Typical low-tech, portable, field test methods for chemical water quality monitoring fall into three categories:
Test strips – These are small, single-use strips that change color to indicate the concentration of a specific chemical. Depending on the particular test, the user “activates” the paper or plastic strip by dipping it into the water sample and swishing it around, or by holding the strip in a stream of water. After waiting for a short time, the user compares the test strip color with a color chart to read the concentration of the chemical. These kits are extremely simple, but they are less accurate than other methods, especially if users don’t follow the instructions.
For example :Residual Chlorine Test Strips
Color comparison kits – Color comparison test kits are available for a wide range of chemical tests. In a typical set-up, the user adds a powder packet or a few drops of a liquid reagent to a water sample in a reusable plastic tube. The user then places the sample tube in a small plastic viewing box. This viewing box contains a color comparison card with a color gradient printed on it. The user rotates the color comparison to find the part that best matches the color of the sample, and then reads the concentration of the chemical from the disk. Color comparison kits typically have multiple steps and often include prescribed wait times, so they’re a little more complicated and costly, but generally more accurate.
For example :Dissolved Oxygen Test Kits
Hand-held digital instruments – Lightweight and portable digital meters, colorimeters, and photometers are available for water testing. They provide the most accurate results of these three testing methods, but they are also more expensive and delicate than the previous options. These instruments require batteries and calibration. While digital instruments are helpful to field technicians and are an essential part of any continuous or remote monitoring network, they are unlikely to be suitable for “citizen science” or crowdsourced water quality testing.
For example :Multi-parameter Water Quality Test Analyzer