Principle

Turbidity, measured in NTU is a colorimetric test with no reagents. Turbidity is a measure of how clear water is. Distilled water should have turbidity of 0 NTU.

The Indian Standard for drinking water holds that the acceptable limit is 1 NTU, but in the absence of any other toxic substances or alternate source, this is relaxable upto 5 NTU.

Calibration

To prepare calibration standards, take 20 ml of distilled water. Depending on if you chose minimal or full calibration, prepare standards as below.

Full Calibration

Standard Drops
0 NTU 0
10 NTU 10
20 NTU 20
30 NTU 30

Minimal Calibration

Standard Drops
0 NTU 0
10 NTU 10
30 NTU 30

You do not need to add any reagent for this test. Shake the standard solutions dropper bottle thoroughly.

  • Take the 0 standard and fill it into the glass cuvette provided. Place the glass cuvette inside the blue cuvette.
  • Place the cuvette under the light stand.
  • Clip on the ring light over your phone and turn it on to maximum brightness
  • Place the phone over the stand
  • Go to Settings > Colorimetric Test > Calibrate and choose Turbidity
  • Select the calibration point, 0.00 NTU in this case
  • Click on Start Camera
  • Position the cuvette so that the middle, most uniformly lit portion is within the circle.
  • Select Analyze
  • You should have your first calibration point. Repeat similarly with the other calibration points.

Test

This test does not require a reagent.

  • Collect 20 ml of sample water and place in glass cuvette and in turn inside the blue cuvette.
  • Place the cuvette under the light stand.
  • Clip on the ring light over your phone and turn it on to maximum brightness
  • Place the phone over the stand
  • From the home screen choose Colorimetric Test > Water > Turbidity
  • Choose No Dilution if this is the first test, you might have to dilute the sample and retry later if you get an error.
  • Click on Start Camera
  • Position the cuvette so that the middle, most uniformly lit portion is within the circle.
  • Select Analyze
  • After some time, the app will display a result.