Apparatus for concentrating sludge

A sludge concentrating apparatus comprising:

• a sludge tank which stores sludge;
• filtering means comprising a filter cloth that is shaped as an endless belt, and a plurality of rollers which turn the cloth, at least a lowermost one of the rollers being immersed in said sludge;
• a filtrate chamber including a filtrate introducing port through which filtrate from the filtering means flows into the filtrate chamber, the filter cloth being kept in close contact with the filtrate introducing port;
• cleaning means for removing sludge cakes adhering to the filter cloth;
• means for keeping a level of liquid in the filtrate chamber substantially constant;
• a sludge introducing means for introducing sludge to the sludge tank, said sludge introducing means being provided near an upper end of the filtrate introducing port;
• and
• concentrated sludge discharge means for discharging sludge from the sludge tank, said concentrated sludge discharge means being provided at a position substantially opposite to the sludge introducing means with the filter cloth therebetween;
• wherein the means for keeping the liquid level in the filtrate chamber substantially constant comprises one of:
• (a) a weir provided at a boundary between the filtrate chamber and an exit chamber into which the filtrate from the filtrate chamber flows, and (b) a riser tube which extends vertically in the filtrate chamber and communicates with a discharge pipe through which filtrate is discharged from the filtrate chamber.