초록 ▼

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 was

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.

대표청구항 ▼

[ What is claimed is:] [1.]1. A process for the treatment of an effluent stream containing water and an organic acid species which is a stronger acid than carbonic acid, comprising:adding an alkaline medium to increase the pH of the effluent stream;subjecting the effluent stream to oxidation treatme

[ What is claimed is:] [1.]1. A process for the treatment of an effluent stream containing water and an organic acid species which is a stronger acid than carbonic acid, comprising:adding an alkaline medium to increase the pH of the effluent stream;subjecting the effluent stream to oxidation treatment to convert the organic acid species to carbon dioxide, water and carbonate and/or bicarbonate ions;separating the oxidised effluent stream into a concentrated aqueous stream rich in (bi)carbonate ions and cationic species derived from said alkaline medium and a depleted aqueous stream which is substantially free of said (bi)carbonate ions and said cationic species; andrecycling the concentrated stream for direct or indirect use as said alkaline medium. [11.]11. Plant for the production of an aromatic carboxylic acid, comprising:an oxidation zone in which a crude acid is first produced by the liquid phase oxidation of a precursor of the acid in an aliphatic carboxylic solvent in the presence of a heavy metal catalyst system;a solids-liquid separation section in which crystals of the crude aromatic carboxylic acid are separated from oxidation zone mother liquor comprising mainly said aliphatic carboxylic acid solvent;a purification zone in which the crude acid crystals are dissolved in aqueous medium and the resulting aqueous solution is hydrogenated to reduce the impurity content of the aromatic carboxylic acid;a pure solids-liquid separation section in which purified crystals of the aromatic carboxylic acid are separated from the purification zone aqueous mother liquor;an organics digestion stage receiving at least part of said purification zone mother liquor in treated or untreated form and producing a reduced COD aqueous stream containing suspended solids and dissolved species including (bi)carbonate ions;means for adjusting the pH of the purification zone mother liquor by addition of alkaline medium prior to, or during, treatment within the organics digestion stage;a solids-liquid separation stage receiving said reduced COD stream and separating the same into a solids-rich stream comprising a minor fraction of the water from said reduced COD stream together with suspended solids and a substantially solids-free stream containing the major fraction of the water from said reduced COD stream and dissolved species including (bi)carbonate ions;a reverse osmosis membrane stage for receiving said solids-free stream and producing a retentate stream comprising a minor fraction of the water from said solids-free stream and containing substantially all of the impurities constituted by said dissolved species, including (bi)carbonate ions and cationic species from said alkaline medium, in the solids-free stream and a permeate stream comprising the major fraction of water and residual dissolved species from the solids-free stream; andmeans for recycling at least part of the retentate stream directly or indirectly to said pH adjusting means.12. Plant as claimed in claim 11 including means for feeding the recovered oxidation zone mother liquor in part as a recycle stream to the oxidation zone and in part as a purge stream to a solvent recovery zone in which the purge stream is concentrated to produce a residue containing organics and catalyst metal; means for dissolving the residue in water and recovering catalyst metals from the solution to leave an organics-containing aqueous stream; and means for feeding said aqueous stream derived from residue treatment to the solids-liquid separation stage for producing said reduced COD stream.13. Plant as claimed in claim 11 or 12 in which the solids-liquid separation stage includes a microfiltration membrane stage.