Question: Nitrogenous waste sensors for 24/7 monitoring

winsorje is asking a question about water-quality
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by winsorje | March 24, 2017 19:31 | #14056

I'm new to this site so please redirect if need be...

I am a high school teacher in central Michigan. I teach a variety of courses including all of our high school Earth and Life Science. I have been a "Salmon in the Classroom" teacher for 10 years and through that experience have collected an array of information on the tributary in which we release our fish at the end of the school year. This has lead to other learning opportunities for my students (and me). Currently, my classes are working with a large aquaponics system that they designed and constructed. We are raising rainbow trout in that system given my familiarity with raising salmon. I have a student that is interested in designing a system that monitors nitrogenous waste (ammonia, nitrite, nitrate - possibly others) in real time. We have been working with our tech department to give him access to the school network and he is currently writing some code/trouble-shooting ways to collect data and publish real-time graphs of our system. He is using a Raspberry pi 3 for this project. What we are finding is that we cannot get any probes that will measure the substances that we would like to that are very cost effective. I am financing all of this work for him so expensive ammonia, nitrate and nitrite probes aren't in my budget. I'm excited that this type of community exists and have numerous other questions regarding projects/work within my classroom and how my students can engage in "citizen science." Any assistance here would be greatly appreciated. Here is a link to our aquaponics website for reference.


I have not worked with water chemistry sensors, but your first impression might be a good one -- a device that can send encoded concentrations of N molecules will be expensive, proprietary, and require regular calibration. There are some ideas out there for making a DIY colorimeter to quantify a color reagent test, but developing an automated version of that sort of thing is more like a master's degree project than a high school assignment.

If there is large variation in the nitrogen molecule concentration, maybe there is a proxy that could be measured. For example, if the N concentration changes dramatically, maybe temperature, conductivity, turbidity, and water color also change in a certain way. It's easier to make sensors for those parameters, and real time data on all of them might provide a signature for N concentration. Tracking those parameters would certainly alert you to changes in the system even if you weren't sure what caused them.


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