KR20060056447A - Modified starch wastewater treatment system - Google Patents

Abstract

The present invention relates to a modified starch wastewater treatment method, and an object thereof is to provide a pretreatment method capable of economically removing hardly decomposable substances contained in modified starch wastewater and a method of significantly reducing the neutralizing agent to reduce operating costs. have.

The composition of the present invention is a modified starch wastewater in a method for treating modified starch wastewater, wherein the modified starch wastewater, which has undergone a pretreatment process consisting of modified starch wastewater → water collection tank → primary aeration tank → first settling tank, is combined with the starch sugar wastewater additionally supplied from the comprehensive collection tank. After the acid fermentation tank → anaerobic digestion tank → secondary aeration tank → secondary sedimentation tank → discharge, it has a modified starch wastewater treatment process, in which the appropriate dilution of the modified starch wastewater and removal of residual starch particles (SS) and glacial acetic acid Part of the acid fermentation wastewater of the acid fermentation tank or the excess anaerobic sludge of the anaerobic digestion tank is returned to the tank, and the settling sludge of the first settling tank and the settling of the secondary settling tank are continuously maintained in the first aeration tank to maintain a constant concentration of activated sludge. All sludge was returned to the system, so that the adsorption and decomposition of aqueous modified starch were simultaneously performed. It is thus characterized by a process in which the weakly acidic modified starch wastewater is weakly alkaline or neutral.

Collection tank, aeration tank, sedimentation tank, acid fermentation tank, anaerobic digestion tank

Description

Modified starch wastewater treatment system             

1 is a wastewater treatment process diagram of the present invention,

Figure 2 is a process chart of modified starch wastewater using conventional anaerobic + activated sludge,

Figure 3 is a process chart of the modified starch wastewater using the conventional activated sludge.

The present invention relates to a method for treating modified starch wastewater, and more particularly, to a method for treating wastewater generated when manufacturing modified starch at a starch sugar manufacturing plant.

Modified starch is a starch that is modified by physical, chemical, and enzymatic treatment of starch for the purpose of use in the food, paper, and textile industries by using the polymer properties of starch. Properties are imparted, and there are acid processed starch, oxide starch, induction starch and the like depending on the processing method.

In particular, wastewater generated during the production of chemically modified starch is produced in the process of forcibly chemically oxidizing starch by adding oxidizing agent (NaOCl or H ₂ O ₂ ) to starch such as corn and potato.

In this regard, the wastewater contains oxidant residue, high salinity, and high concentration of water-soluble high molecular materials which may interfere with the growth of microorganisms.

Conventional treatment methods for treating the wastewater include anaerobic treatment and aerobic treatment.

Figure 2 shows a conventional process for the treatment of modified starch using anaerobic + activated sludge, in this case anaerobic digestion tank after hydrolysis and acid fermentation in the acid fermentation tank wastewater mixed with modified starch wastewater and starch sugar synthesis wastewater ( Anaerobic) is processed by inflow.

Specifically, the modified starch wastewater is collected in a collection tank, and then discharged through a comprehensive collection tank, an acid fermentation tank, an anaerobic digestion tank, a flocculation tank, a flotation tank, an aeration tank, and a settling tank. In general, the sump is configured to supply starch sugar wastewater.

3 is a process chart of modified starch using conventional activated sludge. In the case of such aerobic treatment, the modified starch wastewater is excessively diluted with water or low concentration wastewater (starch sugar wastewater), and then treated with aeration tank activated sludge. .

Specifically, the modified starch wastewater is collected in the sump tank and then discharged through the sump tank, the aeration tank, and the sedimentation tank, which is configured to supply a part of the effluent and the total wastewater per starch.

However, the above processing method has the following problems.

In the case of anaerobic treatment, since the substance to be treated is a high concentration of water-soluble high molecular substance and contains a high concentration of salts with chemicals, it takes a long time to hydrolyze. The disadvantage is that it adversely affects the growth of methane bacteria.

In the case of aerobic treatment, denatured starch is agglomerated (gelled) and precipitated together with activated sludge due to the action of aerobic microorganisms, which makes it difficult to maintain a constant concentration of activated sludge in the tank. There is a disadvantage in that the flocculation process and the sludge is frequently injured in the sedimentation basin, attached to a scraper or a pipe wall, and thus the sludge is difficult to transport.

An object of the present invention for solving the above problems is to reduce the operating cost by drastically reducing the pretreatment method and the neutralizing agent that can economically remove the hardly decomposable substances contained in the modified starch wastewater which is difficult to process in the general method To provide a way to do this.

The present invention to achieve the object as described above and to perform the problem for eliminating the conventional defects in the treatment method of modified starch wastewater, the modified starch wastewater → collecting tank → primary aeration tank → the first precipitating process consisting of the first settling tank The modified starch wastewater is combined with the starch sugar wastewater additionally supplied from the general water collection tank, followed by acid fermentation tank → anaerobic digestion tank → secondary aeration tank → secondary sedimentation tank → discharge. In order to properly dilute the starch wastewater and remove residual starch particles (SS) and glacial acetic acid, the acid fermentation wastewater of the acid fermentation tank or a part of surplus anaerobic sludge of the anaerobic digestion tank is returned, and the primary aeration tank has a constant concentration of activated sludge. Part of the settling sludge of the first settling tank and the total amount of settling sludge of the second settling tank are returned so that it can be maintained continuously. As it characterized by the adsorption and decomposition of the water-soluble modified starch which process to occur at the same time.

Hereinafter, the configuration and the operation of the embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a flow chart of the wastewater treatment of the present invention, in which the whole process is carried out in the order of denatured starch wastewater → collection tank → primary aeration tank → primary sedimentation tank → comprehensive collection tank → acid fermentation tank → anaerobic digestion tank → secondary aeration tank → secondary sedimentation tank → discharge It has a starch wastewater treatment process, wherein the collection tank is configured to return part of the acid fermentation wastewater of the acid fermentation tank or surplus anaerobic sludge of the anaerobic digestion tank, and the settling sludge of the first settling tank and the sedimentation of the secondary settling tank in the first aeration tank. All sludge was returned, and the comprehensive sump was fed and combined.

Hereinafter, each step will be described in detail.

1. Sump stage

Denatured starch wastewater is a high concentration wastewater (CODcr 8,000 ~ 20,000 mg / L) of weak acid (pH 4-5), and the wastewater is collected first in the sump to equalize the flow rate and water quality due to the large load fluctuation according to the discharge time. .

In addition, by maintaining a place under anaerobic conditions, a certain amount of external surplus anaerobic sludge (supplied from the anaerobic digester shown in FIG. 1) or acid fermentation wastewater (supplied from the acid fermentation tank shown in FIG. 1) is added to promote hydrolysis and denatured starch wastewater. Allow dilution to concentration.

The input amount of the acid fermentation wastewater and the appropriate concentration thereof are not uniform because the generated flow rate and water quality are different for each plant treating each wastewater treatment. Therefore, the input amount may be adjusted according to the required purpose according to the flow rate generated.

2. First Abandonment Stage

The modified starch sump effluent is continuously introduced into a primary aeration tank with suspended microorganisms or stationary phase microorganisms and aeration facilities. At the same time, surplus activated sludge (primary and secondary sedimentation sludge sludge sludge) is continuously introduced into a certain amount (some of the sedimentation sludge in the primary sedimentation tank and all of the sedimentation sludge in the secondary sedimentation tank).

It is always possible to maintain a high concentration of activated sludge in the aeration tank due to the activated sludge outside the system and the self-proliferating activated sludge.

Its operating conditions are similar to those of general active sludge. However, under normal operating conditions, the pH of the primary aeration tank is rapidly increased in a few hours due to biological action, thereby increasing to a maximum pH of 9.5 or neutral. This rate of increase in pH is proportional to the amount of air injected.

This has the effect of neutralizing the pH when mixed with starch sugar wastewater (pH: 3-4) supplied from outside in the raw water general water collection tank in the future, it is an existing method of alkaline agents (NaOH, Ca (OH)) _2, other) can greatly reduce the advantage.

The input amount of the sedimentation sludge of the primary sedimentation tank and the sedimentation sludge of the secondary sedimentation tank is not uniform because the generated flow rate and water quality are different for each wastewater treatment plant. Therefore, the input amount may be adjusted according to the required purpose according to the flow rate generated.

3. First precipitation settling stage (or floating tank)

In this step, the wastewater treated in the first aeration tank is introduced into the main tank (primary sedimentation tank) to separate activated sludge and wastewater by specific gravity. The sedimented sludge is withdrawn to the pump from the bottom of the settling tank, a portion of the withdrawn sludge is recycled to the primary aeration tank, the remainder is transferred to the thickening tank and finally dewatered by the dehydrator. This process can also be replaced by flotation tanks.

4. General catchment stage

The starch sugar manufacturing plant generates a small amount of high-density modified starch wastewater and a large amount of low-density (CODcr 3,000 mg / L) starch sugar wastewater.In this step, the pretreated modified starch wastewater and the starch sugar composite waste water are mixed with each other for further treatment. Is a process that is homogenized.

Each of these flow rates and water quality is not uniform because each plant has different types and outputs.

5. Acid Fermentation

This step is to hydrolyze the polymer organic matter as a hybrid microorganism (microorganisms that can grow without oxygen if oxygen is available) before introducing the mixed wastewater into the anaerobic digester. Acid fermentation with acid to produce organic acid (Acetic acid, propionic acid, etc.).

 High Molecular Organics ---------------------> Organic Acids

                    Organic Acid Fermentation

At this time, the optimum reaction pH should be around 6, but in the conventional method, the pH of the starch sugar wastewater (3-4) is low, and the pH is further lowered due to the generation of organic acid. To this end, it is common to continuously raise a large amount of alkaline medication to raise the pH. However, in the present invention, since the modified starch wastewater is preliminarily changed into weak alkaline, the amount of alkaline agent required for neutralization in the subsequent process can be greatly reduced.

In other words, in order to satisfy the optimum reaction pH condition of the acid fermentation tank step 6, the modified starch wastewater pretreated by biological reaction in the first aeration tank was biologically reacted with primary precipitator (or flotation tank), which is a subsequent process. Inflow to the sump can be raised, or in some cases by bypassing the comprehensive sump directly into the acid fermentation tank (in dashed line portion of Figure 1) to increase the pH.

6. Anaerobic Digestion Stage

In this step, the organic acid generated in the acid fermentation tank, which is an acidification tank, is gasified with methane bacteria (Bio-gas).

Organic acid --------------------------------> CO ₂ , CH ₄

                           Methane fermentation

Part of the excess anaerobic sludge produced at this stage was returned to the modified starch collection tank.

7. 2nd Aeration Stage

Contaminants still remain in the anaerobic digester treated water and need to be treated within environmental standards. This secondary aeration tank is a process for treating residual pollutants within the environmental standard value using aerobic microorganisms.

8. Secondary Precipitator Step

The function of this step is the same as that of the primary settler. The mixed liquor of the secondary aeration tank is separated into waste water and sludge, and the supernatant is finally discharged, and the sedimented sludge is separated separately. In the present invention, all of the settled sludge is transferred to the first aeration tank by using a pump to be used again.

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by any person having ordinary skill in the art without departing from the gist of the present invention claimed in the claims. Of course, such changes will fall within the scope of the claims.

The present invention as described above is a biological adsorption removal technology that can remove the water-soluble high-molecular material difficult to remove in a general way economically and wastewater by a biological method at a low cost biological method instead of raising the pH of the waste water using an alkaline agent previously Since it was developed a method of voluntarily raising the pH of the invention, it is a useful invention that is very helpful for the design and operation of an economic wastewater treatment plant and is an invention that is expected to be greatly used in the industry.

Claims (6)

In the treatment method of modified starch wastewater, In order to equalize the flow rate and water quality of the high density modified starch wastewater of the supplied weak acid, the wastewater is first collected and maintained under anaerobic conditions to promote hydrolysis and to increase the concentration of modified starch wastewater by adding external surplus anaerobic sludge or acid fermentation wastewater. A dilution sump step; The modified starch wastewater effluent passed through the sump is continuously supplied, and a surplus of activated sludge outside the system is continuously introduced to maintain a high concentration of activated sludge due to the active sludge and the self-proliferating activated sludge outside the system, thereby making the pH of the wastewater alkaline. A first aeration tank step of making; A first precipitation settling step of receiving activated wastewater treated in the first aeration tank and separating activated sludge and wastewater by specific gravity; A comprehensive collection tank step of mixing a small amount of alkaline high concentration modified starch wastewater that has been passed through the above step and a large amount of low-concentration starch sugar comprehensive wastewater added thereto to adjust to a uniform pH; An acid fermentation tank step of generating organic acids (Acetic acid, propionic acid, etc.) by hydrolysis and acid fermentation of the polymer organic matter in the mixed wastewater homogenized in the comprehensive collection tank as a communicable microorganism; An anaerobic digestion tank step in which the organic acid in the wastewater generated in the acid fermentation tank, which is an acidification tank, is gasified by methane bacteria; A second aeration stage for treating contaminants remaining in the wastewater within the environmental standard values using the aerobic microorganisms after the step; After the above step, the mixed liquor of the secondary aeration tank is separated into wastewater and sludge, and the supernatant is finally discharged, and the sedimented sludge is composed of a secondary sedimentation tank stage to separate, so that the modified starch wastewater is treated. The acid fermentation tank or anaerobic digestion tank returns the portion of the acid fermentation wastewater of the acid fermentation tank or excess anaerobic sludge of the acid fermentation tank to the sump for proper dilution of the modified starch wastewater of the sump and removal of residual starch particles (SS) and glacial acetic acid. Composed, The primary aeration tank is configured to return part of the sedimentation sludge of the primary sedimentation tank and the total amount of the sedimentation sludge of the secondary sedimentation tank so that a constant concentration of activated sludge is continuously maintained, thereby adsorbing and decomposing the aqueous modified starch at the same time. Modified starch wastewater treatment method. The method of claim 1, The modified starch wastewater supplied to the sump is a small amount of high concentration wastewater (CODcr 8,000 ~ 20,000 mg / L) having a pH of 4-5, and the starch sugar wastewater supplied to the comprehensive sump is a large amount of low concentration having a pH of 3-4 ( CODcr 3,000 mg / L) modified starch wastewater treatment method characterized in that. The method of claim 1, The sludge sedimented in the first settling tank stage is withdrawn from the lower part of the settling tank to the pump, and a part of the withdrawn sludge is recycled to the primary aeration tank and the rest is transferred to the concentration tank so that it is finally dehydrated by a dehydrator to be generated in a wastewater treatment plant. The modified starch wastewater treatment method characterized in that all the activated sludge is discharged through the primary sedimentation cell after the adsorption or decomposition of the water-soluble starch through the primary aeration tank. The method of claim 1, The first aeration tank is configured to rise to a maximum pH of 9.5 to neutral in a few hours by the action of pH (biological suspension, fixed-phase microorganisms), and to control the amount of air injecting the rising rate of the pH denatured Starch wastewater treatment method. The method of claim 1, In order to satisfy the optimum reaction pH condition of the acid fermentation tank step 6, the modified starch wastewater pretreated by biological reaction in the first aeration tank was subjected to the first settling tank (or flotation tank) and the comprehensive collection tank as a subsequent process. The modified starch wastewater treatment method characterized by increasing the pH by flowing into the acid fermentation tank. The method according to any one of claims 1 to 5, In order to satisfy the optimum reaction pH condition of the acid fermentation tank step 6, the modified starch wastewater pretreated by biological reaction in the first aeration tank through the biological reaction was subjected to the first sedimentation tank (or flotation tank) as a subsequent process. By-pass denatured starch wastewater treatment method characterized in that to increase the pH by flowing into the acid fermentation tank.

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