JP2003039098A - Acclimation method for microorganisms and sludge volume reduction method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acclimation method for microorganisms participating in sludge volume reduction whereby the microorganisms are acclimated so as to efficiently conduct the sludge volume reduction under alkaline conditions at 20-80 deg.C. SOLUTION: This acclimation method is characterized in that, in a sludge volume reduction treatment under alkaline conditions at 20-80 deg.C, stages having pH's different from each other by 0.1-5 are set and these stages are conducted in the order of from a stage having a lower pH to that having a higher pH in 1-63 days.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sludge treatment method for reducing the volume or eliminating excess sludge generated by wastewater treatment.

[0002]

2. Description of the Related Art Currently, as a typical biological wastewater treatment method, there is an activated sludge method in which a BOD component is decomposed into microorganisms under aerobic conditions and precipitation / separation is performed in a subsequent stage. In this method, a part of the sludge that has been settled is returned to the aeration tank, but it is necessary to treat it as excess sludge after solid-liquid separation in a settling tank or the like. Some of this excess sludge is being reused as soil conditioner and compost material, but most of it is treated as industrial waste. However, methods other than disposal methods are required due to cost considerations and environmental considerations.

[0003] Conventionally, as a method of disposing of excess sludge, a method in which pretreatment such as dehydration and incineration is performed and then the waste sludge is disposed of is mainly used. In this method, it is necessary to prepare a dehydrator or dryer that consumes a large amount of power to treat a large amount of excess sludge. When incinerated, a large amount of heat energy is required. In addition, landfill costs are rising year by year due to tight landfill sites and regulatory issues.

On the other hand, various methods of reducing the volume of sludge to reduce the amount of excess sludge generated have been tried. An anaerobic digestion method is known as an existing technology for reducing the volume of excess sludge, but it has not been widely used recently because the residence time takes 10 to 30 days and the scale of the apparatus increases. Other proposed methods include physical / chemical methods, biological methods,
There are biological methods combined with various sludge pretreatment processes. The treatment of sludge by wet oxidation disclosed in JP-A-4-78496 and the treatment of sludge with supercritical water disclosed in JP-A-9-276900 are sludge volume reduction methods using physical / chemical methods. . As a biological method, there is a method of reducing the volume of sludge by repeating thermophilic biological digestion and mesophilic biological digestion described in Japanese Patent Publication No. 6-509986. In biological methods combined with various pretreatment steps, after sludge is chemically or physically pretreated,
Methods for anaerobically or aerobically treating microorganisms are being studied. This is a method aiming at shortening the treatment time by microorganisms in the latter stage by solubilizing or easily decomposing sludge. For example, JP-A-59-10589
No. 7 publication improves the digestion efficiency of an anaerobic digestion method by treating sludge with ozone. Japanese Patent Laid-Open No. 7-116
In Japanese Patent Laid-Open No. 685 and Japanese Patent Laid-Open No. 8-19899, the sludge cell wall is treated with ozone, and then the volume of the sludge is reduced in an aerobic tank. Is added and treated under alkaline or acidic conditions and then subjected to aerobic treatment. Japanese Patent Laid-Open No. Hei 4
In JP-A-326998 and JP-A-5-345200, sludge is made alkaline, and at the same time, it is heated to 50 to 100 ° C. to perform a hot alkali treatment to promote solubilization, and then to perform anaerobic treatment near neutrality. Is the way. Moreover,
Method for solubilizing sludge by heating treatment (60 to 80 ° C.) (JP-A-8-229595, JP-A-8-243)
595), a method of pretreating sludge with ultrasonic waves to improve the digestion efficiency of the anaerobic digestion method (JP-A-58-76200).
(Japanese Patent Laid-Open No. 9-117800), the sludge is anaerobically treated by heating the sludge in the presence of a surfactant to solubilize the sludge, and then returning the sludge to the aeration tank. After the treatment, ozone treatment or high-pressure pulse discharge treatment is performed, and the volume of sludge is reduced by returning it to the anaerobic treatment process (JP-A-9-206785). Method of returning sludge and treating sludge (Japanese Patent Publication No. 57-19719, Japanese Patent Laid-Open No. Hei 6)
No. -206088). Further, as a sludge solubilizing means, a method of adding a thermophilic microorganism as disclosed in JP-A-9-253699 has been proposed.

However, the conventional physical / chemical sludge treatment methods typified by supercritical water, ultrasonic waves, ozone, high-pressure pulse discharge, acid or alkali, and the addition of surfactants require equipment cost, electricity and chemical charges. There is concern that running costs will be high. Furthermore, when an acid or an alkali is added, equipment and chemical costs for neutralization are required. When using thermophiles in biological methods as well, the cost increase for heating is a problem. A large number of tanks are required in the method of repeating thermophilic bio-digestion and mesophilic bio-digestion, and even in the method of anaerobically or aerobically treating microorganisms after sludge pretreatment, at least the pretreatment tank and the microorganism treatment tank are required. It becomes necessary and takes up a lot of space, which is a problem. On the other hand, when the pretreated sludge is returned by using the microorganism treatment tank also as the activated sludge tank, the sludge is only solubilized and the BOD load itself is almost the same as before the treatment, so the load of the activated sludge tank is greatly increased. This is applicable only when the activated sludge tank has a sufficient processing capacity.
There is a demand for a system capable of not only solubilizing sludge but also reducing its volume, that is, decomposing sludge components, with a small number of tanks.

Therefore, the present inventors have utilized sludge solubilizing conditions that are not suitable for the normal growth of microorganisms, which are alkaline / medium / high temperature conditions, and utilize sludge-degrading microorganisms. A method of solubilizing sludge and simultaneously decomposing sludge by microorganisms has been proposed (JP-A-11-77099, etc.). Furthermore, a Bacillus bacterium having a high sludge decomposing ability that can be used in this treatment method has been obtained (JP-A-12-139449). On the other hand, Japanese Unexamined Patent Publication No. 9-136097 proposes a sludge treatment method of aerating in the presence of aerobic microorganisms under alkaline conditions and returning the sludge to the biological treatment step. The purpose is to reduce the amount of acid chemicals added for summing, which is different from the proposal of the present inventors in that there is almost no microbial decomposition of sludge.

[0007]

In the sludge volume reduction treatment method under alkaline / medium / high temperature conditions proposed by the present inventors, Bacillus bacteria having high sludge decomposing ability play a major role in the treatment. Not only by the bacteria that were killed,
A high degree of treatment is achieved by the combined action with other microbial groups. Most of the microorganisms in the natural world coexist with various mutual relationships (composite microbial system) and analyze interactions etc. even though they have advanced functions that cannot be obtained by a single microorganism. Due to lack of technology, most are left unused. The same applies to water treatment,
It is considered that the function of the complex microbial system is not merely the sum of the functions of the pure culture system, but also the function expressed by the complex microbial system. It is said that more than 90% of the microorganisms that cannot be cultivated even with the activated sludge used for many years have been cultivated, and the functions of most microorganisms have not been elucidated. Even in sludge volume reduction treatment, acclimation was performed in order to treat with a complex microbial system of Bacillus bacteria with sludge decomposing ability that is the main role and microorganisms that are difficult to separate, but the growth conditions of these microorganisms have not been clarified. Therefore, it sometimes took a long time to get used to it. Therefore, the present invention, after adding a microorganism having a high sludge decomposing ability, when performing an excess sludge volume reduction treatment under alkaline and medium-high temperature conditions, acclimate up to a sludge decomposing ability that exhibits a high level volume reduction rate. The purpose is to

[0008]

In order to achieve the above object, the present invention basically has the following configuration.

That is, "alkaline conditions and 20-80 ° C
When performing the sludge volume reduction treatment under the conditions of, the pH condition is provided with steps different from 0.1 to 5, and these steps are
A method for acclimatizing a group of microorganisms involved in sludge volume reduction, which is performed from a step of low H to a step of high H over 1 to 63 days. It is.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The details of the present invention will be specifically described below.

According to the present invention, when sludge volume reduction treatment is carried out under alkaline conditions, steps having different pH conditions of 0.1 to 5 are provided, and these steps are changed from low pH steps to high pH steps. By performing the treatment over 63 days, it is possible to acclimate the microorganism group involved in sludge volume reduction so that high efficiency resolution can be achieved in a short period of time.

In the present invention, it is necessary to provide a step in which pH conditions are different by 0.1 to 5. It is preferably 0.2 to 1, and more preferably 0.2 to 0.5.
Is. If it is less than the lower limit of the above numerical range, the acclimatization period becomes long, and if it exceeds the upper limit, microorganisms are killed and sludge decomposing ability is lowered, which is not preferable in some cases.

[0013] and the pH are different processes, there is a low pH process (the pH conditions and pH ₁₎ and high process (the pH conditions pH _2), the difference in pH between the two (= pH ₂ - p
H ₁ ) is within the above-mentioned pH value range, and is not particularly limited as long as the process proceeds from the lower pH to the higher pH, for example, stepwise increasing the pH. Any method may be used, or the pH may be raised in several steps. When increasing the pH steplessly, the rising speed may be constant or the rising speed may be arbitrarily changed. When increasing the pH stepwise, the number of steps is preferably 2 to 7 (more preferably 2).
~ 3). This is because the microbial activity decreases when the pH is suddenly changed. In the case of the stepwise method, the pH difference in each step is almost equal (for example, assuming that each pH in each step 1 to 3 is pH ₁ to pH ₃ ,
_2- pH ₁ ≈pH _3- pH ₂ ) is preferable, and the pH difference is preferably within 0.5 even if they are different. As described above, in the present invention, the pH is changed during the step of changing the pH.
Etc. do not substantially change (pH change is preferably 0.2
It is also preferable to provide a pH constant step (preferably 1 to 21 days, more preferably 3 to 7 days). This may help acclimatization.

In the present invention, the steps with different pH conditions need to be carried out from a low step to a high step over 1 to 63 days. It is preferably 3 to 30 days, more preferably 3 to 21 days. If it is less than the lower limit of the above numerical range, acclimation is insufficient and high efficiency resolution cannot be achieved, and if it exceeds the upper limit, the acclimation period is long and inefficient, which may not be preferable.

Either stepless or stepwise, or a combination of both, anyway, in the middle of the process,
Rapid pH rise is not preferable, preferably 1 pH / h
Within r (more preferably within 1 pH / day, more preferably within 0.5 pH / 7 days). However, even if the pH is sharply increased as described above, if the pH difference before and after that is within 1 (more preferably within 0.5), there is not much trouble.

Further, the pH may be temporarily lowered due to the convenience of administration, but in this case, it is preferable that the change in pH decrease is within 1.

Acclimation in the present invention is substantially synonymous with acclimation. In other words, it refers to adaptations that require organisms to take days to weeks to adapt to new environments. This is not a main cause of the appearance of mutant species, but is presumed to be mainly due to changes in gene expression morphology, reciprocal relations between various organisms, re-adjustment or reconstitution of abundance ratios, etc. Is. In the present invention, the sludge-degrading microorganisms are acclimated to the direction of exhibiting a high sludge-decomposing efficiency by the steps as described above.

In the present invention, the pH for acclimatization and sludge volume reduction treatment is preferably 8 or more in any step. pH
When it is 8 or more, sludge can be solubilized more efficiently than when only heating is performed. However, if the pH is too high, the cost of the chemical solution becomes high and the growth of microorganisms becomes difficult. Therefore, in the present invention, pH 8 to 12 is more preferable,
The pH of 8.5 to 10 is more preferable. The alkaline agent used for pH adjustment includes, for example, sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, sodium carbonate, sodium hydrogencarbonate, etc., and acid (decreases too high pH, Used when it is necessary to keep constant), hydrochloric acid, sulfuric acid, etc. The addition method is pH
It may be added in the solid state or in the state of an aqueous solution using a device having a control function. Among the above, it is preferable to use sodium hydroxide as the alkali agent and sulfuric acid as the acid from the viewpoint of economy.

In the acclimatization method of the present invention, it is preferable to perform aerobic microbial treatment. As the aerobic microbial treatment, a method of supplying oxygen to the treatment liquid by aeration and / or stirring is preferably used, but it is not particularly limited.

The microorganism used for acclimatization in the present invention is preferably under alkaline conditions (particularly preferably pH 8-12).
Range), more preferably a microorganism that can grow under alkaline conditions and at a temperature of 40 ° C. or higher. Microorganisms that are present by being added as main sludge-degrading microorganisms in the treatment apparatus are preferably microorganisms that belong to the genus Bacillus and have sludge degrading ability that can grow under the alkaline conditions and / or temperature conditions, and more preferably. Is the Bacillus sp. Q2-1 strain obtained by the present inventors (Biotechnology Research Institute, No. 16922),
It is Bacillus sp. Q3 strain (Biotechnology Research Institute No. 16923).

The temperature condition during acclimatization of sludge in the present invention is 20 to 80 ° C. However, the temperature is preferably 40 ° C. or higher and 70 ° C. or lower in view of the effect of promoting solubilization of sludge by heat, growth inhibition of microorganisms not contributing to decomposition and preferential growth of microorganisms involved in sludge decomposition, and energy cost required for heating, It is more preferably 45 ° C. or higher and 65 ° C. or lower.
However, it may be set according to the properties of microorganisms that contribute to sludge decomposition.

The apparatus for acclimatizing sludge in the present invention is basically proposed by the present inventors in Japanese Unexamined Patent Publication No. 11-33.
573, which is an aeration tank having equipment for supplying an acid and an alkaline agent to maintain a constant pH, and having a device for supplying air or oxygen, and further added to the aeration tank. There is no particular limitation as long as it is equipped with a temperature and / or heat retention facility. Depending on the fermentation heat of the sludge itself and the residual heat in the sludge generation process, heat retention may be sufficient without heating. The treatment method may be a batch method, but a continuous method is preferable because of its high efficiency.

As described above, the microorganism group acclimated by the method of the present invention can be used as it is for the sludge volume reduction treatment. P which was finally prepared by acclimatization treatment
The sludge volume reduction treatment can be performed under the same conditions as in the acclimation treatment, except that H is kept substantially constant. Also, on the experimental scale, the pH increasing process is tried under the same conditions as the sludge volume reduction except that the scale and pH are sequentially increased, and the optimum process that maximizes the solubilization rate or decomposition rate of the sludge. In consideration of the pH, it is preferable to set the final adjusted pH of the acclimatization treatment to the optimum treatment pH and the pH during the sludge volume reduction steady operation to the optimum treatment pH in the actual scale.

[0024]

EXAMPLES Specific examples of the present invention will be shown below. In addition,
The present invention is not limited to this.

The solubilization rate of sludge was expressed as a percentage of the decrease in the solid content concentration before and after the treatment with respect to the solid content concentration before the treatment. That is, it is as the following formula.

L = (S ₁ -S ₀ ) / S ₀ * 100 S ₀ : Solid content concentration before treatment (g / l) S ₁ : Solid content concentration after treatment (g / l) L: Solubilization rate (%) The solid content concentration S (g / l) of the sludge is a constant volume V
The sludge liquor of (l) was centrifuged at an acceleration rate of 3000 G for 3 minutes, the obtained precipitate portion was washed once and then centrifuged again to dry the precipitate at 105 ° C., and then the solid content dry weight was weighed. Calculated from (g). That is, it is as the following formula.

S = W / V V: Volume of sludge liquid (l) W: Dry weight of solid content (g) S: Solid content concentration (g / l) The decomposition rate of sludge is the total organic carbon concentration before treatment. The decrease in total organic carbon concentration before and after the treatment was expressed as a percentage. That is, it is as the following formula.

D = (T ₁ -T ₀ ) / T ₀ * 100 T ₀ : Total organic carbon concentration before treatment (g / l) T ₁ : Total organic carbon concentration after treatment (g / l) D: Decomposition Rate (%) Example 1 Microorganisms having sludge-decomposing ability in a treatment tank having a volume of 2 liters, which was prepared by treating excess sludge collected from a chemical plant wastewater treatment facility with water to a solid content concentration of 20 g / l as a liquid to be treated. 1 liter of the liquid to be treated was added in advance, and the liquid to be treated was supplied to the treatment tank at a rate of 1000 ml / day to perform aerobic treatment at 45 ° C. while keeping the pH constant. Further, a portion of the sludge liquid in the treatment tank exceeding 1 liter was made to overflow to the outside of the tank. The pH to be controlled was set to 8.8, and then the pH was controlled to 9.0, 9.2, and 9.4 in order, and the sludge volume reduction treatment was performed. After the solubilization rate and decomposition rate were investigated by continuing the treatment under one pH condition for about 1 week, the treatment was carried out by the method of shifting to the next pH condition (transition time was about several minutes). 28 at pH 8.8
%, 29% at pH 9.0 and 37% at pH 9.2. Decomposition rate is 16% at pH 8.8 and 18 at pH 9.0
%, And 20% at pH 9.2. In addition, pH 9.4
, The solubilization rate was 34% and the decomposition rate was 18%, and the optimum treatment pH was judged to be 9.2 from these.

Comparative Example 1 The treatment was carried out in the same manner as in Example 1 except that the optimum treatment pH 9.2 found in Example 1 was constantly controlled, and the solubilization rate and decomposition rate were examined. As a result of treatment for about 3 weeks, the solubilization rate was 31% and the decomposition rate was 18%. After reaching these values within one week, there was no indication of any further increase.

As is clear from the examples, by providing steps having different pH conditions and performing these steps in order from steps having low pH to steps having high pH, microorganisms involved in sludge volume reduction can be efficiently carried out. You can see that you can acclimate and perform the sludge volume reduction treatment with high efficiency.

[0031]

INDUSTRIAL APPLICABILITY The present invention is carried out under alkaline conditions and at 40 ° C.
In sludge volume reduction treatment using microorganisms that have sludge decomposing ability at the above temperatures, steps with different pH conditions are provided, and these steps are performed in order from steps with low pH to steps with high pH to efficiently reduce sludge volume. By acclimatizing the microorganisms involved in conversion, it is possible to provide a sludge volume reduction treatment method having excellent economical efficiency.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C12N 1/36 C12N 1/36 // (C12N 1/00 C12R 1:07 C12R 1:07) (C12N 1 / 20 C12R 1:07) (C12N 1/36 C12R 1:07) F term (reference) 4B065 AA15X AA99X AC04 BC02 BC06 BC18 BC24 BD14 CA55 4D059 AA05 BA01 BA22 BA28

Claims (6)

[Claims] 1. When performing sludge volume reduction treatment under alkaline conditions and at 20 to 80 ° C., the pH condition is 0.1 to 0.1.
A method for acclimatizing a microorganism group involved in sludge volume reduction, which comprises providing 5 different steps and performing these steps from a step having a low pH to a step having a high pH over 1 to 63 days. 2. The method for acclimatizing a group of microorganisms involved in sludge volume reduction according to claim 1, wherein the acclimatization pH is 8 or more. 3. The method for acclimatizing a group of microorganisms involved in sludge volume reduction according to claim 1 or 2, wherein microorganisms having sludge decomposing ability under alkaline, medium and high temperature conditions are present. 4. The method according to claim 1, which is performed under aerobic conditions.
4. The acclimatization method of a microorganism group involved in sludge volume reduction according to any one of 3). 5. The method for acclimatizing a microorganism group involved in sludge volume reduction according to claim 1, wherein a microorganism belonging to the genus Bacillus having sludge decomposing ability is present. 6. A sludge volume reduction treatment method using the method for acclimatizing a microbial group for sludge volume reduction according to any one of claims 1 to 5.