HK40059416A - Method for treating whey demineralisation effluents - Google Patents

Description

The present invention relates to the treatment of demineralization effluents, particularly the recycling of such effluents, and concerns a process for the demineralization of whey and the treatment of the resultant effluents, as well as a facility as such suitable for the implementation of the process.

Whey is the liquid part of milk that is coagulated, which is caused by the denaturation of casein, the majority of milk protein. There are two types of coagulation, each leading to two different types of whey. Depending on whether the coagulation is a lactic coagulation or a sour coagulation, the resulting whey is respectively called acid whey or sweet whey.

The exploitation of whey has long been a matter of both economic and ecological concern, as although its composition is interesting, whey has a Chemical Oxygen Demand (COD) of 50 g/L to 70 g/L, making it a polluting organic product which cannot be released into nature and whose transport is expensive because of its highly diluted nature (dry extract 5 to 6%).

Thus, over time, methods of recovery have emerged, notably through demineralization processes to obtain demineralized whey.

Demineralized whey, whether liquid or powdered, is now the main component of infant and dietary products, in particular breast milk substitutes.Demineralized whey also has other applications, for example as a substitute for skimmed milk in confectionery or in the manufacture of reconstituted milk.

The most effective whey demineralization processes currently are electrodialysis and ion exchange, which are applied separately or in combination. Electrodialysis is an electrochemical technique that allows the selective removal of ions from a solution in the form of ionized salts by electrostatically scattering them through permeable membranes and migration to the ions.

Ion exchange is a technique based on the principle of ionic equilibrium between a solid and liquid phase and involves the phenomena of absorption and exclusion. Thus, according to this technique, the ionic equilibrium between a resin as a solid phase and the whey to be demineralized as a liquid phase is used, the ions being absorbed on the resin of the same nature during the saturation phase, and then the resins are then regenerated.

However, on an industrial scale, whey demineralization processes generate very large amounts of effluent, including saline effluent.

The management of these effluents is a crucial problem in the context of reducing the environmental impact of processes. e liquid waste, which belongs to the category of Special Industrial Waste (SWI), has difficulties in treatment which have led manufacturers to use, in particular, external companies specialised in the management of this type of waste.

The practice has some advantages but some problems: beyond the purely economic aspect of the cost of treatment, the storage and transport of these effluents present a significant risk to the environment; furthermore, treatment away from the production site prohibits recycling.

In addition, the presence of salts significantly reduces the effectiveness of treatments used to allow the release of these demineralization effluents into the natural environment, such as biological or physicochemical treatments.

Another solution implemented by industry is to send effluents to treatment plants, but this practice also raises cost and environmental concerns.

EP0115992A1 describes a process for the treatment of brine resulting from electrodialysis demineralization, containing noble products and ionizable salts, characterised by subjecting the brine to a de-ionization operation using an appropriate ion exchange resin and reverse osmosis separating the noble products from the solution.

There is therefore a need to develop processes for treating all or part of the demineralization effluents in order to limit both the environmental impact and the risks and costs of transport and storage of these effluents.

The purpose of the present invention is therefore to provide a process for treating demineralization effluents in order to reduce their environmental impact.

The applicant is therefore to be commended for finding that this objective could be achieved by means of a particular treatment process which could be directly implemented at the industrial site for the demineralization of whey.

A first subject matter of the invention relates to a process for the treatment of whey demineralization effluents.

The present invention thus concerns a process for the treatment of whey demineralization effluents comprising the following steps: (i) supply of a whey demineralization effluent, (ii) reverse osmosis treatment of the recovered effluent at step (i) to obtain a reverse osmosis permeate and retention, (iii) neutralization of the reverse osmosis retention at pH 6 to 9.iv) nanofiltration treatment of the neutralized reverse osmosis retention to obtain a nanofiltration permeate comprising mainly monovalent ions and a nanofiltration retention comprising mainly divalent ions, (v) bipolar membrane electrodialysis treatment of the basic nanofiltration permeate at step (iv) to separate at least one acid solution and at least one base solution.

The first step of the process is therefore a step (i) of supply of whey demineralization effluent.

For the purposes of this invention, demineralization effluents are liquid residues from the demineralization of whey, other than demineralized whey as such, and may thus be effluents from the demineralization of whey by electrodialysis and/or ion exchange.

According to a particular manufacturing method, these are effluents from the demineralization of whey by electrodialysis, these effluents being also known as brine.

Step (ii) of the process of the invention consists of reverse osmosis treatment of the effluents supplied in step (i) to obtain a reverse osmosis permeate and retention.

Reverse osmosis is a process known to the trade which allows the separation into the liquid phase by permeation through semi-selective membranes under the effect of a pressure gradient. The flow is continuous tangentially to the membrane.

The process of the invention allows the concentration of the whey demineralization effluent by means of a retentate and a permeate.

The reverse osmosis step may be carried out until a volume concentration factor (FCV) in the retentate is reached between 3 and 5. Preferably, reverse osmosis may be carried out until a FCV in the retentate is approximately equal to 4.

The resulting reverse osmosis retention can have an ash content of 3-7%, preferably 4-6%. For the purposes of the present invention, ash means the product resulting from the incineration of the dry material of the retention.

The process then includes a step (iii) of neutralisation of reverse osmosis retention at pH 6 to 9.

In a first variant of this step, the reverse osmosis retentate is neutralized at a pH between 6.5 and 9. According to this variant, the neutralization of the retentate results in the formation of di- and tricalcium phosphate which precipitates in the form of crystals. Indeed, the inventors found that from a pH of 6.5, a precipitation is obtained regardless of the basic solution used for neutralization. A mechanical separation step can then advantageously be implemented to eliminate the precipitation of di- and tricalcium phosphate and thus limit the fouling and deterioration of the membranes during the subsequent separation step.

In a second variant of this step, reverse osmosis retention is neutralized at a pH of 6 to 6.4 and the implementation of a mechanical separation step is not necessary because the phosphates are mainly in soluble mono and dicalcium forms which remain apparently soluble.

The fourth step (iv) of the process then consists of nanofiltration of the reverse osmosis neutralized retentate of the whey demineralization effluent to separate the monovalent ions from the bivalent ions and also to remove the majority of residual organic matter such as organic acids, peptides, amino acids or lactose.

Nanofiltration is also a technique known to the trade, a method of separating compounds in a liquid by using a semi-permeable membrane with pores ranging in diameter from 1 to 10 nm.

According to this step iv) of the treatment process, the neutralised retentate obtained in step iii) is treated by means of nanofiltration to obtain a nanofiltration permeate comprising mainly monovalent ions and a nanofiltration retentate comprising mainly divalent ions.

The nanofiltration step can be carried out until a volume concentration factor (FCV) in the retentate is reached between 2 and 4.

According to a particular method of production, the retentate containing divalent ions is advantageously recovered in animal feed.

Finally, the fifth step (v) of the process consists of treating the nanofiltration permeate containing mainly monovalent ions obtained in step (iv) by means of bipolar membrane electrodialysis to obtain at least one acid solution and at least one basic solution.

Bipolar membrane electrodialysis, or bipolar electrodialysis, is a technique known to the professional that allows, unlike conventional electrodialysis, to dissociate H+ and OH- ions in solution and thus convert saline solutions into acids and bases.

This step of bipolar electrodialysis is carried out until a permeate conductivity of 0,2 mS/cm to 1,2 mS/cm is obtained.

The process according to the invention thus makes it possible to treat demineralization effluents and to obtain acid and basic solutions which can be advantageously used for other industrial applications.

A second subject matter of the invention concerns a process for the demineralization of whey and the treatment of the effluent produced, comprising the following steps: (a) supply of whey, (b) acidification of whey at a pH of 2.0 to 3.5, (c) electrodialysis of acidified whey, (d) recovery of the electrodialysis brine from step (c) and implementation of a process for treating the demineralization effluent of the invention, the said demineralization effluent from step (i) being the said electrodialysis brine.

According to the present invention, the whey can be either a soft whey or an acid whey.

In the context of the present invention, sour whey may be the liquid obtained by coagulation of milk by acidification caused by the metabolism of lactic acid bacteria. Lactose: 4.0 - 5.0% protein: 0.6 - 0.7% mineral salts (mainly Na+, K+ and Ca2+): 0.7 - 0.8% fat: 0.05 - 0.1% dry matter content (total dry extract): 5.3 - 6.0% acidity: pH 4.3 - 4.6

In the context of the present invention, sweet whey refers to the liquid obtained after casein is coagulated by the rennet during cheese making. As mentioned above, sweet whey is a known by-product of the cheese industry. Lactose: 4.0 - 5,0 %protein: 0.6 - 0.8 %mineral salts (mainly Na+, K+ and Ca2+): 0.4 - 0.6 %fat: 0.2 - 0.4 %dry matter content (total dry extract): 5.3 - 6.6 %acidity: pH 5.9 - 6.5

Depending on the preferred method of manufacture, the whey provided is a soft whey. Depending on this method of manufacture, the soft whey may be in raw or concentrated form. Likewise, it may also be a whey reconstituted from a whey powder.

According to a variant of this preferred method, soft whey is a concentrated soft whey, which is advantageously concentrated thermally under moderate heating conditions to a dry extract of 18 to 25%. Preferably, soft whey has a dry extract of 18 to 23%, and especially about 20%, of dry extract. Whey can also be defined by its conductivity characteristics and ash content. According to this method, the concentrated whey supplied has a conductivity of 13.5 to 14.5 μS/cm at 20 °C and an ash content of 7.8 to 8.4%.

Step (b) of the process consists of acidifying the supply of whey. Acidification is carried out in such a way as to reduce and maintain the pH of the whey at a value of 2.0 to 3.5. Preferably, the pH of the whey is lowered and maintained at a value of 2.5 to 3.2, and preferably again at a value of approximately 3. Acidification can be achieved by means known to the professional such as the use of a solution of hydrochloric acid (HCl).

This acidification of whey has several advantages, notably for the efficiency of electrodialysis. On the one hand, efficiency is increased because the low pH promotes ionization of the divalent and trivalent salts present in whey and thus increases, for example, the availability of calcium or magnesium. On the other hand, it lowers the viscosity of whey and leads to a better passage of ions through the electrodialysis membranes. As a result, membrane fouling is reduced and their shelf life is increased. Furthermore, maintaining the pH of the whey at a high pH between 3.5 and 2 ensures the thermal stability of the proteins by preventing their flocculation and deminaturation during a desaturation stage. This is also of particular interest for the thermal pH of the whole whey, including the nutritional value of the protein.

Finally, the maintenance of acid conditions according to the invention in the demineralization process is also advantageous in that it reduces the consumption of water and chemicals.

Depending on the particular method of manufacture, the process may also include a step (b) of pasteurisation of acidified whey before the demineralization step (c). Pasteurisation significantly reduces the number of microorganisms present in whey, and in particular eliminates the most resistant germs, such as spore-forming and heat-resistant germs, without altering the proteins. This pasteurisation step is carried out at a temperature of 90°C to 125°C and for a duration of 5 seconds to 30 minutes.

Next, step (c) of the whey demineralization and product treatment process consists of an electrodialysis step of the acidified whey to produce a dilute and a concentrate.

The dilute refers to the demineralized whey, while the concentrate refers to the concentrated solution of salts, also called demineralization effluent or brine.

Electrodialysis in this step, known as conventional electrodialysis, is a technique known to the professional that can be performed for example as shown in Figure 1. The electrodialyser consists of compartments separated from each other by alternating anionic and cationic membranes. One compartment contains the whey to be demineralized while the other contains water acidified at a pH of 1.5 to 3.5. When the electric field on both sides of the electrodialyser is applied by means of electrodes, the cations dissolve out of the first compartment by crossing the cationic membrane and are blocked in the second compartment by the cationic membrane. The anions also migrate into the second compartment and are blocked in the first compartment.

This electrodialysis step may be performed at a temperature of 30°C to 60°C, preferably 35°C to 55°C, and preferably 40°C to 50°C. For example, this electrodialysis step may be performed at a temperature of about 45°C.

The electrodialysis step is carried out until the desired demineralization rate is reached, i.e. for this step a demineralization rate of at least 70%, at least 75%, at least 80%, at least 85%, and most notably a demineralization rate of about 90%.

The expression demineralization rate represents the ratio of the quantities of mineral salts removed from the whey (i.e. the difference between the quantities of mineral salts in the starting whey and the residual quantities in the demineralized whey) to the quantities of mineral salts in the starting whey, reduced to the same percentages of dry matter.

The rate of demineralization of whey can be estimated by the user through conductivity. In addition, the ash rate of demineralized whey can also be an indicator of the rate of demineralization achieved. For the purposes of the present invention, ash means the product resulting from the incineration of the dry matter of whey. According to the present invention, the ash rate is determined according to NF 04-208.

The electrodialysis step can thus be carried out to obtain a conductivity of concentrated acidified whey at 20% dry extract of between 2,0 and 3,0 mS/cm and/or an ash content of between 2,2% and 2,6%/dry extract, corresponding to a demineralization rate of approximately 70%.

Depending on the particular method of execution, electrodialysis is carried out in such a way as to obtain a conductivity of concentrated whey at 20% dry extract of between 1.0 and 1.5 mS/cm and/or an ash content of between 0.6 and 1.2%/dry extract, which corresponds to a demineralization rate of about 90%. To this end, when the conductivity of the acidified whey reaches between 2.0 and 3.0 mS/cm during electrodialysis, the latter must be paused until the whey is neutralized at a pH of between 6 and 7.

Depending on the particular method of manufacture, the process of whey demineralization and treatment of the resulting effluents includes a step (e) of recovery of the demineralized whey.

The brine from the electrodialysis thus produced in step (c) is then recovered and used in the process of treatment of the demineralization effluent of the invention as defined above.

Thus, the recovered brine is the whey demineralization effluent supplied in step i. In summary, the whey demineralization process and the treatment of the resulting effluents comprise the following steps: (a) supply of whey; (b) acidification of whey at a pH of 2.0 to 3.5; (c) electrodialysis of acidified whey; (d) recovery of the electrodialysis brine from step (c) and implementation of a process for the treatment of demineralization effluents comprising the following steps: (ii) reverse osmosis treatment of the electrodialysis brine to obtain a reverse osmosis permeate and retention, (iii) neutralization of the reverse osmosis retention at a pH between 6 and 9, (iv) nanofiltration of the neutralized reverse osmosis retention to obtain a nanofiltration permeate comprising mainly monovalent ions and a nanofiltration retention comprising mainly divalent ions, (v) bipolar membrane electrodialysis treatment of the nanofiltration permeate obtained in step iv) to separate at least one acid solution and at least one base solution.

In a particularly advantageous way, the whey demineralization and effluent treatment process also includes a recycling step of all or part of the reverse osmosis permeate from step ii) as process water for step c) of the acidified whey or soft whey electrodialysis.

Another particularly advantageous embodiment is the whey demineralization and effluent treatment process, which also includes a recycling step of all or part of the separated acid solution after bipolar membrane electrodialysis after step v for whey acidification after step b.

In another particularly advantageous embodiment, the whey demineralization and effluent treatment process also includes a recycling step of all or part of the separate basic solution after bipolar membrane electrodialysis after step (v) for reverse osmosis retreat neutralisation after step (iii) and/or for neutralisation of the demineralized whey produced at step (c) of electrodialysis.

For the purposes of this invention, the expression process water is considered to be synonymous with brine unless the context clearly indicates that this is not the case.

As mentioned above, the quantities of brine produced on an industrial scale through the demineralization of whey are very large. The process of the invention thus allows for the treatment of these effluents, the limitation of their environmental impact and the generation of solutions that can be used in the whey demineralization process itself. This also has the advantage of reducing the cost of whey demineralization since some of the process water for electrodialysis comes from the treatment of the effluent generated. The process of the invention allows for a reduction in the total amount of effluent sent to the effluent treatment plant.

A third subject matter of the invention relates to a suitable facility for the implementation of the process of whey demineralization and effluent treatment according to the invention as defined above.

Such an installation shall include: a first electrodialysis equipment comprising a first intake for whey, a second intake for process water, a first outlet for demineralized whey and a second outlet for demineralization effluent,an effluent treatment system comprising: a reverse osmosis equipment comprising a first inlet for demineralization effluent connected to the second outlet of the electrodialysis equipment, a first outlet for the reverse osmosis permeate, and a second outlet for reverse osmosis retention,a neutralisation equipment comprising a first inlet for reverse osmosis retention connected to the second outlet of the reverse osmosis equipment,a second inlet for a neutralising solution, and an outlet for a neutralised reverse osmosis retent,a nanofiltration equipment comprising a neutralised reverse osmosis retent inlet connected directly to the neutralising equipment output or indirectly via a mechanical separation equipment, a first outlet for the neutralised nanofiltration retent and a second outlet for the nanofiltration permeate,a second bipolar membrane electrodialysis equipment having an inlet for the nanofiltration permeate and connected to the second outlet of the basic filtration equipment, a first outlet for an acid solution, a second outlet for a solution,- What? the waste water treatment system comprising all or part of the following means of recycling: a means connecting the first output for the reverse osmosis permeate of the reverse osmosis equipment to the second input of the first electrodialysis equipment and/or,a means connecting the first output for an acid solution of the second bipolar membrane electrodialysis equipment to the second input of the first electrodialysis equipment and/or,a means connecting the second output for a basic solution of the second bipolar membrane electrodialysis equipment to the second input for a neutralisation solution of the first neutralisation equipment and/or to the output for a demineralised lactoserum of the first electrodialysis equipment.

The first electrodialysis equipment allows the implementation of step (c) of the process of the invention in such a way as to demineralize the whey to the desired rate of demineralization. This equipment includes a first input for receiving the whey, a second input for receiving the process water solution, a first output for the demineralized whey and a second output for the brine or demineralization effluent. Process water is the water used to feed the electrodialyser. This water in electrodialysis constitutes the demineralization effluent as described above.

The plant of the invention also includes a treatment system for the treatment of brine produced by the demineralization of whey by means of a series of equipment.

The treatment system thus includes a reverse osmosis equipment. This equipment enables the implementation of step (ii) of the process of the invention in such a way as to generate from the brine a reverse osmosis permeate and a reverse osmosis retentate. The reverse osmosis equipment includes a first inlet for the demineralization effluent connected to the second outlet of the electrodialysis equipment, a first outlet for the reverse osmosis permeate, and a second outlet for the reverse osmosis retentate connected to the neutralisation equipment.

The neutralisation equipment allows the implementation of step (iii) of the process of the invention and neutralises the reverse osmosis retentate before it is processed by a nanofiltration equipment, comprising a first input for reverse osmosis retentate connected to the second reverse osmosis equipment outlet, a second input for a neutralisation solution and an output for neutralised reverse osmosis retentate connected to a nanofiltration or mechanical separation equipment.

This neutralisation equipment allows the pH of the reverse osmosis retentate to be neutralised from 6 to 9. In the case where the pH is neutralised from 6 to 6.4, the output of the neutralisation equipment can be directly connected to the first input of the nanofiltration equipment. However, in the case where the pH is neutralised from 6.5 to 9, the output of the neutralisation equipment is connected to a mechanical separation equipment in order to remove the precipitate of tricalcium phosphate from the retentate.

The mechanical separation equipment thus comprises an input for the neutralised reverse osmosis retentate and an output for the tricalcium phosphate-free separation surgeant.

The nanofiltration equipment enables the implementation of step iv) of the treatment process of the invention to obtain a nanofiltration permeate comprising mainly monovalent ions and a nanofiltration retentate comprising mainly divalent ions. This equipment includes an input for neutralized reverse osmosis retentate directly connected to the output of the neutralization equipment or the output of the mechanical separation equipment, a first output for the neutralized nanofiltration retentate and a second output for the nanofiltration permeate.

Finally, the treatment system includes a bipolar membrane electrodialysis equipment to implement step v) of the invention, which is similar to the first electrodialysis equipment except that it also contains bipolar membranes and thus allows acid and base solutions to be obtained from a saline solution due to the dissociation of H+ and OH+ ions.

The device of the invention is particularly advantageous in that the treatment system also includes one or more recycling media, such as a first recycling medium which can connect the first output of the reverse osmosis equipment to the second input of the first electrodialysis equipment, which allows all or part of the reverse osmosis permeate generated by the reverse osmosis equipment to be recycled as process water at the level of the electrodialysis equipment.

A second recycling medium may connect the first output of the bipolar membrane electrodialysis equipment with the second input of the first electrodialysis equipment, thus allowing all or part of the acid solution generated by the bipolar membrane electrodialysis equipment to be recycled for acidification of the whey in step (b) of the whey demineralization and effluent treatment process.

Finally, a third recycling medium may connect the second output of the bipolar membrane electrodialysis equipment with the second input of the neutralisation equipment and/or the first output for a demineralized whey from the first electrodialysis equipment. This third medium allows all or part of the basic solution generated by the bipolar membrane electrodialysis equipment to be recycled for the neutralisation of reverse osmosis retention in the neutralisation equipment and/or for the neutralisation of the whey at the end of the demineralization.

The following examples will help to understand the invention better, which are purely illustrative and do not in any way limit the scope of protection.

Examples Example 1

The purpose of this example is to implement the process of treatment of demineralization effluent according to the invention.

A. Supply of demineralization effluent:

The effluent treated in this example is brine from the demineralization of a soft whey with the ion concentrations and characteristics shown in Table 1 below: - What? Tableau 1.1

Extrait sec (%)	21,8
pH	6,7
Conductivité (mS/cm)	20,28

The pH of the recovered brine is 2,4 and the ion concentrations are as shown in Table 1.2 below: - What? Tableau 1.2

P	Cendres (%)
Concentrations (mg/100g liquide)	674	163	62	13	808	77	1,9

B. Treatment of brine generated by the demineralization of sweet whey Reverse osmosis is the same as in the case of the

The brine obtained from the demineralization of soft whey is treated by reverse osmosis in step (b) of the process of the invention. Reverse osmosis is carried out from 40 L of brine until a volume concentration factor (FCV) in the retentate is obtained equal to 4.

The characteristics of reverse osmosis are given in Table 1.3 below: - What? Tableau 1.3

Membrane	AG 1812 (GE Membranes)
Pression cible (bar)	30
Débit (L/h)	900
Volume initial (L)	40
FCV visé	4
Volume final rétentat (L)	10
Volume final perméat (L)	30
Température	45°C

The COD, dry extract percentage, ash content, pH and the concentrations (mg/100 g) of the various ions in the retentate were measured at different VOCs up to the target VOCs are shown in Table 1.4 below: - What? Tableau 1.4

FCV	K	Na	Ca	Mg	Cl	P	DCO	ES %	Cendres %	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

This reverse osmosis step is repeated twice under the same conditions to obtain an additional 20 litres of retent and thus bring the total volume of the reverse osmosis retent to 30 litres.

Nanofiltration:

The reverse osmosis retentate is then neutralized at 20°C to pH 7 with a 40% by weight NaOH solution and a precipitate of tricalcium phosphate is formed.

The 30 litres of reverse osmosis retention are then settled for 12 hours and 21 litres of surfactant are obtained.

Nanofiltration is carried out until a volume concentration factor of 3 is obtained in the nanofiltration permeate. - What? Tableau 1.5

Membrane	DK 1812 (GE Membrane)
Pression cible (bar)	25
Débit (L/h)	900
Volume initial (L)	21
FCV visé	3
Volume final rétentat (L)	10
Volume final perméat (L)	20
Température	20°C

Nanofiltration of 21 L of supernatant yields 14 L of nanofiltration permeate containing only monovalent ions such as K+ and Na+.

The COD, dry extract percentage, ash content (%), pH and concentrations (mg/100 g) of the various ions in the permeate were measured and are shown in Table 1.4 below: - What? Tableau 1.6

FCV	K	Na	Ca	Mg	Cl	P	DCO	ES	Cendres	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

The electrodialysis on bipolar membrane:

The nanofiltration permeate is then treated by electrodialysis on bipolar membrane.

The first step starts with a volume of 7L of permeate in the feeding compartment, 5L of water in the acid compartment, and 5L of water in the base compartment.

Electrodialysis is initiated to reduce the permeate conductivity from 50 mS/cm to less than 0.5 mS/cm.

Once the conductivity of 0.5 mS/cm is reached, a second step is carried out with 7 new litres of permeate in the feeding compartment.

At the end of electrodialysis, the final measured permeate conductivity is 1,1 mS/cm, the acid solution is 1,08 mol/L and the basic solution is 0,87 mol/L.

The values of the permeate conductivities are given in Table 1.7 below: - What? Tableau 1.7

Conductivité (mS/cm)
50,0
0,51
50,0
1,09

The following are the concentrations in acid and basic solution obtained at the end of steps 1 and 2: - What? Tableau 1.8

	Unité	Acide	Base
Etape 1		0,61	0,43
	% massique d'HCl	2,2	3,9
Etape 2		1,08	0,87
	% massique de NaOH	1,7	3,5

Finally, the following table 1.9 shows the mineral compositions (mg/100 g liquid) of the acid and base solution at the end of each step: Tableau 1.9

		K	Na	Ca	Mg
Etape 1	Solution Acide	22	87	4,4	1,3
	Solution Basique	6	705	5,9	0
Etape 2	Solution Acide	229	201	5,3	1,4
	Solution Basique	2006	1208	5,2	0

At the end of bipolar electrodialysis, the molar ratio of potassium to sodium concentrations in the basic solution is 49/51 (K/Na).

The process according to the invention thus allows the brine resulting from the demineralization of whey to be treated to obtain, inter alia, acid and basic solutions which can be reused for other applications.

Example 2:

The purpose of this example is to implement the process of whey demineralization and effluent treatment of the invention from a whey other than that of example 1.

A. Production of whey demineralization effluent:

The soft whey used for demineralization has the ion concentrations and characteristics shown in Table 2.1 below: - What? Tableau 2.1

Extrait sec (%)	23,0
pH	6,2
Conductivité (mS/cm)	22,05

The soft whey is then acidified at the beginning of demineralization to pH 3 with an acid solution produced in example 1.

From 19.7 L of whey, a first electrodialysis step is carried out until a whey conductivity of about 3 mS/cm is obtained.

The whey is then neutralised to pH 6,2 with the basic solution produced in example 1, and a second electrodialysis step is performed until the whey conductivity is reduced to about 1,6 mS/cm.

Ion concentrations (mg/100 g dry extract) in the whey at the beginning and end of electrodialysis (ED) are given in Table 2.2 below: - What? Tableau 2.2

K	Na	Ca	Mg	Cl	P	Cendres (%)
Concentration début ED	2692	700	600	117	3878	570	8,48
Concentration fin ED	203	181	240	66	42	222	1,61

The brine circuit of the electrodialyser initially contains 20 L of process water which is not changed between the two electrodialysis steps.

The ion concentrations in brine were measured at the beginning and end of electrodialysis as follows: - What? Tableau 2.3

K	Na	Ca	Mg	Cl	P	Cendres (%)
début d'électrodialyse (en mg/100g liquide)	0	3	8	0	3	1	0,54
fin d'électrodialyse (en mg/100g liquide)	610	203	71	13	823	74	1,89

B. Recycling of brine from whey demineralization Reverse osmosis is the same as in the case of the

As in example 1, reverse osmosis is performed from 40 L of brine until a volume concentration factor (FCV) in the retentate is equal to 4. 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 to obtain an additional 20 L of retentate.

The characteristics of reverse osmosis are identical to those of example 1.

The concentrations (mg/100 g) of the various ions in the retentate measured at different FCVs: - What? Tableau 2.4

FCV	K	Na	Ca	Mg	Cl	P	DCO	ES	Cendres %	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

Nanofiltration:

The reverse osmosis retentate is then neutralized to pH 8.6 with a KOH/NaOH solution at 0.5M of KOH and 0.5M of NaOH reconstituted from the basic solution obtained in example 1.

The reverse osmosis retentate is then settled for 12 hours and 17 L of surfactant is obtained.

Nanofiltration is carried out until a volume concentration factor of 3 is obtained in the nanofiltration permeate.

The ion concentrations in the nanofiltration retentate are given below: - What? Tableau 2.5

FCV	K	Na	Ca	Mg	Cl	P	DCO	ES %	Cendres %
1,0	80 7	392	1	0	1219	1	2	2,7	2,50
1,5	10 64	496	1	0	1540	1	/	3,4	3,17
Global (3)	98 9	465	1	0	1639	1	4	3,2	3,07

Nanofiltration of 17 L of supernatant yields 11.5 L of nanofiltration permeate containing only monovalent ions such as K+ and Na+.

The electrodialysis on bipolar membrane:

The nanofiltration permeate is then treated by bipolar membrane electrodialysis according to the same protocol as in example 1, by a two-step treatment.

The first step starts with a volume of 5.5L of permeate in the feeding compartment, 5L of water in the acid compartment, and 5L of water in the base compartment.

Electrodialysis is initiated to reduce the permeate conductivity from 50 mS/cm to less than 1 mS/cm.

The second step is carried out with 5.5 new litres of permeate in the feeding compartment. The acid and base solutions produced are, however, unchanged to allow their concentration. The conductivity target for the feeding is the same as for the first step, i.e. a conductivity of less than 1 mS/cm.

At the end of electrodialysis, the final measured permeate conductivity is 0,7 mS/cm, the acid solution is 0,69 mol/L and the basic solution is 0,64 mol/L.

The values of the permeate conductivities are given in Table 2.6 below: - What? Tableau 2.6

Conductivité (mS/cm)
50,0
0,7
46
0,7

The following are the concentrations in acid and basic solution obtained at the end of steps 1 and 2: - What? Tableau 2.7

	Unité	Acide	Base
Etape 1		0,34	0,32
	% massique d'HCl	1,2	1,3
Etape 2		0,69	0,64
	% massique de NaOH	2,5	2,6

Finally, the following table 2.8 shows the mineral compositions (mg/100 g liquid) of the acid and base solution at the end of each step: Tableau 2.8

		K	Na
Etape 1	Solution Acide	37	33
	Solution Basique	604	332
Etape 2	Solution Acide	67	46
	Solution Basique	1308	658

At the end of bipolar electrodialysis, the molar ratio of potassium to sodium concentrations in the basic solution is 54/46 (K/Na).

The process of the invention thus allows whey to be demineralized and brine to be treated in order to obtain, inter alia, acid and base solutions which can be reused in the process of demineralization as such, thus limiting discharges to the treatment plant.

Example 3

The purpose of this example is to show a suitable installation for the implementation of the process of the invention, which is shown schematically in Figure 2 and includes: a first ED equipment comprising a first inlet 11 for receiving whey, a second inlet 12 for receiving process water, a first outlet 13 for demineralized whey and a second outlet 14 for demineralization effluent,an effluent treatment system comprising: a reverse osmosis equipment OI comprising an input 21 for the demineralization effluent connected to the second output 14 of the electrodialysis equipment, a first output 22 for the reverse osmosis permeate,and a second output 23 for reverse osmosis retentate,an NL neutralisation equipment comprising a first input 31 for reverse osmosis retentate connected to the second output 23 of the reverse osmosis equipment, a second input 32 for a neutralisation solution, and an output 33 for neutralised reverse osmosis retentate,an NF nanofiltration equipment comprising an input 51 for neutralised reverse osmosis retentate connected directly to the output 33 of the neutralisation equipment, a first output 52 for neutralised nanofiltration retentate and a second output 53 for the nanofiltration permeate,a second membrane dipole electrodialysis equipment comprising an input 61 for nanofiltration and an EDBP 53 connected to the second nanofiltration equipment,a first output 62 for an acid solution, a second output 63 for a basic solution, that system comprising recycling facilities comprising all or part of the following: a medium R1 connecting the first outlet 22 for the reverse osmosis permeate of the reverse osmosis equipment to the second outlet 12 of the first ED ED equipment to receive the process water and/or,a medium R2 connecting the first outlet 62 for an acid solution of the second EDBP bipolar membrane electrodialysis equipment to the second outlet 12 of the first EDBP electrodialysis equipment and/or,a medium R3 connecting the second outlet 63 for a basic solution of the second EDBP bipolar membrane electrodialysis equipment to the second outlet 42 of the NL neutralisation equipment and/or to the first outlet 13 of the EDBP electrodialysis equipment.

In the case of neutralisation at a pH of 6,5 to 9, the output 33 for the neutralised reverse osmosis retentate of the neutralisation equipment NL shall be connected by a conduit to the input 41 of the mechanical separation equipment, and the output 42 of the same equipment shall be connected by a conduit to the input 51 of the nanofiltration equipment.

In the case of continuous operation, the connections and means of connection between the various inputs and outputs of the equipment shall be provided by pipes.

Nomenclature of the figures:

A: AnodeC: CathodeSP: Mechanical separation equipmentE.EDP: process water inputE.LS: whey inputED: electrodialysis equipmentEDBP: bipolar membrane electrodialysis equipmentLS: LactoserumLSD: demineralized wheyMA: anionic membraneMC: cationic membraneNF: nanofiltration equipment: neutralisation equipmentOI: reverse osmosis equipmentP.OI: reverse osmosis permeateR.NF: nanofiltration retentionS.Ac: acidic solutionS.Ba basic solution.LSD: de-mineralized wheyS.NI: neutralisation solutionS.NL:

Claims (10)

1. 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,

   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.
2. Method according to claim 1, wherein the whey demineralization effluent is a brine from electrodialysis of whey, preferably of sweet whey.
3. Method according to claims 1 or 2, wherein step ii) is carried out so as to obtain a concentration factor (CF) of 3 to 5 in the retentate.
4. Method according to one of claims 1 to 3, 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.
5. Method according to one of claims 1 to 4, 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.
6. 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 one of claims 1 to 5, said demineralization effluent in step i) being said electrodialysis brine.
7. Method according to claim 6, wherein it further comprises 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).
8. Method according to claims 6 or 7, wherein it further comprises 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).
9. Method according to one of claims 6 to 8, wherein it further comprises 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.
10. Facility suitable for demineralizing whey and for treating the effluents produced, said facility comprising:

    - a first electrodialysis (ED) device 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,

    - an effluent treatment system comprising:

    - 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,

    - 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,

    - a nanofiltration device (NF) comprising an inlet (51) for the neutralized reverse osmosis retentate connected directly to the outlet (33) of the neutralization device or indirectly via a mechanical separation device, a first outlet (52) for theneutralized nanofiltration retentate, and a second outlet (53) for the nanofiltration permeate,

    - 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,

    said system comprising recycling means comprising all or part of the following means:

    - a means (R1) connecting the first outlet (22) for the reverse osmosis permeate of the reverse osmosis device (OI) with the second inlet (12) of the first electrodialysis device (ED) intended to receive the process water, and/or

    - 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 (ED), and/or

    - 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 (42) of the neutralization device (NL) and/or with the first outlet (13) of the first electrodialysis device (ED).