JPH02208562A - Detection and control of anaerobic fermentation tank - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a load detection method and a load state control method for detecting the load state of an anaerobic fermenter that performs fermentation using biological reactions. The load condition is detected and utilized from the current gas generation rate of the processing liquid, the gas generation rate generated when sufficient substrate is added, and the ratio thereof.

[Prior Art] One of the methods for treating wastewater, etc., is fermentation treatment that utilizes biological reactions.
Alternatively, it is used as an anaerobic fermenter using anaerobic microorganisms, such as in a reactor for high-concentration wastewater.

In such an anaerobic fermenter, if the amount of wastewater or substrate that flows into the tank becomes overloaded beyond the allowable range, inhibitors to anaerobic microorganisms will gradually accumulate, reducing the fermentation processing capacity. .

In particular, if an anaerobic fermentor continues to be overloaded, methane bacteria often suffer damage that cannot be easily recovered, which has long been a major problem.

Therefore, since it is necessary to detect and deal with the load state of the anaerobic fermenter, the following load detection methods are mainly adopted.

■: Measures the pH inside the anaerobic fermenter and detects an overload condition from the drop in pH.

■: Detects overload status from the amount of volatile fatty acids accumulated in the anaerobic fermenter.

■: Detects overload conditions from a decrease in the amount of gas generated as a result of biological reactions in the anaerobic fermenter.

If these load detection methods determine that the inside of the anaerobic fermentor is overloaded, measures such as limiting the amount of wastewater and substrate flowing in, or adding slaked lime are taken to deal with this. Efforts are being made to reduce the load and recover anaerobic microorganisms.

[Problems to be Solved by the Invention] However, all of the conventional load detection methods for anaerobic fermenters have the following problems.

First of all, with the method of detecting the drop in pH as described in (2), the drop in pH appears after a considerable delay from the overload state, so it is too late to respond after detecting the drop in pH, and the anaerobic microorganisms will be seriously damaged. There is a problem with this.

In addition, with the method of detecting the amount of volatile fatty acids accumulated in (①), it is currently not possible to easily and automatically measure the accumulated amount of volatile fatty acids, so there is a problem that the status of the anaerobic fermenter cannot be immediately known. There is.

Furthermore, when detecting the decrease in the amount of gas generated in (■), the decrease in the amount of gas generated does not only occur when there is an overload condition;
There is also a problem in that it is impossible to judge whether the load is too low or if the load is too low.

Therefore, in any of the load detection methods, many parts are left to human judgment, and the load cannot be detected automatically or mechanically, and the load cannot be controlled in the anaerobic fermenter. This is the current situation.

This invention was made in view of the problems of the prior art, and it is possible to reduce the amount of gas generated due to overload by acetate! @
We focused on the difference that gas production does not recover even if a substrate for methane bacteria, such as an acid salt, is added, whereas a drop in gas production caused by too low a load can be recovered by adding sufficient substrate. It is an object of the present invention to provide a method for detecting a load in an anaerobic fermenter and a method for controlling the load in an anaerobic fermenter.

[Means for Solving the Problems] In order to solve the problems of the above-mentioned prior art, the load detection method for an anaerobic fermenter of the present invention includes After determining the current gas generation rate from the liquid containing anaerobic microorganisms and the gas generation rate based on the excess gas generation capacity obtained by adding sufficient substrate to this liquid, the load is detected from the ratio of these. The anaerobic fermenter load control method of the present invention is characterized in that when controlling the load of the anaerobic fermenter, the current gas generation rate and the gas generation rate stop ratio are 1. The present invention is characterized in that the inflow amount of the processing liquid is adjusted based on the detected load.

[Function] According to this method of detecting the load on an anaerobic fermenter, the current rate of gas generation is determined by measuring the amount of gas generated from the liquid in the anaerobic fermenter, and a sufficient amount of substrate is added to this liquid. The ratio of these is determined by measuring the amount of gas generated when the gas is recovered and determining the rate of excess gas generation.
When the ratio, which varies in the range of 0 to 1, approaches 1, it is assumed that the load is increasing, and when it approaches 0, it is determined that the anaerobic fermenter has surplus capacity, and the load state is detected.

In addition, according to this anaerobic fermenter load control method, the flow rate of the processing liquid is adjusted using the load detection results, making it possible to control the anaerobic fermenter according to the load, which was previously difficult. It is said that

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a schematic diagram of an embodiment of an anaerobic fermenter to which the anaerobic fermenter load detection method of the present invention is applied.

An anaerobic fermenter 1 to which this invention is applied ferments wastewater flowing in from a wastewater supply pipe 2 connected to the bottom with anaerobic microorganisms, and collects gases such as methane generated as a result of the biological reaction into a gas reservoir 3 at the top. The gas is collected and discharged to the outside through a gas exhaust pipe 4.

Load detection device 1 provided in such an anaerobic fermenter 1
0 is equipped with a gas generation tank 11 for load detection with an opening formed at the bottom, and the gas generation tank 11 is an anaerobic fermentation tank 1.
The upper half of the flap protrudes above the anaerobic fermenter 1, and the lower half of the flap is fixed within the anaerobic fermenter 1.

The upper end of the slurry sampling pipe 12 is open at the upper part of the gas generating tank 11 for load detection, and the lower end of the slurry sampling pipe 12 is located near the bottom of the anaerobic fermentation tank 1. The sludge 14 containing microorganisms is sent to the gas generation tank 11 via a constant flow type sludge collection pump 13 interposed in the middle, and gas is generated under the same conditions as the anaerobic fermentation tank 1 to check the current gas generation rate A. It is now possible to do so.

In addition, in order to generate gas with sufficient substrate added and measure the gas generation rate B, a chemical injection pipe 14 is connected to the slurry sampling pipe 12 on the outlet side of the slurry pump 13 so as to join together. A substrate is sent to this chemical feed pipe 14 via a chemical feed pump 16 from a chemical feed tank 15 for storing an aqueous solution of acetate, formate, etc., which are substrates for methane bacteria. ing. The chemical injection pump 164 is equipped with a timer 17 and is operated intermittently at preset intervals.

Further, a gas discharge pipe 18 is connected to the upper end of the gas generation tank 11 for discharging the generated gas.

The generation rate A of gas generated in such a gas generation tank 11
, B, a measuring device 20 is provided within the constant temperature device 19.

This measuring device 20 is composed of a gas flow meter 21 such as a mass flow meter type and a recorder 22 for recording the flow rate.
The measurement is performed after the gas from the gas generation tank 11 sent through the gas exhaust pipe 18 is purified.

For this purpose, an alkali cleaning tank 23 for gas purification is provided in the constant temperature device 19, and an alkali cleaning tank 24 for storing an alkaline cleaning liquid such as an aqueous sodium hydroxide solution is connected to an alkali injection pump 25 and an alkali injection pipe 26 for alkali cleaning. It is designed to be fed to the middle part of the tank 23.

Further, an alkali discharge pipe 27 is connected to the bottom of the alkali cleaning tank 23, and is once raised upward depending on the amount of alkali to be held, and then led out to the outside.

A gas exhaust pipe 18 is introduced into the alkali cleaning tank 23 and opens near the bottom, and the gas that has passed through the alkali and becomes clean is passed through the clean gas exhaust pipe 28 provided at the upper end. After being sent to the gas flow meter 21 via the gas flow meter 21, it is discharged to the outside.

In addition, the anaerobic fermentation tank 1 of the mud collection pipe 12 and the gas generation tank 11
A heat insulating material 29 is attached to the outside of the gas exhaust pipe 18 and to the outside of the gas exhaust pipe 18.

Further, as shown in FIG. 2, the gas generation tank 11 may be installed outside the anaerobic fermentation tank 1, and in this case, the entire gas generation tank 11 is covered with a heat insulating material 29.

Furthermore, in cases where corrosion due to gas is not a problem, the constant temperature device 19, an alkali cleaning tank 23, an alkali storage tank 24, an alkali injection pump 25,
Gas cleaning parts such as the alkali injection pipe 26 and the alkali discharge pipe 27 may be omitted.

Next, the operation of such a load detection device 10 and a load detection method will be explained.

(1) Measurement of current gas generation rate A.

In this case, the chemical injection pump 16 is kept in a stopped state, and the sludge 14 is pumped from inside the anaerobic fermentation tank 1 to the sludge collection pump 1.
3 and sends it to the gas generation tank 11.
It is returned to the anaerobic fermenter 1 from the bottom of the tank.

Then, gas is generated in the gas generation tank 11 at almost the same rate as inside the anaerobic fermentation tank 1 due to the action of methane bacteria contained in the sludge 14.

This gas is sent to the alkaline cleaning tank 23 via the gas exhaust pipe 18, where the carbon dioxide and hydrogen sulfide in the gas are absorbed, preventing corrosion of the equipment after the clean gas exhaust pipe 28, and preventing the corrosion of the equipment after the clean gas exhaust pipe 28. It is possible to measure the amount of methane produced, which is a component.

Only the methane that has become clean in this way is removed from the clean gas exhaust pipe 28.
The flow rate is measured by the gas flowmeter 21, and is recorded by the recorder 22, as shown in FIG. Desired.

(2) Measurement of gas generation rate B based on surplus gas generation capacity.

In this case, the chemical injection pump 16 is operated by setting the timer 17 etc. in order to carry out measurement with a sufficient amount of substrate such as methane bacteria added.

Then, in parallel with the operation of the chemical injection pump 16, the sludge 14 is sucked up from the inside of the anaerobic fermentation tank 1 by the sludge collection pump 13 to produce acetate! ll! Gas generating tank 11 along with substrates such as acid salts
from the bottom of the gas generation tank 11 to the anaerobic fermentation tank 1.
Return to

Then, in the gas generation tank 11, the methane bacteria contained in the sludge 14 are recovered by the substrate, and a large amount of gas is generated based on the excess gas generation capacity.

This gas is sent to the alkaline cleaning tank 23 through the gas exhaust pipe 18, and after being cleaned there, it is sent from the clean gas exhaust pipe 28 to the gas flow meter 21 where the flow rate is measured, as shown in FIG. 3, for example. is recorded by the recorder 22, and from this flow rate, the gas generation rate B is determined based on the surplus gas generation capacity when sufficient substrate is added.

(3) Calculation of the ratio: A/B that represents the load state.

In this way, the current gas generation rate A in the current state within the anaerobic fermentor 1 and the excess gas generation rate B when sufficient air quality is added are measured, and the ratio of these: A/B is determined.

This ratio: A/B is a value that changes in the range of 0 to 1.0, and if the anaerobic microorganisms in the anaerobic fermenter 1 have surplus capacity, this value will be close to O, and there will be no surplus capacity. , it becomes close to 1.0.

Therefore, by using this ratio: A/B, the load state of the anaerobic fermenter 1 can be known.

(4) Ratio: Load control by A/B.

When controlling the load of the anaerobic fermenter 1 based on the load state of the anaerobic fermenter 1 that can be detected in this way, for example, as shown in FIG. 4, using a computer or the like,
The current gas generation rate A before the start of chemical injection and the gas generation rate B based on the surplus gas generation capacity after chemical injection are electrically input.

Then, these ratios A/B are calculated, and if this value is, for example, ratio A/B = 0.8 or less, it is determined that the condition is normal and operation is continued, and the ratio A/B is = 0.8 or more, it is determined that there is an overload condition, and the inflow of processing liquid is restricted or stopped to prevent major damage such as methane bacteria caused by the overload condition. .

Note that it is also possible for the operator to adjust the inflow amount of the processing liquid, etc., based on the load state.

By calculating the ratio of the current gas generation amount to the gas generation capacity in this way, it becomes possible to quantitatively understand the remaining capacity of microorganisms in the anaerobic fermenter 1, which has been difficult to measure in the past. At the same time, the load status can be known.

It is also possible to automatically measure the amount of gas generated based on the current amount of gas generated and the gas generation capacity, and output it as an electrical signal, making it possible to automatically control the load on the anaerobic fermenter.

Furthermore, by detecting such a load state, it can be used to grasp the internal state when planning to gradually increase the load during the acclimatization process of microorganisms at the start of operation of the anaerobic fermenter.

In the above embodiment, the gas generation rate is determined from the amount of gas generated, but the present invention is not limited to this, and other methods may be used for detection.

[Effects of the Invention] As specifically explained above in conjunction with the embodiments, the method for detecting the load on an anaerobic fermenter according to the present invention measures the amount of gas generated from the liquid in the anaerobic fermenter to determine the current state. In addition to determining the gas generation rate, we measured the amount of gas generated when the liquid was recovered by adding sufficient substrate to determine the excess gas generation rate and calculated the ratio of these.
When the ratio that changes in the range of 1 to 1 approaches 1, it is assumed that the load is increasing, and when it approaches 0, it is determined that the anaerobic fermenter has surplus capacity, and the load state can be detected.

In addition, according to this method for controlling the load of an anaerobic fermenter, it is possible to adjust the flow rate of the processing liquid using the load detection results, making it possible to control the anaerobic fermenter according to the load, which was previously difficult. Become.

1: Anaerobic fermentation tank, 2: Waste water supply pipe, 3: Gas reservoir, 4
: Gas exhaust pipe, 10: Load detection device, 11: Gas generation tank, 12: Sludge collection pipe, 13: Sludge collection pump, 14: Chemical injection pipe, 15: Chemical injection tank, 1
6: Chemical injection pump, 17: Timer, 18: Gas discharge pipe, 1
9: Constant temperature device, 20: Measuring device, 21: Gas flow meter, 2
2: Recorder, 23: Alkali cleaning tank, 24: Alkali storage tank, 25: Alkali injection pump, 26: Alkali injection pipe, 27: Alkali discharge pipe, 28: Clean gas discharge pipe.

[Brief explanation of the drawing]

Figures 1 and 2 are schematic configuration diagrams of an embodiment of an anaerobic fermenter to which the load detection method for an anaerobic fermenter of the present invention is applied, and Figure 3 shows gas generation by the load detection method of the present invention. FIG. 4 is an explanatory diagram showing the measurement results of the amount, and is an explanatory diagram according to an embodiment of the load control method for an anaerobic fermenter according to the present invention.

Claims (2)

[Claims] (1) When detecting the load state in the anaerobic fermenter, the current gas generation rate from the liquid containing anaerobic microorganisms in the anaerobic fermenter and the surplus gas generation obtained by adding sufficient substrate to this liquid 1. A load detection method for an anaerobic fermenter, characterized in that after determining the gas generation rate based on the capacity, the load is detected from the ratio of these. (2) A claim characterized in that when controlling the load of the anaerobic fermenter, the inflow amount of the treatment liquid is adjusted based on the load detected from the ratio of the current gas generation rate and the gas generation rate. Item 1. Load control method for an anaerobic fermenter according to item 1.