JP2007061702A - Sludge weight reduction method using activated sludge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sludge weight reduction method which has a high effect of inhibiting generation of sludge, and can be introduced to an existing wastewater treatment facility at a low cost. <P>SOLUTION: To a system of an activated sludge group (B) generating surplus sludge, an activated sludge group (A) having an autolysis rate higher than the activated sludge group (B) is added. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for reducing sludge containing organic matter generated from various wastewater treatment facilities, and more particularly to a sludge reduction method for suppressing the generation of excess sludge by adding activated sludge having different properties. .

In general, a treatment system that uses living organisms (bacteria) is employed to treat wastewater containing organic substances. In the treatment method using this organism, a large amount of excess sludge is generated.
Currently, Japan is comprehensively promoting waste reduction and recycling with the aim of creating a recycling-oriented society. Among these wastes, the ratio of organic and inorganic sludge is high, and about 70% of the sludge is organic sludge. Regarding recycling and recycling of organic sludge, composting and composting have begun to be considered a little at public wastewater treatment facilities and major offices, but little is done at small-scale facilities. However, waste landfills nationwide have less capacity to accept and new locations are difficult, and sludge treatment costs are increasing year by year. Development of a system that can control sludge generation easily and inexpensively. Is desired.

  In such wastewater treatment facilities that generate a large amount of organic sludge, development of sludge generation suppression technology and reduction technology has been carried out. Examples thereof include a biological method to be introduced into the treatment tank and a method in which a part of the generated sludge is solubilized by a physicochemical method, and the obtained solution is returned to the biological treatment tank and biologically treated. As the former method, utilization of microorganisms and utilization of Bacillus subtilis and photosynthetic bacteria using secretory enzymes have been empirically performed. Moreover, in recent years, a sludge reduction method using microorganisms developed from swine urine treatment (see Patent Document 1) has been proposed, and a sludge reduction system using thermophilic bacteria (see Patent Document 2) has been proposed. Yes. In addition, as the latter method, as a method of destroying biological cells in sludge by a physicochemical method and reducing sludge, mill method (see Patent Documents 3 to 5), ozone method (Patent Documents 6 to 6). 9), an ultrasonic method (see Patent Documents 10 and 11), a water jet method (see Patent Documents 12 to 14), and the like.

  However, although any technique can reduce the sludge generation rate to 10 to 20% of the conventional technology, it has hardly been put into practical use. In the case of biological methods, there is a problem that even if reduced bacteria are added to the biological treatment tank in the wastewater treatment facility, the microflora in the tank does not fluctuate very much, or it is not prioritized even if continuously added. This is because the actual effect is not clear. Furthermore, solid components typified by cellulose components such as paper are difficult to decompose in biological treatment tanks and difficult to reduce in weight.

On the other hand, in the case of physicochemical treatment methods such as the mill method, the ozone method, and the ultrasonic method, there is a problem that the apparatus is generally expensive and it is difficult to implement from the viewpoint of cost. In addition, the mill method for solubilizing sludge by friction between beads and sludge has a problem that the sludge slurry has a finer efficiency, but the solubilization rate is low and it is difficult to increase the size of the apparatus. In addition, the ozone method, which is a kind of accelerated oxidation method, is highly useful because it can easily decompose not only sludge but also difficult-to-decompose substances, but the ozone generator is expensive and the waste ozone treatment device. There is another problem that is necessary. In addition, the ultrasonic method is high in both the sludge refinement rate and the solubilization rate, but the equipment is extremely expensive, and measures against heat and sound due to ultrasonic waves are also required. The water jet method is a method in which the sludge slurry is brought into a high pressure state and then blown into the water through a nozzle and broken by cavitation caused by the pressure difference at that time. Since the solubilization rate depends on the amount of cavitation, a high-power pump is required for effective sludge crushing.
Thus, each sludge generation suppression technology and weight reduction technology have advantages and disadvantages, and development of more innovative technologies is expected.

JP-A-9-245 JP-A-9-234060 JP-A-11-300393 JP 2000-167597 A JP 2000-325983 A JP-A-9-234497 JP-A-11-90496 JP 2001-259678 A JP 2001-327998 A JP 2002-361281 A JP 2003-200198 A JP 2001-212599 A JP 2001-314877 A JP 2003-10890 A

  The present invention was developed on the basis of such a situation, and an object thereof is to provide a sludge reduction method that is highly effective in suppressing the generation of sludge and can be introduced into existing wastewater treatment facilities at low cost. Is.

  As a result of various studies to achieve the above object, the present inventors have added surplus sludge by adding activated sludge having different properties to a biological treatment tank (aeration tank) of a wastewater treatment facility where surplus sludge is generated. It was found that the generation of sludge can be suppressed.

  This invention was made | formed based on the said knowledge, and the activated sludge group (A) whose self-digestion rate is faster than the activated sludge group (B) to the system of the activated sludge group (B) which has generated excess sludge. The present invention provides a method for reducing sludge, characterized by adding

The sludge reduction method of the present invention is a very simple method of adding another activated sludge group (A) having a high self-digestion rate to a biological treatment tank (aeration tank) of a wastewater treatment facility where excess sludge is generated. The operation can suppress the generation of surplus sludge, and is an inexpensive system and economical compared to conventional chemical and physical methods. The burden on wastewater treatment can be reduced, and economic effects can be expected. In addition, it can be easily applied to any existing wastewater treatment facility as long as it is a wastewater treatment facility using a living organism.
The activated sludge group (A) is a completely safe substance existing in nature, and is safer than the conventional chemical treatment method. Furthermore, it can be carried out under general temperature conditions (20 ° C. to 35 ° C.) in the natural world, and operations such as heating are unnecessary.

Hereinafter, the sludge reduction method of this invention is explained in full detail about the preferable embodiment.
The sludge reduction method of the present invention can be applied to any wastewater treatment facility as long as it is a wastewater treatment facility using a living organism. For example, the wastewater treatment facility of a business establishment merger septic tank, a wastewater treatment facility of a fishery processing establishment, a food It can be suitably applied to factory wastewater treatment facilities, meat processing plant wastewater treatment facilities, livestock breeding plant wastewater treatment facilities, agricultural settlement wastewater treatment facilities, domestic wastewater treatment facilities, and the like.
The activated sludge group (B) in the present invention is an activated sludge group that generates excess sludge in the wastewater treatment facility.

The activated sludge group (A) added to the activated sludge group (B) is an activated sludge group of a wastewater treatment facility different from the activated sludge group (B), and the self-digestion rate is the activated sludge. It is faster than the autolysis rate of group (B).
The activated sludge group (A) preferably has a self-digestion rate of 150 mg / l · day or more, more preferably 200 to 300 mg / l · day faster than the self-digestion rate of the activated sludge group (B). It is.
The self-digestion rate of the activated sludge group (A) is preferably 300 mg / l · day or more, more preferably 400 mg / l · day or more, and further preferably 500 mg / l · day or more.

The self-digestion rate is a value determined as follows.
A sample (activated sludge) is charged, and the air obtained through a 0.2 μm filter is fed and aerated in the state without adding organic substances as nutrients, promoting self-digestion (endogenous respiration and auto-oxidation). The suspended substance concentration in the sample is measured for 5 days, and the value obtained by quantifying the gradient of the concentration change as the slope coefficient is the self-digestion rate.
That is, the self-digestion rate (mg / l · day) = − (suspended substance concentration in initial sample−suspended substance concentration in sample after 5 days) ÷ 5.
An example of the activated sludge group (A) is shown in FIG. 1, and an example of the activated sludge group (B) is shown in FIG. As shown in FIGS. 1 and 2, activated sludge having a large suspended substance concentration change up to 5 days after self-digestion is the activated sludge group (A), and activated sludge having a small change is the activated sludge group (B). .

  In addition, when measuring the self-digestion rate of activated sludge that has already been adjusted as concentrated sludge by self-digesting activated sludge collected from certain types of wastewater treatment facilities, self-digestion proceeds and the correct value is obtained. Therefore, it is necessary to feed the food containing organic substance and perform the breeding operation to make it active, and after confirming the stable state, it is necessary to remove the organic substance, aerate, and measure the self-digestion rate. is there. The bait is added at a ratio of 1 part by mass of an organic substance and 8 parts by mass of water with respect to 1 part by mass of concentrated sludge, and is allowed to grow in a temperature range of 25 to 35 ° C.

  The addition amount of the activated sludge group (A) is preferably 4 to 100% by mass, more preferably 6 to 40% by mass with respect to the activated sludge group (B). The sludge reduction effect can be controlled by the addition amount of the activated sludge group (A).

The method for adding the activated sludge group (A) is not limited. For example, a predetermined amount of the activated sludge group (A) is directly charged into the biological treatment tank occupied by the activated sludge group (B). The activated sludge group (A) can be stored in a separate storage tank, and the activated sludge group (A) can be gradually added to the biological treatment tank occupied by the activated sludge group (B). .
Also, the activated sludge group (A) is put into a separate storage tank, and a part of the activated sludge group (B) is taken out and mixed, and the mixed activated sludge group (A + B) is gradually added. The method of adding to the biological treatment tank occupied by the activated sludge group (B) is also an efficient and desirable method as a condition for exerting the sludge reducing ability of the mixed sludge group.

  In the present invention, it is only necessary to add the activated sludge group (A) to the system of the activated sludge group (B), and both the activated sludge group (A) and the activated sludge group (B) exist in nature. Therefore, if the temperature is normal temperature and the pH is a condition under which normal biological treatment is performed, it is possible to cope with it, and in carrying out the present invention, preparing a special environment with temperature, pH, etc. It is unnecessary.

  EXAMPLES Next, examples are given to describe the present invention more specifically, but the present invention is not limited to the following examples.

Example 1
As the activated sludge groups (A) and (B), the activated sludge group of 412 mg / l · day and the activated sludge group of 164 mg / l · day shown in FIG. 3 were used. These activated sludge groups are mixed in the same amount, aerated with air, the initial suspended solids concentration condition is adjusted to 4,000 mg / l, and the suspended sludge concentration of the activated sludge group (A + B) mixed system is adjusted. Changes were measured. The result is shown in FIG. In FIG. 4, 1 is a graph showing the change in suspended solids concentration of the activated sludge group (A + B) mixed system, 2 is the activated sludge group (A) alone system, and 3 is the activated sludge group (B) alone system. It is a graph which shows the change of each suspended matter density | concentration in the case of. 4 shows the change in suspended solids concentration expected when the activated sludge group (A) and the activated sludge group (B) are mixed. The activated sludge group (A) alone system and the activated sludge group (B) alone It is a graph which shows an average value with the case of a system.
Moreover, the graph which shows the change of the suspended-substance density | concentration of each activated sludge group shown in FIG. 4 by the suspended-substance weight loss rate defined below is shown in FIG. In FIG. 5, 1 is an activated sludge group (A + B) mixed system, 2 is an activated sludge group (A) alone system, 3 is an activated sludge group (B) alone system, It is a graph which shows the average value in the case of activated sludge group (A) independent system, and the case of activated sludge group (B) independent system.
Suspended material weight loss after N days (%) = [(SS1-SSN) / SS1] × 100
However, SS1 is the suspended matter concentration (mg / l) after 1 day, and SSN is the suspended matter concentration (mg / l) after N days.

Example 2
As the activated sludge group (B), the change in suspended solids concentration was measured in the same manner as in Example 1 except that the activated sludge group shown in FIG. The weight loss rate was determined. The result is shown in FIG. In FIG. 6, 5 is an activated sludge group (A + B) mixed system, 6 is an activated sludge group (A) single system, and 7 is an activated sludge group (B) single system. It is a graph which shows the average value in the case of activated sludge group (A) independent system, and the case of activated sludge group (B) independent system.

Example 3
As the activated sludge group (A), the change in the suspended solids concentration was measured in the same manner as in Example 1 except that the activated sludge group shown in FIG. The weight loss rate was determined. The result is shown in FIG. In FIG. 7, 9 is an activated sludge group (A + B) mixed system, 10 is an activated sludge group (A) single system, 11 is an activated sludge group (B) single system, respectively. It is a graph which shows the average value in the case of activated sludge group (A) independent system, and the case of activated sludge group (B) independent system.

Example 4
As the activated sludge group (A), the self-digestion rate 367 mg / l · day activated sludge group shown in FIG. 1 is used, and as the activated sludge group (B), the self-digestion rate 127 mg / l · day activated sludge shown in FIG. Except for using the group, the change in suspended solid concentration was measured in the same manner as in Example 1 to determine the suspended solid weight loss rate. The result is shown in FIG. In FIG. 8, 13 is an activated sludge group (A + B) mixed system, 14 is an activated sludge group (A) single system, and 15 is an activated sludge group (B) single system. It is a graph which shows the average value in the case of activated sludge group (A) independent system, and the case of activated sludge group (B) independent system.

  As can be seen from Examples 1 to 4 above, in the case of the activated sludge group (A + B) mixed system of the present invention, the effect expected when the activated sludge group (A) and the activated sludge group (B) are mixed. Has an effect that exceeds.

Example 5
The present embodiment shows a case where the present invention is applied to an existing wastewater treatment facility in food processing.
The existing wastewater treatment facility has a high inflow raw water BOD value of 500 to 800 mg / l, and the surplus sludge generation rate is 35 to 40% of the BOD load. Moreover, the self-digestion rate of the activated sludge group [activated sludge group (B)] of this treatment facility is 106 mg / l · day. 1% of the activated sludge group shown in FIG. 1 as the activated sludge group (A) is added to this treatment facility with respect to the activated sludge group (B). The suspended matter concentration of was continuously measured. The result is shown in FIG.
As can be seen from FIG. 9, the suspended solid concentration initially decreased to 2,500 to 3,000 mg / l, but after that, it stabilized at 4,000 mg / l in about 2 months and remained stable for 4 months. Is maintained. Since the suspended solids concentration is stable, excess sludge was not extracted.
As a result, it was confirmed that the generation of excess sludge can be suppressed by adding the activated sludge group (A) having a high self-digestion rate to the activated sludge group (B) having a low self-digestion rate.

Example 6
As the activated sludge group (A), the activated sludge group having a self-digestion rate of 572 mg / l · day shown in FIG. 1 is used. As the activated sludge group (B), the activated sludge having a self-digestion rate of 164 mg / l · day shown in FIG. Using the group, 15% methanol aqueous solution and nutrients were added as organic substances to the single system and mixed system of the above activated sludge group, and the change in BOD concentration was measured. The result is shown in FIG. In FIG. 10, 17 is an activated sludge group (A + B) mixed system, 18 is an activated sludge group (A) single system, and 19 is an activated sludge group (B) single system. Moreover, in FIG. 10, 20 is a graph which shows the BOD accumulation density | concentration of the added organic substance.
As can be seen from FIG. 10, the BOD treatment capacity of the activated sludge group (A + B) mixed system is as follows: the activated sludge group (A) alone system having a high self-digestion rate, and the activated sludge group (B) alone system having a low self-digestion rate. It is surprising that the activated sludge group (A + B) mixed system can suppress the generation of surplus sludge, despite the fact that it shows a common sense additivity.

It is a graph which shows the basic state of the self-digestion rate of the activated sludge group used as activated sludge group (A) by this invention. It is a graph which shows the basic state of the self-digestion rate of the activated sludge group used as activated sludge group (B) by this invention. It is a graph which shows the basic state of the self-digestion rate of the activated sludge group used in Example 1. 2 is a graph showing changes in suspended solid concentration of activated sludge groups measured in Example 1. FIG. 2 is a graph showing changes in the suspended solid weight loss rate of the activated sludge group measured in Example 1. FIG. 6 is a graph showing changes in the suspended solid weight loss rate of the activated sludge group measured in Example 2. FIG. 6 is a graph showing changes in the suspended solid weight loss rate of the activated sludge group measured in Example 3. FIG. It is a graph which shows the change of the suspended solid weight loss rate of the activated sludge group measured in Example 4. It is a graph which shows the change of the suspended solid concentration in the aeration tank in Example 5. 6 is a graph showing changes in the BOD concentration of each activated sludge group measured in Example 6.

Claims (5)

  An activated sludge group (A) having a higher self-digestion rate than the activated sludge group (B) is added to the system of the activated sludge group (B) generating surplus sludge.   The sludge reduction method according to claim 1, wherein the self-digestion rate of the activated sludge group (A) is 300 mg / l · day or more.   The sludge reduction method according to claim 1 or 2, wherein the self-digestion rate of the activated sludge group (A) is 150 mg / l · day or more faster than the self-digestion rate of the activated sludge group (B).   The sludge reduction method according to any one of claims 1 to 3, wherein the amount of the activated sludge group (A) added is 4 to 100 mass% with respect to the activated sludge group (B). The above-mentioned activated sludge group (B) consists of a combined septic tank at a business establishment, a wastewater treatment facility at a fishery processing plant, a wastewater treatment facility at a food factory, a wastewater treatment facility at a meat processing plant, a wastewater treatment facility at a livestock breeding plant, and an agricultural settlement drainage The sludge reduction method according to any one of claims 1 to 4, which is an activated sludge group in a treatment facility or a domestic wastewater treatment facility.

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