JPH08132020A - Treatment of waste water containing oil component - Google Patents

Abstract

PURPOSE: To finally separate into dehydrated sludge and filtrate when a treating agent contg. a coagulant and dust not contg. oil component are added to waste water contg. oil component and the mixture is forcibly fed into a pressurizing tank together with compressed air by mixing floating scum and settled sludge to filter the mixture. CONSTITUTION: Dust 3 not contg. oil component is added to primarily treated waste water 2 which a primary treating agent is added to waste water contg. oil component to form, and the waste water 2 is forcibly fed to a pressuring tank 4 together with compressed air 1. While feeding of the primarily treated waste water into an inner cylinder 11 of a thickener 9 through a pressure adjusting valve 7, a coagulant is added as a secondary treating agent 8 to form floating scum. The floating scum is delivered to a slurry tank 15 through a scum tank 14 from a scum discharge port 12. On the other hand, the other precipitated dust particles are made to precipitate as precipitated sludge to a slurry tank 15. In the slurry tank 15, the floating scum and the precipitated sludge are mixed, and also the mixture is delivered to a filter press 15 and filtered to separate it into dehydrated sludge 17 and filtrate 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating industrial wastewater including ironmaking wastewater, particularly wastewater containing oil.

[0002]

2. Description of the Related Art Conventionally, waste water is generally treated by injecting chemicals such as a sulfuric acid band, a neutralizing agent and a polymer coagulant into the waste water in a reaction tank to agglomerate the dust particles present in the waste water to form flocs. Then, sedimentation was promoted in a thickener to collect, and this was referred to as recovered sludge, which was filtered by a filter press or the like to separate dehydrated sludge and filtrate.

Regarding the treatment of oil content in the filtrate,
A gravity type oil-water separator was used to separate oil-water by the difference in specific gravity of oil and water.

[0004]

In the conventional so-called sedimentation type thickener as a coagulation-sedimentation apparatus, the oil content in the waste water causes a floating scum that is difficult to settle, and dust particles that precipitate, that is, sedimentation sludge. Since the precipitation is inhibited, there is a problem that the collection of the sedimentation sludge becomes insufficient and the dust concentration in the wastewater treatment system increases.

When the oil in the wastewater floats up along with the floating scum, the oil remains in the thickener supernatant, and the oil gradually accumulates in the wastewater treatment system to raise the oil concentration. It was

Further, when the settled sludge is filtered by a filter press, the accumulated oil content adheres to the filter material and deteriorates the filtering function, and the oil content is mixed in the filtrate after dehydration. It is necessary to carry out the treatment, and there is a problem in that oil and water are separated by the gravity type oil and water separating device and the like, and it takes time and labor for pumping, handling, oil tank management and transportation management of the separated oil.

In order to solve these problems, the present invention adds a treatment agent containing oil-free dust and a flocculant to wastewater containing oil and a process in which dust particles form a floc-like scum in a thickener. By adopting a known pressure dissolution method, instead of floating scum, the floating scum is forcibly promoted to be formed, the oil in the waste water is adsorbed to the floating scum and the dust particles that do not float are precipitated. It is intended to filter the same floating scum together with the settling sludge to be separated into a dehydrated sludge containing oil and a filtrate with reduced oil, and further to obtain an appropriate filtration state during the above filtration. The purpose is to set a target value of the ratio of dust / oil content in the waste water to be filtered, and to use the step of controlling the addition amount of the oil-free dust.

[0008]

In order to achieve the above object, in the present invention, a wastewater containing oil is added with a primary treatment agent and dust containing no oil, and the mixture is pressed into a pressure tank together with compressed air. A coagulant is added as a secondary treatment agent in the middle of supplying the treated primary treated wastewater from the same tank to the inner cylinder of the thickener via the pressure control valve, and the treated wastewater is treated by the air bubbles generated by depressurization in the inner cylinder. When the dust particles intervening in the air form a floating scum, most of the particles trap the oil contained in the waste water as an adsorbent and form a floating scum that floats up with the bubbles, and the floating scum is slurried from the scum outlet. Sending to the tank, dust particles that settle in addition to the floating scum, that is, settling sludge, are sent from the bottom of the thickener to the slurry tank, where the floating scum and the settling sludge are sent. Mixing a slurry and without, filtered and pumped to the filter press, and the separating into a dewatered sludge and filtrate.

[0009] Further, when adding oil-free dust to oil-containing wastewater, it is necessary to make the filtration separation performance of the dehydrated sludge and the filtrate by a filter press and the oil recovery rate to the dehydrated sludge appropriate. For the set target value of the ratio of dust and oil in the wastewater, a process for controlling the amount of dust that does not contain oil will be used together.

[0010]

By the above means, the primary treatment agent is added in advance,
Both free oil and emulsified oil of oil can be processed, and compressed air is pressed into a pressure tank together with wastewater containing oil containing dust that does not contain oil, and the same tank as in the known pressure dissolution method. When the treated wastewater containing dissolved compressed air in the tank is supplied from the same tank to the inner cylinder in the middle stage of the thickener, the pressure is reduced via a pressure control valve and a coagulant is added as a secondary treatment agent. When dust particles intervening in the treated wastewater form floating scum due to air bubbles generated when depressurizing to the atmospheric pressure in the inner cylinder, most of the dust particles trap free oil in the wastewater in an adsorbed state. As a floating scum that floats along with the air bubbles, and therefore the oil content in the drainage is reduced, and the floating scum is discharged from the scum outlet and sent to the slurry tank, and the dust particles that settle without forming the floating scum are settled. Since there is almost no floating scum that hinders the sedimentation, sedimentation sludge is easily settled to the bottom of the thickener, and the sludge is sent to the slurry tank. In the slurry tank, the floating scum and the sedimentation sludge are mixed to form a slurry. It is sent by pressure to a press and filtered to separate the dehydrated sludge in which the oil content in the wastewater is adsorbed and the filtrate in which the free oil content in the wastewater is reduced.

When dust containing no oil is added to the wastewater containing oil, the dust containing no oil adsorbs the oil contained in the wastewater, and when the amount of dust containing no oil is controlled, The amount of oil to be adsorbed will be controlled, and the dust that has adsorbed oil will be collected as floating scum and sedimentation sludge, and sent under pressure to a filter press for filtration.
In the process of this filtration, the sludge layer to be filtered itself functions as a filter medium and is separated into dewatered sludge in which the oil content in the wastewater is adsorbed and adsorbed and the filtrate in which the oil content in the wastewater is reduced. The dust / oil content ratio is set to an appropriate control target value, and the amount of dust that does not contain oil content is controlled with respect to this target value, so the filtration separation performance of the filter press and the oil content contained in the dehydrated sludge are controlled. The recovery rate of is properly controlled.

[0012]

[Example] To the primary treatment wastewater 2 in which the primary treatment agent was added to the wastewater containing oil, the dust 3 containing no oil was added, and the primary treatment wastewater pressed into the pressure tank 4 together with the compressed air 1 was treated. , A coagulant is added as a secondary treatment agent 8 during the middle of supplying the thickener 9 from the same tank to the inner cylinder 11 of the thickener 9 through the pressure control valve 7, and bubbles are generated in the inner cylinder during depressurization in the treated wastewater. When the dust particles intervening in the air form a floating scum, most of the dust particles adsorb the oil content in the drainage and form a floating scum that floats along with the bubbles, and the floating scum is discharged from the scum outlet 12. Then, it is sent to the slurry tank 15 via the scum tank 14, and other dust particles of the floating scum that precipitate are settled as sedimentation sludge 13 at the bottom of the thickener, and the sludge is sent to the slurry tank 15, Oite, mixing the floating scum and sediment sludge was filtered and pumped to filter presses 16 forms a slurry with, have decided to separate the dewatered sludge 17 and filtrate 18.

When the dust 3 containing no oil is added to the wastewater containing oil, the filter separation performance of the dehydrated sludge 17 and the filtrate 18 by the filter press 16 and the dehydrated sludge 1
The process of controlling the addition amount of the dust is also used for the target value of the ratio of dust and oil in the wastewater, which is set so that the oil recovery rate to 7 is appropriate.

[0014]

Since the present invention is configured as described above, it has the following effects.

In the conventional so-called sedimentation type thickener as a coagulation-sedimentation apparatus, the oil content in the waste water causes a floating scum that is difficult to settle, so that the settling of dust particles that settle is hindered and the settling dust particles are settled. That is, although the collection of sedimentation sludge became insufficient and the dust concentration in the wastewater treatment equipment system increased, in the present invention, the primary treatment agent and the dust not containing oil were added to the wastewater containing oil. It is not possible to process difficult oil or emulsified oil in treated water. By pressure dissolution method, the primary treatment wastewater is pressed into the pressure tank together with compressed air, and the air is contained in the dissolved state. A flocculant is added as a secondary treatment agent in the middle of supplying to the inner cylinder, and bubbles generated when the pressure is reduced to atmospheric pressure in the inner cylinder promotes the formation of the floating scum, and the The oil content in the waste water is adsorbed, thus reducing the oil content in the waste water and the floating scum, and other dust particles that settle in the floating scum settle as sedimentation sludge at the bottom of the thickener, and the floating scum and the sedimentation sludge that adsorbed the oil content. It is possible to collect and dehydrate and to a filter press for filtration to separate the dehydrated sludge in which oil is adsorbed and the filtrate in which oil is reduced.

Therefore, by removing the dehydrated sludge and the filtrate out of the waste water treatment equipment system by this method and treating them respectively, it is possible to prevent dust concentration and oil content accumulation in the system.

Further, in the prior art, since oil remains in the filtrate after dehydration, oil and water separation, oil extraction, oil tank management, and transportation management are required for the oil treatment of the same liquid, but in the present invention, , By promoting the formation of the floating scum as described above, the oil content in the drainage is adsorbed to the scum, thus reducing the oil content in the drainage and recovering the floating scum and the sedimentation sludge that adsorbed the oil content. Since it can be separated into dehydrated sludge that has adsorbed oil content and filtrate that has reduced oil content by pumping to a filter press and filtering, dehydrated sludge is taken out of the waste water treatment equipment system by this method and incinerated, Can be processable outside the system.

When the oil-free dust is added to the oil-free wastewater, the oil-free dust adsorbs the oil content in the wastewater, and the addition amount of the oil-free dust is controlled to control the amount of the oil-free dust. The amount of oil adsorbed will be controlled, and the dust that has adsorbed oil will be collected as floating scum and settling sludge, pressure-fed to a filter press and filtered,
In the process of this filtration, the sludge layer to be filtered itself functions as a filter medium and is separated into dewatered sludge in which the oil content in the wastewater is adsorbed and adsorbed and the filtrate in which the oil content in the wastewater is reduced. The dust / oil content ratio is set to an appropriate control target value, and the amount of dust that does not contain oil content is controlled with respect to this target value, so the filtration separation performance of the filter press and the oil content contained in the dehydrated sludge are controlled. Therefore, the recovery rate of the filter is appropriately controlled, and thus the filter separation performance of the filter press is improved, and the replacement cost and labor of the filter material or the filter cloth are reduced,
Oil recovery is stable and related processes can be operated stably.

Incidentally, the dehydrated sludge is treated by incineration,
After burning the oil content, the non-combustible portion can be recycled as oil-free dust by adding the oil-free dust to the primary treatment wastewater.

As mentioned above, the wastewater containing oil is added with a treatment agent containing dust containing no oil and a coagulant, and at the same time the formation of floating scum is forcibly promoted by the pressure dissolution method in the thickener. The purpose is to capture the oil content in the waste water in an adsorbed state, and to separate the dewatered sludge containing the oil content by filtering the floating scum together with the sedimentation sludge that precipitates the dust particles that do not float, and the filtrate with reduced oil content, and During the filtration, a step of setting a target value of the ratio of dust / oil content in the wastewater to be filtered in order to obtain an appropriate filtration state and controlling the addition amount of the dust not containing the oil content is also used. You can reach the goal.

[Brief description of drawings]

FIG. 1 is a process chart showing an embodiment of the present invention.

[Explanation of symbols]

 1 Compressed Air 2 Primary Treatment Wastewater 3 Dust Not Containing Oil 4 Pressure Tank 7 Pressure Control Valve 8 Secondary Treatment Agent 9 Thickener 10 Supply Pipe 11 Inner Cylinder 12 Scum Discharge Port 13 Settling Sludge 14 Scum Tank 15 Slurry Tank 16 Filter Press 17 Dewatered sludge 18 Filtrate

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Masaaki Segawa 2-2-14 Yamamoto-cho, Yao-shi, Osaka (72) Inventor Kazuo Sasakawa 2-12-1, Koriyama, Ibaraki-shi, Osaka

Claims (2)

[Claims] 1. A primary treatment agent and dust containing no oil are added to waste water containing oil, and the mixture is pressed into a pressurized tank together with compressed air, and then the same is passed from the tank to the inner cylinder of the thickener through a pressure control valve. When a coagulant is added as a secondary treatment agent during the supply, and dust particles present in the treated wastewater form floating scum due to air bubbles generated when decompressing the inner cylinder, a large amount of dust particles is generated. The part captures the oil contained in the drainage in an adsorbed form to form a floating scum that floats with the bubbles, discharges the floating scum from the scum outlet and sends it to the slurry tank, and other dust particles that settle on the floating scum are removed. The sedimentation sludge settles at the bottom of the thickener, and the sludge is sent to the slurry tank. In the same slurry tank, the floating scum and the sedimentation sludge are mixed to form a slurry, and the slurry is pressed to the filter press. A method for treating wastewater containing oil, which comprises sending and filtering, and separating into dehydrated sludge and filtrate 2. When the dust containing no oil is added to the wastewater containing oil, the performance of filtering and separating the dehydrated sludge and the filtrate by the filter press and the recovery rate of the oil to the dehydrated sludge are adjusted appropriately. A method for treating wastewater containing oil, which includes a step of controlling the amount of dust added to the set target value of the ratio of dust and oil in the wastewater.