| abstract |
An acidic organics-containing waste water stream (12) derived from for example plant for the production of an aromatic carboxylic acid such as terephthalic acid is treated to allow recovery of alkali and water for recycle to the production process. The treatment comprises adjusting the pH of the waste water stream using an alakaline medium, oxidising (10) the organics content of the stream to convert the same to water, carbon dioxide and (bi)carbonate ions, and supplying the treated stream to a reverse osmosis membrane (28, 30) to produce a retentate containing (bi)carbonate ions and cations derived from the alkaline medium and a permeate which is substantially free of those components. The retentate (46) is recycled for use in adjustment of the pH of the waste water stream and, if desired, water-consuming facilities which can tolerate less pure water. The permeate (44) may also be recycled, with or without further treatment, for use in water-consuming facilities within and/or associated with the production plant. |