laboratory tests

Important types of laboratory tests for water

In this article, we mentioned the importance of laboratory tests for water treatment. And the consequent guarantee of water quality, and avoiding potential problems if laboratory tests are constantly neglected.

Taking water samples for laboratory tests:

​The quality of drinking water is constantly monitored by monitoring various microbiological and chemical parameters. It is also specified in the sanitary quality systems for drinking water, which are periodically updated. These measurements make it possible to distinguish the components of water. Ensure its hygienic quality and formal taste, as well as follow the trends of changes. And the discovery of difficult problems related to the quality of drinking water in order to preserve the health of the public.

When determining water quality, the test results refer to only the sample that was tested. Therefore, the sample must best represent the form of the water from which it was taken. The sampling process is the first and central stage by conducting a water test. Proper sampling is necessary in order to obtain correct results.

 

Physical Measurements

Turbidity

It was found that there is a relationship between turbidity, water safety, taste, and odor in untreated natural water and treated filtered water. It was found that 50% of the causes of turbidity are due to the decomposition of organic matter in the form of colloidal substances.

There is a relationship between turbidity and bacterial content in water. As nutrients stick to the surface of the particles causing turbidity and thus helping bacterial growth. Turbidity also limits the detection of bacteria and viruses in water.

Effect of turbidity on water treatment

Turbidity reduces the effectiveness of chlorine in disinfecting water, and therefore water needs larger quantities of chlorine to kill bacteria and pathogens. E. coli bacteria were detected in water with turbidity between 4-84 units and containing 0.1-0.5 ppm residual chlorine after a contact period of not less than 30 minutes.

Turbidity Meter

Turbidity is measured with a Turbidity Meter

The turbidity of drinking water shall not exceed (1) in Naphalometric Units (NTU).

The idea of ​​the device working depends on projecting a light on the water sample, so the turbidity in the sample causes dispersal of the incident light, and the intensity of the scattered light expresses the amount of turbidity in the sample.

 

Power of Hydrogen (pH)

The ionization process is defined as: “the process of converting molecules of a compound into ions”. As for water, its ionization rate is very weak, when compared to the ionization rates of other compounds. However, some water molecules may decompose into positive hydrogen ions (+H) and negative hydroxyl (-OH).

It was found that an increase in the concentration of hydrogen ions. It means an increase in the acidity of this liquid, while an increase in the concentration of a hydroxyl ion means an increase in its alkalinity. In the case of pure water, the number of hydrogen ions is equal to the number of hydroxyl ions, that is, it is neutral.

pH meter

We can measure it (the concentration of hydrogen ions) in the water with a pH Meter

Acid-neutral substances, such as pure water, have a pH value of 7, as for acids. The pH ranges between zero and 6.9, and alkaline substances have a pH value ranging between 7 and 14. Most of the biological processes take place in a limited range of pH. If the pH is higher or lower than this range. The vital processes or the natural functions of the body are disturbed.

For example, the pH value of human blood is 7.4. It means that the blood is alkaline and this alkalinity must be maintained, as even small changes are dangerous. If the hydrogen ion concentration rises to 6.95 (that is, it is almost above the limit and is located on the acidic side. The person will fall into a coma and then die, and if the hydrogen ion concentration in the blood drops to 7.7, the person will have convulsions). With acidic blood, the heart relaxes and stops beating, and with highly alkaline blood, the heart contracts and stops beating.

It should be noted that a change in the pH value by one degree. It means a change in the degree of acidity by an amount of 10 times.

A solution with a pH value of 3 is 10 times more acidic than a solution with a pH value of 4 because the pH or alkalinity has a logarithmic relationship (decimal logarithm) with the hydrogen ion concentration in the solution.

Effect of pH on water treatment

Water sterilization with chlorine is more effective if the pH is less than 8, and therefore the appropriate rate was chosen for water standards with a pH between 6.5 – 8.5. This means that the water does not contain mineral acids or highly alkaline substances.

We can measure pH by colorimetric comparison or by using an electrical pH measuring device equipped with a special electrode for measurement.

The electrode of the pH measuring device is a silver wire coated with chloride

Silver and dipped in a solution of saturated potassium chloride.

Solution Buffer

Solutions with constant pH, are solutions that resist the sudden change in the pH value when an acid or base is added to it in small quantities. These solutions are used in the calibration of the device.


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