

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