Water treatment by ballasted flocs and degreasing
The invention concerns the use of a coagulation-flocculation-decantation device for water treatment to degrease water inside the device itself so as to eliminate therefrom more than 20% of hexane-extractable matter without resorting to separate degreasing means by flotation. The invention also concerns a plant comprising a coagulation-flocculation-decantation device by ballasted flocs having a coagulation zone ( 1 ), means supplying ( 4 ) a granular material denser than water ( 4 ), a flocculation ( 6 ), a decantation zone ( 8 ) and means for recycling ( 15 ) granular material including at least a hydrocyclone ( 17 ). The characterised in that it does nut comprise degreasing means provided upstream of the coagulation-flocculation-decantation device, the grease being removed from the water inside the coagulation-flocculation-decantation device itself without means for injecting air or an equivalent gas.
1. A method of degreasing water or wastewater in the course of treating water or wastewater, comprising: subjecting the water or wastewater to treatment by flocs ballasted by granular material and directing the water or wastewater through coagulation, flocculation and sediment devices, and degreasing the water or wastewater within the coagulation, flocculation and sediment devices and eliminating at least 20% of hexane extractable material from the water or wastewater without subjecting the water or wastewater to flotation degreasing means.
2. The method of claim 1 including eliminating more than 50% of hexane extractable materials from the water or wastewater.
3. The method of claim 1 including at least partially removing grit from the water or wastewater.
4. The method of claim 3 including utilizing a coarse grit removal device upstream from the coagulation, flocculation and sediment devices and operating the coarse grit removal device at a settling speed of more than 15 m/h.
5. The method of claim 4 including operating the coarse grit removal device at a settling speed between 80 and 200 m/h.