JP2005334736A - Desalting method for salts-containing treated water and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a desalting method for high concentration salts-containing organic waste water, and an apparatus therefor. <P>SOLUTION: Salts-containing treated water obtained by treating the high concentration salts-containing organic waste water by the combination of biological treatment, coagulation treatment, and solid-liquid separation membrane treatment is subjected to multistage concentration using a plurality of evaporators to deposit and separate salts. Organic matter in the salts-containing treated water is removed by activated carbon absorption treatment or/and ozone oxidation treatment beforehand, and then fed to a first stage evaporator. A calcium salt, and the like, contained in the salts-containing treated water are removed beforehand as carbonates before or after the first stage evaporator. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention can be applied to biological treatment, coagulation treatment, solid-liquid separation membrane treatment (for example, microfiltration membrane treatment or ultrafiltration membrane treatment) for organic wastewater containing a high concentration of salts such as human waste and landfill leachate. ) And the like, and a salt-removing method and apparatus for recovering the salt as a crystal salt that can be used as an industrial salt or the like from a salt-containing treated water obtained by a combination treatment.

  Examples of methods for treating organic wastewater such as human waste and landfill leachate include biological treatment for the purpose of removing BOD (biological oxygen demand) components, COD (chemical oxygen demand) components, and chromaticity. There are agglomeration treatment and solid-liquid separation membrane treatment for the purpose of removing components and SS (suspended material), and the treatment methods are generally combined.

  However, organic wastewater, such as human waste and landfill leachate, will be discharged when treated with low dilution, even if contaminants such as organic matter are treated, the treated water contains high-concentration salts. In some cases, the protection of river water quality or the impact on agricultural water should be considered. Therefore, recently, there is an increasing need for removing not only organic pollutant components but also salts.

  As a method for removing salts from human waste water, a method using a solid-liquid separation membrane and a reverse osmosis membrane has been proposed (see, for example, Patent Document 1). However, this method is not a fundamental solution because it obtains treated water that does not contain salts, but discharges concentrated liquids containing salts at high concentrations.

Also, in the method of removing salts from treated water containing high-concentration salts such as landfill leachate using reverse osmosis membrane or electrodialysis membrane, before desalting by reverse osmosis membrane treatment or electrodialysis membrane treatment Alternatively, a method has been proposed in which heavy metals are removed using a chelate resin after desalting, and the concentrated solution of membrane separation is evaporated and dried to recover the salt as a solid (see, for example, Patent Document 2).
In this method, an expensive reverse osmosis membrane device or electrodialysis membrane device is required, and a heavy metal processing device is required. In addition, the chelate resin needs to be regenerated and is complicated to handle. Further, since the entire amount of water in the concentrated solution is evaporated, the obtained solid matter is a mixture of various things other than heavy metals.

  In addition, flocculant is added to human waste sewage, solid-liquid separation such as precipitation separation is performed, and sludge and separation liquid are separated. A method has been proposed in which treated water not containing salts is obtained, and the residual concentrated liquid of the evaporation treatment is incinerated in an incinerator together with dehydrated sludge and disposed as ash (see, for example, Patent Document 3). Even in this method, only a solid substance containing various miscellaneous materials as described above can be obtained.

JP-A-9-174051 JP 2001-70989 A JP-A-63-123500

The present invention has been made in view of the above circumstances, and its purpose is to treat organic wastewater containing high-concentration salts without using expensive reverse osmosis membranes or electrodialysis membranes. It is to provide a method and an apparatus for desalinating from water.

  The present invention has been made to achieve the above-described problems, and has been solved by the following means. A method for desalinating treated water containing high-concentration salts, containing salts obtained by combining organic wastewater containing high-concentration salts with biological treatment, coagulation treatment, solid-liquid separation membrane treatment, etc. The treated water was concentrated in a plurality of stages using a plurality of evaporators to precipitate the salts and separate them.

  The organic matter in the salt-containing treated water is removed in advance by activated carbon adsorption treatment or / and ozone oxidation treatment, and then supplied to the first stage evaporator, and the calcium salt contained in the salt-containing treated water, It is also characterized in that it is removed as carbonate in advance before or after the first stage evaporator.

  Desalination equipment for treated water containing high-concentration salts, containing salts obtained by combining organic wastewater containing high-concentration salts with biological treatment, coagulation treatment, solid-liquid separation membrane treatment, etc. The treated water was provided with a plurality of evaporators for sequentially concentrating and a centrifuge for separating the precipitated salts.

  An activated carbon adsorbing device or / and an ozone oxidation device for removing organic substances contained in the salt-containing treated water are provided in a previous stage of the first-stage evaporator to which the salt-containing treated water is supplied, the salt-containing treatment It is also characterized in that a softening device for removing calcium salt and the like contained in water as carbonate is provided in the front stage or the rear stage of the first stage evaporator.

According to the present invention, treated water obtained by treating organic wastewater containing high-concentration salts such as human waste and landfill leachate in combination with biological treatment, coagulation treatment, solid-liquid separation membrane treatment, etc. Since the plurality of evaporators are used for sequential concentration, scaling of the evaporators is suppressed, and maintenance work such as scale removal can be reduced.
Further, the condensed water recovered by cooling the steam generated in the evaporator can be reused because it is treated water that does not contain salts.

Further, by subjecting treated water containing high-concentration salts to activated carbon treatment and / or ozone oxidation treatment in advance, foaming due to organic matter in the evaporator can be prevented, and a crystalline salt with less coloring can be obtained.
Furthermore, by providing a softening device that removes calcium or the like at the front stage or the rear stage of the first stage evaporator, scaling of the evaporator can be prevented and the operation of the apparatus can be stabilized.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications.
FIG. 1 is a schematic diagram illustrating a configuration example of an embodiment of the present invention, and FIG. 2 is a schematic diagram illustrating a configuration example of another embodiment of the present invention. In FIG. 1 and FIG. 2, the same elements are denoted by the same reference numerals, and redundant description is omitted.

In FIG. 1, 1 is a separator such as a drum screen for separating impurities contained in human waste and septic tank sludge, 2 is removal of organic matter such as BOD, and ammonia nitrogen and nitric acid / nitrite nitrogen are converted to nitrogen gas. This is the primary nitrification denitrification tank. Reference numeral 3 denotes a secondary nitrification denitrification tank for removing remaining nitrogen. 4 is a first stage membrane separator for separating sludge and treated water, 5 is a coagulation tank for coagulating COD components and colored components, and 6 is for solid-liquid separation of solids such as aggregates and treated water. It is a second stage membrane separator.
7 is a tank of treated water containing high-concentration salts, and is a desalting raw water tank that needs to be desalted.

  8, 9, and 10 are the first-stage evaporator, second-stage evaporator and third-stage evaporator (hereinafter, first-stage evaporator, second-stage evaporator) for sequentially concentrating the desalted raw water. A stage evaporator, a third stage evaporator, or simply an evaporator). Usually, most of the salt precipitates in the final stage evaporator (the third stage evaporator in the example of FIG. 1), so this evaporator is often referred to as a crystallization can. .

A steam boiler 11 supplies steam used as a heating source of the evaporator, and 12 is a centrifuge for separating salts that are crystallized and precipitated by the evaporator.
Reference numerals 14, 15 and 16 denote water-cooled condensers for condensing vapor vaporized in the evaporators 8, 9 and 10. 17 is an activated carbon treatment apparatus for treating the condensed water of the condenser, and 18 is a contact tank for disinfecting the treated water.

Human waste sewage such as human waste and septic tank sludge is supplied to the separator 1 via the liquid feeding pipe L1, and contaminants which are large solids are removed by the screen of the separator 1.
Next, organic substances such as BOD components are removed and denitrified by the biological treatment apparatus A composed of the primary nitrification denitrification tank 2, the secondary nitrification denitrification tank 3, and the first stage membrane separation apparatus 4. Methanol or the like is added to the secondary nitrification denitrification tank 3 as a nutrient source if necessary (not shown).
The permeated liquid of the biological membrane separation device 4 that is biologically treated water is supplied to the coagulation tank 5 through the liquid feeding pipe L2.

  To the aggregating tank 5, an inorganic aggregating agent such as polyiron sulfate, iron chloride, aluminum sulfate or polyaluminum chloride and a pH adjusting agent such as sodium hydroxide are added to agglomerate COD components, phosphorus, coloring components and the like. The treatment liquid in the flocculation tank 5 is supplied to the flocculation membrane separation device 6 via the liquid feed pipe L3, and solids such as flocculates are separated and removed. The permeate of the second-stage membrane separation device 6 is usually discharged as treated water after being subjected to activated carbon adsorption treatment and disinfection treatment, but since it contains high-concentration salts, it is stored in the desalting raw water tank 7. Is done.

  As the separation membrane used in the biomembrane separation device 4 and the agglomeration membrane separation device 6, since solid-liquid separation is mainly used, a microfiltration membrane or an ultrafiltration membrane is usually used. As the membrane filtration method, various methods such as a method of immersing a fixed membrane or a rotatable membrane (for example, a rotating flat membrane) in water to be treated are used. Moreover, as a shape of the membrane to be used, a flat membrane, a tubular membrane, a hollow fiber membrane or the like is used.

The demineralized raw water containing high-concentration salt is supplied from the demineralized raw water tank 7 via the liquid feed pipe L4 to the first stage evaporator 8 to which water vapor is supplied from the steam boiler 11, and then to the second stage evaporator 9. Further, it is sequentially sent to the third stage evaporator 10.
The demineralized raw water is concentrated about 10 times in the first stage evaporator 8, and the concentrated solution is adjusted to pH by adding an acid or the like as necessary in order to prevent precipitation of calcium salt and the like. It is concentrated about 4 times in the stage evaporator 9. That is, the second-stage evaporator 9 is concentrated about 40 times with respect to the demineralized raw water.

The concentrated liquid concentrated in the second stage evaporator 9 is supplied to the third stage evaporator 10, where it is further concentrated by about 5 times and about 200 times with respect to the desalted raw water and dissolved. Crystallization of the salts takes place.
The third-stage evaporator 10 is discharged in a high-concentration slurry containing crystallized salts and is supplied to the centrifuge 12 via the slurry pipe L5. Salts (such as NaCl and Na ₂ SO ₄ ) crystallized by the centrifuge 12 are separated from the concentrate and recovered as industrial salts and the like.

  The mother liquor from which the crystal salt has been separated by the centrifuge 12 is stored in the mother liquor tank 13, returned to the third stage evaporator 10 through the liquid feed pipe L 6, and concentrated again to recover the crystal salt. . A part of the mother liquor is discharged out of the system through the drain pipe L7 in order to prevent accumulation of substances not suitable for crystallization.

  On the other hand, the vapors of the evaporators 8, 9, and 10 are cooled by condensers 14, 15, and 16, respectively, and the condensed water is supplied to the activated carbon treatment device 17 and processed. Since the treated water of the activated carbon treatment apparatus 17 does not contain salt or organic matter, a part is used as process water or middle water, and the rest is sterilized with a disinfectant such as sodium hypochlorite in the contact tank 18. After being released.

The salt-containing treated water in the first stage evaporator 8 and the second stage evaporator 9 is heated by, for example, heat exchange using a heat transfer tube installed in the evaporator using steam as a heat source. The heating inside the eye evaporator 10 is also performed by heat exchange using a shell-and-tube heat exchanger using steam as a heat source. It is also possible to use an electric heater as a heat source.
Various types of evaporators 8, 9, and 10 can be used in appropriate combination.
Further, the evaporation operation may be either a batch type or a continuous type, and an evaporation method using a multiple effect method using a plurality of evaporators or a multistage flash method can be employed.

In addition, although the case where three evaporators were used was demonstrated in embodiment of FIG. 1, you may add an evaporator and make it 4 steps | paragraphs or more.
By the method of the present invention in which evaporators are provided in multiple stages, the concentration factor of the target scale substance is adjusted by individually setting the concentration ratio of each stage, and the pH in the evaporator with high concentration that is likely to cause scales. Because adjustments can be made, scaling can be effectively generated in evaporators and other in-system piping, even in wastewater and other wastewater such as waste landfill leachate, even in treated water containing high concentrations of salts. It is possible to suppress.

For example, the first-stage evaporator 8 responsible for about 90% of the processing amount is about 10 times concentrated with respect to the demineralized raw water, so there is almost no crystallization of the salt. Is possible.
On the other hand, since the second stage evaporator 9 is concentrated about 40 times with respect to the demineralized raw water, the concentration of the salts forming the scale becomes saturated or supersaturated, so scaling may occur. Not suitable for continuous operation. However, it is possible to suppress the scaling by adjusting the pH to increase the solubility of target salts such as calcium salts.

  Further, even if scaling occurs in the second stage evaporator 9, it is only necessary to remove the scaling of only the small second stage evaporator 9, and it is possible to save chemicals used and shorten the work. .

Next, another embodiment of the present invention shown in FIG. 2 will be described.
In FIG. 2, 19 is an activated carbon treatment apparatus, B is a softening apparatus comprising a reaction tank 20 for converting calcium salt or the like into an insoluble carbonate, and a solid-liquid separation tank 21 for separating a product by precipitation separation or the like.
The embodiment shown in FIG. 2 is the same as the embodiment shown in FIG. 1 except that the activated carbon treatment device 19, which is a process for pretreating the salt-containing treated water to be treated, is placed in the front stage of the first stage evaporator 8. The softening device B is provided after the first stage evaporator.

  That is, in the embodiment of FIG. 1, the salt-containing treated water to be treated is supplied directly to the first stage evaporator 8 via the liquid feeding pipe L4. However, in the embodiment of FIG. Organic substances and coloring components in the treated water are previously removed through the activated carbon treatment device 19 and then supplied to the first stage evaporator 8 via the liquid feeding pipe L8.

  Further, in order to convert soluble calcium salt or magnesium salt into insoluble carbonate in the subsequent stage of the first stage evaporator 8, hot water containing sodium carbonate or carbonate ions, etc., and a neutralizing agent (alkaline or A softening device B including a reaction tank 20 to which an acid is added and reacted, and a solid-liquid separation tank 21 that precipitates and separates the generated calcium carbonate, magnesium carbonate, and the like, and includes components that cause scaling such as calcium and magnesium. It is intended to be removed.

  Organic wastewater containing high-concentration salts, such as human waste and landfill leachate, is purified to a considerable extent by combining the aforementioned biological treatment, coagulation treatment, solid-liquid separation membrane treatment, etc. In treated human waste water, persistent organic substances such as oxides of bile pigment and denatured hemoglobin remain. In addition, persistent humic acid and fulvic acid remain in the treated water of landfill leachate.

  These remaining organic substances cause a foaming phenomenon in the highly concentrated third stage evaporator 10. When foaming occurs, bubbles containing high-concentration salts flow out on the condensate side, deteriorating the quality of the discharged water. In addition, since these hardly decomposable substances are colored components, the recovered crystalline salt exhibits a color such as black, which becomes an obstacle when used as industrial salts.

Organic substances such as bile pigment oxides, hemoglobin denatured products, humic acid, and fulvic acid that cause the above problems can be adsorbed by activated carbon, so supply salt-containing treated water containing them to the first stage evaporator 8 It can be removed by passing through the active treatment device 19 in advance.
Further, instead of the activated carbon adsorption treatment, it is possible to perform ozone oxidation treatment to decompose and remove these organic substances. Further, after the ozone oxidation treatment, it is also possible to perform an activated carbon treatment.

  By providing an activated carbon treatment device 19 or an ozone oxidation treatment device (not shown) to remove organic matter, not only the salt without coloring can be recovered, but also the amount of organic matter in the concentrated liquid in the evaporator can be reduced. Since it reduces, there is also an advantage that the concentration rate can be increased and waste liquid discharged out of the system can be reduced.

  In treated water containing high-concentration salts, calcium and magnesium are usually dissolved, and they become solid carbonates and sulfates by evaporation and concentration and adhere to various devices such as evaporators. Scaling occurs.

In particular, scaling may occur on the surface of the heat transfer tube in the second stage evaporator 9 having a high concentration rate with respect to the desalted raw water. However, this problem can be prevented by providing the softening device B and removing calcium, magnesium, and the like in advance.
In addition, although the softening apparatus B is installed in the back | latter stage of the 1st stage evaporator 8 in the figure, it is also possible to arrange | position in the front | former stage of the 1st stage evaporator 8.

By treating such treated water containing high-concentration salts with the activated carbon treatment device 19 and the softening device B in advance, scaling problems in the second-stage evaporator 9 and the third-stage evaporator 10 The problem of foaming inside and the problem of coloring the recovered crystal salt can be solved.
That is, the embodiment of FIG. 2 provided with the activated carbon treatment device 19 or the ozone oxidation treatment device (not shown) or / and the softening device B can further improve the scaling problem as compared with the embodiment shown in FIG. In addition, it is possible to recover industrial salt without coloring.

  In the embodiment of FIGS. 1 and 2, urine has been mainly described as an example. However, the present invention is similarly applied to organic wastewater containing various high-concentration salts such as industrial wastewater to obtain the same effect. be able to.

It is the schematic which shows one Embodiment of this invention typically. It is a block diagram which shows typically other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Separator 2 Primary nitrification denitrification tank 3 Secondary nitrification denitrogenation tank 4 First stage membrane separation tank 5 Coagulation tank 6 Second stage membrane separation tank 7 Desalination raw water tank 8 First stage evaporator 9 Second stage Eye evaporator 10 Third stage evaporator 11 Steam boiler 12 Centrifugal separator 13 Mother liquor tanks 14, 15, 16 Capacitors 17, 19 Activated carbon treatment equipment 18 Contact tank 20 Reaction tank 21 Solid-liquid separation tank A Biological treatment equipment B Softening equipment

Claims (7)

Salt-containing treated water obtained by treating organic wastewater containing high-concentration salt in combination with biological treatment, flocculation treatment, solid-liquid separation membrane treatment, etc., is concentrated in multiple stages using multiple evaporators. A method for desalting salt-containing treated water, wherein the salt-containing treated water is separated.   2. The salt-containing treated water according to claim 1, wherein organic substances in the salt-containing treated water are previously removed by activated carbon adsorption treatment and / or ozone oxidation treatment and then supplied to the first stage evaporator. Salt method.   3. The salt-containing treated water according to claim 1, wherein calcium salt or the like contained in the salt-containing treated water is removed in advance as a carbonate before or after the first-stage evaporator. Desalting method.   4. The method for desalinating salt-containing treated water according to claim 1, wherein the salt is precipitated and separated and then recovered as an industrial salt.   Multiple evaporators that sequentially concentrate salt-containing treated water obtained by combining organic wastewater containing high-concentration salt with biological treatment, coagulation treatment, solid-liquid separation membrane treatment, etc., and precipitated salts A demineralizer for salt-containing treated water, comprising a centrifuge for separating water.   An activated carbon adsorbing device and / or an ozone oxidation device for removing organic substances contained in the salt-containing treated water is provided in a previous stage of the first stage evaporator to which the salt-containing treated water is supplied. Item 6. A desalinization apparatus for salt-containing treated water according to Item 5. The softening apparatus for removing the calcium salt etc. which are contained in the said salt containing treated water as carbonate is provided in the front | former stage or the back | latter stage of a 1st stage evaporator, The Claims 5 and 6 characterized by the above-mentioned. Desalination equipment for salt-containing treated water.

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