طرق معالجة المياه(الغليان/التقطير/غشاء الضغط الاسموزى)

Water Treatment Methods
Boiling:
In an emergency, boiling is the best way to disinfect water that is unsafe because of the presence of protozoan parasites or bacteria.
If the water is cloudy, it should be filtered before boiling. Filters designed for use when camping, coffee filters, towels (paper or cotton), cheesecloth, or a cotton plug in a funnel are effective ways to filter cloudy water.
Place the water in a clean container and bring it to a full boil and continue boiling for at least 3 minutes (covering the container will help reduce evaporation). If you are more than 5,000 feet above sea level, you must increase the boiling time to at least 5 minutes (plus about a minute for every additional 1,000 feet). Boiled water should be kept covered while cooling.
The advantages of Boiling Water include:
Pathogens that might be lurking in your water will be killed if the water is boiled
long enough.
Boiling will also drive out some of the Volatile Organic Compounds (VOCs) that
might also be in the water. This method works well to make water that is
contaminated with living organisms safe to drink, but because of the
inconvenience, boiling is not routinely used to treat drinking water except
in emergencies.
The disadvantages of Boiling Water include:
Boiling should not be used when toxic metals, chemicals (lead, mercury, asbestos,
pesticides, solvents, etc.), or nitrates have contaminated the water.
Boiling may concentrate any harmful contaminants that do not vaporize as the
relatively pure water vapor boils off.
Energy is needed to boil the water

distillation:
In many ways, distillation is the reverse of boiling. To remove impurities from water by distillation, the water is usually boiled in a chamber causing water to vaporize, and the pure (or mostly pure) steam leaves the non volatile contaminants behind. The steam moves to a different part of the unit and is cooled until it condenses back into liquid water. The resulting distillate drips into a storage container.
Salts, sediment, metals - anything that won't boil or evaporate - remain in the distiller and must be removed. Volatile organic compounds (VOCs) are a good example of a contaminant that will evaporate and condense with the water vapor. A vapor trap, carbon filter, or other device must be used along with a distiller to ensure the more complete removal of contaminants.

The advantages of Distillation include:
A good distillation unit produces very pure water. This is one of
the few practical ways to remove nitrates, chloride, and other salts that carbon filtration can not remove.

Distillation also removes pathogens in the water, mostly by killing and leaving them behind when the water vapor evaporates. If the water is boiled, or heated just short of boiling, pathogens would also be killed.


As long as the distiller is kept clean and is working properly the high quality of treated water will be very consistent regardless of
the incoming water - no drop in quality over time.


No filter cartridges to replace, unless a carbon filter is used to remove volatile organic compounds.

The disadvantages of Distillation include:
Distillation takes time to purify the water, It can take two to five hours to make a gallon of distilled water.

Distillers uses electricity all the time the unit is operating
Distillers requires periodic cleaning of the boiler, condensation compartment, and storage tank.

Countertop Distillation is one of the more expensive home water treatment methods, using $0.25 to $0.35 of electrical energy per gallon of distilled water produced - depending on local electricity costs. The cost of ownership is high because you not only have the initial cost of the distillation unit to consider, but you also must pay for the electrical energy for each gallon of water produced. If it cost you $0.25 to distill each gallon, and you purified 10 gallons per week, you would pay $130 for your 520 gallons of distilled water each year.

Most home distillation units require electricity, and will not function in an emergency situation when electrical power is not available.

Reverse Osmosis (RO):

Water pressure is used to force water molecules through a membrane that has extremely tiny pores, leaving the larger contaminants behind. Purified water is collected from the "clean" side of the membrane, and water containing the concentrated contaminants is flushed down the drain from the "contaminated" side. The average RO system is a unit consisting of a sediment/chlorine pre filter, the reverse-osmosis membrane, a water storage tank, and an activated-carbon post filter. They cost from about $150 to over $1,500 for point of use systems.
The advantages of Reverse Osmosis include:
Reverse osmosis significantly reduces salt, most other inorganic material present in the water, and some organic compounds. With a quality carbon filter to remove any organic materials that get through the filter, the purity of the treated water approaches that produced by distillation.

Microscopic parasites (including viruses) are usually removed by properly functioning RO units, but any defect in the membrane would allow these organisms to flow undetected into the "filtered" water - they are not recommended for use on biologically unsafe water.

Though slower than a carbon or sediment water filter, RO systems can typically purify more water per day than distillers and are less expensive to operate and maintain.


Reverse Osmosis systems also do not use electricity, although because they require relatively high water pressure to operate, they may not work well in some emergency situations.


The disadvantages of Reverse Osmosis include:
Point of Use RO units make only a few gallons of treated water a day for drinking or cooking.

RO systems waste water. Two to four gallons of "waste" water are flushed down the drain for each gallon of filtered water produced.

Some pesticides, solvents and other volatile organic chemicals (VOCs) are not completely removed by RO. A good activated carbon post filter is recommended to reduce these contaminants.


Many conditions affect the RO membrane's efficiency in reducing the amount of contaminant in the water. These include the contaminant concentration, chemicalproperties of the contaminants, the membrane type and condition, and operating conditions (like pH, water temperature, and water pressure).

Although RO filters do not use electricity, they depend on a relatively high water pressure to force the water molecules through the membrane. In an emergency situation where water pressure has been lost, these systems will not function.
* However, if a high quality activated carbon filter is used for the post filter, it could probably be disconnected and used to siphon water through in an emergency to reduce many contaminants.

RO systems require maintenance. The pre and post filters and the reverse osmosis membranes must be changed according to the manufacturer's recommendation, and the storage tank must be cleaned periodically.

Damaged membranes are not easily detected, so it is hard to tell if the system is functioning normally and safely.

A reverse-osmosis system is a good treatment option for people who have unacceptably high levels of dissolved inorganic contaminants in their drinking water which can not be removed effectively or economically by other methods.

Water from shallow wells in agricultural areas that contains high nitrate levels is a good example of a situation where RO would make sense. Most people, however, who are using municipal water water that is subject to EPA regulations

usually have acceptably low levels of nitrates. Maximum nitrate levels should be able to be determined by requesting a water quality report from your local water provider.