JPH0889991A - Treatment of waste water - Google Patents

Abstract

PURPOSE: To provide a treating method of a waste water capable of reducing the amount of a surplus sludge generating in a biological treatment. CONSTITUTION: Waste water 1 to be treated is introduced previously to a reactor 12 and a solid matter in the waste water 1 is converted into a soluble org. matter by hydrolysis/org. acid fermentation, then the solid matter is separated by a solid liq. separating device 13 and a part of the surplus sludge 15 is discharged. An effluent liq. 16 of the solid liq. separation is introduced to a biological reactor 3, and a waste water treatment by a usual biological treating method to discharge the surplus sludge 6. The surplus sludges 6 and 15 are sent to a concentrating device 7, a dehydrating device 8 and a drier/incinerator 9 to be treated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biological treatment method for wastewater containing high concentrations of organic matter, nitrogen and solid matter such as human waste and various industrial wastewaters.

[0002]

2. Description of the Related Art A conventional biological treatment method for wastewater is as shown in FIG. 5, in which a simple pretreatment step 2 such as a fine screen for removing coarse solids and impurities in the wastewater 1 is applied to the wastewater 1. After being applied, the biological reaction tank 3 is introduced into various biological reaction tanks 3 for treatment such as activated sludge method for removing organic matters and nitrogen, biological nitrification denitrification method, etc., and the biological reaction tank 3 is installed by the solid-liquid separation device 4 installed thereafter. The microorganisms therein are separated and collected and circulated as a partially returned sludge 5 into the biological reaction tank 3, and a part is withdrawn as an excess sludge 6.

From the solid-liquid separation device 4, in addition to the excess sludge 6,
The treated water 17 is discharged. The surplus sludge 6 is treated in the sludge treatment process. In the sludge treatment, first, the concentration of solids is greatly increased by the concentrator 7 and the dehydrator 8 (3-4% → 3).
(0 to 40%), and thereafter, it is introduced into the drying / incineration device 9, and finally becomes incinerated ash 10 and exhaust gas 11. Biological reaction tank 3
May be a single tank or multiple tanks depending on the purpose, and may be either aerobic or anaerobic for denitrification.

[0004]

In the conventional method, the excess sludge generated from the biological treatment of wastewater is the amount of solids in the stock solution after the pretreatment step that was not decomposed in the biological reaction tank and dissolved. It is the amount obtained by subtracting the amount of self-degradation of microorganisms from the amount of bacterial growth that serves as a carbon source for volatile organic matter. The decomposition ability is extremely small.

Most of the excess sludge is caused by the solid matter in the undiluted solution after the pretreatment, and there is a fundamental problem that the sludge treatment process is excessive and the equipment cost and the operating cost increase. In order to make the sludge treatment process compact and reduce equipment and operating costs, it is necessary to reduce the amount of excess sludge itself.

[0006] An object of the present invention is to provide a wastewater treatment method capable of reducing the amount of excess sludge generated in biological treatment.

[0007]

According to the present invention, since the solid matter in the stock solution after the pretreatment step is decomposed with high biological efficiency to reduce the amount of excess sludge, the usual biological treatment is carried out. Preliminary hydrolysis of wastewater before treatment by applying the method
Organic acid fermentation is applied.

Conventionally, there is an anaerobic digestion method as a biological treatment method for wastewater having a high solid substance decomposing ability, which is a combination of hydrolysis / organic acid fermentation and methane fermentation. It is common to carry out hydrolysis / organic acid fermentation and methane fermentation in a single tank by utilizing the above cycle, and it was extremely difficult to carry out the reaction in independent and separate tanks.

In the present invention, this hydrolysis / organic acid fermentation is applied as a pre-step of a normal biological treatment method such as an activated sludge method or a biological nitrification / denitrification method, and a solid matter in a stock solution is converted into a soluble organic matter. Convert.

According to this wastewater treatment method of the present invention, the wastewater to be treated is previously introduced into the biological reaction tank as described above, and the solid matter in the wastewater is dissolved by hydrolysis / organic acid fermentation. Since it is converted to organic matter and then subjected to normal biological treatment, the amount of excess sludge generated is greatly reduced.

Next, in another aspect of the present invention, in order to reduce the amount of surplus sludge generated when biological treatment of wastewater is performed, the wastewater before application of normal biological treatment is concentrated and separated by concentration separation. And a concentrated and separated supernatant liquid, and the concentrated and separated liquid is introduced into a biological reaction tank to convert the solid matter into a soluble organic matter by hydrolysis and organic acid fermentation. The mixed solution of the treatment solution thus obtained and the above-mentioned concentrated and separated supernatant is treated by an ordinary biological treatment method.

[0012] Thus, before carrying out the hydrolysis / organic acid fermentation, the solid matter in the wastewater is concentrated and separated into a soluble organic matter and a solid organic matter, and only the solid organic matter is hydrolyzed / organic acid. Fermentation is performed to efficiently decompose only solid organic matter in wastewater.

The reason is that when the waste water containing the soluble organic matter and the solid organic matter is subjected to hydrolysis / organic acid fermentation, only the easily degradable soluble organic matter is decomposed and the solid organic matter is not decomposed. .

[0014]

Embodiments of the wastewater treatment method according to the present invention will be specifically described below with reference to FIGS. 1 and 2. 1 and 2, the same steps as those in the conventional processing method shown in FIG. 5 are designated by the same reference numerals, and the duplicated description thereof will be omitted.

(First Embodiment) First of all, referring to FIG.
An embodiment will be described. In FIG. 1, 12 is a biological reaction tank and 13 is a solid-liquid separation device. After applying the same pretreatment step 2 to the wastewater 1 as in the conventional method, organic matter is stored in a biological reaction tank 12 (which may be anaerobic or aerobic) which is hermetically sealed so that oxygen is not mixed from the outside. Acid fermentation is performed to decompose solids and convert them into soluble organic substances.

After that, the solid-liquid separation device 13 separates and collects the microorganisms, circulates them in the biological reaction tank 12 as partly returned sludge 14, and sends them to the sludge treatment step as partly surplus sludge 15. The solid-liquid separation device 13 may be any of gravity separation, centrifugal separation, pressure floating separation, and membrane separation.

The solid-liquid separation effluent 16 is subjected to a treatment such as an ordinary activated sludge method and a biological nitrification denitrification method in the biological reaction tank 3, and the solid-liquid separation device 4 collects microorganisms to partially Is returned to the biological reaction tank 3 as return sludge 5, and excess sludge 6 is sent to the concentrator 7.

The excess sludge generated by the treatment method shown in FIG. 1 is 15 and 6, but the total amount thereof is smaller than the excess sludge generated by the conventional treatment method.

(Second Embodiment) Next, a second embodiment of the wastewater treatment method according to the present invention will be specifically described with reference to FIG. In FIG. 2, reference numeral 20 denotes a solid-liquid separator, and the solid-liquid separator 20 separates waste water into a concentrated separated liquid 22 and a concentrated separated supernatant liquid 21. Other components are as described in FIG.

In FIG. 2, after applying a pretreatment step 2 similar to the conventional method to wastewater, the solid matter is concentrated and separated by the solid-liquid separation device 20, and the concentrated separation liquid 22 and the concentrated separation supernatant liquid 2 are collected.
Divide into 1. At this stage, most of the solids in the stock solution after pretreatment move to the concentrated separation liquid 22.

The concentrated separated liquid 22 is subjected to organic acid fermentation in a bioreaction tank 12 (either anaerobic or aerobic) which is hermetically sealed so that oxygen is not mixed from the outside, and the solid matter is decomposed and dissolved. Try to convert to organic substances. After that, the solid-liquid separation device 13 for collecting microorganisms separates and collects the microorganisms, circulates them in the biological reaction tank 12 as partly returned sludge 14, and sends them as partly surplus sludge 15 to the extraction sludge treatment process. The solid-liquid separators 20 and 13 include gravity separation, centrifugal separation,
Various methods such as pressure floating separation and membrane separation are conceivable, and any method may be used.

Concentration separation supernatant 21 and solid-liquid separation apparatus 1
The effluent 16 of 3 is subjected to usual biological nitrification denitrification method, activated sludge method, etc. in the biological reaction tank 3, microorganisms are recovered in the solid-liquid separation device 4, and a part of the effluent 16 is returned as sludge 5. The excess sludge 6 returned to the reaction tank 3 is sent to the concentrator 7. The amount of excess sludge generated is excess sludge 15 and 6, which is smaller than in the past.

Next, in order to confirm the effect of the wastewater treatment method according to the present invention, an example of an experiment conducted on human waste will be described.

[0024] (Experimental Example) target solution, night soil in properties after pretreatment obtained from certain human waste treatment _plant, BOD 5 8900 (m
g / l), CODM _n 5100 (mg / l), T-N3200 (mg / l), SS960
It is 0 (mg / liter). A conventional wastewater treatment method and the wastewater treatment method according to the present invention were applied to this human waste, and the amounts of excess sludge generated were compared.

The conventional wastewater treatment method was carried out by the experimental apparatus shown in FIG. The basic specifications are as shown in FIG. In FIG. 6, the reaction tank and the denitrification tank correspond to the biological reaction tank 3 shown in FIG. In this reaction tank, nitrification and denitrification are performed at the same time as the removal of organic substances, and the oxidized nitrogen remaining in the subsequent denitrification tank is removed.

FIG. 3 shows a part of the apparatus for experimenting the wastewater treatment method according to the present invention up to the part where hydrolysis and organic acid fermentation are carried out. The wastewater after the pretreatment by the apparatus shown in FIG. 3 was introduced into the same apparatus as shown in FIG. 6 for biological treatment, but the part is not shown.

As the seed sludge, an anaerobic digestion sludge of night soil treatment plant was used. According to the conventional treatment method, the amount of excess sludge generated was 7.9 kg / kl in terms of solid amount per unit treatment amount, whereas the amount generated in the treatment method of the present invention (organic acid fermentation step and The total of the biological treatment steps) was 4.8 kg / kl, which was a reduction of about 40%.

Next, FIG. 4 shows a part of another apparatus for experimenting with the wastewater treatment method according to the present invention, up to the part for carrying out hydrolysis and organic acid fermentation, as in FIG. The above target liquid was subjected to gravity separation for solid concentration separation, the concentrated separation liquid was subjected to organic acid fermentation, and the fermented water and the solid content concentration separation supernatant were mixed and treated with the same apparatus as shown in FIG. .
Anaerobic digestion sludge was used as the seed sludge.

The amount of surplus sludge generated in the conventional method was 7.9 kg / kl in terms of the solid amount per unit treated amount, whereas in the case of the treatment method based on the present invention (the organic acid fermentation step and the latter stage). The total of the biological treatment steps) was 4.0 kg / kl, which could be reduced by about 50%. Compared with the conventional equipment cost and operating cost, the sludge treatment reduced about 50%, the pretreatment according to the present invention increased 20%, and thus the total reduction was 30%.

[0030]

As described above, according to the present invention,
By introducing the wastewater to be treated into a biological reaction tank in advance, converting the solid matter in the wastewater into soluble organic matter by hydrolysis and organic acid fermentation, and then treating the treated solution with a biological treatment method. Since the amount of excess sludge itself is reduced, the sludge treatment process can be made compact and the equipment cost and operating cost can be reduced.

[Brief description of drawings]

FIG. 1 is an equipment configuration diagram for explaining an embodiment of a wastewater treatment method according to the present invention.

FIG. 2 is an equipment configuration diagram for explaining another embodiment of the wastewater treatment method according to the present invention.

FIG. 3 is an equipment configuration diagram showing an experimental apparatus for a wastewater treatment method of the present invention.

FIG. 4 is a device configuration diagram showing another experimental device of the wastewater treatment method of the present invention.

FIG. 5 is an equipment configuration diagram for explaining a conventional wastewater treatment method.

FIG. 6 is a device configuration diagram showing an experimental device of a conventional wastewater treatment method.

[Explanation of symbols]

 1 Wastewater 2 Pretreatment process 3 Biological reaction tank 4 Solid-liquid separator 5 Partly returned sludge 6 Excess sludge 7 Concentrator 8 Dehydrator 9 Drying / incinerator 10 Incinerator ash 11 Exhaust gas 12 Bioreactor 13 Solid-liquid separator 14 1 Partly returned sludge 15 Partial surplus sludge 16 Solid-liquid separation runoff water 17 Treated water 20 Solid-liquid separation device 21 Concentrated liquid separation supernatant 22 Concentrated separated liquid

Claims (2)

[Claims] 1. A biological treatment method for wastewater containing high concentrations of organic matter, nitrogen, and solid matter, wherein the wastewater to be treated is previously introduced into a biological reaction tank and the solid matter in the wastewater is hydrolyzed. A method for treating wastewater, which comprises treating the treated liquid by a conventional biological treatment method after converting it into a soluble organic substance by organic acid fermentation. 2. A biological treatment method for wastewater containing high concentrations of organic matter, nitrogen and solid matter, wherein the wastewater to be treated is separated into a concentrated separation liquid and a concentrated separation supernatant liquid by concentration separation, and the same concentration. After introducing the separated liquid into the biological reaction tank and converting the solid matter into soluble organic matter by hydrolysis and organic acid fermentation, the mixture of the treated liquid and the concentrated separation supernatant is subjected to normal biological treatment. A method for treating wastewater, which is characterized in that it is treated by a method.