JP2012192344A - Wastewater treatment equipment, and waste water treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide wastewater treatment equipment and a wastewater treatment method each having a novel configuration, in which a powdery flocculant can be directly put in a flocculation reaction bath, regarding wastewater treatment equipment and a wastewater treatment method which use a precoat-type vacuum filtration apparatus.SOLUTION: The wastewater treatment equipment includes: a flocculation reaction device (10) which produces a raw liquid to be filtrated by forming flocs by adding a powdery flocculant into wastewater; and a filtration-separating device (16) for filtration-separating the raw liquid to be filtrated which is supplied from the flocculation reaction device (10), into a cake and clarified water. The flocculation reaction device (10) includes: a flocculation reaction bath (14) equipped with a stirrer (22); a wastewater supply unit which supplies wastewater to the flocculation reaction bath (14); and a flocculant supply unit which supplies the powdery flocculant composition. A raw-liquid-to-be-filtrated supply piping-line (31) having a supply port (31a) at a position of a set liquid level of the raw liquid to be filtrated, which supplies the raw liquid to be filtrated from the flocculation reaction bath (14), and a return pipeline (37) which returns the raw liquid to be filtrated to the flocculation reaction bath (14) from a bath (36) for raw liquid to be filtrated, are provided between the flocculation reaction bath (14) and the bath (36).

Description

  The present invention relates to a wastewater treatment facility and a wastewater treatment method using a precoat type vacuum filtration device.

  A flocculant was added to the wastewater, and the solid content contained in the wastewater was combined to form a floc, and in the case of wastewater treatment for solid-liquid separation, a precoat vacuum filtration device was used to obtain a high-clarity filtrate. There are wastewater treatment facilities (for example, Patent Documents 1 and 2).

  As shown in FIG. 1, the wastewater treatment facility includes a precoat tank 11, a vacuum filtration device 16, and a coagulation reaction device 10.

  The agglomeration reaction apparatus 10 includes an agglomeration reaction tank 14, waste water supply means (waste water tank 12, waste water supply pipe 28) for supplying waste water to the agglomeration reaction tank 14, and a supply means for coagulant and the like (alkaline) A liquid tank 18, an inorganic flocculant tank 20, and supply pipes 26, 26) are provided.

  Each of these tanks 18 and 20 is equipped with stirrers 22 and 22. That is, a certain amount of alkaline solution is added to the wastewater supplied to the agglomeration reaction tank 14 and then neutralized with a sulfuric acid band to form floc. Each of the alkaline liquid tank 18 and the inorganic flocculant tank 20 dilutes and suspends the drug about 10 to 20 times and supplies it to the agglomeration reaction tank 14 via the supply pipe 26 with a pump (diaphragm type) 24. . In the figure, 36 is a stock solution tank, 38 is a filter drum, 46 is a scraper device, and 47 is a cake collection box.

  In the wastewater treatment facility having the above configuration, the following problems have been pointed out.

  The vacuum filtration device 16, the precoat tank 11, the agglomeration reaction tank 14, the alkaline liquid tank 18 and the inorganic flocculant tank 20, respectively, the stirrers 22 and 22 and the quantitative supply pumps 24 and 24 to the agglomeration reaction tank 14 and the supply pipes 26 and 26, respectively. Furthermore, a pH meter 13 is required for the aggregation reaction tank 14.

  Moreover, since the slaked lime of the alkaline liquid tank 18 is sparingly soluble in water, it is usually necessary to add it before the sulfuric acid band of the inorganic flocculant tank 20 for the following reasons.

  This is because the control by the pH meter is one-point control, and it is necessary to add a sulfuric acid band solution to a predetermined pH and reduce it to a predetermined pH in waste water that has been dissolved by adding slaked lime to become alkaline.

  Depending on the type of wastewater, the addition of the sulfuric acid band may improve the oil removal.

  For these reasons, a relatively large equipment floor area is required, equipment costs are increased, and operation costs tend to be increased.

  In order to solve these problems, it is conceivable to add a powdery coagulant or the like directly to the waste water stored in the coagulation reaction tank 14 to obtain a filtrate stock solution. Then, the alkali liquid tank 18 and the inorganic flocculant tank 20 are not necessary, and the pumps 24 and 24 for supplying the alkali liquid and the flocculant from the respective tanks 18 and 20 to the aggregation reaction tank 14 and the supply pipe 26 are provided. , 26 becomes unnecessary.

  Patent Document 1 proposes a vacuum precoat filtration method having the following configuration, and describes that a filtration stock solution can be prepared by directly adding a powdery flocculant to the agglomeration reaction tank 14 to which waste water (raw water) is supplied. .

  The description of claim 1 and paragraph 0040 in Patent Document 1 is cited below.

  [[Claim 1] The filtered stock solution is poured almost uniformly in the axial direction on the upper surface of the filter drum from above the rotated filter drum, and is separated into a solid content and a liquid content by the precoat layer of the filter drum. The solid content is captured on the precoat layer, the liquid content is sucked into the filter drum, and at the same time, the solid content is dehydrated into a cake, and the dehydrated cake layer is separated from the precoat layer and taken out. Top feed type continuous vacuum precoat filtration method. "

  “[0040] In the method of the present invention, a predetermined amount of flocculant is added to the filtrate stock, and after stirring and mixing, it is poured from above the filter drum. In general, flocculants are difficult to dissolve in water. It takes time to dissolve and has a low solubility.Therefore, dissolve it in a large amount of water to make an aqueous solution, and inject it in the middle of the filtration stock supply piping, or install a coagulation tank and supply it to this On the other hand, in the method of the present invention, the top feed method is used, so that the flocculant is put into the flocculant tank as a powder, that is, the flocculant is added at a high concentration with respect to the filtrate stock solution. The turbid particles can be aggregated and guided to the upper side of the filter drum, poured from above and filtered, and as a result, if the floc is large in the prior art (see Appendix; coarse) The flocs settle to the bottom of the filtrate stock solution tank.), Which had hindered the filtration and adsorption, but the method of the present invention employs the top feed method. Therefore, even if the suspension is difficult to agglomerate with the addition of a low concentration of a flocculant in the prior art, the method of the present invention can be used as a filtration stock solution. It is possible to add a flocculant at a high concentration, enhance the agglomeration effect, and form flocs to improve the processing efficiency. "

  However, the preparation of the filtrate stock solution by the direct use of the powdery flocculant in Patent Document 1 does not recognize that the powdery flocculant in the present invention is directly introduced into the wastewater for the following reasons.

  In the above precoat type vacuum filtration method, the undiluted filtration solution (powdered flocculant is used in the undiluted position (filtration adsorption step A: FIG. 27) in the undiluted filtration solution tank (filter tank) of the filter drum. This is because there is no description of how to eliminate the trouble of filtration adsorption in the case of containing a large floc. That is, the filtration stock solution tank is supplied to the top of the filter drum and flows down without filtration, or directly flows from the agglomeration reaction tank through the branch pipe, and stores the filtrate stock solution containing large flocs. As described above, coarse flocs are deposited on the bottom and are not adsorbed on the surface of the filter drum, making vacuum filtration difficult.

  In addition, although it does not affect the patentability of this invention, patent document 2 etc. exist as a prior art document relevant to the wastewater treatment facility using a precoat-type vacuum filtration apparatus.

JP-A-8-38818 JP 2010-234325 A

  In view of the above, the present invention is a wastewater treatment facility and a wastewater treatment method using a precoat-type vacuum filtration device, and a wastewater treatment facility and a wastewater treatment method having a novel configuration capable of directly feeding a powdery flocculant into an agglomeration reaction tank The purpose is to provide.

  As a result of diligent development efforts to solve the above problems, the inventors have come up with a wastewater treatment facility and a wastewater treatment method having the following configuration. For reference, a reference numeral is attached in parentheses.

The wastewater treatment facility of the present invention supplies the filtrate stock solution of the coagulation reactor (10) that forms flocs by adding a flocculant to the wastewater to the filter separation device (16) in order to filter and separate into cake and clarified water. In the wastewater treatment facility,
The filtration separation device is a precoat type vacuum filtration device (16) provided with a filtrate stock solution tank (36) for storing a filtrate stock solution, a filter drum (38), and a scraper means (46),
The agglomeration reaction apparatus (10) comprises an agglomeration reaction tank (14) provided with a stirrer (22), waste water supply means (12, 28) for supplying waste water to the agglomeration reaction tank (14), and a powdery flocculant A flocculant supply means (15) for supplying the composition,
Between the agglomeration reaction tank (14) and the filtrate stock solution tank (36), a supply port (31a) is provided at a set filtration stock solution surface position to supply the filtrate stock solution from the agglomeration reaction tank (14). A filtration stock solution supply pipe (31) and a filtration stock solution return pipe (37) for returning the filtrate stock solution from the filtration stock solution tank (36) to the aggregation reaction tank (14) are provided.

It is a flowchart which shows an example of the conventional wastewater treatment facility. It is a flowchart which shows an example of the waste water treatment facility of this invention. It is principle explanatory drawing of the precoat type vacuum filtration apparatus used by this invention. It is the side model figure (A) and front model figure (B) for operation | movement description of the filter chamber division type filter drum applied to this invention. It is the whole scraper apparatus used by this invention front view (A), and the enlarged view (B) of a scraping blade holding | maintenance part. It is the side model figure (A) and front model figure (B) of the vacuum filtration apparatus which arranged the paddle (fan turbine type) rotary stirring blade between the filter drum applied to this invention, and the filtration stock solution tank bottom part. It is the side model figure (A) and front model figure (B) of the vacuum filtration apparatus which similarly provided the rocking | swiveling stirring blade.

  One embodiment of the wastewater treatment facility of the present invention will be described based on the drawings.

  FIG. 2 shows an example of a flow sheet of the wastewater treatment facility. This flow sheet assumes waste water treatment such as polishing waste water, die-cast release agent waste water, flexo ink waste water and the like.

  As a basic configuration, an agglomeration reaction device 10 and a filtration separation device (vacuum filtration device) 16 are provided. The agglomeration reaction apparatus 10 includes an agglomeration reaction tank 14 provided with a stirrer 22, waste water supply means 12 and 28 for supplying waste water to the agglomeration reaction tank 14, and an aggregating agent for supplying powdery (powder) aggregating agent. Supply means 15 is provided.

  Here, the powdery flocculant composition supplied from the powdery flocculant supply means 15 uses at least an inorganic flocculant and a pH buffer. Here, the pH buffer is used together with the inorganic flocculant for the following reason.

  This is because the use of a pH buffering agent can prevent a decrease in the coagulating action of the inorganic coagulant without adding the inorganic coagulant to the filtered stock solution from the neutral range.

Specifically, examples of the inorganic flocculant include aluminum salts such as sulfate band (Al ₂ (SO ₄ ) ₃ .nH ₂ O), PAC (Al ₂ (OH) _n Cl _6-n ), and sulfuric acid first Iron salts such as iron (FeSO ₄ ), ferric chloride (FeCl ₃ ), and ferric sulfate (Fe ₂ (SO ₄ ) ₃ ) can be used.

  Moreover, what is necessary is just to select the buffering agent which buffers the target pH range (usually 4-14) as a pH buffering agent. A mixture of a weak acid and its conjugate base in about 0.5 pH units centered on the pKa of the weak acid (see Oki et al., “Chemical Dictionary”, Tokyo Chemical Dojin, 1994, “Buffer”). As the pH buffer, for example, various phosphates can be used.

  Furthermore, if necessary, the polymer flocculant may be added to the powder flocculant composition, or may be supplied in the middle of the filtration stock solution supply pipe.

  As the polymer flocculant, an anionic one is used in the case of the waste water exemplified above. Examples of the anionic polymer flocculant include sodium alginate, CMC sodium salt, sodium polyacrylate, polyacrylamide partial hydrolysis salt, and the like.

  A waste water tank (raw water tank) 12 stores the polishing waste water and the like, and a waste water supply pipe 28 is disposed between the waste water tank 12 and the agglomeration reaction tank 14. In addition, although not shown in figure, the waste water tank 12 is normally equipped with the stirrer and the pump.

  The agglomeration reaction tank 14 includes a stirrer 22. Between the agglomeration reaction tank 14 and the filtration stock solution tank 36 of the vacuum filtration device 16, a filtration stock solution supply pipe 31 including a supply pump 25 for the filtration stock solution (waste water containing floc: sludge) is disposed. .

  And waste water (for example, grinding | polishing waste water) normally uses the thing in the range of pH5.5-9 (desirably pH6-8). When the pH is out of the range, an alkaline agent is added and the pH is adjusted to be in the above range. The reason why the waste water having the above-mentioned range is used is that the buffer capacity can be exhibited by the addition of the pH buffering agent.

  In the agglomeration reaction tank 14 to which the wastewater is supplied, the pH of the wastewater is in a neutral range (pH 5.5 to 9, preferably pH 6 to 8), so the particles in the wastewater are negatively charged. Then, by supplying and stirring a powdery flocculant containing an inorganic flocculant such as a sulfuric acid band, the positive charge in the flocculant reacts with the negative charge of the particles, and the particles stick to each other, Flocks (aggregates) (particle size 100-500 μm) are formed.

  The reason why an inorganic flocculant such as a powdered sulfuric acid band can be directly added to the agglomeration reaction tank by containing a pH buffer is as follows. A sulfuric acid band (aluminum sulfate) is taken as an example, but the same applies not only to other aluminum salt systems but also to iron salt systems.

If the pH coagulant is contained in the powder flocculant and the liquidity can be maintained neutral, Al (OH) ₃ (s) with a positive charge of aluminum hydroxide near the pH neutral range Can be formed. As a result, colloidal particles with negatively charged Al (OH) ₃ (s) are taken in and electrically neutralized, so that the particles are attracted by Vanden-Walls force (interparticle attractive force), so-called slow aggregation. (Sweep coagulation) (Kenji Fujita "Water Treatment Chemicals Handbook", Technical Hall Publishing, 2003, p23-24, Fig. 2.1.5 Aggregation region in aluminum sulfate aggregation).

  Then, the filtrate stock solution (sludge) generated by the floc is supplied to the filtration separation device (vacuum filtration device) 16. Between the agglomeration reaction tank 14 and the filtrate stock solution tank 36, a filtration stock solution supply pipe 31 having a supply port 31a at the set filtration stock solution surface position and supplying the filtrate stock solution from the agglomeration reaction tank 14 is arranged. .

  By adding (supplying) the polymer flocculant to the sludge, the contained floc can be further increased in diameter and the floc strength (destructive strength) can be increased.

  In this embodiment, the vacuum filtration device 16 basically uses a precoat type vacuum filtration device having the principle as shown in FIG.

  That is, a filter stock solution tank (filter tank) 36 and a filter drum 38 that is arranged so that the lower side is immersed in the filter stock solution tank 36 are provided. A filtrate pipe 44 connects between the central rotating shaft side of the filter drum 38 and an airtight separation tank (decompression chamber) 42 provided with a vacuum pump 40.

The filter drum 38 can be rotated at a low speed (for example, 0.5 to 2 min ⁻¹ ) by forced driving, and a scraping blade 48 of a scraper means (scraper device) is disposed on the side facing the rotation direction of the filter drum 38. Has been. The scraper means allows the scraping blade 48 to be advanced at a predetermined speed, and continuously peels off the precoat layer 50 to which the cake 49 is adhered to constantly expose the surface of the new precoat layer 50. In this way, stable continuous filtration is possible, and treated water (filtrate) with high clarity can be obtained.

  In the present embodiment, the general-purpose filter drum 38 has the following configuration (see FIG. 4).

  A plurality of uniform filter chambers 62 are partitioned by the partition plate 60 between the inner cylinder portion 56 and the outer cylinder portion 58 of the filter drum 38 to be rotatable, and each filter chamber 62 has its partition plate 60. In the vicinity of the inner side surface in the rotation direction, a branch pipe 66 branched from the filtrate main pipe 64 also serving as the rotation axis is continued, and the filter drum 38 is filtered so that its lower half is located in the tank. Tank) 36 is installed.

  The filter drum 38 has an outer cylinder portion 58 formed of a wire mesh, and a filter cloth 54 as a support for the precoat layer 50 is stretched and fixed to the wire mesh. The filtrate main pipe 64 also serving as a rotating shaft provided at the center of both sides of the filter drum 38 is attached with a driving chain wheel 68 at its middle part, and the end part is connected to a vacuum device (the aforementioned vacuum pump via a hollow rotary joint). 40 is connected to an airtight separation tank 42).

  In this way, the precoat liquid having a predetermined concentration is first supplied from the precoat tank 11 to the filtrate stock solution tank 36, and the vacuum drum (vacuum pump 40) is driven at the same time as the filter drum 38 is rotated at a low speed. At this time, a branch pipe 66 branched from the filtrate main pipe is continued in a plurality of uniform filter chambers 62 partitioned by the partition plate 60 between the inner cylinder part 56 and the outer cylinder part 58.

  For this reason, when there is no filtrate stock solution (precoat solution or reaction solution) in the tank, the pressure is evenly reduced and an equal amount of air is sucked through the outer cylinder portion 58.

  Next, as shown in the figure, the lower half of the filter drum 38 composed of six filter chambers 62 that rotate rightward in the direction of the arrow is positioned in the tank, and the filtrate stock solution (precoat liquid or reaction liquid) is placed in the tank. The suction action when supplied is as follows. Hereinafter, for easy understanding, each position code is appended with parentheses for the filter chambers 62 at the positions A to F.

  The filter chamber 62 (A) that reaches the lower right position A corresponding to the filtration zone adsorbs the dispersoid in the filtrate on the surface and sucks the filtrate into the filter chamber 62 (A). At this time, since the filtrate has not yet reached the suction port of the branch pipe 66, the filtrate sucked into the filter chamber 62 (A) is not sent to the filtrate main pipe 64.

  Thus, the filter drum 62 is gradually rotated to reach the lower left position B, and the filtrate sucked into the filter chamber 62 (B) reaches the suction port of the branch pipe 66. The filtrate is gradually sucked and discharged through the filtrate main pipe 64, and suction force acts on the surface of the outer cylinder portion 58 of the filter chamber 62 (B) to such an extent that the cake adsorbed at the lower left position does not peel off. Become.

  Next, in the filter chamber 62 (C) that has been rotated to the left position C, the filtrate inside reaches the suction port of the branch pipe 66 as in the lower left position B. Therefore, the filtrate is further discharged through the branch pipe 66 and the filtrate main pipe 64, and the upper half of the surface of the filter chamber 62 (C) communicates with the atmosphere through the cake adsorbed thereto. At this time, since the suction port portion of the branch pipe 66 is located in the filtrate, the amount of air passing through the upper half is very small and does not adversely affect the suction force with respect to the other filter chambers 62.

  Further, the filter chamber 62 (D) rotated to the upper left position D, like the left position C, sucks moisture in the cake and functions as a drying zone. For this reason, the amount of filtrate in the filter chamber 62 (D) is also reduced.

  Next, in the filter chamber 62 (E) rotated to the upper right position E, the amount of air sucked from the surface of the filter chamber 62 is released from the suction port of the branch pipe 66 by the flow of the internal filtrate in the rotational direction. Slightly increases, and the function as a drying zone also increases. At this time, the filtrate remaining in the filter chamber 62 (E) is in the lower part of the surface of the filter chamber 62 (E). For this reason, the suction force to at least the other filter chambers 62 on the surface of the filter chamber 62 (E) that directly sucks the atmosphere is not adversely affected, and the vacuum with the lower right position A, the lower left position B, etc., which corresponds to the filtration zone. The balance is good.

  Then, when the filter chamber 62 is rotated to the right position F, the tip of the scraping blade 48 faces the outer periphery of the filter chamber 62 (F), thereby drying the upper left position D and the upper right position E. In the zone, the precoat layer to which the dried cake is attached can be peeled off.

  Next, when the filter chamber 62 is rotated to the right position F, the filter chamber 62 (F) acts in the same manner as the filter chamber 62 (E) at the upper right position E. At this time, the lower part of the filter chamber 62 (F) is gradually immersed in the filtrate stock solution in the filter tank 36, so that the amount of air sucked from the surface is the filter chamber 62 (E) at the upper right position E. The amount of suction in the atmosphere is further reduced, and there is almost no adverse effect on the suction of the other filter chambers 62.

  Through such a process, the filter drum 38 continues to rotate, so that the vacuum efficiency is extremely high at the upper left position D and upper right position E, which are drying zones, and at the lower right position A and lower left positions B, which are filtration zones. Thus, an efficient filtration operation can be continuously performed without a switching valve.

  Next, details of the scraper means (scraper device) 46 will be described (see FIG. 5). Of course, other conventional scraper means may be used.

  A scraper device 46 that can move toward the precoat layer 50 formed on the outer peripheral surface of the filter drum 38 is attached to the support stand 74 provided on the machine frame 72 at an angle.

  A screw shaft 76 is pivotally supported by a bearing attached to the support base 74, and the screw shaft 76 is attached to be inclined with respect to the precoat layer 50, and a holder 78 is fixed at a right angle to the tip of the screw shaft 76. Yes. A notch 80 is provided at one end of the holder 78, and a scraper blade 48 made of a thin steel plate having a razor blade thickness of 1 mm or less (preferably 0.1 to 0.6 mm) is placed on the notch 80. The entire surface of the scraping blade 48 is held on the surface of the notch 80 by a presser fitting 82 made of a mountain-shaped elastic thin plate having a projection 87 for pressing it. The presser fitting 82 can be tightened by tightening a fastening bolt 84 so that the scraping blade 48 is elastically supported by the tip of the presser fitting 82 and the tip of the projection 87. The male screw portion 86 of the screw shaft 76 is screwed into a sleeve 90 having a female screw 88. The outer diameter portion of the sleeve 90 is keyed to the worm wheel 92. The worm wheel 92 meshes with a worm 96 having a worm shaft 94. The worm 96 and the worm wheel 92 are accommodated in a gear case 98 integrated with the bearing. Further, the worm shaft 94 can be engaged with and disengaged from the worm wheel 92 by an engagement / disengagement device (not shown). Further, a stopper collar 100 that prevents the screw shaft 76 from moving forward is attached to the end of the screw shaft 76, and a handle 99 is attached to a sleeve 90 that is fitted to the screw shaft 76.

  In this configuration, when the worm shaft 94 is rotated to rotate the worm 96, the screw shaft 76 is slowly advanced toward the precoat layer 50, and the precoat layer 50 to which the cake adheres is scraped off. The cutting edge of the blade 48 can be thinned off. At this time, the cutting edge portion of the scraping blade 48 is worn, but since the thickness of the scraping blade 48 is as thin as 0.1 to 0.6 mm, a flat portion as seen in the case of a thick blade even if the cutting edge portion is worn. It will never be a cutting edge. For this reason, the frictional resistance acting on the cutting edge during scraping of the cake is less than in the case of the thick blade, and the cutting action of the cake layer does not change much.

  Therefore, the precoat layer exposed by scraping the cake does not cause striped clogging, and the scraping blade 48 attached to the holder 78 can withstand long-term use.

  Further, the scraping blade 48 is elastically supported by a presser fitting 82 made of an elastic thin plate. Therefore, even when the scraping blade 48 is mounted on the holder 78 as a whole and a hard lump of foreign matter is present in the cake, the tip of the scraping blade 48 is slightly deformed by the elastic action of the presser fitting 82. Thus, the foreign matter can be overcome or scooped out, and the blade tip does not spill due to the impact applied to the tip.

  As described above, the thickness of the scraping blade 48 is preferably 0.1 to 0.6 mm, but depending on the material of the scraping blade 48, it can be in the range of 0.05 to 1 mm.

  Furthermore, in this embodiment, the filter drum 38 can filter the suction filtration pressure with a stable suction pressure without using a switching valve as described above, so that the moisture content of the cake adhering to the precoat layer is stable. is doing. Therefore, the undulation (variation) of the surface strength of the cake adhesion precoat layer at the scraping position is small. For this reason, the scraping blade is cut smoothly in the normal state where it does not interfere with foreign matter, and wear of the scraping blade occurs evenly regardless of the position of the drum. No reduction in filtration performance due to layer breakage.

  A further desirable mode of the present embodiment is that, in the above configuration, a stirring blade (stirring means) is disposed between the bottom wall of the filtrate stock solution tank 36 and the filter drum 38.

  This agitation means is installed to prevent the floc sedimentation and accumulation in the filtrate stock solution tank 36. The accumulation of flocs causes a reduction in filtration efficiency.

  As the stirring means, a horizontal rotation stirring type (paddle type: fan turbine type) (FIG. 6), a swing stirring type (cradle type) (FIG. 7), and the like can be considered.

  In the case of the horizontal rotary stirring type, it is necessary to increase the rotational speed of the paddle (rotary blade) 102 to prevent sedimentation of flocs. However, when the number of rotations is increased, the floc is destroyed and the floc diameter is reduced, so that the particle size of the filter aid for forming the precoat layer for capturing the floc cannot be increased. If the particle size of the filter aid can be increased, the particle gap in the precoat layer increases and the filtration rate increases. Incidentally, the general-purpose particle size of the conventional filter aid (for example, diatomaceous earth) was about 40 μm.

  Moreover, it is necessary to provide the bearing part of the rotating shaft 104 in the filtrate stock solution tank 36, and it is necessary to set it as a liquid seal structure.

  In contrast to the horizontal rotation stirring method, the swing stirring method has a structure in which the driving shaft of the swing lever is provided outside the liquid (the rotation shaft portion of the filter drum). For this reason, a seal structure for supporting the shaft is not required in the filtrate stock solution tank 36. Further, by gently rocking the stirring member along the bottom of the filtrate stock solution tank 36, it is easy to prevent sedimentation without destroying the floc.

  Here, the shape of the oscillating stirring blade may be a rod body, an angle body, or a band plate body that oscillates along the arc-shaped bottom of the filtrate stock solution tank 36, but a projected arc shape as shown in FIG. It is desirable to use the arcuate stirring blade 106 of the planar frame body or planar porous body.

  At this time, the gap between the arc-shaped stirring blade 106 and the bottom surface of the filtrate stock solution tank 36 is, for example, 1 to 25 mm, depending on the size of the formed floc.

  The shape of the arc stirring blade 106 is not particularly limited as long as it is arcuate, and may be a perforated plate, but a pair of arcuate plates connected by a bar, an angle, or a slat arranged at equal intervals. The stirring effect is easy to obtain, which is desirable.

  The arc-shaped stirring blade 106 is driven to swing by using a general-purpose reciprocating mechanism connected to a prime mover (not shown).

  Furthermore, in this embodiment, it is desirable to form a filtration stock solution return pipe 37 to the aggregation reaction tank 14 at the bottom of the filtration stock solution tank 36 so that the sedimentation floc can be returned to the aggregation reaction tank 14. This is because when the floc is too large to settle and vacuum filtration is possible, the flocs are returned to the agglomeration reaction tank 14 so that reprocessing is possible.

  Next, the usage aspect of the vacuum filtration apparatus provided with the said stirring apparatus is demonstrated.

1) Precoat operation The filter aid dispersion liquid is pumped to the filtrate stock solution tank 36. In addition, it does not specifically limit as a filter aid, For example, diatomaceous earth, perlite, etc. can be used.

Then, the filter drum 38 is rotated at a low speed (for example, 1 min ⁻¹ ) and vacuumed (for example, 40 kPa), and the arc-shaped stirring blade 106 is swung (reciprocated). The reciprocating motion cycle at this time is 20 to 50 Hz.

  At this time, the tip of the scraping blade 48 of the scraper device is kept stationary at a position away from the outer peripheral surface of the filter drum 38 by the set thickness of the precoat layer 50.

  By reciprocally swinging the arc-shaped stirring blade 106, even a filter aid having a large particle size is not deposited on the bottom of the filtrate stock solution tank 36. Further, as described above, a high suction pressure acts on the filter cloth surface of the filter drum 38 while being immersed in the precoat liquid. For this reason, a filter aid having a large particle size is efficiently attached to the filter drum 38, so that the precoat layer is efficiently formed. Here, for example, in the case of diatomaceous earth, one having a particle diameter of 40 to 80 μm is used.

  In order to prevent cracks, fresh water is supplied during pre-coating.

2) Coagulation operation Waste water is supplied from the waste water tank 12 to the coagulation reaction tank 14 with the supply pump until the liquid level position signal of the level meter of the coagulation reaction tank 14 is received and reaches the set liquid level position (H position).

  A powdery flocculant composition (an inorganic flocculant to which a pH buffer is added) is supplied from the powdery flocculant supply means (unit) 15 to the aggregation reaction tank 14. Thereafter, the flocs are generated in the agglomeration reaction tank 14 and continuously supplied to the filtrate stock solution tank 36 of the vacuum filtration device 16. After supplying the powdery flocculant, the stirring is stopped, and the generated floc is allowed to settle at the bottom of the agglomeration reaction tank 14. 36 may be supplied.

3) Filtration operation The filtrate stock solution (sludge) is filtered from the aggregation reaction tank 14 through the filtrate stock solution supply pipe 31 until it receives the signal at the L position equipped in the filtrate stock solution tank 36 and becomes the H position. To supply. The supply port 31a of the filtered stock solution supply pipe 31 is located on the set liquid level (H position) of the filtered stock solution.

  At this time, the filter drum 38 vacuum-sucks each filter chamber 62 and rotates it at a low speed. Further, the scraping blade 48 of the scraper device 46 is located at the surface position of the precoat layer 50 and moves forward at a predetermined speed. The forward speed at this time is 0.02 to 0.20 mm / min.

  The anionic polymer flocculant may be a constituent component of the powder flocculant, but may be supplied in the middle of the filtrate stock solution supply pipe 31.

  For this reason, when the polymer flocculant is added, the floc grows to 1 to 5 mm. The amount of the polymer flocculant added is, for example, 1.0 to 5.0 mg / L for wastewater whose SS concentration after coagulation (specified in Appendix 8 of the Environmental Agency Notification No. 59 of 1971) is 4000 mg / L. And

  If the addition amount of the polymer flocculant is excessive, the filtration resistance increases due to the viscosity of the excess polymer flocculant. If the amount is too small, the addition effect by the polymer flocculant, the increase in floc strength and the filter aid. It becomes difficult to make the diameter larger.

  Even when the flocs are grown, the flocs do not settle and the flocs are hardly destroyed because they are gently swirled and stirred by the cradle type arcuate stirring blade 106. In this case, the reciprocating cycle is 20 to 50 Hz.

  As described above, since the suction pressure in each filter chamber 62 is maintained at a degree of vacuum sufficient for filtration, flocs are well captured by the precoat layer to form a cake.

  Further, when the floc becomes too large without setting the stirring blade 106 and settles in the filtrate stock solution tank 36, it is returned to the agglomeration reaction tank 14 through the filtrate stock solution return pipe 37 from the bottom of the filtrate stock solution tank 36 as described above. The floc can be broken with a stirrer 22 or the like and re-prepared.

DESCRIPTION OF SYMBOLS 10 Aggregation reaction apparatus 11 Precoat tank 12 Waste water tank 14 Aggregation reaction tank 15 Powdery flocculant supply means 16 Vacuum filtration apparatus 36 Filtration stock solution tank 37 Filtration stock solution return piping 38 Filter drum 46 Scraper means

Claims (6)

In a facility for treating wastewater by supplying a filtration stock solution of a coagulation reactor that adds flocculant to wastewater to form floc and separating it into cake and clarified water,
The filtration separation device is a precoat type vacuum filtration device provided with a stock solution tank for storing a stock solution, a filter drum, and scraper means;
The agglomeration reaction apparatus comprises an agglomeration reaction tank equipped with a stirrer, a waste water supply means for supplying waste water to the agglomeration reaction tank, and a flocculant supply means for supplying a powdery flocculant.
Between the agglomeration reaction tank and the filtration stock solution tank, a filtration stock solution supply pipe for supplying the filtrate stock solution from the aggregation reaction tank to a set filtration stock solution surface position, and the filtration stock solution from the filtration stock solution tank to the aggregation reaction tank It has a filtration stock solution return pipe for returning,
Wastewater treatment facility characterized by that.   The filter drum has an inner cylinder portion concentrically arranged with a predetermined gap inside the outer cylinder portion, and a plurality of annular spaces between the inner cylinder portion and the outer cylinder portion are equally divided by a partition plate. The filter chambers are formed, and each of the filter chambers is connected to a branch pipe branched from a filtrate main pipe that also serves as a rotation shaft in the vicinity of the inner side surface in the rotation direction of the partition plate. The wastewater treatment facility according to claim 1.   The wastewater according to claim 1 or 2, wherein a stirring blade is disposed between a bottom wall of the filtrate stock solution tank and the filter drum so as to prevent sedimentation of flocs in the filtrate stock solution. Processing equipment.   The wastewater treatment method using the wastewater treatment facility according to any one of claims 1 to 3, wherein a pH buffer is used together with an inorganic flocculant as the powdery flocculant.   The wastewater treatment method according to claim 4, wherein a polymer flocculant is further used as the powder flocculant.   The wastewater treatment method according to claim 4 or 5, wherein the wastewater has a pH of 5.5 to 9.

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