Copyright © 2019 by PuntSeq. All rights reserved.

DIY Arduino Water Testing

Every living organism has a preferred environment in which it feels comfortable. Some like it dark, some like it warm, others prefer strong currents or standing water. To be able to align environmental parameters with the DNA data from the MinION, we have built a simple DIY (do-it-yourself) measurement kit.

It includes:

  1. A water temperature sensor. Many organisms are very sensitive to temperature fluctuations. For example, it is well known that differences in temperature can have a large impact on the abundance of certain bacterial species in Northern European lakes (see Lindström et al., Applied Environmental Microbiology 2005). You might have noticed this phenomenon when baking bread or cakes: a yeast culture is relatively inactive in the fridge, but at room temperature your yeast culture is so active it causes your dough to visibly expand!

  2. A dissolved oxygen sensor. Just like us humans breathe air to absorb oxygen with our lungs, fish and other river inhabitants also rely on oxygen that is dissolved in the water (see Kurilkina et al., FEMS Microbial Ecology 2016). The amount of dissolved oxygen depends on water flow-rate, temperature and levels of nutrients such as phosphate (PO43-) or nitrate (NO3-). You might have heard of instances where the fish population of an entire lake was wiped out by water hypoxia. This can happen in the summer when water temperatures rise in eutrophic standing water regions, usually accompanied by rapid algal growth that depletes all oxygen - especially during night time when photosynthetic activity is absent.

  3. A pH sensor. The pH is a measure of how acidic or basic the water is. The pH of a healthy river usually lies in the range of 6.5 – 8.5. Different bacteria favour different pH levels (see Percent et al., Applied Environmental Microbiology 2008). The pH is influenced by geological variables, (acidic) rain, algae, nearby livestock or fields that are frequently being fertilised.

  4. A turbidity sensor. Turbidity is a measure of how cloudy water is, i.e. it tells us how much sediment from the river we caught or how well algae grow in the water. The turbidity that we measure will depend on where exactly in the river we take the water from, e.g. taking water near the river bank usually means obtaining higher soil proportions, whereas taking water from the centre of the river - where flow speed is high - usually means clearer water.

These four sensors will give us a good indication of local water environment. With a bit of luck, we can draw direct correlations between (combinations of) these four indicators and our genetic data. This may even allow us to make predictions about biological water quality by measuring environmental parameters alone.

Building your Own Water Environment testing Kit:

 

Thanks to open source electronic prototyping platforms like Arduino, building a simple water testing equipment is easy and cheap.

 

Here is what you will need:

  • Arduino nano (with usb cable) ~£20

  • Water temperature sensor ~£2

  • pH sensor ~£45

  • Turbidity sensor ~£15

  • Prototyping breadboard, jumper wires, soldering kit, a laptop

  • A plastic box to encase the electronics

  • Reading basic tutorials on Arduino and soldering will be helpful, but even if you have never touched anything like this it will be easy enough for you to get to grips and rebuild the kit within 1-2 days.   

There are already some great tutorials on how to integrate these sensors on an Arduino Nano, and how to display their live measurements on a personal laptop. For the pH sensor we recommend this tutorial, for the dissolved oxygen sensor you find all the information on how to connect it here, for the turbidity sensor watch this video, and for the temperature sensor look here. You can use prototyping breadboard and jumper wires to build everything. We decided to solder everything and put in in a plastic box, so things don’t move around too much when cycling between sampling locations. If you need further advice on how to build your own kit, please send us an email.