| 摘要 |
<p>In a single-tank activated sludge process or a multistage activated-sludge process using predation action of animalcules, an improvement in treatment efficiency and a decrease in the amount of excess sludge generation are achieved, while maintaining stable treated water qualities. In a biological treatment wherein organic wastewater is introduced to a first biological treatment tank 1A and is biologically treated with bacteria, the treatment liquid containing the bacteria in the first biological treatment tank 1A is introduced to a second biological treatment tank 1B and is activated-sludge treated, and the treatment liquid from the second biological treatment tank 1B is separated into sludge and treated water, a portion of the sludge in the second biological treatment tank 1B and/or at least a portion of the separated sludge is introduced into a sludge treatment tank 3 having a submerged filter element 4 with a pore diameter of 5 to 100 µm in the tank and is subjected to aerobic biological treatment, and the liquid permeated through the submerged filter element 4 is returned to the first biological treatment tank 1A and/or the second biological treatment tank 1B. Both high effect of reduction in the amount of sludge and satisfactory treated water qualities can be simultaneously achieved by reducing the amount of sludge with animalcules in the sludge treatment tank 3, allowing residual fine components to permeate through the submerged filter element 4, and, again, returning the fine components to the filter predation animalcule tank 1B for predation.</p> |
