Safe water and methods of purifying water

Collected by : Sayed Mohammad Naim KHALID

“Water, water everywhere and not a drop to drink,” as the old saying goes. A more apt statement for these times might be, “water, water everywhere, but is it safe to drink?” Sadly, in this day and age there are few, if any, places where the water is safe to drink without treating, no matter how pristine and inviting it may look.

Water in the wild often contains harmful microorganisms, bacteria and parasites that can cause a variety of ailments, such as giardia, dysentery, hepatitis, and hookworms. Luckily, however, there are many simple and diverse methods to purify water to make it safe for consumption.

Since 1990, 2 billion people have gained access to improved drinking water sources and 1.8 billion people have gained access to improved sanitation. However, worldwide, 780 million people still do not have access to improved water sources and an estimated 2.5 billion people — half of the developing world — lack access to adequate sanitation.

Eighty-eight percent (88%) of deaths due to diarrheal illness worldwide are attributable to unsafe water, inadequate sanitation, and poor hygiène.

hese diarrheal diseases (such as cholera) kill more children than AIDS, malaria, and measles combined, making diarrheal disease the second leading cause of death among children under five.

There are several methods which can be used as water purification methods. These methods may include very primative and developed ways. Since our focus is more purification and provision of safe and available water in the developing world. Therefore, 4 basic methods will be listed and briefly explained below :

1.     Separation method

2.     Chemical method

3.     Filteration methods

4.     Oxidation methods

1. SEPARATION: HEAT, LIGHT & GRAVITY

SEDIMENTATION gravitationally settles heavy suspended material. 

BOILING WATER for 15 to 20 minutes kills 99.9% of all living things and vaporizes most chemicals.  Minerals, metals, solids and the contamination from the cooking container become more concentrated.
DISTILLATION boils and recondenses the water, but many chemicals vaporize and recondense in concentration in the output water.  It is also expensive to boil & cool water.
ULTRAVIOLET LIGHT is a good bactericide, but has no residual kill, and works only in clearly filtered water.   Still in its infancy stage is a new technology involving super white light.

2. CHEMICALS METHODS

There are also several chemical purifiers on the market. Iodine comes in either liquid form, (which can be messy), or tablet form.

One to two tablets or drops will clear up a quart of water.  Shake your container and wait twenty minutes before drinking. Water treated with iodine will have a darker color and a bit of an unpleasant flavor.

It is possible to mask this flavor by adding a powdered drink mix, but be sure to wait the twenty minutes before adding it, as it will interfere with the iodine’s effectiveness.

Other chemical treatments to purify water that work similarly to iodine are chlorine tablets, potassium permanganate, or halazone tablets. You should be able to pick these up fairly cheaply at most outdoor stores.

You can even add a few drops of bleach in a pinch, though I wouldn’t recommend overusing this one. It is important when using chemical purification to make sure all surfaces have been decontaminated.

After waiting the twenty minutes, slightly unscrew the lid of your water bottle or container and rinse around the threads and lid. The nice thing about using tablets is the container is very small and portable and can be slipped into a pocket, a plus if you do not want to carry a stove or pot, or take the time to boil water. Chemical treatment can be done on the hoof with minimal stopping time.

CHLORINE is common, cheap, but extremely toxic.  It does not decrease physical or chemical contamination, it does     increase colesterol formations, is a carcinogen, amd causes heart disease. 

BROMINE, used in pools and spas, doesn't smell or taste as bad and doesn't kill bacteria very well. 

IODINE is not practical, and is mostly used by campers. 

HYDROGEN PEROXIDE kills bacteria with oxygen, is chemically made and is very toxic.  It is used in emergencies. 

SILVER is an effective bactericide but a cumulative poison which concentrates and doesn't evaporate. 

NONTOXIC ORGANIC ACIDS should be used with caution in large water plants only. 

LIME AND MILD ALKALINE AGENTS should also be used with caution only by large water plants, or only for laundry. 

NEUTRALIZING CHEMICALS react with the unwanted chemicals and produce outgases and a sediment, but levels of need vary. 

COAGULATION-FLOCCULATION adds chemicals which lump together suspended particles for filtration or separation. 

ION EXCHANGE exchanges sodium from salt for calcium or magnesium, using either glauconite (greensand), precipitated synthetic organic resins, or gel zeolite, thus softening the water.  Minerals, metals, chemicals or odors are not affected, and the water is salty to drink. 

3. FILTRATION

A third method of treatment is commercial filters. These come in all shapes, sizes and price ranges. Most work by pushing the water through a charcoal or ceramic filter and then chemically treating it. Normally, they have one hose with a float that goes from the water source to the filter and a second hose, for clean water, that goes from filter to water bottle. When using this type of filter it is important to not cross contaminate the hoses. Keep the clean hose in a separate plastic bag so it never touches the contaminated hose. The plus side to this method of how to purify water is that there is no flat or funky flavor. Commercial filters are also good for when the water is on the murky or dirty side, as they will remove this also. The drawback is that the sediment or tannins that you are filtering out will quickly clog up the filter. Some can be cleaned, with others you need to buy a replacement filter. Like all technical equipment, cost and breakage are things to be considered.

SLOW SAND of 1 cubic meter passes about 2 liters/min, and does a limited bacteria removal. 

PRESSURE SAND of 1 cubic meter passes about 40gpm and must be backwashed daily. 

DIATOMACEOUS EARTH removes small suspended particles at high  flow rates, must be daily backwashed and is expensive. 

POROUS STONE/CERAMIC filters are small but expensive, and do not effect chemicals, bacteria or odors. 

PAPER or CLOTH filters are disposable and filter to one micron, but do not have much capacity. 

CHARCOAL: 
     -COMPRESSED CHARCOAL/CARBON BLOCK is the best type of charcoal  filter, can remove chemicals and lead, but is easily clogged,  so  should be used with a sediment prefilter.
     -GRANULAR CHARCOAL is cheaper, but water can flow around the  granules without being treated.
     -POWDERED CHARCOAL is a very fine dust useful for spot cleaning  larger bodies of water, but is messy and can pass through some filters and be consumed.
REVERSE OSMOSIS uses a membrane with microscopic holes that require 4 to 8 times the volume of water processed to wash it in order to remove minerals and salt, but not necessarily chemicals and bacteria.

4. OXYDATION

AERATION sprays water into the air to raise the oxygen content, to break down odors, and to balance the dissolved gases.  However, it takes space, is expensive, and picks up contaminants from the air. 

OZONE is a very good bactericide, using highly charged oxygen molecules to kill microorganisms on contact, and to flocculate iron and manganese for post filtration and backwashing. 

ELECTRONIC PURIFICATION and DISSOLVED OXYGEN GENERATION creates super oxygenated water in a dissolved state that lowers the surface tension of the water and effectively treats all three types of contamination: physical, chemical and biological.