CN111315689A

CN111315689A - Water treatment device

Info

Publication number: CN111315689A
Application number: CN201880072691.2A
Authority: CN
Inventors: 高桥淳一
Original assignee: Kurita Water Industries Ltd
Current assignee: Kurita Water Industries Ltd
Priority date: 2018-03-14
Filing date: 2018-10-24
Publication date: 2020-06-19
Also published as: WO2019176156A1; JP2019155293A; JP6468384B1; TW201938251A; SG11202008563SA; TWI757581B

Abstract

A water treatment device comprising: an NF membrane module (4) which receives water from the water system (1) and performs permeation treatment, and which is provided with a selective permeation membrane (NF membrane) that is impermeable to useful components; an RO device (9) for performing deionization treatment on the permeate of the NF membrane module (4); and a module for returning the non-permeate water of the NF membrane module (4) and the permeate water of the RO apparatus (9) to the water system (1).

Description

Water treatment device

Technical Field

The present invention relates to a water treatment apparatus for treating water from a water system and returning the treated water to the water system.

Background

In the open-circulation cooling system, a treatment of treating a cooling tower drain water (blow off water) and returning the treated water to the cooling tower is performed (patent document 1 and the like).

Recently, it is desired to reduce the amount of water used or to recover water, and it is also desired to recover drain water discharged to the outside of a system for performing water treatment, for example, cooling water or a boiler (boiler). However, the existing water recovery technology also removes components effective for water treatment. There is a waste of energy or medicines due to excessive removal of components in water.

In the process of recovering the cooling tower discharge water, a combination treatment of a pretreatment filtration (sand filtration, activated carbon, Microfiltration (MF) membrane, etc.) and a Reverse Osmosis (RO) membrane or an electrodialysis reversal (EDR) (polar inversion electrodialysis apparatus) is performed. In a conventional effluent recovery process, the entire amount of effluent is treated with a pretreatment membrane, an MF membrane, or the like and then supplied to an RO membrane. The RO membrane or the like is used to concentrate water treatment chemicals, dissolved salts, and the like in concentrated water and discharge the concentrated water to the outside of the system, and permeate water of the RO membrane or the like is recovered as recovered water.

[ patent document 1] Japanese patent laid-open No. 2003-1255

In the above-described conventional recovery process, all of various useful components contained in raw water, which is effective components for water treatment, such as calcium, zinc, polymers, phosphoric acid, and chemical components such as phosphonic acid (phosphonic acid), are contained in concentrated water and discharged to the outside of the system. In the conventional recovery process, zinc, phosphoric acid, organic matter (Total organic carbon (TOC), Chemical Oxygen Demand (COD)), and the like are also concentrated in the RO membrane and the like, and thus fouling (fouling) of the RO membrane and the like is likely to occur. In addition, when concentrated water is discharged, it is necessary to perform removal treatment of zinc, phosphoric acid, COD, Biochemical Oxygen Demand (BOD), and the like.

Disclosure of Invention

The invention provides a water treatment device capable of recovering useful components, easily treating water discharged to the outside of a system, and preventing operation failure of the device.

The water treatment device of the present invention comprises: a selectively permeable membrane device which receives water from a water system and performs a permeation treatment, and which is provided with a selectively permeable membrane that is impermeable to a useful component; the deionization device is used for carrying out deionization treatment on the permeation water of the selective permeation membrane device; and means for returning the non-permeate from the selectively permeable membrane device and the deionized water from the deionization unit to the water system.

In one aspect of the present invention, the water of the water system contains at least one of a rust inhibitor, a scale inhibitor and a slime inhibitor.

In one aspect of the present invention, the water system is a cooling water system, a water treatment apparatus, or a makeup water system that supplies makeup water to the water treatment apparatus.

In one embodiment of the present invention, the permselective membrane is a Nanofiltration (NF) membrane, and the deionization apparatus is an RO apparatus or an electrodeionization apparatus.

[ Effect of the invention ]

In the present invention, water from a water system is treated with a selectively permeable membrane (a membrane having a high rejection rate of ions having a valence of 2 or more, a membrane for removing organic substances, or the like), and the water permeated through the selectively permeable membrane is treated with a deionization apparatus such as an RO membrane or an EDR. The non-permeate water that selectively permeates the membrane is then returned to the water system for recovery of the value. And, the deionized water of the deionization apparatus is returned to the water system to recover the water. As described above, the useful component and water are recovered.

In the present invention, since the water supplied to the deionization apparatus has the useful component removed by the selectively permeable membrane, the water discharged from the deionization apparatus does not contain the useful component, and the water discharged from the deionization apparatus can be easily treated. Since the feed water to the deionization apparatus is treated by the selectively permeable membrane, the impurity concentration is reduced, and stable operation of the deionization apparatus can be realized.

When a hollow fiber type low pressure NF membrane is used as the permselective membrane, the membrane can replace the function of the conventional pretreatment membrane, and the apparatus can be miniaturized.

Drawings

Fig. 1 is a block diagram of a water treatment apparatus according to an embodiment.

FIG. 2 is a block diagram of a test apparatus used in the examples.

FIG. 3 is a block diagram of a test apparatus used in examples.

FIG. 4 is a block diagram of a test apparatus used in a comparative example.

Fig. 5 is a graph showing the test results.

Fig. 6 is a graph showing the test results.

Fig. 7 is a graph showing the test results.

Detailed Description

Hereinafter, an embodiment will be described with reference to fig. 1. In fig. 1, the water system is a circulating cooling water system, but the present invention is not limited thereto, and can be applied to treatment of various water systems that hold water containing useful components.

In the water treatment apparatus of fig. 1, a part of water in a water system 1 is supplied by a pump 2 to a pretreatment apparatus 3 including a pretreatment membrane (e.g., MF membrane, sand filtration, MMF (multi membrane filtration), DMF (double membrane filtration), cartridge (cartridge filter), etc.), a filter (purifier), etc., and solid matter having a large particle diameter is removed to obtain pretreatment water. The pretreatment water is supplied to the NF device 4 as a selective permeation membrane device. The non-permeated water (concentrated water) of the NF device 4 is returned to the water system 1 through the pipe 5. A part of the non-permeated water is discharged from the pipe 6 to the outside of the system as necessary.

The permeate from the NF apparatus is supplied to an RO apparatus 9 as a deionization apparatus via a pipe 7 and a pump 8. Instead of the RO apparatus, an electric dialysis apparatus such as EDR may be used. The permeate from the RO apparatus 9 is returned to the water system 1 through a pipe 10. The non-permeate water (concentrate water) of the RO unit 9 is discharged from the system through the pipe 11. In order to improve the water recovery rate, a part of the water is returned to the water supply pipe 7 of the RO apparatus via the pipe 12, and the RO process is performed again.

In the above embodiment, a water treatment chemical such as a rust inhibitor, a scale inhibitor, or a slime inhibitor is added to the cooling water system 1, and the water from the water system 1 contains various useful components (such as a polymer, a phosphate, an organic phosphoric acid compound, zinc ions, and calcium ions). These useful components are recovered by the NF device 4 into non-permeate water and returned to the water system 1. Since deionized water from the RO apparatus 9 is also recovered to the water system 1 through the pipe 10, the amount of makeup water can be reduced by effectively using water.

The concentrated water in the RO apparatus 9 contains components (chloride ions, silica, etc.) which do not require water treatment or whose components determine the upper limit of water treatment. These components are discharged to the outside of the system by discharging the concentrated water. As described above, since components such as chloride and silica, which may cause problems in water treatment, can be selectively removed, the concentration of the above components in the water system can be reduced.

In the water system 1, an operation of discharging (sluw) the useful component from the water system 1 to prevent excessive concentration is performed as needed. In the case of fig. 1, a part of the concentrated water of the NF device is discharged from the pipe 6 to the outside of the system, whereby the amount of the discharged water from the water system can be reduced.

The present invention can be applied to various water systems to which agents such as rust inhibitors and scale inhibitors are added, in addition to cooling water systems.

[ examples ]

[ example 1]

< treatment 1 >

The water sample collected from the actual machine circulating cooling water system was subjected to NF membrane filtration and concentrated by the circulation treatment apparatus using an NF membrane module shown in fig. 2.

In fig. 2, a sample water in a tank (tank)20 is supplied to an NF membrane module 23 via a pump 21 and a pipe 22. A part of the discharged water of the pump 21 is returned to the reservoir 20 through the pipe 29. The concentrated water of the NF membrane module 23 is returned to the storage tank 20 through a pipe 24 including a constant flow valve 25. The permeated water in the NF membrane module 23 is introduced into a permeated water tank 27 through a pipe 26, and the amount of water is measured by a weight measuring instrument 28.

By continuing to operate the device, the water in the reservoir 20 is gradually concentrated.

As the NF membrane, an NF membrane (hollow fiber type NF membrane) manufactured by de.mem corporation (de.mem Limited ASX: DEM) was used. The membrane filtration is carried out under the condition of 50 percent recovery under the inlet pressure of 0.25 MPa-0.3 MPa. 5L of water sample is put into the storage tank 20, and water supply is finished when the water amount of the permeated water reaches 2.5L.

< treatment 2 >

The permeated water obtained in the above-mentioned treatment 1 was added with 10mg/L of scale inhibitor (Kuriver N-500, manufactured by Takara industries, Ltd.) and operated at a recovery rate of permeated water of 70% and a fixed amount of permeated water by using an RO system including an RO membrane (polyamide, PA) membrane ES-20, manufactured by Hydranautics, Ltd.) shown in FIG. 3. The transmembrane Pressure (TMP) and the solution conductivity were monitored, and the Normalized permeation Flux (m) at 25 ℃ and a transmembrane Pressure (0.75 MPa) corrected for the solution permeation Pressure was calculated³/m²Day (day)).

In the RO system of fig. 3, the concentrated sampled water in the tank 20 is supplied as feed water to a tank (vessel)33 of an RO unit 32 via a pump 30 and a pipe 31. Inside the vessel 33, a primary chamber 35 and a secondary chamber 36 are divided by an RO membrane 34 comprising a flat membrane (flat membrane). The container 33 is disposed in a water bath (water bath)37 including a circulation pump 38 and a heater (heater) 39. In the primary chamber 35, stirring is performed by a magnetic stirrer 40. The non-permeated water (concentrated water) flowing through the primary chamber 35 flows into the concentrated water tank 44 through the pipe 41, the constant pressure valve 42, and the conductivity meter 43. The concentrated water tank 44 is provided in a weight measuring device 45, and measures the amount of concentrated water flowing into the concentrated water tank 44, and data thereof is recorded in a recorder (logger) 46.

The permeated water in the secondary chamber 36 permeated through the RO membrane 34 flows into the permeated water tank 52 through the pipe 50 and the conductivity meter 51. The permeated water tank 52 is provided in the weight measuring instrument 53, and the amount of permeated water flowing into the permeated water tank 52 is measured and the data thereof is recorded in the recorder 54.

The

pipes

31 and 50 are provided with

pressure sensors

60 and 61, and water pressure data is recorded in a recorder 62.

The results of analyzing the water quality of the water sample, the NF membrane concentrated water and the permeate of fig. 2, and the RO membrane permeate and the concentrated water of fig. 3 are shown in table 1. In table 1, the rejection rates (reject rates) of the NF and RO membranes are shown.

[ Table 1]

Item	Unit of	Water sample	NF concentrated water	NF permeating water	Retention rate	RO permeate water	RO concentrated water
								pH	(at 25 ℃ C.)	7.8	8.3	8.4	-	7.3	8.8
EC	μS/cm	1439	1836	945	42	39	2992
								M-al	mgCaCO₃/L	175	196	152	18	10	481
Ca-H	mgCaCO₃/L	178	283	81	65	3	265
								Mg-H	mgCaCO₃/L	82	130	35	67	1	114
Cl	mg/L	170	165	170	-1	10	538
								SiO₂	mg/L	54.8	58.7	50.6	11	3	160
O-PO₄	mg/L	5.6	10.4	1.0	88	<0.1	3.4
								T-PO₄	mg/L	8.3	15.3	1.2	90	<0.1	3.9
Zinc	mg/L	1.3	2.21	0.22	87	<0.1	0.7
								Polymer and method of making same	mg/L	22	45	<5	100	<5	<5
Sulfate ion	mg/L	195	375	22	92	<1	75
								Turbidity of water	NTU	1.1	1.9	<0.5	100	<0.5	<0.5
TDS	mg/L	1007	1285	662	30	27	2095
								TOC	mg/L	11.3	19.2	1.5	90	<1	4.9
BOD	mg/L	<20	<20	<20	-	<20	<20
								COD	mg/L	40	60	15	70	<5	50

< investigation >)

In the water treatment of cooling water, calcium hardness, zinc, phosphate ions or phosphonic acid, polymers, etc., which are important for corrosion prevention or scale prevention, are trapped at a high rate of 65% to 100% by the treatment of the NF membrane module 23 of fig. 2. On the other hand, the NF membrane rejection rate (rejection rate) of chloride ions or silicon oxide, which are factors of corrosion or scale, is as low as-1% to 11%, and passes through the NF membrane.

In the RO system of fig. 3, the organic components causing clogging of the RO membrane have been mostly removed by the RO membrane treatment. The transition in normalized permeation amount is shown in fig. 5 as the result of the evaluation test of the RO membrane of the flat sheet membrane test. The RO membrane was stable in permeation amount, and clogging due to contamination with scale, organic matter, or the like was not observed. From the above results, it is considered that the unwanted ions are concentrated by the RO membrane and stably discharged to the outside of the system.

As shown in table 1, the chemical components (Zn, T-PO4, Polymer (Polymer), etc.) and organic substances hardly permeate the NF membrane and are recycled in the system, so that the amount of the chemical used is reduced, and the concentrations of Zn, P, and BOD in the RO concentrated water are reduced (Zn 0.7, P1.3, BOD 20). Therefore, the environmental load can be reduced, and the water can be drained without the need for a supplementary treatment.

Comparative example 1

< Experimental conditions >

In the same manner as in example 1, the actual cooling water was sampled, and as shown in fig. 4, all the amounts were filtered under an inlet pressure of 0.25MPa to 0.3MPa by an MF membrane (Kuraray) with a pore size of 0.02 μm made of Polyvinylidene Fluoride (PVDF). In fig. 4, a sample water in a tank 70 flows in the order of a pump 71, a pipe 72, an NF membrane module 73, and a pipe 74, and is introduced into a filtered water tank 75, and the amount of water is measured by a weight measuring instrument 76. A part of the discharged water of the pump 71 is returned to the reservoir 70 through the pipe 77.

Test water A containing 10mg/L of scale inhibitor (Kuriver N-500, manufactured by Takeda industries, Ltd.) and test water B containing 3.4mL/L of sulfuric acid (1N) and having a pH value (pH) adjusted to 5.6 were prepared.

The RO system shown in FIG. 3 (the RO membrane is the same as the above-mentioned one) was used to fix the permeated water at a permeated water recovery rate of 70%, a permeated water recovery rate of 30 ℃ and the same permeation rate of the detected water A and the detected water BThe operation was carried out under the condition of excess water, the TransMembrane Pressure (TMP) and the solution conductivity were monitored, and the normalized permeation quantity (m) at 25 ℃ and an TransMembrane Pressure of 0.75MPa after the solution osmotic Pressure correction was calculated³/m²Day (day)).

< results and investigation >

The results of water quality analysis using test water a and the results of observation of the transition of Normalized permeation Flux (Normalized Flux) of the flat membrane test apparatus are shown in table 2 and fig. 6, respectively. The results of water quality analysis using the test water B and the results of observation of the transition of the normalized permeation amount of the flat membrane test apparatus are shown in table 3 and fig. 7, respectively.

[ Table 2]

Item	Unit of	Detection of Water A	MF permeate water	Retention rate	RO permeate water	RO concentrated water
							pH	(at 25 ℃ C.)	7.8	7.8	-	7.1	8.9
EC	μS/cm	1439	1435	0	34	3444
							M-al	mgCaCO₃/L	175	170	3	20	408
Ca-H	mgCaCO₃/L	178	175	2	3	443
							Mg-H	mgCaCO₃/L	82	78	5	1	198
Cl	mg/L	170	170	0	12	417
							SiO₂	mg/L	54.8	55	0	1	135
O-PO₄	mg/L	5.6	5.5	2	<0.1	14
							T-PO₄	mg/L	8.3	8.2	1	<0.1	22
Zinc	mg/L	1.3	1.2	8	<0.1	3.0
							Polymer and method of making same	mg/L	22	21	5	<5	54
Sulfate ion	mg/L	195	195	0	<1	510
							Turbidity of water	NTU	1.1	<0.5	100	<0.5	<0.5
TDS	mg/L	1007	1005	0	24	2411
							TOC	mg/L	11.3	11.1	1	<1	27
BOD	mg/L	<20	<20	-	<20	<20
							COD	mg/L	40	40	0	<5	98

[ Table 3]

As shown in table 2 and fig. 5, since the test water a containing only the scale inhibitor in the MF membrane permeated water had a high calcium concentration and a large amount of organic matter remained, even when the MF treatment and the RO treatment were performed by adding the scale inhibitor, the clogging tendency of the clear Normalized permeation Flux (Normalized Flux) in the RO membrane was confirmed. In the case of the detection water B of which pH was adjusted by sulfuric acid, no scale tended to occur, and therefore, no decrease in Flux was observed, and stable operation was possible.

The pH adjustment by sulfuric acid is effective for stabilizing the operation of the RO membrane, but is performed for 1m³The sample of (2) is treated as 90% sulfuric acid, 185g, for example, 10m per hour³The apparatus (3) consumes more than 1300kg per month on average, and therefore, the management of the storage tank or the storage place becomes a problem.

Further, since the concentrated water of RO contains chemical components (zinc, phosphoric acid, polymer, etc.), it is difficult to satisfy the discharge destination standard, and it is necessary to consider the replenishment, discharge of industrial waste, reduction of recovery rate, and the like.

The present invention has been described in detail with reference to the specific embodiments, but it should be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

The present application is based on japanese patent application 2018-046832, filed 3, 14, 2018, which is incorporated by reference in its entirety.

Description of reference numerals

1: water system

4: NF device

9: and (4) an RO device.

Claims

1. A water treatment device comprising:

a selectively permeable membrane device which receives water from a water system and performs a permeation treatment, and which is provided with a selectively permeable membrane that is impermeable to a useful component;

the deionization device is used for carrying out deionization treatment on the permeation water of the selective permeation membrane device; and

means for returning the non-permeate water of the permselective membrane device and the deionized water of the deionization unit to the water system.

2. The water treatment apparatus as claimed in claim 1, wherein water of the water system contains at least one of a rust inhibitor, a scale inhibitor and a slime inhibitor.

3. A water treatment apparatus as claimed in claim 1 or 2, wherein the water system is a cooling water system, a water treatment apparatus or a makeup water system for supplying makeup water to a water treatment apparatus.

4. The water treatment apparatus according to any one of claims 1 to 3, wherein the permselective membrane is a nanofiltration membrane, and the deionization apparatus is a reverse osmosis apparatus or an electrodeionization apparatus.