Pireka. Water treatment filters

ABOUT WATER

Water, like atmospheric air is essential and indispensable source of life. People use water all the age and its quality often effects their health. No other product in the world has so rigid quality control standards as drinking water has. 

Water is a good solvent and contains many substances dissolved in it as well as undissolved and colloidal particles. Chemical composition of water its pollution and mineralization depends on hydrogeological conditions, rocks it lies in and filters through. Furthermore, improper economic activity of people has a negative effect on surface and ground waters: pouring of uncleaned sewage into ground waters, uncared dumps (Lithuania has more than one thousand dumps), etc.

In Lithuania only ground waters are used for central water supply, they are retrieved from seven horizons that have water. The explored water sources suitable for exploiting make about 2 million m³ per 24 hours, but at the moment only 25 per cent of the sources are used in the country.

The most common water problems and their solutions are described below.

Water is hard because of calcium and magnesium salts that are dissolved in it. They do not have a direct negative effect on human health, but bathing in such water makes the skin dry and hair coarse, household equipment maybe harmed and it is more complicated to take care of it. 

The effects of hard water:

• pipelines, bathroom facilities and other plumbing equipment are covered with lime;
• kettles, irons and boilers are covered with white sediments that are hard to remove;
• white laundry gets yellow and the colour clothes fade out, the clothes are worn faster;
• food cooked in hard water looses part of nourishing qualities.

Advantages of soft water:

• soap makes more foam, less shampoo or cleanser is needed, hair becomes soft and shining, protective layer of the skin remains unharmed;
• clothes washed in soft water look more new, are softer and are worn in a longer period of time;
• water heating expenses are reduced;
• pipelines and household equipment have no lime sediment.

Water softening systems eliminate the mentioned shortcomings of hard water. Their basis is the filtering media which is made of high capacity ion exchange resin. The resin joins Ca and Mg ions that are in the water and gives harmless sodium ions. When the resin’s capacity is used up, it is restored with a specially prepared solution of clean salt. Ca and Mg ions that had accumulated during that time are cleaned out to sewerage and are replaced by sodium. That is why the filtering media can serve for many years unchanged.

  

The average amount of iron that Lithuanian water supply wells contain is 1–2 mg/l. In 75% of all water tests iron concentration reached from 0,2 to 2,0 mg/l. According to hygiene norms the quality of water is considered to be very good if concentration of iron is less than 0,2 mg/l.

If water looks clear it does not mean it has no iron. Two-valent iron is dissolved in water and cannot be seen by naked eye. But if the water is left in an open vessel for some time, sediments appear.

Increased amounts of iron are indicated by:

• brown spots on a bath, a sink or a lavatory as well as inside walls of dishes and kettles;
• metal taste of water;
• brown or yellow stains on the laundry;
• brown sediments, that occur in carafes or other vessels water is kept in;
• brown sediments on pressure gauges as well as valves and bolts which get clogged and cannot be closed tightly;
• brown water running from a tap if water was not used for a longer period of time.

Iron removal filters with a special media covered with oxidating components effectively solve these problems. Iron is removed from water through oxidation and filtration. Iron that is dissolved in water is oxidated at the surface of the media and from two-valent iron that dissolves in water turns into undissolved three-valent iron hydroxide, the sediments of which are hold up in the filter media. Sediments that accumulate in the media are regularly washed out into the sewerage.

 

Concentration of manganese in Lithuanian water supply wells reaches up to 0,5 mg/l. It is higher than quality norms allow in more than 40% of water used in Lithuania. Manganese develops in ground waters in a natural way, i.e. when water flows and dissolves rocks that have manganese.

Increased amounts of manganese can be recognized by the following indications:

• water and drinks that are made of it (tea, coffee) have a bitter taste;
• inside walls of pipelines are covered with colour that damages laundry;
• kettles and pots get brown or black tint;
• brown or black water runs when the tap is opened if it was not used for a longer period of time;
• drops of water leave brown spots on a bath, a sink or a lavatory.

Manganese is removed from water in the same way as iron. But manganese is more difficult to oxidate and needs two – three times more of oxidating media.

 

If a glass of water is hold in the light, a lot of small particles can be seen in it. Various undissolved organic substances can cause water turbidity: clay, sand, rust, sediments of manganese, silicon, sulphur, etc.

Sediment removal filters is the most effective turbid water purification means in most cases. If the particles are very small, coagulation may be necessary to induce formation of dregs. The dregs are effectively removed by filtering water through an appropriate sand media.

 

The smell and taste of water depends on various admixtures present in it. 

The most common are smells of a decaying egg and chlorinated water.

The smell of a decaying egg is caused by sulphur hydrogen. Its presence can be detected by the following signs:

• water has unpleasant taste;
• silver dishes get black;
• steel and copper pipes get covered with rust.

If concentration of sulphur hydrogen is not big, oxidating filters can be used or aerated water can be filtered through sand filter. If the concentration is big, strong oxidating substances are necessary, such as chlorine or potassium permanganate.

Smells and admixtures can be removed by chlorinating (disinfecting) water. A lot of microorganisms are killed this way. However, big doses of chlorine worsen smell and taste of water. Remains of chlorine can be eliminated by filtering water through activated carbon media or by intensive aeration.

 

About 2,7 million residents of our country get water from centralized water supply. The rest one million residents supply themselves with water individually from shallow wells, the number of which comes to about 300 thousand. The ground horizon with water that is feeding wells is the closest to the earth surface and most sensitive to pollution. The main problems of well water quality are nitrates and microbiological contamination. Nitrates and nitrites form in soil by oxidation of organic and non-organic nitrogen combinations and most often accumulate in surface layers of soil. The main reason of their formation is soil fertilization with organic fertilizers, uncleaned sewage, poured on the ground and pits of waste.

In this case drinking water preparation system with reverse osmosis membrane is most effective. The system removes from water nitrates and most of heavy metals, poisonous organic and chemical combinations. The water cleaned this way is safe to use.