JP6287009B2 - Method and apparatus for treating wastewater containing inorganic ions - Google Patents

Description

  The present invention relates to a method for treating wastewater containing inorganic ions such as metal ions and phosphate ions, and in particular, a part of the aggregated sludge is returned to the reaction tank, and an insolubilizing product generator such as alkali is added to the returned sludge. The present invention relates to a method for treating inorganic ion-containing wastewater.

  High density sludge method (HDS method: High Density Sludge) such as alkaline sludge method is known as a method for treating metal ion-containing wastewater to obtain highly concentrated metal hydroxide sludge that is rich in concentration and excellent in dewaterability. It has been. In the alkaline sludge method, alkali is added to a part of the sludge that is separated and returned by the treatment of the waste water containing metal ions.

  In the alkaline sludge method, the amount of insolubilized material (SS amount) and the amount of returned sludge produced by neutralization of raw water is used to stably obtain sludge with high concentration and excellent dewaterability and maintain good quality of treated water. It is important to maintain the ratio in a proper range.

  Japanese Patent Application Laid-Open No. 5-57292 discloses a heavy metal-containing wastewater in which the solid content of the return sludge mixed with alkali is 15 to 40 times, particularly 20 to 30 times the amount of insolubilized product produced by the reaction between alkali and raw water. The processing method is described.

  JP-A-8-24877 discloses the amount of insolubilized product produced by the reaction between alkali and wastewater in the method for treating ion-containing wastewater by the alkali sludge method, and the pH of the wastewater is around 3 to 8.5. It is described that it is calculated from the amount of alkali used until it becomes.

  Japanese Patent Laid-Open No. 2010-234300 describes that the flow rate ratio between the return sludge and the drawn sludge is constant. In addition, the publication discloses that after returning sludge to raw water, a polymer flocculant is added to perform a coagulation treatment.

  Note that fluorine ions and phosphate ions are also removed by the HDS method. In this case, a calcium compound or the like is used as the insolubilization product generator.

Japanese Patent Laid-Open No. 5-57292 JP-A-8-24877 JP 2010-234300 A

  An object of this invention is to provide the processing method and apparatus of the inorganic ion containing waste_water | drain which can produce | generate the sludge which is dense and has high dehydration property and a large sedimentation speed.

In the method for treating inorganic ion-containing wastewater of the present invention, an insolubilized product generator addition return sludge is added to the inorganic ion-containing wastewater to precipitate the insolubilized material, and then the solid-liquid separation treatment is performed to remove the sludge containing the insolubilized material from the treated water. A part of the separated sludge is returned to the sludge, and the insolubilizing agent is added to the returned sludge and added to the inorganic ion-containing wastewater, and the remainder of the sludge is extracted and discharged as sludge. In the treatment method (except the method using an aluminum-based inorganic flocculant and / or an iron-based inorganic flocculant) , the inorganic ion-containing wastewater to which the insolubilized product-generator-added return sludge is added has a cation group ratio. after addition of 10 to 50 mole% of the cationic polymer flocculant stirred by generating a floc, further anionic group ratio of 5 to 30 mole% of the low ionic anionic high content The coagulant is added, characterized in that granulating the agglomerated flocs.

The treatment apparatus for inorganic ion-containing wastewater of the present invention has a cation group ratio of 10 to the means for adding insolubilized product-generator-added return sludge to the inorganic ion-containing wastewater and to the liquid to which the insolubilized-product-generator-added return sludge is added. 50 mole% of cationic addition polymer flocculant stirred to means Ru to produce a floc, a liquid in which the cationic polymer flocculant is added, the anionic group ratio is 5 to 30 mol% and granulated to that means the aggregated floc by adding a low ionic anionic polymer flocculant, a solid-liquid separation means for the anionic polymer flocculant is solid-liquid separated by the liquid additive, the solid solution And an insolubilized product adding means for adding the insolubilized product generating agent to a part of the sludge separated by the separating means to make the insolubilized product adding return sludge (however, an aluminum-based inorganic flocculant and / or Or use iron-based inorganic flocculant To the exception of equipment.).

  In the present invention, when the inorganic ion-containing wastewater contains heavy metals, the inorganic ion-containing wastewater may be neutralized to precipitate heavy metal hydroxide before the return sludge is added.

As the cationic polymer flocculant, a low ionic cationic polymer flocculant having a cationic group ratio of 10 to 50 mol% is preferable .

  In the present invention, solid-liquid separation may be performed in a granulation-type coagulation sedimentation tank, and the SS concentration of the sludge blanket in the granulation-type coagulation sedimentation tank may be 2000 to 100000 mg / L.

  As a result of repeated researches by the present inventors, an insolubilized product generator added return sludge is added to inorganic ion-containing wastewater to precipitate insoluble salts, and then solid-liquid separation treatment is performed to separate sludge containing insoluble salts from the treated water. In the method of treating wastewater containing inorganic ions, a part of the separated sludge is used as return sludge, the insolubilization product generator is added to the return sludge, and the remainder of the sludge is extracted and discharged as sludge. After the cationic polymer flocculant is added and stirred to the inorganic ion-containing wastewater to which the product-forming agent is added, agglomerated flocs are generated, and then an anionic polymer flocculant is added to granulate the aggregated flocs. It was found that an agglomerate having high floc strength and high density can be formed by separating the produced granulated product from the treated water as sludge. In particular, it has been found that by using a cationic polymer flocculant having a cation group ratio of 10 to 50 mol% as the cationic polymer flocculant, it is possible to form a floc having a high density and not easily broken.

  The present invention is based on such knowledge. According to the present invention, even if the stirring floc is subjected to a shearing force due to stirring, it is difficult to make it finer, so that the fine floc is prevented from being mixed into the treated water as SS, and clear treated water is obtained. Further, since the granulated product has a high density and a high sedimentation rate, a high load treatment can be performed.

It is a flowchart for demonstrating the processing method of the inorganic ion containing waste_water | drain which concerns on embodiment. It is a flowchart for demonstrating the processing method of the inorganic ion containing waste_water | drain which concerns on embodiment. It is a flowchart of a comparative example. It is a flowchart of a comparative example.

  Hereinafter, embodiments will be described with reference to the drawings. FIG. 1 is a flow diagram of a wastewater treatment facility to which the inorganic ion-containing wastewater treatment method of the present invention is applied.

  Inorganic ion-containing wastewater (raw water) is introduced into the reaction tank 2 from the pipe 1, pH is adjusted by adding an acid such as hydrochloric acid or caustic soda, slaked lime, etc. from the pH adjuster addition means 3, and from the pipe 5. An insolubilized product generator addition return sludge is added, a cationic polymer flocculant is added from the addition means 4 of the cationic polymer flocculant, and stirred by the stirrer 6. The acid or alkali is added so that the pH detected by the pH meter 7 falls within a predetermined range. The agglomeration reaction liquid in the reaction tank 2 is transferred to the pellet formation tank 11 through the pipe 9, and from the anionic polymer flocculant addition means 10 at the outlet of the reaction tank 2 or in the middle of the pipe 9. A molecular flocculant is added. The agglomeration reaction liquid to which the anionic polymer flocculant is added is agitated by the agitator 12 in the pellet forming tank 11 to grow agglomerated pellets.

  A sedimentation tank 15 is juxtaposed to the pellet forming tank 11. The pellet forming tank 11 and the sedimentation tank 15 are connected via an outgoing pipe 13 and a return pipe 14. The forward pipe 13 communicates with the vicinity of the middle in the height direction of the tanks 11 and 15, and the return pipe 14 connects the upper parts of the tanks 11 and 15. The pellet sludge that has grown in the pellet forming tank 11 flows into the settling tank 15 through the forward pipe 13 together with water and settles. The water from which the pellet sludge has been separated in the settling tank 15 returns to the pellet forming tank 11 via the return pipe 14. The supernatant water in the pellet forming tank 11 is taken out of the system from the trough 11a of the pellet forming tank 11 through the treated water extraction pipe 16.

  The pellet sludge precipitated in the settling tank 15 is taken out by the sludge pump 17, and a part thereof is taken out from the system as a drawn sludge from the drawing pipe 18. The remainder of the sludge is introduced into the insolubilized product generating agent addition tank 20 through the return pipe 19, and the insolubilized product generating agent is added by the adding means 21 and stirred by the stirrer 22. The insolubilized product generator addition return sludge from the addition tank 20 is introduced into the reaction tank 2 through the pipe 5.

  In the embodiment of FIG. 1, the raw water is introduced into the reaction tank 2, but the raw water is introduced into the neutralization tank 31 as shown in FIG. Sludge and / or alkali mixed sludge) is added to adjust the pH to, for example, pH 5 to 9, and the insolubilized product additive added return sludge is introduced into the neutralization tank 31 and stirred by the stirrer 32, and then transferred by the transfer pipe 33. You may introduce | transduce into aggregation reaction tank 2 '.

  In the flow of FIG. 2, when a large amount of iron is contained in the water to be treated, a pre-neutralization tank is provided in front of the neutralization tank 31, and the sludge or alkali added and returned to the water to be treated in this pre-neutralization tank Sludge may be added, and the pH may be preferably adjusted to 3.5 to 4.5, particularly preferably 3.8 to 4.2. An alkali such as caustic soda or slaked lime can be added as necessary. In order to precipitate and remove iron, it is necessary to adjust the pH to 5 or more. However, if the pH is adjusted without pre-neutralization to pH 3.5 to 4.5, rather than the reaction with the hydroxide on the sludge surface, Densification does not occur due to increased reaction with hydroxide in water.

  In FIG. 2, instead of the pellet forming tank 11 and the sedimentation tank 15, a granulation type aggregation sedimentation tank 35 is provided. Flock-containing water from the transfer pipe 9 is introduced into the bottom of the granulation-type coagulation sedimentation tank 35, passes through the sludge blanket in an upward flow, and is taken out as treated water through the trough 37 and the pipe 38. The sludge blanket is agitated by the agitator 36. Sludge may be extracted from the bottom of the tank, or may be extracted from the middle part of the blanket in the vertical direction when the concentration is high. Other configurations in FIG. 2 are the same as those in FIG. 1, and the same reference numerals denote the same parts.

  1 and 2, the anionic polymer flocculant is added to the pipe 9, but in the present invention, an agglomeration reaction tank for adding the anionic polymer flocculant may be provided.

  In the present invention, inorganic ions in the waste water containing inorganic ions include metal ions such as Al, Ca, Cu, Zn, Cd, Pb, Fe, Co, Ni, Cr, Mn, phosphate ions, fluorine ions, and the like. Illustrated.

  As the insolubilized product generating agent for generating an insolubilized product from metal ions, alkali agents such as sodium hydroxide, potassium hydroxide, calcium hydroxide are suitable. When alkali is used as the insolubilization product generator, the metal ions in the raw water (treated water) react with the hydroxide adsorbed on the sludge surface and precipitate on the sludge surface, resulting in high density and dehydrating properties. Excellent sludge.

  As a phosphate ion insolubilization product generator, calcium salts such as calcium chloride, calcium hydroxide, and the like are suitable. As the fluorine ion insolubilization product generator, calcium salts such as calcium chloride, calcium hydroxide and the like are suitable.

  When the raw water contains fluorine ions as in the semiconductor manufacturing process waste water, sulfuric acid and / or sulfate or waste water containing these may be added to the neutralization tank 31 and the reaction tank 2. Thereby, the aggregation property, crystallinity, and sedimentation property of the calcium fluoride particles to be produced are improved. Sodium sulfate is preferred as the sulfate.

  The calcium salt or the like is added according to the phosphate ion concentration or the fluorine ion concentration in the raw water. In the case of treating phosphate ions, the addition amount of calcium salt and the like is preferably about 1 times the molar ratio and the total amount of 20 to 200 mg / L as residual Ca. In the case of treating fluoride ions, the addition amount of calcium salt or the like is preferably about the total amount of 1 times the molar ratio and 200 to 500 mg / L as residual Ca.

  When the inorganic ion-containing wastewater is a metal ion-containing wastewater, it is suitable for applying the present invention when the metal ion concentration in the wastewater is about 50 to 5000 mg / L. Specific examples of the metal ion-containing wastewater suitable for applying the method of the present invention include various factory wastewater and mine wastewater.

  When the inorganic ion-containing wastewater is phosphate ion-containing wastewater, it is suitable for applying the present invention when the phosphate ion concentration in the wastewater is about 10 to 5000 mg / L. Specific examples of the phosphate ion-containing wastewater include various factory wastewater, agricultural wastewater, dehydrated filtrate of activated sludge, anaerobic digestion and desorption fluid, and the like. It is suitable for applying the present invention when the concentration of fluorine ions in the waste water is about 15 to 20000 mg / L. Specific examples of the fluorine ion-containing waste water include various factory waste water and smoke waste water.

The acid or alkali is added so that the pH in the reaction tank 2 or the neutralization tank 31 is within a predetermined range. The preferred pH range varies depending on the metal species, pH 4 to 6 for Al, pH 5 to 7 for Cr, pH 8 to 10 for Fe ²⁺ , pH 8 to 10 for Zn, and pH 4 to 5 for Fe ^3+. 5. In the case of Cu, the pH is 6-8.

  The cationic polymer flocculant is preferably an acrylamide type, and the cationic group ratio is preferably 10 to 50 mol%, particularly 15 to 40 mol%, and more preferably 20 to 30 mol%. The weight average molecular weight of the cationic polymer flocculant is preferably about 12 million to 25 million, particularly about 15 million to 22 million. The addition amount of the cationic polymer flocculant is preferably 0.2 to 5 mg / L, particularly 1 to 3 mg / L.

  As such cationic polymer flocculants, those generally used as cationic polymer flocculants can be applied, and specifically, a copolymer of a cationic monomer and acrylamide can be suitably used. . Specific examples of the cationic monomer include dimethylaminoethyl acrylate and dimethylaminoethyl methacrylate (hereinafter, both compounds may be referred to as “dimethylaminoethyl (meth) acrylate”) or a quaternary ammonium salt thereof. Dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide (hereinafter, both compounds may be referred to as “dimethylaminopropyl (meth) acrylamide”) or their quaternary ammonium salts are preferably used. Yes, but not limited to this. The product form of the cationic polymer flocculant is not particularly limited, and the cationic polymer flocculant particles are dispersed in a powder product, a W / O emulsion, or an aqueous medium having a high salt concentration. It is applicable to the general distribution for waste water agglomeration treatment, such as dispersions.

  The anionic polymer flocculant is preferably an acrylamide type, and the anionic group ratio is preferably 5 to 30 mol%, particularly 5 to 20 mol%. The weight average molecular weight of the anionic polymer flocculant is preferably about 9 million to 20 million, particularly about 12 million to 18 million. The addition amount of the anionic polymer flocculant is preferably 0.2 to 8 mg / L, particularly 2 to 6 mg / L.

  As such an anionic polymer flocculant, those generally used as an anionic polymer flocculant can be applied, and specifically, a copolymer of an anionic monomer and acrylamide, or a hydrolysis of polyacrylamide. A decomposition product can be used. As a specific example of the anionic monomer, acrylic acid or a salt thereof can be suitably used. Polymers copolymerized with acrylamide using 2-acrylamido-2-methylpropanesulfonic acid or a salt thereof together with acrylic acid or a salt thereof as an anionic monomer are particularly useful in that they can be used stably over a wide pH range. It can be used suitably.

  The product form of the anionic polymer flocculant is not particularly limited, and is a powder product, a W / O type emulsion, or a disperser in which anionic polymer flocculant particles are dispersed in an aqueous medium having a high salt concentration. What is generally distributed for waste water agglomeration treatment, such as John, can be applied.

  The cationic group ratio is a molar ratio of the cationic monomer in the total molar amount of the nonionic monomer and the cationic monomer to be copolymerized. Anionic group ratio is the molar ratio of anionic monomer to the total molar amount of nonionic monomer and anionic monomer to be copolymerized (in the case of polyacrylamide hydrolyzate, nonionic repeating unit and anionic repeating unit Molar ratio).

  For example, in the case of a cationic polymer flocculant obtained by copolymerizing 80 mol of acrylamide and 20 mol of quaternary ammonium salt of dimethylaminoethyl acrylate, the ratio of the cation group is 20 mol% as follows.

Cationic group ratio [mol%] =
[Molar ratio of cationic monomer / (molar ratio of cationic monomer + molar ratio of nonionic monomer)] × 100
= [20 / (20 + 80)] x 100 = 20 [mol%]

  After adding the flocculant, a sedimentation accelerator such as sand may be added.

  In the present invention, the ratio Ac / Aa between the addition amount Ac of the cationic polymer flocculant and the addition amount Aa of the anionic polymer flocculant is preferably 0.1 to 1 and particularly preferably 0.4 to 0.8. .

The stirring strength of the reaction tank 2 and the neutralization tank 31 is preferably 100 to 500 s ⁻¹ in terms of G value, and the residence time is preferably 1 minute to 10 minutes.

  After the anionic polymer flocculant is added to the water containing floc formed in the reaction tank 2 or the aggregation reaction tank 2 ′, the anionic polymer flocculant is mixed with the floc floc before the anionic polymer flocculant sufficiently undergoes the aggregation reaction. Since it is preferable to flow into the pellet forming tank 11 or the granulation type coagulating sedimentation tank 35, the pellet forming tank 11 is preferably immediately after the addition of the anionic polymer flocculant (for example, 1 second to 1 minute, particularly 5 seconds to 30 seconds). Or it is preferable to flow into the granulation type coagulation sedimentation tank 35.

  In the pellet forming tank 11 or the granulation-type coagulating sedimentation tank 35, a sludge blanket holding aggregates (pellets) having a very high sedimentation speed is formed. Sludge blanket in which pellets are held not only by supplying pellets from outside the system in the initial stage of operation, but also by operating pellet forming tank 11 or granulation-type coagulating sedimentation tank 35 to grow aggregates to produce pellets Can be formed. When the water flowing into the bottom of the pellet forming tank 11 or the granulation type coagulating sedimentation tank 35 passes through a sludge blanket (hereinafter sometimes simply referred to as a blanket), the floc is adsorbed by the pellets in the blanket. Therefore, clear (for example, SS concentration 20 mg / L or less, particularly 10 mg / L or less) water flows out from the trough 11a or 37 as treated water.

  The blanket is sheared by a stirrer 12 or 36, and mechanical dehydration of the floc is promoted to form granulated pellets. When water containing an anionic polymer flocculant and flocs passes through the blanket, the flocs are firmly bonded to the pellets, so that suspended substances are removed and the pellets are hardly broken by shearing force. The granulated pellet (granulated sludge) is pulled out from the lower part of the settling tanks 15 and 35 as described above. Since dehydration from floc is promoted during the pellet formation process, the granulated sludge has a high density.

Stirring intensity of the blanket in the pellet formation tank 11 or granulated type coagulating sedimentation tank 35 is preferably set to 2～150S ^-1 particularly 5～100S ^-1 in G value. The SS concentration of the blanket is preferably 5,000 to 100,000 mg / L, particularly 10,000 to 60,000 mg / L. Moreover, it is preferable that the water flow LV of the pellet forming tank 11 or the granulation type aggregation and precipitation tank 35 is 5 to 90 m / hr, particularly 10 to 70 m / hr.

  The sludge concentration of the drawn sludge is preferably 5 wt% or more, particularly 10 wt% or more.

  The reason why the flocs with high mechanical strength are generated in the pellet forming tank 11 or the granulated coagulation sedimentation tank 35 is unknown in detail, but is presumed as follows. That is, SS in the raw water is charged neutralized by the cationic polymer flocculant to form a complex with the insolubilized product-added agent-added return sludge. By adding an anionic polymer flocculant to this, in addition to the electrostatic action of the cation and the anion, the hydrogen bonds of the nonionic chain based on the acrylamide unit entangle the flocs and strengthen the bond.

  Since the hydrogen bond by acrylamide (nonionic chain in the polymer flocculant) works greatly, it is preferable that the polymer flocculant has many nonionic chains. Further, a predetermined amount of cation chain is required for SS negative charge of water to be treated. Therefore, it is considered that the cationic polymer flocculant to be used is suitable to have a low cation degree and a large molecular weight. On the other hand, the anionic polymer flocculant is also preferably one having a large number of nonionic chains in the molecule because hydrogen bonds due to acrylamide (nonionic chains) work greatly. Further, a predetermined amount of anionic chain is required for the positive charge derived from the flocculant remaining in the flocs in the water to be treated. Therefore, it is considered that the anionic polymer flocculant used has a low anion degree and a large molecular weight.

  An anionic polymer is added without adding a cationic polymer flocculant by adding a cationic polymer flocculant having a cationic group ratio of 10 to 50 mol% together with the return sludge with an insolubilized product generator added to the raw water and stirring. Compared with the case where the flocculant is added, it is considered that the proportion of water molecules incorporated is small and flocs having high density can be formed. Subsequently, an anionic polymer flocculant is added and granulated in a mixed state with flocs, so that the flocs are strongly adsorbed on the pellets in the blanket zone by the adsorbing force of the anionic polymer flocculants, thereby coarsening. At this time, a hard flock having a higher density can be formed by using a low ionic material. However, if the ionicity is too low, there is a concern that the dispersibility may deteriorate and the adsorptive power may decrease, leading to a decrease in turbidity and an increase in the amount of drug used. There is a need to.

  Thus, since the coupling | bonding of flocs is strong, a pellet is destroyed at the time of granulation stirring, and it becomes difficult to refine | miniaturize. Thereby, the rate at which the fine SS flows out into the treated water can be reduced.

  By increasing the binding force between the flocks, the flock pore water is easily removed, and the mechanical dehydration action by stirring is promoted. Thereby, an aggregate with a large sedimentation rate is formed. Moreover, when the granulation is promoted, the density of the generated granulated sludge increases. For this reason, the equipment in the subsequent dehydration process can be reduced in size.

  Since the positive charge of the cationic polymer flocculant acts on the negative charge of SS, the amount of inorganic flocculant used can be reduced.

  In the present invention, the insolubilized product generating agent may be added to the entire amount of the returned sludge, or the insolubilized product generating agent may be added to a part of the returned sludge.

  By setting the solid content of the return sludge to be added to the water to be treated to 5 to 500 times the amount of the insolubilized product produced by the reaction of the water to be treated and the insolubilized product generator (hereinafter referred to as the return ratio) The size of the sludge is coarse, and it becomes sludge with excellent dewaterability, and solid-liquid separation can be stabilized. The amount is preferably 10 to 200 times. The optimum return ratio varies depending on the metal concentration contained in the water to be treated, but if it is less than 10 times the amount of sludge, the sludge does not precipitate on the sludge surface and the sludge does not increase in density. When the amount is larger than the amount, the sludge concentration is high, so that the sludge does not enlarge, becomes dispersed, and easily leaks from the sedimentation tank.

Since the metal in the water to be treated is deposited on the sludge surface, it is desirable that the surface area of the sludge is large. Therefore, if necessary, a finer means for refining the coarse pellets can be provided before adding to the water to be treated or before adding the alkali agent. At this time, the G value is 50 to 500 S ⁻¹ , preferably 100 to 300 S ⁻¹ .

[Example 1]
A simulated liquid containing 1,000 mg / L of Cu was prepared as waste water containing metal and used as test raw water. This synthetic raw water was treated by continuously passing through the inorganic ion-containing wastewater treatment apparatus of FIG. 2 at a water flow rate of 630 L / hr. The volume of each tank and processing conditions are as follows.
Neutralization tank 31: 150L
Aggregation reaction tank 2 ': 50L
Granulation-type coagulation sedimentation tank 35: 25L
Insolubilized product adding tank 20: 5 L
Insolubilizer: NaOH (25 wt% aqueous solution)
Amount of insolubilization product (NaOH) added: added so that the pH of the neutralization tank 31 is 8.5.

  The residence time in the neutralization tank 31 was 15 min, and HCl or NaOH was added so that the pH was 8.5 ± 0.1.

The return sludge concentration at this time was 12%. The return ratio was 20. (The SS concentration generated from the wastewater was 1540 mg / L in terms of Cu (OH) ₂ , so sludge was returned at 260 mL / hr and SS 12%.)

In the aggregation reaction tank 2 ′, 1 mg / L of the cationic polymer flocculant c having a cationic group ratio of 20 mol% was added as the cationic polymer flocculant. 2 mg / L of anionic polymer flocculant a having an anionic group ratio of 12 mol% was added to the pipe 9 as an anionic polymer flocculant. In the agglomeration reaction tank 2 ′, stirring was performed at a G value of 200S ⁻¹ for a residence time of 2 min.

In the granulation-type coagulation sedimentation tank 35, the water area load LV 60 m / hr, and the G value of the blanket zone was 50S- ¹ . The SS concentration of the blanket is 50,000 mg / L. The generated coarse floc was separated by settling and taken out as sludge. Further, the supernatant water that overflowed the trough 37 was treated water.

  Table 1 shows the results of analyzing the treated water and the extracted sludge after performing this operation for 150 hours.

[Comparative Example 1]
The same raw test water as in Example 1 was treated according to the flow shown in FIG. In the flow of FIG. 3, the sludge is not returned, the cationic polymer flocculant is not added, and the anionic polymer flocculant a ′ having an anion group ratio of 20 mol% is added to the aggregation reaction tank 2 ′. The flow is the same as that shown in FIG.

  Caustic soda was added in the neutralization tank 31 to adjust to pH 9, and the residence time was 5 min. In the aggregation reaction tank 2 ′, 3 mg / L of an anionic polymer flocculant a ′ having an anion group ratio of 20 mol% was added as an anionic polymer flocculant for a reaction time of 3 min. Next, solid-liquid separation was performed in a precipitation tank having a water area load LV of 1 m / hr. Table 1 shows the results of analyzing the treated water and the extracted sludge.

[Comparative Example 2]
In Example 1, the test raw water was treated under the same conditions except that sludge was not returned. Table 1 shows the results of analyzing the treated water and the extracted sludge.

[Comparative Example 3]
The same raw test water as in Example 1 was treated according to the flow shown in FIG. The flow in FIG. 4 is the same as that in FIG. 2 except that the anionic polymer flocculant a ′ having an anionic group ratio of 20 mol% is added to the agglomeration reaction tank 2 ′ without adding the cationic polymer flocculant. It is the same as the flow shown.

  The residence time of the neutralization tank 31 was 15 min, and alkali mixed sludge added with alkali as an insolubilized product generator was added to the returned sludge so that the pH was 8.5 ± 0.1.

The return sludge concentration at this time was 12%. The return ratio was 20. (The SS concentration generated from the wastewater was 1540 mg / L in terms of Cu (OH) ₂ , so sludge was returned at 260 mL / hr and SS 12%.)

  In the aggregation reaction tank 2 ′, 3 mg / L of anionic polymer flocculant a ′ having an anion group ratio of 20 mol% was added to make the reaction time 3 min. Subsequently, solid-liquid separation was performed in a precipitation tank having a water area load LV of 1 m / hr. Table 1 shows the results of analyzing the treated water and the extracted sludge after performing this operation for 150 hours.

  Table 1 shows the treated water Cu concentration, the treated water SS concentration, and the sludge concentration (SV24hr) after leaving the drawn sludge for 24 hours in Example 1 and Comparative Examples 1 to 3. The sludge concentration of the extracted sludge after standing for 24 hours was measured as an index for judging dewaterability.

[Discussion]
In Comparative Example 1, SV24hr is 10% of Example 1, and dense sludge cannot be obtained. In Comparative Example 2, the water flow LV was the same as that in the example, but SV24hr was 15%. In Comparative Example 3, SV24hr is concentrated to 76%, but the water flow LV is low.

[Example 2]
A potassium fluoride (KF) aqueous solution having a fluorine concentration of 150 mg / L was prepared and used as test raw water. This synthetic raw water was treated by continuously passing water through the inorganic ion-containing wastewater treatment apparatus of FIG. 1 at a flow rate of 0.63 m ³ / hr. The volume of each tank and processing conditions are as follows.
Reaction tank 2: 150L
Pellet formation tank 11: diameter 200 mm, height 750 mm
Insolubilized product adding tank 20: 5 L
Insolubilizer: CaCl ₂ (35 wt% aqueous solution)
Insolubilization product (CaCl ₂ ) addition amount: 500 mg-Ca / L-return sludge

HCl or NaOH was added to the reaction vessel 2 so that the pH was 7 ± 0.3. In addition, a 20 wt% aqueous solution of Na ₂ SO ₄ was added to the reaction tank 2 at an addition amount of 200 mg-SO ₄ / L.

  The return sludge concentration at this time was 15%. The return ratio was 40.

In the reaction tank 2, 1 mg / L of a cationic polymer flocculant c having a cationic group ratio of 20 mol% is added as a cationic polymer flocculant, and an anionic group ratio of 12 mol% is added to the pipe 9 as an anionic polymer flocculant. 3 mg / L of anionic polymer flocculant a was added. In the reaction tank 2, stirring was performed with a G value of 120S- ¹ .

In the pellet forming tank 11, the water area load LV was 20 m / hr, and the G value of the blanket zone was 20S- ¹ . The SS concentration of the blanket is 50000 mg / L. The generated coarse floc was taken out from the sedimentation tank 15 as sludge. Moreover, the supernatant water which overflowed the trough 11a was made into the treated water.

  Table 2 shows the results of analyzing the treated water and the extracted sludge after performing this operation for 150 hours.

[Comparative Example 4]
A potassium fluoride (KF) aqueous solution having a fluorine concentration of 150 mg / L was prepared as waste water containing metal, and used as test raw water. This synthetic raw water was treated by continuously passing water through the inorganic ion-containing wastewater treatment apparatus of FIG. 4 at a flow rate of 0.63 m ³ / hr. The volume of each tank and processing conditions are as follows.
Neutralization tank 31: 150L
Aggregation reaction tank 2 ': 50L
Granulation-type coagulation sedimentation tank 35: 25L
Insolubilized product adding tank 20: 5 L
Insolubilizer: CaCl ₂ (35 wt% aqueous solution)
Insolubilization product (CaCl ₂ ) addition amount: 500 mg-Ca / L-return sludge

HCl or NaOH was added to the neutralization tank 31 so that the pH was 7 ± 0.3. Further, a 20 wt% aqueous solution of Na ₂ SO ₄ was added to the neutralization tank 31 at an addition amount of 200 mg-SO ₄ / L.

  The return sludge concentration at this time was 10%. The return ratio was 40.

No cationic polymer flocculant was added to any tank. 3 mg / L of an anionic polymer flocculant a having an anion group ratio of 12 mol% was added as an anionic polymer flocculant to the aggregation reaction tank 2 ′. In the neutralization tank 31, stirring was performed with a G value of 120S- ¹ .

In the granulation-type coagulation sedimentation tank 35, the water area load LV4 m / hr and the G value of the blanket zone were 20S- ¹ . The SS concentration of the blanket is 50000 mg / L. The generated coarse floc was taken out from the sedimentation tank 15 as sludge. Moreover, the supernatant water which overflowed the trough 11a was made into the treated water.

  Table 2 shows the results of analyzing the treated water and the extracted sludge after performing this operation for 200 hours.

  As is apparent from the above results, the cationic polymer flocculant is added to the water to be treated containing metal ions, the cationic polymer flocculant is added, the anionic polymer flocculant is added, and the mixture is then stirred. Then, by granulating, then solid-liquid separation, and adding an insolubilized product generator to the returned sludge, a sludge that is dense and highly dewaterable, coarse, and has a high sedimentation rate can be formed.

2 Reaction tank 2 'Aggregation reaction tank 3 pH adjuster addition means 11 Pellet formation tank 15 Precipitation tank 20 Insolubilization product addition tank 31 Neutralization tank 35 Granulation type aggregation precipitation tank

Claims (6)

Add insolubilized product generator added return sludge to waste water containing inorganic ions to precipitate insolubilized material, then separate the sludge containing insolubilized material from the treated water by solid-liquid separation treatment,
A part of the separated sludge is returned to the sludge, and the insolubilizing product generator is added to the returned sludge and added to the inorganic ion-containing waste water.
In the treatment method of inorganic ion-containing wastewater that drains the remainder of the sludge and discharges it as sludge (except for the method using an aluminum-based inorganic flocculant and / or an iron-based inorganic flocculant) ,
After adding a cationic polymer flocculant having a cation group ratio of 10 to 50 mol% to the inorganic ion-containing wastewater to which the insolubilized product additive-added return sludge has been added and stirring to produce agglomerated flocs, further anions A method for treating inorganic ion-containing wastewater, comprising adding a low-ionic anionic polymer flocculant having a base ratio of 5 to 30 mol% to granulate the aggregated floc.   In Claim 1, the said inorganic ion containing waste_water | drain contains heavy metal, and neutralization which precipitates heavy metal hydroxide by neutralizing this inorganic ion containing waste_water | drain before adding the said insolubilization agent addition return sludge. An inorganic ion-containing wastewater treatment method, further comprising a step.   3. The method for treating inorganic ion-containing wastewater according to claim 1, wherein the cationic polymer flocculant is a low ionic cationic polymer flocculant having a cationic group ratio of 15 to 30 mol%. In any one of Claims 1 thru | or 3 , solid-liquid separation is performed in a granulation type coagulation sedimentation tank, and SS density | concentration of the sludge blanket in this granulation type coagulation sedimentation tank shall be 2000-100000 mg / L. A method for treating wastewater containing inorganic ions. Means for adding insolubilizing agent added return sludge to the waste water containing inorganic ions,
The liquid the insolubles formers added return sludge is added, it means for cationic group ratio Ru to produce added and stirred to flocs of 10-50 mole% cationic polymer flocculant,
To a solution the cationic polymer flocculant is added, and granulation to that means a flocculating floc anionic group ratio was added 5 to 30 mole% of the low ionic anionic polymer flocculant,
Solid-liquid separation means for solid-liquid separation of the liquid to which the anionic polymer flocculant is added;
An inorganic ion-containing wastewater treatment apparatus comprising: an insolubilized product generating agent added to a part of the sludge separated by the solid-liquid separating unit to obtain the insolubilized product adding return sludge. (However, the apparatus using an aluminum inorganic flocculant and / or an iron inorganic flocculant is excluded.) According to claim 5, wherein the inorganic ion-containing waste water contains heavy metals to precipitate heavy metal hydroxides for neutralization to inorganic ion containing waste water prior to adding the insolubles formers added return sludge An inorganic ion-containing wastewater treatment apparatus, further comprising neutralization means.

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