JPH09192692A - Treatment of oil and fat-containing waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conveniently and efficiently separate waste water to a purified water and a sludge by mixing an inorg. flocculating agent to the waste water to form a flock after adsorbing oil and fat by mixing an inorg. fat adsorbent to waste water and mixing a high molecular flocculating agent to waste water to form a desired flock after adjusting pH. SOLUTION: At the time of treating oil and fat-containing waste water 1 such as kitchen waste water, the waste water is stored in an oil and fat adsorbent mixing tank 3 after removing a relatively large sludge suspended in the waste water 1 with a removing screen 2. After sufficiently adsorbing the oil and fat to an inorg. oil and fat adsorbent 3A such as diatomaceous earth and bentnite at here, the flock is formed by using an inorg. flocculating agent. Then the waste water 1 in which the flock is formed is transferred into an adjusting tank 5 and the pH is adjusted to increase a sticking property of the flock at the time of sludge separation and to increase a dehydrating ability by releasing a moisture content in a separated sludge. Then a high molecular flocculating agent 6A is added at a flocculation accelerating tank 6 to separate the sludge and the purified water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention can easily and efficiently separate wastewater having a high concentration of fats and oils such as kitchen wastewater and food processing wastewater into purified water and sludge, and also easily separate sludge. The present invention relates to a method for treating oil / fat-containing wastewater that can be formed into dry sludge.

[0002]

2. Description of the Related Art Wastewater having a high concentration of fats and oils such as kitchen wastewater and food processing wastewater has been conventionally stored in a storage tank and then treated with acid or alkali to obtain a required pH.
After adjusting the value, transfer it to the flocculation tank, mix and stir the required flocculant to form flocs of oils and contaminants, and then float the flocs by supersaturated air in the pressure flotation tank to obtain purified water. The so-called dehydrated cake in which purified water is discharged into a river and the floated and separated, and the water content is removed as much as possible by the centrifugal separation method, filter press method, belt press method, etc. As a result, they are disposed of after reducing the disposal cost.

[0003] However, in addition to pollutants, not only water-insoluble fats and oils such as animal fats and oils but also a part of them such as vegetable fats and fats which are soluble in water are contained in kitchen wastewater and food processing wastewater. Since it is contained in a large amount, extremely high technology and operability are required over the adjustment of pH value for floc formation, the mixing amount of a flocculant, the stirring conditions, and the airation during pressure floating. For this reason, the separation of flocs and purified water becomes insufficient again, resulting in deterioration of treated water quality.

Further, sludge containing a large amount of oil and fat is
In a short time, the inside becomes anaerobic to generate hydrogen sulfide, etc., which not only gives offensive odors but also may impair the health of workers, and also causes corrosion of wastewater treatment equipment. In addition, dehydration treatment to reduce sludge disposal costs. Also in the case of carrying out the above, since the adhesion of the oil and fat causes the adhesion in the dehydrator and the clogging of the dehydration filter, the dehydration treatment is considerably reduced.

For this reason, it has been desired to treat the sludge containing oil and fat with a thermal means instead of the conventional mechanical means. By the way, as a method of dehydrating sludge by thermal means, it is possible to dehydrate the sludge by dielectric heating while transporting the sludge on a dehydration conveyor in the dehydration pipe.
Japanese Patent Application Laid-Open No. Hei 7-35323 discloses that the heated heat medium balls are mixed with sludge, the sludge is dried, and then the heat medium balls and the dried sludge are separated. Further, it is disclosed in Japanese Patent Application Laid-Open No. 7-136662 that the sludge is attached to the belt-shaped filter cloth of the conveyor device in which the belt-shaped filter cloth rotates and is passed through the heating device while being carried out upward to be dehydrated and dried. ing.

However, in the invention of Japanese Patent Laid-Open No. 6-198300, the sludge generated by the wastewater treatment is supplied into the dehydration pipe body to heat and evaporate the water by high-frequency dielectric heating for dehydration. 85 to 9
Since 0% or more of water is contained, very high power is required to heat and evaporate and dehydrate these water, and in the case of sludge containing oil and fat, the boiling point of oil and fat is higher than that of water, and water is evaporated. At the same time, the oil and fat melted,
Post-processing is extremely troublesome.

Further, according to the invention of JP-A-7-35323, in the sludge having a high content of oil and fat, even if the water is evaporated in the heat medium ball, the oil and fat is melted and adheres to the heat medium ball, and the dry sludge and the heat medium are Separation from the ball becomes extremely difficult.

Further, in the invention of Japanese Patent Application Laid-Open No. 7-136662, the sludge containing the oil and fat separated from the purified water is attached to the band-shaped filter cloth by filtration, carried out upward and heated and dried. Not only does the oil and fat melt away and dry sludge cannot be formed, but there is a risk that the melted oil and fat will drip into the purified water that has been separated and purified.

[0009]

The present invention has been made in view of the above problems, and the present invention provides a simple and efficient purified water even for wastewater having a high oil and fat content such as kitchen wastewater and food processing wastewater. An object of the present invention is to provide a method for treating oil-and-fat-containing wastewater which can be separated into sludge and easily formed into dry sludge without melting the separated oil and fat.

[0010]

[Means for Solving the Problems] The technical means used by the present invention to solve the above-mentioned problems are the wastewater treatment such as kitchen wastewater or food processing wastewater containing at least 50 ppm of oil / fat separation concentration. 1m of the wastewater
³ to 10 to 1000 g of an inorganic fat and oil adsorbent selected from diatomaceous earth, bentonite, activated clay or shirasu
Mix and stir an appropriate amount of the above range to sufficiently adsorb the fat and oil, and then mix and stir an appropriate amount of the inorganic flocculant to form a floc on the inorganic fat and oil adsorbent on which contaminants and fats and oils are adsorbed. Let it form.

Then, after adjusting the pH value to a required value with an acid or alkali, an appropriate amount of the polymer flocculant is mixed and stirred to form a desired floc. Then, the wastewater in which the flocs are formed is divided into two tanks, a front tank and a rear tank, by a filter screen that is meshable to filter the flocs and that is rotatable above the outside of the tank. Allow the flocs formed in the front part of the tank to slowly flow in so that they do not collapse, and allow the waste water that has flowed into the front part of the tank to pass through a filter screen that is divided by the water level difference. By advancing into the rear tank, the flocs are filtered by a filter screen and carried out to the outside of the tank, the water content in the flocs is naturally released and separated into dehydrated sludge,
The present invention also relates to a method for treating oil-fat-containing waste water, in which purified water is separated into a rear tank by passing it through a filter screen.

[0012] In addition, in the present invention, further suitable technical means can be provided except when the fat-and-oil-containing wastewater contains a large amount of extraneous contaminants or has an abnormal pH value. After removing relatively large contaminants that are turbid in the oil / fat-containing wastewater by a mechanical means and mixing and stirring an appropriate amount of the inorganic oil / fat adsorbent in the range of 10 to 1000 g with respect to 1 m ³ of the wastewater, the polymer coagulant is added. It is also possible to mix and agitate an appropriate amount to form flocs, and then gently inject the wastewater on which the flocs are formed into the front tank of the separation tank to separate purified water and sludge. Issues are solved.

[0013]

The technical means of the present invention has the following actions.
That is, even if a large amount of fats and oils that are insoluble or soluble in wastewater are contained, it is possible to use porous diatomaceous earth, bentonite, activated clay or shirasu etc. The oil adsorbent selected is 1m of wastewater
^Since an appropriate amount within the range of 10 to 1000 g is mixed and agitated with respect to 3, the fats and oils contained in the kitchen wastewater and food processing wastewater are sufficiently adsorbed by the fats and oils adsorbent, and thus the inorganic coagulant or high Since the molecular aggregating agent is mixed in an appropriate amount and agitated, flocs having a high aggregating property and being substantially uniform are formed.

The wastewater on which the flocs are formed is divided into two tanks, a front tank and a rear tank, by a filter screen that is meshable to filter the flocs and that is rotatable above and outside the tank. In order to allow the formed flocs to slowly flow into the front tank of the divided separation tank so as not to collapse, the wastewater that has flowed into the front tank is filtered through the filter screen that divides according to the water level difference. As a result of advancing into the rear tank through the flow, the flocs in the wastewater are filtered on the filtering screen without being damaged and are swept out above the tank, so that the water content in the flocs is naturally released. Is separated as dewatered sludge and filtered through a filter screen to separate purified water into the rear tank.

[0015]

EXAMPLE An example of the present invention will be described below with reference to the drawings. FIG. 1 is a process flow chart of the present invention using an inorganic coagulant and pH adjustment. The oil and fat-containing wastewater 1 includes kitchen wastewater. Waste water with high oil and fat content, such as food processing waste water, which usually has a low oil and fat content concentration of about 50 to 100
Approximately 500 to 10 when the content concentration is high from ppm
It is as high as 00 ppm. In the treatment of the oil / fat-containing wastewater 1, relatively large contaminants turbid in the oil / fat-containing wastewater 1 are removed in advance by the coarse removal screen 2 and then in the oil / fat adsorbent mixing tank 3. Save.

Then, with respect to 1 m ³ of the oil / fat-containing wastewater 1 stored in the oil / fat adsorbent mixing tank 3, the oil / fat has a high adsorptivity and a large adsorption surface area, and is further dried by heating after being separated as sludge. In order to sufficiently adsorb the oil / fat contained in the inorganic oil / fat adsorbent 3A in view of reusability as a dry sludge or the like, the inorganic oil / fat adsorbent is appropriately mixed in an amount of 10 to 1000 g and stirred. Specific examples of 3A include diatomaceous earth, bentonite, activated clay and shirasu. The amount of the inorganic oil / fat adsorbent 3A mixed is at least 1 m of waste water in order to sufficiently adsorb the oil / fat content of 50 ppm.
10g or more is required for ³ and 1000g
This is because increasing the amount of sludge generated on the contrary exceeds. Inorganic oil adsorbent 3 for oil-containing wastewater 1
The specific mixing ratio of A varies slightly depending on the oil and fat content concentration and SS value, but the oil and fat content concentration is 310 ppm, S
1m for wastewater 1 containing fat and oil with S value of 330ppm
About 180 to 250 g is used for 3 pieces.

Thus, after the oil / fat of the oil / fat-containing wastewater 1 is adsorbed on the inorganic oil / fat adsorbent 3A, the wastewater is condensed into a coagulation tank 4
And the flocs are formed on the inorganic fat and oil adsorbent 3A or the like that adsorbs contaminants and fats and oils that are turbid in the fat and oil-containing wastewater 1. The formation of flocs in such a case is performed by adsorbing an turbid pollutant or an oil / fat component
Since it is for separating A into purified water, the inorganic flocculant 4A is used because it is necessary to reliably capture these contaminants and the like to form flocs. Examples include sulfuric acid bands and aluminum chloride. The mixing ratio of the inorganic coagulant 4A varies depending on the water quality of the oil / fat-containing wastewater 1.
For general wastewater such as kitchen wastewater, when using a sulfuric acid band with a concentration of 10%, approximately 250 per 1 m ^{3 of} oil-fat-containing wastewater
About 350 to 350 g may be used.

The oil-fat-containing wastewater 1 on which flocs are formed is transferred into the adjusting tank 5 for adjusting the pH value to the required value. Waste water 1 containing oil and fat in the adjusting tank 5
On the one hand, the pH value should be adjusted to comply with the discharge standard for separating and discharging purified water on the one hand, and enhancing the filterability of the flocs during sludge separation and naturally releasing the water content in the separated sludge. To increase the dewatering property and to separate purified water through the filter screen efficiently by filtering, thus enhancing the aggregating action by the polymer aggregating agent that grows to a floc of a required size. Acid or alkaline 5A mainly composed of caustic soda is used.

The oil-and-fat-containing wastewater 1 in which flocs are formed and adjusted to a required pH value is transferred to the flocculation promoting tank 6 in order to further grow the flocs and to efficiently separate sludge and purified water. To be done. In this coagulation accelerating tank 6, the polymer flocculant 6A is mixed in an appropriate amount and stirred in order to grow the flocs already formed by the inorganic flocculant 4A to a required size. Examples thereof include polyacrylamide type coagulant, sodium alginate, and chitosan. The mixing amount of the polymer flocculant 6A is determined by the mesh size of the filter screen 8 provided in the separation tank 7 used for separating the sludge and the purified water and the size of the flocs grown and formed. The size of the flock is preferably about 3 to 10
It is convenient to form it to about mm, and in the general oil-fat-containing wastewater 1, about 2 to 5 g is used for 1 m ³ .

As described above, the present invention is limited to the method of treating the oil / fat-containing wastewater 1 in a continuous multi-step manner over the oil / fat adsorbent mixing tank 3, the aggregation tank 4, the adjusting tank 5 and the aggregation promoting tank 6. However, a storage tank capable of adjusting the inflow amount of the oil-and-fat-containing wastewater 1 is provided, and in an appropriate treatment tank, the inorganic oil-and-fat adsorbent 4A is mixed and stirred, the inorganic flocculant 5A is mixed and stirred, and an acid or an alkali is used. The mixing and stirring of 5A and the mixing and stirring of 7A of the polymer flocculant may be sequentially processed in the same tank.

The fat-and-oil-containing wastewater 1 thus grown into the required flocs has a mesh structure capable of filtering the flocs grown into the required size as shown in FIG. 2 and above the outside of the tank. A separation tank 7 whose inside is divided into two tanks, a front tank 7A and a rear tank 7B, by a filter screen 8 which can be rotated to
Of the oil and fat-containing wastewater 1 that has flowed into the front tank 7A is filtered through the filter screen 8 due to the difference in water level. By advection to the rear tank 7B, the flocs are filtered on the filter screen 8 without collapsing, and the water content in the flocs is carried out by being carried out above the tank as the filter screen 8 rotates. Is also naturally discharged and separated as dewatered sludge, and the one that has passed through the filter screen 8 is separated as purified water in the rear tank 7B.

By the way, the general oil / fat-containing wastewater 1 such as kitchen wastewater and food processing wastewater is not restricted by the above treatment method because it does not have turbidity of extraneous contaminants or an extreme pH value. Without this, a simpler processing method can be adopted as shown in FIG. That is, a relatively large contaminant that is turbid in the oil-fat-containing wastewater 1 having an oil-fat content-concentration of 50 ppm or more is removed, and 1 to ³ m ^{3 of the} oil-fat-containing wastewater 1 contains 10 to 1000 of the inorganic oil / fat adsorbent 3A.
An appropriate amount within the range of g is mixed and stirred to sufficiently adsorb the oil and fat to the inorganic oil and fat adsorbent 3A, and then the polymer coagulant 6
A is mixed and stirred in an appropriate amount to directly form a floc of a required size, and thus the oil / fat-containing wastewater 1 in which the floc is formed is gently flown into the front tank 7A of the separation tank 7, Therefore, a treatment method for efficiently separating sludge and purified water can be adopted. Even in such a case, it is desired that the size of the flocs to be formed is about 3 to 10 mm, and the polymer flocculating agent 6A is directly formed, so that the mixing amount of the polymer flocculating agent 6A is a general oil and fat content. In the case of the contained wastewater 1, about 10 to 30 g may be used for 1 m3.

[0023]

Since the present invention uses the above-mentioned technical means, insoluble fats and soluble fats which are turbid in kitchen wastewater and food processing wastewater are 10 to 10 per 1m3 of the wastewater.
Since an appropriate amount of the inorganic oil / fat adsorbent having an adsorption surface area in the range of 00 g is mixed and stirred, these oil / fat components are sufficiently adsorbed by the inorganic oil / fat adsorbent, and the inorganic coagulant and the polymer coagulant are added. Alternatively, since the polymer flocculant alone forms flocs, it is possible to reliably form substantially uniform flocs of a required size with high cohesiveness with respect to not only the contaminants but also the inorganic fat and oil adsorbent in which fats and oils are adsorbed. ,
By allowing the flocs to flow into the front tank of the separation tank without collapsing and allowing the water to pass through the filter screen due to the difference in water level, the flocs can be filtered without being pressed onto the filter screen. Therefore, the water content in the flocs is easily released spontaneously by being carried out to the upper side of the tank by the rotation of the filtration screen, so that it is separated as dewatered sludge having a significantly lower water content than the conventional sludge. Moreover, the dewatered sludge can be easily separated from the filter screen and collected. Further, since the dehydrated sludge separated according to the present invention has a very low water content and the oil and fat content is also adsorbed by the inorganic oil and fat adsorbent, the heating amount is significantly reduced even when the dried sludge is formed by an appropriate heating means. The oil and fat do not melt even when heated, and can be reused easily. It can be said that this is a treatment method of oil-fat-containing wastewater, which has a very large number of characteristics, such as purified water being separated in the rear tank by passing it through a filter screen.

[Brief description of the drawings]

FIG. 1 is a process diagram of the present invention using an inorganic coagulant and pH adjustment.

FIG. 2 is a cross-sectional explanatory view of a separation tank.

FIG. 3 is a process chart of the present invention using a polymer flocculant.

[Explanation of symbols]

 1 Wastewater Containing Oils and Fats 2 Removal Screen 3 Oils and Oils Adsorbent Mixing Tank 3A Inorganic Oils and Oils Adsorbent 4 Coagulation Tank 4A Inorganic Coagulant 5 Adjustment Tank 5A Acid or Alkali 6 Aggregation Acceleration Tank 6A Polymer Coagulant 7 Separation Tank 7A Front Tank 7B Rear tank 8 Filtering screen

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C02F 1/58 C02F 1/58 B

Claims (2)

[Claims] 1. Waste water containing fats and oils in a concentration of at least 50 ppm or more is removed by a removal screen to remove relatively large contaminants that are turbid in the waste water, and 1 m ^{3 of the} waste water.
On the other hand, an inorganic oil / fat adsorbent selected from diatomaceous earth, bentonite, activated clay or shirasu is mixed in an appropriate amount within a range of 10 to 1000 g and stirred to allow the oil / fat content to be sufficiently adsorbed, and an appropriate amount of the inorganic coagulant. Mix and stir to form flocs on the inorganic oil and fat adsorbent that has adsorbed contaminants and oils and fats, and then acid or alkali to give the required pH.
After adjusting to the value, a suitable amount of the polymer flocculant is mixed and stirred to form a desired floc, and thus the floc is a mesh that allows the floc to be attached by filtration and is rotatable above the outside of the tank. The waste water on which flocs were formed was allowed to slowly flow into the front tank of the separation tank, which was divided into two tanks, the front tank and the rear tank, by the landing screen, and the water level difference in the front tank was As a result, the wastewater is filtered through a filter screen and admitted into the rear tank, whereby the flocs are filtered onto the filter screen and carried out to the outside of the tank, so that the water content in the flocs is naturally released. A method for treating oil-fat-containing wastewater, characterized in that purified water is separated into dehydrated sludge and filtered through a filter screen to separate purified water into the rear tank. 2. The amount of inorganic adsorbent is 10 per 1 m ^{3 of} waste water.
A method in which the waste water formed into flocs by mixing and stirring an appropriate amount of a polymer flocculant is gently flowed into the front tank of the separation tank after mixing and stirring an appropriate amount in the range of 1 to 1000 g. 1. The method for treating oil-and-fat-containing wastewater according to 1.