One of the techniques commonly used to measure pH analysis of a sample is used to determine the acidic or basic strength . The quantity as Log [H +] = pH acidic and usually ranges from 0 to 14 are defined . PH measurement of acid color reagent ( a solution of paper or color scale ) or potentiometric method (using a glass electrode ) is done . These methods are used today in most devices pH meter accuracy is higher by using an ion selective electrode (Ion Selective) called a special glass electrode . The glass membrane electrode is used with a special compound that is sensitive only to the number of ions + H . Biological treatment of wastewater under acidic or alkaline liquid mixtures major impact on the activity of microorganisms . The pH controls the On - Line or online is required. In addition, different processes and control drinking water supply is essential for accurate pH .