WO2014091819A1

WO2014091819A1 - Method for removing suspended solids from wastewater

Info

Publication number: WO2014091819A1
Application number: PCT/JP2013/077977
Authority: WO
Inventors: 拓贄川; 俊介新井; 加藤　雄一郎; 和弘楠元; 正博島瀬; 優奥貫; 将司藤田; 大大山; 和司前田
Original assignee: 日鉄住金環境株式会社
Priority date: 2012-12-10
Filing date: 2013-10-15
Publication date: 2014-06-19
Also published as: JP6374157B2; JP2014133229A

Abstract

Provided is a method for separating out and removing coarse suspended solids from wastewater. Said method, which is extremely useful industrially, yields treated water having good water quality and makes it possible to: reduce the amount of flocculant added; substantially simplify the equipment used; and reduce the cost of said equipment, the cost of maintaining and operating same, and the cost of recycling generated precipitates. This method is also free of problems stemming from inorganic flocculants. This method, which uses at least one type of organic flocculant to flocculate, precipitate out, and remove suspended solids from wastewater, creates a state in which said organic flocculant(s) is/are present in turbulent water that contains at least both coarse suspended solids and fine suspended solids and has a flow rate of at least 0.5 m/s, making it possible to flocculate and precipitate out both coarse suspended solids and fine suspended solids with the same treatment and remove same simultaneously.

Description

Method for removing suspended solids from wastewater

The present invention relates to a method for removing suspended solids from wastewater, and more specifically, wastewater containing a large amount of suspended matter such as metal powder or oil having a particle size of 50 μm or more, which is generated in large quantities in a steelworks. In addition, using organic flocculants, the suspended solids can be coagulated and settled at once in a state of containing these coarse suspended solids, and these can be removed simultaneously. The present invention relates to a technology for removing suspended substances in wastewater.

For example, wastewater generated at the ironworks includes direct cooling wastewater in the continuous casting process, direct cooling wastewater in the rolling process, dust collection wastewater in the blast furnace, converter, electric furnace process, rainwater wastewater generated from the outdoor raw material storage yard, etc. There is a large amount. Moreover, in these wastewaters, as described below, not only fine suspended substances, but also particle sizes of metal powder such as iron, granulated slag, coal powder and coke powder are 50 μm or more. Of coarse suspended solids (hereinafter also referred to as coarse SS). As will be described later, when removing suspended substances from such waste water, first, the coarse suspended substances are first removed in advance by a method such as sedimentation separation, and the removed waste water is then removed using various flocculants. In many cases, fine suspended substances (hereinafter also referred to as fine SS) having a particle size of less than 50 μm are removed by coagulation sedimentation.

FIG. 5 is an example of a conventional method for removing suspended matter (SS) containing coarse SS and fine SS as described above contained in wastewater, and is a direct cooling in a rolling process of a steel material rolling line. An outline of wastewater treatment is schematically shown. As shown in FIG. 5, the direct cooling wastewater is recycled as direct cooling water after the SS is removed to become treated water. Therefore, the treated water is desired to be clearer with less suspended matter. Below, with reference to FIG. 5, the procedure of the process of the direct cooling wastewater currently performed is demonstrated. First, in a rolling process, cooling water is sprayed on the steel material surface from a spray nozzle etc., and steel material is cooled. The cooling water used at that time flows down to an open soot called scale sluice indicated by 1 in FIG. This is called direct cooling wastewater and contains various suspended substances. Specifically, in this direct cooling wastewater, a large suspended substance having a particle size of 50 μm or more called a scale peeled off from the surface of the steel material, a roll shaft lubricating oil used for casting or rolling, or rolling Oil, fine iron powder generated by friction between these rolls and steel materials, and the like are included, and at least coarse SS and fine SS are mixed. In addition, the direct cooling waste water produced in the continuous casting process in the steel material production line has the same property, and the treatment is often performed in the same manner as described above.

The large amount of direct cooling wastewater that has flowed down into the scale sluice 1 as described above is drained by a violent flow into a tank called a scale pit indicated by 3 in FIG. 5 and stored in the pit. The scale pit is mainly intended for the sedimentation separation of large scale (coarse SS) having a large particle size that is directly present in the cooling wastewater, and is a relatively small tank with an Over Flow Rate of about 10 m / hr or more. is there.

As described above, in the conventional treatment for the direct cooling wastewater generated from the continuous casting process or the rolling process, first, suspended matter having a large particle size (that is, coarse SS) is first formed in the scale pit 3. For the waste water from which the coarse SS has been separated after the precipitation separation, fine particles having a particle size of less than 50 μm (that is, in a coagulation sedimentation facility 8 or a filter 9 provided later, or an electromagnetic filter (not shown)) , The fine SS) is removed. Then, after removing the coarse SS and the fine SS as described above, the treated water is cooled by passing it through the cooling tower 4 or the like, and then supplied directly to the factory as cooling water again.

In the conventional method for removing suspended substances from directly cooled wastewater, which has been performed as described above, a flocculant is used for the purpose of efficiently suspending the suspended substances. The flocculant to be used is selected according to the properties of the wastewater, and it is common to use various flocculants in combination. For example, Patent Document 1 relating to a water treatment method for steel rolling wastewater has a step of injecting polyaluminum chloride (PAC), which is an inorganic flocculant, and an organic flocculant into raw water obtained by collecting water used for steel rolling. Based on this assumption, the concentration of suspended solids can be more greatly and advantageously reduced by adjusting these injection amounts. Further, in Patent Document 2, when oil-containing wastewater generated from the steel industry or the like is treated with PAC, a cationic dispersion type (co) polymer that is an organic flocculant is added, and then subjected to aggregation precipitation treatment and dehydration treatment. A method has been proposed. Patent Document 3 proposes to add a specific cationic organic flocculant to a wastewater mixed with mineral oil such as automobile industrial wastewater, and then add an anionic organic flocculant to aggregate and separate the flocs. Yes.

Furthermore, in Patent Document 4, in the water treatment method of direct cooling wastewater in the rolling process described above, when sulfuric acid bands or PACs of inorganic flocculants are used, sulfate ions and chlorine ions in the cooling water increase, and cooling water and There is a problem of promoting corrosion of equipment such as rolling mills and rolls in contact with each other and generating fine iron oxide (Fe ₂ O ₃ ) in the cooling water. It cannot be removed. In the technique described in Patent Document 4, as a countermeasure, aggregation treatment is performed using a cationic organic flocculant such as ammonia, an aliphatic primary amine, an aliphatic secondary amine, or a polycondensate of alkylenediamine and epichlorohydrin. However, it is said that it is effective to add a scale inhibitor specific to the treated water.

Further, Patent Document 5 relates to the treatment of converter exhaust gas dust collection water, which is one of waste water generated in a steelworks, and dust collection water containing dust obtained by wet dust collection processing using a wet dust collector. After separating coarse dust by introducing it into the coarse separator, when collecting and precipitating with a thickener, dust collection water and / or coarse separation between the coarse separators from the outlet of the wet precipitator It has been proposed to add a polymer flocculant to the vessel. And by setting it as the said structure, it is supposed that the recovery rate of the coarse-grain dust in a coarse-grain separator can be raised, the recycle cost of converter waste gas dust can be reduced, and the recycle efficiency can be improved.

JP 2012-139633 A JP 2008-006382 A Japanese Patent No. 4072075 Japanese Patent No. 3868521 Japanese Patent No. 4134914

As described above, for example, in the process of removing suspended substances from directly cooled wastewater generated in large quantities at a steelworks, multiple types of flocculants selected from various inorganic and organic flocculants are used. ing. Here, since the amount of direct cooling wastewater at the smelter is large, the cost for the flocculant becomes large. Therefore, development of a technology that achieves high coagulation sedimentation efficiency at a lower price and in a smaller amount is demanded. ing. Moreover, even if several types of flocculants are separately added to waste water in the prior art, the point of addition is usually after entering the water treatment facility. For example, in the example shown in FIG. 5, a flocculant may be added to the scale pit 3 described above, which is the first treatment tank in the water treatment facility, for the purpose of further precipitating the coarse SS. In this case, an inorganic flocculant is usually used as the flocculant. On the other hand, the organic flocculant is originally used to agglomerate fine SS to form a large floc and agglomerate and settle. In the example shown in FIG. 5, the waste water after the coarse SS is precipitated in the scale pit 3. It is used for the purpose of coagulating and precipitating fine SS inside. Specifically, in the example shown in FIG. 5, the organic flocculant is added to the vast sedimentation basin 8 that constitutes the coagulation sedimentation facility. And it may be necessary to accelerate | stimulate mixing with to-be-processed water, such as direct cooling wastewater, and a coagulant | flocculant using a stirrer. As a method for promoting the mixing, for example, a stirrer may be installed in the settling basin. However, when the settling pond is very large, a stirrer tank is provided in front of the settling basin, and the water to be treated is previously stored in the stirrer tank. And a flocculant are mixed and then introduced into a settling basin. In that case, in addition to the cost for the coagulant to be used, the equipment cost and the maintenance cost for the stirrer and the stirring tank are required separately, and therefore development of a treatment method that does not involve the use of a stirrer or the like is desired.

In the conventional treatment method, as described above, after the coarse SS is precipitated in the scale pit, the waste water from which the coarse SS has been removed is treated in the coagulation sedimentation facility. As described above, the suspended matter in the wastewater flowing into the stirring tank provided in the preceding stage of the settling basin is fine particles (fine SS) having a particle size of less than 50 μm. For this reason, even if flocs are formed using various flocculants, the sedimentation speed is at most about 2 to 3 m / hr, and is not rapid. Therefore, the conventional treatment method requires a large sedimentation basin having an Over Flow Rate that is lower than the sedimentation speed of flocs composed of fine SS. This means that the scale of the processing facility becomes extremely large.

On the other hand, in the case of wastewater containing suspended solids mainly composed of iron, such as direct cooling wastewater generated from continuous casting and rolling processes, an electromagnetic filter or filter is suspended instead of a large sedimentation basin. It is also used to remove turbid substances. In the facility illustrated in FIG. 5, the coagulation sedimentation facility having the sedimentation basin 8 and the filter 9 are used in combination. However, in addition to the equipment cost, electromagnetic filters and filters are cumbersome and expensive to maintain, and the backflow is intended to periodically discharge suspended substances captured by these filters. Cleaning is essential. Further, equipment and chemicals are required for the treatment of the waste water for backwashing.

Further, the technique described in Patent Document 4 has the following problems. As described above, in the removal of suspended substances in direct cooling wastewater generated from a continuous casting process or a rolling process, usually only an inorganic flocculant or an inorganic flocculant and an organic flocculant are used in combination. Corrosive anions such as Cl ^- and SO ₄ ^2- derived from the flocculant may be mixed into the treated water. In general, after the treated water is cooled, it is supplied again to the factory as cooling water. Therefore, when the concentration of the corrosive anions increases as the water evaporates in the cooling tower or the like, There is a risk of accelerating corrosion of piping and spray nozzles in the system.

In addition, in the removal treatment of suspended solids in such direct cooling wastewater, a large amount of high oil sludge in which the oil and solid suspended matter such as fine iron powder are firmly adsorbed is generated in the sedimentation basin. This high oil content sludge is disposed of as industrial waste or recycled as a raw material for making koji, and in most cases, a step for concentration and dehydration is required. However, as described in Japanese Patent Application Laid-Open No. 2002-275549, high oil content sludge is prone to concentration failure and dewatering failure and is also very poor in combustibility. There is a problem that oil vapor is generated without being able to burn sufficiently and accumulates in the exhaust gas dust collector, which may cause spontaneous ignition or explosion.

As a solution to the problems such as poor concentration and poor dehydration in the above-mentioned high oil content sludge, there are a method of concentrating and dewatering after mixing with other sludge having a low oil content, and a method of incineration. However, these methods cannot be used when the amount of low oil sludge to be mixed with the high oil sludge is limited or when the remaining capacity of the incinerator is not large. And is not a fundamental solution to the problem of poor dehydration. For this reason, it would be extremely useful if a fundamental solution to the problem in the high oil content sludge generated in a large amount by the conventional method could be found.

In addition, the technique described in Patent Document 5 is different from the above-described technique in that the wastewater to be treated is different and relates to the treatment of the converter exhaust gas dust collection water. It is to increase the recovery rate of the coarse dust separation performed in the coarse separator. Even with this method, it is essential to treat the fine particles that cannot be separated with a coarse separator by aggregating and precipitating with a thickener, and this is more effective than increasing the recovery efficiency of coarse dust separated with the coarse separator. I don't get it. Furthermore, the degree of improvement is said to be 1.1 to 1.3 times that in the case where no polymer flocculant is used in the coarse-grain separator, and the improvement effect is not sufficient. On the other hand, it would be extremely useful if a technology was developed that could remove coarse suspended substances and fine suspended substances at the same time.

From the situation as described above, the present inventors can obtain the following effects, particularly in the method for removing suspended substances in wastewater containing various suspended substances such as those generated in a steelworks, In addition, there is a technology that makes it possible to simultaneously remove at least the coarse suspended substances and the fine suspended substances in the wastewater, even if they contain oil. If it can be provided, it has come to be recognized as extremely useful. In the steelworks, for example, for various wastewater containing suspended solids such as direct cooling wastewater generated from continuous casting process and rolling process, which are often used in circulation, (1) With simplified equipment (2) Low maintenance costs, (3) Without the use of inorganic flocculants that could adversely affect treated water, (4) Suspended substances such as metals and coke in wastewater In addition, even if the oil is suspended, an economical and simple method for removing suspended substances in wastewater that does not generate sludge that is difficult to recycle by the treatment is desired.

Therefore, the present invention can achieve the following when, for example, separating and removing suspended substances in various wastewaters in which the coarse SS and the fine SS coexist, which occur in the steelworks as described above, An object of the present invention is to provide an industrially very useful method for removing suspended substances in wastewater. In other words, when the suspended solids are removed, the coarse SS and the fine SS are coagulated and settled by the same treatment, but the same or higher than that achieved by the conventional treatment method that has been treated separately. In addition to being able to treat the water with a clear water quality, it is possible to reduce the total amount of flocculant used compared to the conventional method, and to greatly simplify the equipment. The cost of equipment and maintenance can be reduced, and the recycling cost of the aggregated and settled sediment generated is reduced. In some cases, the corrosion of piping mixed into the treated water due to the use of inorganic flocculant It is an object of the present invention to provide a technology that can achieve a reduction in the amount of a substance that promotes the process.

The above object is achieved by the present invention described below. That is, the present invention is a method for removing suspended solids from wastewater by using a flocculant to remove suspended solids from the wastewater by coagulation and sedimentation, wherein at least one organic flocculant is used as the flocculant. A state in which at least a coarse suspended substance and a fine suspended substance coexist, the flow velocity is 0.5 m / second or more, and the organic flocculant coexists in turbulent water. The coarse suspended substance and the fine suspended substance are agglomerated and settled by the same treatment so that they can be removed at the same time. A processing method is provided.

As a preferred embodiment of the above-described method for removing suspended solids from wastewater of the present invention, the organic flocculant contains a coarse suspended solid and a fine suspended solid, and a flow rate of 0.5 m. When added to wastewater in a turbulent state at a speed of more than 1 second / second, coarse suspended matter and fine suspended matter coexist, and the flow rate is at least 0.5 m / second, resulting in a turbulent state. And a method for removing suspended substances in the waste water, which causes the organic flocculant to coexist in the water. Further, in this method for removing suspended solids from wastewater, the wastewater is wastewater generated at a smelter, and the position where the organic flocculant is added to the wastewater is not limited to coarse suspended solids and fine suspension. It can be any point from the point where the wastewater where turbid substances coexist is generated to the vicinity of the entrance of the water treatment facility.

As another preferred embodiment of the above-described method for removing suspended substances in waste water of the present invention, the organic agglomeration is previously performed on the water before becoming waste water in which the coarse suspended substances and fine suspended substances coexist. By adding this agent and further using this water, coarse suspended substances and fine suspended substances coexist, and the flow rate is 0.5 m / second or more, and turbulent water Examples thereof include a method for removing suspended substances in wastewater that causes a state in which the organic flocculant coexists. Furthermore, in this method for removing suspended matter in wastewater, the wastewater is wastewater generated in a steelworks, and the wastewater before the coarse suspended matter and fine suspended matter coexist. Water is treated water obtained after coagulating and precipitating the coarse suspended substance and the fine suspended substance in the presence of the organic flocculant by the same treatment and removing them simultaneously. In the system that circulates and uses the treated water, the addition of the organic flocculant to the treated water is from the point where the water is treated until the use standard is satisfied to the water supply point where the water is used. The method for removing suspended substances in wastewater according to claim 4 performed at any point.

As another preferred embodiment of the above-described method for removing suspended substances in waste water of the present invention, the following can be further mentioned. The coarse suspended substance has a particle diameter of 50 μm or more, the fine suspended substance has a particle diameter of less than 50 μm, and the coexistence state of these substances is a fine suspension. The ratio of the coarse suspended solid concentration to the suspended solid concentration (rough / fine) is 0.5 or more in terms of mass ratio; the number of lay nozzles in the turbulent water state is 8000 or more; The flocculant contains a cationic or amphoteric copolymer as a main component, the copolymer has a weight average molecular weight of 1,000,000 to 13 million, and a cation colloid equivalent value at pH 7 of 0.1 meq / the coarse suspended substance and the fine suspended substance are at least one of metal powder, granulated slag, coal powder or coke powder, and in some cases, any one of these substances Coexist with oil That is, after the coarse suspended substance and the fine suspended substance are coagulated and settled by the same treatment, the coagulated sediment is further removed.

Although it does not specifically limit as an organic flocculant used in the removal processing method of the suspended matter in the wastewater of this invention, For example, the following can be used conveniently. Furthermore, in the present invention, it is more preferable to design so as not to use an inorganic flocculant in addition to such an organic flocculant.
The following general formulas (1) and (2) are essential components and a cationic or amphoteric copolymer derived from a raw material monomer each containing 5 mol% or more is a main component, and the weight average molecular weight of the copolymer is The cation colloid equivalent value at pH 7 is 0.1 meq / g or more, more preferably 0.2 meq / g or more.

(In the above formula, R ₁ and R ₂ represent CH ₃ or C ₂ H ₅ , R ₃ represents H, CH ₃ or C ₂ H _5. X ⁻ represents an anionic counter ion.)

In addition, waste water treated by the method for removing suspended solids from waste water according to the present invention is applicable to any waste water in which coarse suspended solids and fine suspended solids coexist. However, for example, wastewater as described below that requires a large amount of treatment can be treated. The method for removing suspended substances in wastewater of the present invention includes, for example, direct cooling wastewater of steel in a continuous casting process of a steelworks, direct cooling wastewater of steel in a rolling process of a steelworks, a blast furnace of a steelworks, Dust collection wastewater in the converter, electric furnace process, rainwater wastewater generated from the outdoor raw material storage yard of the steelworks, and cooling wastewater generated when water granulation is obtained from the blast furnace water of the steelworks it can.

According to the present invention, for example, when separating and removing suspended substances in various wastewaters in which a coarse SS and a fine SS coexist, which are generated in a steelworks, the coarse SS and the fine SS are the same. It can be agglomerated and settled by the treatment, and the obtained treated water can have a water quality that is as clear or better than that achieved by the conventional treatment method in which these suspended substances are separately treated. An industrially very useful method for removing suspended solids from wastewater is provided. That is, by adopting the treatment process of the present invention, the coarse SS and the fine SS can be coagulated and settled by the same treatment, so that the total amount of the coagulant used can be reduced as compared with the prior art. It is possible, and the equipment can be greatly simplified, so the equipment and maintenance costs can be reduced. In addition to this, the cost of recycling the aggregated and settled sediment generated is reduced, and an inorganic flocculant is used. As a result, it is possible to achieve a reduction in the amount of substances that promote corrosion of the piping mixed into the treated water. In addition, the treated water obtained by the treatment process of the present invention exhibits a clear water quality equivalent to or higher than that achieved by the conventional treatment method, and thus can be recycled as it is, and further agglomerates are generated. The settled sediment has the advantage that it is easy to handle with good water separation, and the cost for processing the sediment can be greatly reduced as compared with the conventional method.

It is a schematic diagram which shows a suitable example at the time of applying the removal processing method of the suspended solids of this invention to the direct cooling wastewater process of a continuous casting process. It is a schematic diagram (Example 1) which shows another suitable example at the time of applying the removal processing method of the suspended solids of this invention to the direct cooling wastewater process of a continuous casting process. It is a schematic diagram (Examples 4 and 5) which shows another suitable example at the time of applying the removal processing method of the suspended solids of this invention to the direct cooling wastewater process of a hot rolling process. It is a schematic diagram which shows the comparative example (hot rolling process) with respect to the removal processing method of the suspended solids of this invention. It is a schematic diagram of the removal processing method of the suspended solid with respect to the direct cooling wastewater of the conventional hot rolling process.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. As a result of intensive studies to solve the problems of the prior art described above, the present inventors stopped using the inorganic flocculant, while adding the organic flocculant, or the organic flocculant After the addition of the organic flocculant, the coarse SS and the fine SS, the flow velocity is as fast as 0.5 m / second or more, and a state of coexistence in a turbulent state is generated, According to the very simple method, it is possible to coagulate and settle the coarse SS and the fine SS in the waste water with the same treatment. The present invention has been accomplished by discovering surprising facts that overturn the common sense of technology. As a result, according to the treatment method of the present invention described above, various effects listed below can be obtained as compared with the conventional suspension material removal treatment method. First, it is not necessary to use an inorganic flocculant that has been used to promote sedimentation of coarse SS, and it is not necessary to remove fine SS after the treatment of coarse SS. As a result, the equipment cost and the maintenance cost can be reduced as compared with the case of the conventional processing. Furthermore, since the precipitate obtained by coagulating and sedimenting coarse SS and fine SS in the same treatment is completely different from the sludge produced in the conventional treatment, it has good dewaterability and low oil content. The treatment is extremely easy, and the equipment cost and maintenance cost required for the conventional treatment for the treatment of the precipitate can be greatly reduced. Furthermore, the treated water obtained has no problem of chlorine ions and sulfate ions mixed due to the use of the inorganic flocculant, and at least equivalent to the treated water obtained by the conventional method for removing suspended solids. This is an epoch-making thing that can be reused as good cooling water without removing fine SS at a later stage.

More specifically, in the method for removing suspended solids in wastewater of the present invention, at least one organic flocculant is used, at least coarse SS and fine SS coexist, and the flow rate is 0. By producing a state in which the organic flocculant coexists in turbulent water at 5 m / second or more, the above-described excellent actions and effects can be obtained.

As described above, wastewater generated at a smelter is usually treated as coarse SS with a particle size of 50 μm or more, and as fine SS with a particle size of less than 50 μm. On the other hand, in the latter stage, the fine SS is treated by agglomeration and precipitation. However, in the present invention, these coarse SS and fine SS can be coagulated and settled by the same treatment, and these can be removed simultaneously. It is characterized by doing so. Although the coexistence state of coarse SS and fine SS in the wastewater to be treated is not particularly limited, according to the study by the present inventors, the ratio of coarse SS concentration to fine SS concentration (rough / fine) is the mass ratio. It was found that if the waste water is 0.5 or more, these can be treated well together in a stable state. Further, according to the study by the present inventors, the ratio of the coarse SS concentration to the fine SS concentration (coarse / fine) may be 0.5 or more, and if it is rather large, good processing can be performed. Even if the ratio of the coarse SS concentration to the SS concentration is about 100, it can be processed without any problem. As a result of confirmation by the present inventors, the ratio of coarse SS concentration to fine SS concentration (coarse / fine) of wastewater generated in the smelter depends on the specific gravity of the suspended matter. It was about 5 to 100 or about 10 to 70. Furthermore, according to the study by the present inventors, by applying the treatment method of the present invention to any of these wastewaters, suspended substances of different sizes in the wastewater are agglomerated by the same treatment. It can be allowed to settle, and the treated water becomes clear that could not be easily achieved by conventional treatment.

The meaning of “flow velocity of 0.5 m / second or more and turbulent state” as defined in the present invention means that the use state of the organic flocculant is treated in the conventional gentle flow state while stirring. Instead, it means that coarse SS, fine SS, and organic coagulant coexist in a vigorous fluid state where the remarkable effects of the present invention are obtained. The flow rate may be in a state of flowing at a speed of 0.5 m / second or more, but more preferably, the flow rate is in a state of flowing at a speed of 1.0 m / second or more. Further, the flow state needs to be a turbulent flow state. More specifically, the number of water lay nozzles is 8000 or more, and more preferably, the number of water lay nozzles is 10,000 or more. The coarse SS and the fine SS may coexist, and the organic coagulant may coexist. The above-described configuration of the present invention does not need to be achieved by providing a separate agitation facility or the like as in the case of the conventional suspension treatment method, and, as described below, the intense flow of wastewater generated in the factory. Since it can be achieved by skillfully using the suspended matter removal process, the equipment advantage is extremely large.

Examples of a method for producing the above-described water state defined in the present invention include a method of adding an organic flocculant to waste water in such a state as described in (1) below, and a coarse SS as described in (2) below. And a method of adding an organic flocculant in advance to the water before becoming wastewater in which the fine SS is coexisted.

(1) An organic flocculant is added to waste water in a turbulent state where a coarse SS and a fine SS coexist, the flow rate is 0.5 m / second or more. In this case, a preferable addition position of the organic flocculant includes any point from the point where the waste water where coarse SS and fine SS coexist to the vicinity of the inlet of the water treatment facility.
(2) The organic flocculant is added in advance to the water before becoming waste water in which coarse SS and fine SS coexist, and by using this water, coarse SS and fine SS coexist. In addition, the organic flocculant coexists in turbulent water at a flow rate of 0.5 m / second or more. As an example of the position of addition of the organic flocculant in that case, the water before becoming the waste water in which the coarse SS and the fine SS coexist is converted into the coarse SS and the fine SS in the presence of the organic flocculant. In a system that circulates and uses treated water obtained after coagulating and settling in the same treatment and removing these simultaneously, the point where the water was treated until the addition of the organic flocculant satisfies the use standard To the water supply point where the water is used.

As for the above (1) and (2), the direct cooling wastewater generated in the continuous casting process and rolling process of the steelworks will be specifically described as an example. "Any point from the point where the wastewater coexists to the vicinity of the entrance of the water treatment facility" includes the following points. First, when cooling water is sprayed from the spray nozzle or the like onto the surface of the steel material to cool the steel material, the cooling water becomes direct cooling waste water, so this point is a “waste water generation point”. In addition, “any point from the point where the wastewater is generated to the vicinity of the entrance of the water treatment facility”, after cooling the steel material, directly becomes cooling wastewater and flows down into an open rod called scale sluice. It flows to the scale pit, which is a water treatment facility, meaning a series of points in the meantime and nearby points.

As described above, in the present invention, the addition of the organic flocculant is performed at a point where the coarse SS and the fine SS coexist in the wastewater in which the coarse SS and the fine SS coexist. Or may be added in the vigorous stream immediately before being drained into the scale pit, added near the scale pit inlet, or added near the suction of the scale pit pump.

In addition, the “any point from the point where the water is treated before the use standard is met to the point where the water is supplied” as referred to in the above (2) refers to the sedimentation basin, the filtration tank after the scale pit Circulating flow from the exit point of the suspended solids removal equipment such as the machine, electromagnetic filter, etc. (that is, the treated water discharge port) to the waste water generation point through the cooling tower and from the downstream side of the scale pit to the scale sluice It means from the vicinity of the suction of the scale pit pump that generates the water to the waste water generation point described above.

According to the study by the present inventors, at least one kind of organic flocculant is used, and in particular, the organic flocculant is in a state in which coarse SS and fine SS coexist and fluidly flows with water. It was found that a high effect can be obtained by creating a coexisting state. More specifically, when the organic flocculant coexists with the coarse SS and fine SS in a vigorous mixed state, the coagulation / aggregation / sedimentation effect of the organic flocculant is more prominent, and the coarse SS and fine SS It was found that coagulation sedimentation occurs in the same treatment. Furthermore, in the state where these coexist, it is possible to obtain a high effect if a certain amount of time during which they are flowing vigorously is secured, and from the ease of the addition work, for example, as shown by 2 in FIG. It has also been found that it is preferable to add the organic flocculant as far as possible from the scale pit 3 of the scale sluice. If comprised in this way, an organic flocculant, coarse SS, and fine SS will be in a vigorous mixing state in any point where cooling wastewater flows through a scale sluice, for example. As a result, surprisingly, when discharged into the scale pit 3, the suspended matter containing coarse SS and fine SS directly in the cooling wastewater is coagulating / aggregating, or has already coagulated / aggregated. Therefore, it separates quickly into precipitate and clear treated water. Further, for example, in a system in which treated water is circulated and used as cooling water as illustrated in FIG. 1, the point as far as possible from the scale pit 3 is obtained, for example, before the waste water generation point described above. It is also effective to select up to the water supply point where the treated water will be used for the service water, and to add the organic flocculant to the service water before becoming the waste water. Of course, even if it is not a system in which treated water is circulated, an organic flocculant is added to the service water in advance, and by using the water, the “organic flocculant is defined as coarse SS and fine SS. May coexist and produce a coexisting state in a state of flowing vigorously with water ".

For these reasons, the inventors of the present invention are mixed vigorously when the organic flocculant is added to waste water or irrigation water at the points as described above, and in this state, first, the organic flocculant is mixed with the coarse SS where it coexists. On the other hand, it exhibits a particularly high agglomeration effect and a stronger agglomeration effect. As a result, agglomeration and agglomeration of coarse SS occur rapidly, and at this time, the coexisting fine SS is formed by the coarse agglomerate formed by this organic flocculant It is considered that the excellent effect of the present invention, that is, good aggregation and sedimentation by the same treatment, is obtained by being taken into the aggregate. In particular, when the wastewater is flowing in a ditch or liquid channel, the fine SS is actively moving in the wastewater, so it is inferred that the fine SS is more easily taken up by coarse aggregates. Yes. Further, the aggregated sediment / precipitate obtained by the treatment method of the present invention, which is considered to be obtained by such a mechanism, is sludge obtained by adding a flocculant and allowing it to settle in a sedimentation tank. This is clearly different from the above, and it has good dehydration and low oil content. For this reason, subsequent processing becomes extremely easy, and it is possible to significantly reduce the cost conventionally required for the secondary treatment of sedimentation / precipitate.

The organic flocculant used in the present invention is not particularly limited. For example, an organic flocculant selected from acrylic, polyamine and diallylammonium compounds can be used. According to the study by the present inventors, a more remarkable effect can be obtained by using the organic flocculants listed below. Specifically, a cationic or amphoteric copolymer derived from a raw material monomer containing 5 mol% or more of each of the following general formulas (1) and (2) as an essential component is the main component. It is effective to use those having a weight average molecular weight of 1,000,000 to 13,300,000 and a cation colloid equivalent value at pH 7 of 0.1 meq / g or more.

The above-mentioned cationic copolymer that can be used as an organic flocculant in the present invention is obtained from the raw material monomers each containing 5 mol% or more of the monomers represented by the above formulas (1) and (2). The average molecular weight and the cation colloid equivalent value at pH 7 can be derived by being within the ranges defined in the present invention. Specifically, the synthesis method described in Japanese Patent No. 2777732 can be used. In addition, amphoteric copolymers include, for example, a cationic monomer represented by the above formulas (1) and (2), and other monomers such as itaconic acid and acrylic as described in Japanese Patent No. 3352835. It can be obtained by the same method by appropriately mixing an anionic monomer such as an acid to obtain a raw material monomer.

Representative examples of the monomer represented by the above formula (1) include acryloyloxyethyltrimethylammonium chloride, hydrochloride of dimethylaminoethyl acrylate, and the like. A typical example of the monomer represented by the formula (2) is acryloyloxyethyldimethylbenzylammonium chloride. Examples of other monomers copolymerizable with these monomers include (meth) acrylamide, N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide and the like.

As a result of detailed studies on the organic flocculants obtained from the raw material monomers as described above, the present inventors have found that the above-mentioned raw material monomers are used in order to stably achieve the object of the present invention at a higher level. It has been found that the obtained cationic or amphoteric copolymer needs to satisfy the following requirements. Specifically, in the case of the organic flocculant described above, among the copolymers derived from the raw material monomers, the weight average molecular weight is 1 million to 13 million, and the cation colloid equivalent value at pH 7 is It is preferably 0.1 meq / g or more. The more preferable range varies depending on the balance between the weight average molecular weight and the cation colloid equivalent value, but the weight average molecular weight is 2 million to 11 million, and the cation colloid equivalent value at pH 7 is 0.2 to 1. It is preferable to use a weak cation to a strong cation of 9 meq / g.

If the weight average molecular weight is too smaller than the above range, a sufficient effect of removing SS cannot be obtained. On the other hand, if the weight average molecular weight is too large, the viscosity increases and it becomes difficult to use. The cation colloid equivalent value indicates the cation density in the organic flocculant, that is, the amount of the functional group exhibiting cationic property. The cation colloid equivalent value of the organic flocculant used in the present invention is a value measured by a colloid titration method, but is a value obtained by a titration method using a polyvinyl potassium sulfate solution.

The organic flocculants exemplified above are cationic, but the present invention is not limited to this, and anionic or nonionic organic flocculants can be used depending on the wastewater to be treated. . For example, according to the study by the present inventors, in the case of dust collection wastewater from a converter, it is more effective to use an anionic organic flocculant than to use a cationic organic flocculant. can get. In addition, when treating wastewater containing carbon-based dust such as coal and coke from rainwater drainage in a coal yard, the use of a slightly anionic or nonionic organic flocculant is suitable.

According to the study by the present inventors, the above-described organic flocculant mainly composed of a copolymer is discharged from a metal such as iron powder or rolling oil, for example, in a large amount from a hot rolling process of a steelmaking factory. Directly cooled wastewater in which coarse SS and fine SS coexist and suspended, in which oil components such as oil are suspended, is 0.1 mg / L or more with respect to the treated wastewater, for example, about 2 mg / L. By simply adding a small amount, suspended substances in the wastewater quickly aggregate and settle, and the supernatant becomes extremely clear with no turbidity observed visually. On the other hand, when this organic flocculant is used for the coagulation sedimentation treatment performed after removing coarse SS from wastewater in advance as in the prior art, the remarkable effect as described above cannot be obtained, and the fine SS Although there was a tendency to flocculate and settle, the supernatant was turbid with the naked eye and apparently not sufficient. This is because the remarkable coagulation / coagulation / sedimentation effect of the present invention brought about by the organic coagulant described above is exhibited when a fine SS and a coarse SS having a particle size of 50 μm or more coexist. This indicates that it is important to treat waste water in a state where coarse SS and fine SS coexist and float.

Further, according to the study by the present inventors, the organic flocculant is, as described above, for example, the direct cooling wastewater from the hot rolling process reaches the “scale pit” which is a water treatment facility. A higher effect can be obtained if it is added to a groove or liquid channel called “scale sluice” where the waste water up to this point is flowing vigorously. In other words, the suspended matter in the wastewater generated at the smelter contains a large amount of iron powder with a large specific gravity, so it is necessary to prevent sedimentation of the suspended matter. It is extremely fast, about 5 m / sec. According to the study by the present inventors, the organic flocculant is simply added to the flow of this fast wastewater, and the requirements specified in the present invention are satisfied. As a result, the remarkable effects of the present invention are achieved. Obtainable. Further, as described above, in this case, it is more effective to add the organic flocculant to the “scale pit” that is the water treatment facility more upstream. In particular, by adding the organic flocculant in the vicinity of the wastewater generation point, it will ensure a longer time for the wastewater to flow violently until it reaches the “scale pit” via the “scale sluice”. Although it becomes possible to do so, the higher effect of the present invention can be obtained. When organic flocculant is added, it is better to add the organic flocculant to the place where the wastewater is flowing vigorously and react the organic flocculant with coarse SS and fine SS in a vigorous mixed state. It shows that the coagulation, agglomeration and sedimentation effects due to the use of the agent are more prominent. As mentioned earlier, in the grooves and liquid channels called scale sluice, wastewater flows violently in a fast flow, for example, skillfully using this point before the wastewater is introduced into the water treatment facility If this is the case, it is not necessary to separately provide equipment such as a stirrer, and various industrially excellent effects described later can be obtained by a simple means of appropriately designing the point where the organic flocculant is added. become. For this reason, in order to achieve the requirements defined in the present invention, it is of course possible to keep the grooves and liquid paths called conventional scale sluice, but in some cases, for example, obstacles in the grooves and liquid paths Alternatively, the flow may be devised so that the flow becomes more turbulent by a method such as installing a rotating wing or the like. In any case, in the method for removing suspended substances in waste water of the present invention, it is more preferable to react the organic flocculant with the coarse SS and fine SS that are the targets of the removal treatment in a vigorous mixed state. By doing so, the amount of the organic flocculant used can be reduced, and a higher coagulation / aggregation / sedimentation effect can be obtained by the added organic flocculant.

The feature of the present invention is that at least coarse SS and fine SS coexist, and the flow velocity is 0.5 m / second or more, and the organic coagulant coexists in turbulent water. However, by setting the point where the organic flocculant is added to each of the points as mentioned above, it is possible to easily satisfy the above-mentioned requirements defined in the present invention. According to the treatment method of the present invention, the following industrially extremely useful effects can be obtained by the above-described extremely simple method. Four main effects or merits obtained by the processing method of the present invention will be described.

(1) Simplification of water treatment process By simply devising the addition point of the organic flocculant, coarse SS and fine SS in the wastewater are well mixed with the organic flocculant, so that fine iron powder and oil Fine iron powder and oil that could not be removed by the scale pits used to process coarse suspended solids are precipitated in the scale pits or similar relatively small tanks. Separation is possible, and clean treated water can be obtained on the exit side of the scale pit with reduced mixing of suspended solids to a level equivalent to or higher than conventional levels.
As a result, the fine iron powder and oil separation facilities such as a sedimentation basin, a filter, and an electromagnetic filter, which are required in the conventional process for removing fine SS in wastewater, are not required. In connection with this, the backwashing waste water treatment equipment required when using a stirrer, a filter, and an electromagnetic filter becomes unnecessary.
Moreover, since the inorganic flocculant is unnecessary in the method for removing suspended solids from wastewater according to the present invention, facilities such as a tank, a pump, a stirrer, and a liquid feed line are not required.
Therefore, when constructing a new facility for removing suspended solids from wastewater that is generated in large quantities at a steelworks and coexists with coarse SS and fine SS, Equipment space and construction costs can be greatly reduced.
(2) Reduction of operation and maintenance costs No sedimentation basin or filter is required, and treated water can be sent directly from the exit side of the scale pit to the cooling tower, reducing the number of necessary pumps and maintaining electricity costs. Administrative costs can be significantly reduced.
(3) Reduction of corrosion Since the inorganic flocculant is not required in the method for removing suspended solids in the waste water of the present invention, the corrosiveness contained in inorganic flocculants represented by polyaluminum chloride and sulfuric acid band. It is possible to remarkably reduce the presence of anions, such as Cl ^- and SO ₄ ^2-, in the treated water. For this reason, when the coagulated sediment and the treated water cooled are supplied again to the factory, it is possible to reduce the corrosion of the piping system and the surface of the steel material to be produced.
(4) Promotion of recycling of iron sludge Occurred in scale pits by adopting the method for removing suspended substances in wastewater of the present invention, and coagulating and sedimenting coarse SS and fine SS by the same treatment, A sludge composed of a large particle size scale, fine iron powder, and oil has good dewaterability and concentration, and has a low oil content per weight, and therefore can be easily transported and recycled.

FIG. 1 is a schematic view showing a preferred embodiment when the method for removing suspended solids in wastewater of the present invention is applied to direct cooling wastewater treatment in a continuous casting process. As shown in FIG. 1, the directly cooled wastewater generated from the continuous casting process flows down from the continuous casting line to the scale sluice 1, and the wastewater moves to the scale pit 3 while flowing violently inside the scale sluice 1. . In the example shown in FIG. 1, the organic flocculant 2 is added at the most upstream part of the scale sluice 1 through which the cooling wastewater flows directly. Therefore, the organic flocculant 2 and the directly cooled wastewater are mixed in a vigorous flow in the scale sluice 1 and drained into the scale pit 3. As a result, in the scale pit 3, the scale, fine iron powder, and agglomerated and aggregated oil in the wastewater are quickly settled and separated. Therefore, since the supernatant water in the scale pit 3 becomes clear, the supernatant water is pumped to the cooling tower 4 as it is. Finally, the treated water obtained by cooling in the cooling tower 4 is supplied to the factory again as direct cooling water.

The present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

<Examples 1 and 2 and Comparative Example 1>
The outline of this example is shown in FIG. In the present embodiment, similar to that shown in FIG. 1, the uppermost stream portion of the scale sluice 1 in which the spray cooling wastewater flows through the organic flocculant 2 with respect to the spray cooling wastewater generated in the continuous casting process. Added at. And the supernatant water obtained by the scale pit 3 was processed by the electromagnetic filter 5, cooled by the cooling tower 4, and used again as cooling water. In this example, the organic flocculant 2 was derived from a raw material monomer containing 20 mol% each of the two types of monomers represented by the general formulas (1) and (2) as essential components. A cationic compound mainly composed of 2- (acryloyloxy) ethyl] benzyldimethylammonium chloride / [2- (acryloyloxy) ethyl] trimethylammonium chloride copolymer (molar ratio = 60/20/20) Using. The weight average molecular weight was 3 million, and the cation colloid equivalent value at pH 7 was about 0.6 to 1.0 meq / g. Then, the organic flocculant was continuously added to the waste water in the scale sluice 1 so as to be 0 mg / l (no addition), 1 mg / l, and 2 mg / l. The ratio of coarse SS to fine SS (rough / fine) in the spray cooling wastewater treated above was about 5 to 20 in terms of mass ratio.

After the above treatment, the SS concentration and the n-Hex extract substance concentration (oil content) of the spray return water 6 (treated water A) and the spray direct water 7 (treated water B) were measured according to JIS K0102. In addition, spray return water here is the water (supernatant water) of the exit side of scale pit 3, and spray direct feed water is the water cooled after processing with the electromagnetic filter 5 (cooling water after a process). ). As Comparative Example 1, the SS concentration and the n-Hex extract substance concentration (oil content) were also measured when no organic flocculant was added.

Table 1 shows the results of the above-described organic flocculant addition test. As Example 1, the organic flocculant was added to 1 mg / l, so that the SS concentration of spray return water was 19 mg / l and the n-Hex extract substance concentration was 5 mg / l. Compared to Example 1), it was confirmed that the concentrations of both pollutants were halved. In addition, in the direct spray water, a good water quality with an SS concentration of 10 mg / l and an n-Hex extract concentration of 4 mg / l was obtained.

Further, when tested in the same manner as described above except that the organic flocculant was added at 2 mg / l as Example 2, the SS concentration of spray return water was 9 mg / l, and the n-Hex extract substance The concentration was 2 mg / l. The water quality of the spray return water is the same as that of the direct spray water treated with the electromagnetic filter 5 at the subsequent stage when the addition concentration of the organic flocculant is 1 mg / l. Therefore, when an organic flocculant is added so that it may become 2 mg / l, even if the process by the electromagnetic filter 5 is stopped, it is thought that favorable water quality can be maintained.

<Example 3>
In the present embodiment, for the purpose of determining whether or not it is possible to stop the treatment facility provided in the subsequent stage of the conventional scale pit 3, it is considered that the water quality is most deteriorated. The presence or absence was confirmed. Scale frying refers to dripping scale sludge, which is sediment deposited in the bottom layer of the scale pit, with a crumb heavy machine. At the time of scale frying, since the scales that have been accumulated are wound up, it is considered that the water quality temporarily deteriorates. In this example, the same constitution as in Example 1 was used, and the organic flocculant was continuously added upstream of the scale sluice so that the amount of wastewater was 2 mg / l.

Immediately after the start of scale frying (5 minutes after the start), just before the end (10 minutes before the end), and after the end (5 minutes after the end), the concentrations of the SS and n-Hex extract substances were measured. Table 2 summarizes the results of the water quality confirmation test when the scale was deep-fried. The SS of the spray return water was 7-8 mg / l, the n-Hex extract was 2 mg / l, and it was confirmed that the water quality was hardly changed even before and after the scale frying, which is considered to be the worst in water quality. From the above results, it was determined that the treatment facility after the scale pit, which was conventionally required, can be stopped by adopting the method for removing suspended solids from wastewater according to the invention.

<Examples 4 and 5 and Comparative Example 2>
In Examples 4 and 5 and Comparative Example 2, when hot-rolling the steel slabs produced in the steelmaking process, water used for roll cooling, cooling of steel and steel slabs, scale reduction, etc. (direct cooling wastewater) Targeted.
First, for comparison, it was processed by the process shown in FIG. 4 which is a process for removing suspended substances from the target water, and this was designated as Comparative Example 2. Specifically, first, the inorganic flocculant 2 ′ is added to the scale pit 3, and the coarse scale is settled and separated, and after removing suspended fine particles and oil in the settling basin 8 arranged in the subsequent stage, the cooling tower The water was cooled at 4 to obtain treated water, which was used as cooling water. The treated water A (6) and treated water B (7) in this case were analyzed, and the results are shown in Tables 3 and 4.

As Examples 4 and 5, the suspended solids in the wastewater were removed in the same manner except that the amount of the organic flocculant added was changed in the process shown in FIG. Specifically, as shown in FIG. 3, the organic flocculant 2 is added upstream of the scale sluice 1 in the same manner as in Examples 1 and 2 without adding the inorganic flocculant to the scale pit 3. did. And the treated water A of the exit side of the scale pit 3 was analyzed. The SS concentration and n-Hex extract concentration of the treated water were analyzed according to JIS K0102, and the test results are shown in Table 3.

As shown in Table 3, by adding the organic flocculant, SS and n-Hex extract substances in the treated water A could be removed better than in the treatment of Comparative Example 2. Further, the SS concentration of the treated water A treated by the method of Example 4 was 16 mg / l, and the n-Hex extract substance concentration was 2 mg / l. Furthermore, the SS concentration of the treated water A treated by the method of Example 5 was 4 mg / l, and the n-Hex extract substance concentration was 1 mg / l. From these results, the water quality was improved as compared with the treated water A in Comparative Example 2.

Table 4 shows the water quality of the treated water A of Examples 4 and 5 shown in Table 3 and the treated water B obtained as a result of treatment by the conventional treatment method of Comparative Example 2 shown in FIG. When these were compared, the concentrations of SS and n-Hex extract substances in the treated water A of Examples 4 and 5 were comparable or lower than the treated water B of Comparative Example 2. From this, it is considered that by adding the organic flocculant to the scale sluice without adding the inorganic flocculant, the pollutant can be removed to the same level or lower even if the sedimentation basin is excluded.

<Reference Example 6>
In order to clarify the present invention, the influence of the flow rate and Reynolds number of the water to which the chemical is added on the effect of the chemical is tested in laboratory tests for direct cooling wastewater of the rolling mill in eight ways. It was set, the treated water SS concentration was compared and evaluated, and the meaning of the requirements defined in the present invention was confirmed. As a result, as shown in Table 5, when the assumed flow velocity exceeds 0.5 m / sec, the treatment water turbidity is greatly improved. Even if the assumed flow velocity is increased further, the effect of improving the treatment water turbidity is I confirmed it was small.

From the above results, as shown in Table 5, when applying the treatment method of the present invention, by adding a necessary amount of organic flocculant at an appropriate position, coarse SS and fine SS And the coexistence of the organic flocculant occurs in turbulent water having a flow velocity of at least 0.5 m / second and a Reynolds number of 8000 or more. It was confirmed that the effect of the present invention is remarkably observed when the flow velocity is 1.0 m / second or more and the turbulent flow state water has a Reynolds number of 10,000 or more. For this reason, when applying the treatment method of the present invention, the flow rate and Reynolds number of the wastewater at each point from the point where the wastewater occurs until the wastewater moves and enters the treatment facility are measured. The organic flocculant is obtained so that the coarse SS and the fine SS coexist, and the organic flocculant coexists. It is preferable to determine the point at which is added.

Examples of utilization of the present invention include direct cooling wastewater for steel in the continuous casting process of the steelworks, direct cooling wastewater for steel in the rolling process of the steelworks, dust collection wastewater in the blast furnace, converter, and electric furnace processes of the steelworks Coarse SS and fine SS, such as rainwater wastewater generated from the outdoor raw material storage yard of the steelworks and cooling wastewater generated when granulated slag is obtained from the blast furnace pit of the steelworks It is mentioned that coarse SS and fine SS can be coagulated and settled by the same treatment from a large amount of waste water by an extremely simple method such as devising a position where an organic flocculant is added. By configuring as described above, facilities such as a sedimentation basin for processing fine SS, which has been required in the conventional processing, and the operation and maintenance associated therewith are unnecessary, and extremely economical processing is possible. Therefore, its use is expected. In addition, the supernatant water in the case where coarse SS and fine SS are coagulated and settled by the same treatment is less visually suspended than the treated water obtained by the conventional method. It is clear that there is no turbidity, and there is virtually no problem of adverse effects due to mixed chlorine ions, etc., which has been a concern in conventional methods using inorganic flocculants. From this point, it is extremely economical. Furthermore, the sediment (scale sludge) formed by agglomeration / aggregation of organic flocculant, coarse suspended solids and fine suspended solids is easy to handle, can be dredged with crumb heavy machinery, and solidified firmly. Therefore, the influence of the supernatant liquid on the water quality during the operation is small, and the treatment of the precipitate can be greatly simplified. In this respect, an extremely economical treatment is possible. As described above, the treatment method of the present invention is extremely simple, such as changing the point at which the organic flocculant is added, but the coarse SS and the fine SS are separately treated as compared with the conventional method. This makes it possible to reduce the type and amount of the flocculant to be used, and it is also possible to eliminate the need for a vast sedimentation tank required for the coagulation and precipitation of fine suspended substances. In addition, the treatment of the precipitate becomes very simple, and there is a possibility that facilities such as an electromagnetic filter and a filter may be unnecessary, and it can be expected that the conventional treatment method will be completely covered and a very large economic effect will be brought about. . The treatment method of the present invention can be applied to any wastewater in which coarse SS and fine SS coexist, but the amount of wastewater to be treated is extremely large. When applied to wastewater containing suspended solids generated in the process, a particularly great effect can be expected.

1: Scale sluice (open)
2: Organic flocculant 2 ': Inorganic flocculant 3: Scale pit 4: Cooling tower 5: Electromagnetic filter 6: Spray return water (treated water A)
7: Direct spray water (treated water B)
8: Sedimentation basin 9: Filter

Claims

A method for removing suspended solids from wastewater by using a flocculant to remove suspended solids from the wastewater by coagulation and sedimentation,
Using at least one organic flocculant as the flocculant,
At least a coarse suspended substance and a fine suspended substance coexist, and a flow rate of 0.5 m / second or more causes a state in which the organic flocculant coexists in turbulent water. In this way, the coarse suspended substance and the fine suspended substance are coagulated and settled by the same treatment, and these can be removed at the same time.
By adding the organic flocculant to waste water in a turbulent flow state where a coarse suspended substance and a fine suspended substance coexist, the flow rate is 0.5 m / second or more, The suspension material and the fine suspension material coexist, and the flow rate is 0.5 m / second or more, and the organic coagulant coexists in the turbulent water. A method for removing suspended substances in wastewater as described in 1.
The waste water is waste water generated in a steelworks,
The position where the organic flocculant is added to the wastewater is at any point from the point where the wastewater where coarse suspended substances and fine suspended substances coexist to the vicinity of the entrance of the water treatment facility. The method for removing suspended substances in wastewater according to claim 2.
The organic flocculant is added in advance to the water before becoming the waste water in which the coarse suspended substance and the fine suspended substance coexist, and by using this water, the coarse suspended substance and the fine suspended substance are used. The waste water according to claim 1, wherein the organic flocculant coexists in the turbulent water at a flow rate of 0.5 m / second or more. Method for removing suspended solids.
The waste water is waste water generated in a steelworks,
In the presence of the organic flocculant, the irrigation water before the waste water in which the coarse suspended substance and the fine suspended substance coexist is the same in the presence of the organic flocculant. In a system that circulates and uses treated water obtained after coagulating and sedimenting by treatment and removing these simultaneously, the addition of the organic flocculant is performed from the point where the water is treated until the use standard is satisfied. The method for removing suspended substances in wastewater according to claim 4, wherein the method is performed at any point up to a water supply point where water is used.
The coarse suspended substance has a particle diameter of 50 μm or more, the fine suspended substance has a particle diameter of less than 50 μm, and the coexistence state of these substances is a fine suspension. The removal of suspended substances in wastewater according to any one of claims 1 to 5, wherein the ratio of the coarse suspended substance concentration to the suspended substance concentration (rough / fine) is 0.5 or more by mass ratio. Processing method.
The method for removing suspended substances in wastewater according to any one of claims 1 to 6, wherein the number of lay nozzles of the turbulent water is 8000 or more.
The organic flocculant contains a cationic or amphoteric copolymer as a main component, the copolymer has a weight average molecular weight of 1,000,000 to 13 million, and a cation colloid equivalent value at pH 7 is 0.00. The method for removing suspended substances in wastewater according to any one of claims 1 to 7, wherein the amount is 1 meq / g or more.
The coarse suspended substance and the fine suspended substance are at least one of metal powder, granulated slag, coal powder, and coke powder, and in some cases, any of these substances and oil components may coexist. The method for removing a suspended substance in wastewater according to any one of claims 1 to 8.
The wastewater according to any one of claims 1 to 9, wherein the coarse suspended substance and the fine suspended substance are coagulated and settled by the same treatment, and then the coagulated sediment is further removed. A method for removing suspended solids.