The operating principles of the Halbach Array Magnetic Ring water treatment are based on four essential methods of action: Halbach Rare Earth magnetic array; interaction of the induced magnetic field with colloidal particles; control of microbial populations; and corrosion control. Magnetic array works by changing how calcium carbonate and other dissolved minerals precipitate from solution. The Halbach arrays activate colloidal nucleation sites in the bulk solution. These activated sites become the preferential nucleation sites for precipitation from a calcite to an aragonite crystalline structure. The amorphous precipitate, generated, does not adhere to the pipe wall but remains with the bulk solution and is removed via blowdown and/or side-stream filtration. Side stream filtration with centrifugal separator is preferred method.
The systems use colloidal science instead of inorganic chemistry to control scale.
Magnetic system is a bacteriostatic product rather than a true bactericide. Although the bacteria are not killed, they are controlled through two mechanisms. The first relates to the well-established effect in water treatment that coagulation, nutrient/trace mineral sequestration, and calcium carbonate precipitation will result in a microbial reduction. The second mechanism involves sub-lethal injury from the field (believed to be secondary to disruption in ion channels in bacteria cell walls and membranes), that controls bacteria even when there is no precipitation occurring.
Corrosion inhibition is accomplished indirectly by maintaining sufficient cycles of concentration to force the system into the alkaline mode at the saturation point of calcium carbonate, which is a cathodic corrosion inhibitor. In this type of water system, the expected corrosion rate on mild steel is 2 to 5 mils per year (mpy). The Cooling Technology Institute Guideline WTP-130 lists corrosion rates in cooling towers on mild steel of 2 to 5 mpy as “good” and 0 to 2 mpy as “excellent”. In many municipal water systems, phosphates or silicates are used as corrosion inhibitors to meet EPA’s copper/lead requirements. Where these systems are cycled up, the corrosion rate on mild steel is typically less than 2.0 mpy.
EXISTING SYSTEMS- Changing from Chemicals to Hydroflux
After stable operation of the evaporative loop is assured transition to Magnetic treatment is fairly simple: Turn off any chemicals being used. The conductivity set point will need to be monitored and set based on makeup water chemistry. Check frequently for the first month and adjust conductivity up or down as required to achieve the proper cycles of concentration as measured by chloride. After 1-month of stable operation, start monthly tests for bacteria.
If there is a significant amount of existing scale in the system, there will be a period of time where this preexisting scale will start to fall out of the fill and/or dislodge from the pipes and heat exchangers. During the descaling period, it is important to inspect strainers and the hot deck of the tower frequently and clean if necessary. This process can take several weeks to complete. The system is getting cleaner and more efficient.
Very low cycles of concentration or soft water can result in higher than normal corrosion rates. Our testing shows that the Magnetic System provides corrosion protection in most cases by allowing users to use calcium carbonate as a natural corrosion inhibitor. Unfortunately some waters do not allow proper sealing films to develop and protect metal surfaces. In some instances, one might have to use environmentally friendly corrosion inhibitors to supplement the magnetic water treatment. Operation with a lower than design heat load also has the effect of not ramping up the calcium carbonate level to keep corrosion rate at acceptable level.
Typically we want to keep the total bacteria population of the cooling system very low. Normally the Total Heterotrophic Bacteria Count (TBC) in the bulk water as measured by Standard Methods 9215B or ASTM D6530 will not exceed the 10,000 CFU/mL (Colony Forming Units per milliliter). The Cooling Technology Institute recommends this limit as an indicator of good tower hygiene to prevent outbreaks of Legionella. It is not unusual to see total bacteria counts of less than1,000 CFU/mL. Bacteria testing should not begin until the system has been running for at least 4 consecutive weeks of stable operation.
The magnetic design is effective against existing and potential biofilm formation. As a result, after the unit has been in operation for several weeks, there should be no clear slimy feeling biofilm in the bottom of the tower basin. If there is much existing biofilm in the system upon startup the system water bacteria count can go much higher than 10,000 CFU/mL for 2-3 weeks while the biofilms break down and release more bacteria into the water. After the system cleans itself the bacterial levels in the system water should drop to normal levels below 10,000 CFU/mL.
Algae are rootless plants that require sunlight and minerals to grow. In typical cooling tower systems the algae form a symbiotic relationship with the bacteria normally found in the cooling tower. After only a few weeks of operation the preexisting algae in the system will die. This is normal due to the ability to keep the bacteria count very low. This takes away a very important source of food for the algae. The algae are shocked by this sudden removal of bacteria and biofilm and subsequently die. The algae might reappear if there is abundant light and a food source such as phosphate in the makeup water. Normally the algae will not cause any system related problems and can be considered only an aesthetic issue. If the heterotrophic plate count is under control, and if the algae are not interfering with tower performance, it may be simpler to let the algae remain until normal routine cleaning. Even so, there might be some conditions where an operator believes that no amount of algae can be tolerated. If this is the case, then the use of foam or floating balls to block light is the most environmentally friendly solution.
Legionella bacteria are present in virtually all raw water and is found in soil and in the air. The risk of human infection is related to many factors such as temperature, mist formation, likelihood of breathing the mist, individual immune system characteristics, and others. No matter how clean the tower is kept, there is always a real possibility of Legionella contamination, therefore testing for Legionella presence is recommended following guidelines published in "Legionellosis Guideline: Best Practices for Control of Legionella" by Cooling Technology Institute.
STAGNANT WATER ISSUES
When the water is not circulated through the entire system, several problems can result. These problems include localized corrosion, biofilm and scale formation. Differential oxygen cell corrosion results when water becomes stagnant. The dissolved oxygen levels throughout the system are no longer uniform due to non-circulation of the water. In addition, when oxygen levels drop in the stagnant zone, anaerobic sulfate reducing bacteria and multiply and cause Microbial Induced Corrosion (MIC). This will lead to accelerated corrosion in the chiller as noticed by formation of large Tubercular deposits. No water equals no water treatment; therefore, bacteria can no longer be successfully controlled.
DEPOSITS ON OUTSIDE OF FILL AND SCALE CHIPS
Because the water in the tower is full of minerals, anywhere it is allowed to evaporate to dryness will leave a scale deposit behind. Deposits on outside of fill and scale chips in the basin indicate improper water distribution. This allows water to evaporate to dryness and leave behind deposits that are visible on the outer fi ll. To correct, check for obstructions and broken nozzles in the hot water basin as well as proper flow to tower at all times. If pumps are cycled in such a manner that water flow rate is lower than recommended by the tower manufacturer, improper water distribution will result. Cyclic or weekend shutdown can also result in some chips being formed due to cyclic drying and wetting of the fill. Periodic flushing with design water flow can be used to reabsorb tower fill scale in some installations. Flush time is site specific.
Treatment system has a short term residual bacterial effect that will protect the system during a weekend shut down of up to 3 days providing the system was running at least 4 days prior to the shutdown to assure adequate water treatment and residual buildup.
SHUTTING DOWN AND STARTING CHILLERS OR HEAT EXCHANGERS
It is very important that when chillers or heat exchangers are taken off line, that water continues to circulate through them to fully cool off the equipment. Failure to do this can cause scale to form inside the heated equipment due to higher than normal temperatures of the water remaining inside the equipment.
When starting equipment it is important to start water flow first for several minutes to allow opportunity to flush out settled material and provide fresh treated water to the heat exchanger before heat is applied. This will help prevent formation of scale inside the heat exchanger.
1. BACTERIA CONTROL IN NON-EVAPORATIVE CLOSED LOOPS
A. The system can successfully control bacteria in non-evaporative closed loops. Because the water is not cycled up, it is not likely that the system will operate above saturation for calcium carbonate. Therefore, the use of corrosion inhibitors might be required.
B. For effective bacteria control, try to get as much recirculation as possible. If possible turn over system volume 3 times per hour.
C. If the unit is heavily fouled with biofilm, there will be a two to four week period of larger than normal bacteria counts due to breaking up of the biofilm. Large masses of biofilm can break loose and foul system strainers, but this will be a temporary condition only.
2. SCALE CONTROL FOR HOT WATER BOILERS
A. The array can provide scale control for Hot Water Boilers in single pass or recirculating systems.
B. Locate magnets on inlet side of boiler for protection against scaling of boiler.
C. Locate magnet rings on outlet side of boiler for maximum protection of plumbing and fixtures.
3. SPECIAL SCALE CONTROL IN INDUSTRIAL PROCESSES
A. The rings produce universal seed crystals that will prevent the formation of new scale and many times will also soften existing scale.
B. Each process is different so a trial application might be in order to prove if the system can produce the desired amount of scale control
4. ENHANCED FILTRATION
A. The units reduce Zeta Potential on colloidal solids so they tend to agglomerate or stick together. This makes the percolates larger and more massive so they fall out of solution or will easily be removed by filtration systems.
B. Most effective applications are ones where recirculation is present.
C. Be certain to place the rings on the discharge side of any pumps or inlet if laminar flow is assured; and provide several feet of pipe before the filter to allow for proper seed formation to occur.