TREATMENT OF WASTE WATER DEHYDRATED FROM LOW GRADE COAL

PURPOSE:To reduce the necessary amount of powdery low grade coal to a large extent, by connecting a plurality of apparatus systems each consisting of a contact tank and a solid-liquid separation tank in series and returning powdery carbon-containing sludge separated by once performing adsorption treatment to the contact tank of the preceding system to reuse the same. CONSTITUTION:Waste water dehydrated from low grade coal containing org. components at high concn. is sent into a first contact tank 1a to be contacted with the sludge returned from a second solid-liquid separation tank 2b and, thereafter, sludge is withdrawn from a first solid-liquid separation tank 2a. The separated liquid from the tank 2a is sent into a rear stage contact tank 1b and a powdery carbon-containing composition such as powdery low grade coal or dry distillation char is thrown in said liquid to be contacted therewith. Subsequently, solid-liquid separation is performed in the second solid-liquid separation tank 2b and solid-containing sludge is returned to the first contact tank 1a and the liquid part is sent to a rear stage flocculative precipitation apparatus or biological treatment apparatus.