VERFAHREN UND ANLAGE ZUR REINIGUNG VON ABWASSER

In a process for the purification of sulphate-containing waste water (effluent), a solution of calcium chloride is added to the waste water having a pH of 1 to 6 in a mixing zone such that molar ratio of Ca to S04 of (0.5 to 3):1 is established in the mixing zone . The discharge from the mixing zone is led into a well-agitated holding zone while the overflow from the holding zone is transferred to a thickening zone, from which the separated thick sludge is fed to a filtrate zone. A plant for carrying out the process consists of a neutralisation unit which is constructed of a neutralisation tank, a crystalliser and a sedimentation tank. A waste water feed pipe (1) is connected to a mixing section (2) into which a feed pipe (3) for a solution containing ionogenous calcium enters tangentially. The mixing section (2) is connected flow-wise to the lower region of at least one holding tank (5). The holding tank (5) is connected flow-wise to a thickener (12), from the bottom outlet of which a sludge pipe (13) leads to a filtration unit. Finally, a pipe (14) is provided which leads from the upper region of the thickener (12) to the neutralisation tank.