JPH03238092A - Waste liquor treating device - Google Patents

Abstract

PURPOSE:To prevent the quality deterioration of the liquors being treated and oxidize sulfide in the waste liquors efficiently by a method wherein excessive sludge is sent from an upward flow reaction tank at the last stage of a first group of reacting part back into the upward flow reaction tank in the same group with the flow of at least a specific amt. of the liquors running into the first-mentioned reaction tank. CONSTITUTION:When waste liquor has reacted an upward flow reacting tank 6-4 at the last stage of a first group of reacting part 1, excessive sludge is removed therefrom with the flow of at least 5% of the amt. of the liquor running into the reacting tank 6-4 by the operation of a first sludge pump 22 provided on a pipe 21 and sent back into an upward flow reacting tank 6-2 in the same group, whereby the sludge consisting mainly of the anaerobic microorganisms produced in the first group of reacting part 1 is prevented from flowing into a second group of reacting part 2. In this way foul substances and sulfide are prevented from remaining in the liquor being treated, so that a good quality of treated water can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION 2-Field of Industrial Application This invention relates to a wastewater treatment device for removing solid matter, organic pollutants, etc. from wastewater such as urban sewage, industrial wastewater, and domestic wastewater.

BACKGROUND OF THE INVENTION Conventionally, there have been various wastewater treatment methods that utilize microorganisms, and a method disclosed in Japanese Patent Laid-Open No. 63-242394 has been proposed as a wastewater treatment method that can solve the problems associated with these methods.

Following the reaction tank in which oxygen is dissolved in the waste water, the waste water is slowly raised in an upflow reaction tank, and the aerobic microorganism group, anaerobic microorganism group, formed in this upflow reaction tank, A device for retaining self-granulated sludge containing solid matter in the same reaction tank, in which multiple stages of reaction sections each having the same reaction tank are provided, and these reaction sections act as solid-liquid separation in the previous stage. It is divided into a reaction section and a reaction section that acts as a subsequent biological reaction section. By the way, in such previously proposed wastewater treatment equipment, air or oxygen is supplied from a reaction tank equipped with an aeration device in each reaction section, and an aerobic process is carried out using an upflow type reaction tank. Filamentous bacteria will proliferate and self-granulating sludge will be formed.

Since the first stage reaction section lacks oxygen supply, most of the self-granulated sludge is made up of anaerobic microorganisms, while the second stage reaction section has aerobic microorganisms as the main constituent organisms because the amount of oxygen supplied and the amount of sludge material are balanced. It is important to operate the reactor in such a way that the anaerobic microorganisms in the front reaction section generate sulfides produced by these microorganisms in the waste water.

In such wastewater treatment equipment, the reaction tank equipped with an aeration device simply supplies oxygen to the wastewater, so its volume is much smaller than that of an upflow reaction tank. can be taken as a thing.

Problems to be Solved by the Invention During actual operation, a portion of the self-granulated sludge in the first reaction section flows into the second reaction section, and a considerable portion of the self-granulated sludge in the second reaction section is exposed to anaerobic microorganisms. may be occupied. In this way, when anaerobic microorganisms become the dominant species in the latter reaction section, which is the final treatment stage, pollutants remain in the treated water, and sulfides produced by the anaerobic microorganisms also remain, resulting in a decrease in the water quality of the treated water. There is a problem in that it causes deterioration. Moreover, if too much sludge increases in the final stage, it will be mixed with the treated water and flow out, causing another problem of deterioration of water quality.

Furthermore, the volume of a reaction tank equipped with an air diffuser can be made small as mentioned above, saving installation space, but if the volume is too small for this purpose, the reaction tank The sulfide is not removed in the wastewater and flows directly into the upflow reaction tank, and the sulfide produced in the upflow reaction tank is added to this, increasing the sulfide concentration in the wastewater. do. The sulfide concentration in the outflow water from the reaction tank equipped with the aeration device in this way was 3.2 mg.
When the temperature exceeds IQ, all of the oxygen supplied in the reaction tank will be consumed to oxidize the sulfide in the waste water, and when this concentration of sulfide flows into the final stage reaction section, this reaction section will be oxidized. There is also the problem that it is no longer possible to maintain the water aerobically, and the quality of the treated water deteriorates.

Therefore, the purpose of this invention is to solve the above-mentioned problems in the previously proposed wastewater treatment equipment, so that the self-granulated sludge in the first stage reaction section will not flow out to the second stage reaction section, and the self-granulated sludge will not flow out from the last stage reaction section. To provide a wastewater treatment device that does not mix sludge into treated water and can efficiently oxidize sulfides in wastewater.

Means for Solving the Problem Therefore, in order to achieve the above-mentioned object, the apparatus according to claim 1, in the already proposed wastewater treatment apparatus as described above, has the following features: In order to avoid mixing with the sludge produced in the sludge, the upper part of the upflow reaction tank in the final stage of the pre-stage reaction part is connected to the upflow reaction tank in the previous stage through a pipe line, and this pipe is connected to the final stage upflow type reaction tank. A pump is provided to return excess sludge to the upstream reaction tank of the previous stage at a flow rate of 5% or less of the amount of water flowing into the upflow reaction tank of the stage.

Furthermore, in the previously proposed wastewater treatment apparatus, the apparatus according to claim 2 is arranged such that the upper part of the reaction tank is closed so that the sludge in the final stage upflow type reaction tank of the latter reaction section does not flow out into the treated water. It communicates with the upstream reaction tank in the previous stage through a pipe, and this pipe has 5% of the amount of water flowing into the upflow reaction tank in the final stage.
A pump is provided to return excess sludge to the upstream reaction tank at the above-mentioned upstream stage at the following flow rate.

Further, the apparatus according to claim 3 is provided with a device for measuring the dissolved oxygen concentration in the waste water flowing out from each reaction section provided with an air diffuser and before flowing into the upward flow type reaction section, The amount of air diffused is controlled so that the oxygen concentration does not fall below 4 mg/l.

In the device according to claim 4, in each of the above devices,
A reaction tank equipped with an air diffuser was filled with a carrier made of plastic, nonwoven fabric, wood, ceramic, or the like.

Function: In the wastewater treatment device according to claim 1, when the waste water reaches the upstream reaction tank at the final stage of the front stage reaction section,
5% of the amount of water that has flowed into the reaction tank through a pipe connected to the upper part of the reactor by the operation of a pump installed in the pipe.
Excess sludge is pulled out at the following flow rate and returned to the upstream reaction tank, which prevents the sludge mainly composed of anaerobic microorganisms generated in the first reaction section from flowing into the second reaction section. be done.

Further, in the wastewater treatment apparatus according to claim 3, the dissolved oxygen concentration in the wastewater flowing out from each reaction section provided with the aeration device and before flowing into the upward flow type reaction section is measured by a measuring device,
When the concentration becomes 4 mg/Q or less, the amount of air diffused from the air diffuser is increased so that it becomes higher than that.

Furthermore, in the wastewater treatment device according to claim 4, even if the volume of the reaction tank provided with the aeration device is small, the bacteria group having the ability to oxidize sulfide that grows on the carrier filled inside the reaction tank can oxidize sulfide. will be oxidized and removed within a short time.

Example 8- FIG. 1 is a schematic diagram of an embodiment of the invention.

1 indicates a front reaction section consisting of four reaction sections, and 2 indicates a rear reaction section consisting of two reaction sections.In this way, this example has a total of six reaction sections, but the front and rear reaction sections are The number of stages may be other than this.

Each reaction section has a reaction tank 4 having an air diffuser 3 and an upflow reaction tank 6-1 to 6-6.

A waste water inflow pipe 7 is provided in the upper part of the first stage reaction tank 4, and the lower part of each reaction tank 4 and the upflow type reaction tanks 6-1 to 6-6 are connected by a pipe 8. The upper parts of the first to fifth stage upflow reaction tanks 6-1 to 6-5 and the upper parts of the adjacent reaction tanks 4 on the downstream side are connected by a pipe 9, and the final stage upflow reaction A treated water extraction pipe line 11 is connected to the upper end of the tank 6 .

Each pipe line 8 is provided with a dissolved oxygen concentration measuring device 12, and the amount of oxygen diffused from the aeration device 3 is adjusted by this measuring device 12.

The upper part of the upflow reaction tank 6-4 in the final stage (in this example, the 4th stage) of the pre-stage reaction section 1, and the upflow type reaction tank 6 in the previous stage (in this example, the 2nd stage) -2 is connected to the middle part by a first return pipe 21, and this return pipe 21 is provided with a first sludge pump 22. One end of a second return pipe 23 is connected to this return pipe 21 near its terminal end, and the other end of this pipe 23 is connected to the upper part of the final stage upward flow type reaction tank 66. A second sludge pump 24 is installed in route z3.
is provided. A branch pipe 25 from the pipe line 23 is provided, and its upper end is connected to the middle part of the fifth stage upflow type reaction tank 6-5.

In the above-mentioned wastewater treatment equipment, wastewater is introduced from the upper part of the first stage reaction tank 4 through the pipe 7, and the wastewater is diffused by the aeration device 3 at the lower part of the same kind of reaction tank 4.
It flows into the reaction tank 6-1 via the pipe line 8, and this reaction tank 6-
The waste water that has risen and overflowed in the reaction tank 1 flows into the lower part of the second stage reaction tank 4 via the pipe line 9.

The same process is repeated at each stage in the same way as in the previously proposed apparatus, during which the reaction vessels 6-1 to 6-6 contain aerobic microorganisms, anaerobic microorganisms, and self-organized microorganisms containing solid matter. The granular sludge is retained, and high-quality treated water produced by the action of the sludge is taken out from the final reaction tank 6-6 via the pipe 11.

When the wastewater is treated as described above, when the wastewater reaches the final upstream reaction tank 6-4 of the pre-stage reaction section 1,
Through the first return pipe 21 connected to the upper part of the reaction tank 64, by operating the first sludge pump 22 provided in the pipe 21, excess sludge is removed at a flow rate of 5% or less of the amount of water flowing into the reaction tank 64. The sludge mainly composed of anaerobic microorganisms produced in the first stage reaction section 1 is transferred to the second stage reaction section 1. 2 is prevented.

When we conducted an experiment on this issue, we found that the sulfide concentration in the treated water was 5 mg/12 when this method was not used as in the past, but when treated as described above, the sulfide concentration was the same. The concentration was changed to 1.5 μ/Q.

In this way, when the waste water reaches the upstream reaction tank 66 of the final stage (the sixth stage in this embodiment) of the rear reaction section 2, it is passed through the second return pipe 23 connected to the upper part of the upstream reaction tank 66. Conduit 2
By the operation of the second sludge pump 24 installed in the reaction tank 6-6, excess sludge is extracted at a flow rate of 5% or less of the amount of water that has flowed into the reaction tank 6-6, and the excess sludge is pumped out to the upper stage of the previous stage (second stage in this embodiment). The sludge is returned to the counter-current reaction tank 6-2, thereby preventing the sludge in the up-flow reaction tank 6-6 from reaching a certain level or higher, thereby preventing the sludge from mixing into the treated water.

When conducting an experiment on this matter, it was found that when this method was not adopted, the solids concentration in the treated water was 3z/Q, but when treated as described above, the same concentration was 11z/Q. Q's item was changed.

At this time, the dissolved oxygen concentration measurement device 12 provided in each pipe line 8 measures the concentration of dissolved oxygen in the wastewater before it flows into the upflow reaction tank 6, and the concentration is determined to be 4 mg/l or less. When this happens, the measuring device 12 issues a signal to increase the opening of the valve of the air supply pipe 13 to the air diffuser 3 or increase the rotational speed of the air supply blower to reduce the amount of acid gas into the reaction tank 4. The concentration of dissolved oxygen in the waste water discharged to the upflow reaction tank 6 is adjusted so that it does not become less than 4 mg/l. As a result, it was confirmed that aerobic filamentous bacteria proliferated stably in the upflow reaction tank 6.

Figure 2 shows the relationship between the sludge particle size μ and cumulative percentage when operating at dissolved oxygen concentrations of 1/Q and 4 mgIQ, respectively, as lines a and b.
When it is less than g/l, the particle size of the sludge is distributed in a small range, and it can be seen that the state of production of self-granulated sludge is worse than when it is more than that.

When treating wastewater as described above, the air diffuser 3
If a carrier made of plastic, nonwoven fabric, wood, ceramic, etc. is filled into the reaction tank 4 equipped with
Bacteria that have the ability to oxidize sulfides remaining in wastewater grow on these carriers, and the sulfides are oxidized and removed by these bacteria.

When we conducted an experiment on this issue, we found that if this method is not adopted, the sulfide concentration in the waste water flowing out from the reaction tank 4 in which the aeration device 3 of the latter stage reaction section 2 is installed will be 2.42+.
ng/Q, but when treated as described above, the same concentration was found to be 0.96 ng/Q.

Effects of the Invention The present invention is as described above, in which 5% of the amount of water flowing into the reaction tank from the upper part of the upflow reaction tank in the final stage of the pre-stage reaction section
The excess sludge extracted at the following flow rate is returned to the upstream reaction tank in the previous stage, thereby preventing the sludge mainly composed of anaerobic microorganisms generated in the first stage reaction section from flowing into the second stage reaction section. This has the effect of preventing pollutants and sulfides from remaining in the treated water due to their inflow, and allowing high-quality treated water to flow.

In addition, the present invention provides for removing surplus sludge from the upper part of the final upflow reaction tank in the latter reaction section at a flow rate of 5% or less of the amount of water flowing into the reaction tank, from the upper part of the upflow reaction tank in the previous stage. Since the sludge in the up-flow reaction tank of the final stage is not raised above a certain height, this prevents sludge from getting mixed into the treated water and prevents high-quality treated water from flowing out. There is an effect that can be done.

In addition, in this invention, in order to prevent the dissolved oxygen concentration of the wastewater flowing into the upflow reaction tank from becoming less than 4 mg/U,
Since the amount of air supplied from the air diffuser is constantly adjusted, aerobic filamentous bacteria grow stably in the upflow reaction tank at all times, resulting in efficient sewage treatment.

Furthermore, in this invention, by filling a reaction tank equipped with an air diffuser with a carrier, a group of bacteria capable of oxidizing sulfide grows on the carrier and oxidizes and removes sulfide. In addition, there is no need to increase the volume of the reaction tank, making it more compact, saving installation space, and sulfides can be removed efficiently in a short time.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of the present invention, and FIG. 2 is a graph showing the particle size distribution of sludge depending on the welding oxygen concentration. 1... Pre-stage reaction section 2... Post-stage reaction section 3... Diffusion device 4... Reaction tank 6... Upflow type reaction tank 13... Dissolved oxygen concentration measuring device 7.8, 9.11 Pipe line 21... First return pipe z2... First sludge pump

Claims (1)

[Claims] 1. A reaction section consisting of a reaction tank provided with an aeration device and an upflow reaction tank connected to the reaction tank is connected in multiple stages, and the reaction section is connected to a plurality of preceding stages. In a wastewater treatment system that is divided into a reaction section and a plurality of post-stage reaction sections, the upflow reaction system in the last stage of the pre-stage reaction section is designed to prevent the sludge produced in the first-stage reaction section from mixing with the sludge produced in the post-stage reaction section. The upper part of the tank is connected to the upstream reaction tank in the previous stage through a pipe, and excess sludge is poured into this pipe at a flow rate of 5% or less of the amount of water flowing into the final stage upflow reaction tank. , A wastewater treatment device characterized in that it is provided with a pump for returning the water to the upstream reaction tank. 2. A reaction section consisting of a reaction tank equipped with an aeration device and an upflow reaction tank connected to the reaction tank is connected in multiple stages, and the reaction section is connected to a plurality of pre-stage reaction sections and a plurality of upstream reaction sections. In a wastewater treatment equipment separated into a rear reaction section, in order to prevent the sludge from the final upflow reaction tank in the rear reaction section from flowing into the treated water, the upper part of the reaction tank is connected to the upflow reaction tank at the previous stage. The tank is connected to the tank through a pipe, and through this pipe, excess sludge is returned to the previous stage upflow reaction tank at a flow rate of 5% or less of the amount of water flowing into the final stage upflow reaction tank. A wastewater treatment device characterized by being equipped with a pump. 3. Equipped with a device to measure the dissolved oxygen concentration in the waste water flowing out from each reaction section equipped with an aeration device and before flowing into the upflow type reaction section, and ensuring that the dissolved oxygen concentration is 4 mg/l or less. Claim 1: The amount of air diffused is controlled to prevent
Or the wastewater treatment device according to 2. 4. The wastewater treatment device according to claim 1 or 2, wherein the reaction tank equipped with an aeration device is filled with a carrier made of plastic, nonwoven fabric, wood, ceramic, or the like.