JPH03224689A - How to remove soluble COD - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is a COD treatment method used for further advanced treatment of soluble COD components in treated sewage water and industrial wastewater for pollution control purposes or for water reuse. Regarding one method of treatment, in more detail, coagulation and sedimentation, which are established for general wastewater treatment,
This is a COD treatment method that effectively utilizes the dehydration process.

[Conventional technology] (1) In the case of factory wastewater treatment Even in the same factory, various types of wastewater are generated depending on the manufacturing process, but when these are generally integrated, they can be treated using general treatment techniques such as biological treatment, coagulation and sedimentation, and dehydration. Wastewater is broadly divided into wastewater that can be treated and wastewater of a quality that cannot be treated using these general methods.

Among the wastewater that cannot be treated using general methods, high-molecular organic compounds and biorefractory organic substances (color components such as bile pigments and lignin, surfactants such as ABS, surface treatment agents, dyes,
Conventional methods for removing soluble COD components caused by water-soluble polymeric organic compounds such as PVA include activated carbon adsorption methods, oxidation methods using ozone, chlorine ions, potassium permanganate, etc.; The technology is rPPM 19
There are acidic flocculation and chemical oxidation methods published in the 1986 October issue.

All of these conventional methods require the installation of dedicated treatment equipment for soluble COD treatment, and require a large amount of chemicals to operate, resulting in high construction costs and treatment running costs. There is.

(2) In the case of advanced sewage treatment, secondary treatment of sewage water is treated by coagulation, sedimentation, sand filtration, etc.
Increasingly, the treated water is subjected to more advanced treatment using reverse osmosis membrane technology and reused for industrial purposes. In this case, soluble COD components caused by organic substances that are difficult to decompose are removed by a reverse osmosis membrane, but concentrated wastewater has a high concentration of soluble COD components, so in the case of the factory wastewater mentioned above, Similarly to the conventional method, it is necessary to install specialized equipment for treatment and then drain the water, which similarly raises the problem of high construction and running costs.

[Problems to be Solved by the Invention] The present invention solves the problems of this conventional method and makes effective use of existing treatment processes, thereby reducing construction costs, extremely low running costs, and achieving a high removal rate. The present invention provides a method for removing soluble COD components.

[Means for Solving the Problems] The present invention provides a treatment method for removing soluble COD components contained in raw water to be treated, in which existing or new coagulation, precipitation, Raw water to be treated containing soluble COD components is mixed into the sludge extracted during the dewatering process,
The raw water mixed sludge is separated into solid and liquid by dehydration, and the soluble C
This method obtains separated water from which OD components have been removed, and makes effective use of existing or newly installed coagulation, precipitation, and dehydration processes that have been commonly used in the past, without the need for special treatment equipment.
This is a method for inexpensively removing soluble COD components with a high removal rate.

[Function] In general, in wastewater treatment by coagulation and precipitation, a neutralizing agent is injected for wastewater containing metal ions such as iron or aluminum, such as acidic wastewater from factories, to coagulate it and remove organic substances like sewage. For materials containing a large amount of suspended solids, a flocculant (aluminum-based or iron-based) is injected to coagulate and form flocs. Therefore, in any of the above cases, the sludge that is separated and extracted in the sedimentation process contains acidic metal ion components (
Al1 and Fe) are included. Soluble COD of the present invention
The principle of action of component removal is that CO soluble in such sludge
Raw water to be treated containing component D is mixed, and in the process of dehydrating this raw water mixed sludge, soluble COD components are made to act on acidic metal ion components, and separated water from which soluble COD components have been removed is discharged as treated water. Alternatively, the separated water is remixed into untreated sewage or industrial wastewater, and the wastewater is treated through the coagulation and precipitation treatment steps.

An example in which the present invention is applied to factory wastewater treatment and advanced sewage treatment will be described below.

[Example 1] Figure 1 (A) is a treatment flow of an existing wastewater treatment facility in a certain metal processing factory, in which acidic factory wastewater 1 containing aluminum-based metal substances is treated using a general method. The wastewater is treated by coagulation and sedimentation methods before being discharged.

Figure 1 (B) shows the flow of biologically treating COD wastewater 15 containing surface treatment agents, dyes, etc. generated from another manufacturing process in the same factory, but this treated water contains soluble COD that cannot be treated. Contains ingredients.

The present invention is characterized by the soluble C discharged in the treatment flow of (B).
Treated water containing OD as soluble COD raw water 19 (A)
This is done by mixing it into the processing flow.

Factory wastewater 1 is primarily stored in a regulating tank 2 and sent to a chemical feeding tank 4 by a pump. The neutralizing agent 3 is injected into the chemical injection tank 4, mixed with a stirrer, and sent to the sedimentation tank 6 after a flocculation time has elapsed in the flocculation tank 5. The supernatant water in the settling tank 6 overflows, passes through a water receiving tank 7, and is discharged as treated wastewater 8 by a pump. On the other hand, the drawn sludge 9 drawn from the lower part of the settling tank 6 is sent to a sludge receiving tank 11 by a pump, and further sent to a dewatering device 12 by a pump.
3 and a dehydrated cake 14 are separated into solid and liquid. The separated water 13 is returned to the adjustment tank 2 by a pump and reprocessed. The dehydrated cake 14 is treated as industrial waste. Note that a vacuum dehydrator, a pressure dehydrator, a centrifugal dehydrator, etc. are used as the dehydrator.

COD wastewater 15 generated from another process is transferred to another tank 16.
It is temporarily stored in the tank, sent to a packing tank 17 for biological treatment using a pump, and sent to a settling tank 18 after being packed. A part of the sludge 29 discharged from the lower part of the settling tank 18 is dehydrated and treated as industrial waste, and the rest is returned to the adjustment tank 16 and reprocessed.

Since the supernatant water of the sedimentation tank 18 contains organic substances that cannot be completely biodegraded by biological treatment, it is treated as soluble COD raw water 19 in the sludge receiving tank 11 shown in the treatment flow in FIG. 1 (A).
The mixed sludge 10 is mixed into the drawn sludge 9 to form a mixed sludge 10. This mixed sludge 10 is sent by a pump to a dewatering device 12, where it is separated into solid and liquid, but in this process, the soluble COD component acts on the acidic metal ion component contained in the drawn sludge 9, It is removed and discharged together with the dehydrated cake 14.

The separated water 13 is either directly discharged as N waste water, or in order to further increase the removal rate of soluble COD, it is returned to the adjustment tank 2 by a pump and coagulated as shown in the existing treatment flow shown in FIG. 1(A).
It is reprocessed by precipitation and discharged as wastewater together with the treated wastewater 8.

Soluble CO measured experimentally in this Example 1
Table 1 shows the removal performance of D. Drawing sludge 9 in Figure 1 (A) treatment flow and soluble COD in Figure 1 (B) treatment flow
Experiment No. 001 to 3 on the water volume ratio of raw water 19
When the soluble COD component in the mixed sludge 10 is 300 ppm to 1.500 ppm, the soluble COD component remaining in the separated water 13 after dehydration treatment is 26,
The removal rate was reduced to lppm-79.2ppm, that is, a high removal rate of 90% or more was obtained.

[Example 2] Figure 2 (C) shows the existing advanced sewage treatment flow at a sewage treatment plant, in which biologically treated sewage secondary treated water 21 is treated by the common method of coagulation and precipitation. The water is then subjected to sand filtration treatment and reused as miscellaneous water 24.

FIG. 2(D) shows a flow in which a part of the above-mentioned miscellaneous water 24 is treated as raw water and subjected to further advanced treatment through reverse osmosis membrane treatment to regenerate and utilize highly pure industrial water 28.

The present invention converts concentrated water containing soluble COD components separated and concentrated by the reverse osmosis membrane in the treatment flow (D) into soluble COD components.
rg) is mixed into the flow of (C) as raw water.

The secondary treated sewage water 21 is temporarily stored in the adjustment tank 2 and sent to the chemical injection tank 4 by a pump. A flocculant 22 is injected into the chemical injection tank 4 and mixed with a stirrer, and after a flocculation time has elapsed in the flocculation tank 5, it is sent to the settling tank 6. The supernatant water of the settling tank 6 overflows, is stored in the water receiving tank 7, is sent to the sand filter device 23 by a pump, and the filtered water is reused as miscellaneous water 24.

On the other hand, the drawn sludge 9 drawn from the lower part of the settling tank 6 is sent to a sludge receiving tank 11 by a pump, and further sent to a dewatering device 12 by a pump. Separated. The dehydrated cake 14 is treated as industrial waste, and the separated water 13 is either directly discharged as N waste water or sent back to the adjustment tank 2 by a pump and reprocessed.

A part of the miscellaneous water 24 regenerated in the flow shown in FIG.
The permeated water is sent to a reverse osmosis membrane 27 by a high-pressure pump 26, and the permeated water is reused as high-purity industrial water 28.

On the other hand, concentrated water is treated as soluble COD raw water 19 in Figure 2 (C
) The sludge is sent to the sludge receiving tank 11 shown in the treatment flow and mixed with the drawn sludge 9 to form the mixed sludge 10.

The second mixed sludge 10 is sent to a dewatering device 12 by a pump,
Solid-liquid separation is performed in the dewatering device 12, and during this process, soluble COD components act on acidic metal ion components contained in the drawn sludge 9, and are removed and discharged together with the dehydrated cake 14.

The soluble COD components are removed from the separated water 13 and the water is discharged as waste water, or (C) it is remixed into the secondary treated sewage water before the flow treatment and subjected to coagulation and precipitation treatment.

[Effects of the Invention] According to the present invention, soluble C
By mixing OD raw water and performing solid-liquid separation, soluble CO caused by high-molecular organic compounds and biodegradable organic substances is removed.
As shown in Table 1, component D can be removed with a high removal rate of 90% or more, and even if the amount of the soluble COD component changes, there is an excellent effect that the removal rate does not decrease. Furthermore, existing flocculation, precipitation treatment, and dehydration treatment equipment conventionally used in general wastewater treatment can be effectively used, so there is no need to install dedicated equipment for removing soluble COD components. Since no chemicals are required for removal, equipment costs and running costs can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a processing flow of an embodiment in factory wastewater treatment of the present invention, FIG. 2 is a diagram showing a processing flow of an embodiment when the present invention is used for recycling treatment of secondary sewage treatment water, It is. 1: Factory wastewater, 2: Adjustment tank, 3: Neutralizing agent, 4: Chemical feeding tank, 5: Coagulation tank, 6: Sedimentation tank, 7: Water receiving tank, 8
: Treated wastewater, 9: Pulled sludge, 10: Mixed sludge, 1]
: Sludge receiving tank, 12: Dewatering device, 13: Separated water, 1
4: Dehydrated cake, 15: COD wastewater, 16: Adjustment tank, 17: Biological treatment tank (bag tank), 18: Sedimentation tank,
19: Dissolved COD raw water, 20: COD treated wastewater,
21: Secondary treated sewage water, 22: Coagulant, 23: Sand filter device, 24: Miscellaneous water, 25: Check filter 2
6; High pressure pump, 27; Reverse osmosis membrane, 28 Industrial water

Claims (2)

[Claims] (1) When sewage or factory wastewater is coagulated and sedimented, soluble COD raw water is mixed into the extracted sludge containing acidic metal ions, the mixed sludge is separated into solid and liquid by dehydration treatment, and the separated water is used as treated wastewater. Soluble COD characterized by
How to remove. (2) Soluble COD, characterized in that the separated water according to claim (1) is further mixed into the sewage or industrial wastewater before the coagulation-precipitation treatment step, subjected to the coagulation-precipitation treatment, and then discharged.
How to remove.