JPH09117800A - Biological treatment method of organic waste liquid - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] It is possible to reduce the volume of excess sludge, prevent deterioration of treated water quality such as increase in chromaticity and COD, and obtain high treated water quality at low cost. A biological treatment method for organic wastewater is proposed. A liquid to be treated 13 is introduced into an aeration tank 11 together with return sludge 14 for aerobic biological treatment, the treatment liquid is concentrated by a concentrating device 12, and a part of the concentrated sludge is returned to the aeration tank 11. In the aerobic treatment method of returning to the above, after introducing a part of the concentrated sludge into the solubilization treatment tank 21 and performing heat treatment in the presence of a surfactant to solubilize the sludge,
It is returned to the aeration tank 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for biological treatment of organic waste liquid, in which the organic waste liquid is biologically treated and the sludge produced is solubilized to reduce its volume.

[0002]

2. Description of the Related Art In a method of aerobically treating organic waste liquid in the presence of activated sludge, a large amount of surplus activated sludge which is hardly dehydrated is produced. A large amount of excess digested sludge is also produced by a method of anaerobically treating in the presence of anaerobic sludge. In order to reduce the volume of such excess sludge, a method of aerobically or anaerobically digesting excess sludge has been used. In the aerobic digestion, the excess sludge is simply aerated in a digestion tank to digest it, and the aerated sludge is separated into solid and liquid to return the separated sludge to the digestion tank. In anaerobic digestion, excess sludge is put into a digestion tank and digested by the action of anaerobic bacteria.

[0003] Such a digestion method digests by utilizing the action of aerobic or anaerobic organisms. However, since excess sludge itself is biologically stable through biological treatment, sludge is reduced. There is a limit to the volume of the sludge, usually 30
Only ４０40% is reduced in volume.

In order to improve such a point, Japanese Patent Publication No.
No. 61994 describes a method for treating organic wastewater in which excess sludge is solubilized at a pH of 2.5 or lower at a temperature of 50 ° C. or higher and then returned to an aeration tank. In addition, JP-A 1-224
No. 100 is anaerobic digested sludge at 100-180 ℃
Describes a method for treating organic sludge in which the solubilized sludge is returned to the anaerobic digestion tank after being solubilized in.

[0005]

However, although it is possible to reduce the volume of sludge by such a conventional method, since the conditions for solubilization treatment are severe at high temperatures, hardly biodegradable organic substances are produced. There is a problem that the chromaticity and COD of the treatment liquid are increased and the quality of the treated water is deteriorated, and a device with high heat resistance is required, which consumes a large amount of energy and is costly.

In order to solve the above problems, the object of the present invention is to suppress the deterioration of the quality of treated water, and to heat sludge at a low temperature to reduce the volume of sludge at a low cost. It is to propose a processing method.

[0007]

The present invention is a method for biologically treating an organic waste liquid in a biological treatment tank in the presence of biological sludge containing aerobic or anaerobic microorganisms. Introduced into the treatment tank, the biological treatment process of treating aerobic or anaerobic organisms in the presence of biological sludge containing aerobic or anaerobic microorganisms, and withdrawing the mixed liquid or concentrated sludge in the biological treatment tank, Is heated in the presence of a surfactant to perform a solubilization treatment, and then the solubilization treatment step of transferring the solubilization treatment to a biological treatment tank is carried out.

The organic effluent to be treated in the present invention is a effluent or sludge containing an organic substance to be treated by a biological treatment, but it may also contain a hardly biodegradable organic substance or an inorganic substance. . Such organic effluents include sewage, night soil, food factory effluents, other industrial effluents,
Examples thereof include sludge such as surplus sludge generated when treating these waste liquids.

The biological treatment step for biologically treating such organic waste liquid may be an aerobic biological treatment or an anaerobic biological treatment. Examples of aerobic biological treatment include activated sludge method and biofilm method. The activated sludge method is an aerobic biological treatment of organic wastewater in the presence of activated sludge.The organic wastewater is mixed with activated sludge in an aeration tank and aerated, and the mixture is concentrated by a concentrator. In general, a standard activated sludge method in which a part of the concentrated sludge is returned to the aeration tank is used, but another treatment method modified from the standard activated sludge method may be used. The biofilm method is a treatment in which a biofilm is formed on a carrier and aerobically brought into contact with the drainage. Examples of the anaerobic treatment include an anaerobic digestion method and a high-load anaerobic treatment method.

The treatment conditions for aerobic organism treatment and anaerobic organism treatment are not particularly limited, and ordinary aerobic organism treatment or anaerobic organism treatment conditions can be adopted. For example, in the case of aerobic biological treatment, the digestion tank (biological treatment tank) residence time can be set to 1 day or longer, usually 3 to 15 days in sludge digestion, and sludge load in organic sludge activated sludge treatment. Operation such as 0.1-0.5 kg-BOD / MLSS / day is possible. In the case of anaerobic treatment, the digestion tank (biological treatment tank) residence time in digesting sludge can be 2.5 days or longer, and usually 5 to 30 days.

In the present invention, a part of the biological sludge is extracted from the treatment system in such biological treatment, and the extracted sludge is solubilized. When removing the biological sludge, the concentrated sludge concentrated by the concentrating device may be withdrawn, or the mixed solution may be withdrawn from the biological treatment tank, but the solubilization process should be performed in a small capacity treatment tank. The former is preferred because it can be performed and requires less heating energy. As the concentrating device, a known device such as a precipitation device, a centrifuge or a membrane separation device can be used. Among these, the centrifugal separator and the membrane separator are preferable because the sludge can be highly concentrated.

The concentrated sludge can be partially or wholly extracted as a drawn-out sludge for solubilization treatment. In the former case,
It is possible to solubilize part of the concentrated sludge, return the other part to the biological treatment tank as return sludge, and discharge the rest as excess sludge or digested sludge. Since there are active microorganisms in the biological treatment tank and they proliferate using organic matter in the liquid to be treated and solubilized sludge as a substrate, it is not always necessary to return the sludge to the biological treatment tank. Since sludge can be supplied to the biological treatment tank, it is preferable to return sludge. In the present invention, in addition to excess sludge, it is preferable to further pull out a part of the sludge returned to the biological treatment tank as return sludge for solubilization treatment, in which case the amount of excess sludge generated can be further reduced. Depending on the conditions, the amount of excess sludge generated can be reduced to zero. In this regard,
More on this later.

In the present invention, the drawn sludge is heated in the presence of a surfactant to solubilize it. Examples of the surfactant used in the present invention include nonionic surfactants such as polyoxyethylene nonylphenyl ether and polyoxyethylene alkyl ether; anionic surfactants such as sodium laurylbenzene sulfonate and sodium dodecyl sulfate; Examples thereof include cationic surfactants such as tetradecylamine and cetyltrimethylammonium chloride. Among these, biodegradability is high,
Nonionic surfactants that do not inhibit the digestive activity of microorganisms are preferred.

The amount of surfactant added is M for solubilization treatment.
It is desirable that the amount of LVSS is 10 to 100,000 mg / kg, preferably 1,000 to 20,000 mg / kg. By adding the surfactant in such an amount, even if the solubilized sludge is introduced into the biological treatment tank and biologically treated, the digestive activity of microorganisms is not hindered and the efficiency of the entire treatment is affected. The effect of adding the surfactant can be obtained without causing a new load that affects the solubilization, and the solubilization treatment can be performed under milder conditions than the conventional method.
The surfactant is preferably added to the solubilization treatment tank (heat treatment tank) or the drawn sludge supplied to the solubilization treatment tank.

The heating temperature is 50 to 150 ° C., preferably 6
The temperature is preferably 0 to 90 ° C. The heating time is 15 minutes to 6 hours, preferably 30 as a residence time in the case of a continuous system.
It is desirable that the time is from 2 minutes to 2 hours, and in the case of a batch method, from 10 minutes to 6 hours, preferably 30 minutes to 1 hour.

By performing the solubilization treatment under such conditions, 90% or more of the organic sludge is modified into a readily biodegradable substance. Then, by subjecting the solubilized sludge to aerobic or anaerobic biological treatment, organic matter is decomposed by microorganisms and the sludge volume is reduced. Depending on the conditions, one-time solubilization treatment reduces the volume of 1/3 to 1/4 of the drawn-out sludge subjected to the treatment. The biological treatment of the solubilized sludge can be carried out by returning (circulating) it to the biological treatment tank of the treatment system from which the sludge has been extracted, or by introducing it into the biological treatment tank of another treatment system.

In the present invention, the larger the amount of sludge to be solubilized, the higher the sludge volume reduction rate. However, since the sludge grows when the organic matter in the solubilized sludge is biodegraded, the excess sludge cannot be reduced to zero simply by solubilizing the excess sludge, but the amount of grown sludge is apparent. When the excess sludge is extracted and solubilized so as to be zero, the amount of excess sludge generated from the entire system can be made zero. For example, when digesting sludge, considering the number of solubilization treatments that are circulated to the solubilization treatment tank during the residence time of the digestion tank (biological treatment tank),
An amount corresponding to approximately 1/3 to 1/6 of the amount of inflowing sludge may be solubilized. When the amount of sludge to be solubilized increases, the biological treatment performance may decrease, but in such a case, a carrier for supporting the sludge is provided in the biological treatment tank to maintain a certain amount of sludge. Thereby, the biological treatment performance can be maintained high.

The principle of sludge volume reduction in the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram for explaining the principle of sludge volume reduction. In the figure, 1 is a biological treatment system and 2 is a solubilization treatment system. The biological treatment system 1 is a treatment system that aerobically or anaerobically decomposes an organic waste liquid by bringing it into contact with biological sludge, and a biological treatment tank and a concentrating device are separately provided, but the entire system including them is included. Is shown as a processing system. The solubilization treatment system 2 is illustrated as a treatment system for solubilizing the drawn sludge drawn in the state of a mixed solution or a concentrated solution. Sludge is hydrolyzed by the solubilization process, and BOD
Become a source.

The biological treatment system 1 shown in FIG. 1 holds a certain amount of biological sludge 3a for biological treatment. When the liquid to be treated 4 is introduced into the biological treatment system 1 and biological treatment is performed, the BOD contained in the liquid to be treated 4 is assimilated into the biological sludge 3a, and a new generated sludge 3b is generated due to the proliferation thereof. On the other hand, the biological sludge 3a in the system self-decomposes, and the self-decomposed component 3c disappears. Therefore, in the steady state, the difference between the produced sludge 3b and the self-decomposition 3c grows as the grown sludge 3d.

A case where the sewage treatment system 2 treats the multiplied sludge 3d as excess sludge is shown by a broken line 5 in FIG.
When solubilized sludge 3d is returned to biological treatment system 1,
BOD generated by the solubilization process is converted into sludge, and another generated sludge 3e is generated, and this amount becomes a substantial sludge growth amount and must be discharged as excess sludge. On the other hand, a larger amount of the extracted sludge 3f than the propagated sludge 3d is extracted from the biological treatment system 1, solubilized by the solubilization treatment system 2 and converted into BOD, and the solubilized sludge 6 is converted into the biological treatment system 1.
By returning to BOD, another 3 g of produced sludge is produced from the BOD produced by the solubilization treatment. In this case, the difference between the drawn sludge 3f and the produced sludge 3g becomes the mineralized portion 3h.

Here, a larger amount of the extracted sludge 3f than the propagated sludge 3d is solubilized and converted into BOD.
Compared to the case of solubilizing only the propagated sludge 3d, the mineralized portion is increased and the sludge volume reduction rate is increased. Breeding sludge 3
3d of drawn sludge so that d and the mineralized portion 3h become equal
When the amount of is determined, the surplus sludge becomes substantially zero. When the amount of the grown sludge 3d is larger than that of the mineralized portion 3h, the difference becomes a substantially increased portion 3i, and the excess sludge 7 is discharged out of the system. 8 is a treatment liquid of the biological treatment system 1.

In the biological treatment system 1, the biological treatment capacity is V, the biological sludge concentration is X, the sludge yield is Y, the treated liquid flow rate (treatment liquid flow rate) is Q, the organic matter concentration of the treated liquid is Ci,
The concentration of organic matter in the treated liquid is Ce, the concentration of biologically treated organic matter is (Ci-Ce), the sludge self-decomposition constant is Kd, the excess sludge discharge amount is q, the amount drawn into the solubilization treatment system is Q ', and the solubilization treatment is performed. The mass balance is represented by the following equation [1], where k is the rate at which the generated sludge is converted back into biological sludge.

[0023]

[Formula 1] V dX / dt = YQ (Ci−Ce) −V Kd X−q X−Q′X + k Q′X [1] In the formula [1], V dX / dt is the biological sludge in the biological treatment system 1. 3a, YQ (Ci-Ce) is the amount of produced sludge 3b, V Kd X is the amount of self-decomposition 3c, q X is the amount of excess sludge 7 discharged, Q'X is the amount of extracted sludge 3f, k Q'X is generated sludge 3
The amount of g is shown.

Where Q (Ci-Ce) / V = LV (tank load), q
/ V = 1 / SRT (excess sludge retention time ratio), Q '/ V = θ (circulation ratio of biological sludge to the solubilization treatment system), (1-k) = δ
Assuming (mineralization rate), in a steady state, the equation [1] is simplified as the following equation [2].

[Formula 2] Y LV / X = Kd + 1 / SRT + δθ [2]

In a normal biological treatment system in which the solubilization treatment system 2 does not exist, the third term (δθ) in the equation [2] does not exist, so when the sludge load is constant, excess sludge (X / SRT) is calculated in the second term. ) Is determined. On the other hand, in the treatment system in which the solubilization treatment is combined, as is apparent from the equation [2], the volume of the excess sludge is reduced by the value of the third term. And under the condition that the value of the third term is comparable to the value of the second term, it is possible to set the sludge load to a normal value without discharging the excess sludge (1 / SRT = 0). is there.

In the method of the present invention, the solubilization treatment is carried out in the presence of a surfactant, and in order to obtain a volume reduction rate comparable to that of the conventional method, the treatment is carried out at a temperature lower than the conventional temperature or at the same temperature. Can be solubilized in a short time.
For this reason, it is possible to suppress the production of difficult biodegradable components,
Moreover, it is possible to use a device having a lower heat resistance than that of the conventional one, reduce energy consumption, and suppress odor.

[0027]

Embodiments of the present invention will now be described with reference to the drawings. 2 to 4 are system diagrams showing biological treatment apparatuses of different embodiments, FIG. 2 is an example of solubilizing concentrated sludge obtained by concentrating an aerobic treatment liquid by a concentrating apparatus, and FIG. 3 is an aeration tank. FIG. 4 shows an example of solubilizing the mixed liquid in the inside, and FIG. 4 shows an example of solubilizing the mixed liquid in the anaerobic biological treatment tank. In FIG. 2, 1 is an aerobic biological treatment system,
2 is a solubilization treatment system, 11 is an aeration tank, 12 is a precipitation device as a concentrating device, 21 is a solubilization treatment tank, 23 is a surfactant supply passage, and 24 is a heater.

In the aerobic biological treatment method of the organic waste liquid by the treatment apparatus of FIG. 2, the organic waste liquid or sludge is introduced from the liquid passage 13 into the aeration tank 11 and returned through the return sludge passage 14. Air mixed with the returned sludge and the activated sludge in the aeration tank 11 and supplied with air from the air supply passage 16 is used as the air diffuser 1
Aerate from 5 and perform aerobic biological treatment. As a result, the organic matter in the liquid to be treated is decomposed by the biological oxidation reaction.

A part of the mixed liquid (reaction liquid) in the aeration tank 11 is introduced into the settling device 12 through the communication path 17 and separated into a separated liquid and a separated sludge (concentrated sludge) by sedimentation separation. The separated liquid is discharged as a treated liquid from the treated liquid passage 18 to the outside of the system, the separated sludge is taken out from the separated sludge take-out passage 19, a part of it is returned as the returned sludge to the aeration tank 11 from the returned sludge passage 14, and the remaining part Some or all of them are introduced into the solubilization treatment tank 21 through the sludge extraction passage 22 to perform the solubilization treatment.

In the solubilization treatment tank 21, the surfactant is added from the surfactant supply passage 23, heated by the heater 24, and the drawn sludge is solubilized by the agitator 25 while gently stirring. As a result, sludge is hydrolyzed and BO
Convert to D. The solubilized sludge is continuously returned from the solubilized sludge passage 26 to the aeration tank 11 and treated with aerobic organisms. As a result, the BOD component converted by the solubilization treatment is decomposed and removed, and the excess sludge generated from the aerobic biological treatment system 1 is reduced in volume. When excess sludge is generated, it is discharged from the excess sludge discharge path 20 to the outside of the system.

The treatment method by the apparatus of FIG.
A part of the mixed liquid in the inside is drawn out from the sludge drawing path 22 as drawn sludge, and a surfactant is added to the drawn sludge from the surfactant supply path 23, and then introduced into the solubilization treatment tank 21 for solubilization treatment. To do. Other operations are the same as those in FIG.

Although the precipitation device 12 is used as the concentrating device in FIGS. 2 and 3, other concentrating devices such as a membrane separating device and a centrifugal separating device can also be adopted. Further, instead of the aeration tank 11, an anaerobic treatment tank can be used for anaerobic treatment. Further, the solubilized sludge can be transferred to an aerobic or anaerobic biological treatment system other than the biological treatment system 1 from which the sludge has been extracted for biological treatment.

In FIG. 4, 1 is an anaerobic biological treatment system,
2 is a solubilization treatment system, 31 is an anaerobic treatment tank, and 36 is a membrane separation device. In the treatment method by the treatment device of FIG. 4, the organic sludge or sludge is introduced into the anaerobic treatment tank 31 from the liquid passage 13 to be treated and the organisms in the returned sludge and the anaerobic treatment tank 31 are returned through the return sludge passage 14. Mixer with sludge 32
The anaerobic biological treatment is performed with gentle stirring. As a result, the organic matter in the liquid to be treated is decomposed by the acid-producing bacterium and the methane-fermenting bacterium. The digestion gas containing the produced methane gas is discharged from the exhaust gas passage 33.

A part of the mixed liquid (reaction liquid) in the anaerobic treatment tank 31 is taken out from the communication passage 17, pressurized by the pump 34, guided to the membrane separation device 36, and separated by the separation membrane 37. As a result, the permeated liquid 38 and the concentrated liquid 39 are separated. The permeated liquid 38 is discharged as a treated liquid from the treated liquid passage 18 to the outside of the system, the concentrated liquid 39 is taken out from the concentrated liquid take-out passage 19a, and is returned to the anaerobic treatment tank 31 from the returned sludge passage 14 as excess sludge. When it occurs, it is discharged from the excess sludge discharge path 20 to the outside of the system.

In the solubilization treatment system 2, a part of the mixed liquid in the anaerobic treatment tank 31 is drawn out as sludge from the sludge drawing passage 22 and introduced into the solubilization processing tank 21 for solubilization treatment. Other operations are the same as those in FIG.

In FIG. 4, a membrane separator 36 is used as a concentrator.
However, other concentrating devices such as a precipitation device and a centrifuge can also be used. Also, anaerobic treatment tank 31
It is also possible to perform aerobic treatment using an aeration tank instead of.

[0037]

【Example】

Comparative Example 1 The apparatus of FIG. 3 was used, but the solubilization treatment in the solubilization treatment system 2 was omitted, and the organic waste liquid was aerobically treated. That is, sewage surplus sludge (MLSS = 6000 mg / l)
0 liter aeration tank 11 and 10 liter settler 12
Was continuously processed. Sludge was continuously added at a rate of 4 liters / day. The mixed solution in the aeration tank 11 was withdrawn by 1 liter a day. As a result, after 2 months, the MLSS in the aeration tank 11 was 10,
It became 600 mg / l.

Comparative Example 2 With the above operation, the mixed solution in the aeration tank 11 was lit for 1.5 liters a day.
er was drawn out, introduced into the solubilization treatment tank 21, heated at 60 ° C. for 2 hours for solubilization treatment, and returned to the aeration tank 11. The solubilization treatment was performed every day. When operated with the MLSS maintained at 10,000 mg / l, excess sludge was reduced to 1 after 60 days.
It produced 4.7 g dry weight per day. CO of this treated water
D _Cr was 310~380mg / l. The COD _Cr of the treated water was measured on the supernatant obtained by centrifugation at 15,000 rpm for 5 minutes.

Comparative Example 3 With the above operation, the mixed liquid in the aeration tank 11 was drawn out by 1 liter per day, introduced into the solubilization treatment tank 21 and heated at 120 ° C. for 2 hours for solubilization treatment. I returned to. The solubilization treatment was performed every day. When the entire amount of the settled sludge was returned to the aeration tank 11 without discharging the excess sludge, the MLSS gradually increased. 2 months later, MLSS is 16,000 mg
Stable around / l. The COD _{Cr of} this treated water is 730 to
It was 840 mg / l.

Example 1 In parallel with the operation of Comparative Example 2, the mixed liquid in the aeration tank 11 was changed to 1
1 liter per day was drawn and introduced into the solubilization treatment tank 21 for solubilization treatment. The solubilization treatment is performed by using polyoxyethylene nonylphenyl ether (HL
B = 14) was added and the reaction was carried out at 60 ° C. for 2 hours. The solubilization treatment was performed every day, and the solubilization-treated sludge was returned to the aeration tank 11.
Excess sludge is not discharged at all and all settled sludge is aerated tank 1
When it was returned to 1, the MLSS gradually increased, but after about 1 month, it was stabilized at 12,000 to 14,000 mg / l. The COD _{Cr of} this treated water is 360 to 540 mg.
/ L.

Example 2 Following Example 1, the mixed solution in the aeration tank 11 was lit for 1 day per day.
er was drawn out and introduced into the solubilization treatment tank 21 for solubilization treatment. The solubilization treatment was performed at 60 ° C. for 2 hours by adding sodium laurylbenzenesulfonate (anionic surfactant) in an amount of 1% with respect to the heat-treated sludge amount. The solubilization treatment was performed every day, and the solubilization-treated sludge was returned to the aeration tank 11.
As a result, MLSS was 13,000 to 15,000 mg.
It was stable at 1 / l, and it was not necessary to discharge the excess sludge (all the settled sludge was returned to the aeration tank 11). The COD _{Cr of} this treated water was 430 to 570 mg / l.

From the above results, it is understood that by adding the surfactant, the sludge volume reduction rate is high even if the solubilization treatment is performed at a low temperature. That is, 6 using a surfactant
Volume reduction effect when solubilized at 0 ° C (Examples 1 and 2)
The same or higher results were obtained as in the case of solubilizing treatment at 120 ° C. without adding a surfactant (Comparative Example 2). Moreover, COD _Cr of Examples 1 and 2 is lower than that of Comparative Example 2, and it can be seen that deterioration of treated water can be suppressed.

[0043]

The biological treatment method for organic waste liquid of the present invention comprises:
Since the mixed solution or concentrated sludge in the biological treatment tank is drawn out, the extracted sludge is heated in the presence of a surfactant to be solubilized, and then transferred to the biological treatment tank. It is possible to reduce the volume of sludge at low cost by using a device that suppresses deterioration of water quality and has low heat resistance.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining the principle of sludge volume reduction.

FIG. 2 is a system diagram showing a biological treatment apparatus according to an embodiment of the present invention.

FIG. 3 is a system diagram showing a biological treatment apparatus according to another embodiment of the present invention.

FIG. 4 is a system diagram showing a biological treatment apparatus according to another embodiment of the present invention.

[Explanation of symbols]

 1 Biological treatment system 2 Solubilization treatment system 3a Biological sludge 3b, 3e, 3g Produced sludge 3c Self-decomposition 3d Proliferation sludge 3f Extracted sludge 3h Mineralized part 3i Increased part 4 Solubilized sludge 7 Excess sludge 8 Treatment Liquid 11 Aeration tank 12 Precipitator 13 Processed liquid path 14 Returned sludge path 15 Air diffuser 16 Air supply path 17 Communication path 18 Treatment liquid path 19 Separation sludge discharge path 19a Concentrated liquid discharge path 20 Excess sludge discharge path 21 Solubilization treatment Tank 22 Sludge extraction passage 23 Surfactant supply passage 24 Heater 25, 32 Stirrer 26 Solubilization treatment sludge passage 31 Anaerobic treatment tank 33 Exhaust gas passage 34 Pump 36 Membrane separation device 37 Separation membrane 38 Permeate 39 Concentrated liquid

Claims (1)

[Claims] 1. A method of biologically treating an organic effluent in a biological treatment tank in the presence of biological sludge containing aerobic or anaerobic microorganisms, the method comprising introducing the organic effluent into the biological treatment tank, A biological treatment process for treating aerobic or anaerobic organisms in the presence of biological sludge containing aerobic or anaerobic microorganisms, and withdrawing the mixed liquid or concentrated sludge in the biological treatment tank, and extracting this extracted sludge in the presence of a surfactant. And a solubilization treatment step of transferring to a biological treatment tank after heating and solubilization treatment.