Waste water or slurry coming from the processing lines (marble, granite, agglomerate, ceramic, cement, aggregate, etc.) is conveyed by means of piping to the collection tank, where a submersed motor- driven pump, controlled by a limit level probe, auto- matically convey the slurry to the decanter . On its way to the decanter, the slurry is treated with flocculent (a biodegradable chemical), which is dissolved in the upper tank of the flocculant station by means of an electric mixing device and drained into the lower tank, where a batching and drained into the lower tank, where a batching pump injects the flocculant into the decanter feed line. The flocculant acts on the sediment particles contained in the slurry, causing them to stick together; this results in a shorter sedimentation time. The slurry is fed into the decanter through the inner parallel pipes and its speed is varied in the tapering cone section. The unpolluted water rises through the decanter's central ring into the specially shaped upper channel, from where it passes through the piping into the clean water collection tank. From here a pump would have to be utilized to re-cycle the clean water back to processing line. The sludge deposited at the bottom of the cone in the decanter is removed automatically at regular intervals by a pneumatic valve fed by a compressor. The sludge is then conveyed by piping to the sedimentation collection tank, where a probe unit controls its level.