FORM -2
THE PATENTS ACT, 1970
(39 OF 1970)
&
The Patents Rules, 2003
PROVISIONAL/COMPLETE
SPECIFICATION
(See section 10 and rule 13)
1. Title of the Invention: METHOD FOR REMOVING ORGANIC MATERIAL
IN OILFIELD PRODUCED WATER AND A
REMOVAL DEVICE THEREFOR
2. Applicant(s)
Name, Nationality & Address:
HITACHI, LTD.,
a corporation organized under the laws of Japan,
of 6-6, Marunouchi 1-chome, Chiyoda-ku,
Tokyo 100-8280, JAPAN
3. Preamble to the description:
PROVISIONAL: The following specification describes the Invention.
COMPLETE: The following specification particularly describes the
invention and the manner in which is to be performed.

1
Specification
METHOD FOR REMOVING ORGANIC MATERIAL IN OILFIELD PRODUCED WATER
AND A REMOVAL DEVICE THEREFOR
5 Technical Field
[0001]
The present invention relates to a treatment process and
a treatment device for oilfield produced water which is separated
and produced from a mixture of crude oil and salt water in an
10 oil field and, specifically, relates to a method and a device
for effectively removing an organic material, such as oil
droplets etc., included in oilfield produced water and dissolved
organic compounds.
15 Background Art
[0002]
A mixture in a state where crude oil is mixed with salt
water is mined in an oilfield area, and oilfield produced water
is formed by separating crude oil and salt water from this mixture.
20 Since the oilfield produced water contains a considerable amount
of oil droplets and dissolved organic compounds, there is a
fear that returning it to the sea, the lakes and marshes will
bring about the destruction of the environment.
[0003]
25 Conventionally, various methods have been discussed to

2
separate and remove the oil contained in oilfield produced water
which is produced in an oilfield area. For instance, in JP-A
No. 2003-144805, it is disclosed that the oil contained in
oilfield produced water is made into an emulsion, and a magnetic
5 floc is form by adding magnetic powder and a coagulant therein,
and the magnetic floe is separated by magnetic aspiration.
[0004]
Moreover, "Experience of Produced Water Treatment in the
North Sea, Marine Pollution Bulletin, Vol. 29, No. 6-12, (1994),
10 p.312-316" describes that oil droplets are separated by using
a liquid cyclone.
[0005]
However, even when oil droplets in the oilfield produced
water are removed, a considerable amount of organic compounds,
15 for instance, acetic acid, propionic acid, and valeric acid,
etc. are dissolved in the oilfield produced water and they become
a reason for the bad small and the damage to the environment,
so that a removal technique has been discussed. The index to
measure the content of the aforementioned dissolved organic
20 compound is a value called the COD (chemical oxygen demand).
Therefore, the dissolved organic compound associated with the
aforementioned oilfield goes by the name of COD element.
[0006]
In JP-A No. 2004-275884, it is described that activated
25 carbon powder is added to the oilfield produced water to absorb

3
the COD elements and the activated carbon powder congregates
and is separated by adding a coagulant.
[0007]
In JP-A No. 2004-255290, it is described that an organic
5 polymer coagulant is added to the oilfield produced water and,
moreover, the oil content is decomposed by adding a polymer
coagulant and an oxidant. It is also described that excess
oxidant is absorbed and removed by using activated carbon, and
that hypochlorous acid, etc. formed by electrodialysis is used
10 for an oxidant.
[0008]
The technologies described in the various aforementioned
well-known documents have a problem from the viewpoint of
suitable treatment of the oil content in the oilfield produced
15 water and the dissolved organic compounds which will be a problem
hereafter and treatment of the separated organic compound. For
instance, a large amount of sediment becomes a serious problem
in a method for precipitating the activated carbon, on which
an organic material is adsorbed, by using a coagulant. Though
20 the oil content may be decomposed to a certain point by using
an oxidant such as hypochlorous acid, etc., it is not clear
that the dissolved organic compound can be effectively
decreased.
[0009]
25 In JP-A No. 2000-93957, a technology is disclosed in which

4
water including a small amount of organic material, such as
drinking water, etc. is purified by using a water purification
film which contains a zeolite. However, it is not a technology
which processes very poor water which contains a large amount
5 of oil and organic compounds such as the oilfield produced water.
[0010]
[Patent Document 1] JP-A No. 2003-144805
[Patent Document 2] JP-A No. 2004-275884
[Patent Document 3] JP-A No. 2004-255290
10 [Patent Document 4] JP- No. 2000-093957
[Non-patent Documents 1] Experience of Produced Water
Treatment in the North Sea, Marine Pollution Bulletin, Vol.29,
No.6-12, (1994), p.312-316
15 Disclosure of the Invention
Problems to be Solved by the Invention
[0011]
Therefore, a method and a device for treating oilfield
produced water in which the oil content and the dissolved organic
20 compounds contained in the oilfield produced water are
effectively separated and removed, and in which the load on
the facility, the cost, and the burden on the environment, etc,
are lower in subsequent treatments.
Means for Solving the Problems
25 [0012]

5
The present invention provides a method and a device for
effectively removing the oil content and the dissolved organic
compounds by performing an oil separation treatment of oilfield
produced water which is obtained by separating crude oil from
5 a mixture of crude oil and salt water mined from an oilfield,
and by bringing the aforementioned oilfield produced water into
contact with an absorbent which absorbs and removes the dissolved
organic compounds in oilfield produced water to which an oil
removal treatment is performed.
10
BRIEF DESCRIPTION OF THE DRAWINGS
[0013]
Fig. 1 is a diagram illustrating an outline configuration
of a treatment system of oilfield produced water by the first
15 embodiment of the present invention.
Fig. 2 is a diagram illustrating an outline configuration
of a treatment system of oilfield produced water by another
embodiment of the present invention.
Figs. 3 are a sectional schematic drawing illustrating
20 an adsorption tower with an outer heating furnace used in the
present invention.
Fig. 4 shows X-ray diffraction patterns of an absorbent
used in the present invention.
Fig. 5 is a sketch drawing illustrating a configuration
25 example of an adsorption tower in a treatment system of an

6
embodiment in the present invention.
Fig. 6 is a graph illustrating a relationship between
the heating temperature of the adsorbent and the concentration
of the carrier gas element during temperature-programmed
5 desorption of the adsorbent used in the present invention.
Fig. 7 is a graph illustrating a relationship between
the regeneration temperature of the absorbent used in the present
invention on which a catalytic element is supported and the
carbon concentration remaining in the adsorbent after
10 regeneration.
Fig. 8 is a graph illustrating a relationship between
the regeneration temperature of the adsorbent used in the present
invention and the CODMN value before and after adsorption.
Fig. 9 is a graph illustrating a relationship between
15 the concentration of a catalytic element Co and the residual
carbon concentration after using an adsorbent on which Co is
supported and after thermal regeneration at 400°C for one hour.
Fig. 10 is a graph illustrating a relationship between
the concentration of a catalytic element Mn and the residual
20 carbon concentration after using an adsorbent on which Mn is
supported and after thermal regeneration at 400°C for one hour.
Fig. 11 is a graph illustrating a relationship between
the operating time of the adsorbent and the rate of COD decrease
of the treated water after the treatment.
25 Fig. 12 is a schematic drawing illustrating a structure

7
of an aeration tank arranged instead of an electric potential
generation device and electrolytic bath.
Description of Reference Numerals
5 [0014]
1: oilfield produced water, 2: Raw water tank, 3: coagulation
tank , 4: rotary filter device, 5: rotary filter film, 6: rotary
cylinder, 7: floe, 8: scraping plate, 10: drainage treatment
device, 11: magnetic separation device, 13: potential
10 generation device, 14: electrolytic bath, 15: exhaust pipe,
16: exhaust combustion tower, 17, 19: adsorption tank, 18:
drainage supply tube, 20: heating furnace, 21: adsorbent, 22:
hot-air blower, 23: drain tube, 24: drain valve, 25: second
treated water, 26: COD monitor, 27: reservoir, 28: ventilation
15 tube, 29: moisture meter, 30: duct, 31: gas analyzer, 91, 92:
electrode, 180: second treated water.
Best Mode for Carrying out the Invention
[0015]
20 The present invention is one where oil droplets, etc.
in oilfield produced water are removed and dissolved organic
compounds associated with the water are adsorbed and removed,
and a magnetic separation method is especially suitable as a
method for removing the oil droplets, etc. Moreover, although
25 adsorption and removal using an adsorbent are necessary as

8
methods for removing a dissolved organic compound, electrolysis,
etc. may be used as a treatment before the adsorption treatment •
Hereinafter, some items for the methods of adsorption and removal
which are important in the present invention will be described
5 in detail.
[I] Example of the dissolved organic compound contents;
Table 1 shows the contents of the salts and dissolved organic
compounds which are contained in produced water in a typical
crude oil produced in Japan. Moreover, Table 2 shows the
10 components and concentrations of produced water in a typical
crude oil produced in a foreign country. The kind and contents
change in every sort of way depending on the oilfield. Normal
and/or iso-butyric acid and normal and/or iso-valeric acid are
the agents responsible for the bad smell.
15 [0016]
[Table 1]
Component Molecular formula Concentration(mg/L)Analytical value
Sodium chloride NaCl 16000
Acetic acid CH3COOH 1970
Propionic acid CH3CH2COOH 400
n-butyric acid CH3(CH2)2COOH 78
iso-butyric acid (CH3)2CHCOOH 430
n- valeric acid CH3(CH2)3COOH 15
iso-valeric acid (CH3) 2CHCH2COOH 78
Acetone CH3COCH3 2
Phenol C6H5OH 12
Cresol C6H4(CH3)OH 8
Methyl ethyl ketone (CH3)2CH2CO 0.3
Benzene C6H6 0.28
Toluene CgH5CH3 0.06

9
[0017]
[Table 2]
Component Molecular formula Concentration(mg/L)Analytical value
Sodium chloride NaCl 21000
Acetic acid CH3COOH 12000
Propionic acid CH3CH2COOH 2420
n-butyric acid CH3(CH2)2COOH 110
iso-butyric acid (CH3)2CHCOOH 460
n- valeric acid CH3(CH2)3COOH 110
iso-valeric acid (CH3)2CHCH2COOH 1840
Acetone CH3COCH3 5
Phenol C6H5OH 14
Cresol C6H4(CH3)OH 12
Methyl ethyl ketone (CH3)2CH2CO 0.8
Benzene CeH6 1.5
Toluene C6HsCH3 0.8
[II] Comparison of COD treatment methods
5 When the effectiveness was confirmed through experiments
on various COD removal treatment methods, the following results
were obtained. That is, it is understood that there is a problem
regarding practical use except for a method using an
easy-regeneration-type inorganic adsorbent such as a zeolite
10 absorbent which is used in the present invention.
(1) Activated sludge process; organisms are damaged by the
effects of chlorine. The treatment time is long.
(2) Addition of sodiumhypochlorite; there is little COD decrease
effect.
15 (3) Hypochlorite generation (electrolysis); there is little
COD decrease effect.
(4) Fenton oxidation; there is little COD decrease effect.

10
(5) Vacuum concentration (distillation); Only the material
having a boiling temperature substantially different from water
can be separated. The treatment of condensate is a problem.
(6) Activated carbon; Regeneration is difficult although COD
5 can be decreased. The cost is high because a large amount of
activated carbon is necessary.
[0018]
The characteristics of a preferable
easy-regeneration-type inorganic adsorbent used in the present
10 invention are as follows.
(a) Adsorption capacity is large.
(b) Adsorption and desorption rates are great.
(c) Regeneration is possible. (Consumption of the adsorbent
is small according to the regeneration.)
15 (d) Mechanical strength is sufficiently great.
(e) Pore size of the adsorbent is appropriate.
(f) Surface property of the adsorbent is suitable for an
adsorption material of the object.
[0019]
20 In an embodiment of a specifically preferable COD removal
process in the present invention, removal is possible by
combining an oil-water separation method, an electrolysis
method, and an adsorptive removal method using the adsorption
characteristics of the COD element of synthetic zeolite.
25 Moreover, the adsorptivity can be easily recovered to be almost

11
the same as before use by thermal regeneration even after a
water-soluble organic compound element is sufficiently
adsorbed and the adsorptivity becomes lower, so that the
operation is not complicated and the cost for drainage treatment
5 can be reduced.
[0020]
In the present invention, it is desirable that a
proton-type zeolite be used for an adsorbent. Specifically,
it is desirable that synthetic zeolite be used in which the
10 silica/alumina ratio is high being five or more by the molar
ratio. The synthetic zeolite where the silica/alumina ratio
is high has excellent hydrophobic properties, and it is suitable
for selectively adsorbing organic elements inside drainage.
[0021]
15 The operation of the COD removal device is managed and
used by considering the amount of water to be treated, the amount
of adsorbent, and the adsorption treatment time per unit
adsorption tower, etc. to make the COD value of the treated
water lower than 120 mg/L which is a standard of the drainage
20 regulation. In a COD removal method and a device thereof in
the embodiment of the present invention, the aforementioned
variety of data is stored in the storage part of the controller,
and the method and the device are controlled according to the
data, if necessary.
25 [0022]

12
A treatment device of produced water in an embodiment
of the present invention does not need large-scale equipment
etc. and the device itself can be made compact in spite of it
being able to process an element to a high degree, such as organic
5 solvents, etc. contained in the oilfield produced water
regardless of the concentration, so that the oilfield produced
water can be treated at low cost.
[0023]
As already mentioned, various organic elements are
10 dissolved in oilfield produced water and they become agents
responsible for the increase in COD. A problem to be solved
in the present invention is that the COD of such oil separated
water is decreased to be lower than the standard of the drainage.
Moreover, it is to provide a COD removal system where the
15 adsorption activity and the durability are maintained for a
long time.
[0024]
It can be achieved by using a carbonaceous adsorbent
(activated carbon) and an inorganic adsorbent as an adsorbent
20 where an organic solvent is removed from oilfield produced water
by adsorption. However, there is a problem that activated
carbon is not easy to be regenerated although it has excellent
adsorptivity, and it is important to make use of a method which
can solve the problem.
25 [0025]

13
The COD elements associated with water in typical crude
oil produced in Japan are acetone, methyl ethyl ketone, acetic
acid, propionic acid, butyric acid, valerianic acid,
trichloroethylene, tetrachloroethylene, benzene, toluene,
5 ethylbenzene, xylene, phenol, cresol, xylenol,
hexachlorobenzene, carbon disulfide, methanol, succinic acid,
and lactic acid, etc.
[0026]
Adsorptivity of the synthetic zeolite for the
10 aforementioned COD elements has uniqueness. The many kinds
of synthetic zeolites can be used together as a mixture or in
combination. Specifically, by combining adsorbents having
different cavity diameters (pore sizes), from an organic
compound having small molecular weight to an organic compound
15 having large molecular weight, they can be effectively adsorbed.
For instance, an organic compound having small molecular weight
such as acetic acid is adsorbed by an adsorbent having small
pore size and an organic compound having large molecular weight
such as valeric acid and an aromatic compound is adsorbed by
20 an adsorbent having large pore size. This is because there
is a possibility that a compound having a molecular weight which
can not be adsorbed by one kind of adsorbent remains in the
produced water. Thus, it is understood that the COD element
can be effectively removed in stages by adsorbing the element
25 for which each adsorbent is best, even when a plurality of

14
adsorption towers filled with adsorbent are arranged in parallel
or in series against the flow of water to be processed, or when
adsorbents having different pore sizes are mixed and packed
in one adsorption tower.
5 [0027]
As far as the shape of the adsorbent, consideration is
given to a variety, and there are molded bodies such as powder
shapes, particle shapes, pellet shapes, rod shapes, fiber shapes,
plate shapes, honeycombs, and tube-forms, etc. From the
10 viewpoint of economy and environmental protection, it is
extremely important that the adsorbent used is regenerated and
used repeatedly. Therefore, the adsorbent is used in a shape
and a way of use where it is easily regenerated. For instance,
even when it is in a shape such as a powder shape, particle
15 shape, and pellet shape, it is important that they are easily
separated from the water to be treated and a regeneration
treatment is applied. Therefore, these various shapes of
adsorbents are installed in the adsorption tower by sandwiching
them between meshes and porous plates so that they are not
20 discharged from the adsorption tower and are easily separated
from the water to be treated. In the case of other shapes,
an installation method is adopted which takes the regeneration
into consideration.
[0028]
25 According to the present invention, a device for treating

15
oilfield produced water is provided which comprises an oil-water
separation tank where the oil content and undissolved particles
floating and suspended in the drainage are removed, an
electrolytic bath where molecules of an organic element are
5 decomposed in the first treated water passing through the
oil-water separation tank, an adsorption removal tank where
an organic element is adsorbed and removed from the second
treated water passing through the electrolytic bath, and a
combustion chamber where the organic compound eliminated from
10 the adsorption removal agent which is filled in the adsorption
removal tank is burned and exhausted.
[0029]
According to the present invention, a device for treating
oilfield produced water is provided which comprises an oil-water
15 separation tank where the oil content and undissolved particles
floating and suspended in the drainage are removed, an
electrolytic bath where molecules of an organic element are
decomposed in the first treated water passing through the
oil-water separation tank, a separation removal tank where an
20 organic element is separated and removed from the second treated
water passing through the electrolytic bath, an adsorption
removal tank where an organic element is adsorbed and removed
from the third treated water passing through the electrolytic
bath, and a combustion chamber where the organic element
25 separated and removed in the separation removal tank and the

16
organic element separated and removed in the adsorption removal
tank are mixed, burned, and exhausted. The aforementioned
oil-water separation tank is preferably a magnetic separation
tank.
5 [0030]
Moreover, an inorganic adsorption removal agent is
preferable as an adsorption removal agent used for the
aforementioned adsorption removal tank. A natural zeolite or
a synthetic zeolite is preferable for the aforementioned
10 inorganic adsorbent, where the crystal structure including
silica and aluminum oxide is zeolite and the ratio of silica
and aluminum is 5ormoreasaSi02/Al203moleratio. Specifically,
a synthetic zeolite having excellent hydrophobic property is
preferable. Moreover, one is preferable for the aforementioned
15 inorganic adsorbent, in which at least one element from silica,
aluminum oxide, and sodium oxide is included, the ratio of silica
and aluminum oxide is 5 or more in the mole ratio of SiO2/Al2O3,
and the adsorbent includes at least one element selected from
the group of Pt, Pd, Ru, Rh, Ni, Fe, Cu, Mn, and Co.
20 [0031]
Furthermore, it is preferable that an inorganic
adsorption removal agent be used which, after adsorbing and
removing the organic elements, be repeatedly regenerated by
heating at 100°C to 600°C under atmospheric atmosphere.
25 [0032]

17
The aforementioned separation removal tank may be a
separation removal tank where a volatile organic compound can
be separated and removed by aerating the first treated water.
[0033]
5 Moreover, the present invention provides a treatment
method comprising a magnetic separation process where the oil
content and undissolved particles floating and suspended in
the drainage is removed, an electrolysis process where the
magnetically separated oilfield produced water is electro lyzed,
10 a separation removal process where volatile organic compounds
are separated and removed from the second treated water from
the aforementioned electrolysis process, an adsorption removal
process where an organic element is adsorbed and removed from
the third treated water discharged from the separation removal
15 tank, a process where volatile organic compounds discharged
along with steam from the separation removal tank and is burned
and exhausted.
[0034]
In addition to using, in combination, a magnetic separation
20 device, an aeration tank, an evaporation concentration device,
a hypochlorous acid reaction device and/or an electrolytic device
in accordance with the COD value of the oilfield produced water
which is the raw material, a method for removing the COD element
by using an adsorption technique is preferable in which a
25 catalytic adsorbent is used until the COD value finally becomes

18
lower than the environmental standard value of a drainage and,
therefore, zeolite is suitable for the catalytic adsorbent.
Among these, synthetic zeolite is effective, having specif ically
a high silica/alumina ratio and hydrophobic properties.
5 [0035]
Although the catalytic adsorption treatment method is
relatively easy to systemize, the life and regeneration
frequency of the catalyst have a strong relationship with the
process cost. Therefore, in addition to its properties being
10 important, it is also important that regeneration of the
adsorbent be easy as well.
[0036]
In order to regenerate the adsorbent on which organic
materials such as organic solvents, etc. are absorbed, there
15 is an effective method for removing them by using a heating
method, a so called dry heating method, where the adsorbed carbon
element is oxidized and burned. However, there is a limit to
how often the regeneration can be repeated because the carbon
system adsorbent itself burns and is consumed, so that there
20 is a disadvantage that an efficient COD removal system cannot
be built because a device for replenishing the spent material
is necessary. Moreover, in the case of an ocean oilfield, it
is preferable that the supply of adsorbent for recharging be
avoided as much as possible from the viewpoint of transportation
25 costs.

19
[0037]
According to the present invention, a COD element in
oilfield produced water can be removed by an adsorption technique
using a zeolite as an adsorbent, and the most important
5 characteristic is that the deterioration of the adsorption
properties by the material to be adsorbed can be recovered by
combustion and decomposition in atmosphere.
[0038]
As mentioned above, among the zeolites, synthetic zeolite
10 is specifically suitable for a material which uses the feature
of the present invention, and synthetic zeolite is the most
suitable among those where the SiO2/Al2O3 ratio is 5 or more
in the mole ratio, and it has hydrophobic properties.
Specifically, ZSM-5 is an absorbent which is suitable for the
15 purpose of the invention.
[0039]
When the carbon element caused by the adsorbed organic
material remains as is on the surface of the adsorbent, the
surface activity of the adsorbent is decreased. Therefore,
20 when the activity of the adsorbent is decreased, the activity
has to be recovered by removing the carbon element.
[0040]
The organic material adsorbed on the adsorbent remains
as a carbon element. The carbon element can not generally be
25 removed unless it is heated at 600°C or more. However, sodium

20
chloride in the same concentration as seawater is dissolved
in the actual oilfield produced water. Therefore, when there
is repeated regeneration at 600°C, SiO2 which is a main component
of the zeolite reacts with Na in sodium chloride for a short
5 time, resulting in the deterioration in its function as an
adsorbent. Heating at a temperature that is as low as possible
below 600°C is desirable.
[0041]
By supporting a catalytic element the organic material
10 on the surface of the adsorbent can be decomposed, oxidized,
and burned at a temperature of 500°C or less, and under the
best conditions at a low temperature of 400°C or less, and the
adsorbent can be recovered to an original active state.
[0042]
15 According to the present invention, it is possible to
reduce the concentration of organic elements in oilfield
produced water at a low cost of operation as well as to control
the consumption of the adsorbent compared with the prior art.
[0043]
20 Moreover, the present invention has an advantage superior
to a conventional method in the following points. Specifically,
synthetic zeolite is used for a main component of the adsorbent
and the organic materials adsorbed on the surface of the
adsorbent is oxidized and burned by using a catalytic effect
25 of the catalytic element supported on the surface of the

21
synthetic zeolite, resulting in the adsorptivity being
recovered at the same level as that before use.
[0044]
The catalytic element is selected from the group of noble
5 metals such as Pt, Pd, Rh, Au, and Ag, etc. and transition metals
such as Fe, Ni, Mn, and Co, etc. have a similar effect.
[0045]
Since the regeneration operation can be done only by
removing the treated water while the absorbent is filled, there
10 are no complications operationally, and there is also an
advantage from the viewpoint of reducing the drainage treatment
cost.
[0046]
Synthetic zeolite is made to come into contact with
15 oilfield produced water for the purpose of removing the COD
element from the oilfield produced water. As a result, it could
be decreased to a COD concentration, which is less than the
target emission regulation demonstrated or less by the
adsorptivity. The activity of one where the adsorptivity is
20 deteriorated by extended duration use can be recovered by burning
and removing the carbon element originating from the organic
materials by heating the adsorbent. Therefore, it is effective
to repeatedly remove the COD elements in oilfield produced water
for a long time.
25 [0047]

22
Specifically, an adsorbent where a catalytic element is
supported on the surface of a synthetic zeolite maintains its
adsorptivity, and it is possible to oxidize and decompose the
adsorbed organic elements and to oxidize and burn the carbon
5 elements only by heating at a relatively low temperature of
500°C or less.
EMBODIMENT
[0048]
10 Hereinafter, the present invention will be described in
further detail referring to the embodiments. In the embodiment
of the invention, the performance was evaluated by using the
following techniques.
Evaluation of adsorptivity
15 An adsorbent weighing precisely 1.0 g is put into a 100
mL beaker. 100 mL of oilfield produced water is precisely
measured and put into the beaker. A stirrer is put inside and
mixing occurs by using a magnetic stirrer in order to allow
adsorption for a predetermined time. After this is finished,
20 in the case when fine particles cannot be separated, the fine
particles are promptly separated from the treated water by using
a centrifugal separator, and the liquid is supplied for analysis.
The liquid is supplied to the COD analysis after the adsorbent
is quickly separated from the liquid by using a centrifugal
25 separator.

23
Measurement of COD concentration in the drainage
COD was measured by chemical oxygen demand (CODMn) using
potassium permanganate of the JIS K 0102 test method of
industrial wastewater.
5 Quantitative analysis of acetic acid and propionic acid in the
drainage
Quantity of the concentration of acetic acid and propionic
acid was carried out by ion chromatography.
[0049]
10 First embodiment
Hereinafter, the embodiment of the present invention will
be described referring to Fig. 1. A drainage treatment device
which is one embodiment in the present invention includes a
magnetic separation device which separates the oil content in
15 oilfield produced water, an electrolytic bath 14, a COD
adsorption tank 17, and an exhaust combustion tower 16.
[0050]
The operation of the drainage treatment device will be
explained as follows. First, oilfield produced water 1 is
20 stored in a raw water tank 2. Oil is emulsified and dispersed
in oilfield produced water. Extremely fine mud, sand, and other
solid materials are included in oilfield produced water except
for an organic element and an inorganic ion represented by sodium.
Therefore, oilfield produced water 1 is sent to a coagulation
25 tank 3 and a treatment where the suspended matter is allowed

24
to aggregate to produce floc is carried out by using a coagulant
such as iron 2 sulfate and poly aluminum chloride, etc. and
magnetic particles such as magnetite (Fe3O4) and y-hematite
(Fe2O3), etc.
5 [0051]
Raw water including the floe is sent to a rotary filter
device 4 and the oil content is separated from the floe. A
rotary filter film 5 and a rotary cylinder 6 are provided in
the rotary filter device 4, and a magnetic field generation
10 device such as an electromagnet is placed inside the rotary
cylinder 6 although it is not shown in the figure. The raw
water is filtered by the rotary filter film 5, and the oil content
and floc 7 are separated from the raw water. The oil content
and floc which accumulates over the rotary filter film 5 are
15 removed from the rotary cylinder 6 by spraying cleaning water
and scraping it off using a scraping plate 8, and they are
discharged to outside of the rotary filter device 11. The
filtrate water 90 is sent to the electrolytic bath 14.
[0052]
20 Electrodes 91 and 92 are placed in the electrolytic bath
14. Electrodes 91 and 92 are connected to a potential generation
device 13. After coming into the electrolytic bath 14, the
organic material in the filtrate water 90 is decomposed by
continuously electrolyzing it to become organic materials
25 having smaller molecular weight. Since a high concentration

25
of sodium chroride is dissolved in oilfield produced water,
there is an advantage in the progress of electrolytic reaction.
The components of exhaust gas in the electrolytic bath 14 are
analyzed by using a gas analyzer 31'.
5 [0053]
The hydrocarbon generation reaction takes place by
establishing a current flow in the electrolytic bath 14 and
a volatile organic element is formed. Consequently, it is
exhausted from an exhaust pipe 15 for collecting the volatile
10 organic elements located in the upper part of the electrolytic
bath 14. The exhaust combustion tower 16 for burning and
removing the volatile organic element is placed at the tip of
the exhaust pipe 15, and the flue gas is discharged into the
atmosphere from the duct 30.
15 [0054]
According to the analysis, the volatile organic element
discharged from the electrolytic bath 14 was a saturated
hydrocarbon group such as ethane, ethylene, and cyclopropane,
etc. In the electrolytic bath 14, the preferable material for
20 the electrode which is used for electrolysis is Fe, Ni, Al,
Au, Pt, and SUS. When it is an electrode material where high
current density can be obtained, a reaction occurs in which
hydrocarbon is mainly formed by combining two molecular weights
of carboxylic acid with two protons. A high current density
25 condition is desirable for this, and it is understood from the

26
investigation of the inventors that Pt or a material which is
covered by Pt as a thin film is suitable among the aforementioned
electrode materials.
[0055]
5 It is not necessary to complete the electrolytic reaction
in the electrolytic bath 14, so that the filtrate water 90 can
flow into the electrolytic bath 14 continuously. The organic
elements which are not decomposed in the electrolytic bath 14
and the organic elements where decomposition progresses halfway
10 are sent to either of the COD adsorption tanks 17 or 19 as elements
in the second treated water 180 through a drainage supply tube
18.
[0056]
The COD adsorption tank includes a first COD adsorption
15 tank 17 and a second COD adsorption tank 19. The first COD
adsorption tank 17 is used for a regular operation and the second
COD adsorption tank 19 is installed as a reserve, or the first
and second adsorption tanks are alternatively used. Therefore,
the configurations of the first COD adsorption tank and the
20 second COD adsorption tank are same. The configuration of the
whole adsorption tank will be described as follows referring
to the first COD adsorption tank 17.
[0057]
Although two COD adsorption tanks are provided in the
25 present invention, more adsorption tanks may be provided.

27
Particles of ZSM-5 which is a kind of synthetic zeolite are
filled as the adsorbent 21. A catalytic element is supported
beforehand on the particles of ZSM-5. In the case of this
embodiment, the Ni element is supported so that it becomes 0.5
5 wt% converted on per unit weight of ZSM-5. In addition to ZSM-5,
mordenite has a similar adsorptivity as the components of the
adsorbent 21.
[0058]
The container of the COD adsorption tank of this embodiment
10 has a cylindrical shape and is made of SUS 304. The material
of the container of the COD adsorption tank is not limited to
SUS 304. The COD adsorption tank 17 is placed inside of the
heating furnace 20 and has a structure where the adsorbent 21
can be heated with the COD adsorption tank 17. A hot-air blower
15 22 and a drain tube 23 are installed in the COD adsorption tank
17. The drain tube 23 is placed under the adsorption tank with
the drain valve 2 4.
[0059]
When the adsorptivity of the adsorbent is deteriorated,
20 the flow line of the water to be treated is switched to the
adsorption tank 19 and water in the COD adsorption tank 17 is
drained by opening the drain valve 24 of the adsorption tank
17. Next, hot-air of about 100 to 120°C is blown into the COD
adsorption tank 17 by operating the hot-air blower 22 to dry
25 the adsorbent 21. A structure which discharges from the lower

28
section of the COD adsorption tank by ventilating from the upper
part is preferable.
[0060]
The water content of the adsorbent 21 in the whole COD
5 adsorption tank 17 is decreased to 10% or less by ventilating
for about 30 minutes using the hot-air blower 22. The
ventilation time depends on the tank length of the COD adsorption
tank 17 and the ventilation temperature, so that it is not limited
to this embodiment.
10 [0061]
In order to control and manage the water content of the
adsorbent, a moisture meter 29 may be provided in the ventilation
tube 28 under the adsorption tank. The second treated water
25 passing through the COD adsorption tank 17 is discharged
15 28 after being stored once in the reservoir 27. COD monitors
26 are provided before and after the reservoir and, especially,
are used for management of the COD value (COD≤120 mg/L)of the
drainage.
[0062]
20 A hot-air blower may be used for raising the temperature
to the same level instead of the aforementioned heating furnace
20. In that case, it is preferable that the atmosphere of the
hot-air have atmospheric constituents.
[0063]
25 Figs. 3 are a structural example illustrating an

29
adsorption tower used in the embodiment of the present invention.
Fig. 3A is one where an electric furnace or a microwave furnace
61 is arranged around the adsorption tower in which the COD
adsorbent is filled. The raw water (including COD) 62 is
5 supplied from the bottom of the adsorption tower and exhausted
from the adsorption tower as the treated water 63. The remaining
water in the tower 67 is discharged during regeneration of the
adsorption tower, and the air for combustion 64 is supplied
from the bottom of the adsorption tower, and then the flue gas
10 (including CO2, CO, CH) 65 is introduced into a combustion chamber
66 and burnt.
[0064]
Although Fig. 3B is almost the same as Fig. 3A, high
temperature air or high temperature gas (T≤600°C) 68 is supplied
15 from the bottom of the adsorption tower without installing a
heating furnace around the adsorption tower. The flue gas 69
is introduced into the combustion chamber 66.
[0065]
Fig. 3C is a drawing where the gas turbine exhaust 70
20 is supplied from the top of the adsorption tower, the combustion
air 68 is supplied from the bottom of the adsorption tower,
and the flue gas 69 is exhausted. These configurations of the
adsorption tower are examples, and it is needless to say that
it can be applied to cases other than that in the above-mentioned
25 embodiment.

30
[0066]
Second embodiment
The second embodiment is an example of a test result using
the device shown in the first embodiment.
5 [0067]
Table 3 show measurement results of the CODMn value in
the electrolysis process and the adsorption process.
[0068]
[Table 3]
Treatmentprocess CODMn Aceticacid Propionicacid Methanol
Firsttreatedwater Oil-waterseparation 386 1740 390
Secondtreatedwater Electrolysis 270 1200 222 150
Thirdtreatedwater Adsorptiontreatment 110 410 90 70
10 Unit: mg/L
The first treated water in Table 3 means the results of
analysis where the sample was taken at the first treated water
sampling intake 31 in Fig. 1. The second treated water is one
which is treated by applying an electric field using the electric
15 charging device 13 between the electrodes 91 and 92 placed in
the electrolytic bath 14 of the electrodialysis device.
Although it is not shown in Fig. 1, the analytical sample can
be taken at the midway point of the drainage supply tube 18,
and they are the results of analysis of the collected second

31
treated water 180.
[0069]
After passing through the electrolysis device, the CODMn
value decreased by 116 mg/L. The concentration of acetic acid
5 and the concentration of propionic acid decreased by 540 mg/L
and about by 170 mg/L, respectively. Conversely, methanol is
formed and the concentration thereof becomes 150 mg/L. Thus,
the result in which an electric field was applied to oilfield
produced water and the concentration of the organic acid in
10 oilfield produced water changed indicates that the Kolbe
reaction had progressed.
[0070]
The reason why the CODMn is decreased by electrolysis is
that acetic acid becomes gaseous and released in atmosphere
15 from the second treated water by generating ethane C2H6 according
to the Kolbe reaction shown in the expression (1).
2CH3COO- + 2( + ) → CH3CH3 + 2CO2 (1)
Herein, (+) means a proton.
[0071]
20 An increase in the concentration of ethane was observed
in the result which was analyzed using a gas analyzer 31 placed
at the midway point of the exhaust pipe 15 installed at the
top of the electrolytic bath 14.
[0072]
25 The results in which methanol was formed in the

32
aforementioned embodiment of the invention indicates that the
reaction shown in the expression (2) had progressed.
CH3COO- + OH- + 2( + ) → CH3OH + CO2 (2)
Although the material of the electrodes 91 and 92 used
5 in the invention are Pt (platinum), it is not necessary that
the entire electrode be formed of Pt. The same results can
be obtained by using SUS, Fe, Al, and Ti, etc. where Pt is coated
over the surface. A method for covering the surface with SUS,
Fe, Al, and Ti is an ion plating technique, an evaporation
10 technique, or a sputtering technique, and any of these materials
is effective as an electrode material.
[0073]
Next, the adsorbent 21 will be explained. As a result
of the experiment done by the inventors, the following are
15 confirmed as features of the adsorbent 21. The molar ratio
of SiO2/Al2O3 is preferably 5 or more as an element of the adsorbent
and the molar ratio of SiO2/Al2O3 is preferably 80 or more in
order to adsorb water-soluble organic materials in oilfield
produced water. In the case when a comparison is done of the
20 kind of the organic material which is adsorbate, there is a
tendency that the absorbed amount decreases with an increase
in the carbon number of the organic material. Therefore, it
is desirable that the opening diameter of the pore contributing
to adsorption be from 0.5 to 0.6 nm and the pore contributing
25 to adsorption be formed in a three-dimensional structure.

33
[0074]
Any shape, such as a particle shape and a powder shape,
presents no problem as an adsorbent filled in the adsorption
tower when it has the aforementioned adsorptivity. However,
5 there is a concern that the flow path is not dispersed during
the transport of water in the case when it has a powder shape,
and it results in a pressure drop buildup in the thermal
regeneration process. Then, it is preferable that the powder
shaped adsorbent be molded beforehand in a particle shape, or
10 the adsorbent be supported on a carrier such as a honeycomb,
etc. and placed in the COD adsorption removal tank.
[0075]
Fig. 5 is a concrete example of an adsorption tower in
the embodiment of the present invention. In the figure, a
15 plurality of COD adsorption towers 70 are arranged in series
against the flow of the produced water 85 and the treated water
90 is discharged from the top of the last adsorption tower.
Each adsorption tower 70 comprises a heating furnace 75 which
is used for the regeneration of the adsorbent. Moreover, each
20 adsorption tower comprises a hot-air blower system 80 for drying
the adsorbent during regeneration.
[0076]
Third embodiment
Fig. 6 shows a result of the regeneration of the adsorbent
25 in the present invention. That is, it is a figure showing the

34
relationship between the heating temperature and the amount
of C02, CO and hydrocarbon generated from the adsorbent during
repeated regeneration.
[0077]
5 As shown in Fig. 6, the most appropriate kind of catalytic
element and concentration range thereof can be determined by
adsorbing under the same conditions by using the adsorbent on
a variety of concentrations of catalytic elements, carrying
out the temperature programmed desorption test under the same
10 conditions, and comparing the temperature of the gas generation
peaks of CO2 and/or CO.
[0078]
The test condition to obtain the results shown in Fig.
6 will be explained as follows. Synthetic zeolite ZSM-5 where
15 the SiO2/Al2O3 ration was 90 was used as an adsorbent. First,
5.0 g of the adsorbent was put into a 200 mL beaker and 50 mL
of the second treated water of oilfield produced water is put
therein and stirred for ten minutes. This operation
corresponds to the adsorption process. Then, only the
20 adsorbent is collected by performing a solid-liquid separation
operation by using a centrifugal separator. This adsorbent
is dried by heating in atmosphere at about 100°C.
[0079]
The adsorptivity is evaluated by using the following
25 techniques in Fig. 7 and Fig. 8. 300 mL of oilfield produced

35
water is measured and put into a beaker, and the adsorbent
precisely weighed is put therein. After corking tightly, it
is sufficiently reacted by shaking the mixture or rotating the
mixture for a predetermined time. After the reaction is
5 complete, the adsorbent is quickly filtered and separated from
the treated water. In the case when fine particles can not
be separated, the fine particles are separated from the treated
water by using a centrifugal separator. As mentioned above,
the obtained liquid is analyzed.
10 [0080]
Next, Fig. 7 shows the residual carbon concentration in
the adsorbent and adsorptivity of the regenerated adsorbent
when it is heated in air with a heating rate of 10°C per minute.
[0081]
15 The adsorbent is one where Pt is catalyzed by being
supported on zeolite with a weight ratio of 0.2 wt%. Zeolite
consists of ZSM-5 particles molded by an extrusion technique
to have a diameter of 3 mm and a length of 5 to 20 mm. Using
dinitrodiamine Pt (II) nitrate solution as a raw material, Pt
20 was supported by immersing the aforementioned ZSM-5 particles
in Pt solution diluted with refined water to be the
aforementioned concentration.
[0082]
After the Pt solution was evenly adhered to and impregnated
25 in all particles, the water was evaporated at 120°C and it was

36
heated at 600°C for one hour in atmosphere after evaporating
the water completely.
[0083]
In the beaker oilfield produced water comes into contact
5 with the catalyzed adsorbent formed by the aforementioned method,
and it was stirred for ten minutes. The COD value of oilfield
produced water before being put into the beaker was 600 mg/L.
The stirring period was determined after it had been confirmed
that the COD value of the water after the treatment hardly changed
10 after ten minutes or more. After the stirring was over, the
adsorbent was separated from the treated water; the adsorbent
was dried using a hot-air blower and heated at 300 to 500°C
for one hour; and the carbon concentration in the adsorbent
was quantitatively analyzed after heating.
15 [0084]
The horizontal axis of Fig. 7 is the heating temperature
of regeneration of the catalyzed adsorbent, and it is
corresponded to the regeneration temperature of the adsorbent
in the present invention. The value of the vertical axis is
20 the residual carbon concentration in the adsorbent. When the
regeneration temperature is 400°C or less, the residual carbon
concentration is 0.1 wt% or more. On the other hand, when it
is 400°C or more, the residual carbon concentration is 0.1 wt%
or less. Fig. 8 is a graph in which is shown how much the residual
25 carbon affects the adsorptivity as a function of the change

37
of the CODMn value of the oil pollution water. On the vertical
axis are the COD values of the treated water after performing
the adsorption reaction ten times and regenerating the oilfield
produced water ten times. The CODMn value of the raw water was
5 600 mg/L and the COD value was decreased by adsorption using
a ZSM-5 particle adsorbent which has been repeatedly regenerated
at 300°C and 350°C. However, they did not satisfy the
environmental standard value which is CODMn≤ 120 mg/L. When
the regeneration temperature was 400°C and 500°C, the
10 concentration of the raw water, 600mg/L, decreased to 105 to
110 mg/L, which satisfied the environmental standard value.
It is considered that it becomes difficult to adsorb the COD
elements in the raw water and the adsorptivity is decreased
because the carbon concentration which remains unburnt on the
15 surface of the absorbent is high when the regeneration is
performed at 350°C or less. According to Fig. 8, regeneration
which satisfies the environmental standard value becomes
possible when the regeneration is performed at about 380°C.
[0085]
20 According to the aforementioned embodiment of the present
invention, there is a regeneration process to maintain the
adsorptivity of the adsorbent while adsorbing the COD elements
in oilfield produced water using the adsorbent, so that it
becomes possible to remove the COD elements for a long time.
25

38
Fourth embodiment
Fig. 9 shows a result when the appropriate content of
the Co content is determined for Co which is one kind of catalytic
element for the adsorbent.
5 [0086]
The adsorbent is one where the Co is supported up to a
maximum of 3 wt% of the zeolite weight ratio. The zeolite is
ZSM-5 particles molded by an extrusion technique to have a
diameter of 3 mm and a length of 5 to 10 mm. Using a cobalt
10 nitrate hexahydrate solution as a raw material, Co was supported
by immersing the aforementioned ZSM-5 particles in a Co solution
diluted with the refined water to the aforementioned catalyzed
concentration.
[0087]
15 After the Co solution was evenly adhered to and impregnated
in all the particles, the water is evaporated at 100 to 120°C
and it was heated at 600°C for one hour in air after evaporating
the water completely.
[0088]
20 In the beaker oilfield produced water comes into contact
with the Co impregnated adsorbent formed by the aforementioned
method and it was stirred for ten minutes. The COD value of
oilfield produced water before being put into the beaker was
450 mg/L. The stirring period was assumed to be 10 minutes
25 for the same reason as the embodiment. After stirring was over.

39
the adsorbent was separated from the treated water; the adsorbent
was dried in a constant-temperature drying oven heated at 400°C
for one hour in air; and the carbon concentration remaining
in the adsorbent was quantitatively analyzed after heating.
5 [0089]
The horizontal axis of Fig. 9 shows the Co concentration
which was supported on the ZSM-5 carrier. The vertical axis
shows the ratio of residual C concentration in the adsorbent.
The denominator of the residual C concentration ratio in the
10 vertical axis is the residual C concentration in the adsorbent
after adsorption by an adsorbent (ZSM-5 particles) which does
not contain the catalytic element Co, drying, and heating at
400°C for one hour.
[0090]
15 As is evident from Fig. 9, the most effective range of
the concentration as the catalytic element is obtained when the
residual C concentration ratio is the lowest. Therefore, in
order to support Co on ZSM-5 particles as a catalytic element,
it is understood that the amount of supported Co is preferably
20 about 1 to 2 wt%.
[0091]
In the case when the catalytic element was Mn, it was
recognized that there exists a Mn concentration range where
the residual C concentration becomes lowest, the same as the
25 results for Co. In the case of Mn, the appropriate concentration

40
range for regenerating the adsorbent was from 0.3 to 0.6 wt%.
[0092]
Fifth embodiment
An embodiment applying a drainage treatment system to
5 the treatment of oilfield produced water in an oil mining well
will be explained using Fig.2. However, the present invention
is not limited thereto. In the treatment system for oilfield
produced water shown in Fig. 2, oilfield produced water 100
is stored in a raw water tank 106. Oil is emulsified and
10 dispersed in oilfield produced water. Extremely fine mud, sand,
and other solid materials are included except for an organic
element and sodium. Therefore, raw water which is oilfield
produced water is sent to a coagulation tank 107 and a treatment
where the suspended matter is allowed to aggregate to produce
15 floc is carried out by using a coagulant such as iron (II) sulf ate
and poly aluminum chloride, etc. and magnetic particles such
as magnetite (Fe3O4) and yhematite (Fe2O3), etc. Raw water
including the floe is sent to a rotary filter device 108 and
the oil content is separated from the floe.
20 [0093]
A rotary filter film 109 and a rotary cylinder 111 are
provided in the rotary filter device 108, and a magnetic field
generation device such as an electromagnet is placed inside
of the rotary cylinder 111 although it is not shown in the figure.
25 The raw water is filtered by the rotary filter film 109, and

41
the oil content and floc are separated from the raw water. The
filtered water 110 is sent to a drainage treatment system of
the invention to be mentioned later. The oil content and floe
which accumulates over the rotary filter film 109 are removed
5 from the rotary cylinder 111 by spraying cleaning water and
scraping it off using a scraping plate 112, and they are
discharged to outside of the rotary filter device 108.
[0094]
The filtered water 110 is sent to either the adsorption
10 tower 115a or 115b through a drainage supply tube 104 . Although
two adsorption towers are provided in the present invention,
additional adsorption towers may be provided. The purpose of
preparing two tanks is to carry out the adsorption treatment
in one adsorption tower while carrying out the regeneration
15 treatment in another adsorption tower, so that the drainage
treatment can be performed continuously. Switching the
adsorption towers is done by opening and shutting the valves
117a and 117b. Inorganic system adsorbents 116a and 116b are
filled in the adsorption towers 115a and 115b, respectively.
20 It is preferable that fine particles be used for the raw material
of the absorbent in order to make the surface area of the adsorbent
larger. Although the control of the fine particle is
complicated because they flow out by the flowing water, it is
easy to use them when they are molded in a certain shape and
25 fired. The shape of the molded body may be a rod shape, a pellet

42
shape, a cylinder shape, a honeycomb, or a net shape. It may
be one where adsorbent fine particles are supported by a molded
carrier. As a carrier having a honeycomb or a net shape, it
is preferable that an inorganic material or a metal be used
5 because of the requirement to endure repeated regeneration.
[0095]
An analyzer 130 for analyzing the concentration of sodium
in the drainage is connected with the drainage supply tube 104,
and analyzers 140a and 140b for analyzing the concentration
10 of sodium in the treated water are connected to the treated
water exhaust pipes 121 and 122 at the outlet of the adsorption
tower.
[0096]
Heating elements 118a and 118b for heating adsorbent are
15 provided in the adsorption towers 115a and 115b, and air blast
tubes 120a and 120b are installed through the valves. The air
blast tube is connected to the air supply device which is not
shown in the figure. This heating device and air blast tube
are used when the adsorbent in the adsorption tower is
20 regenerated. That is, when the amount of adsorbed organic
element in the adsorbent increases and the adsorptivity
decreases, the adsorption operation is stopped once, air is
blown in the adsorption tower through the air blast tube, the
adsorbent is heated to a high temperature by using the heating
25 element, and organic elements adsorbed on the adsorbent are

43
burned and removed. At this time, the heating temperature is
preferably controlled to be as low as possible in a range where
the organic compounds can be burnt and removed because
vitrification of the adsorbent progresses easily with
5 increasing temperature. Concretely, the temperature is
preferably 500°C or less and, specifically, 400°C or less is
more preferable. When the regeneration process is carried out
on the adsorbent, the valve 119a or valve 119b is kept closed,
which is provided on the outlet side of the adsorption tower
10 where the operation is performed.
[0097]
In the analyzers 130, 140a, and 140b, sodium concentration
is analyzed continuously or in a given time interval, and the
analytical data are sent to the data gathering device 151 of
15 the control device 150 through the communication line, etc.
Data gathered in the data gathering device 151 are sent to the
arithmetic unit 152. In the arithmetic unit 152, when data
in the analyzer 130 and data in the analyzers 140a and 140b
are compared, and when they become a given condition which is
20 previously established, it is judged that the adsorbent is
poisoned by sodium and dead, and signal is sent to close a valve
where the adsorption operation is going on, that is, either
valve 117a or 117b. The condition when the valves 117a and
117b are closed is the case when the sodium concentrations
25 measured by the analyzers 140a and 140b are greater than the

44
sodium concentration measured by the analyzer 130 as one example.
Or, the sodium concentrations measured by the analyzers 140a
and 140b become a predetermined ratio against the sodium
concentration measured by the analyzer 130. An absorption
5 spectrophotometer, an ion chromatography, and flame atomic
absorption spectrometry, etc. can be used for the analyzers
130, 140a, and 140b.
[0098]
When signal for closing the valve 117a or the valve 117b
10 is sent by the control device 150 and the drainage supply to
the adsorption tower is stopped, the adsorbent filled in the
adsorption tower is exchanged or the treatment is carried out
to remove the sodium. The function being performed in the
control device 150 can be carried out by reading the program
15 which has this function. Moreover, this function may be carried
out by recording the program in the recording medium and reading
it in the control device.
[0099]
Next, various experimental results will be described.
20 Experiment 1
300 mL of oilfield produced water was put into a
polyethylene reagent bottle, the adsorbent was put therein and
corked tightly, and the oilfield produced water and the adsorbent
were mixed by stirring by vibration of the reagent bottle for
25 about 30 minutes. After that, the adsorbent was separated from

45
the water by using filter paper and the rate of decrease in
the COD element in water was analyzed. Measurement of the rate
of the decrease in COD was carried out by the COD analysis method
using potassium permanganate in the JIS K 0102 test method of
5 industrial wastewater. Eight kinds of synthetic zeolite from
No. 1 to No. 8, which are shown in Table 5 and had different
silica/alumina molar ratios and specific surface areas were
used for the adsorbent. Moreover, as oilfield produced water,
two kinds of raw water, a first raw solution and a second raw
10 solution shown in Table 4, were used. Acetic acid, propionic
acid, butyric acid, valeric acid, succinic acid, lactic acid,
acetone, methyl ethyl ketone, trichloroethylene,
tetrachloroethylene, benzene, toluene, ethylbenzene, xylene,
phenol, cresol, xylenol, hexachlorobenzene, and carbon
15 disulf ide, etc. are contained in these oilfield produced waters
and all of them become factors which increase COD. The rate
of COD decrease of the treated water is shown in Table 4. The
higher the rate of decrease in the COD element, the more the
amount of organic element adsorbed on the adsorbent, resulting
20 in the amount of the organic element contained in the drainage
after treatment being smaller.
25

46
[Table 4]
First raw water Second raw water
Contents Concentration(mg/L) Concentration(mg/L)
NaCl 36000 16000
Acetic acid 2000 120
Propionic acid 500 40
Ketones 3 10
Phenols 30 60
Benzenes <1.0 <1.0
CODcr 7500 1980
[0101]
[Table 5]
Zeolites Rate of COD decrease(%) Silica/Alumina(molar ratio) Specificsurfacearea (m2/g)
First rawwater Second rawwater
No. 1 34.4 47.4 6 550
No. 2 12.5 31.6 6 230
No. 3 7.8 31.6 17 360
No. 4 32.8 62.6 18 170
No. 5 12.5 26.3 40 330
No. 6 31.3 86.3 200 400
No. 7 42.1 81.1 240 420
No. 8 28.1 64.2 510 750
5
In zeolites No. 1 to 8, higher rates of COD decrease were
obtained in the No.6 zeolite and the No. 7 zeolite in either
the first raw solution or the second raw solution. The
silica/alumina molar ratio and specific surface area do not
10 affect the rate of COD decrease.
(Experiment 2)
The second raw solution shown in Table 4 and the synthetic
zeolite shown as No. 7 in Table 5 were put into a reagent bottle

47
and mixing by stirring for one hour. After that, the second
raw solution was exchanged for a new one and mixed by stirring
for one hour and the exchange of raw solution was repeated five
times, and then the adsorbent was taken out from the reagent
5 bottle and heated to a high temperature. The heating
temperature was changed four ways in the range from 120°C to
700°C. Then, the specific surface area and the carbon content
of the adsorbent were measured. The carbon content was measured
by a high-frequency combustion infrared absorption method and
10 the specific surface area was measured by a BET method.
[0102]
[Table 6]
Sample Rawmaterial Afteruse Afteruse Afteruse Afteruse
Heatingtemperature(°C) 120 300 500 700
C content(weight %) 0 0.3 0.28 <0.01 <0.01
Specificsurfacearea (m2/g) 390 385 390 395 390
In Table 6, what is shown as "raw material" means the
15 state before using the experiment, and what is shown as "after
use" means the state where adsorption and regeneration were
repeated five times. When the heating temperature was 500°C
and 700°C, the residual carbon content in the adsorbent was
extremely small and it became almost the same state as that
20 before use. On the other hand, when the heating temperature

48
was 120°C and 300°C, the carbon content was large and the organic
elements were not fully combusted, so that the ratio remaining
therein became high. From these results heating it up to 500°C
or more is preferable to effectively burn off the organic
5 elements. However, since the adsorbent is easily vitrified
when the heating temperature becomes high, the heating
temperature is preferably controlled to be as low as possible,
and it is preferable that the organic elements be burned by
supporting a catalytic element and heating at a temperature
10 of 400°C or less. 500°C or less is preferable and, concretely,
the most preferable temperature is in the range from 400 to
450°C.
[0103]
The specific surface area almost does not change in the
15 range of heating temperature from 120 to 700°C, and the effects
of the heating temperature are small in this temperature range.
(Experiment 3)
An experiment which repeats the adsorption and
heat-regeneration was carried out by using synthetic zeolite
20 as the adsorbent where the peak intensity of the X-ray
diffraction pattern exists at 28=22.98° before adsorption as
shown in Fig. 4. The experiment was carried out as follows;
the adsorbent and the first raw liquid shown in Table 3 were
put into a reagent bottle, it was mixed by stirring for one
25 hour and taken out therefrom and regenerated by heating at 600°C,

49
and the adsorbent was put into the reagent bottle with the new
first raw solution and, after that, similar operations were
repeated. Fig. 4 shows the X-ray diffraction peaks of the
adsorbent before adsorption, that is, a new adsorbent, of the
5 adsorbent where adsorption and heat-regeneration were carried
out twenty times each, and of the adsorbent where adsorption
and heat-regeneration were carried out fifty times each.
Measurement of the X-ray diffraction pattern was done by using
a powder X-ray diffraction method. In Fig. 4, the peak position
10 of 28=22.98° means that this adsorbent includes SiO2. When the
adsorption and regeneration are repeated, another peak appears
at the position of 20=21.68° and the intensity at this position
becomes higher with increasing frequency of adsorption and
regeneration. The position means that sodium exists, that is,
15 it starts vitrifying. According to Fig. 4, the degree of
vitrification increases with increasing frequency of
adsorption and regeneration.
[0104]
Fig. 11 shows the rate of COD decrease in COD of the drainage
20 after treatment and the change of the sodium concentration with
increasing operating time of the adsorbent. The arrows in the
figure mean that the value becomes greater while going in that
direction, for instance, that the Na concentration in the
drainage becomes higher. The interval between measurement
25 points is about ten hours. Actually, since regeneration is

50
performed with every one hour of adsorption, ten times adsorption
and regeneration are carried out, respectively, in ten hours.
It is understood that the rate of decrease in COD decreases
with increasing operating time. On the other hand, the sodium
5 concentration in the drainage increases with increasing
operating time. Thus, it was confirmed that sodium accumulates
in the adsorbent with increasing operating time and the
adsorption removal rate of the organic elements decreases even
when adsorption and regeneration were repeated. Therefore,
10 measuring sodium concentration in the drainage before and after
coming into contact with the adsorbent is extremely effective
to judge the life of the adsorbent.
[0105]
Sixth Embodiment
15 Another embodiment of the present invention will be
explained as follows referring to Figs. 12 and 1. In the present
invention, as shown in Fig. 12, electrolysis is not applied
to the water to be treated and air 114 is supplied using a blower
from underneath the filler 113 filled in the aeration tank 12,
20 which is different from Fig. 1. Other points are the same as
Fig. 1, so that same codes will be used to explain. A drainage
treatment device 10 of the embodiment in the present invention
includes a magnetic separation device 11 which separates the
oil content in oilfield produced water, an aeration tank 12,
25 a COD adsorption tank 17, and an exhaust combustion tower 16.

51
[0106]
The operation of the drainage treatment device 10 will
be explained as follows. First, oilfield produced water 1 is
stored in a raw water tank 2. Oil is emulsified and dispersed
5 in oilfield produced water. Extremely fine mud, sand, and other
solid materials are included in oilfield produced water except
for organic elements and sodium. Therefore, oilfield produced
water 1 is sent to a coagulation tank 3 and a treatment where
the suspended matter is allowed to aggregate to produce floe
10 is carried out by using an adsorbent such as iron (II) sulfate
and poly aluminum chloride, etc. and magnetic particles such
as magnetite (Fe3O4) and γ-hematite (Fe2O3), etc. Raw water
including the floc is sent to a rotary filter device 4 and the
oil content is separated from the floc. A rotary filter film
15 5 and a rotary cylinder 6 are provided in the rotary filter
device 4, and a magnetic field generation device such as an
electromagnet is placed inside the rotary cylinder 6 though
it is not shown in the figure. The raw water is filtered by
the rotary filter film 5, and the oil content and floc 7 are
20 separated from the raw water. The oil content and floc which
accumulate over the rotary filter device 5 are removed from
the rotary cylinder 6 by spraying cleaning water and scraping
it off using a scraping plate 8, and they are discharged to
outside of the rotary filter device 11.
25 [0107]

52
The filtered water 90 is sent to the aeration tank 12.
The filler 113 is filled in the tower in the aeration tank 12
and the blower 114 is placed to blow air from underneath the
filler. After the filtered water 90 flows into the aeration
5 tank 12, volatile organic elements are discharged from the
exhaust pipe 15 which is placed at the top of the tower. The
exhaust combustion tower 16 for burning and removing the volatile
organic elements is placed at the tip of the exhaust pipe 15.
According to the analysis, the volatile organic elements
10 exhausted from the aeration tank 12 are ketones such as acetone,
etc. and benzenes.
[0108]
Elements which are difficult to volatilize in the filtered
water 90 are sent to either the first COD adsorption tank 17
15 or the second COD adsorption tank 19 from the bottom of the
aeration tank 12 as aerated processed water 180 through the
drainage supply tube 18. This aerated processed water 180 is
the second treated water. The COD adsorption tank includes
a first COD adsorption tank 17 and a second COD adsorption tank
20 19. The first COD adsorption tank 17 is used for a regular
operation and the second COD adsorption tank 19 is installed
as a reserve. Therefore, the configurations of the first COD
adsorption tank and the second COD adsorption tank are the same.
The configuration of the whole adsorption tank will be described
25 as follows referring to the first COD adsorption tank 17.

53
Although two COD adsorption tanks are provided in the present
invention, more adsorption tanks may be provided.
[0109]
Particles of ZSM-5 which was a kind of synthetic zeolite
5 were filled therein as the adsorbent 21. A catalytic element
was supported beforehand on the particles of ZSM-5. In the
case of this embodiment, Pt element was supported to be 0.2
wt% converted on the basis of a unit weight of ZSM-5. Mordenite
has a similar adsorptivity as the element of the adsorbent 21
10 besides ZSM-5.
[0110]
The container of the COD adsorption tank is formed of
SUS 304 with a cylindrical shape. The material of the container
of the COD adsorption tank is not limited to be SUS 304. The
15 COD adsorption tank 17 is placed inside of the heating furnace
20 and it has a structure where the adsorbent 21 can be heated
with the COD adsorption tank 17. A hot-air blower 22 and a
drainage tube 23 are installed in the adsorption tank 17. The
drainage tube 23 is placed at the bottom of the adsorption tank
20 with the drain valve 24.
[0111]
When the adsorptivity of the adsorbent is deteriorated,
water in the COD adsorption tank 17 is drained by opening the
drain valve 24. Next, inside of the COD adsorption tank 17
25 is dried. Hot-air of about 100 to 120°C is blown into the COD

54
adsorption tank 17 by operating the hot-air blower 22 to dry
the adsorbent 21. A structure is preferable where air is blown
from the upper part and exhausted while there is draining from
the bottom of the COD adsorption tank.
5 [0112]
The water content of the adsorbent 21 in the whole COD
adsorption tank 17 was decreased to 10% or less by ventilating
for about 30 minutes using the hot-air blower 22. The
ventilation period depends on the tank length of the COD
10 adsorption tank 17 and the ventilation temperature, so that
it is not limited to this embodiment.
[0113]
In order to control and manage the water content of the
adsorbent, a moisture meter 29 may be provided in the ventilation
15 tube 28 under the adsorption tank.
[0114]
The treated water 25 passing through the COD adsorption
tank 17 is discharged 28 after being stored in the reservoir
27 once. COD monitors 26 are provided before and after the
20 reservoir and, especially, are used for management of the COD
value (COD^120 mg/L) of the drainage.
[0115]
Although the aeration tank 12 was used in the
aforementioned drainage treatment device 10, a vacuum distiller,
25 an electrolytic device, or a hypochlorite reactor may be used

55
instead of the aeration tank 12 according to the nature of the
raw water.
[0116]
Moreover, an electrolytic device may be installed in the
5 fore part of the aeration tank 12, which is a separation removal
device. At this time, the electrolytic device 14 and the
aeration tank 12 may be combined with each other by providing
the blower 114 in the part lower than the electrodes 91 and
92 of the electrodialysis device. Moreover, the aeration tank
10 may be placed in the fore part and the electrolytic device may
be placed in the aft part.
[0117]
According to the present invention, since the
regeneration process is included in order to maintain the
15 adsorption ability of the adsorbent while the COD elements in
oilfield produced water is adsorbed, removal for a long time
becomes possible.
Industrial Applicability
[0118]
20 The present invention can be applied to a treatment to
render oilfield produced water harmless, which is obtained by
collecting crude oil from a mixture of crude oil and salt water
mined in the oilfield etc., and the treated water can satisfy
environmental standard regulations.
25

56
Claims
[1]
A method for removing dissolved organic material in
oilfield produced water comprising the steps of:
5 bringing an adsorbent into contact with oilfield produced
water obtained by separating crude oil from a mixture of crude
oil and salt water;
adsorbing and removing the dissolved organic material
in oilfield produced water; and
10 desorbing the material to be adsorbed from the adsorbent
and regenerating the adsorbent.
[2]
A method for removing dissolved organic material in
oilfield produced water according to claim 1,
15 wherein oil is separated from oilfield produced water
before oilfield produced water is brought into contact with
the adsorbent.
[3]
A method for removing dissolved organic material in
20 oilfield produced water according to claim 1,
wherein oil-drops in oilfield produced water are
separated by performing magnetic separation to oilfield
produced water.
[4]
25 A method for removing dissolved organic material in

57
oilfield produced water according to claim 1,
wherein the adsorbent has a particle shape, a pellet shape,
a rod shape, a fiber shape, a plate shape, a molded body, or
a combination thereof.
5 [5]
A method for removing dissolved organic material in
oilfield produced water according to claim 1,
wherein the adsorbent is kept in a certain section in
oilfield produced water and maintained in a state where it can
10 be easily separated from oilfield produced water.
[6]
A method for removing dissolved organic material in
oilfield produced water according to claim 5,
wherein the adsorbent has a powder shape, a pellet shape,
15 a rod shape, or a combination thereof, and the average diameter
is 1 to 10 mm.
[7]
A method for removing dissolved organic material in
oilfield produced water according to claim 6,
20 wherein the adsorbent is an inorganic adsorbent including
SiO2-Al2O3 or SiO2-Al2O3-Na2O as a main element.
[8]
A method for removing dissolved organic material in
oilfield produced water according to claim 7,
25 wherein another metallic element is supported by said

58
inorganic adsorbent.
[9]
A method for removing dissolved organic material in
oilfield produced water according to claim 1,
5 wherein the adsorbent is activated carbon.
[10]
A method for removing dissolved organic material in
oilfield produced water according to claim 1,
wherein at least two kinds of adsorbents with different
10 pore size are included.
[11]
A method for removing dissolved organic material in
oilfield produced water according to claim 10,
wherein two kinds of adsorbents having a pore size of
15 about 7 angstroms or less and a pore size of about 7 angstroms
or more are included.
[12]
A method for removing dissolved organic material in
oilfield produced water according to claim 1,
20 wherein the adsorbent is heated in an oxidizing atmosphere
for desorption and regeneration of the adsorbent.
[13]
A method for removing dissolved organic material in
oilfield produced water according to claim 1,
25 wherein an organic material in the desorbed material is

59
decomposed or burnt by heating the desorbed material of the
adsorbent.
[14]
A method for removing dissolved organic material in
5 oilfield produced water according to claim 1,
wherein air is supplied to an adsorbent layer for
desorption.
[15]
A method for removing dissolved organic material in
10 oilfield produced water according to claim 1,
wherein a step is included in which a coagulant is added
in oilfield produced water to remove suspended matter before
a contact-treatment of the adsorbent with oilfield produced
water.
15 [16]
A method for removing dissolved organic material in
oilfield produced water according to claim 1,
wherein a step is included in which oilfield produced
water is flown between electrodes to which an electric field
20 is applied and dissolved organic molecules in oilfield produced
water are decomposed before a contact-treatment of the adsorbent
with oilfield produced water.
[17]
A method for removing dissolved organic material in
25 oilfield produced water according to claim 1,

61
system adsorbent or not is judged on the basis of both measured
values.
[20]
A method for removing dissolved organic material in
5 oilfield produced water comprising;
an oil-water separation process where the oil content
and undissolved particles floating and suspended in oilfield
produced water.
a process where dissolved organic material in treated
10 water passing through said oil-water separation process is
electrolyzed,
a separation removal process where an organic element
is separated and removed from a second treated water from the
electrolytic process,
15 an adsorption removal process where an organic element
is adsorbed and removed from a third treated water passing
through said separation removal process,
a combustion process where amixture of the organic element
separated and removed in said separation removal process and
20 the organic element separated and removed in said adsorption
removal process is burned and exhausted.
[21]
A method for removing dissolved organic material in
oilfield produced water according to claim 20,
25 wherein an inorganic system adsorption and removal agent

62
is used in said adsorption removal process, said inorganic system
adsorption and removal agent after adsorbing and removing the
organic element being used repeatedly by desorbing and
regenerating at 380 to 600°C in atmosphere.
5 [22]
A device for removing dissolved organic material in
oilfield produced water comprising;
a means for forming oilfield produced water by separating
crude oil from a mixture of crude oil and salt water,
10 a means for holding an adsorbent having adsorptivity for
dissolved organic material in oilfield produced water,
a means for bringing said oilfield produced water into
contact with said adsorbent,
a means for regenerating the adsorbent on which said
15 dissolved organic material is adsorbed.
[23]
A device for removing dissolved organic material in
oilfield produced water according to claim 22,
wherein the means for contacting is a plurality of
20 adsorption towers in which an adsorbent is filled.
[24]
A device for removing dissolved organic material in
oilfield produced water according to claim 23,
wherein said plurality of adsorption towers are arranged
25 in parallel against the flow of oilfield produced water to be

63
treated.
[25]
A device for removing dissolved organic material in
oilfield produced water according to claim 22,
5 wherein different kinds of adsorbents are arranged in
series or parallel against the flow of oilfield produced water
to be treated.
[26]
A device for removing dissolved organic material in
10 oilfield produced water according to claim 22,
wherein a microwave heating device for heating said
adsorbent is included.
[27]
A device for removing a dissolved organic material in
15 oilfield produced water according to claim 22,
wherein a means is provided for magnetically separating
crude oil from salt water associated with crude oil.
[28]
A system for removing dissolved organic material in
20 oilfield produced water according to claim 22,
wherein a means for detecting the concentration of salt
in salt water and a means for controlling said removal device
on the basis of a signal from said detection means.
[29]
25 A system for removing dissolved organic material in

64
oilfield produced water comprising;
a drainage treatment system for removing dissolved
organic material contained in the drainage by bringing the
drainage including an organic element and sodium into contact
5 with an inorganic system adsorbent,
wherein a control device is included in which supply of
drainage to said inorganic system adsorbent is stopped on the
basis of the sodium concentrations in the drainage to be
contacted with said inorganic system adsorbent and in the
10 drainage to be discharged from said inorganic system adsorbent.
[30]
A system for removing dissolved organic material in
oilfield produced water according to claim 29,
wherein an analyzer is provided for analyzing the sodium
15 concentration by collecting a part of the drainage to be
contacted with said inorganic system adsorbent and an analyzer
for analyzing the sodium concentration in the drainage which
is discharged from said inorganic system adsorbent.
[31]
20 A system for removing dissolved organic material in
oilfield produced water according to claim 30,
wherein said control device comprises a data gathering
device for gathering analytical data measured by said two
analyzers and an arithmetic unit for sending a signal to stop
25 the drainage supply to said inorganic system adsorbent on the

65
basis of data accumulated in said data gathering device.
[32]
A system for removing dissolved organic material in
oilfield produced water comprising;
5 an oil-water separation tank where oil content and
undissolved particles floating and suspended in the drainage
are removed,
an electrolytic means where an organic element is
decomposed in the drainage passing through the oil-water
10 separation tank,
a separation removal tank where an organic element is
separated and removed from second treated water passing through
said electrolytic means,
an adsorption removal tank where an organic element is
15 adsorbed to an inorganic system adsorbent and removed from third
treated water passing through said separation removal tank,
a combustion chamber where the organic element separated
and removed in the separation removal tank and the organic
element separated and removed in the adsorption removal tank
20 are mixed, burned, and exhausted.
[33]
A system for removing dissolved organic material in
oilfield produced water according to claim 32,
wherein, after the organic element is adsorbed and removed,
25 the inorganic system absorbent is heated at 380°C to 600°C in

66
atmosphere for regeneration and repeatedly used.
[34]
A system for removing dissolved organic material in
oilfield produced water according to claim 32,
5 wherein said oil-water separation tank also works as a
magnetic separation tank and an electrolytic bath.
[35]
A system for removing dissolved organic material in
oilfield produced water according to claim 32,
10 wherein said inorganic system adsorption removal agent
includes silica and aluminum oxide and the ratio of silica and
aluminum oxide is 5 or more as a SiO2/Al2O3 molar ratio, and
wherein the micro pores of the adsorbent has a three
dimensional network structure.
15 [36]
A system for removing dissolved organic material in
oilfield produced water according to claim 32,
wherein said separation removal tank is a separation
removal tank in which a volatile organic compound is separated
20 and removed by ventilating said second treated water.

A method and a device for removing dissolved organic
material in oilfield produced water which are characterized
by bringing an adsorbent into contact with oilfield produced
water obtained by separation of crude oil from a mixture of
crude oil and salt water, adsorbing and removing dissolved
organic material in the emulsion, and regenerating the
adsorbent