Last Updated on June 13, 2020 by Amit Abhishek
UV Sterilizer ( marine freshwater Sterilizer ) has widely used onboard ships as a disinfectant to treat drinking water produced from fresh water generator. Onboard ship Freshwater is used for the most part by huge boilers, running machinery, and crew every day.
It controls the spread of microorganisms in water by killing them or simply make them permanently inactive. Using UV light to sterilize water is a residue-free method to make water safe for drinking without making it taste awful or adding any odor.
Why Need To Treat Water Produced On Ship
On average, the crew consumes about 69 liters/day/person and in case of passenger ships, 222 liters/day/person. The ship takes only a minimum quantity of fresh water from the port for domestic services (since it is not allowed to use the freshwater generator in port).
The water so produced by a freshwater generator or stored in double bottom tanks are sterilized to avoid any unknown transfer/spread of micro-organism.
As jacket water used in the freshwater generators is only 70-75 degrees hot which are insufficient to kill all the germs and bacteria in the freshwater.
So it is mandatory to sterilize fresh water on board for human consumption.
Thus the water is purified and protected from the spread of microorganisms. In the process, UV-C rays are used to break the molecular bonds within the DNA of various microbial organisms like bacteria and viruses. Thus making them incapable of doing any harm to us.
The primary advantage of using U.V sterilization over other modes of water treatment is that; it’s cheap, environmentally safe, does not include any chemical and does not have any negative impact on the taste or smell of the water.
How Does UV Sterilizer Works?
UV Sterilization of potable water is a safe and reliable method of disinfecting it, this method causes photochemical reactions in the cells of micro-organisms, thus killing up to almost 100% of the bacteria and viruses.
UV purifier is known to kill major microbial contaminants causing disease including but not limited to; Beaver fever, Dysentery, Cholera, Typhoid fever, gastroenteritis, E.coli, Hepatitis, etc.
The UV rays have short wavelengths; it kills or inactivates microorganisms by destroying nucleic acid and disrupting their DNA. Thus making them impaired to perform important functions, like reproduction and damage to human beings. The wavelength of 260 nm–270 nm is termed as “Germicidal UV”.
The effectiveness of such a UV sterilization method depends on a number of factors such as; the size of the organism, power of UV light or Power of the bulb, UV penetration, and contact time. Other factors that indirectly affect the effectiveness of UV purifier working are flow rate and working temperature.
- Size of the organism: UV purifiers are best suited for microorganisms of small size such as protozoa, algae, virus, and bacteria. larger organisms such as complex multicellular organisms require a large dosage of UV rays. Thus they are better separated in advance using filtration technique.
- Amount of UV light: The larger is the UV light or power of the Uv bulb the better will be the effectiveness of the UV purifier or UV sterilization process. Thus sufficient capacity bulbs are selected for the capacity of water to be treated.
- UV Penetration: If the water is cloudy and dirty the UV light can not properly penetrate the water thus the effectiveness drops. The UV light can also not penetrate if the flow is turbulent. Thus cleanliness of the lamp and flow type matters.
- Contact Time: Also sometimes referred to as dwell time; it is the net time the water is exposed to the UV light. The length will be the exposure period or contact time the better will be the effectiveness of the purifier.
Why U.V sterilizer is preferred over other popular disinfectants?
U.V is preferred on board ship it is preferred above another disinfectant because of its supreme tendency to kill all kinds of germs. Under controlled and tidy conditions (regular maintenance) it gives its best results at an economical rate. But it requires clean water, free of small particles and minerals; To penetrate and disinfect radially which is always present on the ship.
On top of that UV water purifiers are safer to use. In fact, it is the most effective method of disinfecting drinking water. It’s chemical-free, taste, and odor-free requires less maintenance and investment. But on the contrary, it does not work satisfactorily where the water is too hard or cloudy.
Other factors responsible for using U.V over others are:
- It is a powerful disinfectant that kills a different variety of germs including bacteria, viruses, and parasites.
- It provides high-quality disinfection.
- There is no such problem as a reaction to pipes or corrosion.
- Have no effect on the taste and odor of water.
- They do not require any chemicals.
- Requires very little energy, as much as it is required to light 60watt bulb
- Low Maintenance, just changes the UV lamps bi-annually.
How long does it take for UV light to sterilize?
It takes just a millisecond to kill 98% of bacteria or few milliseconds to kill 99.99% of bacteria or other microorganisms present in the water. As the water passes through the ultraviolet light, it instantaneously impaired their growth disrupting their DNA to make them inactive.
Construction Features of Marine Freshwater UV Sterilizer
U.V sterilizer fitted on board ship have the following constructional properties:
- Ultra-Violet Sterilizer consists of a casing that has mirror-finished inside of it.
- Consist of two cleaning plug
- Return Block made up of Cast Iron.
- four Clamping Nut
- Two Quartozoid Glass tube
- Three UV lamps or Germicidal lamps.
- Drain plug at the bottom.
- Four Rubber gasket or O-Ring.
- Three Observation Window.
Maintenance of UV Sterilizer
Before carrying out maintenance, ensure that inlet valve and outlet valve to and from UV Sterilizer respectively is shut and the by-pass valve is open, so as not to interrupt the water supply
- Mirror finish inside of the casing should be cleaned to enable UV rays to reflect effectively.
- The UV lamp has an effective germ-killing life of 6 months, a book is maintained to monitor the replacing time.
- Use a wetted cloth to clean quartozoidal glass tube on the UV sterilizer.
- Do not disturb the glass tube unless required.
- Quartozoidal glass tube has O-ring around it and clamping nut is used to screw the tube.
Precaution to take
- Never to look at the UV lamp with naked eyes.
- Always close power supply when opening the cabinet.
- Don’t pressure too much when assembling the gland fittings.
- Take care while cleaning Quartozoidal glass, as they are very thin.
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