JP2022183507A - Dialysis waste liquid treatment method - Google Patents

Abstract

To provide a dialysis waste liquid treatment method that removes unnecessary potassium ion and urea removed from a body, while collecting necessary electrolyte components from dialysis wastewater.SOLUTION: In a dialysis waste liquid treatment method, in which an undiluted solution is treated using a separation membrane module 1 having a separation membrane 1 and a separation membrane module 2 having a separation membrane 2 to be separated into purified liquid having water and electrolytes collected therefrom and waste liquid containing neutral low molecules such as urea, the undiluted solution is dialysis waste liquid containing at least electrolytes and neutral low molecules. A pore diameter of the separation membrane 1 which is measured using a positron annihilation lifetime measurement technique is 7Å or more and a pore diameter of the separation membrane 2 which is measured using the positron annihilation lifetime measurement technique is 7Å or less, and permeated liquid of the separation membrane module 1 is supplied to the separation membrane module 2 to perform the separation treatment.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for treating dialysis waste fluid.

Among the needs for various selective separation technologies, in recent years, the number of patients undergoing artificial dialysis treatment has been increasing worldwide as living standards have improved. Technology is gaining attention. In general artificial dialysis treatment, it is necessary to use a large amount of dialysate of 90L to 150L in one treatment. Since the dialysate used for artificial dialysis treatment contains waste products such as urea that have migrated from the blood, the dialysate is basically discarded after one use. As a result, there is a problem that a large amount of dialysis waste liquid is generated.
As a method for preparing a dialysate, a dialysate is generally prepared by adding necessary salt, glucose, etc. to pure water obtained by treating tap water with a reverse osmosis membrane or the like. However, in water shortage areas where the supply of tap water is intermittent, it may be difficult to secure the necessary amount of tap water, and there is a demand for reducing the amount of water used. Furthermore, even in areas with a sufficient water supply, if the water supply continues to be cut off during a disaster, dialysate cannot be made from tap water. Therefore, there is an increasing demand for reuse of dialysis waste fluid by removing waste products such as urea from dialysis waste fluid and reusing it as dialysis fluid, and several proposals have been made for dialysis waste fluid recycling technology.
For example, it has been proposed to remove impurities, waste products, and electrolytes from dialysis effluent by means of sorbents, but regeneration of dialysis effluent requires several kilograms of sorbent, depending on the dialysis treatment being performed. A system that minimizes weight and cost is desired.
Patent Literature 1 proposes a system in which impurities are removed using a reverse osmosis membrane after salt is removed to some extent by an adsorbent or electrodialysis.

WO2020/218571

The technique described in Patent Document 1 is a technique for separating waste products such as urea using a reverse osmosis membrane having a pore size of 7.0 Å or less to regenerate dialysis waste fluid. In this technique, it is necessary to add salt to the regeneration solution, which is costly.
Therefore, a system for recovering and reusing the required salt from the dialysis waste fluid is required, but in this case, potassium ions, which are waste products, are also recovered and reused. Controlling the blood potassium ion concentration also plays an important role in dialysis, since accumulation of potassium ions in the body of dialysis patients may cause hyperkalemia.
Accordingly, an object of the present invention is to provide a dialysis waste liquid treatment method for removing unnecessary potassium ions and urea removed from the body while recovering necessary electrolyte components from the dialysis waste liquid.

In order to achieve the above objects, the dialysis waste fluid treatment method of the present invention has any one of the following configurations (1) to (12).
(1) The undiluted solution is treated with the separation membrane module 1 having the separation membrane 1 and the separation membrane module 2 having the separation membrane 2, and the purified liquid obtained by recovering water and electrolytes, and the waste liquid containing neutral low molecules such as urea. wherein the undiluted solution is a dialysis waste liquid containing at least an electrolyte and a neutral low-molecular weight molecule, and the separation membrane 1 has a pore size of 7 Å or more as measured by a positron annihilation lifetime measurement method. , the separation membrane 2 has a pore size of 7 Å or less as measured by a positron annihilation lifetime measurement method, and the permeate of the separation membrane module 1 is supplied to the separation membrane module 2 for separation treatment,
A dialysis waste liquid treatment method characterized by satisfying at least one of the following requirements (i) and (ii).
(i) A part of the permeated liquid of the separation membrane module 2 is mixed with the raw liquid and then supplied to the separation membrane module 1, and all or part of the remaining permeated liquid of the separation membrane module 2 is mixed with the raw liquid. to obtain a purified solution.
(ii) After mixing the whole amount of the permeated liquid of the separation membrane module 2 with the raw liquid, it is supplied to the feed side of the separation membrane module 1 to obtain the concentrated liquid of the separation membrane module 1 as a purified liquid.
(2) When a solution 1 in which 10000 mg / L sodium chloride (NaCl) and 250 mg / L urea are mixed is supplied to the separation membrane 1 at 36 ° C. and a pressure of 1.2 MPa, the permeate to the feed liquid (1) that the sodium chloride removal rate of the separation membrane 1 is 90% or more and the urea removal rate of the separation membrane 1 is 25% or less, with respect to the removal rate defined by the reduction rate of the component concentration in the 4. The method for treating dialysis waste fluid according to .
(3) When a solution 2 in which 1000 mg/L sodium chloride (NaCl) and 700 mg/L urea are mixed is supplied to the separation membrane 2 at 36 ° C. and a pressure of 1.8 MPa, the permeate to the feed liquid For the removal rate defined by the reduction rate of the component concentration in
The dialysis waste liquid treatment method according to (1) or (2), wherein the separation membrane 2 has a urea removal rate of 85% or more.
(4) In the requirement (i) above, the ratio of the amount of a part of the permeated liquid of the separation membrane module 2 mixed with the raw liquid to the amount of the permeated liquid of the separation membrane module 2 is 0.6 or more ( 1) A method for treating dialysis waste fluid according to any one of (3).
(5) The dialysis waste liquid treatment method according to any one of (1) to (4), wherein the ratio of the purified liquid to the stock liquid is 75% or more.
(6) The dialysis waste liquid treatment method according to any one of (1) to (5), wherein the separation membrane includes a support layer and a separation functional layer membrane containing at least one of polyamide and cellulose acetate.
(7) The dialysis waste liquid treatment method according to any one of (1) to (6), wherein the separation membrane includes a support layer and a separation functional layer membrane containing polyamide.
(8) A dialysis waste liquid treatment apparatus that separates and treats a stock solution with a separation membrane module 1 and a separation membrane module 2, wherein the separation membrane module has a separation membrane,
The separation membrane 1 has a pore size of 7 Å or more measured by a positron annihilation lifetime measurement method, the separation membrane 2 has a pore size of 7 Å or less measured by a positron annihilation lifetime measurement method, and the separation membrane module. A permeate solution line containing a permeate obtained from the permeate side of 1 is connected to the feed side of the separation membrane module 2,
A dialysis waste liquid treatment apparatus characterized by satisfying at least one of the following requirements (i) and (ii).
(i) The permeated liquid line of the separation membrane module 2 is branched into two, one of which is connected to the raw liquid line, and the other of the permeated liquid line of the separation membrane module 2 is connected to the concentrated liquid line of the separation membrane module 1. and use it as a purified liquid line.
(ii) The permeated liquid line of the separation membrane module 2 is connected to the raw liquid line, and the concentrated liquid line of the separation membrane module 1 is used as the purified liquid line.
(9) When a solution 1 of a mixture of 10000 mg/L sodium chloride (NaCl) and 250 mg/L urea is supplied to the separation membrane 1 at 36 ° C. and a pressure of 1.2 MPa, the permeate to the feed liquid Regarding the removal rate defined by the reduction rate of the component concentration in the separation membrane 1, the sodium chloride removal rate of the separation membrane 1 is 90% or more and the urea removal rate of the separation membrane 1 is 25% or less, (8) 4. The dialysis waste liquid treatment device according to .
(10) When a solution 2 in which 1000 mg/L sodium chloride (NaCl) and 700 mg/L urea are mixed is supplied to the separation membrane 2 at 36 ° C. and a pressure of 1.8 Mpa, the permeate to the feed liquid For the removal rate defined by the reduction rate of the component concentration in
The dialysis waste liquid treatment method according to (8) or (9), wherein the separation membrane 2 has a urea removal rate of 85% or more.
(11) The dialysis waste liquid treatment apparatus according to any one of (8) to (10), wherein the separation membrane includes a support layer and a separation functional layer membrane containing at least one of polyamide and cellulose acetate.
(12) The dialysis waste liquid treatment apparatus according to any one of (8) to (11), wherein the separation membrane includes a support layer and a separation functional layer membrane containing polyamide.

According to the dialysis waste liquid treatment method of the present invention, a purified liquid obtained by removing unnecessary potassium ions and urea removed from the body while leaving the necessary electrolyte components even under low-pressure operation can be recovered from the dialysis waste liquid at a high recovery rate.

BRIEF DESCRIPTION OF THE DRAWINGS It is an example of the schematic diagram of the dialysis waste fluid processing apparatus of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is an example of the schematic diagram of the dialysis waste fluid processing apparatus of this invention. It is an example of a schematic diagram of a conventional dialysis waste liquid treatment apparatus. It is an example of a schematic diagram of a conventional dialysis waste liquid treatment apparatus.

EMBODIMENT OF THE INVENTION Below, although embodiment of this invention is described in detail, referring drawings, this invention is not limited at all by these.
<Regarding dialysis and dialysis wastewater>
A known method is applied for dialysis. A dialyzer has a dialysis membrane that is permeable to toxins such as urea and impermeable to plasma components. One side of the dialysis membrane is supplied with dialysate while the other side is supplied with blood. The composition of dialysate is known and includes sodium ions, potassium ions, calcium ions, magnesium ions, glucose and the like. Urea in the blood is removed from the blood by diffusing into the dialysate through the dialysis membrane. Potassium ions are one of the substances that need to be removed by dialysis other than urea. Since about 90% of potassium ions are excreted by the kidneys, dialysis patients tend to accumulate potassium ions. Hyperkalemia can cause cardiac arrest, and control of blood potassium ion concentration also plays an important role in dialysis. As a dialysis system, it is necessary to remove 26% to 35% of blood potassium ions in each dialysis to control the blood potassium ion concentration.
It is assumed that the dialysis waste fluid that has passed through the dialysis machine contains 10000 mg/L of electrolyte, of which 100 mg/L of potassium ions and 600 mg/L of urea, which is a neutral molecule, is contained. Removal of about 70% of urea and removal of potassium ions in the range of 2 to 12% from the dialysis waste solution is preferable as a regeneration solution, and recovery of 80% or more of electrolytes is more preferable from the viewpoint of cost reduction.
<Process overview>
1 and 2 show one embodiment of the dialysis waste fluid treatment method according to the present invention. In the dialysis waste liquid treatment apparatus shown in FIGS. 1 and 2, both the separation membrane module 1 and the separation membrane module 2 are normal separation membrane modules with no feed on the permeate side. In a typical separation membrane module, a pressurized feed is introduced to the feed side of the module to obtain a concentrate and a permeate.
The separation membrane module 1 has a high urea permeability and a high electrolyte removal rate. The separation membrane module 2 highly removes all components contained in the permeated water of the separation membrane module 1 such as urea and electrolytes. Since the concentrate (105) of the separation membrane module 1(1) has a higher electrolyte concentration rate than urea, the electrolyte is contained more preferentially. On the other hand, the permeated liquid (106) of the separation membrane module 1 contains a large amount of urea and a small amount of electrolyte. The permeate (106) of separation membrane 1 is treated in separation membrane module 2 (2) to obtain concentrate (108) and permeate (109) of separation membrane module 2. Since the separation membrane module 2 removes all components to a high degree, the liquid permeated through the separation membrane module 2 contains both electrolytes containing potassium ions and urea in very small amounts. Also, the concentrated liquid (108) of the separation module 2 containing a large amount of urea is discharged outside the system. In the dialysis waste liquid treatment method shown in FIG. 1, part of the permeated liquid (109) of the separation membrane module 2, and in FIG. It is mixed with the stock solution (101) to be circulated. The remaining permeate (109) of the separation membrane module 2 and the concentrate (105) of the separation membrane module 1 are mixed to obtain a purified liquid (102) containing little urea but much electrolyte.
It is assumed that the dialysis waste liquid used in the dialysis waste liquid treatment method of the present invention contains 1000 mg/L or more as a total component concentration. In the dialysis waste liquid treatment method without circulation of the permeated liquid of the separation membrane module 2, there is a problem that the concentrate (105) of the separation membrane module 1 becomes highly concentrated. However, the concentration of the feed liquid (104) of the separation membrane module 1 is lowered by the above circulation, and the permeated liquid (109) of the separation membrane module 2 is treated at a lower pressure than the dialysis waste liquid treatment method that does not circulate. becomes possible. If it can be processed at low pressure, there is no need to use a high-pressure pump, a high-pressure flow path, or a pressure vessel, which is expected to reduce equipment costs and noise. The ratio of the amount of circulating (110) to the amount of permeating liquid (109) in the separation membrane module 2 is preferably 0.6 or more, and more preferably 0.8 or more to achieve a urea removal rate of 70% or more for the entire system.
Here, the urea removal rate of the entire system was obtained from the following formula.
Urea removal rate = [(urea concentration of stock solution (101)) x (flow rate of stock solution (101)) - (urea concentration of purified solution (102)) x (flow rate of purified solution (102))]/[(stock solution Urea concentration of (101)) × (flow rate of undiluted solution (101))] × 100 [%]
The ratio of the purified liquid to the supplied raw liquid, that is, the water recovery rate of the entire system, is preferably 75% or more. is preferably 90% or higher for the entire system.
Also, for concentration adjustment of the purified liquid, a part of the permeated liquid of the separation membrane module 2 may be taken out, or pure water or a solution may be added to the purified liquid.
In order to embody the dialysis waste liquid treatment method of the present invention, a dialysis waste liquid treatment apparatus can be assembled by constructing lines according to the flow described above and arranging valves and pumps at appropriate positions.
<Membrane Conditions Necessary for Establishing the Process>
The separation membrane module 1 uses the separation membrane 1, and the separation membrane module 2 uses the separation membrane 2, respectively. Separation membrane 1 has a pore diameter of 7 Å or more as measured by a positron annihilation lifetime measurement method. From the viewpoint of using the dialysis waste fluid treatment system at home, separation membrane 1 with a pore size of 7 Å or more can have practical water permeability, and the system can regenerate dialysate in a short period of time. Moreover, in order to ensure the required electrolyte removal rate, the pore size of the separation membrane 1 is more preferably 10 Å or less.
Separation membrane 2 has a pore size of 7 Å or less as measured by a positron annihilation lifetime measurement method. Since the pore diameter of the separation membrane is 7 Å or less, the separation membrane module 2 can highly remove all components contained in the permeated water of the separation membrane module 1 such as urea and electrolytes.
Pore size is measured using positron annihilation lifetime measurements. The positron annihilation lifetime measurement method measures the time from when the positron enters the sample until it annihilates (on the order of several hundred picoseconds to several tens of nanoseconds), and based on the annihilation lifetime, 0.1 to 10 nm This is a non-destructive method for evaluating information such as the size of vacancies, their number density, and their size distribution. This measuring method is described in "Experimental Chemistry Course, 4th Edition", Vol. 14, p. 485, edited by The Chemical Society of Japan, Maruzen Co., Ltd. (1992).
The average pore radius R in the separation functional layer of the separation membrane according to the present invention is obtained from the following formula (1) based on the positron annihilation lifetime τ. Formula (1) shows the relationship when it is assumed that o-Ps exists in holes of radius R in an electron layer of thickness ΔR, and ΔR is empirically determined to be 0.166 nm ( Nakanishi et al., Journal of Polymer Science, Part B: Polymer Physics, Vol.27, p.1419, John Wiley & Sons, Inc. (1989).

Hereinafter, the salt removal rate and urea removal rate of the separation membrane 1 are for a solution 1 in which 10000 mg/L sodium chloride (NaCl) and 250 mg/L urea are mixed at pH 7, and the pressure is 1.2 MPa. It is defined as the reduction rate of the concentration of the component in the permeated solution relative to the concentration of the component in the solution.
In addition, the salt removal rate and urea removal rate of the separation membrane 2 are the supply solution when the pressure is 1.8 MPa with respect to the solution 2, which is a mixture of 1000 mg / L sodium chloride (NaCl) and 700 mg / L urea at pH 7. Defined as the rate of decrease in component concentration in the permeated solution relative to the component concentration in the medium.
The concentration of urea is measured using the urease GLDH method. The urease GLDH method is a method for measuring BUN by performing the following first reaction and second reaction and measuring the amount of change in coenzyme (NADPH).
(first reaction)
In reaction formula (II), endogenous ammonia generated in reaction formula (I) is eliminated by the action of α-ketoglutaric acid, reduced nicotinamide adenine dinucleotide phosphate (NADPH), and glutamate dehydrogenase (GLDH). The resulting oxidized nicotinamide adenine dinucleotide phosphate (NADP) is reduced to NADPH by the action of L-isocitrate dehydrogenase (ICDH) in reaction formula (III).
(Second reaction)
After scavenging endogenous ammonia by the first reaction, urea is decomposed into ammonia and carbon dioxide by the action of urease. This ammonia and α-ketoglutarate (α-KG) are converted into glutamic acid by the action of GLDH, and at the same time NADPH is converted into NADP. NADPH has an absorption maximum at 340 nm, and the rate of decrease in absorbance is measured to determine the urea nitrogen value. At this time, the reaction formula (III) of the first reaction is terminated by the action of the chelating agent added to the second reagent.
Urea + H ₂ O (+ urease) → 2NH ₃ + CO ₂ (I)
α-ketoglutarate+NH ₃ +NADPH+H ⁺ (+GLDH)→glutamic acid +NADP ⁺ +H ₂ O (II)
NADP ⁺ + L-isocitric acid (+ICDH) → NADPH ⁺ + α-ketoglutarate + CO ₂ (III)
In order to make the electrolyte recovery rate of the whole system 80% or more, it is preferable that the sodium chloride removal rate of the separation membrane 1 is 90% or more. In addition, in order to preferentially remove only urea by about 70% in the entire system, the urea removal rate of the separation membrane 1 is preferably 25% or less, and the urea removal rate of the separation membrane 2 is 85% or more. is preferred.
In the system, potassium ions are recovered together with other electrolytes and accumulated in the regenerated dialysate. As a result of close examination, if the salt removal rate of the separation membrane module 1 is in the range of 93% to 99%, potassium ions are removed in the range of 2 to 12% as a whole system, and the blood potassium ion removal rate is 26% to 26%. It was found that it could be controlled within a range of 35%.
Here, the electrolyte recovery rate and potassium ion removal rate of the entire system were obtained from the following equations.
Electrolyte recovery rate = (electrolyte concentration of purified solution (102)) x (flow rate of purified solution (102)) / [(electrolyte concentration of undiluted solution (101)) x (flow rate of undiluted solution (101))] x 100 [%]
Potassium ion removal rate = [(potassium ion concentration of stock solution (101)) x (flow rate of stock solution (101)) - (potassium ion concentration of purified solution (102)) x (flow rate of purified solution (102))]/ [(potassium ion concentration of stock solution (101)) x (flow rate of stock solution (101))] x 100 [%]
As the separation membrane used in the dialysis waste liquid treatment method of the present invention, a separation membrane having separation performance corresponding to the electrolyte components desired to remain in the solution and the potassium ions and urea desired to be removed is used. The separation membrane may be a single layer or a composite membrane comprising a separation functional layer and a substrate. In addition, the composite membrane may further have a porous support layer between the separation function layer and the substrate.
The separation function layer may be a layer having both a separation function and a support function, or may have only a separation function. In addition, the “separation function layer” refers to a layer having at least a separation function.
When the separation function layer has both a separation function and a support function, a layer containing as a main component a polymer selected from the group consisting of cellulose, polyvinylidene fluoride, polyethersulfone and polysulfone is preferably applied as the support function layer. be.
On the other hand, as the separation functional layer, a crosslinked polymer is preferably used because the pore size can be easily controlled and the durability is excellent. In particular, a composite membrane having a separation function layer containing at least one of cellulose acetate and polyamide is preferable in terms of excellent separation performance of components in the feed liquid, and in particular polyamide having higher removal performance is preferable. A composite membrane with a separating functional layer is preferred. In order to maintain durability against operating pressure and high water permeability and blocking performance, a structure in which polyamide is used as a separation functional layer and supported by a support made of a porous membrane or nonwoven fabric is suitable.
The porous support layer is a layer that supports the separation functional layer, and can also be called a porous resin layer when the material is a resin.
The material used for the porous support layer and its shape are not particularly limited. For example, the porous support layer may be formed on the substrate with a porous resin. Although the composition of the porous support layer is not particularly limited, it is preferably made of a thermoplastic resin. Here, the thermoplastic resin is made of a chain polymer substance, and is a resin that exhibits the property of being deformed or fluidized by an external force when heated. Examples of thermoplastic resins include homopolymers or copolymers of polysulfone, polyethersulfone, polyamide, polyester, cellulosic polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, and polyphenylene oxide, either alone or in blends. can be used. Cellulose polymers such as cellulose acetate and cellulose nitrate, and vinyl polymers such as polyethylene, polypropylene, polyvinyl chloride, polyacrylonitrile, and acrylonitrile-styrene copolymers can be used. Among these, it is preferable to use polysulfone, which has high chemical, mechanical and thermal stability and whose pore size is easy to control.
The porous support layer is formed, for example, by casting the above N,N-dimethylformamide solution of polysulfone to a certain thickness on a base material (for example, tightly woven polyester nonwoven fabric) described later, and wet-coagulating it in water. It can be manufactured by
The separation membrane may have a substrate from the viewpoint of the strength and dimensional stability of the separation membrane. As the base material, it is preferable to use a fibrous base material in terms of strength and fluid permeability.
As the substrate, a long-fiber nonwoven fabric and a short-fiber nonwoven fabric can be preferably used.
<Element>
The separation membrane 1 and the separation membrane 2 in the present invention are a spiral element in which a flat membrane is wrapped around a water collection tube, or a flat membrane on both sides of a plate-type support plate. It can be configured as a plate-and-frame type element laminated at regular intervals, a tubular type element using tubular membranes, or a hollow fiber membrane element in which hollow fiber membranes are bundled and housed in a case. Furthermore, one or a plurality of these elements are connected in series and housed in a pressure vessel to form a separation membrane module. The form of the element may be any form, but from the viewpoint of operability and interchangeability, it is preferable to use a spiral type element. A spiral-type separation membrane element is obtained by winding a laminate of a separation membrane, a permeate-side channel material, and a feed-side channel material around a perforated water collection tube for collecting the permeated liquid.
The material of the channel material on the supply side is not particularly limited, and it may be the same material as the separation membrane or a different material.
Here, the separation membrane has a permeate side and a concentration side, and the separation membranes formed so that the feed side faces each other are called a separation membrane pair.
The separation membrane forms a separation membrane pair with the feed side channel material and the permeate side channel material. The separation membranes are arranged so that the supply-side surfaces face each other with the supply-side channel material interposed therebetween. Further, a permeation-side channel material is arranged between the surfaces on the permeation side. In the permeate-side channel, only one inner side in the winding direction is open between the permeate-side surfaces so that the permeated fluid flows into the perforated central tube, and the other three sides are sealed.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples.
(Measurement of separation membrane performance)
For PA membrane A, PA membrane B, PA membrane C, PA membrane F, and CA membrane, pH 7, 10000 mg / L sodium chloride (NaCl) and 250 mg / L urea mixed solution 1, pressure 1.2 MPa The separation membrane performance is defined as the NaCl removal rate and the urea removal rate when the membrane permeation flux is 0.35 m/d.
For PA membrane D, PA membrane E, and PA membrane G, the membrane permeation flux was 0.8 MPa with respect to solution 2, which was a mixture of 1000 mg/L sodium chloride (NaCl) and 700 mg/L urea at pH 7. The separation membrane performance is defined as the NaCl removal rate and the urea removal rate at 35 m/d.
(Positron annihilation lifetime measurement method by positron beam method)
The positron annihilation lifetime measurement of the separation functional layer in each example was performed using the positron beam method as follows. That is, the separation functional layer was dried at room temperature under reduced pressure and cut into 1.5 cm×1.5 cm squares to obtain test samples. A thin-film positron annihilation lifetime measurement device equipped with a positron beam generator (this device is described in detail in, for example, Radiation Physics and Chemistry, 58, 603, Pergamon (2000)), beam intensity 1 keV, room temperature , under vacuum, the test samples were measured with a barium difluoride scintillation counter using a photomultiplier tube with a total count of 5 million and analyzed with the POSI TRONFIT. The average pore diameter was calculated from the average positron annihilation lifetime τ of the fourth component obtained by the analysis.
(Preparation of microporous support membrane)
A 16.0% by weight DMF (dimethylformamide) solution of polysulfone (PSf) was cast at room temperature (25° C.) to a thickness of 200 μm on a polyester nonwoven fabric (airflow rate of 2.0 cc/cm ² /sec), and immediately immersed in pure water. A support film was prepared by immersing in and leaving for 5 minutes.
(Preparation of PA membrane A)
A 1.5% by weight aqueous solution of m-phenylenediamine was prepared. The support film obtained by the above operation was immersed in the above aqueous solution for 2 minutes, the support film was slowly lifted vertically, nitrogen was blown from an air nozzle to remove excess aqueous solution from the surface of the support film, and the temperature was maintained at 25°C. A 25° C. decane solution containing 0.065% by weight of trimesic acid chloride (TMC) was applied in a booth kept at 25° C. so that the surface was completely wetted, and left to stand for 60 seconds to obtain a film. The separation membrane performance of the obtained membrane was 97% NaCl removal rate and 18% urea removal rate. The pore size measured using positron annihilation lifetime spectroscopy was 7.2 Å.
(Preparation of PA film B)
A 1.8% by weight aqueous solution of m-phenylenediamine was prepared. The support film obtained by the above operation was immersed in the above aqueous solution for 2 minutes, the support film was slowly lifted vertically, nitrogen was blown from an air nozzle to remove excess aqueous solution from the surface of the support film, and the temperature was maintained at 25°C. A decane solution containing 0.06% by weight of trimesic acid chloride (TMC) at 25° C. was applied in a booth kept at 25° C. so that the surface was completely wetted, and allowed to stand for 60 seconds to obtain a film. The separation membrane performance of the obtained membrane was 98% NaCl removal rate and 25% urea removal rate. The pore size measured using positron annihilation lifetime spectroscopy was 7.0 Å.
(Preparation of PA film C)
A 0.2 wt% aqueous solution of piperazine was made. The support film obtained by the above operation was immersed in the above aqueous solution for 2 minutes, the support film was slowly lifted vertically, nitrogen was blown from an air nozzle to remove excess aqueous solution from the surface of the support film, and the temperature was maintained at 45°C. A 45° C. decane solution containing 0.17% by weight of trimesic acid chloride (TMC) was applied in a booth kept at 20° C. so that the surface was completely wetted, and left to stand for 1 minute. Next, in order to remove excess solution from the membrane, the membrane was held vertically for 1 minute to drain, and dried by blowing air at 25° C. using an air blower. After drying, it was immediately washed with water and stored at room temperature to obtain a nanofiltration membrane. The separation membrane performance of the obtained membrane was 93.7% NaCl removal rate and 16% urea removal rate. The pore size measured using positron annihilation lifetime spectroscopy was 9.0 Å.
(Preparation of PA film D)
A 6.0% by weight aqueous solution of m-phenylenediamine was prepared. The support film obtained by the above operation was immersed in the above aqueous solution for 2 minutes, the support film was slowly lifted vertically, nitrogen was blown from an air nozzle to remove excess aqueous solution from the surface of the support film, and the temperature was maintained at 45°C. A 45° C. decane solution containing 0.17% by weight of trimesic acid chloride (TMC) was applied in a booth maintained at 45° C. so that the surface was completely wetted and allowed to stand for 10 seconds. The film was placed in an oven at 140° C. and heated for 30 seconds while supplying steam at 100° C. from a nozzle provided on the back side of the film to obtain a film. The separation membrane performance of the obtained membrane was 99.6% NaCl removal rate and 90% urea removal rate. The pore size measured using positron annihilation lifetime spectroscopy was 5.1 Å.
(Preparation of PA film E)
A 5.5% by weight aqueous solution of m-phenylenediamine was prepared. The support film obtained by the above operation was immersed in the above aqueous solution for 2 minutes, the support film was slowly lifted vertically, nitrogen was blown from an air nozzle to remove excess aqueous solution from the surface of the support film, and the temperature was maintained at 45°C. A 45° C. decane solution containing 0.15% by weight of trimesic acid chloride (TMC) was applied in a booth kept at 20° C. so that the surface was completely wetted, and left to stand for 10 seconds. The film was placed in an oven at 140° C. and heated for 30 seconds while supplying steam at 100° C. from a nozzle provided on the back side of the film to obtain a film. The separation membrane performance of the obtained membrane was 99.6% NaCl removal rate and 90% urea removal rate. The pore size measured using positron annihilation lifetime spectroscopy was 6.0 Å.
(Preparation of PA film F)
A 2.0% by weight aqueous solution of m-phenylenediamine was prepared. The support film obtained by the above operation was immersed in the above aqueous solution for 2 minutes, the support film was slowly lifted vertically, nitrogen was blown from an air nozzle to remove excess aqueous solution from the surface of the support film, and the temperature was maintained at 25°C. A 25° C. decane solution containing 0.12% by weight of trimesic acid chloride (TMC) was applied in a booth maintained at 25° C. so that the surface was completely wetted, and left to stand for 40 seconds. The film was placed in an oven at 140° C. and heated for 30 seconds while supplying steam at 100° C. from a nozzle provided on the back side of the film to obtain a film. The separation membrane performance of the obtained membrane was 99.0% NaCl removal rate and 50% urea removal rate. The pore size measured using positron annihilation lifetime spectroscopy was 6.8 Å.
(Preparation of PA film G)
An aqueous solution of 1.8% by weight of m-phenylenediamine and 4.5% by weight of ε-caprolactam was prepared. After applying to the support film obtained by the above operation and removing excess aqueous solution from the support film surface by blowing nitrogen from an air nozzle, a 25 ° C. n-decane solution containing 0.06% by weight of trimesic acid chloride was applied to the surface. was applied so that it was completely wetted. After that, excess solution was removed from the membrane by air blow, washed with hot water at 80° C., and drained by air blow to obtain a membrane. The separation membrane performance of the obtained membrane was 97.0% NaCl removal rate and 80% urea removal rate. The pore size measured using positron annihilation lifetime spectroscopy was 7.2 Å.
(Preparation of CA film)
A casting solution prepared by mixing 25% by weight of cellulose acetate, 45% by weight of acetone, and 30% by weight of formamide was cast on the support film obtained by the above operation, and the casting solution was evaporated for 2 minutes. immersed in. Next, it was immersed in warm water of 90° C. to obtain a film. The reverse osmosis membrane performance of the obtained membrane was 93.0% NaCl removal rate and 15% urea removal rate. The pore size measured using positron annihilation lifetime spectroscopy was 10 Å.
(Preparation of type I separation membrane element)
Six seawater desalination RO membranes and low-pressure RO membranes were cut and folded with the supply side inward so that the inner peripheral edge formed a crease. : 380 μm, projected area ratio: 0.15) as a channel material on the supply side, and arranged so that the inclination angle of the net-constituting yarn is 45° with respect to the winding direction. In this manner, six pairs of separation membranes having a length of 850 mm and a width of 930 mm or 465 mm were produced. Tricot having a uniform thickness (thickness: 280 μm, groove width: 200 μm, ridge width: 300 μm, groove depth: 105 μm) was prepared as the channel material on the permeate side and cut into six pieces. A permeate-side channel material is placed on the permeate-side surface of the separation membrane, an adhesive is applied to the permeate-side channel so that the inner peripheral end is open, and an ABS (acrylonitrile-butadiene-styrene) perforated material is applied. A central tube (length: 1020 mm, diameter: 30 mm, 40 holes x 1 linear row) was spirally wound. After wrapping, a film is wrapped around the outer periphery and fixed with tape, followed by edge cutting, attachment of end plates, and filament winding. made.
(Undiluted solution)
The undiluted solution was used as artificial dialysis waste. Components in the undiluted solution are salts (100 mg/L of potassium ions out of 10000 mg/L) and urea (630 mg/L).
(Example 1)
An end plate and a brine seal were attached to the prepared separation membrane element, and the element was placed in a pressure vessel to obtain one separation membrane module 1 and one separation membrane module 2. A pump and a valve were prepared as shown in FIG. 2, and pipe connections were made. The valves were adjusted so that the water recovery rate of the entire system was about 97% and the urea removal rate was about 70%.
(Example 2)
A separation membrane module similar to that of Example 1 was prepared except that the width of the separation membrane pair used in modules 1 and 2 was 465 mm. An end plate and a brine seal were attached to the prepared separation membrane element, and the element was placed in a pressure vessel to obtain one separation membrane module 1 and one separation membrane module 2. A pump and a valve were prepared as shown in FIG. 1, and pipe connections were made. The valves were adjusted so that the water recovery rate of the entire system was about 97% and the urea removal rate was about 70%. The permeate circulation ratio of the separation membrane module 2 was 0.85. A part of the permeated liquid of the separation membrane module 2 goes to the purified liquid, so that the amount of water to the modules 1 and 2 is reduced, and the system can be established with half the membrane area of the first embodiment.
(Example 3)
A reverse osmosis membrane module similar to that of Example 1 was prepared except that the reverse osmosis membrane used in the reverse osmosis membrane module 1 was a CA membrane. An end plate and a brine seal were attached to the prepared reverse osmosis membrane element, and the element was placed in a pressure vessel to obtain one reverse osmosis membrane module 1 and one reverse osmosis membrane module 2 . A pump and a valve were prepared as shown in FIG. 1, and pipe connections were made. The valves were adjusted so that the water recovery rate of the entire system was about 97% and the urea removal rate was about 70%. The permeate circulation ratio of the reverse osmosis membrane module 2 was 0.95.
(Example 4)
A separation membrane module was prepared in the same manner as in Example 1 except that PA membrane E was used as the separation membrane for separation membrane module 2 . An end plate and a brine seal were attached to the prepared separation membrane element, and the element was placed in a pressure vessel to obtain one separation membrane module 1 and one separation membrane module 2. A pump and a valve were prepared as shown in FIG. 1, and pipe connections were made. The valves were adjusted so that the water recovery rate of the entire system was about 97% and the urea removal rate was about 70%. The permeate circulation ratio of the separation membrane module 2 was 0.95.
(Example 5)
A separation membrane module was prepared in the same manner as in Example 1 except that PA membrane B was used as the separation membrane for separation membrane module 1 . An end plate and a brine seal were attached to the prepared separation membrane element, and the element was placed in a pressure vessel to obtain one separation membrane module 1 and one separation membrane module 2. A pump and a valve were prepared as shown in FIG. 1, and pipe connections were made. The valves were adjusted so that the water recovery rate of the entire system was about 97% and the urea removal rate was about 70%. The permeate circulation ratio of the separation membrane module 2 was 0.85.
(Example 6)
A separation membrane module was prepared in the same manner as in Example 1 except that PA membrane C was used as the separation membrane for separation membrane module 1 . An end plate and a brine seal were attached to the prepared separation membrane element, and the element was placed in a pressure vessel to obtain one separation membrane module 1 and one separation membrane module 2. A pump and a valve were prepared as shown in FIG. 1, and pipe connections were made. The valves were adjusted so that the water recovery rate of the entire system was about 90%, and the urea removal rate was about 70%. The permeate circulation ratio of the separation membrane module 2 was 0.90.
(Example 7)
A separation membrane module similar to that of Example 1 was prepared. An end plate and a brine seal were attached to the prepared separation membrane element, and the element was placed in a pressure vessel to obtain one separation membrane module 1 and one separation membrane module 2. A pump and a valve were prepared as shown in FIG. 1, and pipe connections were made. The valves were adjusted so that the water recovery rate of the entire system was about 75%, and the urea removal rate was about 60%. The permeate circulation ratio of the separation membrane module 2 was 0.60.

(Comparative example 1)
A separation membrane module similar to that of Example 1 was prepared. A pump and a valve were prepared as shown in FIG. 1, and pipe connections were made. All of the permeated liquid of the separation membrane module 2 is mixed with the concentrated liquid of the separation membrane module 1 (that is, the permeated liquid of the separation membrane module 2 is not circulated to the raw liquid of the separation membrane module 1) to obtain a purified liquid. The permeate circulation valve was adjusted. Since the maximum operating pressure of the apparatus is 5.5 MPa, the valve was adjusted so that the maximum operating pressure was 5.5 MPa, and evaluation was performed under the conditions shown in Table 2. The results were as shown in Table 2. In order to increase the urea removal rate of the entire system, it is necessary to increase the recovery rate of the separation membrane module 1 in order to increase the urea permeability in the separation membrane module 1, but circulation is not performed in the dialysis waste liquid treatment method of FIG. In this case, the osmotic pressure difference in the separation membrane module 1 becomes high, and even 5.5 MPa cannot obtain a sufficient effective pressure, and a urea removal rate cannot be obtained.

(Comparative example 2)
A separation membrane module similar to that of Example 1 was prepared, except that PA membrane F was used as the separation membrane used in separation membrane module 1 . A pump and a valve were prepared as shown in FIG. 1, and pipe connections were made. Since the water recovery rate of the entire system is 90% and the maximum operating pressure of the device is 5.5 MPa, the valve was adjusted so that the maximum operating pressure was 5.5 MPa, and evaluation was performed under the conditions shown in Table 2. The results were as shown in Table 2. Since the urea permeability in the separation membrane module 1 is low, it is necessary to increase the recovery rate of the separation membrane module 1 in order to increase the urea removal rate of the entire system. Even at 5 MPa, a sufficient effective pressure cannot be obtained, and a urea removal rate cannot be obtained.
(Comparative Example 3)
A separation membrane module was prepared in the same manner as in Example 1 except that PA membrane G was used as the separation membrane for separation membrane module 2 . A pump and a valve were prepared as shown in FIG. 1, and pipe connections were made. Since the water recovery rate of the entire system is 90% and the maximum operating pressure of the device is 5.5 MPa, the valve was adjusted so that the maximum operating pressure was 5.5 MPa, and evaluation was performed under the conditions shown in Table 2. The results were as shown in Table 2. When trying to increase the water recovery rate to 90% or more, the urea removal rate is low because the pore size of the separation membrane 2 is large, and it is necessary to increase the recovery rate of the separation membrane module 1, but the urea removal rate is obtained even at 5.5 MPa. can't
(Comparative Example 4)
A separation membrane module was prepared in the same manner as in Example 1, except that PA membrane D was used as the separation membrane used in separation membrane module 1 . A pump and valves were prepared as shown in FIG. 3, and pipe connections were made. The valves were adjusted so that the water recovery rate of the entire system was 90%, and evaluation was performed under the conditions shown in Table 2. The results were as shown in Table 2. Since all of the concentrate in the separation membrane module 1 is discharged, the electrolyte recovery rate becomes 1% or less.
(Comparative Example 5)
A separation membrane module was prepared in the same manner as in Example 1, except that PA membrane D was used as the separation membrane used in separation membrane module 1 . A pump and valves were prepared as shown in FIG. 4, and pipe connections were made. The valves were adjusted so that the water recovery rate of the entire system was 90%, and evaluation was performed under the conditions shown in Table 2. The results were as shown in Table 2. Since all of the concentrate in the separation membrane module 1 is discharged, the electrolyte recovery rate becomes 1% or less.

The present invention is suitable for regeneration of dialysate.

1 separation membrane module 1
2 separation membrane module 2
3 Separation membrane module 1 supply pump 4 Separation membrane module 1 concentrate valve 5 Separation membrane module 2 supply pump 6 Separation membrane module 2 concentrate valve 7 Separation membrane module 2 permeate or purified liquid flow distribution valve 8 Separation membrane module 2 permeate Check valve 101 Undiluted liquid 102 Purified liquid 103 Effluent 104 Separation membrane module 1 feed liquid 105 Separation membrane module 1 concentrated liquid 106 Separation membrane module 1 permeate or permeate side effluent 107 Separation membrane module 2 feed liquid 108 Separation membrane module 2 concentrate Liquid 109 Separation membrane module 2 permeate liquid 110 Separation membrane module 2 permeate liquid circulation

Claims (12)

A raw liquid is treated by a separation membrane module 1 having a separation membrane 1 and a separation membrane module 2 having a separation membrane 2, and separated into a purified liquid obtained by recovering water and electrolytes, and a waste liquid containing neutral low-molecular weight compounds such as urea. A dialysis waste fluid treatment method comprising:
The undiluted solution is a dialysis waste solution containing at least an electrolyte and a neutral low molecule, the separation membrane 1 has a pore size of 7 Å or more as measured by a positron annihilation lifetime measurement method, and the separation membrane 2 is a positron annihilation lifetime measurement method. The permeate of the separation membrane module 1 is supplied to the separation membrane module 2 and subjected to separation treatment,
A dialysis waste liquid treatment method characterized by satisfying at least one of the following requirements (i) and (ii).
(i) A part of the permeated liquid of the separation membrane module 2 is mixed with the raw liquid and then supplied to the separation membrane module 1, and all or part of the remaining permeated liquid of the separation membrane module 2 is mixed with the raw liquid. to obtain a purified solution.
(ii) After mixing the whole amount of the permeated liquid of the separation membrane module 2 with the raw liquid, it is supplied to the feed side of the separation membrane module 1 to obtain the concentrated liquid of the separation membrane module 1 as a purified liquid. When a solution 1 in which 10000 mg / L sodium chloride (NaCl) and 250 mg / L urea are mixed is supplied to the separation membrane 1 at 36 ° C. and a pressure of 1.2 MPa, the component in the permeate for the feed liquid 2. The method according to claim 1, wherein the separation membrane 1 has a sodium chloride removal rate of 90% or more and a urea removal rate of 25% or less with respect to the removal rate defined by the concentration reduction rate. Dialysis waste liquid treatment method. When a solution 2 in which 1000 mg / L sodium chloride (NaCl) and 700 mg / L urea are mixed is supplied to the separation membrane 2 at 36 ° C. and a pressure of 1.8 Mpa, the component in the permeate for the feed liquid For the removal rate defined by the concentration reduction rate,
The dialysis waste liquid treatment method according to claim 1 or 2, wherein the separation membrane (2) has a urea removal rate of 85% or more. Claims 1 to 1, wherein in the requirement (i), the ratio of the amount of a part of the permeated liquid of the separation membrane module 2 mixed with the raw liquid to the amount of the permeated liquid of the separation membrane module 2 is 0.6 or more. 4. The method for treating dialysis waste fluid according to any one of 3. The dialysis waste liquid treatment method according to any one of claims 1 to 4, wherein the ratio of the purified liquid to the raw liquid is 75% or more. The dialysis waste liquid treatment method according to any one of claims 1 to 5, wherein the separation membrane comprises a support layer and a separation functional layer membrane containing at least one of polyamide and cellulose acetate. The dialysis waste liquid treatment method according to any one of claims 1 to 6, wherein the separation membrane comprises a support layer and a separation functional layer membrane containing polyamide. A dialysis waste liquid treatment apparatus that separates and treats a raw liquid with a separation membrane module 1 and a separation membrane module 2, wherein the separation membrane module has a separation membrane,
The separation membrane 1 has a pore size of 7 Å or more measured by a positron annihilation lifetime measurement method, the separation membrane 2 has a pore size of 7 Å or less measured by a positron annihilation lifetime measurement method, and the separation membrane module. A permeate solution line containing a permeate obtained from the permeate side of 1 is connected to the feed side of the separation membrane module 2,
A dialysis waste liquid treatment apparatus characterized by satisfying at least one of the following requirements (i) and (ii).
(i) The permeated liquid line of the separation membrane module 2 is branched into two, one of which is connected to the raw liquid line, and the other of the permeated liquid line of the separation membrane module 2 is connected to the concentrated liquid line of the separation membrane module 1. and use it as a purified liquid line.
(ii) The permeated liquid line of the separation membrane module 2 is connected to the raw liquid line, and the concentrated liquid line of the separation membrane module 1 is used as the purified liquid line. When a solution 1 in which 10000 mg / L sodium chloride (NaCl) and 250 mg / L urea are mixed is supplied to the separation membrane 1 at 36 ° C. and a pressure of 1.2 MPa, the component in the permeate for the feed liquid 9. The method according to claim 8, wherein the separation membrane 1 has a sodium chloride removal rate of 90% or more and a urea removal rate of 25% or less, with respect to the removal rate defined by the concentration reduction rate. Dialysis waste liquid treatment equipment. When a solution 2 in which 1000 mg / L sodium chloride (NaCl) and 700 mg / L urea are mixed is supplied to the separation membrane 2 at 36 ° C. and a pressure of 1.8 Mpa, the component in the permeate for the feed liquid For the removal rate defined by the concentration reduction rate,
The dialysis waste liquid treatment method according to claim 8 or 9, wherein the separation membrane (2) has a urea removal rate of 85% or more. The dialysis waste liquid treatment apparatus according to any one of claims 8 to 10, wherein the separation membrane includes a support layer and a separation functional layer membrane containing at least one of polyamide and cellulose acetate. The dialysis waste liquid treatment apparatus according to any one of claims 8 to 11, wherein the separation membrane includes a support layer and a separation functional layer membrane containing polyamide.

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