JP2019037956A - Method and device for water treatment of organic wastewater containing oil - Google Patents

Abstract

To provide a method and a device for treating organic wastewater containing oil and organic matter.SOLUTION: In organic wastewater containing oil and organic matter, a cationic organic polymer flocculant is added to form flocculated floc (flocculation treatment). The treated water containing the flocculated floc is mechanically solid-liquid separated, and the mechanically solid-liquid separated liquid is biologically treated. The separated sludge generated in at least one of the biological treatment and the post-treatment after the biological treatment is returned to the aggregation treatment step or the former stage thereof, and the mixed liquid 2 including the separated sludge 11 and the organic drainage is subjected to flocculation treatment and subsequent steps.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a water treatment method and treatment apparatus for organic wastewater containing oil, and particularly relates to a treatment method and treatment apparatus that can be used for removing oil from wastewater containing oil such as in the food processing industry and beverage factories. .

  Conventionally, biological treatment using microorganisms has been used for wastewater treatment, but wastewater containing oil (hereinafter referred to as oil-containing wastewater) requires much time for biodegradation, and if the surface of the microorganism is covered with oil, the microorganism Respiration and fermentation were hindered, leading to inactivation of microorganisms.

  Further, among biological treatments, the membrane separation activated sludge method (MBR method) also has a problem that solid-liquid separation becomes difficult due to the oil adhering to the membrane surface. Therefore, when using biological treatment, it is necessary to remove an appropriate oil content.

  Examples of the method for removing oil from the oil-containing wastewater include an oil trap, a coagulation sedimentation treatment, and a pressurized flotation treatment. The following techniques are known as conventional techniques of this type.

  Patent Document 1 describes a wastewater treatment for decomposing oils and fats by adding a microorganism having excellent oil decomposition characteristics to wastewater instead of a pressurized flotation separator. However, management of such microorganisms is difficult, and the added bacteria do not always grow, so that it is difficult to stably grow the bacteria, and the treatment state often becomes unstable.

  Moreover, it is necessary to continuously add microorganisms to maintain the microbial activity, but the price is high, and due to technical problems and cost problems, full-scale spread has not been achieved.

  Patent Document 2 describes a wastewater treatment that improves the solids recovery rate by generating finer bubbles as compared with a conventional pressurized flotation separation treatment. However, the basic principle of attaching bubbles to solids is the same as before, and bubbles are attached to the removed solids.

  Therefore, floss accumulates in the upper part of the froth storage tank, there is a problem that the sludge supply concentration to the dehydrator fluctuates and the moisture content of the dehydrated sludge fluctuates. Due to the presence of gas inside, there are cases where the operation becomes idle and the transfer becomes impossible. Therefore, in patent document 2, a solid substance cannot be sludge-treated as it is, and a defoaming tank for separating bubbles is required, which increases the facility and the maintenance cost.

  In patent document 3, although an inorganic flocculant is used together, the metal hydroxide derived from an inorganic flocculant may generate | occur | produce and an inorganic sludge generation amount may increase from inflow SS. Moreover, every time the properties of the raw water fluctuate, it is necessary to adjust the chemical injection volume, pressurized air volume (gas-solid ratio), floss scraping speed, floss scraping interface height, etc. There is a problem.

  In Non-Patent Document 1, a flocculant is injected into raw water and stirred in a flocculation reaction tank, then a part of this liquid is used as pressurized water to dissolve air, and mixed with the flocculated stirring liquid to attach bubbles to the floc. A pressure levitation treatment method is described in which it is allowed to flow into the levitation separation tank. In this treatment method, fine bubbles also adhere to the oil-containing sludge scraped at the top. Concentration does not proceed in the state where bubbles are attached, and there are problems such as a problem that the subsequent sludge treatment facility becomes large and cavitation occurs in the transfer pump to prevent good operation.

Japanese Patent Laid-Open No. 2002-018481 JP 2006-297239 A JP 2003-2111293 A JP 2007-307512 A JP 2010-264417 A

Water treatment engineering edited by Tetsuo Ide, Gihodo Publishing Co., Ltd. Mechanical equipment standard specifications Published in 2016, Sewerage Business Support Center

  In such a conventional technique, when the oil-containing wastewater is treated and the biological treatment is performed at a later stage, the pressure levitation treatment method and the coagulation sedimentation treatment method, which are conventional techniques, are often performed as pretreatment. FIG. 1 is a flow sheet showing an example of a pressure levitation treatment method as one method of the prior art.

  In the flocculation and pressure levitation treatment, first, an inorganic flocculant and an organic polymer flocculant (A) are added to flocculate oil to form flocs. Next, by injecting pressurized water in which air is dissolved in the pressurized levitation tank, the flock is levitated on the surface of the pressurized levitation tank.

  The floc that floats on the surface of the pressurized levitation tank is called floss or sludge, but here it is called oil-containing sludge. Finally, the oil-containing sludge that floats above the water surface is discharged out of the system with a scraper, and the intermediate water in the pressurized flotation tank becomes treated water. Such a cohesive pressurization levitation process has the following problems.

(1) Since two types of inorganic flocculants and organic polymer flocculants are used, facilities such as a tank for each chemical, a dissolution tank, and a supply pump are required, which increases the investment amount.

(2) Since it is necessary to appropriately control the injection rate of each medicine, the operation management work becomes complicated.

(3) There are many operation management items such as the amount of dissolved air, the amount of pressurized water, adjustment of scraping speed, etc., and the operation management work becomes complicated.

(4) Since the inorganic flocculant is acidic, an additional step of adding an alkali (eg, caustic soda) to obtain a pH suitable for the reaction is required depending on the amount of the inorganic flocculant, and the operating cost is high.

(5) Since sludge derived from the metal in the inorganic flocculant is generated, more oil-containing sludge is generated than the amount of inflow solids.

(6) Since phosphorus dissolved in the waste water or existing as a solid is aggregated and discharged as oil-containing sludge, phosphorus as a nutrient is required in the subsequent biological treatment.

(7) The water content of oil-containing sludge is as high as 94 to 98%, and a large amount of oil-containing sludge is generated. For this reason, a dehydration treatment facility using another type of organic polymer flocculant (B) is required. Moreover, in order to remove the adhering fine bubbles, a deaeration treatment facility (such as a deaeration tank) equipped with a stirring device is also required as a pretreatment.

  The present invention has been made in view of the above-mentioned problems, and the object of the present invention is to remove excessive inorganic nutrient sources (such as phosphorus) of microorganisms in a method and apparatus for treating organic wastewater containing oil. Therefore, an object of the present invention is to provide a method and an apparatus that can reduce the consumption of alkalinity, suppress the generation of sludge derived from a flocculant by a dehydration process at a low water content, and reduce the amount of sludge to be discharged.

  In order to solve the above problems, the present invention can be configured as follows.

(I) The present invention relates to a treatment method for treating organic wastewater containing oil and organic matter, and a cationic organic polymer flocculant is added to the organic wastewater to form treated water containing coagulated flocs of oil and organic matter. A coagulation treatment step, a mechanical solid-liquid separation step for mechanically solid-liquid separating the treated water containing the coagulation floc into the coagulation floc and a separation liquid, and A biological treatment step to be treated, and the separated sludge generated in either or both of the biological treatment step and the post-treatment after the biological treatment step is separated from the aggregation treatment step and the aggregation treatment step. Returning to at least one of the processes and processing.

(II) The post-treatment is a step different from the mechanical solid-liquid separation step, wherein the treated water from which organic substances have been removed in the biological treatment step is further solid-liquid separated to obtain the separated sludge. It is a process.

(III) It further has a dehydration step, and the dehydration step dehydrates at least one kind of sludge selected from the above-described separated sludge and the oil-containing sludge generated in the mechanical solid-liquid separation step, It is a process for obtaining dehydrated sludge.

(IV) The separated sludge returning step is characterized in that it is returned according to at least one of the oil concentration and SS concentration of the organic waste water.

(V) Furthermore, the present invention relates to a treatment apparatus for organic wastewater containing oil, wherein the treatment apparatus is pH-adjusted for adjusting the pH of the organic wastewater containing oil and organic matter, and the pH is adjusted. The organic waste water is mixed with a cationic organic polymer flocculant to agglomerate oil and organic matter to obtain treated water containing agglomerated floc, and the treated water containing the agglomerated floc is separated from the agglomerated floc and the separation liquid Solid-liquid separation means for separating the liquid into solid-liquid, biological treatment means for removing organic matter in the separated liquid-solid separation and separating it into sludge and treated water, sludge produced by the biological treatment, and the organism Returning means for returning at least one of the sludge generated in the post-treatment after the treatment to the aggregating means or one or more return places upstream thereof, wherein the returning means is the organic Wastewater oil And density, according to at least one of the density of the SS concentration of the organic waste water, characterized in that said sending back the sludge to the front stage of the apparatus of the aggregation means or the agglomeration means.

The invention as described above has the following effects (i) to (iii), for example.
(I) Less work load than conventional technology. That is, in general pressure flotation treatment, there are many necessary operation management items such as adjustment of injection rate of inorganic flocculant and organic polymer flocculant, adjustment of dissolved air amount, adjustment of pressurized water amount, adjustment of scraping speed, etc. The operation management was complicated. On the other hand, in the above invention, the adjustment of the operation speed of the solid-liquid means (device) used for mechanical solid-liquid separation is only a main item of operation management.

(Ii) Since the above invention uses a cationic organic polymer flocculant (oil separation polymer) as the main flocculant, conventional flocculants (particularly inorganic flocculants such as aluminum flocculants and iron flocculants) Even when used, only a small amount is required, and there is an advantage that the removal rate of phosphorus is low and the consumption of alkalinity is low.

That is, when an aluminum-based flocculant is used as an inorganic flocculant in the prior art, the reaction formula of the flocculant is represented by the following formula: Al ₂ (SO ₄ ) ₃ + 6HCO ₃ ⁻ = 2Al (OH) ₃ + 6CO ₂ + 3SO ₄ ^{2 −}
Through the following formula 2Al (OH) ₃ / Al ₂ (SO4) ₃ = 0.23
As a result, 0.23 mg / L of sludge is generated as flocculant-derived sludge per 1 mg / L of aluminum sulfate (the water treatment chemical handbook, Gihodo Publishing).

In the above process, phosphoric acid (PO ₄ ³⁻ ) becomes Al ³⁺ + PO ₄ ³⁻ = AlPO ₄ to form a poorly water-soluble phosphate, so that phosphorus is simultaneously removed. Also, when iron-based flocculants are used, phosphorus is removed by iron ions. Therefore, removal of phosphorus becomes a problem when using inorganic flocculants regardless of whether aluminum or iron-based.

Furthermore, consumption of alkalinity has also become a problem when using inorganic flocculants. For example, the aluminum-based coagulant, when using aluminum sulfate _{(Al 2 (SO 4) 3} · 18H 2 O), with respect to aluminum sulfate 1 mg / L, to consume alkalinity 0.45 mg / L, as caustic soda An injection of 0.36 mg / L was required.

(Iii) Since a strong floc is formed by the action of the cationic organic polymer flocculant, the mechanical solid-liquid separator can be dehydrated at a low water content, and the flocculant (particularly inorganic flocculant) Since no sludge derived from it is generated, the amount of discharged sludge is small.

  According to the present invention, the work load is small, the moisture content of the dewatered sludge can be reduced, and the sludge discharge amount can also be reduced.

It is a flow sheet of the coagulation pressure levitation processing of the prior art. It is a flow sheet which shows the present invention typically. It is drawing which shows the water treatment method of a 1st example, and the processing apparatus used for it. It is drawing which shows the water treatment method of a 2nd example, and the processing apparatus used for it. It is drawing which shows the water treatment method of a 3rd example, and the processing apparatus used for it. It is drawing which shows the water treatment method of a 4th example, and the processing apparatus used for it. It is a typical sectional view showing the solid-liquid separation device of the 1st example. It is a typical sectional view showing the solid-liquid separation device of the 2nd example.

  Hereinafter, the present invention will be specifically described, but the present invention is not limited to a specific example.

  FIG. 2 is a flow sheet schematically showing the present invention. In the water treatment method and treatment apparatus of the present invention, a cationic organic polymer flocculant is added to the water to be treated, and after coagulation treatment, The treated water after solid-liquid separation is biologically treated. If necessary, the treated water after biological treatment can be subjected to post-treatment. As a specific example of this post-treatment, a solid-liquid separation step using an apparatus different from the mechanical solid-liquid separation in the previous stage is possible. There is.

  In the water treatment method and the treatment apparatus of the present invention, either one or both of sludge generated by biological treatment (excess sludge) and sludge generated by post-treatment are returned, and the returned sludge is treated. Follow the same process steps as for water. More specific description will be given below.

<Treatment water (organic wastewater)>
In the present invention, the water to be treated is organic wastewater containing oil and organic matter, and wastewater generated at various factories such as food processing factories, food production factories, beverage production factories, machine factories, automobile factories, etc. And sewage, human waste, and discharge water from septic tanks. The treated water is not particularly limited, and examples thereof include waste water (kitchen waste water) discharged from various facilities such as shopping centers, restaurants, supermarkets, hotels, and hospitals.

  The oil component indicates not only oil that is liquid at room temperature, but also fat that is solid at room temperature, that is, fats and oils in general. Examples of the oil contained in the water to be treated include vegetable oil, animal oil, mineral oil, and the like, and these oils contain one or more kinds. In general, the concentration of oil in wastewater is measured as a hexane extract (JIS K0102).

  The organic substance is a concept that includes all of the oil and organic substances other than the oil. That is, the organic wastewater may contain only oil or may contain organics other than oil in addition to oil. Examples of organic substances include one or more organic substances such as carbohydrates, proteins, lipids, nucleic acids, vegetable oils, animal oils, mineral oils, alcohols, fatty acids, surfactants and paints. The organic matter may be a material derived from animals or plants or a chemically synthesized material. Moreover, the substance manufactured from the said substance or the decomposition product of the said substance may be sufficient. Furthermore, the water to be treated may contain an inorganic substance.

  Next, an example of the cationic organic polymer flocculant used in the present invention will be described.

<Cationic organic polymer flocculant (oil separation polymer)>
-Kind The cationic organic polymer flocculant is not particularly limited, but is a homopolymer or copolymer of a cationic monomer, a copolymer of a cationic monomer and a nonionic monomer, a copolymer of a cationic monomer and an anionic monomer. One or more types can be selected from polymers and used. In the present invention, an organic polymer flocculant is described in order to clearly distinguish it from inorganic flocculants such as polyaluminum chloride and polyferric sulfate, but it is generally simply referred to as a polymer flocculant.

  The cationic monomer can be selected from one or more of dialkylaminoalkyl (meth) acrylate or neutralized salt, tertiary salt or quaternary salt of dialkylaminoalkyl (meth) acrylate. For example, dimethylamino Examples thereof include neutralized salts, tertiary salts, and quaternary salts of ethyl (meth) acrylate or dimethylaminoethyl (meth) acrylate. Among these, a quaternary salt of dimethylaminoethyl (meth) acrylate is preferable, and an ammonium salt is more preferable.

  As the nonionic monomer, one or more kinds selected from (meth) acrylamide, N, N-dimethyl (meth) acrylamide, (meth) acrylonitrile, vinyl acetate and the like can be used. Examples of the anionic monomer include (meth) acrylic acid, sodium (meth) acrylate, itaconic acid, maleic acid, fumaric acid, 2- (meth) acrylamide-methylpropanesulfonic acid, and metal salts or ammonium salts thereof. One or more types can be selected and used.

  In addition, (meth) acrylate is a concept including both acrylate and methacrylate, (meth) acrylic acid is a concept including both acrylic acid and methacrylic acid, and (meth) acrylamide is both acrylamide and methacrylamide. It is a concept that includes

  As the cationic organic polymer flocculant, in addition to the non-amidine polymer flocculant, an amidine polymer flocculant having an amidine unit, an amidine polymer flocculant and a non-amidine polymer flocculant are mixed. Examples thereof include a polymer flocculant.

  Examples of the cationic organic polymer flocculant include powder and liquid (dispersion and emulsion).

-Cation Degree As described above, the type of raw material monomer and the mode of the flocculant are not limited, but the present invention has a cation degree of 50 mol% or more, that is, a cation in all monomer units of the polymer. It is preferable to use a cationic organic polymer flocculant containing at least 50 mol% of a cationic monomer unit, and a particularly preferable cationic degree is 60 mol% or more, and of these, 80 mol% or more is preferable.

  Furthermore, a cationic organic polymer flocculant composed of a substantially cationic monomer (100 mol%) can also be used. The cation degree can be defined as the ratio (mol%) of the cationic monomer contained in the raw material monomer of the flocculant.

  In general, the oil contained in the wastewater is finely dispersed in the wastewater by the surfactant and the alkali component, and the surface of the oil particles is negatively charged. Compared to the zeta potential of general pollutants, the zeta potential of oil particles is remarkably low. Even if a normal cationic organic polymer flocculant is added, flocs are not formed, or even if flocs are formed, they are mechanical. A strong floc that can withstand solid-liquid separation is not formed.

  On the other hand, when a cationic organic polymer flocculant having a cationic degree of 50 mol% or more is added and mixed, the cationic organic polymer flocculant has large positively charged (high positive charge density) molecular chains in the waste water. Capable of capturing dispersed oil and forming a strong floc that can withstand mechanical solid-liquid separation.

—Molecular Weight The molecular weight of the cationic organic polymer flocculant is not particularly limited, but the molecular weight is preferably 5 million or more, particularly 6 million or more, and more preferably 8 million or more. The molecular weight here is a value measured and calculated by the intrinsic viscosity method. For details of the measurement and calculation method, see pages 112 to 116 of "Guide for using polymer flocculant" (Tokyo Sewerage Service Co., Ltd., Heisei) Issued in March 2014).

  As described above, the oil in the waste water is finely dispersed. Therefore, even if a normal cationic organic polymer flocculant is added, floc formation is not formed, or even if floc is formed, mechanical solid-liquid separation is possible. A strong floc to withstand is not formed. On the other hand, when a cationic organic polymer flocculant having a molecular weight of 5 million or more is added and mixed, the long molecular chain of the cationic organic polymer flocculant captures finely dispersed oil in the waste water, and mechanical solid-liquid A strong floc that can withstand separation can be formed.

-Viscosity From the same viewpoint as the molecular weight, the characteristics of the cationic organic polymer flocculant can be defined by the solution viscosity. Specifically, the solution viscosity when the cationic organic polymer flocculant is dissolved in pure water at 2 g / L is preferably 200 mPa · s or more, particularly 220 mPa · s or more, and more preferably 250 mPa · s or more. It is preferable that

  In addition, when the cationic organic polymer flocculant is dissolved in pure water at 1 g / L, the viscosity of the aqueous solution is preferably 100 mPa · s or more, particularly 120 mPa · s or more, and more preferably 150 mPa · s or more. It is preferable.

In addition, the above-mentioned viscosity uses spindle SB2 described in Appendix 1 (reference) of B-type viscometer, JIS K7117-1: 1999 for both concentrations of 1 g / L and 2 g / L. , 25 ° C., 60 min ⁻¹ , measured at a rotational speed. The spindle is also called a rotor.

—Solvent The cationic organic polymer flocculant is preferably used as a flocculant solution dissolved or dispersed in a solvent. Examples of the solvent include pure water, tap water, industrial water, ground water, treated water for various wastewater treatment, seawater, and the like. From the viewpoint of maximizing the cohesive strength of the cationic organic polymer flocculant, it is preferable to use pure water or tap water. On the other hand, from the viewpoint of economy, it is preferable to use factory water, groundwater, or treated water for various wastewater treatment.

-Injection amount The injection amount of the cationic organic polymer flocculant is preferably 3 to 300 mg / L, more preferably 5 to 200 mg / L, and particularly preferably 10 to 150 mg / L. The injection amount is an amount with respect to 1 L of water to be treated 20, and indicates an amount with respect to 1 L of the mixed liquid 2 when the water to be treated 20 is mixed with the return sludge. The injection amount in the case of using the flocculant solution means the amount of the flocculant itself excluding the solvent.

The injection rate of the cationic organic polymer flocculant with respect to COD _{Cr in the} water to be treated 20 is preferably 0.2% to 10.0%, particularly 0.3% to 7.0%. It is preferably 0.3% to 2.0%. If the injection amount of the cationic organic polymer flocculant is too high, not only will the processing cost be increased, but there will be problems such as an increase in the viscosity of the floc, making it difficult to separate the solid and liquid, and the tendency of the floc to collapse.

[Other drugs]
Although the present invention can treat wastewater containing oil without using other chemicals such as inorganic flocculants, it does not limit the use of chemicals other than the cationic organic polymer flocculants. Specifically, in addition to the cationic organic polymer flocculant, one or more kinds of agents such as an inorganic flocculant, an organic polymer flocculant, and a dehydration aid can be added.

  As the inorganic flocculant, sulfuric acid band, polyaluminum chloride (PAC), aluminum chloride, polyferric sulfate (polyiron), ferric sulfate, ferric chloride or a mixture thereof can be used. Organic polymer coagulants include condensed polyamines, dicyandiamide / formalin condensates, polyethyleneimine, polyvinylimidazoline, polyvinylpyridine, diallylamine salts / sulfur dioxide copolymers, polydimethyldiallylammonium salts, polydimethyldiallylammonium salts / sulfur dioxides Examples thereof include a copolymer, a polydimethyldiallylammonium salt / acrylamide copolymer, a polydimethyldiallylammonium salt / diallylamine hydrochloride derivative copolymer, and an allylamine salt polymer.

  Specific examples of the condensed polyamine include a condensate of alkylene dichloride and alkylene polyamine, a condensate of aniline and formalin, a condensate of alkylene diamine and epichlorohydrin, a condensate of ammonia and epichlorohydrin, and the like. Examples of the alkylene diamine condensed with epichlorohydrin include dimethylamine, diethylamine, methylpropylamine, methylbutylamine, and dibutylamine.

  The dehydration aid is not particularly limited, but an oil removing agent that is dispersed in the water to be treated and contributes to oil removal is preferable. As the oil remover, one or more of a natural polymer oil remover and a synthetic polymer oil remover can be used, and the mode of the oil remover is not particularly limited, such as a powder or a short fiber shape. A substance having at least one of a hydrophilic part and a hydrophobic part therein, preferably a substance containing both a hydrophilic part and a hydrophobic part is used.

  The natural polymer oil remover is not particularly limited as long as it is a hydrophilic substance. The natural product is used as it is, an extract from the natural product, a refined product of the natural product, a processed product of the natural product (chemical modification, modification), A wide variety of natural products such as regenerated products can be used, but cellulose-based materials and protein-based materials are preferable, and cellulose-based materials are particularly preferable.

The synthetic polymer oil remover is not particularly limited as long as it is a lipophilic substance synthesized from a fossil raw material, and one or more polyolefins, vinyl polymers, aliphatic polyesters, or other resin materials can be used. Furthermore, it is also possible to use a powder obtained by pulverizing an oil-absorbing polymer that entangles an oil component at a molecular level into a network of entangled molecular chains or a three-dimensional crosslinked structure from 0.1 mm to about 5 mm.
Next, the processing apparatus of the present invention will be described.

<Processing device>
3 to 6 are drawings for explaining the water treatment methods of the first to fourth examples and the treatment apparatus used therefor, respectively, and the same members are denoted by the same reference numerals and description thereof is omitted. These processing apparatuses 1a to 1d have a coagulation means 15, a solid-liquid separation means (solid-liquid separation apparatus 6), and a biological treatment means (biological treatment tank 9), and for pretreatment as necessary. Other means and devices such as the above-mentioned device (pH adjusting means 13) and the post-treatment device (solid-liquid separation device 10) may be installed. Each means will be specifically described below.

-Aggregation means 15
The agglomeration means 15 has an agglomeration tank 3 and a supply means 14, and the supply means 14 contains a powder or solution of a cationic organic polymer flocculant, preferably an aqueous solution or an aqueous dispersion. The supply means 14 is connected to the agglomeration tank 3 or the preceding stage, preferably the agglomeration tank 3, and finally the cationic organic polymer flocculant is supplied into the agglomeration tank 3. The coagulation tank treated water 5 treated by the coagulation means 15 is sent to the solid-liquid separation means directly or via another treatment apparatus.

-Solid-liquid separation means (solid-liquid separation device 6)
The solid-liquid separation device 6 is not particularly limited, but a mechanical solid-liquid separation device is preferable from the viewpoint of dewatering efficiency, installation area, operation management, and the like, and agglomeration such as a pressure flotation device, rather than a gravity precipitation treatment facility. An apparatus for mechanically solid-liquid separation of flocs by pressurization, centrifugal force, reduced pressure (evacuation) or a combination thereof is more preferable than a floating separation apparatus.

  As the mechanical solid-liquid separator 6, it is possible to use one or a combination of two or more dehydrators and concentrators conventionally used for sludge dewatering and sludge concentration. , Screw press dehydrator, belt press dehydrator, centrifugal dehydrator, multiple disk type dehydrator, multiple plate type screw press dehydrator, rotary pressure dehydrator, vacuum dehydrator, elliptical plate dehydrator, etc., sludge Examples of the concentrator include a screw concentrator, a belt concentrator, a centrifugal concentrator, and an elliptical plate concentrator.

  Reference numerals 6a and 6b in FIGS. 7 and 8 are partial cross-sectional views showing the solid-liquid separators of the first and second examples, and these solid-liquid separators 6a and 6b are flock moving means for continuously processing flocks. 35. The flock moving unit 35 includes, for example, a belt driving unit 37 such as a rotating roll, and a belt 36 spanned over the belt driving unit 37. The coagulating tank treated water 5 is supplied onto the belt 36 through the flock inlet 33 and moves in a substantially horizontal direction together with the belt 36 by the rotation of the belt driving means 37.

  Part or all of the belt 36 is made of a filter cloth, and the treated water is solid-liquid separated into floc and moisture during the movement, and the separated treated water 7 is captured by the capturing means 34 below the belt 36, The separated flock (oil-containing sludge 8) is discharged from the discharge port 39. The belt 36 after discharging the oil-containing sludge 8 returns to the flock inlet 33 side, and the coagulation tank treated water 5 is supplied again. Before returning to the flock inlet 33 side, the cleaning water from the cleaning pipe 38 is sprayed. The belt 36 may be washed.

  Thus, the solid-liquid separation devices 6a and 6b are both suitable for continuous processing of the solid-liquid separation process, but more preferably, the pressurizing means 41 is installed like the solid-liquid separation device 6b of the second example. (FIG. 8). The pressurizing means 41 is a device that pressurizes (squeezes) the flock, and includes, for example, one or more pressurizing plates 42 disposed in front of the discharge port 39.

  The pressure plate 42 is inclined from the vertical surface to the flock inlet 33 side, and there is a gap between the lower end of the pressure plate 42 and the belt 36, and when passing through the gap, the flock is pressed against the belt 36 by the pressure plate 42. Pressurized (squeezed). The pressurization pressure at this time is adjusted by changing one or more pressurization conditions, with the size of the gap, the inclination angle and number of pressurization plates 42, the moving speed of the flock and the supply amount, etc. as pressurization conditions. be able to.

  Note that the pressurizing means 41 is not limited to the pressurizing plate 42, and a pressurizing member having another shape such as a pressurizing roll may be used. In either case, the moisture content of the floc can be efficiently reduced by the pressurizing means 41. The pressure applied to the floc can be appropriately changed depending on the apparatus and solid-liquid separation conditions, but is preferably 200 kPa or less, particularly preferably 1 kPa to 150 kPa, and more preferably 1 kPa to 100 kPa, more preferably 10 kPa or more, and further preferably 15 kPa or more. Especially preferably, it is 20 kPa or more. In the case of the solid-liquid separator 6b of the second example, the pressure can be adjusted by the pressurizing condition of the pressurizing plate 42. In the case of a screw press dehydrator, the screw rotation speed and the opening degree of the outlet are adjusted. The internal pressure can be adjusted.

  In the agglomeration means 15 and the solid-liquid separation devices 6a and 6b, the flock formation step and the solid-liquid separation step are performed separately, but a device that simultaneously performs the flock formation step and the solid-liquid separation step, such as a centrifugal dehydrator. It can also be adopted.

  The centrifugal dehydrator has, for example, a cylindrical casing, a hollow outer bowl that is inserted through the casing, and an inner cylinder screw that is inserted through the outer bowl, and the outer bowl and the inner cylinder screw are Rotating at different speeds in the same direction around the rotation axis, a rotation difference is generated.

  The water to be treated is supplied to the inner space of the inner cylinder screw, and the cationic organic polymer flocculant or its solution is mixed in the preceding stage, and the mixed solution is supplied from the supply port of the inner cylinder screw to the outer cylinder bowl and the inner cylinder screw. It is supplied to a gap (pool) between the barrel screw. The supplied mixed solution is subjected to strong centrifugal force while being stirred and mixed, and solid-liquid separation of the generated floc proceeds. Screw blades are attached to the outer surface of the inner barrel screw, and the oil-containing sludge generated by the solid-liquid separation is transferred by the rotating screw blades and finally discharged from the discharge port of the solid-liquid separator. On the other hand, the separated treated water is discharged from an outlet different from the oil-containing sludge due to the difference in water level from the sludge discharge side.

  Regardless of which solid-liquid separator is used, the treated water separated from the floc (mechanical solid-liquid separator treated water 7) is sent to the biological treatment means.

-Biological treatment means (biological treatment tank 9)
The biological treatment means is not limited as long as it uses living organisms (particularly microorganisms), and uses either one or both of anaerobic microorganisms and aerobic microorganisms to treat organic matter from the treated water 7 of the mechanical solid-liquid separation device, Remove residual substances such as oil and inorganic substances (nitrogen, phosphorus, metal).

  The biological treatment means is usually composed of a biological treatment tank 9 containing the above microorganisms. In the present invention, most of the oil content in the organic waste water is removed in advance by the agglomeration means 15 and the solid-liquid separation devices 6a and 6b in the previous stage, so there is no limitation on the system and use conditions of the biological treatment tank 9. For example, in addition to the normal activated sludge method, an activated sludge method using membrane separation (MBR method), a biofilm method using a carrier to which microorganisms adhere (fixed) may be used, or a carrier that floats a carrier to which microorganisms have adhered. An addition method may be used, or a plurality of methods may be combined.

  Among these, the MBR method in which a membrane separation processing apparatus is installed inside the biological treatment tank 9 and the treated water is solid-liquid separated in the biological treatment tank 9 is obtained by solid-liquid separation of excess sludge from the treated water 7, and suspended matter. In addition to being able to reduce the outflow of the sludge, the management of sludge return described later is also simplified, which is particularly suitable for the present invention.

  The number of installed biological treatment tanks 9 is not particularly limited. For example, the mechanical solid-liquid separation treated water 7 can be passed through a plurality of biological treatment tanks 9 in order and treated in multiple stages. Furthermore, the type of the biological treatment tank 9 that allows water to flow according to the quality of the mechanical solid-liquid separation treated water 7 and raw water (treated water 20) is selected, and the connection between the solid-liquid separation means and the biological treatment tank 9 is switched. May be.

  In either case, the treated water from which residual substances have been removed by biological treatment is discharged to the outside of the treatment apparatuses 1c and 1d (FIGS. 5 and 6) or supplied to a post-treatment apparatus (FIG. 3, 4). Although this post-processing is not specifically limited, Preferably, the solid-liquid separation means different from the apparatus 6 used for isolation | separation of the oil-containing sludge 8 is used.

-Solid-liquid separation means (solid-liquid separation device 10)
A solid-liquid separation device 10 different from the solid-liquid separation device 6 in the previous stage is used as the solid-liquid separation means for post-processing. The type of the solid-liquid separation device 10 is not particularly limited, and it is possible to use the same type of device as the solid-liquid separation device 6 in the previous stage, but more preferably, gravity precipitation treatment equipment, coagulation precipitation treatment equipment, Although it is a membrane separation processing facility or a combination thereof, more preferably a membrane separation processing facility.

  In the solid-liquid separation device 10, substances remaining after the biological treatment are removed, and the treated water is discharged to the outside of the treatment devices 1a and 1b. On the other hand, separation sludge is generated in the solid-liquid separator 10, and surplus sludge is also generated in the biological treatment tank 9 in the preceding stage. The code | symbol 11 of FIGS. 3-6 has shown the solid-liquid separation apparatus 10 and the separation sludge 11 obtained from the biological treatment tank 9. FIG.

  It is also possible to install a sludge dehydrator 12 for dehydrating any one or more of these separated sludge 11 and the oil-containing sludge 8 of the solid-liquid separator 6 (FIGS. 3 and 5). As the machine 12, an apparatus similar to the solid-liquid separation apparatus 6 in the previous stage can be used. However, whether or not the sludge dewatering machine 12 is installed, the processing apparatuses 1a to 1d of the present invention have the return means 17 for returning the separated sludge 11.

-Return means 17
Although the return means 17 is not specifically limited, For example, it is comprised by one or more members, such as piping, a pump, a flow control apparatus (flow meter, flow controller), a valve, a control apparatus, or these combination.

  The return means 17 is connected as a return source to apparatuses 9 and 10 on the downstream side of the solid-liquid separation apparatus 6 in the previous stage, and is connected as a return destination to the aggregation means 15 or an apparatus on the upstream side. Preferably, the return source is one or both of the biological treatment tank 9 and the subsequent solid-liquid separation device 10, and the return destination is a device or piping on the upstream side of the aggregating means 15, and more preferably as the return destination. A mixing tank is installed upstream of the aggregation tank 3. In the processing method of the present invention, the return means 17 is used to return part or all of the separated sludge 11.

  Next, the processing method of the present invention will be specifically described.

<Water treatment method>
The water treatment method of the present invention uses the organic wastewater described above as the treated water 20 when any of the treatment apparatuses 1a to 1d is used. Pre-treatment includes pH adjusters (acid / alkali etc.), inorganic flocculants, flocculants other than the above cationic organic polymer flocculants (especially organic flocculants having a lower molecular weight than cationic organic polymer flocculants), dehydration It is also possible to select one or more types from auxiliary materials and the like and add them to the water to be treated 20.

  However, considering the impact on biological treatment due to the removal of nutrients (phosphorus) and the increase in sludge amount, the amount of inorganic flocculant used should be less than the general amount used (eg 1000 mg / L) The inorganic flocculant 10 containing at least one of an aluminum flocculant and an iron flocculant is less than 500 mg, preferably less than 100 mg, more preferably less than 50 mg, and particularly preferably 10 mg with respect to 1 L of water to be treated 20. It is also possible to add less, and to add substantially no inorganic flocculant.

  The agglomeration means 15 is supplied with at least one of the treated water 20 pretreated as necessary and the separated sludge 11 returned by the return means 17, more preferably both.

  The entire amount of the separated sludge 11 may be returned (FIGS. 4 and 6), or only the necessary amount may be returned and the remaining part may be processed by another device (sludge dehydrator 12) (FIGS. 3 and 5). More specifically, the separated sludge 11 is returned according to the water quality (oil concentration, SS concentration) of the water to be treated 20 before pretreatment and the supply amount of the water to be treated 20.

Specifically, the return amount is determined so that the sludge concentration (SS concentration) of the separated sludge 11 with respect to the supply amount of the treated water 20 is 100 to 200 mg / L. For example, when the supply amount of the treated water 20 is 100 m ³ / day and the sludge concentration of the separated sludge 11 is 5,000 mg / L, the return amount of the separated sludge 11 is 2 m ^{3 to} 4 m per day as shown in the following formula I: ³ or less.

100 [m ³ / day] × (100 to 200) [mg / L] / 5000 [mg / L] = 2 to 4 [m ³ /day]...Formula I

  However, the return amount may be increased beyond the above range. For example, a preliminary test can be performed and determined by the following test procedure.

1 L of water to be treated 20 (before pretreatment) is collected in a container, a cationic organic polymer flocculant is added at a predetermined injection rate (for example, a set value of the supply means 14), and a stirrer (rotation speed 50 min ^{− 1} , the water to be treated and the cationic organic polymer flocculant are mixed in a stirring time of 10 minutes to form a floc. The rotation speed and stirring time of the stirrer can be changed in accordance with the rotation speed in the aggregating means 15 and the stirring time (residence time).

  Next, using a sieve (aperture 1 mm) and a pressure plate (pressure 50 kPa), water to be treated including floc is solid-liquid separated into sludge and a separated liquid, and the strength of the floc is confirmed. At this time, when turbidity or the like is confirmed in the separated liquid, it is considered that the cohesiveness with respect to at least one of the oil concentration of the treated water 20 and the SS concentration of the treated water 20 is insufficient, and the return amount of the separated sludge 11 is returned. And at least one of the injection amount of the drug (cationic organic polymer flocculant, etc.) is increased. This test procedure is not necessarily essential, and the required return amount can be estimated from the results of past tests, the oil concentration and SS concentration of the treated water 20, the operating conditions of the discharge source factory, and the like.

  The returned separated sludge 11 may be supplied to the aggregating means 15 separately from the treated water 20 and processed, but preferably, the treated water 20 and the separated sludge 11 are disposed upstream of the aggregating means 15. The mixed liquid 2 is supplied to the aggregation means 15.

  Most preferably, a mixing tank is installed on the upstream side of the coagulation tank 3, and a pH adjusting agent is added from the pH adjusting means 13 in this mixing tank to adjust the pH, and the treated water 20 and the separated sludge 11 are further added. The mixed liquid 2 is formed by mixing, and the mixed liquid 2 after pH adjustment is processed by the aggregating means 15. The pH of the mixed solution 2 is set to a pH suitable for aggregation (e.g., pH 3 to 11), and more preferably to a pH suitable for subsequent biological treatment (e.g., pH 5 to 8).

  The aggregating tank 3 is provided with a stirring means, and when the cationic organic polymer flocculant is added from the supply means 14 to the mixed liquid 2 containing the separated sludge 11 and the treated water 20 and stirred, The oil and organic matter in 20 are aggregated to form aggregated flocs.

  Since the separated sludge 11 is generated in the devices 9 and 10 downstream from the aggregating means 15, the cationic organic polymer flocculant is already attached, and the cationic organic polymer agglomeration is performed according to the return amount of the separated sludge 11. The drug will also be returned. That is, in addition to the cationic organic polymer flocculant from the supply means 14, the mixed liquid 2 is also supplied with the cationic organic polymer flocculant derived from the separated sludge 11.

  In addition, the flocs contained in the separated sludge 11 become the core and the flocs grow, so that the flocculence can be achieved without increasing the amount of new cationic organic polymer flocculant and other flocculants (inorganic flocculants). The floc grows and becomes a strong floc. Therefore, even if the coagulation tank treatment water 5 is mechanically solid-liquid separated by the solid-liquid separation device 6, the floc is not easily damaged, and the concentration / dehydration treatment can be performed efficiently.

  By this concentration / dehydration treatment, most of the oil and SS derived from the treated water 20 are removed from the treated water 7 as the oil-containing sludge 8. The oil-containing sludge 8 may be mixed with the dehydrated sludge of the dehydrator 12 and discarded, or may be reused alone as a combustion aid. Furthermore, the oil-containing sludge 8 may be discarded alone or together with the separated sludge 11 after being dehydrated by the dehydrator 12.

  On the other hand, the mechanical solid-liquid separation device treated water 7 may be discharged from the processing devices 1a to 1d as it is depending on the required water quality on the discharge side, but preferably biologically treated aerobically or anaerobically in the biological treatment tank 9. To do.

  Since the oil and SS are removed in advance from this treated water 7 as oil-containing sludge 8, the BOD load is low, the residence time in the biological treatment tank 9 can be shortened, the excess sludge can be reduced, etc. Inactivation of microorganisms due to oil is also prevented. Moreover, since the present invention can suppress the use of the inorganic flocculant, phosphorus necessary for the growth of many microorganisms remains in the treated water 7, and the management of the biological treatment tank 9 is also simplified.

  The surplus sludge generated in the biological treatment tank 9 is partly or entirely returned as a separated sludge 11 after solid-liquid separation by the membrane device of the biological treatment tank 9 or as it is. The treated water from which the organic matter has been removed in the biological treatment tank 9 is discharged as it is according to the water quality, and is solid-liquid separated by the subsequent solid-liquid separation device 10 as necessary, and then discharged to the outside. Some or all of the sludge separated by the solid-liquid separator 10 is also returned as the separated sludge 11.

  As described above, the present invention returns the separated sludge 11 generated after the oil is removed as the oil-containing sludge 8, so that substances that adversely affect biological treatment such as oil and membrane filtration are not returned and are necessary for agglomeration. Only substances (floc nuclei, cationic organic polymer flocculants) can be mainly returned and reused.

  Hereinafter, the present invention will be described more specifically with reference to examples.

<Test Example 1>
The treatment test of the organic wastewater containing oil was carried out using the treatment apparatus 1d (FIG. 6) of the fourth example. In this treatment test, first, the water to be treated 20 is adjusted to an optimum coagulation pH with acid and alkali (pH = 7.1), and surplus sludge (separated sludge 11) from the biological treatment tank 9 is returned to 400 mg / L. The mixture was returned in an amount to obtain a mixed solution 2. This mixed liquid 2 was introduced into the coagulation tank 3, and 70 mg of a cationic organic polymer coagulant (oil separation polymer) was added from the supply means 14 per liter of water to be treated and stirred.

  The coagulation tank treated water 5 was mechanically concentrated and dehydrated by the solid-liquid separation device 6 b shown in FIG. 8 and separated into treated water 7 and oil-containing sludge 8.

  Separately from this, as a comparative example, an inorganic flocculant (sulfuric acid band) and caustic soda were injected, and after further adding a polymer flocculant, flocs were removed by the conventional pressure flotation method. The test conditions are summarized in Table 1 below along with the pH of the water to be treated (after pH adjustment), SS concentration, oil content (hexane-extracted substance), BOD, COD, and phosphorus concentration.

In the above table, “oil separation polymer” is a cationic organic polymer flocculant (cation degree 85 mol%, molecular weight 9 million) made of a copolymer of dimethylaminoethyl acrylate quaternary ammonium salt and acrylamide. “Polymer” is an anionic organic polymer flocculant (trade name “Ebagulose A-151” from Mizu Inc.). In the prior art, in order to compensate for the decrease in pH due to the addition of the sulfuric acid band, which is an inorganic flocculant, the addition of NaOH is essential, and the processing cost is increased as compared with the present invention. The P0 4 _-P concentration is approximately 0 mg / L next residual processing water in the prior art, in the prior art, it was confirmed that it is necessary to implantation of phosphorus as nutrients to the biological treatment.

<Test Example 2>
Using the treatment apparatus 1b (FIG. 4) of the second example, a treatment test of the oil-containing organic waste water was performed. In this treatment test, first, the water 20 to be treated is adjusted to an optimum coagulation pH with acid and alkali (pH = 7.1), and a part of the separated sludge 11 (100 mg / L, mg / L was returned as the amount per 1 L of water to be treated (hereinafter the same), and the mixture 2 was obtained.

  This mixed liquid 2 is introduced into the agglomeration tank 3, and 12 mg / L of a cationic organic polymer flocculant (the same oil separation polymer as in Test Example 1) and 100 mg / L of a dehydration auxiliary material (cellulose) are supplied from the supply means 14. The coagulation tank treated water 5 in which flocs were formed was added and stirred, and concentrated and dehydrated with a mechanical solid-liquid separator 6, and separated into treated water 7 and oil-containing sludge 8.

  The oil-containing sludge 8 was discarded and the treated water was treated in the biological treatment tank 9, and then the treated water was treated with a solid-liquid separation device 10 (gravity precipitation treatment) at the subsequent stage. With respect to the treated water treated by the solid-liquid separator 10, the hexane extract material was measured. The measurement results are shown in Table 2 below together with the test conditions.

  As apparent from Table 2 above, according to the present invention, it was confirmed that the residual amount of treated water of the hexane extract was extremely low and the oil was sufficiently removed.

  Moreover, when the excess separated sludge 11 was mixed with the oil-containing sludge 8 and dehydrated by the sludge dewatering machine, the sludge treatment could be unified and the oil-containing sludge moisture content after the dehydration was 80.4%. . On the other hand, the water content of the dewatered sludge according to the prior art is about 85%, confirming the superiority of the present invention.

DESCRIPTION OF SYMBOLS 1a-1d: Processing apparatus, 2: Mixed liquid, 3: Coagulation tank, 5: Coagulation tank processing water, 6, 6a, 6b: Solid-liquid separation apparatus, 7: Mechanical solid-liquid separation apparatus processing water, 8: Oil-containing sludge , 9: biological treatment tank, 10: solid-liquid separator, 11: separated sludge, 12: sludge dehydrator, 13: pH adjusting means, 14: supply means, 15: coagulation means, 17: return means, 20: treated Water: 33: Flock inlet, 34: Trapping means, 35: Flock moving means, 36: Belt, 37: Belt driving means, 38: Washing pipe, 39: Discharge port, 41: Pressurizing means, 42: Pressurizing plate

Claims (5)

A coagulation treatment step of adding a cationic organic polymer flocculant to an organic wastewater containing oil and organic matter to form treated water containing coagulation flocs of oil and organic matter;
A mechanical solid-liquid separation step for mechanically solid-liquid separating the treated water containing the aggregated floc into the aggregated floc and a separation liquid;
A biological treatment step of biologically treating the mechanically separated solid-liquid separated liquid,
The separated sludge generated in one or both of the biological treatment step and the post-treatment after the biological treatment step is returned to the aggregation treatment step and at least one of the steps preceding the aggregation treatment step. A method for treating organic wastewater, comprising treating the organic wastewater.   The water treatment method for organic waste water according to claim 1, wherein in the post-treatment, the treated water from which organic substances have been removed in the biological treatment step is further subjected to solid-liquid separation to obtain the separated sludge.   The oil-containing sludge generated in the mechanical solid-liquid separation step and one or both of the separated sludge are dehydrated to obtain a dehydrated sludge. Water treatment method.   The water treatment method for organic wastewater according to any one of claims 1 to 3, wherein the separated sludge is returned according to at least one of an oil concentration and an SS concentration of the organic wastewater. . PH adjusting means for adjusting pH of organic wastewater containing oil and organic matter;
agglomeration means for mixing the organic wastewater adjusted to pH with a cationic organic polymer flocculant to agglomerate oil and organic matter to obtain treated water containing agglomerated floc;
Solid-liquid separation means for solid-liquid separating the treated water containing the aggregated floc into the aggregated floc and a separation liquid;
A biological treatment means for removing organic substances in the separated liquid and separating it into sludge and treated water;
Return at least one of the sludge generated in the biological treatment and the sludge generated in the post-treatment after the biological treatment to the aggregation means and one or more return places upstream from the aggregation means. And return means to
The return means returns the sludge to the agglomeration means or a device upstream of the agglomeration means according to at least one of the oil concentration of the organic waste water and the SS concentration of the organic waste water. An organic wastewater treatment apparatus containing oil.

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