JP2614580B2 - Wastewater biological treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a wastewater containing a reducing sulfur compound by efficiently and rapidly cultivating and growing useful microorganisms that redox a reducing sulfur compound in a fixed-bed reactor. .

[0002]

2. Description of the Related Art Methods for biologically treating pollutants such as BOD, COD, and sulfide contained in municipal sewage, industrial groundwater, and industrial wastewater have been reported in literatures and the like.

[0003] In the case of treating a gas waste liquid by an activated sludge treatment method, good treatment performance can be obtained by controlling and controlling the amount of aeration using the oxidation-reduction potential of an aeration tank as an index. And JP-A-55-64896.

Further, when microbiologically decomposing pollutants, by maintaining the oxidation-reduction potential in the reactor at a value determined from a change in free reaction energy, useful microorganisms can be rapidly grown and cultured from activated sludge and sludge. The inventors have already invented what can be done.

[0005]

In the conventional method of treating a reducing sulfur compound by growing a sulfur-oxidizing bacterium from activated sludge mainly by a fluidized-bed bioreactor, a useful microorganism is easily washed out. Therefore, the concentration of useful microorganisms in the reactor decreased, and as a result, as shown in FIGS. 2 and 3, it was impossible to sufficiently treat the reducing sulfur compound. Another problem is how to prevent sudden deterioration of treated water quality due to bulking or the like caused by a large change in the concentration of reducing sulfur compounds in wastewater.

[0006]

The gist of the present invention is that sewage,
When cultivating and growing useful microorganisms suitable for wastewater treatment from activated sludge and sludge for treating industrial wastewater, the useful microorganisms that are easy to wash out are immobilized on a saddle-type ceramics microorganism immobilization carrier, and the wastewater that is to be treated Estimate the decomposition chemical reaction formula of the pollutant contained in the, find the oxidation-reduction potential from the amount of change in free reaction energy related to this pollutant decomposition reaction, and fix the microorganism-immobilized carrier that performs wastewater treatment A biological treatment method for wastewater, wherein the oxidation-reduction potential of a bed-type bioreactor is controlled and controlled to a value equal to or higher than the value obtained by this calculation. In this case, it is preferable to use a saddle-type ceramics microorganism-immobilized carrier mainly composed of granulated blast furnace slag as the saddle-type ceramics microorganism-immobilized carrier.

[0007]

FIG. 1 shows a fixed-bed type bioreactor for treating wastewater used for carrying out the method of the present invention.

The present inventors have found that activated sludge and sludge treating sewage and industrial wastewater contain microorganisms that oxidatively decompose reducing sulfur compounds. That is, microorganisms preferentially cultured and grown from activated sludge and sludge that are treating sewage and industrial wastewater by the microorganism acclimation and propagation method described below have a function of oxidizing reducible sulfur compounds to generate sulfuric acid. .

[0009] Further, when a saddle-type ceramic for immobilizing microorganisms is filled in a reactor for acclimating and growing microorganisms, and the microorganisms are acclimated and grown while being fixed, the washout of microorganisms is reduced.

[0010] While it is for acclimatization and proliferation of the reducing sulfur compound oxide decomposing microorganisms, firstly, assuming the oxidative decomposition reaction of the reducing sulfur compounds to obtain the free energy change amount in the reaction Handbook, from literature Next, an oxidation-reduction potential (ORP) for causing these oxidative decomposition reactions is obtained by calculation from the amount of change in free energy.

The above is described in more detail.
When a reducing compound is oxidized using a substance, cells of microorganisms
The reducing sulfur compounds absorbed in the inside are complicated by enzymes, etc.
It is oxidized through the reaction. But overall free energy
Changes between the starting compound and the final
It can be expressed by the difference from the compound.

For example, thiosulfuric acid is used as a reducing sulfur compound.
As an example, the redox system with thiosulfate in the cell
Reaction can be simplified and assumed as shown in Formula 1 below.
You.

[0013]

Embedded image

The amount of change in free energy in the above reaction
(ΔG) is the free energy of each substance of the above formula
It can be easily calculated by obtaining from the list.

Next, the free energy change (ΔG)
To obtain the oxidation-reduction potential (ORP, ΔE) from
Habe and Nagai, "Biochemical Engineering-Reaction Kinetics" (1975)
Of pollutants from wastewater to microbial cells as described in
Use the following equation (1) derived based on the model.
No.

[0016]

(Equation 1)

The ORP sensor 3, OR shown in FIG.
A fixed-bed type bioreactor 1 equipped with a P controller 5, a pH sensor 4, a pH controller 6, and the like is filled with saddle-type ceramics, and an activated sludge mixed solution for treating sewage or industrial wastewater is added thereto. The activated sludge is gradually fixed while circulating by using an air lift pipe 10 installed at the center of the reactor 1. After that, the ORP of the reactor 1 is set to the ORP value obtained earlier.

When a plurality of reducing sulfur compounds are present in the wastewater to be treated, the ORP values are different because the free energy of the oxidative decomposition reaction of each compound is different. For example, when sodium thiosulfate and hydrogen sulfide are present in the wastewater as reducing sulfur compounds, the calculated ORP values are +150 mV for sodium thiosulfate (based on the Ag / AgCl electrode) and about -80 mV for hydrogen sulfide (Ag / AgCl (Electrode reference). In such a case, when the ORP of the aeration tank is set to a more oxidizing side, that is, +150 mV (based on the Ag / AgCl electrode), an oxidation reaction or a decomposition reaction of both compounds occurs. From this fact, when acclimating and growing microorganisms suitable for wastewater in which sodium thiosulfate and sodium sulfide coexist as reducing sulfur compounds, the O at the outlet of the reactor where the activated sludge treating sewage or industrial wastewater is immobilized.
If the RP is maintained at +150 mV or higher (based on the Ag / AgCl electrode) and the wastewater containing these compounds is gradually supplied, it is considered that microorganisms that oxidize these compounds easily grow from the activated sludge.

Based on this idea, microorganisms that oxidize these compounds are adapted and grown. First, an activated sludge mixed solution subjected to sewage treatment is put into the fixed-bed type bioreactor 1 shown in FIG. Activated sludge is fixed to saddle-type ceramics filled in reactor 1 while air is blown in from diffuser pipe at the bottom of reactor 1 by roots blower 8 for about one day, and the activated sludge mixture is circulated by air lift pipe 10 installed in the center of reactor 1. Become After being fixed, the ORP value at the outlet of the reactor 1 is increased by +150 mV.
(Based on the Ag / AgCl electrode), and wastewater containing sodium thiosulfate and sodium sulfide as reducing sulfur compounds is supplied to the reactor 1 so that the treatment time is 8 hours. When the ORP value reaches +150 mV (based on the Ag / AgCl electrode), the growth of the microorganism is measured while sequentially reducing the treatment time to 6, 4, 3, and 2 hours.

After acclimation and propagation, wastewater treatment is performed. The reactor 1 in which activated sludge is immobilized on an immobilization carrier by the above method.
Then, wastewater in which sodium thiosulfate and sodium sulfide coexist as reducing sulfur compounds is supplied such that the treatment time is 2 to 3 hours, and the treatment is performed. At this time, the oxidation-reduction potential is measured by the ORP sensor (gold-silver / silver chloride composite electrode) 3 so that the ORP value at the outlet of the reactor 1 becomes +150 mV (based on the Ag / AgCl electrode). Is the number of rotations of the roots blower 7
Controlled by the P controller 5 and the inverter 9 to increase the pressure. Conversely, when the potential is higher than the set potential, the rotation speed of the roots blower 7 is controlled and reduced by the ORP controller 5 and the inverter 9 to control the ORP value.

Since the pH value in the reactor 1 is appropriately 5 to 6, the pH value is controlled by operating the acid / alkali addition pump by the pH sensor 4 and the pH controller 6.

Furthermore, in a highly efficient treatment for 2 to 3 hours, microorganisms separated from the immobilized carrier may flow out of the reactor 1 outlet. Therefore, when the water treated by the reactor is subjected to the downward filtration treatment by the filtration device 2 filled with saddle-type ceramics as a filtering material, good treated water can be obtained. The microorganisms deposited in the filtration device 2 are:
Backwash with treated water and air for treatment.

[0023]

EXAMPLE Activated sludge from sewage was charged into a fixed-bed type bioreactor and immobilized on a saddle-type ceramic immobilization support mainly composed of granulated blast furnace slag, and sodium thiosulfate (S ₂ ) was used as a reducing sulfur compound. O ₃ ^2- as 500
mg / l), 100mg as sodium sulfide ^{(S 2-}
/ L) was passed through so that the treatment time was 8 hours. Also, the ORP value at the reactor outlet is +150 mV
(Ag / AgCl electrode standard) The reactor was aerated while adjusting the flow rate of the air so as to keep the inside of the reactor at 5 to 6, while acclimating while adjusting the flow rate of the air. The sodium thiosulfate began to oxidize in a few days, and in about a week, the microorganisms that treated the wastewater acclimated.

The wastewater containing the reducing sulfur compound is passed through the reactor, which has been acclimated to the microorganisms by the above method, while reducing the treatment time so that the treatment time becomes 8 hours, 6 hours, 4 hours, and 3 hours. Water, and then treated by a filtration device, the properties of the treated water are COD <20 mg / l,
S ₂ O ₃ ^2- <1 mg / l and S ^2- <1 mg / l were favorable.

[0025]

According to the present invention, the acclimatization and growth of microorganisms capable of treating wastewater containing sodium thiosulfate and sodium sulfide as reducing sulfur compounds at once can be performed in a short period of time and efficiently. Highly efficient processing becomes possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing a fixed-bed bioreactor used to carry out the method of the present invention.

FIG. 2 is a diagram showing a comparison of changes in the concentration of useful microorganisms per m ³ of a reactor according to the method of the present invention and a conventional method.

FIG. 3 S ₂ O _{3 in} treated water by the method of the present invention and the conventional method
It is a figure which compares and shows the change of ^2- , ^S2- concentration.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed-bed type bioreactor 2 Filtration device 3 ORP sensor 4 pH sensor 5 ORP controller 6 pH controller 7 Roots blower 8 Roots blower 9 Inverter 10 Air lift tube

Claims (2)

(57) [Claims] When culturing and growing useful microorganisms suitable for wastewater treatment from activated sludge and sludge for treating sewage and industrial wastewater, useful microorganisms that are easy to wash out are immobilized on a saddle-type ceramics microorganism-immobilizing carrier, and , By estimating the decomposition chemical reaction formula of pollutants contained in the wastewater to be treated, calculating the oxidation-reduction potential from the amount of change in free reaction energy related to this pollutant decomposition reaction, A biological treatment method for wastewater, wherein the oxidation-reduction potential of a fixed-bed type bioreactor filled with an immobilization carrier is controlled and controlled to a value equal to or higher than the value obtained by this calculation. 2. The biological treatment of wastewater according to claim 1, wherein a saddle-type ceramics microorganism-immobilized carrier mainly composed of granulated blast furnace slag is used as the saddle-type ceramics microorganism-immobilized carrier. Method.