Public Lab Research note

Inexpensive conductivity probe for drinking water monitoring network

by roberts_ecofarm | | 124 views | 4 comments |

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Here in East Central Ohio we face increasing pressure from fracking. This pressure comes in two forms, fracking well development, and injection wells used to dispose of the waste brine solution from fracking. A majority of the residents of our county and surrounding counties get their drinking water from private wells. My goal is to build a network of monitoring sites around the area to watch for changes in water quality. To do this I need to develop a low cost dissolved solids meter and data logger that can be deployed by a Citizen Science network to monitor changes in the water. The data logger has been solved by Ed Mallon at the Cave Pearl Project and other brilliant makers. The issues I face is the probe to attach to the data logger.

The issues around conductivity probes seem to break down into several areas:

1. Probe geometry and materials - material, size, spacing, number of emitter/receptors, location in the container/water profile

2. Voltage generator/data reader - AC/DC (not the band...;-), duration, amount of voltage, best generator/reader hardware (lets go for the simplest circuit to get the job done)

3. Calibration and replicability.

I've found a few ideas in all three of these areas that I plan to explore. I will be posting links and updates. I know there has been work done on this site that should link to this project. Working on it. Help is always welcome. Ideas as well.


Welcome! Very cool!

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Oh great project! Pinging in a couple people who might be interested: @cfastie @pdhixenbaugh @donblair @rebeccah @bhickman @JSummers

Anyone have ideas on the voltage question?

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A couple of clarifying questions:

  • do you have a time period in mind for sampling before data collection/processing?

  • do you have any form limitations? eg dimensional limits, a consideration if you are sampling in existing sampling wells.

  • accuracy/repeatability requirements?

The first two are somewhat minor, but the last question will really help focus the selection of sensors. dave

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Clarifying - 1. Ideally Id like to upload daily. For some sites I will be able to connect to the web either through wifi or through cell service. Some site hosts have agreed to this. (that will increase the cost of the unit a bit, but we will work with that to get current data. The other sites may have to store data for a month or more. I was thinking of hourly sampling just to give a rich data set and to catch incursions early. Each unit will need a built in backup data storage unit. This is one reason I really like what Ed has done with Cave Pearl.
2. Form limitations. We will be going into a mix of sites. Some attach to residential plumbing inside a house. Some will be at the well head outside. Others will be deployed in streams and springs. So form is a mixed bag.
3.Accuracy - We have two goals with this project. First, we what to know what is going on with our water, so monitoring change is key. Second, if there is change we want to be able to push for action. That means the data needs to be good enough to get the attention and action of the EPA at the State level. If we can get something simple that works reliably and doesn't break the bank, I expect it will get repeated in other areas of our state at least.

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