JPH0521638B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is an inexpensive and harmless sludge that contains organic matter and has a high water content, such as human waste, septic tank sludge, community treatment sludge (Comipura sludge), and sewage sludge. The present invention relates to a method for treating organic sludge that undergoes chemical treatment, and more specifically, it relates to an ultra-low dilution treatment method that can render filtrate (sludge) containing organic matter harmless through biological treatment without requiring much dilution water. .

(Prior art) As a conventional example of detoxifying sludge containing organic matter and having a high moisture content, for example, as shown in Japanese Patent Application Laid-open No. 153600/1983, a method is used in which contaminants are removed from raw sludge and then treated. There is a method in which pneumatic or anaerobic digestion is performed, and the sludge generated by this treatment (biological treatment) is incinerated together with the impurities.

However, when raw sludge is subjected to biological treatment in its almost unchanged state as described above, it is necessary to dilute the raw sludge with a large amount of water, and at the same time, the amount of surplus sludge generated by biological treatment is large. or,
It is needless to mention in detail that as the population increases, the amount of human waste, sewage sludge, etc. discharged as a result of residents' daily lives increases year by year.

Therefore, for example, local governments in areas where the population is rapidly increasing are making maximum efforts to construct sludge treatment systems, but the conventional method of diluting raw sludge with water and then biologically treating it is very difficult. There is a need to construct a biological treatment facility with a large capacity, or there is a need to secure dilution water that increases with the increase in sludge, and a huge amount of fuel costs are required to incinerate a large amount of excess sludge. , there are problems such as a sharp increase in economic burden.

In addition, when incinerating excess sludge and disposing of it in a landfill to reduce fuel costs, there are also disadvantages such as the need to prepare a vast landfill site.

(Problem to be solved by the invention) The problem to be solved by the present invention is to solve the above-mentioned problems by providing a new method for treating organic sludge that is responsive to the times. be.

(Means for solving the problem) Means for solving the problem in the present invention are as follows:
After the raw sludge with a high moisture content containing organic matter is subjected to sedimentation treatment, the solids contained in this raw sludge are crushed to remove impurities, and the surplus sludge is mixed with the raw sludge from which the impurities have been removed and aerated and agitated. After that, there is a concentration step in which a part of the water is removed from this mixed sludge to make it concentrated and homogenized, and highly flammable organic materials such as rice husk and bark are added to the mixed sludge that has been concentrated and homogenized in the concentration step. A dehydration step in which an auxiliary material is mixed and the sludge mixed with the auxiliary material is compressed and dehydrated to solidify it, and the filtrate produced in the concentration step and the dehydration step is biologically treated to produce effluent water and the raw material. a filtrate treatment step in which the sludge is separated from surplus sludge mixed with the sludge, the impurities removed in the concentration step and the solids obtained in the dehydration step are finally treated, and the effluent generated in the filtrate treatment step is treated. This is characterized in that the excess sludge is discharged and, after being concentrated, is returned to the concentration step.

(Function) After the raw sludge is treated with sand, the solids contained in the raw sludge are crushed and impurities are removed. Damage to the pump can be reduced. Further, since the foreign matter contained in the raw sludge that has been subjected to the sand settling treatment is crushed and removed, the foreign matter can be efficiently removed.

Furthermore, surplus sludge is mixed with the raw sludge from which impurities have been removed, and this is aerated and stirred, and then a portion of the water is removed from this mixed sludge, concentrated and homogenized, and an auxiliary material is mixed into this sludge. Since compression dewatering is performed, the efficiency of removing solids from the sludge is increased.

On the other hand, since solid organic matter is removed mechanically from the filtrate to be biologically treated,
The amount of dilution water required for biological treatment is significantly reduced. In addition, since highly combustible organic auxiliaries are mixed into the concentrated and homogenized mixed sludge and then compressed and dehydrated, the final dewatering efficiency is high and the dewatered water is Since the auxiliary materials mixed in the solids can be effectively used as combustion improvers, or they can be composted as is, there is no need to separate and recover or detoxify the auxiliary materials at the final processing stage. do not have.

Furthermore, since the surplus sludge produced in the biological treatment process is concentrated, returned to the concentrated and fixed state and mixed with the raw sludge, the amount of surplus sludge returned to the concentration process can be reduced.

(Example) Fig. 1 is a block diagram showing the sludge treatment process according to the present invention, and Fig. 2 is a schematic configuration diagram of the entire apparatus showing the embodiment of the present invention. The structure and operation will be explained.

First, in the concentration means for realizing the concentration step A, raw sludge is sent by a pump (not shown) from a receiving tank 2 equipped with a settling tank 1 for removing sand, etc. contained in raw sludge such as human waste, septic tank sludge, Comiplast sludge, etc. The crusher 3 crushes the solids contained in the raw sludge. Incidentally, impurities contained in the raw sludge flowing out from the crusher 3 through the receiving tank 4 are separated as sludge by a drum screen (drum type gravity dehydrator) 5, dehydrated by a press 6, and then incinerated. Ru.

The raw sludge flowing out from the drum screen 5 through the receiving tank 7 is sent to the mixed sludge storage tank 8 together with excess sludge taken out from the filtrate processing means described later. In this mixed sludge storage tank 8, raw sludge and excess sludge are sufficiently stirred by blower aeration to form mixed sludge with a concentration of, for example, 1.7 to 1.8%. The water (filtrate) is separated and concentrated until the sludge concentration is, for example, 8%.

It should be noted that flocculant cations are added to the drum screen 9 from the chemical tank 10 as needed to increase the efficiency of concentration, but the concentration is carried out by changing the addition rate of the flocculant cations depending on the concentration of the mixed sludge. The concentration of sludge is maintained at a predetermined value, for example 8%.

On the other hand, in the dehydration means embodying the dehydration step B,
The sludge concentrated as described above is stored in a mixing tank 11, and is drawn out at a predetermined flow rate per unit time by a mono pump (not shown), and mixed with flocculant cations supplied from a chemical tank 10 in a primary blender 12. do. Then the secondary blender 1
In Step 3, the sludge is mixed with an auxiliary material and subjected to gravity/pressure dewatering for, for example, 10 minutes using a net conveyor (conveyor type gravity dehydrator) 14.

This dewatering reduces the water content of the sludge to, for example, about 70%. In addition, as auxiliary materials, highly flammable, non-polluting, and low-cost organic materials such as rice husk and bark are used, but the type and amount of flocculant and auxiliary materials to be added may be adjusted depending on the final treatment. Just adjust it.

The sludge dewatered by the net conveyor 14 as described above is supplied to a two-barrel caterpillar press (squeezing/dewatering machine) 15, where the sludge is compressed and dehydrated for, for example, 30 minutes and solidified (caked). The moisture content of the solid material obtained in this way is, for example, 55 to 58%, but the dehydration treatment differs depending on the selection of the auxiliary material.

In other words, when using an auxiliary material such as rice husk, which has large particles and is elastic, a gap is created between the sludge and the auxiliary material, which allows water to be drained easily and allows a large amount of sludge to be supplied. High dehydration efficiency. On the other hand, when using an auxiliary material such as bark, which has small particles but burns a high amount of calories, the gap between the sludge and the auxiliary material is small, and the dewatering efficiency is low due to the small amount of elasticity. The type and amount of additives should be adjusted appropriately depending on the characteristics of dewatering and subsequent processing or the sludge, such as when incinerating solidified sludge after drying because the combustion calories are high. You can select .

The filtrate treatment means for biologically treating the filtrate produced by carrying out the concentration step A and the dehydration step B is provided with a storage aeration tank 16 as in the case of conventionally known biological treatment means. The filtrate sent to the storage aeration tank 16 is a filtrate from which solids have been previously recovered (separated) by subjecting the sludge to raw dehydration treatment.

Therefore, even though the BOD of the mixed sludge is 17,000 ppm, the filtrate sent to the storage aeration tank 16 is
The average BOD was about 800 ppm.

In the storage aeration tank 16, the filtrate and wastewater from the site are sufficiently stirred, and then passed through the measuring tank 17 to the first aeration tank 18.
sent to. Note that well water is supplied to this first aeration tank 18 as dilution water.

In addition, the filtrate is transferred from the first aeration tank 18 to the primary concentration tank 1.
9 and a second aeration tank 20 to an activation tank 21, and well water is also supplied to this activation tank 21 as dilution water.

MLSS of activation tank 21 is 1600 to 2200 on average for 4 tanks
mg/, and the MLSS of reaeration tank 22 is
It is 7000mg/. The SV is connected to the surplus sludge thickening tank 24 by a predetermined amount from the final settling tank 23 so that the average of the four tanks in the activation tank 21 is 17 to 30%, but a predetermined amount (3 m ³ / By drawing out the excess sludge (days) to the excess sludge thickening tank 24 and returning a considerable amount (293 m ³ /day) of sludge from the final settling tank 23 to the reaeration tank 22, The amount of excess sludge returned to the thickening means is reduced.

Since the amount of solids in the filtrate is small, it is sufficient to draw out about 3 m ³ of excess sludge from the primary thickening tank 19 to the mixed sludge aeration tank 8 once every three days, thereby improving management efficiency.

Incidentally, the power consumption required to process 172K of mixed sludge per day is 1296KWH, and the final settling tank 2
The amount of sludge extracted from 3 is 26K, the amount of concentrated surplus sludge is 12K, the amount of returned sludge is ^293m3 , the amount of dilution water used is ^293m3 , and the primary aeration air volume is ^8.36m3 /min.
Secondary aeration air volume is 10.0m ³ /min, mixed sludge pH is 7.7
The pH of the filtrate was 8.2.

In addition, the average SV of the activation tank 21 was 19%, the PH was 7.7, the water temperature was 21.0°C, and the MLSS was 1800 mg/, and the SV of the reaeration tank 22 was 83%. The final settling tank 23
PH was 7.7, transparency was 30cm, DO was 1.2mg/, and water temperature was 21.5℃.

On the other hand, the pH of the coagulation sedimentation tank 25, which is directly related to the quality of the effluent water, is 7.8, the visibility is 30 cm, the water temperature is 21.5°C, and the residual chlorine contained in the effluent water is 0.3 mg/.
Hypochlorite was 180 kg/day.

The treatment of the sludge that has been solidified through dewatering is optional. For example, when using it as fuel, the highly flammable organic auxiliary material mixed in during compressed dehydration functions as a combustion auxiliary material and increases the combustion of the sludge. There is no need to use supplemental fuel to facilitate this. Further, when solidified sludge is used as a raw material for compost, the mixed auxiliary materials are composted as they are. Therefore, in any case, there is no need to detoxify the auxiliary material after the fact, and an increase in processing costs can be avoided.

(Effects of the Invention) The present invention is characterized in that after the raw sludge is subjected to sedimentation treatment, the solid matter contained in the raw sludge is crushed to remove impurities, and the raw sludge from which the impurities have been removed is treated with surplus generated within the site. The sludge is concentrated and mixed, the mixed sludge is aerated and stirred, a part of the water is removed, it is concentrated and homogenized, auxiliary materials are mixed in, and then the final treatment is carried out by dewatering and solidifying. Since the filtrate produced by concentration and solidification, that is, the filtrate from which the solid content has been removed, is subjected to biological treatment, the amount of dilution water can be reduced, and the load on the filtrate treatment means can be significantly reduced. The entire structure can be downsized.

In addition, in the present invention, surplus sludge discharged from a filtrate treatment facility is concentrated and then mixed with raw sludge and processed again, so a large amount of surplus sludge is not generated. There is no need for incineration costs or the need to prepare a vast final treatment facility, and the economic burden can be significantly reduced.

Furthermore, in the present invention, highly flammable organic auxiliaries such as rice hulls and bark are mixed into the mixed sludge when it is compressed and dehydrated to solidify it, so that the dewatering effect of the mixed sludge can be enhanced, Solidified sludge can be efficiently combusted through the auxiliary action of auxiliary materials, or when solidified sludge is composted, the auxiliary materials can be composted as is, so the auxiliary materials can be separated and recovered after the fact. Or, it is not necessary to perform detoxification treatment.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a sludge treatment process according to the present invention, and FIG. 2 is a schematic diagram of the entire apparatus showing an embodiment of the present invention. A...Concentration process, B...Dehydration process, C...Filtrate treatment process, 1...Sand settling tank, 2...Receiving tank, 3...
Crusher, 4...Receiving tank, 5...Drum screen,
6... S press, 7... Receiving tank, 8... Mixed sludge storage tank, 9... Drum screen, 10... Chemical tank, 11... Mixing tank, 12... Primary blender, 13... Secondary blender , 14...Net conveyor, 15...Double type caterpillar press, 16
...Storage aeration tank, 17...Measuring tank, 18...First aeration tank, 19...Primary concentration tank, 20...Second aeration tank, 21...Activation tank, 22...Reaeration tank, 23...
...Final settling tank, 24... Surplus sludge thickening tank, 25...
...Flocculation sedimentation tank.

Claims (1)

[Claims] 1 After the raw sludge with a high moisture content containing organic matter is subjected to sedimentation treatment, the solids contained in this raw sludge are crushed to remove impurities, and the surplus sludge is mixed with the raw sludge from which the impurities have been removed and aerated. After stirring, a part of the moisture is removed from the mixed sludge to make it concentrated and homogenized, and the mixed sludge is mixed with highly flammable organic materials such as rice husk and bark. a dehydration step of mixing an auxiliary material and compressing and dewatering the sludge mixed with the auxiliary material to solidify it;
a filtrate treatment step in which the filtrate produced in the concentration step and the dehydration step is subjected to biological treatment and separated into effluent water and excess sludge mixed with the raw sludge, the impurities removed in the concentration step and the dewatering step; Ultra-low dilution of organic sludge, characterized in that the solid matter obtained in the process is finally treated, the effluent water generated in the filtrate treatment process is discharged, and the surplus sludge is concentrated and then returned to the concentration process. Processing method.