PROCEDE DE TRAITEMENT DE PETIT LAIT

METHOD TO TREAT WHEY

Abrégé français

Du petit lait pasteurisé est soumis à une micro-filtration ou à une nano-filtration. L'ultrafiltrat est ensuite traité par osmose inverse et stérilisé ou pasteurisé. Le rétentat est soumis à une électrodialyse et l'eau salée obtenue est traitée par micro-filtration ou nano-filtration. Il est possible de soumettre cette eau salée à une phase de précipitation avant de passer à la micro-filtration ou à la nano-filtration. Il est possible de réutiliser l'eau chimiquement pure issue du traitement susmentionné comme eau de traitement ou de la recueillir dans un récipient.

Abrégé anglais

Pasteurised whey is subjected to micro- or nanofiltration. The permeate is
further treated with reverse osmosis and sterilised or pasteurised. The
retentate is subjected to electrodialysis and the salty water formed is
treated with micro- or nanofiltration. The salty water can be subjected to a
precipitation step before the micro- or nanofiltration. The pure water that is
a result of the treatment above can be reused as process water or drained to a
recipient.

Revendications

6
CLAIMS:
1. A method for treating whey in the field of milk processing industry and in
particularly in cheese production, in which method the separated whey is led to
pasteurizing unit (1), from the pasteurizing unit to nano- and/or microfiltration unit
(2), from where the retentate of the whey is transferred to further processing and
the permeate is led elsewhere, characterized in that the permeate is led to
additional reverse osmosis filter (4) and/or to a second reverse osmosis filter (15)
and/or to a third reverse osmosis filter (22) at later stage of the process, so that the
permeate is treated by means of reverse osmosis filter(s) as to purify it, and that
the resulting technically/commercially clean water is mixed with condensation
water.
2. A method as claimed in claim 1, characterized in that the permeate is
sterilized by UV light (5) after the additional reverse osmosis filter (4) and/or the
additional reverse osmosis filter (15) and/or the additional reverse osmosis filter
(22).
3. A method as claimed in claims 1 and/or 2, characterized in that the permeate
is pasteurized (6) after the additional reverse osmosis filter (4) and/or the
additional reverse osmosis filter (15) and/or the additional reverse osmosis filter
(22).
4. A method as claimed in one or several of claims 1 to 3, characterized in thatthe permeate is led to water tanks (7,8) and further into process use.
5. A method as claimed in one or several of claims 1 to 4, where the retentate part
of the whey is led from the nano- and/or microfiltration unit (3) to a heat
exchanger, is heated by heat exchanger (9), and it is centrifugalized by centrifuge
(10) and then led to storage (11), characterized in that the retentate is led from
the storage to electrodialysis unit (12), where it is treated by electrodialysis so as
to reduce the salinity of the whey, and the saliferous water is led through
intermediate tank (13) to nano- and/or microfilter unit (14), preferably to a
nanofilter unit, and from there to reverse osmosis filter (15).
6. A method as claimed in claim 5, characterized in that the saliferous water isled from intermediate tank (13) to precipitation tank (16), where it is precipitated

7
by adding sodium hydroxide (NaOH), and the resulting solution is centrifugalizedby centrifuge (17), and the resulting solution is led to intermediate tank (18) while
the resulting calcium phosphate deposit is led to another tank (19).
7. A method as claimed in claim 6, characterized in that from the intermediate
tank (18) the solution is led to nano- or microfiltration unit (21), and the resulting
permeate is led to additional reverse osmosis filter (22), the resulting clean water
is led to electrodialysis unit (12), which allows for the development of a closed
circuit system..
8. A method as claimed in one or several of claims 1 to 7, characterized in thatthe clean water derived from the process is mixed (23) with condensation water,
thereby producing water compatible with environmental requirements which can
be discharged directly into waterways or led to a closed system.

Description

r CA 02244109 1998 07-24 'PCT/ Fl 9 7 / O C 0 6 5
TheSwedish PatentO~ce1997 -09- 0 5
?, PCr International ~rP~ tion
J
METHOD TO TREAT WHEY
It is the object of this invention to provide a method to treat whey, and according
to the said method the separated whey is led to a pasteurizing apparatus, from
s there to a nano- and/or microfiltration unit, where~iom the retentate part of the
whey is ll~rell~d to be further processed and the perrneate part is led elsewhere.
In the processes in foodstuff industry, waste water is created which is purified by
leading it through nano- andlor microfilters. The whey that is created during the
10 processing of milk in the cheese industry is saliferous, and it is led to a filtration
unit for desalination. The permeate flowing out of the filtration unit is also
wa~ w~lel, because its salt content is high. Such wa~l~walel~ are discharged as
sewage e.g. to an industrial or a municipal sewage treatment plant. The prices for
water and wa~k;waler treatment are high, and great costs must be paid for large
amounts of waslt:w~ler even if the wa~ walel~ were a1most clean.
The presently employed processes have an additional disadvantage: the potentially
useful ingredients in the permeate are lost. In such cases, new corresponding
ingredients may have to be bought for the process in order to replace the
ingredients which were discharged as sewage along with the permeate. The
recycling of the permeate back to the process does not at present necessarily yield
satisfactory results, for the recycling may result in non-desired ingredients
plugging the nanofiltration ~p~lus.
It is the objective of this invention to present a method which helps decrease the
~L~oulll of waslt;waLels and to utilize the perme~te and the ingredients therein. It
is a further objective to present a method that can be re~ 1 and employed in a
simple and profitable way. I he aim of the invention is also improve the presently
employed tre~tment and purification methods, so as to make possible a closed
system use water or to essentially lower costs of sewage tre~t~nent and of the use
of water needed ~om outside the industrial plant.
The objective of this invention is attained ll~o~gll the method which is
characterized by what is presented in the appended claims.
According to the invention, the perme~te is treated by leading it to an additional
filter and by purifying it there. Thereafter, the permeate leaving the additionaI
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reverse osmosis filter and/or to a second reverse osmosis filter and/or to a third
reverse osmosis filter at a later stage of the process, so that the peremeate istreated by means of reverse osmosis filter(s) as to purify it, and that the reslllting
technically/commercially clean water is mixed with confl~n~1ion water. By
exploiting reverse osmosis, the salinity can be reduced ap~ro~liately. Thereafter,
the permeate leaving the additional reverse osmosis filter(s) is clean in the
technical sense of the word, and it can be lltili7e~1 at many various phases of the
process e.g. for electrodialysis by leading it back to the process. Both the amount
of ~l~;w~l~, and that of the water introduced to the process can be considerablylO reduced, which results in cost reduction. If, however, it is desired to lead the
perme~te to the sewage system, it is sufficiently clean and it can be led directly
into e.g. a ~Lel w~, at least if the possibly e~i~tin~ bacteria are elimin~te~ first.
From nanofiltration stage, kalium and the other valuable salts and other
ingredients are aquired. In many cases, the lele~ e, e.g. sodium, acquired from
s the additional reverse osmosis filter is useful in other processes and the amount
of ~ngredients to be purchased that are necess~ry for the processes, can be reduced.
The invention can be used at least for purifying the wa~Lew~L~l~ resulting from
foodstuff industry processes and, particularly, for purifying the wastewaters
created in milk processing industry, especially in cheese production
In an additional application of the invention, the permeate is sterilized by UV
light, thereby elimin~tin~ h~....rl.l ingredients and b~t~ This step already exists
at many miLk proces~ing plants.
In a second additional application of the invention, the permeate is pasteurizedafter the additional reverse osmosis filtration. During the pasteurization,
tempelaLu~cs ranging from 75~C to 90~C should plt;rel~bly be reached, thereby
elimin~ting det~imental ingredients. This step already exists at many miLk
processing plants. After cooling the ~esulting liquid can be further led to an
30 electrodialysis apparatus.
One importaIlt addition to the process is that con~lens~tion water is al)p~ iately
mixed with the clean water emitted from the process. E.g. the electroconductivity
values - originally about 300 microS - are considerably improved when the clean
water emitted ~om the process is mixed with con.3enC~tion water whose
electroconductivity may be in the range of about lO microS T~ereby, water
fi~1fillin~ even strict el~vi~ ....ent~1 safety requirements is obtained, which can be
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3 CA 02244109 1998-07-24 PCT/ Fl 9 7 / O O 0 6 5
1997 -09- 0 5
directly discharged into waterways or led to a closed water system..
In the following, the invention is defined in more detail with reference to the
attached drawings, in which
Fig. 1 is a flow diagram showing a set of equipment for applying a method in
accordance with the invention,
Fig. 2 is a flow diagram showing another set of equipment for applying a method
in accordance with the invention, and
Fig. 3 is a flow diagram showing a third set of equipment for applying a method
o in accordance with the invention.
With reference now to Fig. 1, an example of one process covered by the
application is presented. Complying with this method, the saliferous, sepal;ll~dwhey is cooled to a le~ t; under 10~ C, preferably to about 6~C, and the
feed is further led from the process to storage tanlc 1, where from it is led topasteurizing unit 2. In the pasteurizing unit the whey is pasteurized to
e~ s ranging from 70~C to 80~C, preferably to roughly 75~C, wh~leaner
it is cooled to 15 - 25~C, l,lt;rel~ly to a lt;ll~ ; of about 20~C. The saliferous
whey is further led to filtration unit 3, which can be either a nano- or a
microfiltration unit, but l,lt;fel~bly a nanofiltrarion unit. At this stage, the dry
solids content of the permeate is approxirnately 0.3 - 0.5 per cent. The permeate
(temperature about 15 - 25~C) which results after the filtration is further led to the
additional reverse osmosis (RO) filt-.ting eq~npm~nt 4 which purifies the perm-o~te
and produces commercially clean ~=clean in the technical sense of the word)
water. As shown in the diagram, the perme~te derived from RO filter 4 is first
treated by p~ g it in unit 6 and/or it is sterilized by UV irradiation in the
W e~lipm~nt 5. Thereafter the pnrified and cooled pçrm~te can be led to water
tanks 7, 8, where it can be stored and filr~er led to various processing or other
uses, e.g. to an electrodialysis unit or possibly to the sewage system. The perme~te
iS commercially clean water and the measured conductivity value is about 150 -
300 microS. After filter 3, the perme~te may also be led to a separate tank for
saliferous water where it is stored as long as desired. From the storage tank the
perm~o~t~ can be reintroduced e.g. to the salt brine processin~ e.g. to
electrodialysis. It is a preferred solution to mix 23 the clean water reslllting from
3s the process with condens~tion water. The con~1~n~tion water can be led directly
to wale-wa~s or to a closed system.
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With reference now to the application and example in Fig. 2, the tre~tment of the
permeate is for the most part similar to that described above. In this application
also the l~ltl-lale is being treated. The process already exists at meny miLk
processing plant, yet without the reverse osmosis step. In this method, the
~ e flowing from iilter 3, its le~ e being about 20~C, is heated by heat
t xc~n~r 9 to about 35~C-45~C, ~It;r~l~ly to reach a temperature of about 38~C.
The dry solids content of such a l~ qle is about 24 per cent. It should be
mentioned that an evaporator may be used instead of a NF filter. Next, the
retentate is ce~ ifilg~1i7ell by c~ iruge 10 so as to elimin~te crystals, and it is
10 then led to storage tank 11. Next, the ~ , i.e. whey is led to electrodialysis
module 12, where it is des~lin~te~1 The salt content of the whey emitte~l out of this
eqwpment depends on the performance of the des~lin~tion process. The whey is
led away 24 and the resulting saliferous water (dIy solids content 1.1 - 1.3%) is
led to intermediate tank 13 and cooled to reach a le~ )el~lu~e of about 20~C,
5 whereafter it is led to micro- and/or nanofiltration module 14, ~lert;l~bly
nanofiltration is used. The dry solids content of the perme~te is now about 0.3 -
0.5 %, and the perme~t~ is further led to reverse osmosis (RO) filter 15 . The total
number of reverse osmosis filters to be used in the process can be one or more
depçn.1in~ on the desired performance level and amount of permeate to be treated.
Thereafter the permeate is led - as described above - after l)a~ a~ion andlor
UV irradiation to storage tanks 7, 8, where also condensation water may be led.
In an :~11r~ e process, the p~ e is led direcdy from NF 3 to RO filter 4 and
fùrther to storage tanks 7,8 after pasteurization and/or UV-irradiation. Cooling may be necessary.
In the third application and example of the invention the flow of the process ismosdy similar to the example referred to in Fig. 2. In this application the brine
(=saliferous water) is led from intermediate storage tank 13 to precipitation tank
30 16 where it is precil~haled by adding sodium hydroxide (NaOH) and saLiferous
mother liquid. The resnlting solution is C~ irl~g~ e~1 by cent~ ge 17, and the
resulting solution is led to intermediate tank 18, while the resulting calcium
phos~ deposit is led to tank 19. From tank 18 the solution is led to nanofilter
21, wllw~ JIll the resulting pe~n~o~t~ is led to additional reverse osmosis filtOE 22
and filrther in the m~nner described earlier. With such a procedure the calcium and
the phosphate can be recovered and the amount of precipil~ lg ingredients is
reduced, thereby not fouling NF 21 and thus improving its performance and the
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1,
elimin~tion of phosphorus; most of the phosphorus from permeate is discarded
together with the deposit during centrifil~li7~tion.
The invention is not restricted to ~e plt;rell~;d applications presented here; it may
s vary within the general framework and inventional idea incorporated in the
following claims.
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