Is there a water quality sensor that can measure elements in the water?

 I am planning a project in which I am trying to measure the amount of dissolved phosphorus and nitrogen in certain waterways, and then eventually find a way to filter out the excess of these elements, as they can be destructive for the environment. I was researching for some sensors and stumbled upon two types of sensors. TDS (total dissolved solids) sensor and an NPK (nitrogen phosphorus and potassium) sensor, (used for soil). However, I just found these and I don't know if they might work for my application. Anyone here have any experience with these sensors or suggestions for other sensors?

Thank you in advance

Since we do not know what your are looking at, I would suggest the best solution is to contact the manufacturer or his rep for that information.

There are a vast number of different compounds that contain the elements phosphorous and nitrogen. Which specific compounds do you intend to measure?

Hint: don't be deceived by advertisements for so called NPK sensors. All of them are scams.

Atlas scientific do a range of sensors pH, ORP, DO, etc

jremington:
There are a vast number of different compounds that contain the elements phosphorous and nitrogen. Which specific compounds do you intend to measure?

Hi thanks for responding.

I am specifically trying to measure for phosphates and nitrates. Sorry for not clarifying that earlier.

Probes specific to aqueous nitrate are available. They are delicate and expensive. I don't know of any that work for phosphate, but check current research literature, such as this paper: https://www.researchgate.net/publication/230893981_Sensing_and_analysis_of_soluble_phosphates_in_environmental_samples_A_review

TDS, salinity and pH probes are cheap and easy to use and in some specific cases, those measurements can be representative of soluble nitrate and phosphate ions. You will need to research the specific environments you are studying to determine if that might be the case.

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If you want to use the NPK Sensor that you can go for the Modbus module type sensor. There are some Chinese vendors who manufacture the sensor. You can easily interface the sensor with Arduino or any other microcontroller. Here is a very nice article, you can follow it: Measure Soil Nutrient using Arduino & Soil NPK Sensor