The heart of a ballast water treatment system is the disinfection stage. This is the part of the system that takes filtered seawater and sanitizes it to prevent the spread of microbes, microorganisms, and viruses that cannot otherwise be removed by a filter.
Selecting a Technology
Many people ask “which type of ballast water treatment system is right for my vessel?” While we will not presume to answer that question for you, there are four key things that you should consider when considering what type of disinfection stage you want to use:
- Do you want a system that has no limitations based on the salinity of the water you are trading in?
- Do you want to protect your crew from having to handle dangerous chemicals?
- Do you want to prevent generating explosive hydrogen gas during your ballasting process?
- Does your ship either go on short voyages where it is critical to be able to ballast and Deballast in the same day? In the same port? At the pier during cargo operations?
- Do you store ballast for long periods in some tanks, maybe for a year or longer?
If you answered yes to any of those questions you should definitely consider UV. If you answered yes to all of them – you should definitely select the Hyde GUARDIAN®
Medium Pressure UV versus Low Pressure UV
UV for disinfection is broken down into two different types of lamps: low pressure UV lamps and medium pressure UV lamps. While each gets their name based on pressure of the pressure of the gas inside the lamp, the primary difference between medium pressure and low pressure lamps relates to the spectrum of light being emitted by the lamp. Medium pressure UV systems emit a broad spectrum of UV disinfecting light, while low pressure UV lamps emit targeted light targeted to the “germicidal spectrum” of 254 nm
Low pressure UV systems typically have a lower power requirement and are more energy efficient, but due to the specific, targeted light output, they cannot penetrate far into the water and require many more lamps than a medium pressure UV system. Low pressure UV systems also operate at very low temperatures, which means that at lower seawater temperatures, they may have challenges starting and producing light at their peak efficiency.
Medium pressure UV lamps operate at a higher power level, but translate this higher power into water-penetrating intensity that reduces the number of lamps needed. This penetrating UV light also allows medium pressure UV systems to operate in waters with lower UV transmissivity (UV-T) than typical low pressure systems.
One final factor in selecting your UV system is that the broad spectrum medium pressure UV lamps have shown increased effectiveness both in meeting the U.S. Coast Guard’s testing methods for ballast water treatment systems, and they have a broader impact on organisms in the 10 – 50 micron size class. This means that the treatment system is not solely reliant on the filter to remove all of these organisms, but instead the disinfection stage can serve as a backstop when the filter starts to age.
Despite the power requirements, medium pressure UV light is still the most useful, balanced, effective, and environmentally sound method of disinfecting the water once it gets past the filter.
Keeping It Clean
Seawater is clean. Unfortunately, most ships do not ballast in the open ocean. You get ballast at the pier where local rivers, tides, runoff, and silt cloud the water and stain your equipment. As the water passes through the separation stage of a ballast water treatment system, some of the heavier, larger staining factors are removed, but most of them remain. And most of them end up all over the inside of your ballast water treatment system.
So what is the most effective way to clean a ballast water UV chamber? Hyde Marine has the experience and the installation base to know that automatic mechanical cleaning is always the best. Our proprietary wiper design automatically cleans all of the quartz sleeves across their entire effective area as well as cleaning the UV sensor window without interrupting ballast flow.
The use of a mechanical wiper has three key advantages over other types of cleaning:
- Cleaning can take place immediately, as the sleeve becomes clouded, rather than letting the stain build up until a cleaning cycle can be initiated
- With no chemicals and no need to flush the reactor, the cleaning cycle is automatic, seamless, and invisible to the crew
- Immediate, routine cleaning prevents the inevitable buildup of iron deposits that necessitate the disassembly of the reactor and hand-cleaning required when cleaning is put off too long
The Hyde Marine UV measurement circuit constantly monitors sleeve cleanliness and automatically initiates mechanical wipe cycles. Cycles are also timed regardless of the observed cleanliness to ensure that the system is always performing at its best. Five hundred installations after we first installed a mechanical wiping system on the M/V Coral Princess, mechanical, automatic cleaning is still the best way to ensure your sleeves are always ready to go.
Scaling or Stacking
The Hyde GUARDIAN was born out of the municipal drinking water industry. As a part of De Nora Water Technologies, we have experience treating flows into the millions of gallons per day in some of the largest cities in the world. You simply cannot treat water at those types of flow rates by stacking UV chambers on themselves like books on a shelf.
Hyde Marine has specifically designed each of our three UV chamber offerings with multiple configurations to match the GUARDIAN UV Chamber exactly to your ballast flows. We do not believe that putting reactors in series without individual flow meters and automatic flow regulating valves to balance flow between individual nodes will produce the repeatable, effective treatment that vessels need to prove compliance as a system begins to age.
Further, Hyde Marine has always recognized the critical nature of head loss through a ballast water treatment system. For retrofit applications, this is a particular concern because ballast pumps were likely designed without the increased head of a treatment system. Any increased head on the discharge of a centrifugal pump will result in decreased flow performance through that pump.
Enter the Hyde GUARDIAN UV chamber. With direct flow perpendicular to the lamp orientation and no restrictions to clear flow from the filter through the UV outlet valve, we have achieved the lowest head loss of any UV-based ballast water treatment system. Systems with individual, stacked reactors, introduce multiple pipe bends and redirections of flow with each direction change creating additional head loss. Whether you are looking to optimize the flow through your UV chamber or looking to tailor the precise flow delivered by your ballast pump to the precise capacity of a UV chamber, the Hyde GUARDIAN’s scaled UV chambers make the most sense for your vessel.
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