JP4522297B2 - Method and apparatus for treating wastewater containing inorganic suspended particles - Google Patents

Description

  The present invention relates to a method and an apparatus for treating waste water containing metal carbide, metal nitride, metal oxide and other inorganic suspended particles.

  For example, in wastewater from a factory that handles copper alloys, carbon (copper carbide) containing carbon and copper alloy components is contained as inorganic suspended particles. Wastewater containing such inorganic suspended particles is filtered by, for example, a 200-mesh drum filter, and inorganic suspended particles of less than 200 mesh that have passed through the drum filter are captured by a subsequent sand filtration device. However, the inorganic suspended solids in the concentrate that cannot pass through the drum filter cannot be removed by the sand filter.

Therefore, wastewater that cannot pass through the drum filter is added with an inorganic flocculant such as PAC, stirred and sent to the neutralization tank, and added with NaOH to adjust to a neutral region around pH 6.3 suitable for PAC reaction. Flock is generated in the coagulation tank. The flocs that have become huge from several mm to about 10 mm are settled and separated in a coagulation sedimentation tank, and the sediment is dehydrated and disposed of as a dehydrated cake. This method has been technically established as a coagulation sedimentation method using PAC, and has been adopted for a wide range of wastewater treatment (Patent Document 1).

  However, this method generates unnecessary hydrolysis products and aluminum hydroxide mud about 10 times as large as the target inorganic suspended particles. For this reason, the burden of the landfill disposal is large. In particular, in the case of wastewater containing substances whose landfill is restricted, such as heavy metals and specific chemical substances, there has been a problem in the treatment of dehydrated cake generated in large quantities. In addition, there is a problem that NaOH, which is a powerful drug, must be used for pH adjustment.

  Therefore, as shown in Patent Document 2, a method of aggregating wastewater containing suspended particles using a polymer-based aggregating agent that exhibits an aggregating effect in a smaller amount than an inorganic aggregating agent has been proposed. However, in the method of Patent Document 2, in order to solve the problem that the filterability of floc formed using a cationic polymer flocculant is poor, the formed floc is treated with a water-swellable anionic polymer flocculant. The content is that it is used for secondary aggregation.

  For this reason, a special water-swellable anionic polymer flocculant is required, resulting in an increase in processing cost. In addition, this method is limited to sewage wastewater, food factory wastewater, dyeing factory wastewater, chemical factory wastewater, etc. whose treatment objects can form flocs with cationic polymer flocculants. There was a problem that it was not suitable for the treatment of wastewater contained. Furthermore, the flock generation operation is not easy and takes time.

  In order to solve such problems, the present inventor has developed a method capable of coagulating wastewater containing positively or negatively charged inorganic suspended particles at a low cost without generating a large amount of dewatered sludge. Developed and filed as Japanese Patent Application No. 2005-32920. In this method, a cationic first polymer flocculant is added to concentrated water produced by filtering wastewater containing inorganic suspended particles with a drum filter, and then an anionic or nonionic second high-flocculating agent is added. In this method, a floc is formed by adding a molecular flocculant, and the thick water is separated into sludge and supernatant water, and the supernatant water is sand-filtered.

However, in the above wastewater treatment method, a stable floc may not be formed depending on the properties of the wastewater, and it may take time to form the floc. Sometimes exceeded 10 ppm.
JP 2002-66568 A Japanese Examined Patent Publication No. 62-29114

  The present invention solves the above-described conventional problems, and wastewater containing inorganic suspended particles can be agglomerated at a low cost without generating a large amount of dewatered sludge, and the properties of the wastewater have changed. In addition, the present invention has been made to provide a method for treating wastewater containing inorganic suspended particles that can always form stable flocs and stabilize the quality of treated water.

Invention of Claim 1 made | formed in order to solve said subject adds the 1st cationic polymer coagulant | flocculant to the concentrated water produced by filtering the waste_water | drain containing an inorganic suspended particle with a filter, Next, an anionic or nonionic second polymer flocculant was added to form a floc, and in a method of separating sludge and supernatant water by a thickener , the concentrated water was returned to the SS control tank and returned from the thickener. The concentration of SS is controlled to 500 to 1000 ppm by mixing with sludge, and the first polymer flocculant is added.

Further, the invention of claim 2 made to solve the above-mentioned problem is the addition of a cationic first polymer flocculant to concentrated water produced by filtering waste water containing inorganic suspended particles through a filter. Next, in the method in which an anionic or nonionic second polymer flocculant is added to form a floc and separated into sludge and supernatant water by the thickener, the concentrated water is led to the SS control tank and returned from the thickener. The first polymer flocculant is added after mixing with 60-200 mesh sludge and controlling SS to 300-1200 ppm.

Furthermore, in order to solve the above-mentioned problems, the invention of claim 3 is the addition of a cationic first polymer flocculant to concentrated water produced by filtering wastewater containing inorganic suspended particles through a filter. Then, in a method in which an anionic or nonionic second polymer flocculant is added to form a floc and separated into sludge and supernatant water by a thickener, the concentrated water is guided to the SS control tank, and 60 to 200 Alumina particles adjusted to a mesh are mixed by 0.1 to 1.0% to control SS to 250 to 1300 ppm, and a first polymer flocculant is added. Furthermore, it is preferable to introduce and mix the sludge returned from the thickener to the SS control tank. In the inventions according to claims 1 to 4, a hydration means can be used as necessary to control the concentration of SS.

In the inventions of claims 1 to 5 , it is preferable that the cationic first polymer flocculant is a copolymer of dimethylaminoethyl methacrylate (DMA) or a quaternary salt of DMA and acrylamide, It is preferable that the polymer flocculant 2 is anionic alone, a mixture of anionic and nonionic, anionic, nonionic, or nonionic.

The invention of the wastewater treatment apparatus containing inorganic suspended particles according to claim 8 includes a drum filter for filtering wastewater containing inorganic suspended particles, and an SS control tank for controlling SS of concentrated water discharged from the drum filter. , A first stirring tank for adding and stirring the cationic first polymer flocculant to the concentrated water with controlled SS, and further adding and stirring an anionic or nonionic second polymer flocculant. 2 stirring tanks, thickener for sedimentation and separation of flocs, sand filtration device for the supernatant water, means for separating sludge discharged from the thickener according to particle size, means for returning the separated sludge to the SS control tank, It is characterized by comprising.

In order to carry out the invention of claim 8 , it is preferable to provide the SS control tank with means for reducing SS by hydration and management equipment for mixing sludge from thickener.

In any of the first to fifth aspects of the present invention, the cationic first polymer flocculant is added to the waste water containing the inorganic suspended particles, and then the anionic or nonionic second polymer flocculant is added. A floc is formed by adding an agent and separated into sludge and supernatant water by a thickener. As described above, first, the first polymer flocculant having a positive charge is added to make the surface charge of the inorganic suspended particles positive, and the second high-molecular flocculant composed of the anionic or nonionic polymer flocculant is added. A molecular flocculant is added to form a neutral charge state and generate floc. Therefore, an inorganic flocculant is unnecessary, stable floc generation can be achieved in a short time, and agglomeration can be performed at low cost.

Moreover, in the invention of claim 1, since the concentrated water is introduced into the SS control tank, the sludge from the thickener is mixed, the SS is controlled to 500 to 1000 ppm and the polymer flocculant is added, so that stable floc formation is possible. , Solid-liquid separation becomes easy. In invention of Claim 2 , SS is controlled to 300-1200 ppm by throwing into the SS control tank the sludge by which the particle size was controlled as return sludge, and a floc with a large density can be formed. Such flocs have a large occlusion adsorption effect, a high impurity removal effect, solid-liquid separation is possible in a short time, and the clarity of treated water is improved. Further, in the invention of claim 4, by mixing 0.1 to 1.0% of alumina particles and controlling SS to 250 to 1300 ppm, the alumina particles act as a nucleating agent, and high density flocs are formed. It is formed to facilitate solid-liquid separation.

(Embodiment of Invention of Claim 1)
FIG. 1 is a block diagram showing an embodiment of the invention of claim 1, and raw water which is waste water containing inorganic suspended particles is first filtered by a drum filter 1. The drum filter 1 is preferably 60-mesh, and the inorganic suspended particles having a particle size of less than 60-mesh pass through the drum filter 1 and are sent to the sand filter 7 together with the filtered water to be captured. However, the inorganic suspended particles of a larger size are led to the SS control tank 2 as concentrated water.

This SS control tank 2 is unique to the present invention, measures the SS concentration of concentrated water, mixes sludge from the thickener , and controls the SS concentration to 500 to 1000 ppm. By controlling SS within this range, stable floc formation is possible in the next step. That is, if the concentration is less than 500 ppm, sufficient concentration cannot be achieved because the concentration is low, and if it exceeds 1000 ppm, SS that cannot be aggregated remains, which is not preferable. If necessary, water can be added from the hydration means 9.

  The concentrated water whose SS concentration is adjusted is added with the cationic first polymer flocculant in the first stirring tank 3, and then in the second stirring tank 4, the anionic or nonionic second polymer flocculant. Is added. It is preferable that all or part of the cationic polymer flocculant is dimethylaminoethyl methacrylate (DMA) or a copolymer of quaternary salt of DMA and acrylamide. The amount added is about 1 to 10 ppm per solid content (DS) of the waste water. The first polymer flocculant has a role of being electrically adsorbed to negatively charged inorganic suspended particles to form a floc and charging the whole positively. According to the results of experiments, a DMA having a molecular weight of 2.5 to 4.5 million, preferably a molecular weight of 3 to 4 million was suitable. A copolymer of DMA quaternary salt and acrylamide having a molecular weight of 700,000 to 7.5 million was optimal for floc formation.

  The reason why there is an optimal molecular weight for floc formation is that if the molecular weight is too large, the polymer itself is easily entangled into a spherical shape, the interaction with the suspended particles is weakened and floc formation is difficult, and the molecular weight is small. If the amount is too large, the degree of contact between the suspended particles and the polymer decreases, and it becomes difficult to form large flocs. In addition, when the polymer flocculant is a copolymer with another component as described above, the interaction between the suspended particles and the polymer is affected, so that the optimum molecular weight is shifted.

  In this way, the first polymer flocculant is added and stirred, and then the second polymer flocculant is added. This second polymer flocculant is used to change the state from a positively charged state by the first polymer flocculant to a state in which the charge becomes neutral. A mixture of a polymer flocculant and a nonionic polymer flocculant is used. In the case of mixing, the nonionic polymer flocculant should not exceed 90% of the total. This is because if the nonionic polymer flocculant is more than that, the effect of returning the charge to neutrality becomes insufficient. The amount of the second polymer flocculant added is sufficient to be about 1 to 5 ppm per solid content (DS) of the waste water.

  Here, as the anionic polymer flocculant and the nonionic polymer flocculant, it is particularly preferable to use a copolymer of sodium polyacrylate and polyacrylamide or polyacrylamide. The reason is not fully understood, but it is thought that molecular weight and colloidal equivalent are suitable. In particular, the combination of the first polymer flocculant composed of a quaternary salt of acrylamide and a quaternary salt of DMA having a molecular weight of 2.5 million to 4.5 million or a molecular weight of 700,000 to 7,500,000 makes the particle size smaller. A huge flock of 5 mm or more can be efficiently generated.

  When the charge is neutralized by adding and stirring the second polymer flocculant, the flocculant action increases, the flocs become enormous and the density increases, and the sedimentation tank 5 quickly settles. This operation can be carried out stably, and floc generation proceeds in a short time. The generated floc has good filterability and can be easily separated into sludge (floc) and supernatant water by thickener 6. Can do. As a result, most of the inorganic suspended particles contained in the wastewater are removed as sludge, so the supernatant water from which the floc has been separated passes through the sand filter 7 and is discharged after checking the SS in the monitoring tank 8. The

  According to the present invention, since no inorganic flocculant is used, the amount of dehydrated cake obtained by dehydrating flocs is small, and the processing cost can be suppressed. Further, since the SS concentration is controlled to 500 to 1000 ppm and a polymer flocculant is added, stable floc formation is possible.

(Embodiment of Invention of Claim 2 )
FIG. 2 is a block diagram showing an embodiment of the invention of claim 2 , and its flow is basically the same as that of the invention of claim 1. However, the flow of FIG. 2 is provided with a separation means 10 for separating a part of sludge (floc) separated by the thickener 6 and a return means 11 for returning the separated sludge to the SS control tank 2. The sludge of thickener 6 is sorted into a particle size of 60 to 200 mesh and returned. If necessary, the SS concentration is controlled by means of water.

In the invention of claim 2 , the concentrated water from the drum filter 1 is mixed with the return sludge in the SS control tank 2, and the SS is controlled to 300 to 1200 ppm. The allowable range of SS concentration is wider than that of the invention of claim 1, and a floc having a large density can be stably formed by mixing sludge whose particle size is controlled. Such a large floc has the advantage that the occlusion adsorption effect is large, the impurity removal effect is high, solid-liquid separation is possible in a short time, and the clarity of the treated water is improved.

(Embodiment of Invention of Claim 3 )
FIG. 3 is a block diagram showing an embodiment of the invention of claim 3 , and its flow is basically the same as that of the invention of claim 1. The flow of FIG. 3 is provided with a particle addition means 12 to the SS control tank 2, and for example, alumina particles adjusted to 60-200 mesh such as selben discharged from an insulator manufacturing plant are added to concentrated water. 0.1 to 1.0% is added and mixed, and SS is controlled to 250 to 1300 ppm. Moreover, you may add the process of a hydration means and a return sludge as needed. According to the third aspect of the invention, the added alumina particles act as a nucleating agent, and a floc having a high density is formed, so that solid-liquid separation is facilitated. Note that selben is a fired product of a composite of mullite, corundum, and silica, and has a specific gravity of 2.95. Mullite and corundum can also be used. As other means for adding particles, zirconia is expensive and has a specific gravity of 5.68, which makes it difficult to form flocs. Silica has a specific gravity of 2.66, which is too light, making it difficult to form flocs. Moreover, since a hydrate is produced in the formation process, it is not preferable for floc formation. Further, by adjusting the particle size to be used to 60 to 200 mesh, stable floc formation is possible, and solid-liquid separation is facilitated in a short time. If it is smaller than 60 mesh or larger than 200 mesh, it is difficult to form flocs, and solid-liquid separation becomes difficult.

Note that the inventions of claims 1 to 3 described above may be implemented alone or in combination. Examples of each invention are shown below.

(Embodiment of Invention of Claim 1)
Wastewater containing 1 to 10 ppm of metal carbide as inorganic suspended particles was filtered with a drum filter, and the concentration of the inorganic suspended particles was concentrated to 20 to 100 ppm. In the SS control tank, this concentrated water is added with return sludge and SS controlled to 700 ppm, dimethylaminoethyl methacrylate (DMA) is added as the first polymer flocculant, and polyacrylamide is added as the second polymer flocculant. A floc was formed, and solid-liquid separation was performed with a thickener. A part of the separated sludge was returned to the SS control tank without separating the particle size. When the range of SS control in the SS control tank is within the scope of the invention of claim 1 (Table 1) and outside the range (Table 2), the turbidity in the sedimentation tank and the turbidity in the monitoring tank It was measured. A comprehensive judgment was made and shown in the table.

(Embodiment of Invention of Claim 2 )
Wastewater containing 1 to 10 ppm of metal carbide as inorganic suspended particles was filtered with a drum filter, and the concentration of the inorganic suspended particles was concentrated to 20 to 100 ppm. Returned sludge is added to this concentrated water, SS is controlled to 700 ppm in the SS control tank, dimethylaminoethyl methacrylate (DMA) is added as the first polymer flocculant, and polyacrylamide is added as the second polymer flocculant. A floc was formed, and solid-liquid separation was performed with a thickener. In addition, a part of the separated sludge was classified into 60 to 200 mesh and returned to the SS control tank. Table 3 shows a case where the particle size of the returned sludge is out of the range of 60 to 200 mesh. In Table 3, the SS controllable range is expanded from that in Table 1.

(Embodiment of Invention of Claim 3 )
Wastewater containing 1 to 10 ppm of metal carbide as inorganic suspended particles was filtered with a drum filter, and the concentration of the inorganic suspended particles was concentrated to 20 to 100 ppm. Returned sludge is added to this concentrated water, SS is controlled to 700 ppm in the SS control tank, and 0.5% of coconut selben separated into 60 to 200 mesh is added, and then dimethylaminoethyl as the first polymer flocculant. Methacrylate (DMA) was added, polyacrylamide was added as a second polymer flocculant to form flocs, and solid-liquid separation was performed with a thickener. A part of the separated sludge was returned to the SS control tank without separating the particle size. The case where the range of SS control in the SS control tank is within the scope of the invention of claim 3 was evaluated and shown in Table 5. In addition, Table 6 shows the case where it was out of the range of claim 3 . In Table 5, the SS controllable range is further expanded than in Table 3.

It is a block diagram which shows embodiment of invention of Claim 1. It is a block diagram which shows embodiment of invention of Claim 2 . It is a block diagram which shows embodiment of invention of Claim 3 .

DESCRIPTION OF SYMBOLS 1 Drum filter 2 SS control tank 3 1st stirring tank 4 2nd stirring tank 5 Sedimentation tank 6 Thickener 7 Sand filtration apparatus 8 Monitoring tank 9 Watering means 10 Sorting means 11 Returning means 12 Particle addition means

Claims (9)

Add a cationic first polymer flocculant to concentrated water produced by filtering wastewater containing inorganic suspended particles with a filter, and then add an anionic or nonionic second polymer flocculant In the method of forming flocs and separating sludge and supernatant water by thickener, the concentration of SS is controlled to 500-1000 ppm by introducing concentrated water to SS control tank and mixing with sludge returned from thickener. A method for treating wastewater containing inorganic suspended particles, wherein the first polymer flocculant is added.   Add a cationic first polymer flocculant to concentrated water produced by filtering wastewater containing inorganic suspended particles with a filter, and then add an anionic or nonionic second polymer flocculant In this method, flocs are formed and the thickener is separated into sludge and supernatant water. A method for treating wastewater containing inorganic suspended particles, wherein the first polymer flocculant is added while controlling the concentration of the catalyst to 300 to 1200 ppm.   Add a cationic first polymer flocculant to concentrated water produced by filtering wastewater containing inorganic suspended particles with a filter, and then add an anionic or nonionic second polymer flocculant In the method of forming flocs and separating the sludge and the supernatant water with a thickener, the concentrated water is introduced to the SS control tank, and 0.1 to 1.0% of alumina particles adjusted to 60 to 200 mesh are mixed. Then, after controlling SS to 250-1300 ppm, the 1st polymer flocculant is added, The processing method of the waste_water | drain containing the inorganic suspension particle characterized by the above-mentioned. 4. The method for treating wastewater containing inorganic suspended particles according to claim 3 , wherein the sludge returned from the thickener is further mixed. The method for treating wastewater containing inorganic suspended particles according to any one of claims 1 to 4 , wherein water is added as means for controlling the concentration of SS. The cationic first polymer flocculant is dimethylaminoethyl methacrylate (DMA) or a copolymer of quaternary salt of DMA and acrylamide, according to any one of claims 1 to 5. A method for treating wastewater containing inorganic suspended particles. The second polymer flocculant is any one of anionic type, a mixture of anionic type and nonionic type, anionic type, nonionic type, and nonionic type, according to any one of claims 1 to 5. A method for treating wastewater containing inorganic suspended particles. A drum filter for filtering waste water containing inorganic suspended particles, an SS control tank for controlling SS of concentrated water discharged from the drum filter, and a cationic first polymer flocculant in the SS-controlled concentrated water A first agitation tank for adding / stirring, a second agitation tank for adding / stirring an anionic or nonionic second polymer flocculant, a thickener for sedimentation and separation of flocs, and sand filtration of the supernatant water An apparatus for treating wastewater containing inorganic suspended particles, comprising: an apparatus; means for separating sludge discharged from a thickener according to particle size; and means for returning the separated sludge to an SS control tank . The apparatus for treating wastewater containing inorganic suspended particles according to claim 8 , wherein means for supplying alumina particles is provided in the SS control tank.

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