# Patent

## Title
Split flow EDI apparatus for treating second pass RO permeate water with high flow rate

## Abstract

We report an electro-deionization (EDI) device having split flow arrangement for the purification of second pass RO permeate water with high flow rate in which the feed water is fed through the center port and is diverted into each section of dilute chamber with equal flow rate, producing two product streams. The EDI device has concentrate chambers adjacent to dilute chambers in two sections of the stack, allowing independent flow through the separate sections. The split flow design reduces resin bed depth requirement for processing of second pass RO permeate water. This results in higher flow rate through the stack, elimination of the pressure drop limitation, and reduction of power consumption per unit volume of water.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to U.S. Provisional Patent Application No. 61/428,413, filed on Dec. 30, 2010, and to Indian Patent Application No. 2384/DEL/2010, filed on Oct. 4, 2010. Both of those applications are incorporated by reference as if fully rewritten herein.


BACKGROUND OF THE INVENTION
1. Field of the Invention
Embodiments of the invention relate to electro-deionization methods and apparatus.
2. Background of the Related Art
An Electro-Deionization apparatus (EDI) is a device that removes the dissolved impurities of reverse osmosis (“RO”) permeate water with the help of resin media, ion exchange membrane and DC current. The EDI process is a continuous process as it does not need chemicals such as acid and caustic for regeneration of resin media and membranes. The resin media is regenerated during the purification of water due to continuous water splitting occurring inside the EDI apparatus. Splitting of H+ and OH− ions happens due to the electric potential generated within the dilute compartment from the H2O molecules which regenerates the corresponding resin ions continuously.
An EDI apparatus is generally used for the purification of reverse osmosis permeate water up to a level of 0.055 μS/cm conductivity and makes it suitable for various industrial applications including but not limited to boiler feed/steam generation, microelectronics/semiconductor makeup or rinse water, and purified USP grade water.
An EDI apparatus is typically made up of ion exchange resin, ion exchange membranes, electrodes for DC supply and hardware components for water flow distribution. The arrangement of ion exchange membranes, anion exchange membranes and cation exchange membrane, are very important in an EDI apparatus. They are generally arranged in alternate manner with respect to anode and cathode electrodes. The ion exchange resin media are filled in the chambers/compartments which are formed due the arrangement of anion and cation exchange membranes. This leads to the formation of dilute chambers and concentrate chambers.
The dilute chambers are those in which the feed water (RO permeate) gets purified and become ultra pure water whereas the concentrate chambers are adjacent alternate positioned to dilute in which the removed ions from the dilute chambers are collected and flushed out from the apparatus with the help of separate water stream. A small portion of the water is also used for flushing and cooling the cathode and anode electrodes, called Electrode Rinse stream and the chamber is called the Electrode Rinse Chamber.
The efficiency and commercial utilization of any EDI apparatus depends upon the quantity of product water produced per unit area of membrane, per unit volume of ion exchange media or per cell pair of membranes. There are many commercial EDI apparatus are available in market which can be easily divided into three categories—
1) Low Flow Rate EDI Apparatus:
This type of EDI apparatus are generally thin cell plate and frame EDI having product flow rate range of 1.5 m3/hr and 2.0 m3/hr with 30 or more cell pair. The output product flow of each dilute chamber is generally in the range of 50 to 60 LPH or less.
2) Medium Flow Rate EDI Apparatus:
The second category EDI apparatus are generally thick cell plate and frame EDI having product flow rate of 2.5 m3/hr-5.0 m3/hr with 30 cell pair or more. The output product flow of each dilute chamber is generally in the range of 80 to 170 LPH or less.
In both the first and the second category the pressure drop across dilute chamber (feed to product) is typically around 20 to 30 psi for nominal flow rate. For maximum flow rate it typically increases up to 40-60 psi. The effective length of dilute chambers of such EDI apparatus vary from 350 mm to 450 mm and width vary from 100 mm to 200 mm. The resin volume inside the dilute chambers of these EDI apparatus does not allow increase in the flow rate due to high pressure drops, mechanical leaks or mechanical strength of the apparatus.
The typical flow configuration of both category EDI apparatus is shown in FIG. 1. A third category of EDI apparatus is also used.
3) High Flow EDI Apparatus:
To achieve high product flow rate, more than 5.0 m3/hr, a third category of EDI apparatus is also used, which is generally the combination of multiple EDI apparatus, connected together in parallel with 40 to 60 number of cell pairs per unit, for producing high product flow rate from the stacks. The product flow rate per dilute chamber of this type EDI apparatus is similar to medium flow rate EDI apparatus. The high product flow through these EDI apparatus is only due to the increased area of dilute chambers.
For the production of ultra pure water, an EDI apparatus generally is used to purify either permeate water of single pass RO, where the feed ion load is high with challenging scaling ions, or permeate water of second pass RO permeate, where the feed ions load are very less with negligible amount of scaling ions.
The scaling ions (like Ca2+, Mg2+, CO3, SiO2, etc) have big role to play in any EDI operation and have been the cause for limiting conditions requiring additional pretreatment that may be uneconomical in many cases. Some solutions to this problem have been proposed. For example, the fractional deionization process reported in U.S. Pat. No. 6,896,814, incorporated by reference herein, uses a dual voltage process for the removal of higher load of scaling ions without scaling in EDI apparatus.
EDI design for certain flow depends upon the feed condition and the product quality requirement. For harsher feed condition such as single pass RO permeate water with challenging scaling ions, the product flow is typically reduced. This makes the system costly and therefore unattractive for use.
The typical product flow rate of an EDI apparatus at different feed hardness (as CaCO3) and feed conductivity equivalent (FCE) loads are summarized as,

    
    
        a. Product flow rate=2.4 m3/hr when feed hardness (as CaCO3) is 3 ppm and total FCE load is 25-30 μS/cm for the product quality requirement of more than 10 to 16 MOhms
        b. Product flow rate=3.5 m3/hr when feed hardness (as CaCO3) is 1 ppm and total FCE load is 15-20 μS/cm for the product quality requirement of more than 10 to 16 MOhms
        c. Product flow rate=4.5 m3/hr when feed hardness (as CaCO3) is 0.1 ppm and total FCE load is <10 μS/cm for the product quality requirement of more than 10 to 16 MOhms
    
    


When the feed hardness (as CaCO3) is less than 0.1 ppm like in second pass RO permeate water, the EDI behavior is quite different. Scaling is not a major concern, and the rate of effective in-situ media regeneration is the main criterion to govern the process and higher product quality can be easily achievable even with high flow rate but the main limitation is the higher pressure drop across the dilute chamber in regular flow mode.
The previously mentioned fractional deionization process of U.S. Pat. No. 6,896,814 B2 is a two stage process that deals with hardness and silica removal in separate zones because of their different current requirement. The design of an apparatus for this reason has two stages and is able to produce product flow rate up to 5.0 m3/hr with its regular flow mode. This process/apparatus when used for double pass RO grade water with novel split flow design is able to treat as high as 8 to 10 m3/hr of product water against normally product flow rate which is 3 to 5 m3/hr. Single stack with 8 to 10 m3/hr reduces the line connections, minimize pressure drop across dilute chamber, reduce power consumption per unit volume of water and makes a economical and viable proposition for the user.
BRIEF SUMMARY OF THE INVENTION
To attempt to overcome the limitation of high pressure drop, more cell pair or increased unit area for high flow rate and mechanical leaks through EDI apparatus, we provide the unique EDI apparatus design reported herein. Embodiments of the invention may overcome one or more of the limitations, and may be capable of producing high product flow rate in the ranges of 5.0 m3/hr to 10.0 m3/hr for treating 2nd pass RO permeate water to produced ultra pure level, more than 1.0 MOhms/cm product (generally 10 to 16 MOhms·cm product water) with only 30-35 cell pairs. The output product flow rate through each dilute camber of embodiments of this new EDI apparatus is 150 to 280 LPH which is almost double of the conventional EDI apparatus. The design of the new EDI apparatus has the flexibility to operate in conventional mode if single pass RO permeate water is provided as feedwater.



BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 shows the flow configuration of a conventional EDI apparatus.
FIG. 2 shows a schematic view of a split-flow EDI apparatus according to an embodiment of the invention.
FIG. 3 shows an exemplary embodiment of a dilute spacer including dimensions suitable for use in an embodiment of the invention.
FIG. 4 shows a new design of a dilute chamber of the invention.
FIG. 5 shows an embodiment of a concentrate chamber of the invention.
FIG. 6 shows a spacer of the invention with an emphasis on the middle rib at A.
FIG. 7 shows an EDI assembly according to one embodiment of the invention.
FIG. 8 shows flow configuration of an embodiment of the new EDI dilute spacer for single pass RO permeate water.
FIG. 9 shows product resistivity for one example of an embodiment of the invention.
FIG. 10 shows Graph 2, which is a product quality diagram for a 30-cell-pair embodiment of the invention reported in Example 3.
FIG. 11 shows Graph 3, which is a product quality diagram for a 35-cell-pair embodiment of the invention reported in Example 3.



DETAILED DESCRIPTION OF THE INVENTION
An EDI apparatus provided by an embodiment of the invention generally comprises the following main components—

    
    
        Dilute chambers (typically 30-35 in number)
        Concentrate chambers (typically 31-36 in number)
        Electrode chambers (02 in number) which contains anode and cathode electrodes
        Metal End plates (02 in numbers)
        Outer covers.
    
    


In most of the cases the single pass RO permeate used as feed water contains Feed conductivity equivalent (FCE) ranges between 10 and 40 μS/cm with high scaling ions like Calcium, Magnesium, bicarbonates, silica and CO2, whereas the 2nd pass RO feed water generally contains less than 10 μS/cm FCE, with negligible amounts of CO2 and silica. For treating such 2nd pass RO permeate water a minimum resin bed length is sufficient for producing more than 10 Megaohms/cm ultra pure water.
Based on this finding a new split flow EDI apparatus has been designed which has two sections (sections 1 & 2, as shown in FIG. 3). The total length of spacer is designed to 550 mm with an effective resin bed length of 200-220 mm, preferably 210 mm in each section, and the total width of spacer is designed to 300 mm with effective resin bed width of 200 mm in each section. The thickness of dilute chamber is 11 mm with net volume of 396 cm3 and net membrane surface area of 360 cm2 in each section. Of course these dimensions are for an exemplary embodiment and should not be implied to limit the claims.
This allows a stack design embodying a novel split flow EDI concept, wherein one can maximize the flow through the EDI stack by splitting the flow through the stack into two parts.
During operation of a typical embodiment, the feed water is fed through the center port and is diverted into each section of dilute chamber with equal flow rate and produced two products (Product-1 & Product-2, as shown in FIG. 2). The EDI apparatus has similar design concentrate chambers where two separate concentrate streams that flush the removed ions from the dilute chambers.
One unique feature of this concept is flow patterns within the stack. The flow patterns have a combination of up-flow and down flow. The lower part of the stack operates in a down flow mode and the upper part of the stack operates in an up-flow mode. The dilute and concentrate chambers follow similar flow patterns and remain co-flow with each other. Since the water flows happen through half of the stack length, water volume processed can be increased for the same pressure drop, and a similar quantity of water can be processed through the other half.
The split flow design reduces resin bed depth required for processing of second pass RO permeate water. This results in higher flow rate through the stack and reduces power consumption per unit volume of water compared to typical EDI.
For treating 2nd pass RO permeate water, the RO permeate water may be fed through the port N2 (1-inch), shown in FIG. 4, which is then distributed into each section of dilute chamber with equal flow rate and ultimately produces two products (Product-1 & Product-2) which come out from Port N1 and N4 (both 1-inch). Thus each section acts as an independent dilute chamber. Product output flow is doubled over a single-section dilute chamber. The EDI apparatus has concentrate chambers where two separate concentrate streams removed ions from respective dilute chambers. The Electrode Rinse chamber is also designed with a similar configuration having two separate electrodes for each section at each ends. The typical view of dilute spacer and dilute chamber flow configuration of new EDI apparatus is shown in FIG. 3 and FIG. 4 respectively.
Concentrate Chamber:
The concentrate spacer of new EDI apparatus (FIG. 5) contains conducting mesh of 1.0-2.0 mm thick and the total thickness of concentrate chamber is 2.0-3.0 mm including gaskets. The EDI apparatus has two separate concentrate streams for both section 1&2 and the flow is co-current of dilute flow for each section as shown in FIG. 5.
A typical view of a concentrate chamber flow configuration used in an embodiment of our EDI apparatus is shown in FIG. 5
Another special feature of embodiments of our EDI apparatus is a middle solid supporting rib included in the components/spacers. An example of a rib is shown as Part A of FIG. 6. The ribs play an important role and have following features:

    
    
        Separate and differentiate the two sections and accommodate two sections in a lesser foot print.
        Provide an ability to install inlet and flow distribution nozzles to split flows between two sections.
        Provide mechanical strength to the components/spacers, and
        Prevent the components/spacers from bulging which generally observed in conventional EDI spacer if length would be larger due the resin compression pressure in dilute chambers.

New EDI Apparatus Assembly:

    
    


An embodiment of the new EDI apparatus may be assembled in the following manner, with a typical assembly shown in FIG. 7:
The cathode chamber is formed by placing anion membranes in each section of Electrode housing plate (EHP) which contains two cathodes and cation resin media in each section. The cathodes may be, for example, SS-316 cathodes.
Then a concentrate chamber is formed by placing concentrate spacer (CS) over anion membranes of cathode chamber. The concentrate spacer contains conducting mesh in each section.
The dilute chambers is formed by placing cation membranes on each section of new design dilute spacer facing towards cathode and by placing anion membranes on each section of dilute spacer facing towards anode. The resin media is accommodated in each section of dilute spacer between two membranes.
The another adjacent concentrate chambers are formed placing concentrate spacer in which the anion membrane of each section faces towards the cathode side and the cation membrane faces towards the anode side.
One dilute chamber and one concentrate chamber forms one cell pair. Typically 30-35 cell pair of dilute and concentrate chambers are assembled.
An anode chamber is formed after last concentrate chamber by placing an electrode housing plate (EHP) which contains two titanium anodes and cation resin media in each section.
Finally the whole 30-35 cell pair of dilute and concentrate chambers and two electrode chambers are tighten by two end plate (EP), one at each end, with the help of stainless steel (SS) studs.
Spacers may be separated by rings, preferably EPDM (ethylene propylene diene monomer) to prevent leakage of water during operation.
Description of New Design EDI Apparatus for Treating Single Pass RO Permeate Water:
Embodiments of the new EDI apparatus design have the flexibility to operate for higher conducting (more than 10 μS/cm) RO permeate water (single pass RO) in the alternative to second-pass RO permeate water. In case of single pass RO, the permeate water is fed from the port N1 (typically a 1-inch port) and the section-1 product (D1) entered in section-2 from port N3 as Port N2 and N3 has interconnectivity and finally the purified product comes out from port N4. Two separate concentrate streams also flow in adjacent concentrate chambers as co-current as shown in FIG. 8
EXAMPLES
A series of trials were conducted on new design EDI apparatus with 30-35 cell pair configuration.
Comparative Example-1
Conventional Mode
A 30-cell pair stack was assembled and tested with regular flow mode with feed at the bottom and product at the top. The stack tested for 71 hrs with product flow of 3.5 m3/hr to 5.0 m3/hr flow with feed FCE of 10 μS/cm. The stack configuration was: —

    
    
        Dilute chambers—30 nos with resin media
        Concentrate chambers—31 nos with conducting mesh
        Electrode chambers—O2 nos.
        End plates—O2 number
        Electrode: anode—Titanium and Cathode—SS-316
        Membrane: Heterogeneous Ion exchange membranes
        Effective Membrane area of dilute chamber—4.32 m2
    
    


The product quality of stack was more than 16 MegaOhms·cm with higher pressure dilute drop. At 3.5 m3/hr product flow, dilute pressure drop was 27 psi, at 4.0 m3/hr it was 34 psi, at 4.5 psi it was increased to 43 psi and at maximum 5.0 m3/hr it reached up to 50 psi. The feed temperature was around 25° C. The summarized data of comparative stack are in table-1:







TABLE 1





Comparative example stack data:
























Stack
Feed

Dilute
Product
Product
Section-1

















Op.
FCE
Feed
ΔP
Flow
Resistivity
Voltage
Current



Hrs
μS/cm
pH
psi
LPH
M-ohms · cm
VDC
amps







11
10.4
6.2
27
3500
15.71
250
1.2



20
9.7
6.7
27
3500
17.08
250
1.2



30
10.3
6.6
27
3500
16.75
250
1.3



40
9.7
6.7
27
3500
17.45
250
1.3



50
9.5
6.6
27
3500
17.63
250
1.4



55
9.8
6.6
27
3500
17.61
250
1.4



57
10.5
6.5
34
4000
17.35
250
1.5



58
10.9
6.5
34
4000
17.25
250
1.6



59
10.8
6.5
34
4000
17.00
250
1.6



60
8.9
6.6
34
4000
17.00
250
1.6



61
9.5
6.6
34
4000
17.10
250
1.6



62
9.5
6.6
34
4000
17.25
250
1.6



63
10.1
6.6
34
4000
17.20
250
1.6



64
9.1
6.6
43
4500
16.68
250
1.6



65
10.5
6.5
43
4500
16.59
250
1.5



66
10.9
6.4
43
4500
16.70
250
1.5



67
10.5
6.5
43
4500
16.50
250
1.5



68
9.0
6.5
50
5000
16.20
250
1.5



69
10.5
6.4
50
5000
16.10
250
1.4



70
10.2
6.3
50
5000
16.15
250
1.4



71
10.3
6.5
50
5000
16.10
250
1.6




















Stack
Feed

Dilute
Product
Product
Section-2
C1(OUT)
C2(OUT)
E.Rinse

















Op.
FCE
Feed
ΔP
Flow
Resistivity
Voltage
Current
Flow
flow
Flow


Hrs
μS/cm
pH
psi
LPH
M-ohms · cm
VDC
amps
LPH
LPH
LPH





11
10.4
6.2
27
3500
15.71
350
2.5
250
250
100


20
9.7
6.7
27
3500
17.08
350
2.7
250
250
100


30
10.3
6.6
27
3500
16.75
350
2.5
250
250
100


40
9.7
6.7
27
3500
17.45
350
2.5
250
250
100


50
9.5
6.6
27
3500
17.63
350
2.8
250
250
100


55
9.8
6.6
27
3500
17.61
350
3.0
250
250
100


57
10.5
6.5
34
4000
17.35
350
2.9
250
250
100


58
10.9
6.5
34
4000
17.25
350
2.9
250
250
100


59
10.8
6.5
34
4000
17.00
350
2.9
250
250
100


60
8.9
6.6
34
4000
17.00
350
2.9
250
250
100


61
9.5
6.6
34
4000
17.10
350
2.9
250
250
100


62
9.5
6.6
34
4000
17.25
350
2.8
250
250
100


63
10.1
6.6
34
4000
17.20
350
3.0
250
250
100


64
9.1
6.6
43
4500
16.68
350
2.9
250
250
100


65
10.5
6.5
43
4500
16.59
350
2.9
250
250
100


66
10.9
6.4
43
4500
16.70
350
2.8
250
250
100


67
10.5
6.5
43
4500
16.50
350
2.8
250
250
100


68
9.0
6.5
50
5000
16.20
350
2.8
250
250
100


69
10.5
6.4
50
5000
16.10
350
2.8
250
250
100


70
10.2
6.3
50
5000
16.15
350
2.8
250
250
100


71
10.3
6.5
50
5000
16.10
350
2.7
250
250
100









Example 2
One new split flow design EDI apparatus with 30-cell pair was assembled with the following components:

    
    
        Dilute chambers—30 in number with resin media
        Concentrate chambers—31 in number with conducting mesh
        Electrode chambers—O2 in number
        End plates—O2 in number
        Electrode: anode—Titanium and Cathode—SS-316
        Membrane: Heterogeneous Ion exchange membranes
        Effective Membrane area of dilute chamber—4.32 m2
    
    


The EDI apparatus has been tested for following product flow rate and feed FCE load

    
    
        A—Product flow rate*=5.0 m3/hr (5000 LPH) with feed FCE of 9 to 10 (table-1)
        B—Product Flow rate*=6.0 m3/hr (6000 Lph) with Feed FCE of 1.0 to 10 (table-2)
        C—Product flow rate*=7.0 m/hr (7000 Lph) with Feed FCE of 1.0 to 10 (table-3)

Note: * product Flow Rate=Product-1 flow+product-2 flow)

    
    


The stack product quality in above three flow conditions is always more than 10 MOhms·cm. The applied current is maintained in between 2.0 amps and 3.0 amps in each section (section-1 & 2). The product silica quality is always around 10 ppb from feed silica of 50 ppb to 100 ppb.
The stack data of above conditions are summarized in table-2 to table-4.







TABLE 2





(stack Quality with 5.0 m3/hr (5000 LPH) product flow rate)






















FEED


Product
Product
Voltage



FCE
FEED
ΔP
Flow
Resistivity
section-1



μS/cm
pH
psi
LPH
Mohms · cm
VDC







 9.1
7.2
18
5000
13.91
334



 9.2
6.7
18
5000
13.90
330



 9.3
6.7
18
5000
13.93
330



 9.4
7.0
18
5000
12.70
326



 9.5
6.9
18
5000
12.48
326



 9.6
6.8
18
5000
12.35
327



 9.8
6.6
16
5000
12.97
337



 9.9
6.7
16
5000
12.49
328



 9.9
6.9
16
5000
12.35
327



10.1
6.7
18
5000
11.80
325



10.2
6.8
18
5000
12.22
330



10.3
6.9
16
5000
12.11
326



10.5
6.8
16
5000
12.05
326



10.7
6.8
18
5000
12.20
330




















FEED


Product
Product
Current
C1(OUT)
C2(OUT)
Feed
Product


FCE
FEED
ΔP
Flow
Resistivity
A-2
Flow
Flow
Silica
Silica


μS/cm
pH
psi
LPH
Mohms · cm
ADC
LPH
LPH
Ppb
ppb





9.1
7.2
18
5000
13.91
3.00
200
200


9.2
6.7
18
5000
13.90
2.98
200
200


9.3
6.7
18
5000
13.93
3.00
200
200
79
11


9.4
7.0
18
5000
12.70
2.99
200
200


9.5
6.9
18
5000
12.48
2.99
200
200
83
10


9.6
6.8
18
5000
12.35
2.99
200
200


9.8
6.6
16
5000
12.97
3.00
200
200


9.9
6.7
16
5000
12.49
3.00
200
200
84
9


9.9
6.9
16
5000
12.35
2.99
200
200
98
11


10.1
6.7
18
5000
11.80
3.00
200
200


10.2
6.8
18
5000
12.22
2.99
200
200
81
9


10.3
6.9
16
5000
12.11
2.99
200
200


10.5
6.8
16
5000
12.05
2.99
200
200


10.7
6.8
18
5000
12.20
2.98
200
200
















TABLE 3





Stack Quality with 6.0 m3/hr (6000 LPH) Product Flow Rate





















FEED


Product
Product
Voltage
Current


FCE
FEED
ΔP
Flow
Resistivity
section-1
section-1


μS/cm
pH
psi
LPH
Mohms · cm
Vdc
Amps





0.9
5.9
25
6000
17.56
270
2.01


1.2
6.6
24
6000
17.45
257
2.01


1.3
6.6
26
6000
17.20
257
2.03


1.4
6.4
25
6000
17.20
281
2.05


1.5
6.3
26
6000
17.15
258
2.03


1.6
6.4
25
6000
16.67
266
2.01


1.7
6.4
26
6000
17.10
263
2.00


1.7
6.5
26
6000
17.36
258
2.04


1.7
6.1
25
6000
16.75
266
2.02


1.8
6.3
25
6000
16.34
266
2.02


1.9
6.5
26
6000
17.33
260
2.04


2.0
6.2
25
6000
16.47
265
2.07


2.1
6.8
26
6000
16.95
258
2.03


2.2
6.3
25
6000
16.46
271
2.07


2.8
6.4
26
6000
17.09
256
2.03


3.6
6.1
27
6000
16.02
315
2.01


3.6
6.1
28
6000
16.92
334
2.03


3.7
6.0
27
6000
16.92
337
2.01


3.8
6.3
25
6000
15.93
301
2.04


3.8
6.2
27
6000
16.94
348
2.01


3.8
6.2
27
6000
17.09
327
1.98


3.9
6.3
28
6000
16.69
327
2.00


4.0
6.2
27
6000
16.02
307
2.02


4.0
6.3
26
6000
16.52
319
1.99


4.0
6.2
26
6000
16.68
326
1.99


4.0
6.5
26
6000
16.78
320
1.99


4.0
6.4
27
6000
16.89
334
2.00


4.0
6.3
27
6000
16.89
318
2.03


4.0
6.9
28
6000
16.20
340
2.02


4.1
6.4
26
6000
16.72
320
1.99


4.2
6.4
26
6000
16.42
312
2.00


4.3
6.5
26
6000
16.69
320
1.99


4.4
6.5
27
6000
16.34
323
2.05


4.5
6.5
27
6000
16.42
330
2.02


4.6
6.5
27
6000
16.86
349
2.02


4.7
6.4
28
6000
16.51
333
2.01


4.8
6.2
25
6000
15.59
289
2.01


4.9
6.4
28
6000
15.88
334
2.01


5.0
6.4
28
6000
16.83
325
2.03


5.0
6.3
28
6000
16.05
321
2.02


5.0
6.5
28
6000
16.36
338
2.01


5.0
6.4
28
6000
15.90
332
2.01


5.0
6.4
28
6000
16.19
333
2.02


5.1
6.4
28
6000
16.09
323
2.01


5.1
6.4
28
6000
16.06
325
2.01


5.1
6.3
28
6000
16.29
332
2.01


5.2
6.4
28
6000
15.78
334
2.03


5.3
6.5
24
6000
14.35
283
2.50


5.4
6.8
24
6000
14.55
283
2.51


5.4
6.8
24
6000
14.38
286
2.50


5.6
6.7
24
6000
14.54
282
2.52


5.8
6.9
24
6000
14.92
280
2.50


5.9
6.3
27
6000
15.74
366
2.50


6.0
6.3
27
6000
15.75
358
2.53


6.0
6.6
27
6000
15.57
361
2.51


6.4
7.6
29
6000
16.94
366
2.52


6.9
7.0
28
6000
15.86
358
2.51


7.0
7.0
28
6000
16.50
371
2.51


8.0
7.0
30
6000
16.18
370
2.51


8.4
7.5
29
6000
16.38
370
2.53


8.5
7.7
30
6000
15.82
364
2.53


8.9
6.8
24
6000
11.25
324
2.98


9.0
7.3
30
6000
11.10
368
2.52


9.1
6.6
24
6000
11.50
329
2.98


9.2
6.6
24
6000
11.35
328
3.00


9.6
6.7
24
6000
11.09
334
3.00




















FEED


Product
Product
Voltage
Current
C1(OUT)
C2(OUT)
FEED
Product


FCE
FEED
ΔP
Flow
Resistivity
section-2
section-2
Flow
flow
Silica
Silica


μS/cm
pH
psi
LPH
Mohms · cm
Vdc
amps
LPH
LPH
ppb
ppb





0.9
5.9
25
6000
17.56
278
2.03
200
200


1.2
6.6
24
6000
17.45
260
2.00
200
200
44
9


1.3
6.6
26
6000
17.20
260
2.03
200
200


1.4
6.4
25
6000
17.20
283
2.03
200
200
37
8


1.5
6.3
26
6000
17.15
259
2.02
200
200


1.6
6.4
25
6000
16.67
270
2.02
200
200
180
12


1.7
6.4
26
6000
17.10
265
2.02
200
200
38
10


1.7
6.5
26
6000
17.36
260
2.03
200
200
36
5


1.7
6.1
25
6000
16.75
263
2.01
200
200
76
11


1.8
6.3
25
6000
16.34
263
2.01
200
200
160
15


1.9
6.5
26
6000
17.33
260
2.03
200
200
38
10


2.0
6.2
25
6000
16.47
261
2.02
200
200


2.1
6.8
26
6000
16.95
259
2.04
200
200


2.2
6.3
25
6000
16.46
267
2.01
200
200
57
9


2.8
6.4
26
6000
17.09
258
2.03
200
200
34
7


3.6
6.1
27
6000
16.02
359
2.02
250
250


3.6
6.1
28
6000
16.92
369
2.02
250
250
35
9


3.7
6.0
27
6000
16.92
373
2.03
250
250
27
8


3.8
6.3
25
6000
15.93
346
2.04
250
250
34
8


3.8
6.2
27
6000
16.94
379
2.00
250
250
30
8


3.8
6.2
27
6000
17.09
362
1.99
250
250
37
9


3.9
6.3
28
6000
16.69
365
2.00
250
250
47
9


4.0
6.2
27
6000
16.02
350
2.03
250
250


4.0
6.3
26
6000
16.52
359
2.00
250
250
41
9


4.0
6.2
26
6000
16.68
366
1.98
250
250
29
8


4.0
6.5
26
6000
16.78
358
2.01
250
250
33
10


4.0
6.4
27
6000
16.89
370
2.01
250
250
40
8


4.0
6.3
27
6000
16.89
337
2.02
250
250
54
14


4.0
6.9
28
6000
16.20
365
2.05
250
250
60
11


4.1
6.4
26
6000
16.72
359
2.00
250
250


4.2
6.4
26
6000
16.42
352
2.01
250
250


4.3
6.5
26
6000
16.69
358
2.01
250
250


4.4
6.5
27
6000
16.34
346
2.03
250
250
101
13


4.5
6.5
27
6000
16.42
356
2.02
250
250


4.6
6.5
27
6000
16.86
378
2.02
250
250
108
13


4.7
6.4
28
6000
16.51
357
2.01
250
250


4.8
6.2
25
6000
15.59
290
2.00
200
200
43
8


4.9
6.4
28
6000
15.88
358
2.0
250
250
69
13


5.0
6.4
28
6000
16.83
350
2.02
250
250
44
10


5.0
6.3
28
6000
16.05
345
2.02
250
250
75
12


5.0
6.5
28
6000
16.36
360
2.01
250
250
79
14


5.0
6.4
28
6000
15.90
357
2.03
250
250
65
13


5.0
6.4
28
6000
16.19
354
2.01
250
250
66
14


5.1
6.4
28
6000
16.09
347
2.01
250
250
71
13


5.1
6.4
28
6000
16.06
349
2.01
250
250
61
13


5.1
6.3
28
6000
16.29
357
2.01
250
250
49
12


5.2
6.4
28
6000
15.78
355
2.02
250
250
66
13


5.3
6.5
24
6000
14.35
286
2.50
150
150
46
11


5.4
6.8
24
6000
14.55
288
2.52
150
150
65
11


5.4
6.8
24
6000
14.38
289
2.50
150
150
75
11


5.6
6.7
24
6000
14.54
287
2.51
150
150


5.8
6.9
24
6000
14.92
283
2.50
150
150
71
12


5.9
6.3
27
6000
15.74
386
2.52
250
250
76
14


6.0
6.3
27
6000
15.75
387
2.59
250
250


6.0
6.6
27
6000
15.57
386
2.55
250
250
54
11


6.4
7.6
29
6000
16.94
384
2.52
200
200


6.9
7.0
28
6000
15.86
358
2.58
250
250
79
13


7.0
7.0
28
6000
16.50
387
2.51
250
250


8.0
7.0
30
6000
16.18
383
2.52
200
200
51
12


8.4
7.5
29
6000
16.38
384
2.53
200
200
96
11


8.5
7.7
30
6000
15.82
377
2.51
200
200
84
11


8.9
6.8
24
6000
11.25
331
2.99
200
200


9.0
7.3
30
6000
11.10
381
2.50
200
200
61
13


9.1
6.6
24
6000
11.50
329
3.00
200
200


9.2
6.6
24
6000
11.35
328
3.00
200
200
96
9


9.6
6.7
24
6000
11.09
338
3.00
200
200
















TABLE 4





Stack Quality with 7.0 m3/hr (7000 LPH) Product Flow Rate





















FEED


Product
Product
Voltage
Current


FCE
FEED
ΔP
Flow
Resistivity
Section-1
Section-1


μS/cm
pH
psi
LPH
Mohms · cm
vdc
amps





1.6
7.4
37
7000
17.57
326
1.98


1.7
7.5
37
7000
17.50
360
2.51


1.9
7.2
37
7000
17.52
357
2.58


2.0
7.4
37
7000
17.91
359
2.52


3.5
7.0
35
7000
15.43
375
2.54


5.9
7.7
35
7000
14.56
360
2.66


6.0
7.8
35
7000
15.80
375
2.81


6.1
7.6
35
7000
15.18
360
2.76


6.2
7.5
35
7000
15.13
375
2.93


6.3
6.7
35
7000
15.40
375
2.70


6.3
7.3
35
7000
15.14
360
2.69


6.4
7.3
35
7000
15.86
375
2.93


6.4
7.5
35
7000
14.98
360
2.70


6.9
7.7
35
7000
15.12
360
2.76


7.8
8.2
37
7000
13.75
326
2.07


8.5
6.8
37
7000
14.05
328
2.97


8.7
6.7
37
7000
14.30
322
3.00


8.9
6.9
37
7000
11.30
326
2.98


9.6
6.2
37
7000
13.90
330
2.98


9.8
6.7
35
7000
13.91
334
2.98


10.0
6.6
35
7000
13.80
328
2.97


10.1
6.9
35
7000
13.87
335
2.98


10.1
6.6
35
7000
13.43
329
2.97


10.4
6.6
37
7000
13.98
328
2.99


10.5
6.9
35
7000
14.90
328
3.00


10.9
6.9
35
7000
13.42
317
3.00


11.1
6.9
35
7000
13.71
310
3.00


11.8
6.7
35
7000
13.28
311
3.00




















FEED


Product
Product
Voltage
Current
C1(OUT)
C2(OUT)
Feed
Product


FCE
FEED
ΔP
Flow
Resistivity
Section-2
Section-2
flow
flow
Silica
Silica


μS/cm
pH
psi
LPH
Mohms · cm
vdc
amps
LPH
LPH
ppb
ppb





1.6
7.4
37
7000
17.57
326
1.82
200
200
31
12


1.7
7.5
37
7000
17.50
380
2.51
200
200
26
7


1.9
7.2
37
7000
17.52
370
2.52
200
200


2.0
7.4
37
7000
17.91
372
2.45
200
200


3.5
7.0
35
7000
15.43
375
2.37
200
200


5.9
7.7
35
7000
14.56
360
2.43
200
200
50
14


6.0
7.8
35
7000
15.80
375
2.5
200
200
55
10


6.1
7.6
35
7000
15.18
360
2.49
200
200
73
12


6.2
7.5
35
7000
15.13
375
2.6
200
200
50
12


6.3
6.7
35
7000
15.40
375
2.48
200
200
45
12


6.3
7.3
35
7000
15.14
360
2.44
200
200
70
11


6.4
7.3
35
7000
15.86
375
2.6
200
200
50
12


6.4
7.5
35
7000
14.98
360
2.47
200
200
52
14


6.9
7.7
35
7000
15.12
360
2.51
200
200
54
15


7.8
8.2
37
7000
13.75
326
1.88
200
200
50
12


8.5
6.8
37
7000
14.05
327
2.98
200
200
59
12


8.7
6.7
37
7000
14.30
328
3.00
200
200
61
8


8.9
6.9
37
7000
11.30
326
3.00
200
200
82
10


9.6
6.2
37
7000
13.90
329
2.98
200
200
47
13


9.8
6.7
35
7000
13.91
340
2.99
200
200
82
8


10.0
6.6
35
7000
13.80
331
2.98
200
200
34
12


10.1
6.9
35
7000
13.87
335
2.96
200
200
50
12


10.1
6.6
35
7000
13.43
334
3.00
200
200
61
11


10.4
6.6
37
7000
13.98
331
2.99
200
200
36
10


10.5
6.9
35
7000
14.90
326
2.96
200
200
30
8


10.9
6.9
35
7000
13.42
307
3.00
200
200
72
13


11.1
6.9
35
7000
13.71
291
3.00
200
200
48
14


11.8
6.7
35
7000
13.28
301
3.00
200
200









Product Quality Performance:

The new Split Flow EDI apparatus of example-2 was operated for 742 hours with product flow rate of 5.0 m3/hr to 7.0 m3/hr with 2nd pass RO permeate water having feed FCE load from 1.0 μS/cm to 10.0 μS/cm. The product resistivity of the apparatus remains above 10 MOhms/c·cm (between 11 MOhms·cm to 17.5 Mohsm·cm) which represent graph 1 (FIG. 9).
Example-3
Another New Split Flow EDI apparatus with new design components was assembled first with 30-cell pairs and tested for 587 hours in 5.0 m3/hr to 7.0 m3/hr product flow rate and then 5 more cell pair added to the apparatus to make it 35-cell pair apparatus and continue the testing up to 857 hours with product flow rate of 6.0 m3/hr to 10.0 m3/hr with 2nd pass RO permeate water having less than 10 μS/cm FCE load.
The EDI apparatus configuration of example-3 is

    
    
        Dilute chambers—30-35 nos with resin media
        Concentrate chambers—31-36 nos with conducting mesh.
        Electrode chambers—O2 nos.
        End plates—O2 number
        Electrode: anode—Titanium and Cathode—SS-316
        Membrane: Heterogeneous Ion exchange membranes
        Effective Membrane area of dilute chamber—4.32 m2 (30-cell pair) to 5.04 m2 (35 cell pair)
    
    


The EDI apparatus has been tested for following product flow rate

    
    
        D—Product flow rate*=5.0 m3/hr (5000 LPH) to 7.0 m3/hr (7000 LPH) (table-5)
        E—Product Flow rate*=6.0 m3/hr (6000 LPH) to 10.0 m3/hr (10000 LPH) (table-6)

Note: * Product Flow Rate=(Product-1 flow+product-2 flow)

    
    


The EDI apparatus product quality in above product flow conditions is always more than 10 MOhms·cm (generally 10 MOhms/cm to 17.5 MOhms·cm). The applied current is maintained in between 2.0 amps and 3.0 amps in each section (section-1 & 2). The product silica quality is always less 10 ppb from feed silica of 20 ppb to 50 ppb.
The EDI apparatus data of above conditions are summarized in table-5 and table-6.







TABLE 5





(EDI Apparatus data with 30-cell pair; Quality with 5.0 m3/hr to 7.0 m3/hr Product flow rate)
























Stack
Feed


Product
Product
Voltage
Current



Op.
FCE
Feed
ΔP
Flow
Resistivity
Section-1
Section-1



Hrs.
μS/cm
pH
psi
LPH
Mohms · cm
Vdc
Amps







 11
2.9
6.8
8
6000
15.36
223
2.00



 20
3.1
7.5
8
6000
16.67
227
2.01



 30
5.6
7.5
8
6000
15.90
225
2.01



 40
5.2
7.5
9
6000
15.10
238
2.02



 50
4.6
7.4
9
6000
14.57
248
2.01



 60
4.4
7.5
10
6000
15.10
265
2.01



 70
1.5
6.9
10
6000
16.94
272
2.01



 80
1.6
6.9
10
6000
17.13
261
2.00



 90
7.0
7.4
10
6000
16.41
235
2.01



100
7.3
7.6
10
6000
13.10
274
2.50



110
7.6
7.6
10
6000
12.92
280
2.53



120
7.0
7.5
10
6000
12.58
284
2.52



130
7.6
7.5
10
6000
12.22
280
2.49



140
7.7
7.1
10
6000
11.78
284
2.50



150
6.6
7.0
10
6000
11.44
298
2.54



160
6.5
7.2
10
6000
10.70
251
2.72



170
7.7
7.1
10
6000
10.60
257
2.77



180
8.3
6.9
10
6000
10.76
255
2.75



190
7.1
7.2
10
6000
10.53
265
2.75



200
7.1
7.0
7
5000
10.98
270
2.75



210
7.8
7.2
7
5000
11.61
268
2.74



220
7.4
7.2
7
5000
13.21
275
2.75



230
7.8
7.1
7
5000
13.23
272
2.75



240
7.2
7.3
7
5000
13.48
284
2.75



250
7.6
7.2
7
5000
13.25
287
2.78



260
7.4
7.2
7
5000
15.22
282
2.75



270
7.2
7.4
7
5000
14.98
282
2.75



280
7.4
7.2
7
5000
15.81
285
2.77



290
7.6
7.3
7
5000
16.36
279
2.75



300
7.8
7.5
7
5000
16.12
283
2.75



310
7.4
6.8
7
5000
15.45
293
2.75



320
7.2
6.6
7
5000
15.48
303
2.75



330
7.5
7.1
7
5000
16.08
292
2.75



340
7.5
7.6
7
5000
16.18
296
2.73



350
7.2
7.1
7
5000
16.39
289
2.74



360
7.9
7.5
7
5000
16.48
286
2.75



370
7.9
7.4
7
5000
16.10
291
2.75



380
7.8
6.9
7
5000
16.39
308
2.75



390
6.9
6.6
7
5000
16.17
303
2.75



400
2.6
6.5
12
7000
15.97
310
2.75



410
4.8
7.5
12
7000
16.91
294
2.75



420
2.2
7.3
12
7000
17.11
284
2.75



430
2.2
7.0
12
7000
16.99
291
2.76



440
2.8
7.1
12
7000
17.27
289
2.75



450
2.4
6.3
12
7000
16.96
288
2.76



460
2.5
7.3
12
7000
17.19
291
2.74



470
1.9
7.2
12
7000
17.19
296
2.74



480
2.3
6.8
12
7000
16.90
296
2.75



490
2.1
7.2
12
7000
17.67
306
2.72



500
2.8
7.3
12
7000
17.21
303
2.75



510
2.5
6.8
12
7000
17.30
308
2.75



520
2.2
7.0
12
7000
17.36
318
2.75



530
4.9
7.4
12
7000
17.10
312
2.74



540
5.4
7.3
12
7000
16.58
316
2.75



550
5.1
7.2
12
7000
16.33
322
2.75



560
5.2
7.2
12
7000
16.33
323
2.75



570
5.2
7.1
12
7000
15.60
325
2.73



580
5.8
7.5
12
7000
15.71
318
2.75



587
5.1
7.2
12
7000
15.37
318
2.75























Stack
Feed


Product
Product
Voltage
Current
C1(OUT)
C2(OUT)
ER
Feed
Product


Op.
FCE
Feed
ΔP
Flow
Resistivity
Section-2
Section-2
Flow
Flow
Flow
Silica
Silica


Hrs.
μS/cm
pH
psi
LPH
Mohms · cm
Vdc
Amps
LPH
LPH
LPH
ppb
ppb





11
2.9
6.8
8
6000
15.36
237
2.01
200
200
100
39
5.0


20
3.1
7.5
8
6000
16.67
247
2.01
200
200
80
34
6.0


30
5.6
7.5
8
6000
15.90
245
2.01
200
200
80
34
6.0


40
5.2
7.5
9
6000
15.10
255
2.01
200
200
80
34
6.0


50
4.6
7.4
9
6000
14.57
272
2.00
200
200
80
34
6.0


60
4.4
7.5
10
6000
15.10
293
2.01
200
200
80
32
8.0


70
1.5
6.9
10
6000
16.94
355
2.01
200
200
80
28
9.0


80
1.6
6.9
10
6000
17.13
358
1.99
200
200
80
32
8.0


90
7.0
7.4
10
6000
16.41
270
2.01
200
200
80
27
6.0


100
7.3
7.6
10
6000
13.10
313
2.50
200
200
80
39
7.0


110
7.6
7.6
10
6000
12.92
335
2.54
200
200
80
44
9.0


120
7.0
7.5
10
6000
12.58
334
2.50
200
200
80
44
9.0


130
7.6
7.5
10
6000
12.22
336
2.47
200
200
80
38
8.0


140
7.7
7.1
10
6000
11.78
360
2.52
200
200
80
38
8.0


150
6.6
7.0
10
6000
11.44
353
2.56
200
200
80
38
9.0


160
6.5
7.2
10
6000
10.70
249
2.76
200
200
80
38
9.0


170
7.7
7.1
10
6000
10.60
247
2.74
200
200
80
36
7.0


180
8.3
6.9
10
6000
10.76
255
2.75
200
200
80
40
8.0


190
7.1
7.2
10
6000
10.53
264
2.74
200
200
80
40
8.0


200
7.1
7.0
7
5000
10.98
264
2.74
200
200
80
32
5.0


210
7.8
7.2
7
5000
11.61
264
2.75
200
200
80
38
6.0


220
7.4
7.2
7
5000
13.21
271
2.74
200
200
80
38
6.0


230
7.8
7.1
7
5000
13.23
270
2.75
200
200
80
38
6.0


240
7.2
7.3
7
5000
13.48
276
2.75
200
200
80
42
6.0


250
7.6
7.2
7
5000
13.25
277
2.75
200
200
80
42
6.0


260
7.4
7.2
7
5000
15.22
276
2.75
200
200
80
36
6.0


270
7.2
7.4
7
5000
14.98
273
2.75
200
200
80
24
4.0


280
7.4
7.2
7
5000
15.81
274
2.73
200
200
80
24
4.0


290
7.6
7.3
7
5000
16.36
270
2.75
200
200
80
24
4.0


300
7.8
7.5
7
5000
16.12
275
2.75
200
200
80
24
4.0


310
7.4
6.8
7
5000
15.45
286
2.75
200
200
80
24
4.0


320
7.2
6.6
7
5000
15.48
294
2.75
200
200
80
24
4.0


330
7.5
7.1
7
5000
16.08
286
2.74
200
200
80
36
4.0


340
7.5
7.6
7
5000
16.18
287
2.74
200
200
80
36
4.0


350
7.2
7.1
7
5000
16.39
281
2.75
200
200
80
29
3.0


360
7.9
7.5
7
5000
16.48
277
2.75
200
200
80
38
5.0


370
7.9
7.4
7
5000
16.10
277
2.75
200
200
80
38
5.0


380
7.8
6.9
7
5000
16.39
294
2.75
200
200
80


390
6.9
6.6
7
5000
16.17
293
2.75
200
200
80
49.6
3.4


400
2.6
6.5
12
7000
15.97
301
2.75
200
200
80
59.7
6.6


410
4.8
7.5
12
7000
16.91
284
2.75
200
200
80
28.1
4.1


420
2.2
7.3
12
7000
17.11
274
2.75
200
200
80
19.3
4.1


430
2.2
7.0
12
7000
16.99
271
2.77
200
200
80
19.3
4.1


440
2.8
7.1
12
7000
17.27
275
2.74
200
200
80
30.1
4.0


450
2.4
6.3
12
7000
16.96
273
2.75
200
200
80
15.1
3.4


460
2.5
7.3
12
7000
17.19
276
2.74
200
200
80
25.4
3.0


470
1.9
7.2
12
7000
17.19
280
2.74
200
200
80
15.1
3.4


480
2.3
6.8
12
7000
16.90
276
2.76
200
200
80
19.9
2.6


490
2.1
7.2
12
7000
17.67
291
2.72
200
200
80
26.7
3.9


500
2.8
7.3
12
7000
17.21
287
2.74
200
200
80
28.8
2.0


510
2.5
6.8
12
7000
17.30
290
2.74
200
200
80
56.0
5.4


520
2.2
7.0
12
7000
17.36
294
2.74
200
200
80
32.0
3.5


530
4.9
7.4
12
7000
17.10
294
2.74
200
200
80
32.0
3.5


540
5.4
7.3
12
7000
16.58
299
2.76
200
200
80
30.0
5.3


550
5.1
7.2
12
7000
16.33
305
2.75
200
200
80
56.0
5.0


560
5.2
7.2
12
7000
16.33
309
2.75
200
200
80
56.0
5.0


570
5.2
7.1
12
7000
15.60
309
2.75
200
200
80
32.0
3.5


580
5.8
7.5
12
7000
15.71
306
2.75
200
200
80
32.0
3.5


587
5.1
7.2
12
7000
15.37
300
2.77
200
200
80
28.2
5.4
















TABLE 6





(EDI Apparatus Data with 35-cell pair; Product flow rate = 6.0 m3/hr to 10.0 m3/hr)
























Stack
Feed


Product
Product
Voltage
Current



Op.
FCE
Feed
ΔP
Flow
Resistivity
Section-1
Section-1



Hrs.
μS/cm
pH
psi
LPH
Mohms · cm
Vdc
Amps







600
2.6
6.3
13
6000
14.22
363
2.53



610
6.9
7.0
13
8000
16.67
339
2.52



620
4.9
7.3
13
8000
17.29
340
2.53



630
4.9
7.3
13
8000
17.37
344
2.54



640
4.5
7.0
13
8000
17.37
346
2.55



651
5.7
7.0
13
8000
17.04
337
2.56



660
5.9
7.3
13
8000
16.86
346
2.55



670
6.4
7.1
13
8000
16.63
349
2.52



680
7.0
7.6
13
8000
16.50
353
2.53



690
7.2
7.3
13
8000
16.44
365
2.54



700
6.8
7.3
16
9000
16.54
369
2.52



710
6.9
7.5
17
9000
16.52
370
2.53



720
6.2
7.3
17
9000
17.72
365
2.52



730
6.7
7.4
7
6000
16.32
380
2.53



740
6.9
7.4
7
6000
16.00
380
2.52



750
6.7
7.4
7
6000
16.65
343
2.02



760
6.8
7.4
7
6000
16.10
348
2.01



770
6.5
7.3
20
10000
15.86
343
2.02



780
6.7
7.1
18
10000
13.10
335
2.02



790
6.8
7.3
18
10000
12.54
430
2.54



800
6.3
7.1
18
10000
13.25
412
2.52



810
6.3
7.2
20
10000
13.30
405
2.52



820
6.6
7.4
20
10000
13.39
416
2.53



830
5.1
7.3
20
10000
14.32
409
2.54



840
5.6
7.3
20
10000
13.11
408
2.53



850
5.6
7.6
20
10000
14.52
409
2.53



857
5.5
7.3
20
10000
13.87
400
2.52























Stack
Feed


Product
Product
Voltage
Current
C1(OUT)
C2(OUT)
ER
Feed
Product


Op.
FCE
Feed
ΔP
Flow
Resistivity
Section-2
Section-2
Flow
Flow
Flow
Silica
Silica


Hrs.
μS/cm
pH
psi
LPH
Mohms · cm
Vdc
Amps
LPH
LPH
LPH
ppb
ppb





600
2.6
6.3
13
6000
14.22
368
2.57
230
230
80
28.8
6.1


610
6.9
7.0
13
8000
16.67
352
2.56
250
250
80
38.5
4.7


620
4.9
7.3
13
8000
17.29
377
2.54
250
250
80
38.5
4.7


630
4.9
7.3
13
8000
17.37
409
2.53
250
250
80
28.2
5.4


640
4.5
7.0
13
8000
17.37
427
2.54
250
250
80
32.0
3.5


651
5.7
7.0
13
8000
17.04
402
2.56
250
250
80
38.5
4.7


660
5.9
7.3
13
8000
16.86
428
2.52
250
250
80
37.2
4.8


670
6.4
7.1
13
8000
16.63
418
2.53
250
250
80
38.3
3.3


680
7.0
7.6
13
8000
16.50
408
2.53
250
250
80
36.5
6.1


690
7.2
7.3
13
8000
16.44
422
2.51
250
250
80
36.4
6.1


700
6.8
7.3
16
9000
16.54
433
2.53
250
250
80
36.4
6.1


710
6.9
7.5
17
9000
16.52
445
2.54
250
250
80
37.1
6.7


720
6.2
7.3
17
9000
17.72
438
2.55
250
250
80
36.4
6.1


730
6.7
7.4
7
6000
16.32
467
2.54
250
250
80
37.1
6.7


740
6.9
7.4
7
6000
16.00
432
2.50
250
250
80
30.8
4.6


750
6.7
7.4
7
6000
16.65
402
2.02
250
250
80
30.9
6.0


760
6.8
7.4
7
6000
16.10
404
2.01
250
250
80
17.2
2.6


770
6.5
7.3
20
10000
15.86
394
2.01
250
250
80


780
6.7
7.1
18
10000
13.10
380
2.02
250
250
80
33.0
6.8


790
6.8
7.3
18
10000
12.54
496
2.47
250
250
80
31.5
8.7


800
6.3
7.1
18
10000
13.25
480
2.52
250
250
80
31.5
8.7


810
6.3
7.2
20
10000
13.30
471
2.56
250
250
80
19.9
5.3


820
6.6
7.4
20
10000
13.39
488
2.55
250
250
80
20.6
4.0


830
5.1
7.3
20
10000
14.32
492
2.51
250
250
80
19.9
5.3


840
5.6
7.3
20
10000
13.11
484
2.53
250
250
80
31.5
6.7


850
5.6
7.6
20
10000
14.52
497
2.51
250
250
80
19.9
5.3


857
5.5
7.3
20
10000
13.87
478
2.5
250
250
80
19.9
5.3









Example-4
One trial was conducted to check the Flexibility of new EDI apparatus for treating 1st pass RO permeate water with FCE load greater than 10 μS/cm. For this one 30-cell pair stack was assembled similar to example-2 EDI apparatus and tested with 1st pass RO permeate water for 1010 Hours. The feed RO permeate water specification are as follows

    
    
        Conductivity=15-20 μS/cm
        pH=6.0-6.5
        Total Hardness=0.5-1.5 ppm as CaCO3
        Silica=200-400 ppb as SiO2
        CO2=1-3 ppm
    
    


The product flow rate was maintained 3.0 m3/hr (3000 LPH) throughout the experiment with pressure drop of 24-26 psi. The Resistivity of product water was achieved between 15 Mohms·cm and 17 Mohms·cm with product silica level of less than 15 ppb. The data of the experiment are summarized in table-7







TABLE 7





(EDI Apparatus data with 1st pass RO permeate water with Product flow rate of 3.0 m3/hr (3000 LPH)

























Feed


Product
Product
Voltage
Current
Voltage
Current


Op.
Cond.
Feed
ΔP
Flow
Resistivity
Section-1
Section-1
Section-2
Section-2


Hrs.
μS/cm
pH
psi
LPH
Mohms · cm
Vdc
amps
Vdc
amps





1
20.0
6.0
26
3000
16.74
169
1.1
195
1.5


10
18.6
6.3
26
3000
16.85
175
1.1
194
1.5


20
19.6
6.6
26
3000
16.54
175
1.1
192
1.5


30
19.6
6.5
26
3000
16.44
180
1.1
196
1.5


40
19.7
6.2
26
3000
16.66
185
1.1
237
2.0


50
20.2
6.2
26
3000
16.94
183
1.1
238
2.0


60
19.6
6.6
26
3000
16.92
191
1.1
247
2.0


70
19.0
6.0
26
3000
17.29
184
1.1
242
2.0


80
19.9
6.2
26
3000
16.98
185
1.1
247
2.0


90
19.6
6.7
26
3000
16.89
190
1.1
256
2.0


100
19.4
6.3
26
3000
17.09
185
1.1
245
2.0


110
19.6
6.3
26
3000
16.64
185
1.1
249
2.0


120
20.1
6.2
26
3000
16.38
185
1.1
245
2.0


130
19.3
6.3
26
3000
16.74
187
1.1
247
2.0


140
19.4
6.1
26
3000
16.97
182
1.1
240
2.0


150
19.3
6.4
26
3000
16.76
190
1.1
252
2.0


160
20.6
6.3
26
3000
16.57
193
1.1
250
2.0


170
19.0
6.3
24
3000
16.91
187
1.1
247
2.0


180
19.3
6.3
26
3000
17.09
182
1.1
240
2.0


190
19.5
6.4
26
3000
16.78
190
1.1
252
2.0


200
19.4
6.5
26
3000
16.84
193
1.1
250
2.0


210
19.3
6.6
26
3000
16.85
182
1.1
240
2.0


220
20.1
6.3
26
3000
16.76
190
1.1
252
2.0


230
19.0
6.3
26
3000
16.86
183
1.1
238
2.0


240
19.1
6.2
26
3000
16.70
190
1.1
246
2.0


250
19.0
6.5
26
3000
16.85
201
1.1
246
2.0


260
19.4
6.2
24
3000
16.36
191
1.1
247
2.0


270
19.8
6.3
24
3000
16.07
184
1.1
242
2.0


280
20.1
6.3
26
3000
16.19
185
1.1
247
2.0


290
20.6
6.1
26
3000
16.31
183
1.1
238
2.0


300
20.3
6.3
26
3000
16.38
190
1.1
246
2.0


310
20.9
6.4
24
3000
16.20
195
1.1
246
2.0


320
20.4
6.2
24
3000
16.61
191
1.1
247
2.0


330
19.9
6.3
24
3000
16.50
184
1.1
242
2.0


340
20.7
6.3
24
3000
16.31
185
1.1
247
2.0


350
19.7
6.7
24
3000
16.19
190
1.1
256
2.0


360
20.4
6.0
24
3000
16.20
185
1.1
245
2.0


370
19.8
6.5
24
3000
16.09
185
1.1
249
2.0


380
20.4
6.4
24
3000
16.10
185
1.1
245
2.0


390
20.5
6.2
24
3000
16.09
187
1.1
247
2.0


400
19.5
6.6
24
3000
16.10
182
1.1
240
2.0


410
20.7
6.6
24
3000
15.76
190
1.1
252
2.0


420
19.6
6.7
24
3000
16.05
193
1.1
250
2.0


430
20.3
6.4
24
3000
15.61
200
1.2
250
2.0


440
20.2
6.5
24
3000
15.72
201
1.2
251
2.0


450
20.8
6.3
24
3000
16.10
207
1.2
245
2.0


460
18.4
6.5
24
3000
16.21
205
1.2
245
2.0


470
18.0
6.6
24
3000
16.46
200
1.2
233
2.0


480
18.5
6.4
24
3000
16.10
210
1.2
237
2.0


490
18.6
6.2
24
3000
16.09
209
1.2
245
2.0


500
18.5
6.5
24
3000
15.85
200
1.2
243
2.0


510
18.6
6.2
24
3000
15.78
206
1.2
250
2.0


520
18.6
6.6
24
3000
15.67
203
1.2
244
2.0


530
19.0
6.4
24
3000
15.26
208
1.2
249
2.0


540
18.0
6.5
24
3000
14.97
210
1.2
251
2.0


550
14.1
6.4
24
3000
15.87
221
1.5
263
2.3


560
15.8
6.4
24
3000
15.60
215
1.5
261
2.3


570
16.1
6.4
24
3000
16.80
198
1.2
246
2.1


580
16.8
6.4
24
3000
16.57
206
1.2
260
2.2


590
15.2
6.6
24
3000
16.48
204
1.2
269
2.2


600
15.4
6.3
24
3000
16.34
200
1.2
270
2.2


610
15.2
6.4
24
3000
16.09
197
1.2
266
2.2


620
15.5
6.4
26
3000
16.08
198
1.2
268
2.2


630
15.9
6.4
26
3000
15.88
202
1.2
272
2.2


640
16.4
6.3
26
3000
15.80
202
1.2
268
2.2


650
16.5
6.3
26
3000
15.78
225
1.4
276
2.3


660
15.0
6.5
26
3000
15.92
213
1.3
276
2.3


670
15.6
6.5
26
3000
15.92
214
1.3
278
2.3


680
15.3
6.5
26
3000
16.03
223
1.3
287
2.3


690
16.1
6.5
26
3000
16.16
218
1.3
282
2.3


700
16.0
6.4
26
3000
16.17
217
1.3
286
2.3


710
18.0
6.5
26
3000
16.53
219
1.3
268
2.3


720
17.9
6.5
26
3000
16.25
222
1.3
284
2.3


730
17.0
6.5
26
3000
15.91
225
1.3
288
2.3


740
16.9
6.5
26
3000
15.66
222
1.3
284
2.3


750
16.7
6.2
26
3000
15.60
234
1.3
292
2.3


760
18.2
6.3
26
3000
16.36
233
1.3
284
2.3


770
17.6
6.5
26
3000
15.95
233
1.3
285
2.3


780
18.8
6.0
26
3000
15.58
250
1.4
282
2.3


790
18.5
6.0
26
3000
15.52
244
1.4
287
2.3


800
18.5
6.1
26
3000
16.25
245
1.4
266
2.3


810
18.5
6.1
26
3000
16.25
250
1.4
282
2.3


820
18.6
6.1
26
3000
15.85
254
1.4
289
2.3


830
18.4
6.1
26
3000
15.52
258
1.4
287
2.3


840
18.9
6.0
26
3000
15.56
264
1.4
292
2.3


850
18.0
6.2
26
3000
15.53
266
1.4
293
2.3


860
18.4
6.1
26
3000
15.21
268
1.4
288
2.3


870
18.2
6.1
26
3000
14.91
267
1.4
304
2.5


880
18.5
6.1
26
3000
15.25
275
1.4
310
2.5


890
18.5
6.2
26
3000
15.16
293
1.4
325
2.5


900
18.4
6.2
26
3000
15.01
294
1.4
316
2.5


910
18.6
6.2
26
3000
14.74
294
1.4
320
2.5


920
18.4
6.5
26
3000
14.85
305
1.4
317
2.5


930
18.4
6.4
26
3000
14.81
310
1.4
324
2.5


940
18.7
6.6
26
3000
15.40
276
1.4
298
2.5


950
18.9
6.5
26
3000
15.53
294
1.4
310
2.5


960
18.7
6.5
26
3000
15.15
292
1.4
324
2.5


970
18.6
5.9
26
3000
15.31
308
1.4
328
2.5


980
18.7
6.4
24
3000
15.38
322
1.4
336
2.5


990
18.1
6.5
24
3000
15.38
330
1.4
347
2.5


1000
18.3
6.3
24
3000
15.42
327
1.4
343
2.5


1010
18.3
6.3
24
3000
15.68
347
1.4
351
2.5






















Feed


Product
Product
C1(OUT)
C2OUT)
E.Rinse
Feed
Product
Feed


Op.
Cond.
Feed
ΔP
Flow
Resistivity
Flow
Flow
Flow
Silica
Silica
TH




















Hrs.
μS/cm
pH
psi
LPH
Mohms · cm
LPH
pH
LPH
pH
LPH
ppb
ppb
ppm





1
20.0
6.0
26
3000
16.74
200
9.5
200
9.2
80
226
6
0.1


10
18.6
6.3
26
3000
16.85
200
3.6
200
9.5
80


20
19.6
6.6
26
3000
16.54
200
3.6
200
7.7
80
231
8


30
19.6
6.5
26
3000
16.44
200
5.0
200
4.9
80
222
7


40
19.7
6.2
26
3000
16.66
200
9.3
200
9.2
80
224
7
0.1


50
20.2
6.2
26
3000
16.94
200
5.9
200
8.1
80
244
8


60
19.6
6.6
26
3000
16.92
200
8.1
200
8.0
80
238
8


70
19.0
6.0
26
3000
17.29
200
9.4
200
8.1
80


80
19.9
6.2
26
3000
16.98
200
6.8
200
9.2
80
205
9


90
19.6
6.7
26
3000
16.89
200
7.6
200
7.7
80
438
10
0.2


100
19.4
6.3
26
3000
17.09
200
9.5
200
8.7
80
397
11


110
19.6
6.3
26
3000
16.64
200
8.7
200
9.1
80
385
11


120
20.1
6.2
26
3000
16.38
200
8.4
200
9.3
80
393
10


130
19.3
6.3
26
3000
16.74
200
8.7
200
8.9
80
385
11


140
19.4
6.1
26
3000
16.97
200
8.7
200
8.6
80
404
14


150
19.3
6.4
26
3000
16.76
200
7.8
200
9.2
80
365
14
0.3


160
20.6
6.3
26
3000
16.57
200
10.3
200
9.7
80
362
14


170
19.0
6.3
24
3000
16.91
200
7.5
200
9.2
80
358
13


180
19.3
6.3
26
3000
17.09
200
8.7
200
7.8
80
418
13


190
19.5
6.4
26
3000
16.78
200
8.6
200
9.3
80
409
13


200
19.4
6.5
26
3000
16.84
200
8.2
200
9.3
80
344
12


210
19.3
6.6
26
3000
16.85
200
8.6
200
8.9
80
391
14


220
20.1
6.3
26
3000
16.76
200
8.2
200
9.3
80


230
19.0
6.3
26
3000
16.86
200
9.3
200
8.8
80
163
13
0.5


240
19.1
6.2
26
3000
16.70
200
9.2
200
9.6
80


250
19.0
6.5
26
3000
16.85
200
5.7
200
10
80


260
19.4
6.2
24
3000
16.36
220
5.6
200
9.2
80
201
13
0.6


270
19.8
6.3
24
3000
16.07
220
4.5
200
9.3
80
207
14
0.6


280
20.1
6.3
26
3000
16.19
220
5.7
200
9.6
80
201
13
0.6


290
20.6
6.1
26
3000
16.31
220
3.9
200
9.5
80
203
14
0.6


300
20.3
6.3
26
3000
16.38
220
9.3
200
10.0
80
196
11
0.7


310
20.9
6.4
24
3000
16.20
220
3.7
200
9.9
80
235
11
0.7


320
20.4
6.2
24
3000
16.61
220
3.8
200
9.9
80
221
11
0.7


330
19.9
6.3
24
3000
16.50
220
4.1
200
9.8
80
217
12
0.7


340
20.7
6.3
24
3000
16.31
220
4.4
200
10
80
231
10
0.8


350
19.7
6.7
24
3000
16.19
250
4.2
170
9.9
80
240
10
0.8


360
20.4
6.0
24
3000
16.20
250
4.4
170
9.6
80
224
12
0.7


370
19.8
6.5
24
3000
16.09
250
4.2
170
10.2
80
201
10
0.7


380
20.4
6.4
24
3000
16.10
250
4.4
170
9.8
80
203
10
0.8


390
20.5
6.2
24
3000
16.09
250
4.3
170
9.5
80
215
10
0.8


400
19.5
6.6
24
3000
16.10
250
4.2
170
9.8
80
208
8
0.8


410
20.7
6.6
24
3000
15.76
250
4.2
170
10
80
204
8
0.8


420
19.6
6.7
24
3000
16.05
250
4.3
170
10.1
80
209
8
0.8


430
20.3
6.4
24
3000
15.61
250
4.7
170
9.9
80


440
20.2
6.5
24
3000
15.72
250
4.7
170
9.8
80
251
12
0.8


450
20.8
6.3
24
3000
16.10
250
5.3
170
9.8
80
223
11
0.8


460
18.4
6.5
24
3000
16.21
250
5.1
170
10.0
80
241
13
0.7


470
18.0
6.6
24
3000
16.46
250
6.3
170
9.9
80
217
12
0.7


480
18.5
6.4
24
3000
16.10
250
4.6
170
9.8
80
256
13
0.8


490
18.6
6.2
24
3000
16.09
250
4.0
170
9.5
80
232
13
0.7


500
18.5
6.5
24
3000
15.85
250
4.3
170
9.9
80
219
10
0.8


510
18.6
6.2
24
3000
15.78
250
4.3
170
9.9
80
217
9
0.6


520
18.6
6.6
24
3000
15.67
250
4.3
170
9.3
80
222
10
0.6


530
19.0
6.4
24
3000
15.26
250
4.0
170
9.9
80
215
10
0.7


540
18.0
6.5
24
3000
14.97
250
4.2
170
9.8
80
207
11
0.7


550
14.1
6.4
24
3000
15.87
250
4.4
170
9.7
80
221
10
0.6


560
15.8
6.4
24
3000
15.60
250
4.2
170
9.7
80
237
9
0.7


570
16.1
6.4
24
3000
16.80
250
6.6
170
9.6
80
228
9
0.7


580
16.8
6.4
24
3000
16.57
250
6.0
170
9.4
80


590
15.2
6.6
24
3000
16.48
250
4.4
170
9.1
80
226
10
0.7


600
15.4
6.3
24
3000
16.34
250
4.3
170
9.3
80
220
9
0.7


610
15.2
6.4
24
3000
16.09
250
4.5
170
9.4
80
202
8
0.7


620
15.5
6.4
26
3000
16.08
250
4.5
170
9.4
80


630
15.9
6.4
26
3000
15.88
250
4.3
170
9.5
80
204
8
0.7


640
16.4
6.3
26
3000
15.80
250
4.2
200
9.3
80
215
8
0.9


650
16.5
6.3
26
3000
15.78
250
3.6
200
9.3
80
199
8
0.9


660
15.0
6.5
26
3000
15.92
250
4.3
200
9.3
80
217
8
0.8


670
15.6
6.5
26
3000
15.92
250
4.1
200
9.4
80
207
9
1.0


680
15.3
6.5
26
3000
16.03
250
4.8
200
9.4
80
217
8
0.9


690
16.1
6.5
26
3000
16.16
250
5.4
200
9.4
80


700
16.0
6.4
26
3000
16.17
250
4.7
200
9.4
80
198
8
1.0


710
18.0
6.5
26
3000
16.53
250
6.2
200
9.3
80
211
9
1.0


720
17.9
6.5
26
3000
16.25
250
4.2
200
9.2
80
212
9
1.0


730
17.0
6.5
26
3000
15.91
250
4.3
200
9.1
80
208
9
1.0


740
16.9
6.5
26
3000
15.66
250
4.1
200
9.2
80
203
9
1.0


750
16.7
6.2
26
3000
15.60
250
4.3
200
9.2
80
198
7
1.0


760
18.2
6.3
26
3000
16.36
250
5.3
200
9.4
80
211
9
1.0


770
17.6
6.5
26
3000
15.95
250
4.2
200
9.7
80
198
7
1.0


780
18.8
6.0
26
3000
15.58
250
3.9
200
9.1
80
198
7
1.0


790
18.5
6.0
26
3000
15.52
250
3.9
200
9.4
80
219
9
1.0


800
18.5
6.1
26
3000
16.25
250
4.8
200
9.3
80
232
10
1.0


810
18.5
6.1
26
3000
16.25
250
3.8
200
9.5
80
227
10
1.0


820
18.6
6.1
26
3000
15.85
250
4.3
200
8.9
80
265
10
1.0


830
18.4
6.1
26
3000
15.52
250
3.9
200
9.4
80
259
10
1.6


840
18.9
6.0
26
3000
15.56
250
3.9
200
9.4
80
252
11
1.5


850
18.0
6.2
26
3000
15.53
250
4.1
200
9.2
80
255
12
1.5


860
18.4
6.1
26
3000
15.21
250
3.7
200
8.5
80
269
10
1.5


870
18.2
6.1
26
3000
14.91
250
4.3
200
6.4
80
272
10
1.5


880
18.5
6.1
26
3000
15.25
250
3.9
200
9.3
80
255
9
1.6


890
18.5
6.2
26
3000
15.16
250
3.9
200
8.9
80
257
10
1.4


900
18.4
6.2
26
3000
15.01
250
3.7
200
9.5
80
262
11
1.4


910
18.6
6.2
26
3000
14.74
250
3.7
200
9.8
80
256
11
1.4


920
18.4
6.5
26
3000
14.85
250
4.3
200
7.4
80
231
10
1.5


930
18.4
6.4
26
3000
14.81
250
3.8
200
9.4
80
262
10
1.4


940
18.7
6.6
26
3000
15.40
250
9.0
200
9.6
80
279
10
1.5


950
18.9
6.5
26
3000
15.53
250
4.2
200
9.4
80
267
10
1.5


960
18.7
6.5
26
3000
15.15
250
3.9
200
9.3
80
263
11
1.4


970
18.6
5.9
26
3000
15.31
250
3.9
200
9.2
80
275
11
1.4


980
18.7
6.4
24
3000
15.38
250
3.7
200
9.7
80
259
10
1.4


990
18.1
6.5
24
3000
15.38
250
4.3
200
6.9
80
278
10
1.4


1000
18.3
6.3
24
3000
15.42
250
4.2
200
6.6
80
271
10
1.4


1010
18.3
6.3
24
3000
15.68
250
4.2
200
6.6
80
258
10
1.5









CONCLUSIONS
The stack with conventional design given in example 1 does not deliver higher flows at lower differential pressures whereas the examples given above with split flow method are able to deliver much higher flows at same differential pressure while maintaining the quality parameters required for product. The same stack design can also produce quality product when operated with water produced by single pass RO in a conventional mode as detailed in data through example 4. This proves the flexibility of the stack design for both single and double pass RO waters.

## Claims

1. An electrodeionization apparatus comprising:
a first end plate;
a first electrode house plate (“EHP”) located adjacent to the first end plate, said EHP comprising two cathodes, cationic resin, and an anion membrane;
a plurality of cell pairs comprising alternating concentrate chambers and dilute chambers, wherein each concentrate chamber comprises a concentrate spacer placed over an anion membrane,
wherein each concentrate chamber comprises two independent concentrate sections separated by a concentrate rib, said concentrate sections comprising a conductive mesh, wherein each of said concentrate sections has separate concentrate inlet ports and concentrate outlet ports; and
wherein each dilute chamber comprises a cation membrane oriented toward the first EHP, a dilute spacer, and an anion membrane, wherein each dilute chamber comprises two independent dilute sections separated by a dilute rib and fed by a common feed port that splits flow of feed water equally into the independent dilute sections, each of said dilute sections having separate product ports;

a second end plate; and
a second EHP located adjacent to the second end plate, said second EHP comprising two anodes, a cationic membrane, and cation resin media.

2. The electrodeionization apparatus of claim 1, further comprising a product header for collecting and combining product water from each of said product ports.

3. The electrodeionization apparatus of claim 1, comprising 30-35 cell pairs.

4. The electrodeionization apparatus of claim 1, comprising at least 30 cell pairs.

5. The electrodeionization apparatus of claim 1, further comprising a plurality of EPDM rings between the concentrate spacers and dilute spacers.

6. An combined electrodeionization apparatus comprising a plurality of electrodeionization apparatus of claim 1 connected in series.

7. The electrodeionization apparatus of claim 1, wherein the electrodeionization capacity of the apparatus is twice that of an electrodeionization apparatus having the same number of cells and same membrane area but single-section dilute spacers and single-section concentrate spacers.