Below is a list of frequently asked questions and their answers.

Do you have another question? Feel free to ask in the comments below!

Question
Answer
What is the accuracy of the Aquality App?The accuracy depends on the accuracy of the test strips. Test strips for nitrate give an indicative measurement. In our tests, we've found an accuracy of ~30%, while conventional laboratory measurements have an accuracy around 10%. See also the Accuracy page.
What does it cost?~1 EUR per measurement. Check the getting started page for an order form.
What do I need for a nitrate concentration measurement?For a nitrate concentration measurement you need Hach Nitrate test strips, an Aquality App reference card, and a smartphone with the Aquality App installed. Check the getting started page.
Why do you recommend to fingerflick of excess water and  measure after 60s (instead of after 30s without removing excess water according to the instructions on the package)?Testing with lab comparisons revealed that scanning after 60s gives better results (after 30s gives underestimates the concentration) and flicking of excess water gives more stable results (lower variance in duplo measurements).
Can the Aquality App be used in brackish or salt water?Yes, but not in hypersaline water (salter than sea water).
Can the Aquality App be used in turbid water?The turbidity of the water may have impact on the color of the teststrip and the result. Check the result carefully. You can also filter the water to get a clear sample, or use a piece of toilet paper to extract a clear sample (see the soil Nmin protocol).
How do the light intensity and camera quality affect the measurements?This impact is minimized by combining the test strip and the legend on the reference card on the same scan in the same light conditions. Make sure that the scan is not under- or overexposed and that the color differences of the legend are visible. Shadow transitions on the reference card can influence the result and should be avoided. We advise to block direct sunlight (measure in your own shadow). Some smartphone camera's have problems with focusing on nearby objects and therefore with recognizing the markers on the corners.
Why doesn't the Aquality App recognize my reference card?This can have different causes; most important are the markers on the corners of the reference card. Are they still intact and clean? Also, some smartphones have problems with focusing on nearby objects; try different distances and angles.
My surface water looks very eutrophic with a lot of algae, yet the nitrate concentrations are zero. How is this possible?Especially in stagnant surface waters, algae can consume nitrate or low oxygen levels can induce denitrification.
Does the Aquality App also work with other brands of test strips?No, other test strips have different legend colors.
Can I also measure other water quality parameters with the Aquality App?We enabled measuring salinity (EC) by using the Aquality App to scan the result from a Hanna Dist4 EC meter, see the Aquality App for EC measurements page. More options will follow.
Can I also measure nitrate content in soils?A do-it-yourself protocol for soil Nmin measurements is described at the Aquality App for Soil Nmin measurements page.
What is your business model?Like all Deltares software, the app is free ('dare to share'). We're mainly interested in finding new projects to work on the next developments for the app, which will then become available for the entire user community. Organizations with specific requests (e.g. other parameters, an own private web viewer) are encouraged to contact us.
Can I also measure ammonium and phosphate?

Working on that; we now recommend using Hanna checkers for this,

See:

AmmoniumCheckers-HI700-HI715-HI733-EN.pdf (english version)

AmmoniumCheckers-hi700-hi715-hi733-hi784-nl.pdf (dutch version)


13 Comments

  1. Anonymous

    How do I become a registered user to have access to the "Delta Data Viewer"?

    1. Joachim Rozemeijer

      The Delta Data Viewer has been customized specifically for a group of farmers in the eastern part of the Netherlands. Only this group of farmers has access to this viewer.

       

      1. Anonymous

        Thank you for your prompt reply. If a group of farmers accept to participate in a monitoring program based on this app, is there a way too retrieve the data collectively monitored by these farmers?

        1. Joachim Rozemeijer

          Yes, you can have acces to the database via an online map http://tl-ng015.xtr.deltares.nl/waterkwaliteit-app-service/map.html and/or you can select your measurements from our database at http://tl-ng015.xtr.deltares.nl/waterkwaliteit-app-service/v1/waterkwaliteitmetingen.csv/?period=LASTYEAR

          We are currently working on a group login on the app; that would support to share measurements only within a group and not with everybody.

           

          1. Anonymous

            Great. Thanks a lot for your quick responses.

            1. Anonymous

              Hi Joachim,

              It's me again. I can access the databased through the link you send. It works really; thanks. However, I don't understand the date/time format used in column 3 (e.g. 1491385445593). Can you help me with that?

              Thank you,

              Diogo

              1. Anonymous

                Hi Diogo,

                The time is in unix epoch time (milliseconds since 1970).

                I hope this is helpfull.

                Joachim

                1. Anonymous

                  Yes. That's what I need. Great. 

                  Many thanks.

                  Diogo

  2. Anonymous

    Hi Joachim,

    This is Diogo again. The link you provided above for accessing the measurements database is now broken: http://tl-ng015.xtr.deltares.nl/waterkwaliteit-app-service/v1/waterkwaliteitmetingen.csv/?period=LASTYEAR

    Can you please advise on this?

    Thank you,

    Diogo

    1. Anonymous

      Hi Diogo,

      We secured the internet connection, try this one:

      https://tl-ng015.xtr.deltares.nl/waterkwaliteit-app-service/v1/waterqualitymeasurements.csv/?period=LASTYEAR

      All the best, Joachim

  3. Anonymous

    Hi Joachim,

    Great. Yes, it works.

    Thanks a lot for your quick response.

    All the best,

    Diogo

  4. Anonymous

    I am in the US. I can order the test strips from Hach and I was able to get the app, but I am not sure how I can get the card.  The Hach page did not have a way to get one.  Is there a US based source?

  5. Joachim Rozemeijer

    The cards have only been distributed via the Dutch Hach office so far. If you email me (joachim.rozemeijer@deltares.nl) your address I can send you some.

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