METHOD FOR TREATING WHEY DEMINERALIZATION EFFLUENTS

Abstract

A treatment of demineralization effluents, particularly recycling effluents, a method for demineralizing whey and treating the effluents, and a facility for implementation thereof. The treatment of whey demineralization effluents includes: i) supplying a whey demineralization effluent, ii) treating by reverse osmosis effluent recovered in i) to obtain a reverse osmosis permeate and retentate, iii) neutralizing the retentate pH, iv) treating the neutralized retentate by nanofiltration to obtain a permeate including monovalent ions and a retentate including divalent ions and residual organic materials, v) treating the permeate in iv) by electrodialysis with bipolar membrane to obtain acidic solution(s) and basic solution(s). Thus, it is possible to treat effluents, limit their environmental impact, generate solutions for the whey demineralization process, reduce the cost of whey demineralization because some process water from electrodialysis comes from treatment of the generated effluents, and reduce the total amount of effluent sent to the wastewater treatment plant.

Claims

1-10. (canceled)

11. A method for treating whey demineralization effluents, comprising the following steps: i) supplying a whey demineralization effluent, ii) treating by reverse osmosis the effluent recovered in step i) so as to obtain a reverse osmosis permeate and retentate, iii) neutralizing the reverse osmosis retentate to a pH of between 6 and 9, iv) treating the neutralized reverse osmosis retentate by nanofiltration so as to obtain a nanofiltration permeate comprising the monovalent ions and a nanofiltration retentate comprising the divalent ions and the residual organic materials, and v) treating the nanofiltration permeate obtained in step iv) by electrodialysis with bipolar membrane, so as to obtain at least one acidic solution and at least one basic solution.

12. The method according to claim 11, wherein the whey demineralization effluent is a brine from electrodialysis of whey, preferably of sweet whey.

13. The method according to claim 11, wherein step ii) is carried out so as to obtain a concentration factor (CF) of 3 to 5 in the retentate.

14. The method according to claim 11, wherein the neutralization in step iii) is carried out to a pH between 6.5 and 9 and wherein it also comprises a step of mechanical separation of the neutralized retentate so as to remove the tricalcium phosphate precipitate, the step iv) of nanofiltration then being carried out on the separation supernatant free of tricalcium phosphate.

15. The method according to claim 11, wherein the step v) of electrodialysis with bipolar membrane is carried out so as to obtain a conductivity of the permeate of between 0.2 and 1.2 mS/cm.

16. A method for demineralizing whey and for treating the effluents produced, comprising the following steps: a) supplying a whey, b) acidifying the whey to a pH of between 2.0 and 3.5, c) electrodialyzing the acidified whey, d) recovering the electrodialysis brine and implementing a method for treating demineralization effluents according to claim 1, said demineralization effluent in step i) being said electrodialysis brine.

17. The method according to claim 16, further comprising a step of recycling all or part of the acidic solution which is separated out after electrodialysis with bipolar membrane according to step v), for acidification of the whey according to step b).

18. The method according to claim 16, further comprising a step of recycling all or part of the basic solution which is separated out after electrodialysis with bipolar membrane according to step v), for neutralization of the reverse osmosis retentate according to step iii).

19. The method according to claim 16, further comprising a step of recycling all or part of the reverse osmosis permeate from step ii), as process water for step c) of electrodialyzing the acidified whey.

20. A facility suitable for demineralizing whey and for treating the effluents produced, said facility comprising: a first electrodialysis device comprising a first inlet intended to receive the whey, a second inlet intended to receive the process water, a first outlet for the demineralized whey, and a second outlet for the demineralization effluent, and an effluent treatment system comprising: a reverse osmosis device comprising an inlet for the demineralization effluent connected to the second outlet of the electrodialysis device, a first outlet for the reverse osmosis permeate, and a second outlet for the reverse osmosis retentate, a neutralization device comprising a first inlet for the reverse osmosis retentate connected to the second outlet of the reverse osmosis device, a second inlet for a neutralization solution, and an outlet for the neutralized reverse osmosis retentate, a nanofiltration device comprising an inlet for the neutralized reverse osmosis retentate connected directly to the outlet of the neutralization device or indirectly via a mechanical separation device, a first outlet for the neutralized nanofiltration retentate, and a second outlet for the nanofiltration permeate, and a second electrodialysis device with bipolar membrane having an inlet for the nanofiltration permeate and connected to the second outlet of the nanofiltration device, a first outlet for an acidic solution, a second outlet for a basic solution, said system comprising recycling means comprising all or part of the following means: a means connecting the first outlet for the reverse osmosis permeate of the reverse osmosis device with the second inlet of the first electrodialysis device intended to receive the process water, and/or a means connecting the first outlet for an acidic solution of the second electrodialysis device with bipolar membrane with the second inlet of the first electrodialysis device, and/or a means connecting the second outlet for a basic solution of the second electrodialysis device with bipolar membrane with the second inlet of the neutralization device and/or with the first outlet of the first electrodialysis device.

Description

EXAMPLES

Example 1

[0118] The aim of this example is to implement the method for treating demineralization effluent according to the invention.

[0119] A. Supplying the Demineralization Effluent:

[0120] The effluent treated according to this example is a brine resulting from demineralization of a sweet whey having the ion concentrations and characteristics summarized in Table 1 below:

TABLE-US-00001 TABLE 1.1 Dry extract (%) 21.8 pH 6.7 Conductivity (mS/cm) 20.28

[0121] The recovered brine has a pH of 2.4 and the ion concentrations are as presented in Table 1.2 below:

TABLE-US-00002 TABLE 1.2 K.sup.+ Na.sup.+ Ca2.sup.+ Mg2.sup.+ Cl.sup.− P Ash (%) Concentrations 674 163 62 13 808 77 1.9 (mg/100 g liquid)

[0122] B. Treatment of Brine Generated by Demineralization of Sweet Whey

[0123] Reverse Osmosis:

[0124] The brine obtained after demineralization of sweet whey is treated by reverse osmosis according to step b) of the method of the invention. Reverse osmosis is carried out starting with 40 L of brine until a concentration factor (CF) equal to 4 is obtained in the retentate. The final volume in the retentate is then 10 L and the final volume in the permeate is 30 L.

[0125] The characteristics of the reverse osmosis are presented in Table 1.3 below:

TABLE-US-00003 TABLE 1.3 AG 1812 Membrane (GE Membranes) Target pressure (bar) 30 Flow rate (L/h) 900 Initial volume (L) 40 Desired CF 4 Final volume of retentate (L) 10 Final volume of permeate (L) 30 Temperature 45° C.

[0126] The COD, the dry extract percentage, the ash content, the pH, as well as the concentrations (mg/100 g) of the various ions in the retentate were measured at different CF and up to the target CF, are presented in Table 1.4 below:

TABLE-US-00004 TABLE 1.4 CF K Na Ca Mg Cl P COD DE % Ash % pH 1.00 610 148 66 13 776 74 569 2.6 1.9 2.53 1.33 820 191 83 17 1100 100 817 3.3 2.4 2.55 2 1189 278 129 24 1413 140 1300 4.6 3.3 2.58 4 1979 474 217 37 2310 244 2128 7.7 5.5 2.61

[0127] This reverse osmosis step is repeated two more times under the same conditions, in order to obtain an additional 20 liters of retentate and thus bring the total volume of the reverse osmosis retentate obtained to 30 liters.

[0128] Nanofiltration:

[0129] The reverse osmosis retentate is then neutralized at 20° C. to pH 7 with a 40% (by weight) NaOH solution, and a tricalcium phosphate precipitate forms.

[0130] The 30 liters of reverse osmosis retentate are then decanted for 12 hours, and 21 L of supernatant are obtained. It is therefore the 21 L of supernatant which are then nanofiltered.

[0131] Nanofiltration is carried out until a concentration factor equal to 3 is obtained in the nanofiltration permeate. The characteristics of the nanofiltration are presented below:

TABLE-US-00005 TABLE 1.5 DK 1812 Membrane (GE Membrane) Target pressure (bar) 25 Flow rate (L/h) 900 Initial volume (L) 21 Desired CF 3 Final volume of retentate (L) 10 Final volume of permeate (L) 20 Temperature 20° C.

[0132] Nanofiltration of the 21 L of supernatant makes it possible to obtain 14 L of nanofiltration permeate containing only the monovalent ions, such as K.sup.+ and Na.sup.+.

[0133] The COD, the dry extract percentage, the ash content (%), the pH, as well as the concentrations (mg/100 g) of the various ions in the permeate, were measured and are presented in Table 1.6 below:

TABLE-US-00006 TABLE 1.6 CF K Na Ca Mg Cl P COD DE Ash pH 1.0 1484 853 77 25 1904 119 1554 6.6 5.2 6.47 3.0 2204 1147 150 59 1655 288 3004 10.3 4.9 6.52

[0134] Electrodialysis with Bipolar Membrane:

[0135] The nanofiltration permeate is then treated by electrodialysis with bipolar membrane. The treatment is done in two steps in this example.

[0136] The first step begins with a volume of 7 L of permeate in the feed compartment, 5 L of water in the acid compartment, and 5 L of water in the base compartment.

[0137] Electrodialysis is initiated in order to reduce the conductivity of the permeate, initially equal to 50 mS/cm, to a value below 0.5 mS/cm.

[0138] As soon as the conductivity of 0.5 mS/cm is reached, a second step is carried out with 7 new liters of permeate in the feed compartment. The acid and base produced are unchanged, however, in order to allow them to become even further concentrated. The conductivity goal for the feed is the same as in the first step.

[0139] At the end of the electrodialysis, the final measured conductivity of the permeate is 1.1 mS/cm, the acidic solution has a concentration equal to 1.08 mol/L, and the basic solution has a concentration of 0.87 mol/L.

[0140] The values of the conductivities of the permeate are given in Table 1.7 below:

TABLE-US-00007 TABLE 1.7 Conductivity (mS/cm) Start of 1.sup.st step 50.0 End of 1st step 0.51 Start of 2.sup.nd step 50.0 End of 2.sup.nd step 1.09

[0141] Below are the concentrations in the acidic solution and basic solution, obtained at the end of steps 1 and 2:

TABLE-US-00008 TABLE 1.8 Unit Acid Base Step 1 Mol/L of H.sup.+ 0.61 0.43 Mass % of HCl 2.2 3.9 Step 2 Mol/L of OH.sup.− 1.08 0.87 Mass % of NaOH 1.7 3.5

[0142] Finally, Table 1.9 below shows the mineral compositions (mg/100 g of liquid) of the acidic and basic solution at the end of each step:

TABLE-US-00009 TABLE 1.9 K Na Ca Mg Step 1 Acidic 22 87 4.4 1.3 solution Basic 6 705 5.9 0 solution Step 2 Acidic 229 201 5.3 1.4 solution Basic 2006 1208 5.2 0 solution

[0143] At the end of the bipolar electrodialysis, the molar ratio between the potassium and sodium concentrations in the basic solution is 49/51 (K/Na). The base produced therefore seems to be a basic solution composed of potash and soda in a 50/50 molar ratio.

[0144] The method according to the invention thus makes it possible to treat the brine resulting from whey demineralization in order to obtain, in particular, acidic and basic solutions which can be reused for other applications.

Example 2

[0145] Using a different whey than in Example 1, the aim of this example is to implement the method for demineralizing whey and for treating the produced effluents according to the invention.

[0146] A. Production of Whey Demineralization Effluent:

[0147] The sweet whey used for the demineralization has the ion concentrations and characteristics listed in Table 2.1 below:

TABLE-US-00010 TABLE 2.1 Dry extract (%) 23.0 pH 6.2 Conductivity (mS/cm) 22.05

[0148] The sweet whey is then acidified to pH 3 at the start of demineralization, with an acidic solution produced in Example 1.

[0149] Starting with 19.7 L of whey, a first electrodialysis step is carried out until a conductivity of the whey of about 3 mS/cm is obtained.

[0150] The whey is then neutralized to pH 6.2 with the basic solution produced in Example 1, then a second electrodialysis step is carried out until the conductivity of the whey is reduced to approximately 1.6 mS/cm.

[0151] The ion concentrations (mg/100 g of dry extract) in the whey at the start and end of the electrodialysis (ED) are given in Table 2.2 below:

TABLE-US-00011 TABLE 2.2 K Na Ca Mg Cl P Ash (%) Starting 2692 700 600 117 3878 570 8.48 concentration ED Ending 203 181 240 66 42 222 1.61 concentration ED

[0152] The brine circuit of the electrodialyzer initially contains 20 L of process water which is not changed between the two electrodialysis steps. At the end of the electrodialysis, the brine is recovered and has a pH of 2.4.

[0153] The ion concentrations in the brine were measured at the start and end of the electrodialysis and are listed below:

TABLE-US-00012 TABLE 2.3 K Na Ca Mg Cl P Ash (%) Start of electrodialysis 0 3 8 0 3 1 0.54 (in mg/100 g liquid) End of electrodialysis 610 203 71 13 823 74 1.89 (in mg/100 g liquid)

[0154] B. Recycling the Brine Generated by Whey Demineralization

[0155] Reverse Osmosis:

[0156] In the same manner as in Example 1, reverse osmosis is carried out starting with 40 L of brine, until a concentration factor (CF) equal to 4 is obtained in the retentate. The final volume in the retentate is then 10 L and the final volume in the permeate is 30 L. This reverse osmosis step is repeated twice in order to obtain 20 L of additional retentate. The total volume of the reverse osmosis retentate thus obtained is 30 liters.

[0157] The characteristics of the reverse osmosis are identical to those of Example 1.

[0158] The concentrations (mg/100 g) of the various ions in the retentate measured at different CF:

TABLE-US-00013 TABLE 2.4 CF K Na Ca Mg Cl P COD DE Ash % pH 1.00 540 169 69 12 768 70 459 2.6 1.69 2.48 1.33 658 216 85 15 950 91 / 3.4 2.27 2.45 2.00 954 309 119 22 1397 129 / 4.7 3.08 2.55 4.00 1564 491 189 33 1986 198 1353  6.9 4.85 2.53

[0159] Nanofiltration:

[0160] The reverse osmosis retentate is then neutralized to pH 8.6 with a solution of KOH/NaOH (at 0.5M KOH and 0.5M NaOH) reconstituted from the basic solution obtained in Example 1. A precipitate of tricalcium phosphate forms.

[0161] The reverse osmosis retentate is then decanted for 12 hours and 17 L of supernatant are obtained. It is therefore the 17 L of supernatant which are then nanofiltrated.

[0162] Nanofiltration is carried out until a concentration factor equal to 3 in the nanofiltration permeate is obtained. The characteristics of the nanofiltration are identical to those of Example 1.

[0163] The ion concentrations in the nanofiltration retentate are listed below:

TABLE-US-00014 TABLE 2.5 CF K Na Ca Mg Cl P COD DE % Ash % 1.0 807 392 1 0 1219 1 2 2.7 2.50 1.5 1064 496 1 0 1540 1 / 3.4 3.17 Overall (3) 989 465 1 0 1639 1 4 3.2 3.07

[0164] Nanofiltration of the 17 L of supernatant makes it possible to obtain 11.5 L of nanofiltration permeate containing only the monovalent ions, such as K.sup.+ and Na.sup.+.

[0165] Electrodialysis with Bipolar Membrane:

[0166] The nanofiltration permeate is then treated by electrodialysis with bipolar membrane according to the same protocol as Example 1, by a two-step treatment.

[0167] The first step begins with a volume of 5.5 L of permeate in the feed compartment, 5 L of water in the acid compartment, and 5 L of water in the base compartment.

[0168] Electrodialysis is initiated in order to reduce the conductivity of the permeate, initially equal to 50 mS/cm, to a value less than 1 mS/cm.

[0169] The second step is carried out with 5.5 new liters of permeate in the feed compartment. The acidic and basic solutions produced are unchanged, however, in order to allow their further concentration. The conductivity goal for the feed is the same as in the first step, namely a conductivity of less than 1 mS/cm.

[0170] At the end of the electrodialysis, the final measured conductivity of the permeate is 0.7 mS/cm, the acidic solution has a concentration equal to 0.69 mol/L, and the basic solution has a concentration of 0.64 mol/L.

[0171] The values of the conductivities of the permeate are given in Table 2.6 below:

TABLE-US-00015 TABLE 2.6 Conductivity (mS/cm) Start of 1.sup.st step 50.0 End of 1.sup.st step 0.7 Start of 2.sup.nd step 46 End of 2.sup.nd step 0.7

[0172] Below are the concentrations in the acidic solution and basic solution, obtained at the end of steps 1 and 2:

TABLE-US-00016 TABLE 2.7 Unit Acid Base Step 1 Mol/L of H.sup.+ 0.34 0.32 Mass % of HCl 1.2 1.3 Step 2 Mol/L of OH.sup.− 0.69 0.64 Mass % of NaOH 2.5 2.6

[0173] Finally, Table 2.8 below shows the mineral compositions (mg/100 g of liquid) of the acidic and basic solution at the end of each step:

TABLE-US-00017 TABLE 2.8 K Na Step 1 Acidic 37 33 solution Basic 604 332 Solution Step 2 Acidic 67 46 solution Basic 1308 658 Solution

[0174] At the end of the bipolar electrodialysis, the molar ratio between the potassium and sodium concentrations in the basic solution is 54/46 (K/Na). The base produced therefore seems to be a basic solution composed of potash and soda in a 50/50 molar ratio.

[0175] The method according to the invention thus makes it possible to demineralize whey and treat the brine in order to obtain, in particular, acidic and basic solutions which can be reused in the demineralization process as such, thus limiting discharges to a wastewater treatment plant.

Example 3

[0176] The purpose of this example is to present a facility suitable for implementing the method according to the invention. Said facility is presented schematically in FIG. 2, and comprises: [0177] a first electrodialysis device ED comprising a first inlet 11 intended to receive the whey, a second inlet 12 intended to receive the process water, a first outlet 13 for the demineralized whey, and a second outlet 14 for the demineralization effluent, [0178] an effluent treatment system comprising: [0179] a reverse osmosis device OI comprising an inlet 21 for the demineralization effluent connected to the second outlet 14 of the electrodialysis device, a first outlet 22 for the reverse osmosis permeate, and a second outlet 23 for the reverse osmosis retentate, [0180] a neutralization device NL comprising a first inlet 31 for the reverse osmosis retentate connected to the second outlet 23 of the reverse osmosis device, a second inlet 32 for a neutralization solution, and an outlet 33 for the neutralized reverse osmosis retentate, [0181] a nanofiltration device NF comprising an inlet 51 for the neutralized reverse osmosis retentate connected directly to the outlet 33 of the neutralization device, a first outlet 52 for the neutralized nanofiltration retentate, and a second outlet 53 for the nanofiltration permeate, [0182] a second electrodialysis device with bipolar membrane EDBP having an inlet 61 for the nanofiltration permeate and connected to the second outlet 53 of the nanofiltration device NF, a first outlet 62 for an acidic solution, a second outlet 63 for a basic solution, [0183] said system comprising recycling means comprising all or part of the following means: [0184] a means R1 connecting the first outlet 22 for the reverse osmosis permeate of the reverse osmosis device with the second inlet 12 of the first electrodialysis device ED intended to receive the process water, and/or [0185] a means R2 connecting the first outlet 62 for an acidic solution of the second electrodialysis device with bipolar membrane EDBP with the second inlet 12 of the first electrodialysis device, and/or [0186] a means R3 connecting the second outlet 63 for a basic solution of the second electrodialysis device with bipolar membrane EDBP with the second inlet 32 of the neutralization device NL and/or with the first outlet 13 of the first electrodialysis device ED.

[0187] In the case where the neutralization is carried out at a pH of 6.5 to 9, the outlet 33 for the neutralized reverse osmosis retentate of the neutralization device NL is connected by a pipe to the inlet 41 of the mechanical separation device, and the outlet 42 of the latter device is connected by a pipe to the inlet 51 of the nanofiltration device.

[0188] In the case where the method is carried out continuously, the connections and the means connecting the various inlets and outlets of the devices are ensured by pipes.

NAMING CONVENTIONS IN THE FIGURES

[0189] A: Anode [0190] C: Cathode [0191] SP: mechanical separation device [0192] E.EDP: inlet for process water [0193] E.LS: inlet for whey [0194] ED: electrodialysis device [0195] EDBP: electrodialysis device with bipolar membrane [0196] LS: Whey [0197] LSD: Demineralized whey [0198] MA: anionic membrane [0199] MC: cationic membrane [0200] NF: nanofiltration device [0201] NL: neutralization device [0202] OI: reverse osmosis device [0203] P.OI: reverse osmosis permeate [0204] R.NF: Nanofiltration retentate [0205] S.Ac: Acidic solution [0206] S.Ba: Basic solution [0207] S.LSD: outlet for demineralized whey [0208] S.NI: Neutralization solution [0209] S.Sau: outlet for brine [0210] R1: first recycling means [0211] R2: second recycling means [0212] R3: third recycling means [0213] 11: first inlet for whey [0214] 12: second inlet for process water [0215] 13: first outlet for demineralized whey [0216] 14: second outlet for demineralization effluent [0217] 21: inlet for demineralization effluent [0218] 22: first outlet for reverse osmosis permeate [0219] 23: second outlet for reverse osmosis retentate [0220] 31: first inlet for reverse osmosis retentate [0221] 32: second inlet for neutralization solution [0222] 33: outlet for neutralized reverse osmosis retentate [0223] 41: inlet for neutralized reverse osmosis retentate [0224] 42: outlet for separation supernatant free of tricalcium phosphate [0225] 51: inlet for neutralized reverse osmosis retentate [0226] 52: first outlet for nanofiltration retentate [0227] 53: second outlet for nanofiltration permeate [0228] 61: inlet for nanofiltration permeate [0229] 62: first outlet for acidic solution [0230] 63: second outlet for basic solution