Acid and alkali treatment

Industrial processes such as metal surface treatment or chemical operations can also generate acidic and alkaline liquid waste. Because of their strongly corrosive nature, without proper treatment these can be dangerous to people, to equipment and to the environment. One fundamental method of acid and alkali treatment is neutralisation, in which the pH of the waste is brought into the desired range under controlled conditions. To do this, the acidic or alkaline waste is reacted with a suitable treatment agent. This is not simply a matter of pouring acid and alkali together, but a controlled technological process. During treatment, the pH value – that is, how acidic or alkaline the liquid is – and the progress of the reaction must be monitored continuously. As a result of the treatment, some dissolved contaminants may precipitate in solid form and can later be separated from the liquid. At the end of the process, liquid and solid fractions are produced that are far safer to handle than the original waste. Their further treatment or disposal can then be determined on the basis of their composition. The aim of acid and alkali treatment is therefore to reduce the corrosive, hazardous pH and to prepare the waste for safe further treatment.