Ah, that wonderful refreshing taste of a tall cold glass of water. Cooling, soothing and pure. But is it pure? What about all those invisible microbes and bacteria? What about all those pesticides and herbicides you don’t see? It’s enough to spoil that thirst-quenching moment.
So how do you get pure
drinking water? Most people get a water filtration system. However, no one unit can remove all the impurities in our drinking water. And there are many types to choose from. If you have a better understanding of how water filters work, then you’ll be able to get the right one to fit your lifestyle.
Water filters were invented for good taste – and safety
Water filtration systems have been sought since as early as 4000 B.C. to clear the visible cloudiness in drinking water. We humans have a penchant for purity, don’t we? Especially for something we’re putting inside our bodies! That desire for purity has grown in the last few decades, and has been joined by a desire, also, for safety.
We not only want the water that we drink to be pure, with good taste and odor, we also want to know that we have safe drinking water; that is, free of impurities like bacteria, poisonous chemicals and minerals. And as science discovers more of these in our water, we need to find systems that’ll filter them out. These impurities can be very harmful, causing diseases and malfunctions in our bodies. And since health is such an emphatic issue these days, we need to be making wise decisions about what we eat and drink.
These were the thoughts of Heinz Hankammer and his family as they produced a water filter that would provide, in a simple format, clear water – free from impurities. Heinz named his company after his daughter, Brita, which you’ll probably recognize as the leading manufacturer of freestanding household water filters today. Brita led the way in producing the simplest and most cost-effective way of improving water quality.
Water purification and filtration can be quite technical
We’re going to give you here, a simple explanation of how water filters work. We’ll look at the different types available, while trying to stay away from the technical terms so you’ll get a clear understanding. Remember, if you understand something, you’re far more likely to remember it.
Most filters today are charcoal, or activated charcoal. Charcoal, which is mostly carbon, is the residue of partial burning or destructive distillation of organic material. When special heating or chemical processing is added to charcoal, it becomes much more absorptive, and is then referred to as “activated charcoal”. So a charcoal filter works on the principle of absorption. Large volumes of gases, including most poisonous ones, stick to the charcoal, which is quite porous. (That’s why it’s used in gas masks.) Because it has such a large porous surface area, it absorbs a lot of impurities. Charcoal filters are used in icemaker filters, under-counter filters, countertop filters, whole-house filters, and more. You get the message – charcoal really “takes out the garbage”.
Another type of water filtration system available today is reverse osmosis. That’s the technical name for the process of water being pushed through an ultra-fine semi-permeable membrane, where it separates the tap liquid into the pure permeate which is diverted to a storage tank for later use; the brine concentrate is diverted down the drain. The water is stored in a pressure tank and is treated to a final activated-charcoal polishing filtration stage to remove all remaining odors and tastes before dispensing the purified water into your glass. The disadvantage of reverse osmosis systems is that they waste a lot of water – for every gallon of purified water produced, two gallons are wasted.
Other types of water filters are ion exchange and distillation. Ion exchange is designed to remove dissolved salts in the water, such as calcium. This system actually softens the water or exchanges natural-forming mineral ions in the water with its own ions, thereby neutralizing their harmful effect of creating scale build-up. The ion exchange system was originally used in boilers and other industrial situations before becoming popular in home purifying units, which combine the system with carbon.
Distillation is the simple process of boiling water to create steam. The steam cools and condenses to form pure mineral-free water droplets which are deposited in a container. When combined with carbon, the result is 99.9% pure contaminate-free water. These systems are extremely efficient and reliable, and are regarded today as one of the most effective ways to remove contaminates from any water, from any source.
One other water filter worth mentioning is the portable variety. If you do a lot of camping or hiking, these are the wise choice for you.
A summary of filtration systems and what they do and don’t do:
Activated Carbon Filters – Do: absorb organic contaminants that cause bad taste and odor; some models remove chlorination byproducts; some models remove cleaning solvents and pesticides. Don’t: remove metals such as lead and copper; remove nitrate, bacteria or dissolved minerals.
Ion Exchange Units – Do: remove minerals, particularly calcium and magnesium that make water “hard”; remove fluorides; some models remove radium and barium. Don’t: soften water if it has oxidized iron or iron bacteria, which clogs the system when the ion-exchange resin becomes coated.
Reverse Osmosis Units – Do: remove nitrates, sodium, other dissolved inorganic and organic compounds; remove foul tastes, smells or colors; possibly reduce the level of some pesticides, dioxins and chloroform and petrochemicals. Don’t: remove all inorganic and organic contaminants.
Distillation Units – Do: remove nitrates, bacteria, sodium, hardness, dissolved solids, most organic compounds, heavy metals, and radionuclides; kill bacteria. Don’t: remove some volatile organ contaminants, certain pesticides and volatile solvents; stop bacteria from recolonizing on the cooling coils during inactive periods.
转自：http://www.howitworks.net/how-water-filters-work.html
