Tech Face-Off Part 1
SPRING 2000 FACE-OFF
ULTRAVIOLET LIGHT TECHNOLOGY
IN THE MANAGEMENT OF METALWORKING FLUIDS
ULTRAVIOLET RADIATION Fundamental to the management of metalworking fluids is control of the microbe growth in the fluid. One technology that is effective in the destruction of microbes is ultraviolet light, or UV. UV is electromagnetic radiation in the range of approximately 4 to 400 nanometers. The range of UV radiation is further divided into UV-A (315-400nm), UV-B (280-315nm), and UV-C (15-280nm). The shorter wavelengths, such as those found in UV-C, are known to be particularly deadly to bacteria and viruses and for this reason are commonly used for sterilization.
PHOTODEGRADATION The process by which UV damages cells is photodegradation. This is similar to what happens to your skin in the sun. The photodegradation of microbes from exposure to short-wave UV primarily occurs through cell wall destruction.
OXIDATION-REDUCTION UV can be used to generate ozone, or O3. Ozone destroys microbes, and is commonly used in municipal water facilities to disinfect city water systems. Ozone also destroys the cell membrane, and is generally a faster killer of microbes than photodegradation alone, although this is system-condition dependant.
PHOTOLYSIS An additional microbe killing mechanism for which UV can be used is called photolysis. This is accomplished by addition of selective oxidative agents to a solution and irradiating the solution with ultraviolet radiation. Exposure of the oxidizing agent in the solution to the wavelengths of ultraviolet radiation results in the photolysis of the oxidizing agent into hydroxyl free radicals (OH·). The hydroxyl free radicals aggressively attack the organic constituents of the solution. This process is inappropriate for recycling systems.
METALWORKING FLUID MAGAZINE would like to thank Bill Bettag and John Coogan for their informed participation in our interviews. We chose Coolant Wizard and Triton Thalassic Technologies, because we believe they are the highest quality manufacturers of this type of equipment in the world. While the technology used by these two companies has a similar foundation, there are vast differences in applications and the equipment. To that extent, they are not in competition with each other, and in fact, have a friendly professional relationship. By interviewing them together, we can answer the tough questions that ANYBODY with metalworking fluid might ask. UV technology is the best non-chemical means of extending the life of metalworking fluid, when combined with the necessary mechanical filtration and separation technology. Send your follow-up questions to either Coolant Wizard or Triton Thalassic Technologies at these links:
Interview with John Coogan, PhD
Triton Thalassic Technologies, Inc.
Interview with Bill Bettag
President of Coolant Wizard, Inc.
Q1. How is the UV managed so that the system kills bacteria while preserving the integrity of the organic compounds essential to metalworking fluid performance?
Triton Thalassic Technologies’ monochromatic UV lamp maximizes photobiology and minimizes photochemistry by using a non-oxidizing, but germicidal, UV wavelength. Photochemical processing is target specific to efficiently deliver light energy to microorganisms. This can be contrasted with an oxidation process, which would attack any organic material (bacteria, lubricants, etc.)
Q2. By virtue of this issue, (and others?) which class of metalworking fluids are the best to treat in this manner, and which are the most difficult (and why)?
Unlike other systems using UV that have attempted to treat MWFs, the FASTAC ( Fluid Application Specific Treatment and Control) system is not a modified water treatment system, but a unit designed specifically for operation with coolants and the rigors of plant operation. FASTAC is effective for soluble, semi-synthetic and synthetic fluids. The size and performance of the unit is dependent on the optical properties of the fluid and the general level of housekeeping at the subject facility. While there is no requirement that the fluid is filtered, or tramp oil removed, a well-maintained system will require a smaller scale UV system
Q3. Is the development of this technology (and more particularly, exposure durations) based on known biochemical reaction rates or generally empirically developed? Are critical species of bacteria targeted in any of this? (i.e., Mycobacterium chelonae, -abscessus, E. coli, etc?)
The mode of action for UV is not specific to a particular species of bacteria or fungus. UV controls the full range of microbial contamination found in MWF. The use of UV to disinfect fluids and surfaces is well characterized and wastewater and drinking water is routinely treated using ultraviolet lamps. The doses required to remove E.coli, mycobacteria, or psuedomonas are well characterized – the challenge for the treatment of MWFs is the efficient delivery of this dose within an opaque fluid. The use of a proprietary design (patents have been granted for both the light source and the reactor) allows FASTAC to efficiently deliver this dose to a large volume of fluid, without degrading the value added compounds that allow the fluid to lubricate and inhibit corrosion.
Q4. Please distinguish the differences between ozone and UV treatment of wastewater, drinking water, and metalworking fluids.
Ozone is used to disinfect cooling tower water and drinking water. Both of these applications use water with low organic content which limits the available targets for oxidation by the ozone. What organic material is present (biomass or chemical contamination) is undesirable so any collateral damage to this material is helpful. In MWF, there is a very high loading of organic material, added to the coolant for a specific function, which will be attacked by ozone.
Q6. Please discuss the problems associated with ground level ozone and ultraviolet light generated by these systems and how these issues are managed.
Standard UV systems used to treat water can produce ozone, additionally, exposure to the light from intense UV sources is dangerous. For this reason all UV treatment systems should be interlocked to prevent operation in the air. The lamps used in T3I’s FASTAC system are permanently enclosed in pipes so there is no risk of worker exposure to UV. In addition the wavelength of the lamp is designed to minimize chemical interactions and so it does not produce ozone.
Q7. What effect does the system have on the total organic carbon in the fluid? How does this effect the life of the recycled coolant?
Biocides force the micro-ecology of MWFs into an artificial and unstable condition, which makes the fluid vulnerable to colonization by opportunistic pathogens. T3I’s FASTAC unit maintains the stable, naturally occurring mixed-population of indigenous organisms at a level that eliminates odors and extends fluid life but leaves no room in the fluid ecosystem for the introduction of a non-indigenous pathogen like mycobacteria. By maintaining this ecology, minimizing or eliminating biocides, the coolant will see a longer more productive lifespan.
Q8. Do you manufacture a system that addresses the management of the metal fines in the solution and tanks in combination with UV treatment?
The FASTAC UV system is engineered to reduce bacterial and fungal levels (measured as CFU/mL) by 90 to 99.99% depending on the customer’s specifications. The resulting CFU/mL is therefore dependent on both the scale of the UV equipment and the plant specific environment – type of fluid, pH, water source, housekeeping all effect the growth rate of microorganisms. The removal of metal fines and tramp oil, important processes for reconditioning fluids, does help reduce the growth of microorganisms, but does not kill bacteria or fungus. Therefore, while the FASTAC unit does not require any special filtration to operate, a cleaner system will be maintained at a lower CFU/mL.
Q9. What are the maintenance requirements for a typical system and the cause of the requirement (cleaning, etc.)?
The T3I FASTAC requires very little maintenance. The maintenance required includes the semi-annual inspection of the lamps, and a re-charge of the CIP (Clean In Place) system.
Q10. Are systems batch processing or continuous? What is the smallest system that can be built? (To handle what volume of fluid?)
Since bacteria are living organisms, and always growing, any control technology will work best if applied continuously. The Triton FASTAC system is designed to process the fluid in this fashion. Current systems treat MWF volumes of 1,000 to 50,000 gallons. Larger volumes of process or rinse water can be processed as well.
Q11: Last question - just for fun :). What is your opinion of the equipment and systems of Coolant Wizard? Be candid. Is it junk? Do you hate them? Are they even a competitor? With a cost difference of tens of thousands of dollars, why buy a Trinton system instead of Coolant Wizard system?
As you know, our technology is completely different from Coolant Wizard's and our market is completely different also. In that respect we really don't compete with each other, in fact we really compliment each other within the markets and potential customers we approach although the sales decision makers we approach and work with are also different from Coolant Wizard's.
Q1: What are the limitations of ozonation when applied to control biological growth in metalworking fluids?
Really the biggest hurdle is when the colony is allowed to grow in size so that either a very large ozone generator (read expensive) is needed or nearly continuous application is required. Planned management, as opposed to crisis management, is the answer to this problem. We have not found a bacterium that can resist the deadly affect of ozone. Bacteria, fungus, molds, cysts and yeast cannot develop a rsistance or immunity to ozone as they can do to biocides and fungicides. Tests at Indianan University have proven this fact as information supporting the statement that coolant quality is not jeopardized by ozone application.
Q2: If a centrifuge system is utilized to complement the Coolant Wizard, how will the mixing action of the centrifugal system affect the performance of the Coolant Wizard?
The bacteria colony size will determine the effectiveness of the application of dissolved ozone. When the colony is nearly out of control, long applications of ozone will be needed. Cyclonic treatment, including centrifuging will homogenize the tramp oil and the coolant. The opacity of this homogenized fluid causes ozone accessibility problems when ozone is applied directly to the fluid. Advances are being made to solve this problem, but they are costly to implement. Dissolved ozone does not seem to be affected by the opacity of the fluid to any degree.
Q3: Triton states that they use a non-oxidizing, but germicidal, UV wavelength, since they believe that the ozone is too aggressive, and non-discriminatory with regards to what it attacks, including organic material added to the coolant for a specific function. How do you respond to this, and why is ozone generation superior?
It is true that UV waves applied to coolant will degrade the emulsion when applied directly to the fluid. This fact is old news. The Independent Lubricant Manufacturers Association in their booklet "Waste Minimization and Wastewater Treatment of Metalworking Fluids" states that ".heat treatment, or oxidization by ultra-violet, radioactive or high-energy irradiation can cause undesirable coolant chemistry changes." Coolant Wizard doesn't do this. We generate ozone with the on-board generator and then bubble dissolved ozone into the fluid. This process looks similar to the bubbles you would see in a well managed aquarium. The fluid never sees the UV in our system. This is the same approach used to apply ozone in hot tubs to control bacterial growth. Triton has developed a way to apply the UV to the fluid without the resulting degradation but it is considerably more expensive to do this. As to which is more effective; both applications get the job done. The difference is in the customer's requirements. While you can eat soup with a shovel, it isn't the appropriate tool for the application you have.
Q4: How is the UV managed so that the system kills bacteria while preserving the integrity of the organic compounds essential to metalworking fluid performance?
Again, dissolved ozone is not harmful to coolants. This was proven in tests completed at Indiana University in 1998-1999 and, better yet, by the 250 Coolant Wizard owners.
Q5: How do the optical properties of the fluid effect performance of the coolant wizard?
Because ozone is applied by dissolving it into the coolant, optical properties are not a factor. The ozone "bubbles" don't care whether they are in a clear or opaque fluid as long as they can move through it.
Q6: Please discuss the problems associated with ground level ozone generated by UV systems and how these issues are managed.
If I understand correctly, you are asking about ozone off-gas. An independent laboratory was called to our facility to investigate this in 1998. With a Coolant Wizard Junior filled with city tap water and operating for 3 hours prior to the test, no ozone was detected farther than 3 inches from the fluid level in the cart. We used the Junior because it has a smaller tank, it uses the same ozone generator as the larger cart and we used water because coolant will use up more ozone than water. In other words, a worst case situation.
Q7: Any plans to compete in the stationary recycling system market?
Coolant Wizard is, and always has been, geared to the small to medium size shop applications. Granted, we have systems in very large companies but they are where logistically or economically a central system is out of the question. There are also Coolant Wizard systems in facilities where they are required to use one coolant product for some applications and another product for others
Q8: Is Coolant Wizard ever going to offer complimentary portable recycling equipment? When and what?
We have support products available such as mist collectors, refractometers, bio test products to check on bacteria / fungus growth and pH testers. Other than these products, no. We try to stay focused on the products we have that reduce coolant use. We have talked of an even smaller system where one or two machining centers are involved, but it is still on the drawing board.
Q8: In the opinion of Coolant Wizard, which is generally better for removing the solids in coolant; centrifuging, cyclonic separation, or filtration?
Any material that is heavier than the fluid can be removed by either centrifuges or cyclone systems. Media filtration requires buying and disposing of the media and, depending on the system and the volume of contaminates, can be costly. The first obstacle to overcome is getting to all of the recesses and corners of a sump so that the majority of the solids are addressed. This is applicable to both centrifuging and cyclonic methods. The optimum solution is a sump with sloped sides that allow the solids to gravitate to a single pick-up point. This is most often not possible without the coolant being circulated to a separate holding/separating tank. It therefore seems better to address the gross contaminates before they can settle to the bottom of the sump. Magnetic separation or deep bed filtration wins the prize here.
Q10 : Last question - just for fun :) What is your opinion of the equipment of Triton's systems? Be candid. Is it junk? Do you hate them? Are they even a competitor? Besides a cost difference of tens of thousands of dollars, why buy a Coolant Wizard instead of a stationary system such as made by Triton?
I have had conversations with the folks at Triton and they are knowledgeable and anxious to assist those willing to consider an innovative approach to coolant management. To compare their systems to the Coolant Wizard line is similar to comparing a Ford Mustang to an 18 wheel semi-trailer. They are both good products but they have completely different applications. This is good because customers have different needs. Triton has a product line that will fill the needs of those with central sumps containing thousands of gallons of coolant. Their equipment would not be appropriate for the shop with 10 to 50 machines with 40 to 150 gallon individual sumps