U.S. patent application number 16/936515 was filed with the patent office on 2021-02-04 for whey preacid treatment of wastewater with high calcium concentration to promote anaerobic digestion and delay calcification.
This patent application is currently assigned to GuangXi University. The applicant listed for this patent is GuangXi University. Invention is credited to Meiling LI, Chen LIANG, Hui LIU, Xinliang LIU, Lianxin LUO, Chengrong QIN, Xueping SONG, Shuangfei WANG, Zhiwei WANG.
Application Number | 20210032138 16/936515 |
Document ID | / |
Family ID | 1000005034755 |
Filed Date | 2021-02-04 |
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United States Patent
Application |
20210032138 |
Kind Code |
A1 |
WANG; Shuangfei ; et
al. |
February 4, 2021 |
WHEY PREACID TREATMENT OF WASTEWATER WITH HIGH CALCIUM
CONCENTRATION TO PROMOTE ANAEROBIC DIGESTION AND DELAY
CALCIFICATION
Abstract
A method may add whey to high calcium papermaking industrial
wastewater blended and pre-acidification treatment to promote
anaerobic reaction and inhibit calcification. The method includes,
before anaerobic treatment of papermaking wastewater, mixing whey
wastewater with the papermaking wastewater. The method also
includes pre-treating the papermaking wastewater by acidification
to stabilize the papermaking wastewater prior to entering an
anaerobic reaction system.
Inventors: |
WANG; Shuangfei; (Nanning,
CN) ; WANG; Zhiwei; (Nanning, CN) ; LIU;
Hui; (Nanning, CN) ; QIN; Chengrong; (Nanning,
CN) ; LIANG; Chen; (Nanning, CN) ; SONG;
Xueping; (Nanning, CN) ; LUO; Lianxin;
(Nanning, CN) ; LIU; Xinliang; (Nanning, CN)
; LI; Meiling; (Nanning, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GuangXi University |
Nanning |
|
CN |
|
|
Assignee: |
GuangXi University
|
Family ID: |
1000005034755 |
Appl. No.: |
16/936515 |
Filed: |
July 23, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C02F 2209/06 20130101;
C02F 2209/02 20130101; C02F 1/66 20130101; C02F 2305/00 20130101;
C02F 1/68 20130101; C02F 2103/28 20130101; C02F 3/28 20130101 |
International
Class: |
C02F 3/28 20060101
C02F003/28; C02F 1/66 20060101 C02F001/66; C02F 1/68 20060101
C02F001/68 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 1, 2019 |
CN |
201910705494.6 |
Claims
1. A method of adding whey to papermaking industrial wastewater
having a calcium ion concentration of at least 800 mg/L and
pre-acidification treatment to promote anaerobic reaction and
inhibit calcification, the method comprising: before anaerobic
treatment of the papermaking industrial wastewater, mixing whey
wastewater with the papermaking wastewater; and pre-treating the
papermaking industrial wastewater by acidification to stabilize the
papermaking wastewater prior to entering an anaerobic reaction
system.
2. The method according to claim 1, the method comprising:
adjusting the volume ratio of whey wastewater to papermaking
industrial wastewater to 1:10-15.
3. The method according to claim 1, the method comprising:
controlling the pre-acidification temperature to 25.degree. C.; and
controlling the pH value to 5.5-6.9.
4. The method according to claim 1, the method comprising:
controlling the hydraulic retention time to 3-4 h, the
pre-acidification treatment is carried out in the pre-acidification
tank.
5. The method according to claim 1, the method further comprising:
controlling the stir speed to 170-200 rpm in a stirring device used
in the acidification pre-treatment.
6. A method for promoting anaerobic digestion and delaying
calcification, the method comprising: mixing whey wastewater with
wastewater from a papermaking plant to enhance the production of a
valuable digestion byproduct comprising of biogas; and pre-treating
the papermaking plant wastewater by acidification to stabilize the
papermaking plant wastewater prior to entering an anaerobic
reaction system.
7. The method of claim 6, wherein the acidification pretreatment
comprises a low and stable pH value, promoting anaerobic reaction
of the papermaking wastewater and inhibiting calcium precipitation
to ensure that the biogas comprises characteristics including
CH.sub.4 and CO.sub.2 content.
8. The method of claim 7, further comprising: after the
pre-treating of the papermaking plant wastewater, precipitating
calcium ions in the papermaking plant wastewater to reduce content
of the calcium ions from the acidification in the papermaking plant
wastewater.
9. The method of claim 7, wherein the whey wastewater provides
nutrients for anaerobic bacteria in the treatment of papermaking
wastewater with a single component, and increases an activity of
the anaerobic reaction system to enhance the production of the
valuable digestion byproduct.
10. The method of claim 7, the method further comprising: add
papermaking plant wastewater to an acidification tank; and adding
whey wastewater from a lower end of the acidification tank through
one or more pipes.
11. The method of claim 10, wherein, a volume ratio of the whey
wastewater and the papermaking plant wastewater to 1:10, 1:12, or
1:15, and a volume of pre acidification tank is 800 m.sup.3 or 1200
m.sup.3, to balance the nutrition of wastewater system.
12. The method of claim 11, wherein the mixing of the whey
wastewater and the papermaking plant wastewater is performed by a
mixing device set in a pre-acidification tank having a rotor speed
of 170, 185, or 200 rotations per minute (RPM).
13. The method of claim 10, further comprising: controlling the
pre-acidification temperature to 25.degree. C.; and controlling the
pH value to 5.5-6.9.
14. The method of claim 6, further comprising: after
pre-acidification, adding the mixed wastewater to an anaerobic
reaction tank for further anaerobic treatment to keep the tank at a
target pH, allowing reactions to proceed without limitation.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of Chinese Patent
Application No. 201910705494.6, filed on Aug. 1, 2019. The subject
matter thereof is hereby incorporated herein by reference in its
entirety.
FIELD
[0002] Some embodiments of the present invention generally pertain
to light industry technology pulping and papermaking wastewater
treatment, and more particularly, relate to a method that uses whey
blended pre-acidification treatment high calcium papermaking
industrial wastewater to promote anaerobic reaction and inhibit
calcification.
BACKGROUND
[0003] In 2018, the global pulp production was 417.4 million tons
and the waste pulp was 173.29 million tons. This accounted for
41.29% of total pulp, which is the most important raw material for
papermaking. The waste pulp saves a lot of wood resources and
significantly reduces environmental pollution. A large number of
calcium carbonate (CaCO.sub.3) fillers were added to reduce the
cost, improve the opacity and smoothness of paper in the process of
paper making, there are a lot of calcium ions in wastewater. In the
process of anaerobic treatment, calcium salt is deposited on the
surface, interior or pipeline of anaerobic granular sludge in the
form of calcium carbonate. A large amount of calcium salt
accumulation leads to a significant reduction in the activity of
bacteria in sludge, which seriously affects the treatment capacity.
With the increase of calcium ions, anaerobic granular sludge
produces calcification, even lead to complete calcification. Due to
the collapse of the entire anaerobic treatment system, enterprises
need to change the granular sludge frequently, causing serious
environmental pressure and economic loss. Enterprises also need to
change granular sludge frequently, causing serious environmental
pressure and economic loss when the anaerobic treatment system
breaks down. Therefore, the inhibition of calcification improves
the activity of anaerobic granular sludge and the stability of
anaerobic reaction system. At the same time, the composition of
high-calcium papermaking wastewater is complex, difficult to
degrade, and the nutrient composition, such as nitrogen, phosphorus
and potassium, is not balanced, sometimes some nutrients need to be
added.
[0004] The whey wastewater is a by-product of milk factory. After
the recovery of available protein, the chemical oxygen demand (COD)
concentration of the residual wastewater is still 10000-30000 mg/L.
There are a lot of protein, lactose, vitamins, and minerals in the
wastewater, so it is very difficult to treat the wastewater alone,
but it has high biological value. At same time, whey contains a
large amount of organic and inorganic phosphorus, the average
phosphorus content is 0.09%-0.2%, giving high calcium papermaking
wastewater to provide balanced nutrients.
[0005] The most common method is preprocessing first, remove toxic
and harmful substances initially, and anaerobic treatment. The
purpose is to greatly reduce the organic load, improving the
biodegradability of wastewater and creating favorable conditions
for subsequent aerobic treatment. Therefore, the effect of
anaerobic treatment has become the key point of the whole treatment
system. Chemical method and sewage sludge method are used to treat
the calcification of granular sludge in anaerobic reactor. Chemical
method inhibits the calcification of granular sludge by adding
chemical reagent, but the pH value in raw water is not be
increased. The precipitate not only reduces the calcium in
anaerobic reactor, but also ensure the stability of granular sludge
structure. Calcified sludge was separated and decomposed by sewage
sludge method, but the effect was not well.
SUMMARY
[0006] Certain embodiments of the present invention may provide
solutions to the problems and needs in the art that have not yet
been fully identified, appreciated, or solved by current light
industry pulping and paper making technologies. For example, some
embodiments of the present invention pertain to a method of adding
waste whey to high calcium papermaking wastewater to promote
anaerobic reaction and inhibit calcification of anaerobic granular
sludge.
[0007] In some embodiments, the method uses whey pre-acid treatment
of wastewater with high calcium concentration to promote anaerobic
digestion and delay calcification. The method includes pre-acid
treatment of papermaking wastewater with whey wastewater before
anaerobic treatment.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] In order that the advantages of certain embodiments of the
invention will be readily understood, a more particular description
of the invention briefly described above will be rendered by
reference to specific embodiments that are illustrated in the
appended drawings. While it should be understood that these
drawings depict only typical embodiments of the invention and are
not therefore to be considered to be limiting of its scope, the
invention will be described and explained with additional
specificity and detail through the use of the accompanying
drawings, in which:
[0009] FIG. 1 is a flow diagram illustrating a method for promoting
anaerobic digestion and delay calcification, according to an
embodiment of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0010] In view of the shortcomings of the existing technology, some
embodiments provide a method that uses whey blended
pre-acidification treatment high calcium papermaking industrial
wastewater to promote anaerobic reaction and inhibit calcification.
The method may improve the pretreatment process of the methanation
step. For example, acidification pretreatment is used to produce
stable anaerobic reaction performance of high concentration
wastewater under high organic load. Acidification pretreatment
ensures the dynamic balance between acidification, achieving low
and stable pH value (5.5-6.5), promoting the anaerobic reaction of
papermaking industrial wastewater, and improving the efficiency of
anaerobic methane production of wastewater. At the same time,
acidification pretreatment inhibits the calcium deposition
phenomenon when the pH is high.
[0011] In some embodiments, the method uses whey pre-acid treatment
of wastewater with high calcium concentration to promote anaerobic
digestion and delay calcification. The method includes pre-acid
treatment of papermaking wastewater with whey before anaerobic
treatment.
[0012] In some embodiments, the volume ratio of whey wastewater to
papermaking wastewater is 1:10-15. This may allow for the nutrition
of wastewater system to be more balanced, which is conducive to the
metabolism, growth and reproduction of acidizing bacteria and
subsequent methanogens.
[0013] Also, in some embodiments, the pre-acidification temperature
is 25.degree. C., and the pH value is 5.5-6.9. This may prevent
propionic acid of product of acidolysis from inhibiting the
subsequent methane production process.
[0014] In some further embodiments, the pre-acidification treatment
is carried out in the pre-acidification tank, and the hydraulic
retention time is controlled at 3-4 hours (h). Its function is to
adjust the pre-acidification degree of papermaking wastewater,
which is more conducive to the subsequent methane production and
provides stable pH value.
[0015] In some additional embodiments, the pre-acidification tank
is equipped with a stirring device, having a stirring speed of
170-200 revolutions per minute (RPM). The whey wastewater and
papermaking wastewater are mixed evenly, and anaerobic granular
sludge is in full contact with wastewater.
[0016] The beneficial effects of the embodiments are discussed in
more detail below.
[0017] Some embodiments use the whey wastewater to mix with the
wastewater of papermaking plant. The papermaking wastewater is
pretreated by acidification, making the wastewater entering the
anaerobic reaction system stable and easy to be treated. The
acidification pretreatment has a low and stable pH value, which
promotes anaerobic reaction of papermaking wastewater and inhibits
calcium precipitation. For purposes of explanation, a low and
stable pH value is the growth environment suitable for anaerobic
bacteria in anaerobic granular sludge, i.e., the pH is 5.5-6.9 and
lower than that of the original papermaking wastewater. At the same
time, the whey wastewater provides necessary nutrients for
anaerobic bacteria in the treatment of papermaking wastewater with
relatively single component, and increases the activity of
anaerobic reaction system. In this way, whey wastewater can be
turned into treasure. For purposes of explanation, nutrients may be
defined as organic materials and carbon, and treasure may be
defined as whey wastewater being more fully utilized.
[0018] Pre-acidification treatment may improve the pretreatment
process of methanation. For example, pre-acidification treatment
produces stable anaerobic reaction performance of high
concentration wastewater under high organic load. In addition,
carbohydrates lead to the fermentation of lactic acid, ethanol,
acetic acid and butyric acid at a low pH, which is easy to produce
propionic acid. This is the speed limiting step of the whole
methanation process. After pre-acidification, fermentation to
propionic acid can be avoided, which can prevent propionic acid
from inhibiting the subsequent methanogenesis process and
microorganisms in the anaerobic reaction system.
[0019] After pre-acidification treatment, some of the calcium ions
in the wastewater is precipitated, and is easy to be treated due to
it not being in the anaerobic reactor. For example, due to high
concentrations of calcium ion, only part of the reaction
precipitates. The method described herein removes calcium ions to
some extent. Entering the anaerobic treatment system, the calcium
ion content is reduced due to pre-acidification treatment.
Therefore, the calcification of granular sludge can be delayed, and
the anaerobic reaction system can operate normally and improve
benefit.
IMPLEMENTATION EMBODIMENT 1
[0020] In some embodiments, the method uses whey pre-acid treatment
of wastewater with high calcium concentration to promote anaerobic
digestion and delay calcification. In this embodiment, the
experiment is carried out under laboratory conditions, the total
chemical oxygen demand (TCOD) concentration of raw water is
8000.+-.536 mg/L, and the calcium ion concentration is 300.+-.50
mg/L. The specific operation is as follows.
[0021] The pre-acidification tank is used to add papermaking
industrial wastewater and waste whey. The waste whey is added from
the lower end of the acidification tank through pipes. To balance
the nutrition of wastewater system, the volume ratio of waste whey
and papermaking industrial wastewater is 1:10, and the volume of
pre acidification tank is 800 m3.
[0022] Further, in order to mix the papermaking wastewater and whey
evenly, a mixing device is set in the pre-acidification tank, and
the speed of the rotor is adjusted to 170 RPM.
[0023] The water temperature in the container is kept at 25.degree.
C., and pH was maintained at 5.5 after whey wastewater was added.
In order to prevent propionic acid of product of acidolysis from
significantly having inhibition effect on the subsequent methane
production process at low pH. Put simply, to prevent propionic
acid, acidolysis products of anaerobic granular sludge,
significantly having inhibition effect on the subsequent methane
production process at low pH is at or about 4.5. Further, when pH
is low (i.e., lower than 4.5), the activity of anaerobic bacteria
is weakened or even inhibited.
[0024] The hydraulic retention time in the pre-acidification tank
is controlled at 3 h, which is used to regulate the
pre-acidification degree of papermaking industrial wastewater. It
is more conducive to the subsequent methane production.
[0025] After pre-acidification, the wastewater is added to the
anaerobic reaction bottle for further anaerobic treatment. The TCOD
removal rate was 70% after anaerobic reaction, and the TCOD was
increased by 10% after pre-acidification. The COD of effluent
(SCOD) was 500.+-.34 mg/L, and the removal rate was 94.+-.1%. The
methane production was 0.38.+-.0.03 m.sup.3/m.sup.3d, the
efficiency was increased by 30%. The calcium precipitation was 30%,
and the retention rate was less than 10%, which was significantly
lower than the original 25%. There was no obvious calcification
within two years of operation, and the severe fluctuation of
anaerobic system and the times of heavy sludge discharge were
significantly reduced. The proportion of microorganism in granular
sludge was VSS/TSS.gtoreq.0.69. The degree of calcification was
reduced, the stability of anaerobic reaction process was ensured,
the methane production rate was significantly increased, the
calcification of granular sludge was obviously delayed, and the
enterprise benefit was improved.
IMPLEMENTATION EMBODIMENT 2
[0026] In some embodiments, the method uses whey pre-acid treatment
of wastewater with high calcium concentration to promote anaerobic
digestion and delay calcification. The embodiment is carried out
under paper mill conditions. The TCOD concentration of raw water is
8000.+-.750 mg/L, and the calcium ion concentration is 350.+-.43
mg/L. The operation is described in more detail below.
[0027] The wastewater from papermaking industry is added to the
pre-acidification tank, and then a certain amount of whey
wastewater is added. Because this paper mill has a certain distance
from dairy processing and road conditions, which is not convenient
for pipeline transportation, the whey wastewater is transported to
the paper mill by tank truck and added from the lower end of
pre-acidification pool. To balance the nutrition of wastewater
system, the volume ratio of whey wastewater and papermaking
wastewater is kept at 1:12, and the volume of pre-acidification
tank is 1200 m.sup.3.
[0028] In order to make the whey wastewater and papermaking
wastewater mix evenly, a mixing device is set in the pre
acidification tank, and the speed of the rotor is adjusted to 185
rpm.
[0029] The water temperature in the container is kept at 25.degree.
C., and pH was maintained at 6.2 after whey wastewater was
added.
[0030] The hydraulic retention time in the pre-acidification tank
is controlled at 4 h, which is used to regulate the
pre-acidification degree of papermaking industrial wastewater. It
is more conducive to the subsequent methane production and enhance
the balance of anaerobic reaction system.
[0031] After pre-acidification treatment, the wastewater is added
to the anaerobic reaction bottle for further anaerobic treatment.
The TCOD removal rate was 75% after anaerobic reaction, and the
TCOD was increased by 15% after pre-acidification. The SCOD was
335.+-.30 mg/L, and the removal rate was 96.+-.1%. The methane
production was 0.45.+-.0.04 m.sup.3/m.sup.3d, the efficiency was
increased by 50%. The calcium precipitation was 32%, and the
retention rate was less than 8%, which was significantly lower than
the original 20%. There was no obvious calcification within three
years of operation, and the severe fluctuation of anaerobic system
and the times of heavy sludge discharge were significantly reduced.
The proportion of microorganism in granular sludge was
VSS/TSS.gtoreq.0.74. The degree of calcification was reduced, the
stability of anaerobic reaction process was ensured, the methane
production rate was significantly increased, the calcification of
granular sludge was obviously delayed, and the enterprise benefit
was improved.
IMPLEMENTATION EMBODIMENT 3
[0032] In some embodiments, the method uses whey pre-acid treatment
of wastewater with high calcium concentration to promote anaerobic
digestion and delay calcification. The TCOD of the mixed solution
of the pre-acidification tank is 8000.+-.850 mg/L, and the calcium
ion concentration is 400 mg/L. The papermaking wastewater is from
the factory. The operation is described in more detail below.
[0033] The wastewater is added to the pre-acidification tank, and
the whey wastewater of 4.degree. C. cold storage is taken out and
added to the pre-acidification tank. The volume ratio of whey
wastewater to papermaking wastewater is 1:15.
[0034] In order to make it mix evenly, a mixing device is set in
the pre-acidification tank, and the speed of the rotor is adjusted
to 200 rpm.
[0035] The water temperature in the container is kept at 25.degree.
C., and pH is maintained at 6.9 after whey wastewater was
added.
[0036] The hydraulic retention time in the pre-acidification tank
is controlled at 4 h, which is used to regulate the
pre-acidification degree of papermaking industrial wastewater.
[0037] After pre-acidification treatment, the wastewater is added
to the anaerobic reaction bottle for further anaerobic treatment.
The TCOD removal rate was 83.+-.3% after anaerobic reaction, and
the TCOD was increased by 20% after pre-acidification. SCOD was
260.+-.40 mg/L, and the removal rate was 97.+-.1%. The methane
production was 0.48.+-.0.04 m.sup.3/m.sup.3d, the efficiency was
increased by 60%, and the calcium precipitation was 35%. There was
no obvious calcification within three months of operation, which
ensures the stability of anaerobic reaction process. It can
significantly improve the methane yield and delay the calcification
of granular sludge.
[0038] In the anaerobic reaction without pre-acidification
treatment, the removal rate of COD was about 60%. The methane
production capacity and calcium precipitation effect were not
obvious, and there was also instability of wastewater treatment
system. After pre-acidification, the anaerobic reaction had been
improved, and the performance parameters had been greatly improved.
The most important anaerobic reaction process was stable. The
content of calcium ions in the system is reduced, which is easy to
eliminate and inhibit the calcification of granular sludge, so as
to improve enterprise benefits.
[0039] According to the results of embodiments 1 to 3, the method
of the invention promotes the anaerobic reaction through the
pre-acidification treatment, and the anaerobic process is carried
out stably. With the deepening of pre-acidification treatment, the
pollutant treatment effect and calcium precipitation will be
improved. When the processing time is 4 hours, the best results are
as follows.
[0040] The TCOD removal rate was 83.+-.3%, the effluent COD was
260.+-.40 mg/L, the removal rate was 97.+-.1%. The methane
production was increased to 0.48.+-.0.04 mg/m.sup.3d and efficiency
increased by 60%. Calcium precipitation increased to 35%. The
results show that the anaerobic process become far more stable.
[0041] FIG. 1 is a flow diagram illustrating a method 100 for
promoting anaerobic digestion and delay calcification, according to
an embodiment of the present invention. Method 100 may begin at 105
with mixing whey wastewater with wastewater from a papermaking
plant, and at 110, pre-treating the papermaking plant wastewater by
acidification to stabilize the papermaking plant wastewater prior
to entering an anaerobic reaction system.
[0042] The features, structures, or characteristics of the
invention described throughout this specification may be combined
in any suitable manner in one or more embodiments. For example,
reference throughout this specification to "certain embodiments,"
"some embodiments," or similar language means that a particular
feature, structure, or characteristic described in connection with
the embodiment is included in at least one embodiment of the
present invention. Thus, appearances of the phrases "in certain
embodiments," "in some embodiment," "in other embodiments," or
similar language throughout this specification do not necessarily
all refer to the same group of embodiments and the described
features, structures, or characteristics may be combined in any
suitable manner in one or more embodiments.
[0043] It should be noted that reference throughout this
specification to features, advantages, or similar language does not
imply that all of the features and advantages that may be realized
with the present invention should be or are in any single
embodiment of the invention. Rather, language referring to the
features and advantages is understood to mean that a specific
feature, advantage, or characteristic described in connection with
an embodiment is included in at least one embodiment of the present
invention. Thus, discussion of the features and advantages, and
similar language, throughout this specification may, but do not
necessarily, refer to the same embodiment.
[0044] Furthermore, the described features, advantages, and
characteristics of the invention may be combined in any suitable
manner in one or more embodiments. One skilled in the relevant art
will recognize that the invention can be practiced without one or
more of the specific features or advantages of a particular
embodiment. In other instances, additional features and advantages
may be recognized in certain embodiments that may not be present in
all embodiments of the invention.
[0045] One having ordinary skill in the art will readily understand
that the invention as discussed above may be practiced with steps
in a different order, and/or with hardware elements in
configurations which are different than those which are disclosed.
Therefore, although the invention has been described based upon
these preferred embodiments, it would be apparent to those of skill
in the art that certain modifications, variations, and alternative
constructions would be apparent, while remaining within the spirit
and scope of the invention. In order to determine the metes and
bounds of the invention, therefore, reference should be made to the
appended claims.
* * * * *