• Written by Josje Spierings
    29 March 2016

Check out all the latest blogs about Caddisfly on akvo.org, or take a look at this Tumblr blog from Ternup Labs.
Since 2011, numerous organisations and governments all around the globe have been mapping
water points with Akvo FLOW.

In 2012, our development team at Ternup Labs in Bangalore started working on a simple, low-cost, open source mobile screening test for fluoride, with the best tool for the job: the smartphone. Since then, we’ve been working to provide people in the field with a tool to do mobile water quality testing as well. And, with help from several partners, including lead funding partner SNV, we’ve been focusing on developing Akvo Caddisfly, which we introduced in April 2015.

At the moment, besides fluoride, we are developing additional kinds of water quality tests for the Caddisfly app. These tests are a product of combining hardware, software and the use of the Akvo FLOW platform, which makes it really powerful.  All collected results are stored in the phone immediately and are sent to the Akvo FLOW platform, where they can be accessed remotely online.

Here’s an update on what we’ve been working on in recent months.

1) Colorimetric testing using a smartphone in combination with special hardware

Above: the Akvo Caddisfly fluoride testing kit.

Field-test equipment is often expensive, hard to use, and unreliable. Lab tests are still costly and slow. Resulting data is generally stored locally and not shared effectively across the people that need to use it. The Akvo Caddisfly colorimetric tests are designed to be a simple, fast, portable and low cost drinking water testing kit that can be used anywhere to quickly analyse the level of contaminants in drinking water, using a smartphone.

The first step is to add a specific reagent to a water sample in a testing chamber on your smartphone. The phone’s camera takes a picture to detect the colour of the sample. The Caddisfly app then translates this color into the actual concentration of the contaminant in the water sample.

We are currently developing tests for:

  • Fluoride (Pilots done in India, Kenya, Burkina Faso, Ethiopia and Tanzania.)
  • Arsenic (Under development and pilots coming soon)
  • Coliform (Under development and pilots coming soon).

Besides these parameters, we are also prototyping colorimetric testing for chlorine and turbidity.

Our fluoride test has been piloted and validated at scale and proven to be reliable. By mid 2016 we will have a high fidelity prototype which can be manufactured and distributed in large volumes.

2) Colorimetric testing using test strips 


Above: using the Akvo Caddisfly color calibration card in Kayes, Mali. Photo by Josje Spierings.

Test strips are a simple and inexpensive way to test water quality on a plethora of parameters. Dip a test strip into a water sample and the colour of the strip changes depending on the concentration of the parameter you are testing. Compare the strip’s new colour with the reference colours on the package, and there you have your result. Yet, this test might be subject to errors, as not everyone sees colours in the same way. There is a big factor of human variance in the results. Besides this, the data has no geolocation and needs to be manually entered into a data system, with risk of further errors.

We have recently developed a new app which is capable of standardising the results of the test strips, gathering more accurate results. You take a photo of the test strip and position it on a colour calibration card. Then the app interprets the colour of the test strip and calculates the test result. You can use this, in principle, for any test strip available on the market. With this, anyone in the field can collect accurate water quality information regardless of how their eyes interpret colour. The app reduces the variance in the results.

We are currently piloting this in Mali, Ethiopia, Kenya and Tanzania for one or more of the following parameters:

  • Chlorine
  • Iron
  • Nitrate/nitrite
  • pH
  • Phosphate

3) Electrical conductivity using a smartphone and a sensor


Above: the Akvo Caddisfly electrical conductivity sensor. Photo by Josje Spierings.

Use of electrical conductivity sensors is widespread around the globe. Yet, it’s usually expensive to get an accurate one. Results are generally written down on paper or typed into a phone manually, which can cause errors.

Together with Acacia and Sodaq and with the support of SNV, we have developed an electrical conductivity sensor (EC sensor) to measure how well water conducts electricity. The higher the concentration of dissolved salts in water, the better it conducts electricity, which is an important indicator of water salinity. This includes not only what we know as ‘kitchen salt’ but also elements like sodium, calcium, potassium, etc.. After determining the salinity of the water, further tests, using a test strip for example, can be conducted to detect the type of salt.

You can plug the EC sensor directly into the micro-USB port of your Android smartphone. This enables the data to be transferred to your phone and also powers the EC sensor.

With the EC sensor,  Akvo Caddisfly provides a low cost sensor using open source Arduino hardware, which can immediately be connected to your smartphone.

Read ”Dutch farmers test water quality in North Holland” to learn more about how EC sensors are being used to test the salinity of surface water.

What’s coming next?

The development of Akvo Caddisfly is ongoing. Currently, our tests are being piloted and results are being analysed. We have not officially rolled out Akvo Caddisfly yet but news on that will follow soon.

Related to the Sustainable Development Goals (SDGs) Goal 6 – “Ensure availability and sustainable management of water and sanitation for all”, and the monitoring protocol (which is still under discussion), we are also looking at parameters like the percentage of dissolved oxygen and other parameters.

If you are interested in becoming one of our pilot partners, or in hearing more about the pilot results so far, please contact Hans [at] akvo.org or Josje [at] akvo.org.

Josje Spierings is Project Manager at Akvo in Amsterdam. Follow her on Twitter @JosjeSpierings.

This blog was updated on 25 May 2016 to add mention of partners supporting Caddisfly’s development in the 2nd paragraph.