JP2000350984A - Method and apparatus for treating oil-containing waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove an oil component in oil-containing waste water high in concn. up to a concn. possible to discharge. SOLUTION: The greater part of an oil component in oil-containing water high in concn. is removed in a pressure flotation treatment tank 11 to obtain treated water, which is, in turn, allowed to flow to a bioreactor 13 packed with a petroleum adsorbing. material not only to adsorb the oil component by the petroleum adsorbing material 33 but also to decompose the adsorbed oil by petroleum decomposing bacteria.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating oil-containing wastewater from factories and the like.

[0002]

2. Description of the Related Art Conventionally, wastewater containing a large amount of cutting oil from a factory or wastewater such as bilge wastewater of ships contains tens of thousands to hundreds of thousands of ppm of oil.

[0003] The treatment of the oil-containing wastewater is carried out first by pressurized flotation, that is, by blowing pressurized air into the oil-containing wastewater, and the foam of the blown compressed air causes the oil to float to remove most of the wastewater from the wastewater. The oil is separated and removed, and then the dilute oil remaining in the treated wastewater at a concentration of several hundred ppm is purified using activated carbon to several ppm or less.

[0004]

However, since the treated water after the pressurized flotation treatment contains several hundred ppm of oil, the load on the activated carbon is large unless this is reduced to several tens of ppm or less. The cycle for regenerating activated carbon is shortened and the cost is increased.

[0005] As described above, it is usually difficult to apply the pressure flotation method for the purpose of separating oil at a high concentration, and when passing through an adsorbent such as activated carbon, if the oil concentration is not reduced as much as possible, it will be immediate. Oil saturation occurs, and there are problems such as clogging.

Therefore, in order to reduce the oil load on the activated carbon, a device for removing an oil having a relatively low concentration of about several hundred ppm is incorporated downstream of the pressurized flotation device and before the oil is removed by the activated carbon. Have been tried.

[0007] In this pressure flotation treatment, several hundred ppm
When removing the oil content that has become diluted by
Since the surfactant contained in the wastewater does not float on the water surface and exists in a form dissolved in the water, it is conceivable to separate oil using a membrane separation device such as a hollow fiber membrane. There is a problem that running costs increase due to separation.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide an oil-containing wastewater treatment method and an apparatus thereof that can efficiently remove oil components in high-concentration oil-containing wastewater to a concentration that can be discharged.

[0009]

In order to achieve the above object, an invention according to claim 1 is to remove most of the oil content in high-concentration oil-containing wastewater by pressurized floating treatment. This is an oil-containing wastewater treatment method in which water is flowed into a bioreactor filled with a petroleum adsorbent to adsorb oil to the petroleum adsorbent and decompose the adsorbed oil by petroleum-degrading bacteria.

The second aspect of the present invention is the method for treating oil-impregnated wastewater according to claim 1, wherein high-concentration oil-impregnated wastewater and pressurized air are mixed in a pressurized tank and then subjected to pressure flotation treatment.

According to a third aspect of the present invention, a pressurized flotation tank for levitation and separation of oil in high-concentration oil-containing wastewater with pressurized air, and treated water in the pressurized flotation tank are continuously introduced to adsorb oil. An oil-containing wastewater treatment apparatus comprising a bioreactor filled with a material and decomposing oil adsorbed on the petroleum adsorbent with petroleum-degrading bacteria.

According to a fourth aspect of the present invention, there is provided the oil-impregnated wastewater treatment apparatus according to the third aspect, wherein a pressurized tank for premixing the oil-impregnated wastewater and the pressurized air is connected to the pressurized floating treatment tank.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows the flow of the oil-containing wastewater treatment of the present invention.

The oil-impregnated wastewater treatment apparatus of the present invention comprises a pressurized tank 10 for mixing high-concentration oil-impregnated wastewater and pressurized air, and introducing the oil-impregnated wastewater and pressurized air from the pressurized tank 10 into the wastewater. A pressurized flotation tank 11 for separating and floating oil, and treated water in the pressurized flotation tank 11 are continuously introduced, the oil is adsorbed by the filled oil adsorbent 12, and the oil is decomposed by petroleum-degrading bacteria. The bioreactor includes a bioreactor 13 and a post-treatment device 14 for adsorbing and discharging oil contained in the treated water from the bioreactor 13. In addition, a scum storage tank 15 for storing the oil separated by flotation is connected to the pressurized flotation tank 11.

Hereinafter, this will be described in more detail.

In the pressurized tank 10, tens of thousands to hundreds of thousands ppm
Oil-impregnated wastewater supply line 1 in which a booster pump 16 for increasing the pressure of high-concentration oil-impregnated wastewater containing oil and an on-off valve 17 are connected
8 is connected, and the compressor 19 and the on-off valve 20
Is connected to the pressurized air supply line 21 to which is connected.

The oil-containing wastewater and pressurized air premixed in the pressurized tank 10 are supplied to the pressurized floating treatment tank 11 through a supply line 23 through an on-off valve 22.

The pressurized flotation tank 11 is separated by a separator 24 into a flotation separation chamber 25 and a treated water recovery chamber 26.
The separator 24 is formed so as to form a gap with the upper and lower walls of the pressurized flotation tank 11 vertically.
The space between the flotation separation chamber 25 and the treated water recovery chamber 26 is communicated, and the processing liquid in the flotation separation chamber 25 is supplied to the treated water recovery chamber 2 through a gap below.
6 and a venturi tube 27 is provided at the top of the pressurized flotation tank 11.

An inlet 23a of the supply line 23 is provided at the lower part of the floating separation chamber 25, and an overflow pipe 28 for recovering the oil separated by floating is provided at the upper part. An opening / closing valve 29 is provided below the overflow pipe 28 through an on-off valve 29. The scum storage tank 15 is connected.

A drain port 30 is provided in the treated water recovery chamber 26 in accordance with the position of the overflow pipe 28, and the drain port 30 is connected to the bioreactor 13 via a treated water line 31.
Is connected.

The bioreactor 13 includes a packed bed 34 in which a petroleum adsorbent 33 made of a synthetic fiber or the like is filled in a container 32.
The treated water line 31 is connected to the upper part of the container 32, and the treated water drain line 35 after the decomposition treatment is
And an air line 3 to which a blower 36 and an on-off valve 37 are connected to blow air from the bottom of the container 32.
8 is connected.

The drainage line 35 is connected to a post-processing device 14 filled with activated carbon or the like via an on-off valve 39, and then the discharge line 41 is connected to the processing device 14 via a drainage valve 40.
Is connected.

In the drain line 35, a T-shaped joint 45 is connected to a rising line 35a rising upward from an on-off valve 39, and an air introduction line 46 extending upward is connected to the T-shaped joint 45. A discharge line 35b extending horizontally and bent downward is connected, and the post-processing device 14 is connected to the discharge line 35b. A Venturi tube 47 is provided on the top of the container 32 of the bioreactor 13.

As described above, after the drainage line 35 has been raised, the drainage line 35 is leveled by the T-shaped joint 45 and then lowered.
By providing the venturi tube 47 at the top of the two, the liquid level of the treated water in the bioreactor 13 is maintained at the position of the T-shaped joint 45.

Reference numeral 42 denotes a discharge valve connected to the pressurized tank 10, reference numeral 43 denotes a waste oil line for discharging oil accumulated in the scum storage tank 15, and reference numeral 44 denotes a valve connected to the line 43.

In the above, oil-containing wastewater having a concentration of tens of thousands to hundreds of thousands of ppm is supplied from the oil-containing wastewater supply line 18 into the pressurized tank 10 by the booster pump 16 and simultaneously from the compressor 19 via the pressurized supply line 21. After the pressurized air is supplied into the pressurized tank 10 and the oil-containing wastewater and the pressurized air are premixed in the pressurized tank 10, the flotation separation chamber of the pressurized flotation tank 11 is supplied from the inlet 23 a of the supply line 23. It is blown into 25 treated waters.

Due to this blowing, the pressurized air rises in the treated water as bubbles, and the oil contained in the treated water also rises with the bubbles, so that most of the oil in the oil-containing wastewater is floated and separated by the bubbles.

At this time, the oil-containing wastewater and the pressurized air are premixed in the pressurized tank 10 and blown into the treated water in the flotation chamber 25, so that the oil and the air are mixed and the compressed air expands. It becomes fine air bubbles and efficiently captures oil and separates and floats from the treated water.

The oil floating from the treated water flows down from the overflow pipe 28 to the scum storage tank 15 and is appropriately drained from the waste oil line 4.
3 to be disposed of as industrial waste.

Most of the oil content can be separated and removed in the flotation separation chamber 25 of the pressurized flotation treatment tank 11, but several hundred ppm of oil remains in the treated water, which is transferred from the treated water recovery chamber 26 to the treated water line 31 via the treated water line 31. It is supplied to the reactor 13.

In the bioreactor 13, the oil adsorbent 3
3, the oil in the treated water is adsorbed by the petroleum adsorbent 33, and the adsorbed oil is decomposed by petroleum-degrading bacteria.

FIG. 2 schematically shows a state in which an oil component in the petroleum adsorbent 33 and the treated water is adsorbed and decomposed and removed by petroleum degrading bacteria.

First, as shown in FIG. 2 (a), when treated water is continuously passed through the oil adsorbent 33, the oil o in the treated water adheres to the oil adsorbent 33 as shown in FIG. 2 (b). Or adsorbed.

The oil o adsorbed by the oil adsorbent 33 is
As shown in FIG. 2C, the petroleum-degrading bacteria p immobilized on the oil adsorbent 33 as shown in FIG. Decomposes the oil o while growing.

The oil is decomposed by the petroleum-degrading bacteria p. First, petroleum molecules having a long-chain structure are decomposed into petroleum molecules having a short-chain structure, which are further decomposed into organic acids and fatty acids, and further decomposed into water. The petroleum-degrading bacteria p grow while decomposing to carbon dioxide.

This petroleum-degrading bacterium p is a bacterium normally contained in activated sludge. After oil is adsorbed on the petroleum adsorbent 33, activated sludge is added to propagate and fix the petroleum-degrading bacterium p. Since the growth of the petroleum-degrading bacteria p needs to be maintained in an aerobic atmosphere, air is blown into the bioreactor 13 from the air line 38.

Normally, the oil is adsorbed by the oil adsorbent 33 when the treated water is continuously flowed, and after a certain period of time, the oil that can be adsorbed becomes saturated and the oil can no longer be adsorbed. By decomposing with the fixed petroleum-degrading bacteria, the adsorption capacity is always kept constant, and the oil is efficiently decomposed by the action of the petroleum-degrading bacteria while adsorbing the oil component in the treated water.

In this case, if the high-concentration oil-containing wastewater is passed directly to the bioreactor 13, the oil adsorption capacity and the resolution by the petroleum-decomposing bacteria do not match, and the oil adsorption by the oil adsorbent becomes saturated, causing clogging. By reducing the oil concentration to several hundred ppm in the pressure flotation tank 11 in the former stage, the matching between the adsorption capacity and the resolution by the petroleum-degrading bacteria becomes good.

The oil concentration after the decomposition treatment by the bioreactor 13 is several tens of ppm. The treated water is passed from the drain line 35 to the post-treatment device 14 filled with activated carbon or the like to adsorb and remove the oil component, and is discharged from the discharge line 41 to the oil component. Concentration number p
Discharge as pm wastewater.

As described above, the post-processing device 14 has several tens of
Since the treated water having an oil concentration of pm is supplied, the cycle of regeneration of activated carbon or the like becomes longer and the efficiency becomes higher.

FIG. 3 shows data on the daily change of the oil resolution by the bioreactor, wherein a shows the daily change of the oil concentration of the treated water flowing into the bioreactor, and b shows the oil concentration of the present invention. The daily change in the oil concentration of the treated water after treatment with the petroleum degrading bacteria immobilized on the adsorbent, and c is a comparison when the activated sludge is retained without filling the petroleum adsorbent in the bioreactor. 5 shows the daily change of the oil concentration of the treated water after the treatment.

In this case, the oil concentration was determined by the concentration of the n-hexane extract (mg / L = ppm).

As shown in FIG. 3, the oil concentration of the inflowing treated water treated in the pressurized flotation treatment tank and flowing into the bioreactor 13 is as follows:
It is 300 to 500 ppm, but when treated with the bioreactor of the present invention, a concentration of about 30 ppm can be obtained as shown in b. On the other hand, as shown in FIG.
It can only degrade oil up to a concentration of 00 ppm.

[0045]

In summary, according to the present invention, the treated water having an oil concentration of several hundred ppm after pressure flotation is continuously passed through the bioreactor filled with the petroleum adsorbent, whereby the oil is adsorbed on the petroleum adsorbent. By adsorbing and decomposing the adsorbed oil by assimilating petroleum-degrading bacteria and growing the petroleum-degrading bacteria, it is possible to reduce the load when subsequently adsorbing with activated carbon, etc. and release the wastewater, and it is easy to maintain and manage become.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention.

FIG. 2 is a schematic view illustrating oil adsorption by a petroleum adsorbent and decomposition by petroleum-decomposing bacteria in the present invention.

FIG. 3 is a view showing experimental data of oil decomposition in treated water in the bioreactor according to the present invention.

[Explanation of symbols]

 11 Pressure flotation tank 13 Bioreactor 33 Petroleum adsorbent

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Sakae Fukunaga 1 Shin-Nakahara-cho, Isogo-ku, Yokohama-shi, Kanagawa Ishikawashima-Harima Heavy Industries, Ltd. Machinery and Plant Development Center F term (reference) 4B029 AA02 BB01 CC02 CC03 CC13 DA06 DB11 DF09 DG06 4D024 AA04 AB06 BA17 BB03 BC01 CA01 DB03 DB08 DB15 4D037 AA11 AB06 BA03 CA01 CA07 4D040 BB42 BB82 DD01 DD31

Claims (4)

[Claims] 1. A high-concentration oil-containing wastewater is subjected to pressure flotation to remove most of the oil content from the wastewater, and the treated water is passed through a bioreactor filled with an oil adsorbent, and the oil adsorbent is added to the oil adsorbent. A method for treating oil-containing wastewater, comprising adsorbing oil and decomposing the adsorbed oil with petroleum-degrading bacteria. 2. The oil-impregnated wastewater treatment method according to claim 1, wherein a high-concentration oil-impregnated wastewater and pressurized air are mixed in a pressurized tank and then subjected to a pressurized floating treatment. 3. A pressurized flotation tank for levitation and separation of oil in high-concentration oil-containing wastewater with pressurized air, and treated water in the pressurized flotation tank are continuously introduced and filled with an oil adsorbent, An oil-containing wastewater treatment apparatus, comprising: a bioreactor for decomposing oil adsorbed on the petroleum adsorbent with petroleum-degrading bacteria. 4. The oil-impregnated wastewater treatment apparatus according to claim 3, wherein a pressurized tank for premixing the oil-impregnated wastewater and pressurized air is connected to the pressurized floating treatment tank.