Process and apparatus for decoloring and/or neutralising alkaline waste waters and for decreasing their salt content, particularly for purifying effluents from the textile industry

摘要

The invention relates to a process and an apparatus for decolorising and/or neutralising alkaline industrial effluents and for reducing their salt content in plants where the technology requires soft water to be produced on site and the water softening is carried out by using cation exchange synthetic resin. The essence of the process comprises mixing the calcium- and magnesium-containing solution, produced during regeneration of the water softener (1), with the alkaline waste water, removing the precipitate that forms, converting a portion of the clarified alkaline water with the hydrogen form of the synthetic resin to give an acidic solution and using this to neutralise the other portion of the alkaline water. The salt solution forming during the regeneration of the hydrogen form of the synthetic resin is used to regenerate the water softener (1), and with an acidic salt solution this is neutralised with at most 1% of the alkaline water. The apparatus comprises, connected in series after the water softener (1), a solution store (3), mixing container (5), clarification device (8), distribution valve (9), ion exchanger (10), a bypass line (16) bypassing the ion exchanger (10) and a neutralisation tank (15). A channel (11) for leading off liquid from the ion exchanger (10) and the bypass line (16) lead into the neutralisation tank (15). A lye pipe (19) leads from the machinery (20) into the mixing container (5), while a channel (17) for removing precipitate branches off from the bottom of the clarification device (8). The ion exchanger (10) is allocated to a regenerating acid container (27), and a salt solution line (26) leads from the ion exchanger (10) to the salt solution container (25) of the water softener (1). IMAGE