WATER PLANT OPERATOR TRAINING PROGRAM
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Acids – pH Adjustment The word acid usually conjures up in the minds of the public the vision of something strong, powerful and dangerous. For the two most important acids used by water plant operators, this is the case; these two acids are sulphuric acid and hydrochloric acid. These are mineral acids because they are manufactured from minerals, not from living things. Acid consists of the hydrogen part and the acid radical part. When the acid is place into a watery solution, the two parts split apart and form positively charged hydrogen ions and negative charged acid ions. H2SO4 -> 2H+ + SO4- sulphuric acid -> hydrogen ion + sulphate ion HCl -> H hydrochloric acid -> hydrogen ion + chloride ion In the case of strong acids in solution, almost all the acid molecules split giving a high concentration of hydrogen ions. The hydrogen ions released make the water more acidic and lower the pH. Hydrochloric acid is important in water treatment because of its use in the laboratory as a cleaning agent for glassware. Sometimes it is used for pH adjustment but this is rare because it increases the chloride content of the water. Sulphuric acid is often used for pH adjustment. Concentrated sulphuric acid has a strong tendency to absorb water and gives off heat in the process. Since human cells contain water the effect of sulphuric acid on them is particularly drastic. Care must be taken when handling acids. |