pH of water (Environmental Engineering)

pH scale

pH scale

pH of water sample is an important parameter which is to be constantly checked for or monitored either for performing the various tests on water samples or for the release of waste water into streams or rivers. pH plays an important role as this value would affect the solubility of certain nutrients and metal compounds.

* pH is defined as the negative of logarithmic of hydrogen ion concentration of a sample. Mathematically represented as

pH =  – log [ H+]                     where H+ represents the hydrogen ion concentration

* It defines how acidic or basic the sample is. It varies from 0-14 where 0 represents the sample to be very highly acidic and 14 being a very alkaline one.

* In case of water either for testing or for the release into streams or rivers a pH value in the range 6.5-8.1 is to be maintained as only in this range of pH aquatic life would sustain and also the wide range of indicators etc we will be using in the tests are calibrated for this range of pH. If the pH value decreases due to several reasons of a river or a stream like acid rain etc this will certainly increase the solubility of heavy metals which in turn increases the toxicity of water. Also a change in pH value varies the concentration of various nutrients in the water which will affect the growth of aquatic plants changing the concentration of “Dissolved Oxygen“. 

* Various tests can be performed in the laboratory to determine the pH value of a water sample. Some of them are:

1. pH determination using pH paper

2. pH determination by color comparison (Universal Indicator is used)

3. pH determination by using pH meter.


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