The concepts of “water quality” vary according to the purposes of water use. Up to 300 mg of chloride per liter which is a measure of the salinity of the water and if they are indeed suitable for drinking purposes but certainly not for the purpose of watering orchards for example. Water containing 800 mg of chloride is simply not suitable for human consumption, but can certainly be irrigated. Water that contains 2,000 mg of chloride is intended for cooling the power stations, but certainly not for drinking and / or irrigation purposes.

The Water Pollution Act “A change in the properties of water… physically, biologically, bacteriologically, radioactively or otherwise, which causes water to be dangerous to the public, or may harm animals or plants, or be less suitable for the purpose for which it was intended” (1959).

“Pure” water – a concept that does not exist: in nature, water falls as rain and adsorbs substances that exist in the air on the way to the ground, such as soot, gases, dust, salts and smog. In a meeting with the soil, other substances are present in the water.

Therefore water is divided into 2 groups:

Solid suspended solids: A solid substance that is not dissolved in water such as soot, sand and residues of organic matter.

Water that contains large amounts of suspended solids has a cloudy appearance, as particles absorb some of the sun’s radiation that damages the water.
The dissolved substances: A solution formed from different substances that come in contact with the water in the solution. The substances separate into ions that are at intervals between the water molecules, so that the dispersion of molecules of dissolved substances and the water molecules makes them clear. Such as oxygen, carbon dioxide and cooking salt that form solutions. The properties of the substances cause their level of solubility.

Small oxygen solubility of carbon dioxide.

Water quality: Determined by the number of types of substances added to the water, the concentrations and the reactions to the other substances.

Physical Indices:

Temperature: A major effect on any biological process that takes place in water. As the temperature rises, the oxygen concentrations dissolved in the water decrease, and the rate of metabolism in living organisms increases, thus increasing their rate of culture and growth.

Thermal Pollution: Changing the water temperature due to human activities such as power stations and various industries where water is used for cooling purposes and later the same water is returned to the same source from which it was pumped hotter and with scale built up as a result of water heating.
The ambient temperature rises and affects all creatures. The substances in the water can undergo a chemical process and produce harmful side conditions.


Turbidity: The solids that float in water such as clay, organic matter, algae and waste are the causes of turbidity.

Cloudy water actually indicates high concentrations of all solids. The high turbidity actually prevents the free passage of light rays and hence the rate of photosynthesis of the algae decreases and hence the oxygen concentrations. The carbon dioxide concentrations also increase. Thus many creatures that live in water are harmed.

Color: Evidence of the presence of the various substances, some of which pollute the water, such as the presence of ions of metals and / or substances that are emitted from the various algae and change the color of the water.

The chemical indices are expressed in the concentration of various substances present in water, such as salts, nitrates, phosphorus and oxygen. As salinity, salt dissolved in water is an ion with an electric charge. The salt that is most common in water is the cooking salt and hence the chloride (chlorine ion concentrations) is used as a test meter for the salt concentrations.

The origin of the salts in the water is mainly from the dissolution of the salts in the soil and also in the rocks that come in contact with the water. The salinity value varies depending on the composition of the soil, the composition of the rocks and the amounts of water in the area at a water source that is close to the sea.

The constant and appropriate salinity is what helps all living things to maintain a proper balance of salts in the body. If the salinity changes, the balance is damaged and the water is not suitable for drinking at all. The degree of salinity in the irrigation water actually determines the type of crop that is irrigated.

Nitrates and phosphorylation: are formed in water reservoirs in a natural process during the nitrogen and phosphorus recycling process and they join the water bodies also in surface runoff such as the leaves, carcasses, remnants of cowsheds and poultry, municipal waste, ash from forest fires, and dust emitted from volcanoes.

  • Phosphorus also exists in detergents that are dissolved in water.

  • High nitrate concentrations endanger drinking water.

  • Eatropification: Chains of procedure caused by high concentrations of nitrates and phosphorylation as a result of excess nutrients in the water.


Step 1: The increased reproduction of the algae i.e. algae blooms, which start with the consumption of nutrients.
Step 2: Amounts of nutrient that is reduced due to increased consumption or cessation of flow and onset of algae death.
Step 3: Dead algae constitute the food for the joints and therefore multiply.
Step 4: Joints that consume a lot of oxygen so that the amount decreases to the point where all the aerobic creatures die including the fish, zooplankton and joints.
Stage 5 Peak: The anaerobic joints replace the aerobics and perform slow decompositions accompanied by foul-smelling gases (H2S).


Recovery stages: Stopping the flow of nutrients to the water bodies that allows the decomposition of the organic substances. Which are minimal and conditions are once again created in which the oxygen dissolved in the water does exist.

Hence the aerobic creatures return to the water.

Oxygen: Most of the aerobic creatures in the water are unable to survive in an environment where oxygen concentrations are less than 4 mg per wave.
In fact, most of the oxygen in the water comes from the dissolution of oxygen in the air above the water and another source is photosynthesis if there are aquatic plants.

Saturation Concentrations: Oxygen concentrations measured near the surface of the water mainly in pure water that is not in motion.

As the temperature is higher the saturation concentrations are low as the heat increases the movement of oxygen molecules and they leave the water. The high atmospheric pressure raises the saturation concentrations and thus reduces the amount of oxygen molecules that leave the water in favor of the air.

Oxygen concentrations decrease under the condition that the water is deep; In slow flow; in decreasing photosynthetic activity and proliferation of organic matter.

Elevation value (PH): expresses the level of acidity / alkalinity of the water. The concentrations of the hydrogen ions in the solution exceed the concentrations of the hydroxide ions The solution is defined as acidic and when the concentrations of hydroxyl ions exceed the concentrations of the hydrogen ions the solution is considered basic for the purpose of water with high potential for scale production.
The measurement values ​​are in the PH scale which expresses the concentrations of hydrogen ions in the solution and they range from 1 to 14 so that below 7 the solution is acidic and above 7 is basic. 7 expresses a neutral value.

Influencing factors: Carbon dioxide concentrations that are dissolved in water and come from the air as well as creatures that emit it into the water.
As the water temperature rises the solubility of the carbon dioxide decreases. Its presence creates carbon dioxide in the water as a carbonic acid H2CO3 which causes an increase in the acidity level of the water.

The types of minerals that reach water from the soil also affect the elevation values. The limestone rocks that enrich the water with minerals raise the pH and the ability to form scale. Too acidic and / or alkaline water harms the creatures that live in them.

Hardness: is the amount of concentration of calcium and magnesium ions in water. The higher the amount of these ions, they are considered to be harder and are actually the main causes of scale buildup in the water and hence scale damage in the solar water heater and more. Their response values ​​are high as they produce solution Which tends to be a basic solution.

The country has hard water in all areas because the rainwater comes in direct contact with limestone rocks that tend to form such solutions and
produce water that is capable of exporting scale.

Metals and Synthetic Materials: Heavy metals with high atomic masses such as lead, mercury, cadmium, nickel and the synthetic substances found in water can harm living organisms in both water and terrestrial creatures that drink this water and thus pose a life-threatening drink to some of them. Pesticides, water seepage through waste and a by-product of water disinfection such as chlorine.

Biological amplification: A condition in which the damage increases as they increase in the food chain. Heavy metals and synthetic substances penetrate the body of these creatures through the water and some remain in them. In fact, creatures do not have a natural / physical mechanism to eliminate these substances. More in the chain, and so on. The damage is not immediate but long-lasting as these substances remain in the environment long after the infection.

The best example of mercury contamination is the case of the residents of the village of Minamata in Japan who began to get sick in 1953 in an unconventional way as people died and the others became disabled. It turned out that a factory in the city of foreign wastewater containing mercury accumulated in fish the main food source for the villagers. Stopping the effluent flow that included mercury Hundreds of people have died from poisoning and another 1,500 people still suffer from the symptoms of mercury poisoning.

Biological Indices:

Concentrations of Organic Substance in Water:

What exactly is an organic substance in water?

A substance formed from the inventions of living things, the secretions of living things, dead organisms that have not yet decomposed and organic compounds that are in fact the product of decomposition processes. The water also contains artificial organic compounds such as: fuels and oils.

A large amount of organic matter indicates the high level of pollution and disqualifies the water for use for any purpose.

Measurement of the amount of organic matter in water: the BOD and the COD.

ZHB: The amount of oxygen consumed in the breathing process by creatures that live in the water and especially the bacteria that feed on organic matter in the water, for the benefit of the breathing process. The amount of oxygen consumed expresses the amount of organic matter in the water.

The standard test for ZHB: Fill a sample test tube with water that is tested and measure oxygen concentrations in the water.
Then seal the bottle tightly so that air does not penetrate and keep it in complete darkness for five days at a temperature of 200. After five days, the oxygen concentrations in the water are checked. The ZHB value is actually the difference between the oxygen concentrations in the initial test and the oxygen concentrations in the second test. The value obtained is measured in milligrams of oxygen per liter,
it is clear to us that after 5 days the amount of organic matter is small.
When the amount of organic matter is high, it means that all the oxygen in the tested water was utilized before all the organic matter decomposed. Therefore, when water has high TB ​​values ​​such as wastewater, for example, it should be diluted and measured immediately (even after 5 days).

The test is performed when the water contains a toxic substance that does not decompose such as oil and oil or does not allow the activity of bacteria at all. Hence, a substance is added to the water that reacts with all organic substances in the water, and decomposes them. The measurement of the above-mentioned material consumed is in fact a measurement of an organic substance in water. Therefore, the value obtained can be translated into units of oxygen consumption and compared to the IDF.

Presence of pathogenic factors: Water in nature usually contains a certain amount of microorganisms, mainly bacteria that originate from the soil but do not cause health damage. Antimicrobial infection can be caused by the excretion of animals as well as humans which contains bacteria, viruses, and parasites. So drinking and contact with contaminated water can cause immediate and varied illnesses such as jaundice, cholera, intestinal diseases, skin diseases, and eye diseases.

Millions of people die each year from these diseases and about a third of them are babies.

Isolation and identification of pathogenic bacteria: The methods of testing are both complex and slow and expensive. It is, therefore, simpler to check for the presence of the E.coli bacterium from the coliform group which is easy to detect and is permanently present in the human and animal digestive system but is harmless.
Its presence in water indicates the excretion of humans and animals in the water. It is therefore considered a marker indicating water suspected of pathogenic infection.
The standard for coliform concentrations in 100 mg of water: zero in drinking water, 100 mg in pool water, 200 mg in bathing water at beaches, and 1000 mg in water without human contacts such as a kit and fishing.

Radiological indicators:
Radioactive radiation can also pollute the water in natural sources such as groundwater from the rocks that contain radiation-emitting elements or from human activity, for example toxic waste from hospitals and/or industrial plants.

Above a certain threshold, the radiation may alter the DNA structure of the animal body and also cause the development of cancer. Exposure to radiation from both drinking and contact.