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Turbidity of Water sample Using Nephelometric Method

By: Haseeb Jamal / On: Mar 23, 2017 / Experiments, Lab-Notes, How To, Environmental Lab
 
 

Theory:

Water is said to turbid when it is seen containing materials of suspension inside it. While turbidity may be defined as the measure of visible material in suspension in water, turbidity may be caused by algae or other organisms. It is generally caused by silt or clay. The amount and character of turbidity depends upon two things:

  1. Type of soil over which flows
  2. The velocity of flowing water

When water becomes stationary, the heavier and larger suspended particles settle down quickly and the lighter and finely divided particles settles very slowly and even takes months.

Ground water is less turbid because of low velocity of water. turbidity may be helpful for controlling growth of paganisms by not allowing proper sunlight to water which is necessary for their growth on the other hand it is harmful as the organisms are handling to the suspended particles. When water becomes stationary, the heavier and larger suspended particles settle down quickly and the lighter and finely divided particles settles very slowly and even takes months. Ground water is less turbid because of low velocity of water. Turbidity may be helpful for controlling growth of paganisms by not allowing proper sunlight to water which is necessary for their growth on the other hand it is harmful as the organisms are handling to the suspended particles.

There are Various units for the measurement of turbidity which are:

  1. Standard turbidity unit[mg/lit or ppm]
  2. Jackson turbidity unit [J.T.U]
  3. Nephelometric turbidity unit [N.T.U]

A device called nephelometric turbidity measures the turbidity of water in N.T.U the intensity of light after passing through the water gives a measure of turbidity of water.

WHO guideline value:

WHO suggested a guideline value for turbidity as [N.T.U]for disinfection the turbidity of water should be less than 1 N.T.U.

Apparatus:

W.H.O Nephelometric turbidity meter formazine solution of the sample by multiplying the scale reading by 0.9 N.T.U, 9 N.T.U, 99 N.T.U, test tubes and water samples.

Procedure:

  1. Switch on the power supply and check the battery of the turbidimeter,

  2. Press the 1 N.T.U button and coincide the scale with zero by using focusing template.

  3. Again press 1 N.T.U button and coincide the scale with zero using the focusing template.

  4. A Standard formazine solution of N.T.U is placed on tubidimeter in the path of rays and scale is brought 9 n.t.u

  5. The Water sample is taken in a test and is placed in turbidimeter.

  6. Use A Cell rise if the turbidity is more than 100 N.T.U and get the turbidity dilution factor.

 

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