Biological-chemical treatment of waste water - with dephosphatisation and recycling of the phosphate sludge to active sludge treatment

摘要

Effluent is led through an activator vessel, and the water and active sludge are led into a first separation vessel where the active sludge is sepd. Part of the active sludge is returned to the activator vessel and part is recovered as excess sludge. The effluent water from the settling stage is led into a destabilisation and flocculation vessel with a metered amt. of a chemical flocculating agent. The water is passed into a second sepn. vessel for sepn. of the chemically flocculated sludge and the whole of the sludge recovered in the second sepn. stage is returned to the activation vessel. Resistance time of the effluent water in the activator vessel is sufficiently long to allow the pptn. chemicals remaining in the recycled chemically pptd. sludge to react virtually completely with the effluent water in the activator tank. Process gives improved efficiency and a more economical use of pptn. chemicals in the chemical pptn. (dephosphatising) stage compared with prior art.