Abstract: A ballast water treatment device includes an oxidant supply amount control device in which a storage unit stores a relationship between an absorbance of a raw water for a ballast and a dissolved organic carbon concentration thereof and another relationship between the dissolved concentration and a residual oxidant concentration required after a predetermined time from an oxidant supply, to kill organisms and to suppress their regrowth in the ballast. A calculation unit derives the required residual oxidant concentration corresponding to the absorbance measured by a meter by referring to the relationships and calculates a target oxidant supply amount using the required residual oxidant concentration. For the target, a control unit controls an oxidant supply device.

Abstract: A ballast water treatment device includes an oxidant supply amount control device in which a storage unit stores a relationship between an absorbance of a raw water for a ballast and a dissolved organic carbon concentration thereof and another relationship between the dissolved concentration and a residual oxidant concentration required after a predetermined time from an oxidant supply, to kill organisms and to suppress their regrowth in the ballast. A calculation unit derives the required residual oxidant concentration corresponding to the absorbance measured by a meter by referring to the relationships and calculates a target oxidant supply amount using the required residual oxidant concentration. For the target, a control unit controls an oxidant supply device.

Abstract: A filtration device including: a casing; a first partition wall which partitions the inside of the casing into a first raw fluid chamber and a filtered-fluid chamber; cylindrical filter elements provided inside the filtered-fluid chamber and of which the inside communicates with the first raw fluid chamber to let fluid pass through from inside toward outside to filter the fluid; a second partition wall provided on the other end of the filter elements to form a second raw fluid chamber; a wash pipe connected to an end of the filter element to let fluid flow from the raw fluid chamber in the axial direction to wash the filter elements; and a wash fluid drain pipe which discharges trapped substances, wherein the other end of the filter element connected to the wash pipe is always open to the raw fluid chamber.

Abstract: A filtration device including: a casing 1 having a fluid inlet 6, a fluid outlet 7, a raw fluid chamber 8, and a filtered-fluid chamber 9; a box-shaped or tube-shaped filter element 3 (3a, 3b) having a filter medium 31 removably installed inside the casing 1, allowing the fluid to pass through from inside to outside to filter the fluid, and having a backwashing mechanism inside thereof; and a backwash fluid discharge pipe 4 which discharges backwash fluid to the outside, wherein the backwashing mechanism has a fixed pipe 33 fixed to the inside of the filter element, a movable pipe 34 movably fitted to the outside of the fixed pipe, and a backwash head 35 attached to the movable pipe to backwash the filter medium, wherein the fixed pipe and the movable pipe movably guide the backwash head and form a discharge passage for backwash fluid.

Abstract: A filtration device including: a casing 1 having a fluid inlet 6, a fluid outlet 7, a raw fluid chamber 8, and a filtered-fluid chamber 9; a box-shaped or tube-shaped filter element 3 (3a, 3b) having a filter medium 31 removably installed inside the casing 1, allowing the fluid to pass through from inside to outside to filter the fluid, and having a backwashing mechanism inside thereof; and a backwash fluid discharge pipe 4 which discharges backwash fluid to the outside, wherein the backwashing mechanism has a fixed pipe 33 fixed to the inside of the filter element, a movable pipe 34 movably fitted to the outside of the fixed pipe, and a backwash head 35 attached to the movable pipe to backwash the filter medium, wherein the fixed pipe and the movable pipe movably guide the backwash head and form a discharge passage for backwash fluid.

Abstract: A filtration device including: a casing; a first partition wall which partitions the inside of the casing into a first raw fluid chamber and a filtered-fluid chamber; cylindrical filter elements provided inside the filtered-fluid chamber and of which the inside communicates with the first raw fluid chamber to let fluid pass through from inside toward outside to filter the fluid; a second partition wall provided on the other end of the filter elements to form a second raw fluid chamber; a wash pipe connected to an end of the filter element to let fluid flow from the raw fluid chamber in the axial direction to wash the filter elements; and a wash fluid drain pipe which discharges trapped substances, wherein the other end of the filter element connected to the wash pipe is always open to the raw fluid chamber.

Abstract: A diffuser apparatus which has fine pores is capable of achieving a high oxygen transfer efficiency and rarely becoming clogged so that the apparatus can be operated stably over a prolonged period. The diffuser apparatus includes: an aeration plate that is disposed in an aeration tank in order to release pressurized air, fed from a diffusing air feed pipe, as air bubbles from fine pores formed in an aeration plate surface; blow water feeder for feeding blow water into the diffusing air feed pipe; and an inserted pipe for discharging the blow water, fed into the diffusing air feed pipe, from the aeration plate.

Abstract: The present invention provides a diffuser apparatus which has fine pores capable of achieving a high oxygen transfer efficiency and rarely becoming clogged so that the apparatus can be operated stably over a prolonged period. The diffuser apparatus according to the present invention includes: an aeration plate 4 that is disposed in an aeration tank 12 in order to release pressurized air, fed from a diffusing air feed pipe 3, as air bubbles from fine pores formed in an aeration plate surface 4a; blow water feeding means 5 for feeding blow water into the diffusing air feed pipe 3; and an inserted pipe 7 for discharging the blow water, fed into the diffusing air feed pipe 3, from the aeration plate 4.

Abstract: A screw decanter centrifuge including a cylindrical bowl rotatable in one direction, a main drive motor coupled to the bowl for rotatably driving the bowl, a screw conveyor which is disposed concentrically in the bowl and which is rotatable in the same direction as the bowl at a differential rotation speed from the bowl, and an induction type screw conveyor motor for driving the screw conveyor. The differential rotation speed is changed in response to a carrying torque of the screw conveyor. An induction type screw conveyor motor is provided for driving the screw conveyor. The induction type screw conveyor motor has a shaft connected directly to, or coupled to, a shaft of the screw conveyor, and the induction type screw conveyor motor is controlled by a speed-torque controller.