There are approximately 2,000,000 water treatment devices being sold in Canada and the USA each year. There are a number of methods available to improve or enhance drinking water quality. Many of the proven technologies are commonly used to effectively reduce specific contaminants in drinking water. POU devices are those that take cold water from a source line, treat it via one or more means of technology and then supply it to a dedicated outlet. A Point of Entry [POE] system is one that treats all the incoming water to the home, but will be specific to what it is "treating" the water for ( hardness, iron, chlorine etc.).
Simplistic, cheap, one technology filters are a fad that has resulted from the public becoming aware of the problem but are not educated in the true solutions. Advertising can sell anything to anybody regardless of their true needs. Good quality equipment that employs multiple technologies, is thoroughly tested and is guaranteed not to be cheap. Good quality equipment is generally more expensive at the time of initial purchase, but the difference in "life" of quality systems compared to "cheap" mini systems is dramatic. If you calculate the overall cost per gallon of a mini cartridge system or one of the "disposable" systems, you will find that a tested and certified system is actually cheaper in the long haul. The volume of high quality equipment sold is still low, therefore production costs remain very high and subsequently the initial cost of qualify systems remains high, but compared to the alternative of bottled water, quality, certified systems are cheap.
The following is a basic description of some of the common technologies found in the market place today.
Particulate filters can consist of foam, felt, cloth, woven fibre, paper, compacted charcoal, string, your old socks and so on. The "filtering" media is only limited by the imaginations of man. The one steady fact about them is that all quality filters are rated to a specific micron size. This can range from less than 1 to 1000 microns depending on what they were designed to filter. As an example, a 50 micron filter will trap particles larger than 50 microns. This aids the purchaser in determining the correct unit for the job at hand. If you purchase a unit with too small a rating, for use on water with high sediment levels, it will quickly clog. Particulate filters of various micron size fill an important role as "pre-filters" to almost every quality POU system on the market today. They take the "burden" off of other more expensive components in these systems and therefore save the consumer money in the long run.
The tiny pores of a ceramic filter element make it an extremely efficient filter for the removal of particulate matter and fine sediment from the influent product water. This is known as mechanical depth filtration. This type of filtration is extremely effective in the removal of contaminants such as asbestos fibres. Minute fibres will quickly plug paper style filters, but the ceramics have the added benefit of being cleanable and re-useable. Additionally ceramic candles with micron ratings between 1 and .45 micron also qualify as a certified product for the disinfection water which may be contaminated with bacteria. This particular sub-micron rating allows for the physical removal of bacteria and cysts giving them a "bacteriologically sterile" rating. High quality candles will contain silver that is impregnated throughout the ceramic wall to prevent the growth of the bacteria within the pores of the ceramic thereby ensuring that they meet the standard of being "bacteriostatic" also known as "mitosis".
SUB-MICRON MESH FILTERS
Man has duplicated the efficiency of ceramic with a woven nylon mesh. The qualities of such are identical to the ceramic with the exception that the nylon is expensive and does not have the "cleanable" characteristic associated with ceramic.
ADSORPTION FILTERS
The most common media for the adsorption of contaminants found in drinking water are Granular Activated Carbon [GAC] and KDF. These media reduce common tastes and odors, some turbidity, residual chlorine, radon and many organic and inorganic contaminants with varying degrees of efficiency based on molecular structure and most importantly equipment design. The most common design is a cartridge containing a media "bed". Water flows through the media bed and contaminants "adhere" to the surface area of the media. Remember the "chemical magnet" description. This will be discussed in greater detail later.
This is the end of "filters". We will now look closely at three other technologies, but you will see that even these will employ the virtues of the filtering technologies just mentioned.
Distillation has historically been known to be most effective in producing contaminant free water. As with other point-of-use (POU) and point-of-entry (POE) technologies, design is a major factor in producing a highly effective unit. In general, the energy input required for distillation involves a higher operating expense than other methods and the maintenance factor is extremely high.
Distillation systems duplicate nature's hydrologic cycle producing high quality water essentially pollution free. Water is first boiled in a chamber which creates steam that rises and leaves virtually all contaminants behind in the boiling chamber. Steam is then collected and condensed into clean, distilled water. Impurities remain in the boiling chamber and are either automatically or manually flushed out depending on the system.
Contaminants that boil at less than or close to the same temperature as water are the Volatile Organic Contaminants [VOC's] and are a challenge for some distillers. A quality system must have a vent in the condensing coil to release the VOC's prior to vaporization of the water. These systems ensure that the VOC's are not carried over with the steam and condensed with the distilled water. These features are not found on cheap distillers.
Quality distillation systems use particulate and adsorption filters as standard features. Pre-filters are used before the distiller to reduce the levels of sediment introduced into the boiling chamber thereby helping to lower the maintenance of the unit and GAC post-filters are employed to ensure that any chemicals carried over in the process are further reduced. The post filters will also enhance the taste and reduce odors from a storage medium if used.
Most residential distillation units use either air cooled or water cooled condensers. The air cooled units offer more advantages and have historically been more popular because of their lack of wasted water, fewer service problems and ease of installation and operation. Air cooled systems produce virtually one gallon of distilled water for every gallon of tap water. Water cooled units produce one gallon of distilled water from eight to fifteen gallons of tap water. The costs of producing a gallon of distilled water range anywhere from 20 to 40 cents per gallon because they use about three kilowatt hours of electricity to produce one gallon of water and electrical costs vary in difference parts of the country.
WHAT IS IT? - A technology based on nature's own purification process:
We realize that distillation has a rather long list of disadvantages, but it must be realized that for all its faults it is still the "best" technology available. All other systems and technologies may come close to distillation but none surpass. For most areas and water conditions, going to the extremes of distillation is not necessary and very costly. Newer technologies work faster, cheaper, longer, etc. but they don't work better. Distillation will always have a place in the POU industry.
As this is a popular technology today and somewhat confusing to most we will look at it in depth. Osmosis is a natural process in which a fluid passes through a membrane from a higher concentration to a lower concentration. For example, a prune will dry in the sun as the moisture passes through the skin from its moist interior to the drier atmosphere outside. Placing a dried prune in a pan of hot water causes the water to pass, again by osmosis, into the sugar solution of the prune, swelling it. The concentration difference acts like a pressure difference to cause a flow through the prune membrane.
Reverse osmosis is a separation process in which a semipermeable membrane "filters" dissolves solids. Pressure is used, in addition to the concentration difference, to cause a flow through the membrane, when pressure causes a flow opposite to the natural osmosis flow, the process is called reverse osmosis. While the osmotic pressure causes dilution, reverse osmosis uses pressure to separate and concentrate.
Reverse osmosis [RO] is known as the "high tech" method for reduction of dissolved inorganic contaminants and higher molecular weight organic contaminants. Osmosis does not remove soluble organic chemical contaminants of low molecular weight. The performance of any RO is based on the type of semipermeable membrane used in the unit; cellulose acetate and polyamide types are currently the most commonly used. A system normally consists of a particulate pre-filter followed by a RO membrane and then followed by an activated carbon cartridge, a water reservoir containing a pressurized rubber bladder, an optional activated carbon cartridge and finally a dedicated faucet at the sink. Household under-sink models operate efficiently at pressures that range between 40 and 70 psi on non-brackish waters up to 2,000 mg total dissolved solids. Top quality systems also employ electronic meters that will automatically stop the flow of water if the membrane is damaged. These monitoring systems are built into tiny LED's at the base of the systems faucet.
Cheap counter-top RO systems are just that. They produce very little water in a 24 hour period, the water must be stored somewhere and as the act of osmosis is in itself not effective on chemical contaminants. The benefits of such systems are few.
If high quality pre and post filters are not used, the water will have strange tastes and be of unknown quality. The inability to detect holes in the membrane leaves the consumer in a state of complete unknowing. These cheap devices are not for use on rural supplies or in RV's.
WHAT IS IT? - Technology is based upon a multiple component concept:
Ultra-violet treatment offers the user disinfection without chemicals. Therefore no taste, odor or harmful secondary chemical by-products are produced in the water itself. Other attractive features are minimal maintenance, ease of installation and competitive costs.
Ultra-violet [UV] as used in an UV system is not carcinogenic or dangerous to the consumer of the water in any way. The UV bulb in an ultra-violet disinfection unit is completely enclosed within that unit. The electrical system in an UV system is no more complicated to understand than the fluorescent lights in an office and are as trouble free as an electric bulb.
A complex quality UV system will begin with a low micron pre-filter, as it is essential that the water going through the UV chamber be as free as possible from particulate matter and sediment. Bacteria must not be allowed to "hide" behind common dirt, it must be fully exposed to the UV rays to be killed.
A good ultra-violet system will have monitoring devices to let the user know when it is not working properly. These may consist of: a flow control device, a signal or shut down device, a narrow band metering system with an alarm to indicate any increased levels of bacteria in the water and UV bulb indicator that lets you know when the bulb is burnt out or not working.
Adsorption filters will be employed for the reduction of toxic organic and inorganic contaminants once again. UV light has no effect on chemicals.
UV POU systems are overkill of technology in municipal systems. The organism threat is well contained by municipal disinfection so the efficiency of the system is dependent on the quality of its pre and post filters which are not normally the focus point of the manufacture.
Stand alone UV exposure chambers are excellent in the rural community as POE devices to safeguard against an organism outbreak. They are not however effective on cysts.
WHAT IS IT?- A technology using ultra-violet rays to disinfect water, consisting of:
Although this is predominately a POE system for rural water supplies and we are focusing on POU. The application of POU technology to households that already have water softening or iron reduction POE equipment is a very significant percentage of the total market place, so an understanding is required.
Most all household water softening equipment now on the market today uses the ion exchange principle. As the water passes through a bed of ion exchange material, the hardness minerals are removed, leaving the water soft. Calcium and magnesium ions are exchanged for sodium ions. Thus, water containing the ions of calcium bicarbonate when it enters the bed of the exchanger, will contain the ions of sodium bicarbonate when it leaves the exchanger bed.
De-ionization or de-mineralization is another ion exchange process that is used to remove the mineral and trace element content from the water for laboratory and other specialized uses. There are basically two forms of ion exchange: cation, which is used in water softening applications and anion exchange which is primarily used for the removal of very heavy metals and nitrates.
WHAT IS IT?- A technology that makes use of an cation or anion exchange process:
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