Ozone is a pale blue gas that consists of three oxygen atoms. There are many commercial and industrial uses for ozone including: disinfection of laundry in hospitals and health care facilities, disinfection of drinking water, sanitizer for swimming pools and spas and sanitizer for food industry. Ozone has been used for disinfecting drinking water since the late 1800's. It is used much more extensively for drinking water in Europe and Asia than in the United States.
There are many advantages for using ozone in drinking water treatment. First ozone is a powerful oxidizer and is more effective against bacteria and viruses than traditional chlorine. Ozone can easily kill protozoa such as Giardia and Cryptosporidium, which chlorine is ineffective against. In addition to its disinfection properties, ozone is also used to oxidize metals and inorganic compounds, so it is helpful in removing nuisance contaminants such as iron, manganese and sulfur. Ozone oxidizes the metal or inorganic into an insoluble form which then can be removed via mechanical filtration. The use of ozone also helps in eliminating taste and odor issues found in some drinking water supplies.
While ozone has many advantages over traditional methods of disinfection for potable water it also has some disadvantages as well. First, ozone can be expensive due to higher equipment cost and additional ongoing electrical costs. Ozone dissipates readily so it does not offer residual disinfection protection that chlorine and chloramine offer. The use of ozone may produce disinfection by-products, which may be of concern depending on the original make-up of the water. For example if bromide is naturally occurring in a water source, using ozone on that source would cause the formation of bromate which is considered a carcinogen by the EPA. Additionally there is also the risk of fire and toxicity associated with the generation of ozone.
Since ozone is a gas that cannot be stored or transported, it must be generated on site. There are three ways ozone can be generated: 1.) corona discharge 2.) ultraviolet light and 3.) cold plasma. Corona discharge is one of the most popular methods of generating ozone for most industrial and residential applications. Corona discharge involves passing oxygen containing gas through an electrical field. The electrical current causes a split in the oxygen molecule, the resulting oxygen atoms attach themselves to an oxygen molecule forming ozone. Ultraviolet light works very much like corona discharge. Ambient air is passed over an ultraviolet light which splits the oxygen molecule which ends in the formation of ozone. Cold plasma method is usually for ozone being used therapeutically. It utilizes an electrical field but feeds a pure oxygen rather than ambient air used in corona discharge. Back to the Top. . .
Reverse osmosis is one method of filtering drinking water. It is the movement of a solution, under pressure, through a membrane, to strain out impurities. Water often contains impurities, which may cause the water to look, taste, and smell or even feel unpleasant. Reverse osmosis helps to separate most impurities from the water. Many RO systems have the ability to remove 90-95 percent of dissolved solids from the source water.
The typical configuration of a reverse osmosis system is made up of a pre-filter, membrane, carbon post filter and sometimes a pressurized storage tank. The pre-filter is designed to filter larger particles and any debris that may come from the water source. This is very important since the membrane must stay free of large particles and debris so that the solution may pass through the membrane. Depending on the make-up of the water it may be necessary to additionally treat for nuisance contaminants such as hardness minerals, iron and manganese, which are better removed using ion-exchange prior to reverse osmosis. Large concentrations of those contaminants can cause a reverse osmosis system to prematurely fail. The membrane is the filtering device. This is the device which prohibits the passage of smaller particles, and allows the passage of the solution, water, to the next stage. The activated carbon filter is in the next stage and is designed to capture some smaller particles that may have passed through the membrane and absorb any volatile organics that may have passed through the membrane.
To understand how this process works we must first understand osmosis.
Osmosis is the movement of water or other solution through a semi-permeable membrane. The water or other solution will pass through the semi-permeable membrane but not the impurities. The movement of the water or solution will stop when the pressure on both sides of the membrane is the same. (Osmotic Pressure) This is the process by which our body's cells pass nutrients between each other. This is also the means by which plants get water from the soil, and filter out impurities from the soil.
As in other home filtration, Reverse Osmosis was first developed on an industrial scale to desalinate ocean water. The basic principal of Reverse Osmosis is the same as with Osmosis. The basic difference is that the water is being forced through the semi-permeable membrane under pressure. This pressure is greater than the Osmotic Pressure, so that there can be continuous flow of water.
Reverse Osmosis is a very effective method of filtration. Depending on the size of the pores of the membrane, RO (Reverse Osmosis) is used in many home and commercial applications. The down side of RO is that you must use more water than is ultimately filtered. For every gallon of filtered RO water you will lose approximately 4 gallons of water. Reverse Osmosis is an excellent way to remove most inorganic contaminants, however it is a system best utilized at point of use, due to the corrosive effect of pure water on household plumbing and faucet fixtures. Back to the Top. . .
Ultraviolet light is the light found on the electromagnetic spectrum between visible light and x-ray light. There are three segments of the electromagnetic spectrum, the near ultraviolet, far ultraviolet and extreme ultraviolet. These ranges are distinguished by their energy and by the wavelength which is related to energy. Ultraviolet light has wavelengths shorter than visible light and is considered a germicidal UV or invisible radiation. These short waves of light are what are used in the UV disinfection process which is used to kill or inactivate microorganisms.
Ultraviolet light is considered a safe and effective application for disinfecting drinking water from microorganisms. Ultraviolet light disinfects the water without the use of harsh chemicals such as chlorine and other disinfecting products which may form disinfection by-products. These disinfection by-products are a result of the chlorine or other disinfectants (chloramine, chlorine dioxide or ozone) reacting with naturally occurring organic matter. Some of the disinfection by-products are considered carcinogens or cancer-causing, so there is a struggle to provide water that is free of microbiological contaminants along with reduced levels of these potentially dangerous by-products.
Ultraviolet light is used to disable or kill microorganism such as bacteria, viruses, cysts, protozoa, yeast and molds. When these microorganisms come into contact with the ultraviolet light, the light passes through their outer shell and disrupts their DNA. The microorganisms become mutated and therefore can not reproduce. This renders these organisms inactive and they will inevitably die off.
Utraviolet disinfection systems consist of an ultraviolet light enclosed in a quartz sleeve which is usually enclosed in a stainless steel chamber. The source water flows through the quartz sleeve where the UV light is located exposing the contaminated water to radiation from the light. The effectiveness of the UV light is dependant on numerous factors such as the lamps intensity, proper wavelengths, exposure time, flow rate and the quality of the source water itself.
In order for the ultraviolet light application to perform at peak performance a water analysis should be performed prior to activation. This is an important step for UV application due to the ability of the bacteria, cysts, protozoa and all other microbes to hide behind any minerals or metals which may be in the water. Water with high turbidity or cloudiness can block the ultraviolet light which is necessary to destroy the bacteria. Additionally water with high levels of dissolved or suspended solids can hide or harbor the bacteria from the necessary amount of UV light needed for irradiation. Back to the Top. . .