Wastewater treatment apparatus and wastewater treatment method

Abstract

The present invention provides a wastewater treatment device and a wastewater treatment method that can minimize the installation space required. [Solution] The wastewater treatment device 10 is equipped with a coagulation and sedimentation tank 13 that stirs the wastewater, coagulates solid components in the wastewater, and precipitates solid components by changing the discharge flow rate of the wastewater mixed with a coagulant G.

Description

Technical Field

[0001] The present disclosure relates to a wastewater treatment apparatus and a wastewater treatment method.

Background Art

[0002] Patent Document 1 discloses a wastewater treatment apparatus. This apparatus includes a high-speed stirring tank that stirs treated water with a flocculant added to raw water at high speed, a low-speed stirring tank that stirs the treated water stirred in the high-speed stirring tank at a lower speed than the high-speed stirring tank to grow flocs, and a sedimentation tank that precipitates the flocs from the treated water containing the flocs treated in the low-speed stirring tank.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the apparatus of Patent Document 1, since each tank is arranged side by side, the installation space becomes large.

[0005] The present disclosure has been made in view of the above conventional situation, and an object to be solved is to provide a wastewater treatment apparatus and a wastewater treatment method capable of reducing the installation space.

Means for Solving the Problems

[0006] The wastewater treatment apparatus according to the first disclosure includes a coagulation sedimentation tank that performs stirring of the wastewater, aggregation of solid components in the wastewater, and precipitation of the solid components by changing the discharge flow rate of the wastewater mixed with a flocculant.

[0007] The wastewater treatment method of the second disclosure involves stirring the wastewater in a coagulation and sedimentation tank by changing the discharge flow rate of the wastewater mixed with a coagulant, thereby coagulating the solid components in the wastewater and causing the solid components to settle. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram of a waste disposal system. [Figure 2] This is a schematic diagram showing the wastewater treatment apparatus of Embodiment 1. [Figure 3] This is a partially enlarged perspective view showing the first and second covers attached to the discharge port of the coagulation and sedimentation tank. [Figure 4] This is a plan view showing a coagulation and sedimentation tank. [Figure 5] This is a time chart illustrating an example of the coordinated operation between a sewage treatment system and a wastewater treatment system. [Figure 6] This is a time chart illustrating another example of the coordinated operation between a sewage treatment system and a wastewater treatment system. [Modes for carrying out the invention]

[0009] First, embodiments of this disclosure will be listed and described. Any combination of the following embodiments, without causing any inconsistency, is also included as a form for carrying out the invention.

[0010] [1] The wastewater treatment apparatus of the present disclosure comprises a coagulation-settling tank that stirs the wastewater, coagulates solid components in the wastewater, and settles the solid components by changing the discharge flow rate of the wastewater mixed with a coagulant. Since this wastewater treatment apparatus can perform stirring of the wastewater and coagulant, coagulation of solid components in the wastewater, and settling of solid components in a single coagulation-settling tank, the installation space can be kept small.

[0011] [2] In the wastewater treatment apparatus described in [1] above, the coagulation and sedimentation tank has a discharge section for discharging the wastewater, the discharge section discharges the wastewater at a first discharge flow rate when stirring the wastewater, and discharges the wastewater at a second discharge flow rate when coagulating the solid components in the wastewater, the second discharge flow rate being less than the first discharge flow rate. This wastewater treatment apparatus makes it possible to promote the coagulation reaction of solid components without breaking down the coagulated solid components by setting the discharge flow rate of the wastewater to a second discharge flow rate which is less than the first discharge flow rate when coagulating the solid components in the wastewater.

[0012] [3] In the wastewater treatment apparatus described in [2] above, the discharge unit has two discharge ports for discharging the wastewater into the coagulation and sedimentation tank, and the discharge directions of the wastewater discharged from each discharge port are opposite. This wastewater treatment apparatus can generate turbulence between the flow of wastewater discharged from the two discharge ports, and this turbulence makes it possible to thoroughly mix the wastewater and the coagulant.

[0013] [4] In the wastewater treatment apparatus described in any of [1] to [3] above, the coagulation and sedimentation tank has a discharge port, and comprises a first cover that protrudes from the side wall of the coagulation and sedimentation tank located above the discharge port and is positioned above and in front of the discharge port, and a second cover that extends from the first cover toward the side wall so as to surround the lower half of the discharge port. In this wastewater treatment apparatus, when solid components descend and settle, the first cover prevents the solid components from entering the discharge port, and when wastewater excluding solid components is discharged from the discharge port, the second cover prevents the settled solid components from being caught in the flow of wastewater into the discharge port, while the wastewater excluding solid components is discharged.

[0014] [5] The wastewater treatment method of the present disclosure involves stirring the wastewater mixed with a coagulant in a coagulation-settling tank by changing the discharge flow rate of the wastewater, thereby coagulating the solid components in the wastewater and allowing the solid components to settle. Since this wastewater treatment method can perform stirring of the wastewater and coagulant, coagulation of solid components in the wastewater, and settling of solid components in a single coagulation-settling tank, the installation space can be kept small.

[0015] [6] In the wastewater treatment method described in [5] above, the coagulation and sedimentation tank has a discharge section for discharging the wastewater, the discharge section discharges the wastewater at a first discharge flow rate to agitate the wastewater, and discharges the wastewater at a second discharge flow rate less than the first discharge flow rate to coagulate the solid components in the wastewater. This wastewater treatment method makes it possible to promote the coagulation reaction of solid components without breaking down the coagulated solid components by setting the discharge flow rate of the wastewater to a second discharge flow rate less than the first discharge flow rate when coagulating the solid components in the wastewater in the coagulation and sedimentation tank.

[0016] [7] In the wastewater treatment method described in [6] above, the discharge unit has two discharge ports for discharging the wastewater into the coagulation and sedimentation tank, and each of the discharge ports discharges the wastewater in opposite directions. This wastewater treatment method can generate turbulence between the flow of wastewater discharged from the two discharge ports, and this turbulence makes it possible to thoroughly mix the wastewater and the coagulant.

[0017] <Embodiment 1> Embodiment 1, which embodies the wastewater treatment apparatus and wastewater treatment method of the present disclosure, will be described with reference to the drawings. The wastewater treatment apparatus 10 of Embodiment 1 has the function of removing solid components such as fine fiber debris and fine polymers contained in the wastewater discharged from the sewage treatment apparatus 90 to produce treated water.

[0018] [Configuration of waste disposal system] The waste treatment device 90 is a device that performs a process for disposing of used sanitary products such as disposable diapers D. Sanitary products include disposable diapers, napkins, pet sheets, and the like. For example, as shown in FIG. 1, the disposable diaper D contains a super absorbent polymer P (SAP, super absorbent polymer, hereinafter also simply referred to as polymer P) and pulp in a sheet material S such as a non-woven fabric. The sheet material S has a surface layer material made of a non-woven fabric made of polypropylene or the like and a waterproof material made of a resin material such as polyethylene. Pulp and polymer are sandwiched between the surface layer material and the waterproof material. The pulp and the polymer P have a water absorption performance of absorbing moisture of dirt such as urine and a water retention performance of maintaining the state of absorbing moisture. The particle size of the polymer P before absorbing moisture is 150 to 600 μm, and the density is greater than that of water. The polymer P that has absorbed moisture swells and becomes gel-like, and the particle size of the polymer P in the water absorption state is 600 μm to 4 mm.

[0019] The waste treatment device 90 crushes the disposable diaper D and separates water (also referred to as water separation) from the polymer P that has absorbed moisture using a treatment liquid T in which a water separating agent R (for example, calcium chloride) is dissolved in water. Then, the treatment liquid T used when separating water from the polymer P, the water separated from the polymer P, and the like are discharged as drainage and separated from solid matters such as the sheet material S and the polymer P.

[0020] As shown in FIG. 1, the waste treatment device 90 includes an input unit 91, a crushing device 92, a water separation treatment device 93, a control unit 94, and a dehydration device 95.

[0021] The input unit 91 has a box shape with an open bottom surface. The input unit 91 is provided with an input port 91A. The input port 91A is provided with a lid 91B that can be opened and closed from the outside of the input unit 91. The disposable diaper D can be input into the input unit 91 through the input port 91A.

[0022] The input section 91 is equipped with an input sensor 91C that detects when a disposable diaper D is inserted through the input opening 91A. For example, the input sensor 91C transmits a detection signal to the control unit 94 each time a disposable diaper D is inserted. An operation unit is electrically connected to the control unit 94. However, the operation unit is not shown. The user of the waste disposal device 90 can start or stop the operation of the waste disposal device 90 and the wastewater disposal device 10, which will be described later, by operating this operation unit.

[0023] A deodorizing device 91D is provided on the upper surface of the input section 91. The deodorizing device 91D may use, for example, a known axial fan or a nonwoven fabric with activated carbon attached (a so-called deodorizing filter). The deodorizing device 91D uses an axial fan to draw in odors generated from the disposable diapers D that are put into the input section 91, sends them to the deodorizing filter for deodorization, and then discharges the deodorized air to the outside.

[0024] The crushing device 92 is a device for crushing the disposable diapers D that are fed into the input section 91. The crushing device 92 has a peripheral wall section 92A, a pair of left and right crushing members 92B, and a first water supply section 92C. The pair of left and right crushing members 92B are housed in the peripheral wall section 92A.

[0025] The left and right pair of crushing members 92B are cylindrical in shape as a whole, with their axes oriented in the front-rear direction. Each crushing member 92B has a rotating shaft 92E that is rotationally driven by a crushing motor 92D. The driving of the crushing motor 92D is controlled by a control unit 94. The left and right pair of crushing members 92B are arranged side by side with the axes of the rotating shafts 92E at the same height. Each crushing member 92B is provided with multiple disc-shaped shear blades 92F, the outer edges of which are formed to be uneven, arranged in the direction of the axis of the rotating shaft 92E. The multiple shear blades 92F on one crushing member 92B and the multiple shear blades 92F on the other crushing member 92B are arranged alternately in the direction of the axis of the rotating shaft 92E (not shown). Note that the number of crushing members 92B may be limited to one.

[0026] The first water supply unit 92C is positioned above the crushing member 92B within the peripheral wall 92A. Water is discharged into the peripheral wall 92A from the crushing space nozzle 92G of the first water supply unit 92C. The water discharged from the crushing space nozzle 92G pours onto the crushing member 92B from above. The water that pours onto the crushing member 92B flows down below the crushing member 92B, passing through the gaps between the shearing blades 92F, the gap between the shearing blades 92F and the rotating shaft 92E, and the gap between the shearing blades 92F and the peripheral wall 92A. The water supply operation of the first water supply unit 92C is controlled by the control unit 94.

[0027] The water release treatment device 93 has the function of separating water from polymer P by stirring crushed paper diapers D and a treatment liquid T in which a water release agent R is dissolved in water. The water release treatment device 93 comprises a treatment tank 93A, a stirring member 93B, a second water supply unit 93C, and a water release agent supply unit 93D. The treatment tank 93A is box-shaped. The lower end of the peripheral wall 92A is connected to the upper surface of the treatment tank 93A.

[0028] A circular outlet 93E is formed on the left side wall of the processing tank 93A. After the water separation treatment is completed in the processing tank 93A, the crushed pieces F, polymer P, and processing liquid T inside the processing tank 93A are discharged to the outside of the processing tank 93A through the outlet 93E and sent to the dewatering device 95 via the discharge passage 93F.

[0029] The stirring member 93B is provided on the bottom surface of the processing tank 93A. The stirring member 93B is rotationally driven by a stirring motor 93G having a vertical drive shaft. The stirring member 93B has a disc-shaped main body 93H from which multiple ribs 93J protrude upward. Each rib 93J extends radially from the main body 93H.

[0030] The drive of the stirring motor 93G is controlled by the control unit 94. During the water separation process, the stirring member 93B is rotated alternately in the forward direction (one direction) and the reverse direction (other direction) by the control unit 94. After the water separation process, the crushed pieces F containing polymer P and the processing liquid T from the processing tank 93A are discharged from the discharge port 93E.

[0031] The second water supply unit 93C has a first nozzle 93K and a second nozzle 93L attached to the treatment tank 93A. The first nozzle 93K and the second nozzle 93L are located on the right wall opposite the left wall. The first nozzle 93K is positioned to discharge water toward the stirring member 93B. The second nozzle 93L is positioned to discharge water toward the outlet 93E. The discharge and stopping of water from the first nozzle 93K and the second nozzle 93L are controlled by the control unit 94.

[0032] The water-removing agent supply unit 93D is attached to the processing tank 93A. The water-removing agent supply unit 93D supplies a predetermined amount of the water-removing agent R described above into the processing tank 93A. The supply operation and amount of water-removing agent R are controlled by the control unit 94. The discharge port 93E of the processing tank 93A is connected to the dewatering device 95 via the discharge passage 93F.

[0033] A shut-off valve 93M is provided in the middle of the discharge passage 93F to open and close the discharge passage 93F. For example, an electric ball valve is used for the shut-off valve 93M. When the shut-off valve 93M is open, the crushed pieces F and processing liquid T in the processing tank 93A flow into the dewatering device 95 through the discharge port 93E and the discharge passage 93F. When the shut-off valve 93M is closed, the crushed pieces F and processing liquid T in the processing tank 93A do not flow out into the dewatering device 95, but remain in the processing tank 93A. The opening and closing operation of the shut-off valve 93M is controlled by the control unit 94.

[0034] A known screw press is used in the dewatering device 95. The crushed pieces F and processing liquid T that flow from the processing tank 93A to the dewatering device 95 via the discharge passage 93F pass through the dewatering filter 95C by a screw 95B that is rotationally driven by the dewatering motor 95A. The crushed pieces F pass through the dewatering filter 95C by the screw 95B, fall through the outlet section 95D and are collected from the recovery port 95E. The processing liquid T flows down to the water collection section 95F while passing through the dewatering filter 95C, and flows as wastewater through the discharge port 95G and the inlet pipe 12C into the primary stock tank 12 of the wastewater treatment device 10, which will be described later.

[0035] The control unit 94 is configured, for example, as a microcomputer. The control unit 94 receives a detection signal from the input sensor 91C. Based on the detection signal from the input sensor 91C, operations on an operation unit (not shown), etc., the control unit 94 can control various operations such as the operation of the axial flow fan of the deodorizer 91D, the driving of the crushing motor 92D, the water supply operations of the first water supply unit 92C and the second water supply unit 93C, the operation of the stirring motor 93G, the supply operation of the water release agent R by the water release agent supply unit 93D, the opening and closing operation of the on-off valve 93M, and the operation of the dewatering motor 95A. Furthermore, the control unit 94 can control various operations of the wastewater treatment device 10, which will be described later, such as the coagulant supply unit 13C, the solenoid valve 13K, the pair of pumps 14A and 14B, the pumping pump 16A, the discharge pump 17D, the return pump 19A, and the on-off valve 20C.

[0036] [Configuration of wastewater treatment equipment] The wastewater treatment device 10 removes fine fibrous debris and fine polymers P contained in the wastewater discharged from the sewage treatment device 90 by coagulating them using a coagulant. Here, the coagulant is a chemical agent used to coagulate substances contained in the wastewater. For example, inorganic coagulants and polymer coagulants are used. As shown in Figure 2, the wastewater treatment device 10 includes a storage rack 11, a primary stock tank 12, a coagulation and sedimentation tank 13, a first cover 13D (see Figure 3), a second cover 13E (see Figure 3), a primary recovery filter 15, piping 16, a secondary stock tank 17, a secondary recovery filter 18, a discharge pipe 19, and a ventilation pipe 20.

[0037] The storage rack 11 consists of three racks 11A arranged vertically by support columns 11B. Multiple casters 11C are provided at the lower end of the storage rack 11. Each rack 11A is fitted with one primary stock tank 12, one coagulation and sedimentation tank 13, and one secondary stock tank 17, which will be described later.

[0038] The primary stock tank 12 is, for example, a box shaped like a rectangular parallelepiped or a cylinder, into which wastewater discharged from the sewage treatment device 90 flows in and is stored via an inlet 12B provided at the lower end of the side wall. The primary stock tank 12 is provided with a lid 12A. The primary stock tank 12 is sealed by placing the lid 12A on top. This prevents odors generated from the stored wastewater from leaking to the outside. The primary stock tank 12 is placed on the lowest shelf 11A of the storage shelf 11. The downstream end of the inlet pipe 12C is connected to the inlet 12B. The upstream end of the inlet pipe 12C is connected to the outlet 95G of the dewatering device 95 (see Figure 1). Wastewater flows into the primary stock tank 12 via the outlet 95G of the dewatering device 95 and the inlet pipe 12C. The primary stock tank 12 stores wastewater discharged from the sewage treatment device 90.

[0039] The coagulation and sedimentation tank 13 is, for example, a box shaped like a rectangular parallelepiped or a cylinder. The coagulation and sedimentation tank 13 has the function of adding a coagulant to the wastewater flowing in from the primary stock tank 12, stirring the wastewater and coagulating and settling the fine fiber debris and fine polymer P, which are solid components contained in the wastewater. The coagulation and sedimentation tank 13 is provided with a lid 13A. The coagulation and sedimentation tank 13 can be sealed by placing the lid 13A on top. This suppresses the leakage of odors generated from the incoming wastewater to the outside, and also suppresses the outflow of wastewater when stirring the wastewater and coagulant. The coagulation and sedimentation tank 13 is placed on the third shelf 11A from the bottom of the shelves 11A in the storage rack 11. That is, the coagulation and sedimentation tank 13 is located above the primary stock tank 12.

[0040] An outlet 13B is provided at the lower end of the side wall of the coagulation and sedimentation tank 13. As shown in Figure 3, the outlet 13B is circular in shape. The lower end of the outlet 13B is located above the bottom wall of the coagulation and sedimentation tank 13 and is spaced apart from the bottom wall. As shown in Figure 2, a treated water discharge pipe 13J is connected to the outlet 13B. The treated water discharge pipe 13J is sealed and connected to the coagulation and sedimentation tank 13 and extends to the outside of the coagulation and sedimentation tank 13. A solenoid valve 13K is provided in the middle of the treated water discharge pipe 13J. For example, the solenoid valve 13K is controlled by the control unit 94.

[0041] The coagulation and sedimentation tank 13 is equipped with a coagulant supply unit 13C for supplying coagulant G to the coagulation and sedimentation tank 13. The coagulant supply unit 13C supplies a predetermined amount of coagulant G to the coagulation and sedimentation tank 13. The supply operation and amount of coagulant G in the coagulant supply unit 13C are controlled, for example, by a control unit 94.

[0042] The first cover 13D and the second cover 13E are integrally formed by three-dimensionally combining flat synthetic resin plates. As shown in Figure 3, the first cover 13D protrudes from the side wall of the coagulation and sedimentation tank 13, which is located above the outlet 13B, and is positioned above and in front of the outlet 13B. Specifically, the first cover 13D has an attachment portion 13L that is attached to the side wall of the coagulation and sedimentation tank 13, an overhang portion 13F that is connected to the lower edge of the attachment portion 13L and extends in an overhang shape from the side wall of the coagulation and sedimentation tank 13, and an opposing portion 13G that is connected to the protruding edge of the overhang portion 13F and extends downward to face the outlet 13B. The second cover 13E has an upward-opening rectangular shape and extends from the lower end of the opposing portion 13G of the first cover 13D toward the side wall of the coagulation and sedimentation tank 13 so as to surround the lower half of the outlet 13B. The second cover 13E is connected to the lower edge and both side edges adjacent to the lower end of the opposing portion 13G. The edge of the second cover 13E that contacts the side wall of the coagulation and sedimentation tank 13 is provided with abutment piece 13H so as to make surface contact with the side wall of the coagulation and sedimentation tank 13. The abutment piece 13H is attached to the side wall of the coagulation and sedimentation tank 13. The upper end Te of the second cover 13E is located above the lower end of the opposing portion 13G. When the discharge port 13B is viewed from the front, the upper end Te coincides with the center Ce of the discharge port 13B.

[0043] The coagulation and sedimentation tank 13 has a discharge section 14. The discharge section 14 is provided inside the coagulation and sedimentation tank 13, as shown in Figure 4. For example, a pair of pumps 14A and 14B are used in the discharge section 14. Each pump 14A and 14B sucks up the wastewater mixed with the coagulant G from inside the coagulation and sedimentation tank 13 and discharges it from the discharge ports 14C and 14D, stirring the wastewater mixed with the coagulant G. That is, the discharge section 14 has two discharge ports 14C and 14D. When viewed from above, the pumps 14A and 14B are positioned at two diagonally opposite corners of the four corners of the coagulation and sedimentation tank 13. Each pump 14A and 14B is positioned slightly apart from the side wall of the coagulation and sedimentation tank 13. The discharge ports 14C and 14D of each pump 14A and 14B are positioned so that the discharge directions of the wastewater discharged from each discharge port 14C and 14D are parallel and opposite. In this context, "parallel" does not refer only to strictly parallel lines, but also to angles that deviate slightly from strictly parallel lines. The discharge direction of the wastewater discharged from the discharge port 14D of the pump 14B, which is positioned adjacent to the side wall opposite to the side wall where the discharge port 13B is formed, is directed toward the discharge port 13B.

[0044] For example, the discharge flow rate of wastewater discharged from the discharge ports 14C and 14D of the discharge unit 14 is controlled by the control unit 94. Specifically, the discharge flow rate of wastewater discharged from the discharge ports 14C and 14D of the discharge unit 14 is changed by the control unit 94 between a first discharge flow rate and a second discharge flow rate that is less than the first discharge flow rate.

[0045] As shown in Figure 2, the primary recovery filter 15 is connected to the downstream end of the treated water discharge pipe 13J that extends outside the coagulation and sedimentation tank 13. When wastewater flows in from the coagulation and sedimentation tank 13, the primary recovery filter 15 collects the solid components that have coagulated and settled in the coagulation and sedimentation tank 13. After the wastewater passes through the primary recovery filter 15, the solid components are removed, and it becomes treated water. The treated water flows into the secondary stock tank 17, which will be described later. The primary recovery filter 15 has a filter body 15A and a retaining cylinder 15B that holds the filter body 15A. For example, the filter body 15A is made of a mesh-like material (nonwoven fabric or net, etc.) formed in a bag shape. The retaining cylinder 15B is formed in a cylindrical shape, and the opening of the filter body 15A is connected to it. The retaining cylinder 15B has the function of maintaining the outer shape of the opening of the filter body 15A in a cylindrical shape. The retaining cylinder 15B is connected to the downstream end of the treated water discharge pipe 13J. The primary recovery filter 15 is located inside the secondary stock tank 17, which will be described later. For example, the treated water discharge pipe 13J is provided through the lid 17A of the secondary stock tank 17. For example, the space between the treated water discharge pipe 13J and the lid 17A is sealed. That is, the treated water discharge pipe 13J is sealed and connected to the secondary stock tank 17.

[0046] Pipe 16 transports wastewater stored in the primary stock tank 12 to the coagulation and sedimentation tank 13. The upstream end of pipe 16 is located at the lower end of the primary stock tank 12. A pump 16A is connected to the upstream end of pipe 16. The downstream end of pipe 16 extends into the coagulation and sedimentation tank 13, straddling the upper end of the side wall of the tank. The downstream end of pipe 16 is located at the lower end of the coagulation and sedimentation tank 13. An outlet 16B is formed at the downstream end of pipe 16. That is, the outlet 16B of pipe 16 is located at the lower end of the coagulation and sedimentation tank 13. For example, pipe 16 is installed through the lid 12A of the primary stock tank 12 and the lid 13A of the coagulation and sedimentation tank 13. For example, the space between pipe 16 and lid 12A, and the space between pipe 16 and lid 13A are sealed. In other words, the piping 16 is sealed and connected to both the primary stock tank 12 and the coagulation and sedimentation tank 13.

[0047] Within the coagulation and sedimentation tank 13, the piping 16 upstream of the discharge port 16B extends above the maximum liquid level L in the coagulation and sedimentation tank 13. Here, the maximum liquid level L is the water level of the wastewater when a quantity of wastewater that can efficiently be stirred is introduced into the coagulation and sedimentation tank 13. An air intake hole 16C is formed through the piping 16 above the maximum liquid level L in the coagulation and sedimentation tank 13. The air intake hole 16C is located below the lid 13A when the lid 13A is placed on the coagulation and sedimentation tank 13. When the pump 16A is activated, the wastewater stored in the primary stock tank 12 flows into the coagulation and sedimentation tank 13 via the piping 16. When the pump 16A stops operating, air flows into the piping 16 via the air intake hole 16C. Then, the wastewater in the piping 16 downstream of the air intake hole 16C flows directly into the coagulation and sedimentation tank 13. Drainage in the piping 16 upstream of the intake port 16C returns to the primary stock tank 12. In other words, the siphon effect in piping 16 is suppressed by the intake port 16C. For example, the operation of the pumping pump 16A is controlled by the control unit 94.

[0048] The secondary stock tank 17 is, for example, a box shaped like a rectangular parallelepiped or a cylinder. Treated water, from which at least some of the solid components have been removed from the wastewater discharged from the coagulation and sedimentation tank 13 by the primary recovery filter 15, flows into the secondary stock tank 17. The secondary stock tank 17 can store the treated water. The secondary stock tank 17 is provided with a lid 17A. The secondary stock tank 17 is sealed by placing the lid 17A on top. This prevents odors generated from the stored treated water from leaking to the outside. The secondary stock tank 17 is placed on the second-to-last shelf 11A of the shelves 11A in the storage rack 11. That is, the secondary stock tank 17 is located above the primary stock tank 12 and below the coagulation and sedimentation tank 13. An outlet 17C is provided at the lower end of the side wall of the secondary stock tank 17.

[0049] A discharge pump 17D, connected to the discharge port 17C, is located on the outside of the secondary stock tank 17. A secondary recovery filter 18, described later, is connected downstream of the discharge pump 17D. The discharge pump 17D has the function of sending the treated water stored in the secondary stock tank 17 to the secondary recovery filter 18. For example, if the amount of treated water flowing into the secondary recovery filter 18 per unit time is specified, the discharge pump 17D is provided to send the treated water to the secondary recovery filter 18 at a predetermined inflow rate that does not exceed this specified amount.

[0050] The secondary recovery filter 18 is provided, for example, so as to protrude from the outside of the storage shelf 11. The secondary recovery filter 18 is connected to the downstream side of the secondary stock tank 17. A known filtration device is used for the secondary recovery filter 18. The secondary recovery filter 18 has a case 18A and a filter medium 18B housed in the case 18A. Treated water stored in the secondary stock tank 17 flows into the secondary recovery filter 18 at a predetermined rate by the discharge pump 17D. The secondary recovery filter 18 captures fine solid components that were not captured by the primary recovery filter 15 and which flowed into the secondary stock tank 17 mixed with the treated water. In other words, the secondary recovery filter 18 has a higher solid component filtration capacity than the primary recovery filter 15.

[0051] The discharge pipe 19 discharges the treated water stored in the secondary stock tank 17 to the coagulation and sedimentation tank 13. The upstream end of the discharge pipe 19 is located at the lower end of the secondary stock tank 17. A return pump 19A is connected to the end of the discharge pipe 19 located inside the secondary stock tank 17. The discharge pipe 19 extends from the secondary stock tank 17, crosses the upper end of the side wall of the coagulation and sedimentation tank 13, and extends into the coagulation and sedimentation tank 13. In other words, the discharge pipe 19 is connected to the coagulation and sedimentation tank 13. An outlet 19B is formed at the downstream end of the discharge pipe 19. The outlet 19B of the discharge pipe 19 is located at the lower end of the coagulation and sedimentation tank 13. Inside the coagulation and sedimentation tank 13, the portion of the discharge pipe 19 upstream of the outlet 19B extends above the highest liquid level L in the coagulation and sedimentation tank 13. An air intake hole 19C is formed through the discharge pipe 19 above the highest liquid level L in the coagulation and sedimentation tank 13. The air intake hole 19C is located below the lid 13A when the lid 13A is placed on the coagulation and sedimentation tank 13. For example, the discharge pipe 19 is provided to pass through the lid 17A of the secondary stock tank 17 and the lid 13A of the coagulation and sedimentation tank 13. For example, the space between the discharge pipe 19 and the lid 17A, and the space between the discharge pipe 19 and the lid 13A are sealed. When the return pump 19A is driven, the treated water stored in the secondary stock tank 17 flows into the coagulation and sedimentation tank 13 via the discharge pipe 19. When the operation of the return pump 19A stops, air flows into the discharge pipe 19 via the air intake hole 19C. Then, the treated water in the discharge pipe 19 downstream of the air intake hole 19C flows directly into the coagulation and sedimentation tank 13. The treated water in the discharge pipe 19 upstream of the intake port 19C returns to the secondary stock tank 17. In other words, the siphon effect in the discharge pipe 19 is suppressed by the intake port 19C. For example, the operation of the return pump 19A is controlled by the control unit 94.

[0052] The ventilation piping 20 has a base pipe 20A and a number of branch pipes 20B that branch off from the base pipe 20A. The lower end of the base pipe 20A is airtightly connected to the lid 12A of the primary stock tank 12. Each branch pipe 20B is airtightly connected to the lid 13A of the coagulation and sedimentation tank 13 and the lid 17A of the secondary stock tank 17. In other words, the ventilation piping 20 is sealedly connected to the primary stock tank 12, the coagulation and sedimentation tank 13, and the secondary stock tank 17. An on-off valve 20C is provided in the base pipe 20A. For example, the on-off valve 20C is controlled by the control unit 94.

[0053] When the wastewater treatment device 10 is viewed from the side, the primary stock tank 12, the coagulation and sedimentation tank 13, and the secondary stock tank 17 are positioned offset from each other laterally (see Figure 2). This makes it easier to see the inside of the primary stock tank 12 with the lid 12A removed, and the inside of the secondary stock tank 17 with the lid 17A removed, from above.

[0054] [About the operation of wastewater treatment equipment] The on-off valve 20C of the ventilation pipe 20 and the solenoid valve 13K of the treated water discharge pipe 13J are in a closed state. The primary stock tank 12 can store the wastewater from multiple operations of the waste treatment device 90. For example, the control unit 94 is capable of determining whether the water level of the wastewater in the primary stock tank 12 has reached the maximum storage level. When the control unit 94 determines that the water level of the wastewater in the primary stock tank 12 is at the maximum storage level, it puts diapers D into the waste treatment device 90 and operates the pump 16A to transport the wastewater from the primary stock tank 12 to the coagulation and sedimentation tank 13 via the piping 16. For example, the control unit 94 uses the pump 16A to transport the amount of wastewater from the primary stock tank 12 to the coagulation and sedimentation tank 13 equal to the amount of wastewater that flows into the primary stock tank 12 when the waste treatment device 90 operates once. At this time, the air inside the coagulation and sedimentation tank 13 is pushed out of the tank by the incoming wastewater and flows into the primary stock tank 12 via the ventilation pipe 20.

[0055] Once the transfer of wastewater from the primary stock tank 12 to the coagulation and sedimentation tank 13 is complete, the control unit 94 stops the operation of the pump 16A. Then, the control unit 94 operates the coagulant supply unit 13C to supply a predetermined amount of coagulant G into the coagulation and sedimentation tank 13, and starts the operation of the pumps 14A and 14B of the discharge unit 14.

[0056] First, the control unit 94 controls the operation of pumps 14A and 14B to discharge wastewater at a first discharge flow rate from discharge ports 14C and 14D. When pumps 14A and 14B start operating, as shown in Figure 4, pumps 14A and 14B draw in the wastewater supplied with the coagulant G and discharge it as a discharge flow Fd from each of the discharge ports 14C and 14D. The discharge directions of each discharge flow Fd at discharge ports 14C and 14D are parallel and opposite. Each discharge flow Fd travels in a straight line toward the side wall of the opposing coagulation and sedimentation tank 13. Around the two discharge flows Fd (the area enclosed by the dashed line in Figure 4), the wastewater is agitated in a turbulent flow. The discharge flow Fd discharged from the discharge port 14D of pump 14B flows toward the outlet 13B and hits the opposing part 13G of the first cover 13D which is positioned opposite the outlet 13B (see Figure 3). This prevents the discharge flow Fd from flowing directly into the treated water discharge pipe 13J, and prevents solid components from entering the treated water discharge pipe 13J. Each discharge flow Fd changes direction when it reaches the side wall, spreading out along the side wall. The discharge flow Fd that spreads laterally along the side wall to the region outside the two discharge flows Fd forms vortices V in each of the regions outside the two discharge flows Fd. The discharge flow Fd that spreads upward along the side wall enhances the turbulence formed between the two discharge flows Fd.

[0057] When the coagulant G is discharged from the discharge ports 14C and 14D along with the wastewater at a first discharge flow rate and mixed with the wastewater, a coagulation reaction begins in which fine solid components agglomerate around the coagulant G mixed in the wastewater to form coagulated particles. After the control unit 94 has been discharging the wastewater from the discharge ports 14C and 14D at the first discharge flow rate for a predetermined time, it temporarily stops the operation of the pumps 14A and 14B. Subsequently, the control unit 94 restarts the operation of the pumps 14A and 14B so that the discharge flow rate of the wastewater from the discharge ports 14C and 14D is reduced to a second discharge flow rate, which is less than the first discharge flow rate.

[0058] The second discharge flow rate is less than the first discharge flow rate. Therefore, compared to the first discharge flow rate, when wastewater is discharged from the discharge ports 14C and 14D at the second discharge flow rate, the flow of wastewater in the coagulation and sedimentation tank 13 becomes slower. This allows the wastewater mixed with the coagulant G to be agitated while preventing the coagulated particles from breaking down by discharging the wastewater from the discharge ports 14C and 14D at the second discharge flow rate. As a result, in the coagulation and sedimentation tank 13, the coagulated particles aggregate to form larger clumps (coagulated particle clumps). In other words, when wastewater is discharged from the discharge ports 14C and 14D at the second discharge flow rate, the coagulation of solid components in the wastewater progresses and grows into coagulated particle clumps. Thus, the discharge section 14 agitates the wastewater at the first discharge flow rate and then coagulates the solid components in the wastewater at the second discharge flow rate, which is less than the first discharge flow rate, to form coagulated particle clumps. These grown coagulated particle clumps mainly accumulate in the vortex flow V and the surrounding region A (the region indicated by a collection of multiple points).

[0059] The control unit 94 discharges wastewater from the discharge ports 14C and 14D at the second discharge flow rate for a predetermined time, and then stops the operation of the pumps 14A and 14B. This stops the flow of wastewater in the coagulation and sedimentation tank 13, and promotes the sedimentation of the grown coagulated granules. The first cover 13D prevents the sedimenting coagulated granules from entering the inside of the second cover 13E. In this way, the coagulation and sedimentation tank 13 stirs the wastewater, coagulates fine solid components in the wastewater, grows the solid components into coagulated granules, and settles the coagulated granules by changing the discharge flow rate discharged by the discharge unit 14, which sucks in the wastewater mixed with the coagulant G, to the first discharge flow rate, the second discharge flow rate, and 0.

[0060] The control unit 94 keeps the pumps 14A and 14B stopped for a predetermined period of time, and then opens the solenoid valve 13K. At this time, the coagulated particles that have settled in the coagulation and sedimentation tank 13 accumulate below the upper end Te of the second cover 13E. As a result, the coagulated particles are prevented from entering the outlet 13B of the coagulation and sedimentation tank 13 by the second cover 13E. Then, the supernatant water in the coagulation and sedimentation tank 13 flows into the treated water discharge pipe 13J from between the first cover 13D and the outlet 13B (see Figure 3). At this time, some of the coagulated particles flow into the treated water discharge pipe 13J together with the supernatant water. The coagulated particles that flow into the treated water discharge pipe 13J are collected by the primary recovery filter 15 (see Figure 2). The supernatant water that has passed through the primary recovery filter 15 is stored in the secondary stock tank 17 as treated water. Thus, in the coagulation and sedimentation tank 13, the wastewater treatment device 10 uses a discharge flow Fd, which is drawn in by the discharge unit 14 and discharged, to coagulate and settle the solid components in the wastewater, thereby producing treated water from which at least a portion of the solid components have been removed. At this time, the air in the secondary stock tank 17 is pushed out of the secondary stock tank 17 by the incoming treated water and flows into the coagulation and sedimentation tank 13 via the ventilation pipe 20 (see Figure 2).

[0061] For example, the control unit 94 is configured to detect that the water level of the wastewater in the coagulation and sedimentation tank 13 does not fall below the upper end of the outlet 13B. When the control unit 94 detects that the water level of the wastewater in the coagulation and sedimentation tank 13 is approaching the upper end of the outlet 13B, it closes the solenoid valve 13K. The coagulated granules accumulated at the bottom of the coagulation and sedimentation tank 13 are recovered during periodic maintenance operations of the wastewater treatment device 10. A maintenance operation is an operation to clean the coagulation and sedimentation tank 13. Specifically, a maintenance operation involves starting the return pump 19A, discharging the treated water stored in the secondary stock tank 17 via the discharge pipe 19 into the coagulation and sedimentation tank 13, gently stirring the water so as not to break the coagulated granules accumulated at the bottom of the coagulation and sedimentation tank 13, and then opening the solenoid valve 13K to recover the coagulated granules with the primary recovery filter 15.

[0062] For example, the control unit 94 starts the operation of the discharge pump 17D in conjunction with the start of operation of the dewatering device 95 of the waste treatment device 90. That is, the treated water is discharged from the secondary stock tank 17 in conjunction with the timing when wastewater flows from the dewatering device 95 into the primary stock tank 12. Then, the treated water stored in the secondary stock tank 17 is transported to the secondary recovery filter 18 by the discharge pump 17D. When the treated water flows into the secondary recovery filter 18, fine aggregate particles that were not captured by the primary recovery filter 15 and have mixed into the treated water are collected by the filter media 18B. Then, the treated water from which the fine aggregate particles have been removed passes through the secondary recovery filter 18 and is discharged. The treated water that has passed through the secondary recovery filter 18 is discharged, for example, into a sewer system. At this time, as the treated water flows from the secondary stock tank 17 to the secondary recovery filter 18, air flows from the primary stock tank 12 to the secondary stock tank 17 via the ventilation pipe 20 (see Figure 2). This allows the treated water to be smoothly delivered from the secondary stock tank 17 to the secondary recovery filter 18.

[0063] For example, by operating an operating unit (not shown) connected to the control unit 94, the control unit 94 can also maintain the state in which treated water is stored in the secondary stock tank 17 without operating the discharge pump 17D. In this case, when wastewater flows into the primary stock tank 12, the on-off valve 20C is opened to release the air pushed out from the primary stock tank 12. Then, when the inflow of wastewater into the primary stock tank 12 ends, the on-off valve 20C is closed. For example, by operating an operating unit (not shown), the control unit 94 can start the operation of the return pump 19A and discharge the treated water stored in the secondary stock tank 17 to the coagulation and sedimentation tank 13 via the discharge pipe 19. At this time, the air in the coagulation and sedimentation tank 13 is pushed out of the coagulation and sedimentation tank 13 by the incoming treated water and flows into the secondary stock tank 17 via the ventilation pipe 20 (see Figure 2).

[0064] [An example of coordinated operation between a sewage treatment system and a wastewater treatment system] For example, if the bottom area of ​​each tank is the same, when the wastewater generated by one operation of the sewage treatment device 90 is stored in the primary stock tank 12, the water level of the wastewater in the primary stock tank 12 will be approximately 100 mm. Note that the minimum water level at which each tank can be operated is set to 0 mm. For example, the primary stock tank 12 can store wastewater until the water level reaches approximately 300 mm. In other words, the primary stock tank 12 can store the wastewater from three operations of the sewage treatment device 90.

[0065] For example, as shown in Figure 5, assuming that the waste treatment device 90 has already operated three times and wastewater is stored in the primary stock tank 12 at a water level of approximately 300 mm, a disposable diaper D is put into the input section 91 of the waste treatment device 90 at time T1. Then, at time T1, the control unit 94 starts the operation of the pump 16A and transports the wastewater in the primary stock tank 12 to the coagulation and sedimentation tank 13. The amount of wastewater transported at this time is the same as the amount of wastewater when the waste treatment device 90 is operated once. As a result, the water level of the wastewater in the primary stock tank 12 decreases from approximately 300 mm to approximately 200 mm. At the same time, the water level of the wastewater in the coagulation and sedimentation tank 13 rises from 0 mm to approximately 100 mm.

[0066] At time T2, the control unit 94 crushes the disposable diapers D that have been fed into the input unit 91 by the crushing device 92. At the same time, the control unit 94 starts the operation of the pumps 14A and 14B of the discharge unit 14 located in the coagulation and sedimentation tank 13, and discharges the wastewater at the first discharge flow rate. As a result, in the coagulation and sedimentation tank 13, a coagulation reaction begins in which fine solid components coagulate around the coagulant G mixed in the wastewater to form coagulated particles.

[0067] At time T3, the control unit 94 starts a water separation process to separate water from the polymer P by stirring the crushed paper diaper D in the water separation treatment device 93 with the treatment liquid T, which is obtained by dissolving the water separation agent R in water. At the same time, the control unit 94 stops the operation of the pumps 14A and 14B of the discharge unit 14.

[0068] At time T4, the control unit 94 starts the operation of pumps 14A and 14B and discharges wastewater at the second discharge flow rate. This promotes the aggregation of aggregated particles in the coagulation and sedimentation tank 13, facilitating the formation of larger clumps (aggregated particle clumps). At time T5, the control unit 94 stops the operation of pumps 14A and 14B. From time T5 onward, the sedimentation of the aggregated particle clumps is accelerated.

[0069] At time T6, the control unit 94 rotates the stirring member 93B alternately in the forward and reverse directions to agitate the treatment liquid T in the treatment tank 93A, thereby rinsing the inner wall of the treatment tank 93A with the treatment liquid T.

[0070] At time T7, the control unit 94 opens the solenoid valve 13K installed in the treated water discharge pipe 13J, transporting the supernatant water from the coagulation and sedimentation tank 13 to the secondary stock tank 17. The primary recovery filter 15 collects the coagulated particles (solid components) that are slightly mixed in with the supernatant water. As a result, the water level of the wastewater in the coagulation and sedimentation tank 13 drops from approximately 100 mm to 0 mm. The accumulated coagulated particles remain at the bottom of the coagulation and sedimentation tank 13. At the same time, the water level of the wastewater in the secondary stock tank 17 rises from 0 mm to approximately 100 mm.

[0071] At time T8, the control unit 94 opens the on-off valve 93M, allowing the crushed fragments F containing the polymer P after the water separation treatment and the treated liquid T to flow from the treatment tank 93A into the dewatering device 95. The control unit 94 then starts the operation of the dewatering motor 95A to begin separating the crushed fragments F from the treated liquid T. As a result, the treated liquid T separated from the crushed fragments F flows into the primary stock tank 12 as wastewater and is stored there. At the same time, the control unit 94 operates the discharge pump 17D to begin transporting the treated water from the secondary stock tank 17 to the secondary recovery filter 18. The treated water stored in the secondary stock tank 17 is then discharged into the sewer from the secondary recovery filter 18. From time T8 onward, the inflow of wastewater into the primary stock tank 12 and the disposal of treated water from the secondary recovery filter 18 into the sewer are carried out in parallel. Specifically, the water level of the wastewater in the primary stock tank 12 gradually rises. Simultaneously, the water level of the treated water in the secondary stock tank 17 gradually decreases. At this time, the air in the primary stock tank 12 is pushed out by the incoming wastewater and flows into the secondary stock tank 17 via the ventilation pipe 20.

[0072] At time T9, the separation of the crushed fragments F and the treated liquid T in the dewatering device 95 is completed. Simultaneously, the transfer of treated water from the secondary stock tank 17 to the secondary recovery filter 18 is completed. At this time, the water level of the wastewater in the primary stock tank 12 is approximately 300 mm, and the water level of the treated water in the secondary stock tank 17 is 0 mm.

[0073] After time T9, the waste treatment device 90 may be kept off, and only the wastewater treatment device 10 may be operated to treat all the wastewater in the primary stock tank 12 into treated water before disposing of it into the sewer system. In this case, when the treated water is transported from the secondary stock tank 17 to the secondary recovery filter 18, the shut-off valve 20C of the ventilation pipe 20 is opened to supply air to the secondary stock tank 17.

[0074] [Another example of coordinated operation between a sewage treatment system and a wastewater treatment system] For example, if the bottom area of ​​each tank is the same, the wastewater treatment device 10 may be operated each time the waste treatment device 90 operates. Specifically, as shown in Figure 6, when the waste treatment device 90 operates once and wastewater is stored in the primary stock tank 12 at a water level of approximately 100 mm, a disposable diaper D is put into the input section 91 of the waste treatment device 90 at time T11. At the same time, the control unit 94 starts the operation of the pump 16A and transports the wastewater in the primary stock tank 12 to the coagulation and sedimentation tank 13. At this time, all the wastewater stored in the primary stock tank 12 is transported to the coagulation and sedimentation tank 13. As a result, the water level of the wastewater in the primary stock tank 12 decreases from approximately 100 mm to 0 mm. Along with this, the water level of the wastewater in the coagulation and sedimentation tank 13 rises from 0 mm to approximately 100 mm. Note that the water level referred to here is defined as the minimum water level at which each tank can be operated, which is 0 mm.

[0075] At time T12, the control unit 94 performs crushing of the disposable diapers D that have been fed into the input unit 91 by the crushing device 92. At the same time, the control unit 94 starts the operation of the pumps 14A and 14B of the discharge unit 14 to discharge wastewater at the first discharge flow rate and promote the formation of aggregated particles.

[0076] At time T13, the control unit 94 starts a water separation process in which the crushed paper diaper D and the processing liquid T, which is obtained by dissolving the water separation agent R in water, are stirred to separate the water from the polymer P, and the operation of the pumps 14A and 14B of the discharge unit 14 is stopped.

[0077] At time T14, the control unit 94 starts the operation of pumps 14A and 14B of the discharge unit 14 located in the coagulation and sedimentation tank 13 to discharge wastewater at the second discharge flow rate to promote the formation of coagulated granules, and at time T15, stops the operation of pumps 14A and 14B.

[0078] At time T16, the control unit 94 stirs the processing liquid T in the processing tank 93A with the stirring member 93B and rinses the inner wall of the processing tank 93A.

[0079] At time T17, the control unit 94 opens the solenoid valve 13K installed in the treated water discharge pipe 13J, transporting the supernatant water from the coagulation and sedimentation tank 13 to the secondary stock tank 17. The primary recovery filter 15 collects the coagulated particles (solid components) mixed in the supernatant water. As a result, the water level of the wastewater in the coagulation and sedimentation tank 13 drops from approximately 100 mm to 0 mm. At the same time, the water level of the wastewater in the secondary stock tank 17 rises from 0 mm to approximately 100 mm.

[0080] At time T18, the control unit 94 opens the on-off valve 93M, allowing the crushed pieces F containing the polymer P after the water separation treatment and the treatment liquid T to flow from the treatment tank 93A into the dewatering device 95. The control unit 94 then starts the operation of the dewatering motor 95A to begin separating the crushed pieces F and the treatment liquid T. Simultaneously, the control unit 94 operates the discharge pump 17D to begin transporting the treated water from the secondary stock tank 17 to the secondary recovery filter 18. The water level of the wastewater in the primary stock tank 12 gradually rises, and in parallel, the water level of the treated water in the secondary stock tank 17 gradually decreases. At this time, the air in the primary stock tank 12 is pushed out by the incoming wastewater and flows into the secondary stock tank 17 via the ventilation pipe 20.

[0081] At time T19, the separation of the crushed fragments F and the treated liquid T in the dewatering device 95 is completed, and the transfer of treated water from the secondary stock tank 17 to the secondary recovery filter 18 is also completed. At this time, the water level of the wastewater in the primary stock tank 12 is approximately 100 mm, and the water level of the treated water in the secondary stock tank 17 is 0 mm.

[0082] As described above, the wastewater treatment device 10 of Embodiment 1 is equipped with a coagulation and sedimentation tank 13 that stirs the wastewater, coagulates solid components in the wastewater, and settles solid components by changing the discharge flow rate of the wastewater mixed with the coagulant G. Since this wastewater treatment device 10 can perform stirring of the wastewater and the coagulant G, coagulation of solid components in the wastewater, and settling of solid components in a single coagulation and sedimentation tank 13, the installation space can be kept small.

[0083] In the wastewater treatment device 10, the coagulation and sedimentation tank 13 has a discharge unit 14 that sucks in and discharges wastewater. The discharge unit 14 discharges wastewater at a first discharge flow rate when agitating the wastewater, and discharges wastewater at a second discharge flow rate when coagulating solid components in the wastewater. The second discharge flow rate is less than the first discharge flow rate. By setting the discharge flow rate of the wastewater to a second discharge flow rate, which is less than the first discharge flow rate, the wastewater treatment device 10 can promote the coagulation reaction of solid components without breaking down the coagulated solid components.

[0084] In the wastewater treatment device 10, the discharge unit 14 has two discharge ports 14C and 14D for discharging wastewater into the coagulation and sedimentation tank 13. The discharge directions of the wastewater discharged from each discharge port 14C and 14D are parallel and opposite. This wastewater treatment device 10 can generate turbulence between the wastewater flows discharged from the two discharge ports 14C and 14D, and this turbulence makes it possible to thoroughly mix the wastewater and the coagulant.

[0085] In the wastewater treatment device 10, a discharge port 13B is formed in the coagulation and sedimentation tank 13. The device includes a first cover 13D that protrudes from the side wall of the coagulation and sedimentation tank 13 located above the discharge port 13B and is positioned above and in front of the discharge port 13B, and a second cover 13E that extends from the first cover 13D toward the side wall so as to surround the lower half of the discharge port 13B. In this wastewater treatment device 10, when solid components descend and settle, the first cover 13D prevents the solid components from entering the discharge port 13B, and when discharging wastewater from which solid components have been removed, the second cover 13E prevents the settled solid components from being caught in the flow of wastewater into the discharge port 13B, allowing the wastewater from which solid components have been removed to be discharged.

[0086] In the wastewater treatment method, the wastewater is agitated in the coagulation and sedimentation tank 13 by changing the discharge flow rate of the wastewater mixed with the coagulant G, thereby agitating the solid components in the wastewater and allowing them to settle. Since this wastewater treatment method can perform agitation of the wastewater and the coagulant G, agitation of the solid components in the wastewater, and sedimentation of the solid components in a single coagulation and sedimentation tank 13, the installation space can be kept to a minimum.

[0087] In the wastewater treatment method, the coagulation and sedimentation tank 13 has a discharge section 14 that sucks in and discharges wastewater. The discharge section 14 discharges wastewater at a first discharge flow rate to agitate the wastewater, and then discharges wastewater at a second discharge flow rate that is less than the first discharge flow rate to coagulate the solid components in the wastewater. In this wastewater treatment method, by setting the discharge flow rate of the wastewater to a second discharge flow rate that is less than the first discharge flow rate when coagulating the solid components in the wastewater in the coagulation and sedimentation tank 13, it is possible to promote the coagulation reaction of solid components without breaking down the coagulated solid components.

[0088] In the wastewater treatment method, the discharge unit 14 has two discharge ports 14C and 14D that discharge wastewater into the coagulation and sedimentation tank 13. Each discharge port 14C and 14D discharges wastewater in parallel and opposite directions. This wastewater treatment method can generate turbulence between the wastewater flows discharged from the two discharge ports 14C and 14D, and this turbulence makes it possible to thoroughly mix the wastewater and the coagulant G.

[0089] This disclosure is not limited to Embodiment 1 described above in the description and drawings, but also includes, for example, the following embodiments within the technical scope of this disclosure. (1) Unlike Embodiment 1, the discharge pipe may be extended outside the wastewater treatment device. For example, treated water stored in the secondary stock tank may be sent to the crushing device of the sewage treatment device via the discharge pipe. (2) Unlike Embodiment 1, the discharge section may be configured with only one pump. In this case, a bifurcated hose may be connected to the discharge port of the pump, and the discharge directions of each hose may be arranged parallel and opposite. Alternatively, the hose may be branched into three or more positions, or three or more pumps may be provided. (3) Unlike Embodiment 1, the secondary stock tank and secondary recovery filter may be omitted, and the treated water that has passed through the primary recovery filter 15 may be discharged into the sewer system. (4) Unlike Embodiment 1, if the amount of liquid allowed per unit time to flow into the secondary recovery filter is sufficiently large, a discharge pump may not be necessary. In this case, instead of a discharge pump, a solenoid valve may be installed at the outlet of the secondary stock tank, and treated water may be allowed to flow from the secondary stock tank to the secondary recovery filter by opening the solenoid valve. (5) The ventilation piping may be connected to the sewer or vent pipe and no shut-off valve may be installed. (6) Unlike Embodiment 1, the secondary stock tank may be positioned below the primary stock tank. (7) Unlike Embodiment 1, the wastewater discharged from the washing machine may be fed into the wastewater treatment device. (8) Unlike Embodiment 1, the inlet pipe may be connected to any of the four side walls at any position. [Explanation of symbols]

[0090] 10...Wastewater treatment device, 13...Coagulation and sedimentation tank, 13B...Discharge port, 13D...First cover, 13E...Second cover, 14...Discharge section, 14C,14D...Discharge port, G...Coagulant

Claims

1. A wastewater treatment apparatus comprising a coagulation and sedimentation tank that stirs the wastewater, coagulates solid components in the wastewater, and precipitates the solid components by changing the discharge flow rate of the wastewater mixed with a coagulant.

2. The aforementioned coagulation and sedimentation tank has a discharge section for discharging the wastewater, The discharge unit discharges the wastewater at a first discharge flow rate when agitating the wastewater, and discharges the wastewater at a second discharge flow rate when agglomerating the solid components in the wastewater. The wastewater treatment apparatus according to claim 1, wherein the second discharge flow rate is less than the first discharge flow rate.

3. The discharge section has two discharge ports for discharging the wastewater in the coagulation and sedimentation tank. The wastewater treatment apparatus according to claim 2, wherein the discharge direction of the wastewater discharged from each of the discharge ports is in the opposite direction.

4. The aforementioned coagulation and sedimentation tank is provided with an outlet. A wastewater treatment apparatus according to any one of claims 1 to 3, comprising: a first cover that protrudes from the side wall of the coagulation and sedimentation tank located above the discharge port and is positioned above and in front of the discharge port; and a second cover that extends from the first cover toward the side wall so as to surround the lower half of the discharge port.

5. A wastewater treatment method comprising stirring the wastewater in a coagulation and sedimentation tank by changing the discharge flow rate of the wastewater mixed with a coagulant, thereby coagulating the solid components in the wastewater and causing the solid components to settle.

6. The aforementioned coagulation and sedimentation tank has a discharge section for discharging the wastewater, The wastewater treatment method according to claim 5, wherein the discharge unit discharges the wastewater at a first discharge flow rate to agitate the wastewater, and discharges the wastewater at a second discharge flow rate less than the first discharge flow rate to coagulate the solid components in the wastewater.

7. The discharge section has two discharge ports for discharging the wastewater in the coagulation and sedimentation tank. The wastewater treatment method according to claim 6, wherein each of the aforementioned discharge ports discharges the wastewater in the reverse direction.

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