Will you swim in troubled waters? And drink it from the well? Surely you will prefer clean, clear water, which is pleasant to soak up and which is not dangerous to drink. Today we’ll talk about turbidity. Is it suitable for use, and what is the danger of impurities? How to study quality? And how to get rid of negative phenomena?
What is turbidity?
Water pollution is understood to mean a change in its properties when exposed to chemical or organic substances. If such is found, the use of life-giving fluid must be suspended, as this can be dangerous for the human body.
In laboratories at treatment plants, they analyze for:
- turbidity and color of water;
- smell and acidity;
- the content of organic elements;
- the presence of heavy metals;
- chemical oxygen consumption, etc.
Contaminated liquid contains inorganic and organic fine suspensions. Turbidity of water is an indicator of the degree of transparency.
The causes of turbidity
Turbidity is indicated when solid particles of sand, pebbles, and silt most often appear in water. They are washed away by precipitation, meltwater into the river, and they can also occur as a result of the destruction of the well.
Least of all impurities in winter. Most of all - in the spring and summer, when floods often occur and a seasonal increase in plankton and algae is observed.
State standards
In our country, the turbidity of water is determined by comparing two samples: a standard and taken directly from a reservoir. Use the photometric method. The result is expressed in two ways:
- when using a suspension of koalin - in mg / dm3;
- when using formazin - EM / dm3.
Last adopted by the ISO. It is designated as EMF (Formazin Turbidity Unit).
In Russia, such turbidity standards have been adopted. GOST for drinking - 2.6 EMF, for disinfecting - 1.5 EMF.
How to determine the quality of water
In any water utility there is a laboratory in which studies are conducted of the quality of the water supplied to the pipes. Measurements are carried out several times a day so as not to miss a single change. Consider the basic methods for determining the turbidity of water.
The essence of any method is that a beam of light passes through the liquid. In an absolutely transparent flask, it remains unchanged, dissipates only slightly and has a slight angle deviation. If suspended particles are present in the water, they will interfere differently with the passage of the light beam. This fact will fix the reflective device.
To date, the turbidity of drinking water can be determined by the following methods:
- Photometrically. There are two research options: turbidimetric, which captures attenuated rays, and nephelometric, which results in the reflection of scattered light.
- Visually. The degree of contamination is evaluated on a scale 10-12 cm high in a special turbidimeric tube.
Types of Suspended Particles
Any impurities found in drinking water have their own properties. They are characterized by such a parameter as hydraulic fineness, which is expressed in the sedimentation rate to the bottom in still water at a temperature of 10 ° C. We give examples of suspended particles in the table.
Suspended Particles and Their Characteristics
| Suspended matter | Size mm | Hydraulic size, mm / s | Settling time to a depth of 1 m |
| Colloidal particles | 2 × 10 -4 | 7 × 10 -6 | 4 years |
| Fine clay | 1 × 10 -3 | 7 × 10 -4 | 0.5-2 months |
| Clay | 27 × 10 -4 | 5 × 10 -3 | 2 days |
| Silt | 5 × 10 -2 | 1.7-0.5 | 10-30 minutes |
| Fine sand | 0.1 | 7 | 2.5 minutes |
| Medium sand | 0.5 | 50 | 20 seconds |
| Coarse sand | 1, 0 | 100 | 10 Seconds |
From the history of measuring turbidity
Obviously, turbidity of water is one of the most important factors affecting the quality of fluid intake. Even small changes in the standards indicate the presence of pathogenic flora, which can lead to various diseases in humans. And as soon as humanity realized that cleanliness is the key to health, the need arose to test the water.
The first people to come up with special technology to study liquids in the laboratory were Whipple and Jackson, and their device was called the Jackson Candle Turbidimeter. It was a flask that was held above the candles. Water for research was placed inside, into which the world's first kieselguhr-based suspension was poured. The liquid poured slowly until the light from the candle was completely scattered. Then they looked at the scale and converted the data into Jackson units of turbidity.
Despite the fact that at that time there were no polymers and materials from natural resources were prepared for suspensions, this method, although it gave errors, used it for a very long time.
Only in 1926, the scientists of Kingsbury and Clark chemically created formazin. It is an ideal substance for studying turbidity of water. To prepare the suspension, you need to take a liter of distilled water, 5.00 g of hydrazine sulfate and 50.00 g of hexamethylenetetramine.
Method for the qualitative determination of turbidity
You will need a test tube 10-12 cm high, a sheet of black cardboard.
Sequencing:
- Type in a test tube of water.
- Place the flask so that it stands on a black background, and on the side there is a light source: the sun or an incandescent lamp.
- Visually determine the degree of turbidity: clear water, slightly polluted, slightly turbid, cloudy, very turbid.
Turbidity quantification method
You will need: a flask for analysis (height 6 cm, diameter 2.5 cm), a screen for the tube, a syringe, a pipette, a font sample (height 3.5 mm, line width 0.35 mm)
Sequencing:
- Draw water into the flask. Mount it on a tripod.
- Place a sample font down under the flask. It could just be a letter.
- Around the tube you need to create a screen to reflect light.
- Place the light source on top directly above the tube.
- Pipette water until you see a letter.
- Measure the height of the column with water. Data must be accurate to 10 mm.
