In order for the Aquality app (formerly: Nitrate App) to provide a good colour reading, it is important that all of the materials be clean and dry. In particular, the four black corner markers and the reference legend on the legend card should not be dirty or covered. Keep test strips sealed in a jar at room temperature until use.

A detailed visual user guide is available here.


  1. Jar with test strips (for nitrate, use Hach test strips)
  2. Deltares legend card
  3. Smartphone with the Aquality App


Step-by-step guide

  1. Take a water sample
    1. Rinse the cup before taking a water sample
    2. Reduce the amount of mud, plants and animals that get into the sample
    3. Do not fall into the water
  2. Take out a test strip and your smartphone
    1. Do this with clean, dry hands
    2. Close the lid of the jar with the test strips
  3. Turn on the Aquality app and go to the 'take picture' screen
    1. Press on the photo icon on the home screen
    2. At the top of the 'take picture' screen, a clock indicates the hours, minutes, and seconds
  4. Dip the test strip in the water sample for 1 second and look at the seconds on the screen
    1. Remember the time when you took the sample (seconds)
    2. Do not wave or shake the test strip to dry it
    3. Place the test strip on the black line next to the legend on the legend card
    4. Ensure that the test strip, legend, and four corners of the card are clean and dry and are not covered by dirt or your fingers
  5. Sixty (60) seconds after the strip was dipped in the water, take a picture with the Aquality App
    1. Ensure that there is enough light to take the picture
    2. Press on the screen when you are ready to take the photo. As soon as the legend card is identified, a picture is automatically taken as well.
    3. The image should be clear, straight, and without shadows
    4. A blue cross means that one of the corner points has been detected, and a green frame means that the legend card has been identified
    5. Practice makes perfect
  6. Check and send the measurement
    1. Check if the measured value is plausible: does it correspond to what you had in mind?
    2. Press 'OK' to send the measurement; you can also add a comment and include the water type (e.g., surface water, groundwater)
    3. If your data usage is restricted, the measurement is still stored and sent the next time you connect to Wi-Fi/data (as long as the Aquality app is still running)
  7. Close the Aquality app or (even better) take another sample