JPH08192197A - Method and device for treating sludge using ozone - Google Patents

Abstract

PURPOSE: To efficiently treat sludge with ozone before concentrating the sludge using pH as an index. CONSTITUTION: A sludge feed pump 8 is driven using a controller 6 to feed sludge into a contact tank 1 and ON signal is outputted from the controller 6 to an ozone generator 4 to generate ozone gas, and the ozone gas is fed into the sludge from a diffuser pipe 2 provided at the bottom of the tank 1 so as to be agitated by an agitation device, thereby the ozone gas comes into contact with the sludge to effect ozone processing. When the sludge is subjected to ozone processing, it is sterilized and the value of pH changes. A pH meter 5 is provided in the tank 1 and when pH value or a change in pH value of the meter 5 has reached a set value, the controller 6 outputs OFF signal to the ozone generator 4 to stop generation of ozone. Consequently, ozone processing can be achieved economically.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sludge ozone treatment method and apparatus in a sludge treatment system having a device for ozone treatment of sludge.

[0002]

2. Description of the Related Art In a sludge treatment facility, as shown in FIG.
The sludge is finally disposed of after undergoing treatments such as concentration, digestion and dehydration. Sludge concentration affects digestion and dehydration. In order to efficiently digest, it is necessary to obtain a high concentration of sludge by concentrating sludge.

In the sludge aggregating process, the sludges generated at a plurality of treatment plants are pumped to a sludge aggregating treatment facility to be collectively processed. Changes in sludge properties during sludge transportation affect subsequent concentration, digestion, dehydration, etc.

[0004]

In recent years, the organic matter concentration in the inflowing sewage has been increasing due to the improvement of living standard, the transition of the sewage removal system, the progress of the surface preparation and the like. For this reason, in the concentrating device, changes in the properties of the sludge change due to the progress of rotting, which leads to a decrease in the concentration property. The decrease in the concentration property causes a decrease in the treatment efficiency of the subsequent sludge treatment system and an increase in the load of organic substances on the water treatment system due to the return water.

With the spread of sewerage, the amount of treated sewage is increasing year by year, and the amount of sludge generated is increasing at almost the same rate. This sludge treatment is a big problem not only in large cities with large restrictions on the treatment area, but also in small and medium-sized cities that have newly started treatment, because efficient sludge treatment with a small amount of sludge is difficult. As one of the solutions to this sludge treatment problem, sludge intensive treatment is drawing attention. The advantage is that 1) economies of scale of sludge treatment facilities,
2) Centralization of environmental measures for sludge treatment plants, 3) efficiency of energy recovery, 4) reduction of maintenance costs, and 5) improvement of sludge resource utilization.

Separation of sludge during transportation has become a problem in intensive treatment. Separation of sludge progresses during the pumping of the sludge transportation line, which deteriorates the concentrating property in the subsequent concentrating device and the dewatering property in the dewatering device. In addition, hydrogen sulfide generated by decay causes problems such as corruption of transportation facilities.

Sludge decay is caused by the decomposition of organic matter in sludge by anaerobic microorganisms. In order to prevent sludge spoilage, there is a method of inactivating anaerobic microorganisms and sulfate-reducing bacteria, which are the main causes of sludge spoilage, by using chemicals such as hydrogen peroxide and sodium hypozincate. However, its effect has not been clarified, and it has not been put to practical use.

In practice, only means such as cleaning the sludge pipe is used.

When ozone is used to prevent spoilage from spoiling, a relatively large amount of ozone is required. for that reason,
It is required to treat with an appropriate amount of ozone to prevent spoilage, and monitoring / controlling ozone injection leads to reduction in ozone treatment cost. However, there is currently no online method for monitoring changes in anaerobic microorganisms that directly cause sludge decay. Therefore, it is necessary to develop a method / measuring device for online monitoring of changes in sludge properties, including changes in anaerobic microorganisms.

The present invention has been made in view of the above-mentioned problems of the prior art, and its object is to remove p of sludge.
An object of the present invention is to provide a sludge ozonization method and device capable of simply and efficiently performing ozonation using the H value as an index.

[0011]

Means and Actions for Solving the Problems In order to achieve the above object, the present invention provides a batch type or a pre-stage of a concentrating device for sludge concentration in a sludge treatment system for digesting or dewatering after sludge concentration. A continuous contact tank is provided, and a certain amount of sludge is introduced or continuously flowed into this contact layer, ozone gas generated in the ozone generator is injected into this tank to contact the sludge, and the sludge during the ozone treatment The pH is measured, and the ozone generator is controlled by the controller using the pH value as an index to control the ozone injection amount, and the sludge is subjected to ozone treatment. Since the pH of sludge changes due to ozone treatment, p
Ozone treatment can be performed efficiently by controlling the H value as an index.

As a control index, the pH value at the processing end time or the processing end position, or the deviation value between the pH value at the processing start time or the processing start position and the pH value at the processing end time or the processing end position. Can be used.

Further, a sludge flow meter or a sludge densitometer for measuring the flow rate or concentration of sludge flowing into the contact tank is provided, and the control using the flow rate value or the concentration value as feedforward information is incorporated in the control device to adjust the pH value. The feed-forward control based on the flow rate value or the concentration value is added to the control based on the value to control the ozone generator.

[0014]

EXAMPLE As shown in FIG. 1, the present invention is to perform ozone treatment A on sludge before sludge concentration B in sludge treatment consisting of concentration B to final disposal E etc. Even in the case of FIG. 17), an ozone treatment device is provided before the concentration treatment device to prevent spoilage from spoilage.

As shown in FIG. 10, the basic constitution of the ozone treatment device is that the sludge is put into the contact tank 1 by the supply pump 8 and the ozone gas from the ozone generator 4 is injected into the sludge by the diffusion pipe 2 and stirred. The sludge is brought into contact with ozone by the vessel 3, the amount of injected ozone is calculated by the controller 6 based on the pH value of the sludge measured by the pH meter 5, and the ozone generator 4 is controlled to control the ozone of the sludge. The processing is performed efficiently.

The following is an experimental example of the sludge decay prevention effect and the color change of the sludge by the ozone treatment.

(1) Experimental method The sludge sample obtained at the municipal wastewater treatment plant is subjected to an ozone treatment experiment and a sludge leaving experiment to grasp the effect of suppressing sludge decay. Changes in the number of sulfate-reducing bacteria, the amount of hydrogen sulfide generated, and the concentration were used as indicators of sludge decay.

1) Ozone treatment experiment Ozone treatment was carried out by a semi-batch method. The experimental apparatus is shown in FIG. Effective volume 50L (Direct system φ = 261mm, Height H =
Sludge was put in a contact tank 1 (1.300 mm), ozone gas having a concentration of 50 g / Nm ³ was blown through a diffuser 2 installed at the bottom of the contact tank, and exhaust ozone gas was extracted from the upper part of the contact tank. During the ozone treatment, the contact bath 1 was placed in the constant temperature bath 19 for 2 seconds.
It was kept at 5 ° C. 0, 5, 12, 25 after starting ozone treatment,
Sludge was collected every 50, 75, 100, 150, 200 minutes, and the number of sulfate-reducing bacteria was measured. Further, sludge sampled at 0, 50, 100, and 200 minutes after the start of treatment was used as a sample for a standing experiment and a sedimentation test, and the effect of ozone to prevent the sludge from decaying was examined.

2) Sludge leaving experiment The outline of the sludge leaving experiment device is shown in FIG. Sludge treated with the ozone treatment experimental device (Fig. 11) was transferred to an Erlenmeyer flask 18
The magnetic stirrer 3a is rotated by the electromagnetic device 3b and stirred, and the gas generated from the sludge is trapped in the gas holder 21. For the samples treated with ozone at the respective injection rates, the hydrogen sulfide concentration in the gas holder was measured every 0, 4, 12, 24, and 48 hours after enclosing the sludge, and at the same time, the sludge was collected and the concentration of sulfate-reducing bacteria was reduced. Was measured. Also, 48
The sludge left to stand for a period of time was collected and used as a sample for a sedimentation test.

(2) Results 1) Change in the number of sulfate-reducing bacteria in the ozone treatment experiment The result of the ozone treatment experiment conducted on the sludge sample having an initial TS (evaporation residue) concentration of 10400 mg / L is shown in FIG. The horizontal axis represents the integrated value of the amount of ozone injected per unit sludge (ozone injection rate), and the vertical axis represents the number of sulfate-reducing bacteria.

From FIG. 13, the number of sulfate-reducing bacteria, which was on the order of 10 6 in the beginning, was decreased by ozone treatment,
At the ozone injection rate of about 200 mg / L, it has dropped to the order of the 10th power. Therefore, the sulfate reducing bacteria are inactivated by the ozone treatment.

2) Changes in pH in Ozone Treatment Experiment FIG. 14 shows changes in pH of sludge due to ozone treatment.
The pH is decreased by the ozone treatment.

3) Number of Sulfate-Reducing Bacteria and Amount of Hydrogen Sulfide Generated in Left-Hand Experiment FIG. The abscissa indicates the time of standing as elapsed time. The vertical axis shows the number of sulfate-reducing bacteria. Further, FIG. 16 shows changes in the amount of hydrogen sulfide generated. The horizontal axis shows elapsed time, and the vertical axis shows integrated value of hydrogen sulfide generation amount per unit sludge amount.
Note that A, B, C, and D in the figure represent samples in which ozone was injected at 0, 100, 200, and 475 mg / L in the ozone treatment experiment.

As shown in FIG. 15, in sample C (ozone injection rate: about 200 mg / L), the production of sulfate-reducing bacteria was suppressed for 12 hours. Sample D (Ozone injection rate approx. 475 mg
/ L), the number of sulfate-reducing bacteria was not imaged and was constant even when the sludge was allowed to stand for 48 hours. That is, the ozone injection rate is 47
It can be seen that 5 mg / L can control sludge rotting for 48 hours or more.

FIG. 16 shows changes in the amount of hydrogen sulfide generated in the standing experiment. This figure also confirms the above. In sample D (ozone injection rate: about 475 mg / L), hydrogen sulfide was not generated even after standing for 48 hours. Although the amount of hydrogen sulfide generated was not measured in Sample C, it is easy to suppress the generation of hydrogen sulfide for 12 hours or more from the results of the sulfate-reducing bacteria in FIG. 15 and the results of the hydrogen sulfide generation test in Sample D. Can be guessed. From these results, if at least 200 mg / L of ozone is injected into the sludge, the facility will be corroded by hydrogen sulfide at the average residence time (12 hours) in the gravity concentrating tank in the next step, generation of a foul odor, and settling due to putrefaction. It is possible to prevent deterioration of sex. Since gravity concentration is carried out through sludge transportation and the like, if the time required for this is, for example, 48 hours or more, it is necessary to treat at an ozone injection rate of about 475 mg / L.

On the other hand, by comparing the change in pH during the ozone treatment process (FIG. 14) with the above results, it can be seen that the required ozone injection rate can be determined from the pH value. For example, 12
If it is necessary to prevent spoilage for more than time, perform ozone treatment until the pH value becomes 6.1. If it is necessary to prevent spoilage for more than 48 hours, perform ozone treatment until the pH value becomes 5.8. Good. Further, the ozone treatment may be carried out with a difference from the initial pH value, that is, a pH decrease of 0.3 for 12-hour decay prevention and a pH decrease of 0.6 for 48-hour decay prevention, as judgment values. .

As a method of controlling the ozone injection rate (mass of ozone injected per unit sludge volume), 1) a method of controlling the ozone injection time (contact time, residence time), 2) a method of controlling the injected ozone concentration, 3) A method of controlling the injected ozone flow rate, 4) A combination of the above three is generally known.

In addition, it has been confirmed by another experiment that the required ozone injection rate for achieving the target is almost proportional to the sludge concentration (concentration of evaporative residue).

An embodiment of the sludge ozone treatment apparatus based on the above results will be described with reference to the drawings. In the figure, the same components as those shown in FIG. 10 are designated by the same reference numerals, and their duplicated description will be omitted.

Example 1 With reference to FIG. 2, this example relates to a batch type ozone treatment, and the apparatus has the same configuration as that described in FIG. The controller 6 operates the sludge feed pump 8 to load the sludge into the contact tank 1, and when the charging is completed, outputs an ON signal to the ozone generator 4 to generate ozone gas, and the contact tank 1 sludges the ozone gas. Contact.

Ozone gas is injected into the sludge until the pH value measured by the pH meter 5 reaches the target value, or until the difference from the initial pH value reaches the target value. An OFF signal is output to stop ozone gas generation. Then, the sludge pump 9 is operated to send the sludge that has been subjected to the ozone treatment to the next concentration step.

Therefore, according to this embodiment, the sludge can be efficiently ozone-treated mainly by controlling the ozone injection time.

Example 2 With reference to FIG. 3, this example relates to a batch type ozone treatment. The apparatus is provided with a sludge concentration meter 11 in the sludge inflow path in the apparatus of FIG. 2 and an ozone concentration meter 12 and an ozone concentration meter 12 in the ozone gas supply path. A gas flow meter 13 is provided.

The control device 6 controls the injected ozone concentration according to the sludge concentration (average sludge concentration) measured by the sludge concentration meter 11 when the sludge is fed into the contact tank 1 by the sludge feed pump 8.
It is equipped with a function to control one or both settings of the injected ozone flow rate, and outputs an ON signal to the ozone generator to generate ozone gas after completion of injection, and also outputs a concentration setting signal or flow rate setting signal to the ozone generator. The concentration or flow rate of the ozone gas thus generated is controlled to be equal to the set value, and when the pH value reaches the target value, an OFF signal is output to the ozone generator.

Therefore, according to this embodiment, the sludge can be efficiently ozone-treated by controlling the ozone concentration or the ozone flow rate to be injected mainly depending on the sludge concentration.

Example 3 With reference to FIG. 4, this example relates to continuous ozone treatment. The apparatus has contact chambers A ₁ and A ₂ and channels B _{1 to} B ₃ with partition walls 1a to 1d. The sludge that is formed and is introduced by the sludge supply pump 8 is configured to flow as shown by the dotted line.

Further, air diffusers 2 ₁ and 2 ₂ are provided in the contact chambers A ₁ and A ₂ , a pH meter 5 is provided in the treated sludge outflow path B ₂ , and an ozone concentration meter 12 and a gas flow meter 1 are provided in the ozone supply path.
3 is provided.

The control device 6 is the contact tank 1 measured by the pH meter 5.
Of the pH value at the treated sludge outflow position of
A concentration control signal or a flow rate control signal is output to the ozone generator 4 to control one or both of the injected ozone concentration and the injected ozone flow rate.

Therefore, according to this embodiment, the sludge can be efficiently subjected to continuous ozone treatment so that the pH value thereof becomes the target value while controlling the injected ozone concentration or the injected ozone flow rate.

Example 4 With reference to FIG. 5, this example relates to continuous ozone treatment, in which the apparatus is provided with pH meters 5 ₁ and 5 ₂ at the sludge inflow position and the treated sludge outflow position of the apparatus of FIG. is there.

Then, the controller 6 controls the deviation of the pH values measured by the pH meters 5 ₁ and 5 ₂ to reach the target value.
A concentration control signal or a flow rate control signal is output to the ozone generator 4 to control one or both of the injected ozone concentration and the injected ozone flow rate.

Therefore, according to this embodiment, the sludge can be efficiently subjected to continuous ozone treatment while controlling the injected ozone concentration or the injected ozone flow rate so that the difference in pH value before and after the treatment becomes constant.

Example 5 Referring to FIG. 6, this example relates to continuous ozone treatment, and the apparatus is a sludge flow meter 14 in the sludge supply path of the apparatus of FIG.
Is provided. Then, the control device 6 performs the control in which the feedforward control based on this information is added to the pH control performed by the device of FIG. 4 using the flow rate value measured by the sludge flowmeter 14 as the feedforward information.

Example 6 With reference to FIG. 7, this example relates to continuous ozone treatment, and the apparatus is a sludge flow meter 14 in the sludge supply path of the apparatus of FIG.
Is provided. Then, the control device 6 performs control in which the feedforward control based on this information is added to the pH control performed by the device of FIG. 5 using the flow rate value measured by the sludge flowmeter 14 as feedforward information.

Example 7 With reference to FIG. 8, this example relates to continuous ozone treatment, and the apparatus is provided with a sludge concentration meter 11 and a sludge flow meter 14 in the sludge supply path of FIG.

Then, the control device 6 calculates the sludge solid content from the sludge concentration and the sludge flow rate measured by the sludge concentration meter 11 and the sludge flow meter 14, and the feed forward information is shown in FIG.
The control is performed by adding the feedforward control based on this information to the pH control performed by the device.

Example 8 With reference to FIG. 9, this example relates to continuous ozone treatment, and the apparatus is provided with a sludge concentration meter 11 and a sludge flow meter 14 in the sludge supply path of FIG. Then, the control device 6 calculates the sludge solid amount from the sludge concentration and the sludge flow rate measured by the sludge concentration meter 11 and the sludge flow meter 14, and feeds it based on this information in the pH control performed by the device of FIG. 5 as feedforward information. Performs control with forward control added.

[0048]

Since the present invention is configured as described above, it has the following effects.

(1) Changes in the properties of sludge including changes in anaerobic microorganisms in sludge due to ozone treatment can be easily monitored by measuring pH.

(2) The injection amount of ozone required for preventing decay can be easily obtained.

(3) In an ozone treatment apparatus for the purpose of preventing spoilage, it is possible to prevent excessive ozone injection and reduce the cost of ozone treatment.

[Brief description of drawings]

FIG. 1 is a block diagram showing a sludge treatment system according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a batch-type ozone processing apparatus according to the first embodiment.

FIG. 3 is a configuration diagram of a batch-type ozone processing apparatus according to a second embodiment.

FIG. 4 is a configuration diagram of a continuous ozone processing apparatus according to a third embodiment.

FIG. 5 is a configuration diagram of a continuous ozone processing apparatus according to a fourth embodiment.

FIG. 6 is a configuration diagram of a continuous ozone processing apparatus according to a fifth embodiment.

FIG. 7 is a configuration diagram of a continuous ozone processing apparatus according to a sixth embodiment.

FIG. 8 is a configuration diagram of a continuous ozone processing apparatus according to a seventh embodiment.

FIG. 9 is a configuration diagram of a continuous ozone processing apparatus according to an eighth embodiment.

FIG. 10 is a basic control system configuration diagram of an ozone processing apparatus.

FIG. 11 is a structural diagram of an ozone treatment chamber experimental device.

FIG. 12 is a configuration diagram of a sludge leaving test device.

FIG. 13 is a graph showing changes in the number of sulfate-reducing bacteria in an ozone treatment experiment.

FIG. 14 is a graph showing a pH change in ozone treatment.

FIG. 15 is a graph showing changes in the number of sulfate-reducing bacteria in the standing experiment.

FIG. 16 is a graph showing changes in the amount of hydrogen sulfide generated in the standing experiment.

FIG. 17 is a block diagram showing an example of a conventional sludge treatment method.

[Explanation of symbols]

 1 ... Contact tank (ozone treatment tank) 2 ... Air diffuser 3 ... Stirrer 4 ... Ozone generator 5 ... pH meter 6 ... Control device 7 ... Exhaust ozone blower 8 ... Sludge supply pump 9 ... Sludge pump 11 ... Sludge concentration meter 12 ... Ozone concentration meter 13 ... Gas flow meter 14 ... Sludge flow meter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Noguchi 2-11-17 Osaki, Shinagawa-ku, Tokyo Stock Company Inside Shameidensha (72) Rie Matsui 2-1-117 Osaki, Shinagawa-ku, Tokyo Stock Association Shameidensha (72) Inventor Keiichi Tsukamoto 2-17 Osaki, Shinagawa-ku, Tokyo Stock company Shameidensha

Claims (7)

[Claims] 1. In sludge treatment for digesting or dehydrating sludge after it has been concentrated, before concentrating the sludge, the sludge is put into a contact tank, ozone gas is injected into the sludge, and the pH of the sludge is measured, Sludge p
A method for ozone treatment of sludge, characterized in that the amount of ozone gas to be injected is controlled using the H value as an index. 2. A sludge treatment device performed before sludge concentration in a sludge treatment system for digesting or dehydrating sludge after concentrating the sludge. An ozone generator for supply, a pH meter for measuring the pH of sludge in the contact tank, and a controller for controlling the ozone generation amount of the ozone generator using the measured value of the pH meter as an index. Ozone treatment equipment for sludge. 3. The control index of the control device is a deviation value between a pH value at a processing start point or a processing start position and a pH value at a processing end point or a processing end position. The sludge ozone treatment device according to 2. 4. The control according to claim 2, wherein a sludge flow meter or sludge concentration for measuring the inflow sludge amount or inflow sludge concentration is provided, and the measured flow rate value or concentration value is used as feedforward information. Ozone treatment device for sludge characterized by incorporating a part. 5. The sludge ozone treatment device according to claim 2, wherein the control index of the control device is a pH value at a treatment end point or a treatment end position. 6. The sludge ozone treatment apparatus according to claim 2, wherein the contact tank is a batch-type contact tank, and the treatment is performed in a batch-type. 7. The continuous contact tank capable of treating sludge by continuously flowing sludge therein.
The sludge ozonation apparatus according to any one of 5 above.