JP2006021173A5 - - Google Patents

Description

Cleaning wastewater for exhaust gas from incinerators contains inorganic fluorine compounds, heavy metals, SS, and the like. Removal of these components is required for environmental conservation or maintenance of human health, and the content is also defined by the Wastewater Pollution Prevention Law. Conventionally, heavy metals have been precipitated by adding an alkaline substance, but the actual situation is that they cannot be removed sufficiently by a single treatment, such as the pH at which they are likely to precipitate differs depending on the type of heavy metal. there were. Further, as a method for removing fluorine ions contained in the water to be treated, a calcium agglomeration precipitation method in which slaked lime or the like is added to water to precipitate fluorine ions as calcium fluoride has been most commonly performed. It was difficult to remove to a sufficient concentration. Therefore, a method has been devised in which activated alumina is added in addition to the drug to remove fluorine ions (see Patent Document 1).

Moreover, as shown in FIGS. 1 and 4, for example, the waste water treatment method according to the invention described in claim 2 is a process St11 to St14 for producing the first treated water E1 in the waste water treatment method according to claim 1. And the steps St21 to St24 for producing the second treated water E2 are the steps St11 and St21 for adding the slaked lime M1 and M2 to the drainage D1 or the filtrate L1, and the flocculants N1, N2 and P1 after adding the slaked lime M1 and M2. , P2, Q1, and Q2 are added. St12 to St14, St22 to St24 are provided.

If comprised in this way, it will react with slaked lime , an inorganic fluorine compound will become insoluble calcium fluoride, and a heavy metal will become an insoluble hydroxide, and will precipitate as microparticles | fine-particles. Therefore, the fine particles precipitated by the addition of the flocculant aggregate and grow into a solid material which is a larger aggregate.

Moreover, as shown in FIGS. 1 and 4, for example, the wastewater treatment method according to the invention described in claim 4 is the wastewater treatment method according to claim 3, wherein the flocculants are chelating agents N1 and N2 and inorganic agglomeration. Steps St11 to St14 for creating the first treated water E1 and St21 to St24 for creating the second treated water E2 add slaked lime M1 and M2. Steps St11 and St21, then adding the chelating agents N1 and N2, steps St12 and St22, then adding the inorganic flocculants P1 and P2, steps St13 and St23, and then adding the polymer flocculants Q1 and Q2, St14 and St24 including.

With this configuration, the inorganic fluorine compound reacts with slaked lime to become insoluble calcium fluoride , the heavy metal becomes an insoluble hydroxide, and when a chelating agent is added, a solid substance that is an insoluble chelate compound of heavy metal becomes Generate. When the inorganic flocculant is added, the inorganic flocculant is first uniformly dissolved in water, and then the inorganic hydroxide is precipitated. When inorganic hydroxide is precipitated, there are already heavy metal hydroxides , calcium fluoride and insoluble chelate deposits around it. To grow. The polymer flocculant grows into a solid that is a larger heavy agglomerate. Therefore, solid-liquid separation can be efficiently performed in the subsequent sedimentation and filtration steps.

In order to achieve the object, the wastewater treatment apparatus according to the invention described in claim 7 includes, as shown in FIG. 1, for example, slaked lime M1 and flocculants N1, P1, and Q1 added to wastewater D1 containing SS having a predetermined particle size. The first chemical injection devices 61 to 64 that are added to obtain the first mixed liquid E1; the first mixed liquid E1 is separated into the filtrate L1 and the solid, and the filtration membrane 31 is coated with the solid. A dehydrator 30 to be formed; and second chemical injection devices 66 to 69 in which slaked lime M2 and flocculants N2, P2, and Q2 are added to the filtrate L1 separated by the dehydrator 30 to form a second mixed liquid E2. The first mixed liquid E1 is sent to the dehydrator 30 and separated into the filtrate L1 and solid matter, and the coating is formed on the filter membrane 31 with the solid matter, and the dehydrator 30 on which the coating is formed is used. Control device for controlling the operation so as to filter the mixed liquid E2 And a 40.

If comprised in this way, the inorganic fluorine compound and heavy metal which did not precipitate with the slaked lime and flocculant added by the 1st chemical injection apparatus are made to precipitate with the slaked lime and the flocculant added by the 2nd chemical injection apparatus. Therefore, the wastewater treatment apparatus removes inorganic fluorine compounds and heavy metals to a low concentration. Further, the first mixed solution to which the slaked lime and the flocculant are added is filtered by the first chemical injection device, and the solid matter containing SS having a large particle size is coated on the filtration membrane, and the coated filtration is performed. Since the second liquid mixture to which slaked lime and the flocculant are added is filtered by the second chemical injection device using a dehydrator having a membrane, the second liquid mixture is an aggregate composed of particles having a small particle diameter. Even when only certain solids are included, the filtration membrane is less likely to be clogged.

Furthermore, in order to achieve the object, the wastewater treatment device according to the invention of claim 8, for example, as shown in FIGS. 1 and 2, slaked lime M1 and flocculant to the wastewater D1 containing SS of a predetermined grain size N1 , P1 and Q1 are added, and the first chemical injection devices 61 to 64 to be the first mixed liquid E1; the first mixed liquid E1 is separated into the filtrate L1 and the solid, and filtered through the solid A dehydrator 30 in which a coating is formed on the membrane 31; a second chemical injection device in which slaked lime M2 and flocculants N2, P2, and Q2 are added to the filtrate L1 separated by the dehydrator 30 to form a second mixed solution 66 to 69; a first settling tank 11 in which the first mixed liquid E1 is allowed to stand, and is installed in the first settling tank 11 from the vicinity of the liquid level L in the first settling tank 11 in the vertical direction. A first drainage introduction cylinder 14 having an inner diameter smaller than the inner diameter of the first sedimentation tank 11, The first drainage introduction pipe 51 for introducing the first mixed liquid E1 that is allowed to stand tangentially to the cylinder 14 and the vicinity of the bottom surface 19 of the first sedimentation tank 11 are scraped into the drainage introduction cylinder 14 of A first settling tank 11 having a first scraping blade 16 that rotates so as to take, or a second settling tank 12 in which the second mixed liquid E2 is allowed to stand, and the second settling tank 12 A second drainage introduction cylinder 14 ′ that is vertically installed in the second sedimentation tank 12 from the vicinity of the liquid level L inside thereof and has an inner diameter smaller than the inner diameter of the second sedimentation tank 12, and a second drainage introduction cylinder The second drainage introduction pipe 54 for introducing the second mixed liquid E2 that is placed in the tangential direction with respect to the cylinder 14 'and the vicinity of the bottom surface 19' of the second drainage introduction cylinder 14 'are scraped into the cylinder 14'. And a second settling tank 12 having a second scraping blade 16 ′ rotating to take.

If comprised in this way, in the 1st or 2nd sedimentation tank, the 1st liquid mixture E1 or the 2nd liquid mixture E2 to which slaked lime and the flocculant were added will be contained in the 1st or 2nd waste_water | drain introduction | transduction pipe | tube. By swirling, the density distribution of the solids that are aggregates in the wastewater can be graded, and the solids that are aggregates can be grown greatly, and then the solids are allowed to settle by allowing to stand. be able to. That is, the waste water treatment apparatus is capable of growing and settling solid matter that is an aggregate in one settling tank.

FIG. 1 is a block diagram of a wastewater treatment apparatus 1 according to an embodiment of the present invention. The wastewater treatment apparatus 1 receives a cleaning wastewater D0 (hereinafter also simply referred to as “drainage D0”) of exhaust gas from an incinerator, etc., and a receiving sedimentation tank 10 that settles SS and separates the supernatant T0, and a receiving sedimentation tank The first treated water E1, which is a first mixed solution to which a later-described chemical is added, is allowed to settle in the concentrated drainage D1 that has been concentrated by sedimenting SS and the like at 10, and the solids that are aggregates are allowed to settle to obtain a supernatant T1. The first sedimentation tank 11 to be separated, the dehydrator 30 that filters the first concentrated liquid S1 that has been precipitated and concentrated in the first sedimentation tank 11 through the filtration membrane 31, and the filtrate separated by the dehydrator 30. The second treated water E2, which is a second mixed liquid obtained by adding a later-described chemical, is allowed to stand in the combined liquid G in which L1 and the supernatant liquid T1 merge, and the solid liquid that is an aggregate is allowed to settle to obtain a supernatant liquid T2. A second settling tank 12 for separation, and a receiving settling tank. The concentrated drainage D1 concentrated by precipitating SS and the like at 10 is sucked, pumped to the first slaked lime stirring tank 71 described later, and further sent to the first sedimentation tank 11 and solidified in the first sedimentation tank 11 A first concentrated liquid S1 that sucks in and concentrates the first concentrated liquid S1 that has settled and concentrates the solid in the second sedimentation tank 12 and a second concentrated liquid S2 that settles and concentrates the solid in the second sedimentation tank 12. And a second concentrated liquid pump 22 for pumping to the dehydrator 30.

In addition, the waste water treatment apparatus 1 includes a pipe 50 for discharging the supernatant T0 of the receiving sedimentation tank 10 and a concentrated drainage D1 from the first sedimentation tank 10 to the first sedimentation tank 70 through the concentration drainage pump 20 from the receiving sedimentation tank 10. 11, a pipe 51 for sending the first concentrated liquid S1 from the first sedimentation tank 11 to the dehydrator 30 via the first concentrate pump 21, and a filtrate L1 for the second from the dehydrator 30 . A pipe 54 to be sent to the slaked lime stirring tank 76 and to the second settling tank 12, and a pipe connected to the pipe 54 from the first settling tank 11 to mix the supernatant liquid T1 into the filtrate L1 to be the combined liquid G 52, a pipe 55 for discharging the supernatant T2 of the second settling tank 12, and a pipe 56 for sending the second concentrated liquid S2 from the second settling tank 12 to the dehydrator 30 via the second concentrated liquid pump 22. Then, the filtrate L2 is discharged from the dehydrator 30 to the pipe 55. And a pipe 57. In the pipe 54, a cushion tank 81 is disposed downstream of the position where the pipe 52 is connected, and a cushion tank pump 82 that discharges the combined liquid G stored in the cushion tank 81 to the second sedimentation tank 12 is provided. . In addition, the piping 50-57 is not restricted to the piping path comprised with the pipe, The flow path formed with the trench etc. may be sufficient, and those flow paths shall be included in piping.

Moreover, in the waste water treatment apparatus 1, the 1st slaked lime injection | pouring apparatus 61 which adds slaked lime ( calcium hydroxide: Ca (OH) ₂ ) slurry to the concentrated waste_water | drain D1, and the chelating agent as a flocculant or a heavy metal collection agent A first chelating agent injection device 62 for adding, a first inorganic flocculant injection device 63 for adding ferric chloride (FeCl ₃ ) as an inorganic flocculant, and a first polymer for adding a polymer flocculant The flocculant injection device 64 is connected to the pipe 51 in this order from the upstream side. A slaked lime (Ca (OH) ₂ ) slurry, a chelating agent, ferric chloride and a polymer flocculant (hereinafter collectively referred to as “medicine”) are added to the downstream side where the concentrated drainage D1 is added. A slaked lime stirring tank 71, a first chelating agent stirring tank 72, a first inorganic flocculant stirring tank 73, and a first polymer flocculant stirring tank 74 (collectively referred to as first stirring tanks 71 to 74) are arranged. Then, the concentrated waste water D1 and the drug are mixed with stirring. The 1st stirring tanks 71-74 are vertical installation containers, Comprising: It has a stirring blade (not shown) for stirring a content liquid in it. The stirring blade is connected to a motor shaft (not shown), and the stirring blade is rotated by the rotation of the motor. These injection | pouring apparatuses 61-64 and the 1st stirring tanks 71-74 comprise a 1st chemical injection apparatus.

A second slaked lime injection device 66 for adding slaked lime (Ca (OH) ₂ ) slurry to the combined liquid G; a second chelating agent injection device 67 for adding a chelating agent as a flocculant or a heavy metal scavenger; A second inorganic flocculant injection device 68 for adding ferric chloride (FeCl ₃ ) as an inorganic flocculant and a second polymer flocculant injection device 69 for adding a polymer flocculant are arranged in this order from the upstream side. Thus, the pipe 54 is connected to the downstream side of the cushion tank pump 82. A second slaked lime stirring tank 76, a second chelating agent stirring tank 77, a second inorganic flocculant stirring tank 78, and a second polymer flocculant stirring tank 79 are disposed downstream of the respective chemicals added to the combined liquid G. (Collectively also referred to as second stirring tanks 76 to 79) is arranged, and the combined liquid G and the drug are stirred and mixed. Since the structure of the 2nd stirring tanks 76-79 is the same as the 1st stirring tanks 71-74, description is abbreviate | omitted. These injection devices 66 to 69 and the second stirring tanks 76 to 79 constitute a second chemical injection device.

Returning to FIG. 1, the description of the waste water treatment apparatus 1 will be continued. First slaked lime injection device 61, first chelating agent injection device 62, first inorganic flocculant injection device 63, first polymer flocculant injection device 64, second slaked lime injection device 66, second chelating agent injection device 67 The second inorganic flocculant injecting device 68 and the second polymer flocculant injecting device 69 are respectively connected to a drug tank for storing a drug, a reciprocating pump for delivering a fixed amount of drug, and a pipe 51 or a pipe 54 connected to the pipe 54. And have. The pump may be of other types, and if necessary, a flow rate adjusting valve may be provided on the pipe to adjust the flow rate. Alternatively, the medicine tank may be installed at a position higher than the pipe 51 and the pipe 54 so as to flow by gravity.

FIG. 4 shows a flowchart for explaining the procedure of wastewater treatment in the wastewater treatment apparatus 1, and the operation of the wastewater treatment apparatus 1 will be described with reference to FIGS. 1 and 4. First, drainage D0 from an incinerator (not shown) is sent to the receiving sedimentation tank 10. In the wastewater D0 from the incinerator, SS, which is a suspension of carbon particles carbonized in the incinerator, in addition to the contents such as inorganic fluorine compounds and heavy metals, which are discarded as they are and has an adverse effect on the environment. It is included. The heavy metals, cadmium, lead, mercury, chromium, arsenic, copper, nickel, including manganese, iron, zinc and the like. The drainage D0 is usually weakly acidic with a pH of 5-7.

While receiving the drainage D0 in the receiving sedimentation tank 10, the received drainage D0 is allowed to stand in the receiving sedimentation tank 10. The receiving sedimentation tank 10 secures a capacity sufficient to settle SS and the like with respect to the flow rate of the drainage D0 to be received. As the drainage D0 is allowed to stand, SS and the like settle. The remaining supernatant T0 from which SS or the like has settled is discharged from the side surface of the receiving sedimentation tank 10 through the pipe 50, returned to the exhaust gas cleaning device of an incinerator (not shown), and reused. Thereby , the total amount of the concentrated waste water D1, which is the waste water to be treated, can be reduced, and the subsequent equipment can be downsized.

Concentrated drainage D1 at the bottom of the receiving sedimentation tank 10 that has settled SS and the like is sucked by the concentrated drainage pump 20 and flows into the pipe 51 from the bottom of the tank. The slaked lime slurry M1 is added from the first slaked lime injection device 61 to the concentrated drainage D1 flowing through the pipe 51, and is stirred and mixed in the first slaked lime stirring tank 71 (St11). By adding the slaked lime slurry M1, the pH of the concentrated waste water D1 is adjusted to 7.5 or more and 9.5 or less. The pH of the concentrated drainage D1 is preferably adjusted to 8 or more and 9 or less. The slaked lime slurry M1 is added in an amount of 300 to 1800 mg, preferably 500 to 1500 mg, in 1 liter of the concentrated drainage D1. By inorganic fluorine compound and the heavy metals contained in the concentrate effluent D1 is reacted with slaked lime, calcium fluoride (CaF ₂₎ is produced from the non-machine fluorine compound, a metal hydroxide from heavy metals (M (OH) _X) Produces. M represents heavy metals . Also, pH is raised by adding calcium hydroxide, inorganic fluorine compounds are coprecipitated with magnesium hydroxide, i.e., precipitated. Furthermore, the slaked lime fine particles adsorb calcium fluoride and heavy metal hydroxide. Thus, the inorganic fluorine compound and heavy metals in the concentrated waste water D1 are deposited, adsorbed by the slaked lime fine particles, and grow into a larger solid substance.

The slaked lime slurry M1 is preferably produced by digesting quick lime because the particle size is fine and the reactivity and adsorption with heavy metals and fluorine are improved.

The waste water from the exhaust gas from the incinerator contains SS having a large particle size, and the above-mentioned heavy metal hydroxide precipitates, insoluble chelate compound precipitates , calcium fluoride precipitates and the like are inorganic flocculants and It aggregates by the addition of a polymer flocculant, and grows into a solid substance that is a large aggregate containing SS. Note that the aggregate is a general term for fine particles in which inorganic metals or fluorides are insolubilized by reacting with a drug or SS and solids densely packed by van der Waals force. Therefore, the ratio of the SS contained in the concentrated wastewater D1 to the total amount of solids produced by the treatment of the slaked lime and the flocculant is S / (FS) {where S is the concentration of SS contained in the concentrated wastewater D1 (mg S / (FS) is 0.1 or more, preferably 0.3 or more when expressed by the concentration of solid matter contained in the first treated water E1 (mg / liter)}. Further, it is preferable that SS having a concentration of 0.5 or more is contained in the concentrated drainage D1. The SS concentration S contained in the concentrated wastewater D1 and the solid matter concentration F contained in the first treated water E1 are determined in accordance with JIS K 0102: 1998 “Factory Wastewater Test Method”.

The flow path of the filtrate pipe 35 is switched by a signal i3 from the control device 40 so that the filtrate L1 taken out from the dehydrator 30 flows into the pipe 54. As described above, the pipe 52 from the first sedimentation tank 11 is connected to the pipe 54, and the supernatant liquid T1 of the first sedimentation tank 11 is added to the filtrate L1 to form the combined liquid G. Although the supernatant liquid T1 flows continuously, the filtrate L1 from the dehydrator 30 flows intermittently, so that the flow rate of the combined liquid G changes. Therefore, the combined liquid G is stored in the cushion tank 81, and the flow rate sent to the downstream side is stabilized. From the cushion tank 81, the combined liquid G is sent quantitatively by the cushion tank pump 82. The slaked lime slurry M2 is added to the combined liquid G from the 2nd slaked lime injection | pouring apparatus 66 (St21). By adding the slaked lime slurry M2, the pH of the combined liquid G is adjusted to 8 or more and 10 or less. The pH is preferably adjusted to 8.5 or more and 9.5 or less. Thus, by adjusting the pH to a range different from that of the first treated water E1 in the first stage treatment step, heavy metals and inorganic fluorine compounds that are not separated and separated in the first stage treatment step are precipitated. Can be removed. Particularly in the first stage treatment step, the pH of the first treated water E1 is adjusted to around 8.5 by adding the slaked lime slurry M1 to the concentrated drainage D1, and therefore, it is suitable for depositing and removing lead. In the two-stage treatment step, the pH of the second treated water E2 is adjusted to about 9 by adding the slaked lime slurry M2 to the combined liquid G, which is suitable for removing cadmium and fluorine compounds. Thus, it is preferable that the pH of the first treated water E1 in the first stage treatment step is lower than the pH of the second treated water E2 in the second stage treatment step.

The wastewater treatment apparatus 1 was used to treat the wastewater, and the amounts of heavy metal and fluorine remaining in the treatment liquid were measured. FIG. 6 shows a method and an apparatus for measuring elements and pH in waste water. FIG. 7 shows the results of measurement of elements contained in untreated waste water (raw water), treated water in the first stage treatment process, and treated water in the second stage treatment process , using cleaning wastewater of exhaust gas from the incinerator. In addition, the raw | natural water here refers to the concentrated waste_water | drain D1 (refer FIG. 1) settled in the receiving sedimentation tank 10 (refer FIG. 1). In FIG. 7, the measurement result of 2 times (experiment No. 1 and 2) which changed the chemical | medical agent addition amount slightly is shown. In FIG. 7, the removal rate after the second stage treatment represents the removal rate from the raw water.

Experiment No. 1, the concentration S of SS contained in the raw water and the concentration F of the total amount of solids produced by the treatment with slaked lime and the flocculant were measured, and the ratio S / (FS) was examined. The concentration (S) of SS contained in the raw water was 8370 mg / liter, and the concentration (F) of the total amount of solids contained in the treated water in the first treatment step was 22500 mg / liter. Thus, S / (FS) was 0.59.

It is a block diagram explaining the waste water treatment equipment which is one embodiment of the present invention. It is typical sectional drawing explaining the structure of a 1st sedimentation tank and a 2nd sedimentation tank. It is a perspective view explaining a filter press type dehydrator. FIG. 3A shows a filter press type dehydrator in which a filter chamber is formed and the first or second concentrated liquid is press-fitted. FIG.3 (b) shows the filter press type | mold dehydrator which squeezes a solid substance with air after press injection of a 2nd concentrate. FIG.3 (c) shows the filter press type | mold dehydrator which opens a filter plate and removes a dewatering cake. FIG. 3 (d) shows a filter press type dehydrator for washing the filtration membrane with washing water . 3 is a flowchart illustrating a procedure for wastewater treatment in the wastewater treatment apparatus 1. It is a perspective view explaining the coating formed on the filter membrane of a dehydrator. It is a figure which shows collectively the analysis method and analysis apparatus of the element in waste water, and pH. It is a figure which shows collectively the chemical | medical agent added to the waste_water | drain processed with the processing method which concerns on this invention, and the measurement result of the element contained in treated water.

DESCRIPTION OF SYMBOLS 1 Waste water treatment apparatus 10 Acceptance sedimentation tank 11 1st sedimentation tank 12 2nd sedimentation tank 13, 13 '1st container, 2nd container 14, 14' 1st drainage introduction cylinder, 2nd drainage introduction cylinder 15, 15 'first rotating shaft, second rotating shaft 16, 16' first scraping blade, second scraping blade 19, 19 'bottom 20 concentrated drainage pump 21 first concentrated liquid pump 22 first 2 Concentrate pump 30 Dehydrator 31 Filter membrane 32 Filter plate 33 Filter chamber 34 Supply port 35 Filtrate pipe 36 Coating 40 Controllers 50, 52, 53, 55-57 Pipe 51 Pipe (first drainage introduction pipe)
54 Piping (second drainage introduction pipe)
61 1st slaked lime injection device (1st chemical injection device)
62 1st chelating agent injection device (1st chemical injection device)
63 1st inorganic flocculant injection device (1st chemical injection device)
64 1st polymer flocculant injection device (1st chemical injection device)
66 Second slaked lime injection device (second chemical injection device)
67 Second chelating agent injection device (second chemical injection device)
68 Second inorganic flocculant injection device (second chemical injection device)
69 Second polymer flocculant injection device (second chemical injection device)
71 1st slaked lime stirring tank 72 1st chelating agent stirring tank 73 1st inorganic flocculant stirring tank 74 1st polymer flocculant stirring tank 76 2nd slaked lime stirring tank 77 2nd chelating agent stirring tank 78 2nd inorganic aggregation Agent agitation tank 79 second polymer flocculant agitation tank 81 cushion tank 82 cushion tank pump C dewatering cake D0 drainage D1 concentrated drainage E1 first treated water (first mixed solution)
E2 Second treated water (second mixed solution)
F Concentration of solids in the first treated water (mg / liter)
G Combined liquids i1 to 3 Signal L from the control device Liquid level L1 (of the first or second settling tank), L2 Filtrate M1, M2 Slaked lime slurry ( slaked lime )
N1, N2 chelating agent (flocculating agent)
P1, P2 Ferric chloride (inorganic flocculant)
Q1, Q2 Polymer flocculant S SS concentration of concentrated drainage (mg / liter)
S1 1st concentrated liquid S2 2nd concentrated liquid SD Precipitate upper surface T0-T2 Supernatant liquid

Claims (4)

The step of making the first treated water and the step of making the second treated water include adding slaked lime to the waste water or the filtrate; and
Adding a flocculant after adding the slaked lime ;
The wastewater treatment method according to claim 1. The flocculant includes a chelating agent, an inorganic flocculant, and a polymer flocculant;
The step of making the first treated water and the step of making the second treated water are a step of adding slaked lime , a step of adding a chelating agent, a step of adding an inorganic flocculant, and then a polymer flocculant Adding
The wastewater treatment method according to claim 3. A first chemical injection device in which slaked lime and a flocculant are added to wastewater containing suspended solids having a predetermined particle size to form a first mixed solution;
A dehydrator that separates the first mixture into a filtrate and a solid, and a coating is formed on the filtration membrane by the solid;
A second chemical injection device that adds slaked lime and a flocculant to the filtrate separated by the dehydrator to form a second mixed solution;
The first mixed liquid is sent to the dehydrator, separated into the filtrate and the solid, a coating is formed on the filtration membrane with the solid, and the dehydrator having the coating is used to form the first mixture. A controller for controlling the operation so as to filter the mixture of the two;
Wastewater treatment equipment. A first chemical injection device in which slaked lime and a flocculant are added to wastewater containing suspended solids having a predetermined particle size to form a first mixed solution;
A dehydrator that separates the first mixture into a filtrate and a solid, and a coating is formed on the filtration membrane by the solid;
A second chemical injection device that adds slaked lime and a flocculant to the filtrate separated by the dehydrator to form a second mixed solution;
A first settling tank in which the first mixed liquid is allowed to stand;
A first drainage introduction cylinder installed in a vertical direction in the first settling tank from near the liquid surface in the first settling tank, and having an inner diameter smaller than the inner diameter of the first settling tank;
A first drainage introduction pipe for introducing the first mixed liquid to be left stationary in a tangential direction with respect to the cylinder in the first drainage introduction cylinder;
A first sedimentation tank having a first scraping blade rotating so as to scrape the vicinity of the bottom surface of the first sedimentation tank, or a second sedimentation tank in which the second mixed liquid is allowed to stand. ,
A second drainage introduction cylinder installed in the vertical direction in the second settling tank from near the liquid surface in the second settling tank, and having an inner diameter smaller than the inner diameter of the second settling tank;
A second drainage introduction pipe for introducing the second mixed liquid to be stationary in a tangential direction with respect to the cylinder in the second drainage introduction cylinder;
A second settling tank having a second scraping blade rotating so as to scrape the vicinity of the bottom surface of the second settling tank;
Wastewater treatment equipment.

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