Purifying waste water esp. water from photographic industry, electroplating, eloxal process or neutralisation

摘要

Waste water is purified by subjecting the waste water at least once to reverse osmosis. Also claimed is the apparatus for carrying out the above process comprising a reverse osmosis unit. Further claimed is the use of the above apparatus for carrying out the above process. Pref. the permeate (I) is purified at least once through further reverse osmosis. The greater part of the concentrate (I) and 100% of the concentrate (II) are recycled to the waste water to be treated. The pressure in the reverse osmosis is adjusted so that the ratio of the permeate (II) obtd. in the 2nd reverse osmosis to the concentrate (II) is 70:30-90:10 (85:15). Permeates (I) and/or (II) are purified further in a mixed bed filter. Before the reverse osmosis, an alkali is added to the waste water, esp. to pH at least 7 (7.5-7.8).