JPH04363199A - Termery treating device for waste water - Google Patents

Abstract

PURPOSE:To provide the ternary treating device for waste water which can extremely decrease suspended materials and soluble org. matter. CONSTITUTION:This device has an ozone treating tank 1 which is introduced with secondary treated water and converts the hardly biodecomposable components contained in this secondary treated water to easily biodecomposable components a fluidized bed bioreactor 2 which brings the water into fluid contact with the aerobic biomembranes formed on the surfaces of carriers 25 and removes the above-mentioned biodecomposable components and a fixed bed bioreactor 3 which is introduced with the treated water of the fluidized bed bioreactor 2 and removes the suspended materials contained in the introduced water.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater tertiary treatment apparatus for tertiary treatment of biologically treated secondary treated water and discharging it.

0003

[Prior art] Wastewater such as sewage, industrial wastewater, and domestic gray water is subjected to sedimentation separation (primary treatment) and then biological treatment (secondary treatment).
It is common to discharge the water into rivers, etc. However, with the recent worsening of wastewater pollution, tertiary treatment to further purify the secondary treatment water has been carried out.

FIG. 4 shows the configuration of a conventional tertiary processing device.

[0005] Secondary treated water 101 is introduced into a mixing tank 102, where a flocculant 103 is added and stirred. The outflow water from the mixing tank 102 is introduced into the settling tank 104, where the flocs 106 are settled. The settled flocs are taken out as settled sludge 107. The treated water after sedimentation separation is further filtered with suspended solids SS in a sand filter tank 108.
is removed and then released.

[0006]

[Problems to be Solved by the Invention] However, according to the above-mentioned conventional tertiary treatment equipment, since the flocculant 103 is added, not only does the amount of settled sludge 107 increase, but it cannot be converted into fertilizer, and industrial waste is discarded. must be treated separately as a product.

[0007] Also, the soluble organic substance D-TOC (Diso
Total Organic Carbon)
removal is insufficient.

Furthermore, since the sand filter tank 108 is easily clogged, there is a problem in that it must be cleaned frequently.

The present invention has been made in view of the above circumstances, and its purpose is to provide a tertiary treatment device for wastewater that can obtain tertiary treated water with extremely low amounts of dissolved organic matter and suspended solids. It is in.

[Configuration of the invention]

[0011]

[Means for Solving the Problems] In order to achieve the above object, the present invention introduces secondary treated water and removes components contained in the secondary treated water that are difficult to biodegrade by ozone treatment. an ozone treatment tank that converts the components into components; a fluidized bed bioreactor that introduces effluent water from the ozonation tank and brings it into fluid contact with an aerobic biofilm formed on the surface of a carrier to remove the easily biodegradable components; It is equipped with a fixed bed bioreactor that introduces the bioreactor effluent water and removes suspended solids contained in the introduced water.

0012

[Operation] D-TOC in the secondary treated water consists of a component A that is easily biodegradable (biodegradable component) and a component B that is difficult to biodegrade (biodegradable component). When the secondary treated water is brought into contact with ozone gas for an appropriate period of time (5 to 60 minutes) in an ozone treatment tank, most of component B changes to component A. Therefore, D-TOC after contact with ozone gas can be removed to an extremely high degree in a fluidized bed bioreactor. Furthermore, what constitutes the suspended solids SS are bacterial flocs and microscopic animals. In a fixed bed bioreactor, by installing a floor where microscopic animals such as earthworms and rotifers can settle, the microscopic animals live on this floor and prey on bacteria in the water. Therefore, SS in the secondary treated water can be removed to an extremely high degree.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the construction of an embodiment of a tertiary wastewater treatment apparatus according to the present invention.

[0014] This tertiary treatment device includes an ozone treatment tank 1,
It is constructed by sequentially connecting and arranging a fluidized bed bioreactor 2 and a fixed bed bioreactor 3.

The ozone treatment tank 1 has a cylindrical shape with a bottom and a lid, and pressurized secondary treated water 5 is introduced from a pipe 4 in the lid.

A partition wall 8 having upper and lower openings 6 and 7 is disposed at a position slightly offset from the axial center inside the ozone treatment tank 1. This partition wall 8 allows the inside of the treatment tank 1 to be is divided into an ozone contact section 9 and a water guide section 10. Further, an air diffuser 11 is disposed at the bottom of the ozone contact portion 9, and pressurized ozone gas 12 is introduced from the air diffuser 11 to oxidize and decompose D-TOC in the secondary treated water 5 by bubbling. .

An overflow port 13 is provided slightly below the upper opening 6 of the water guide section 10, and the ozonated water is passed to the fluidized bed bioreactor 2 through a pipe 14 attached to the overflow port 13. be introduced. Further, an exhaust pipe 15 is disposed on the top cover of the ozone treatment tank 1, so that the ozone accumulated in the upper part of the tank is decomposed through an ozone decomposition container 16 and then released into the atmosphere.

[0018] Here, the supply amount of the secondary treated water is QL (m
3/h), the volume V1 of the ozone contact part 9 is
0.1QL to QL (m3), that is, the contact time is 0.1h to 1h, and the ozone supply amount QG-O3 is QL
-10QL (N-m3/h).

The fluidized bed bioreactor 2 includes a reaction section 17 that removes soluble BOD components contained in the effluent of the ozone treatment tank 1 supplied via a pipe 14 by bringing them into contact with an aerobic biofilm; Sedimentation section 18 that separates water and excess sludge
It is composed of.

The reaction section 17 includes a bottomed cylindrical outer cylinder 19,
Provided slightly above the upper end of this outer cylinder 19, this outer cylinder 1
9 and a cylindrical partition wall 20 having the same radius. Further, inside the reaction section 17, a cylindrical air lift wall 21 with openings at both ends is submerged on the same axis in the longitudinal direction, and an air diffuser 22 is installed at the bottom of the reaction section 17. . The air diffuser 22 is connected to a pressurized air source 24 via a pipe 23. As a result, pressurized air is supplied and bubbles are generated within the reaction section 17.

[0021] Also, in the reaction section 17, a carrier 2 such as anthracite, activated carbon, ceramic, etc. having a specific gravity greater than 1 is provided.
5 is added at a rate of about 1 to 10% (V/V) of the reaction tank volume V2, and a biofilm is formed by contacting the suspended solids SS contained in the wastewater.

The settling section 18 is composed of the partition wall 20 and a jacket 28 consisting of a tapered section 26 having a wide angle upward from the upper end of the outer cylinder 19 and a cylindrical section 27 with openings at both ends disposed above the tapered section 26 . ing.

The reaction section 17 and the precipitation section 18 have a liquid junction structure at the gap between the outer cylinder 19 and the partition wall 20, that is, the communication port 29, and the wastewater treated in the reaction section 17 flows into the precipitation section 1.
8.

Further, an overflow port 30 is formed at the upper end of the cylindrical portion 27 of the settling section 18, and the treated water that has been separated into solid and liquid and overflowed is fixed through a pipe 31 connected to this overflow port 30. Flow into bed bioreactor 2.

Here, the volume V2 of the reaction section 17 is 0.
5QL to 3QL (m3), that is, the residence time is 0.5h to 3h, and the volume V3 of the settling section 18 is 0.5Q
L ~ QL (m3), i.e. the residence time is 0.5
h ~ 1h, and the ventilation amount QG-Air is QL ~ 1h.
It is set to 0QL (N-m3/h).

[0026] The fixed bed bioreactor 3 is a cylindrical treatment tank with a bottom, and the inside thereof is divided into upper and lower parts by a strainer 32, the upper part is filled with a filter medium 33, and the lower part is filled with a distributor 34 and a cleaning nozzle. 35 are arranged. Distributor 3
The pipe 31 is connected to 4, and the treated water of the fluidized bed bioreactor 2 is introduced thereto. The cleaning nozzle 35 is connected to the pipe 36
, is connected to the pressurized air source 24 via an on-off valve 37, and is used for periodic cleaning of the filter medium 33. Further, an overflow port 38 is provided at the top of the tank, and the final treated water is discharged into a river or the like through this overflow port 38.

Next, the operation of this embodiment will be explained in the following three stages.

First stage: DT in ozone treatment tank 1
2nd stage of oxidative decomposition of OC; removal of oxidized and decomposed D-TOC in fluidized bed bioreactor 2 and solid-liquid separation of microorganisms; 3rd stage; capture of microorganisms in fixed bed bioreactor 3 <1st stage; ozone treatment tank Oxidative decomposition of D-TOC in step 1 > Normally, secondary treated water contains 10 to 20 (m
g/l) included. Of D-TOC, biodegradable component A is biochemical oxygen demand (BOD5: Bio
Chemical Oxygen Demand, JI
SK0102), it can be expressed as A=C・BOD5. Here, C is a constant, and its theoretical value is 0.33. The ratio between D-BOD5 and D-TOC is calculated using the following formula (1
), it corresponds to the composition ratio of component A.

Composition ratio of component A=A/(A+B)A+B
=TOC, A=C・BOD5 Therefore, A/(A+B)=C・BOD5 /TOC……(1)
Figure 2 shows the experimental results of ozone gas contact time and changes in D-TOC and B-TOC.

As understood from the figure, D-TOC hardly changes, but B-TOC increases with time. This fact means that component B has changed to component A and the composition ratio of component A has increased. Figure 2
When the composition ratio of component A and component B is estimated using equation (1), it is as shown in Table 1.

[0031]

[Table 1]

As understood from Table 1, the composition ratio of component A changes from 0.1 to 0.8 by contacting with ozone gas for 5 minutes.
3, while the composition ratio of component B increased from 0.9 to 0.1
It has decreased to 7. In this way, ozone gas is
By oxidatively decomposing OC, the biodegradable component B can be converted into the biodegradable component A very effectively. Therefore, in the ozone contact part 9 of the ozone treatment tank 1, 2
If the residence time of the next treated water 5 is set to about 6 minutes, D
-TOC is sufficiently oxidized and most of it is converted into easily biodegradable components.

<Second stage: Removal of oxidized and decomposed D-TOC and solid-liquid separation of microorganisms in the fluidized bed bioreactor 2> In the reaction section 17 of the fluidized bed bioreactor 2, a carrier with a biofilm formed on the surface is removed. 25 is circulating and flowing by air supplied from the air diffuser 22. Due to the air lift effect of the generated bubbles, an upward flow is generated inside the air lift wall 21, and a downward flow is generated outside the air lift wall 21. A biofilm is a dense film of bacteria and microscopic animals on the surface of a carrier.
．． Grows to a thickness of 1-1 mm. For this reason, the reaction section 17
The microbial concentration in the activated sludge method is 2 to 5 times higher than in conventional biological treatment reaction tanks, such as aeration tanks, and the biological activity (e.g., oxygen absorption coefficient) is 100 to 50 times higher.
It is 0 mg/l/h, which is 10 to 50 times as much as the activated sludge method, which is about 10 mg/l/h. For this reason, D-BOD
5 can be removed by more than 90% in a treatment time (convection time) of about 1 hour.

[0034] Therefore, more than 90% of the biodegradable component A in the ozonated water flowing from the ozone treatment tank 1 in the previous stage can be removed in the reaction section 17. For this reason, D
-TOC decreases to about 20%.

In the settling section 18, the microbial flocs and detached biofilms flowing out from the reaction section 17 are settled and solid-liquid separated, and the supernatant liquid flows out from the overflow port 30 and flows into the fluidized bed bioreactor 2. The treated water is supplied to the fixed bed bioreactor 3. This supernatant liquid contains bacterial flocs and microscopic animals, so some suspended solids SS are present.

<Third stage: Capture of microorganisms in the fixed bed bioreactor 3> In the fixed bed bioreactor 3, the filter medium 33 acts as a carrier for microorganisms. That is, the treated water of the fluidized bed bioreactor 2 flowing from the distributor 34 passes through the filter medium 33 at a relatively low upward flow rate of about 0.5 to 3 m/h. Therefore, the attachment of microscopic animals such as earthworms and rotifers to the filter medium 33 is promoted. The implanted microscopic animals prey on bacteria. Therefore, at the overflow port 38, overflow water with extremely low SS content, that is, tertiary treated water is obtained. In addition, D-BOD5 in fluidized bed bioreactor 2
is removed, the growth of bacteria within the filter medium 33 is suppressed. Therefore, clogging of the filter medium 33 by bacteria can be suppressed.

As described above, in this embodiment, the secondary treated water is purified through three stages of treatment to obtain the tertiary treated water. Table 2 and Figure 3 compare the quality of secondary treated water and tertiary treated water.
Shown below.

[0038]

[Table 2]

As described above, according to this embodiment, since the fluidized bed bioreactor 2 and the fixed bed bioreactor 3 perform biological treatment to obtain tertiary treated water, the fluidized bed bioreactor 2 has high biological activity. D-BOD5 is removed to a high degree. Furthermore, since the processing time is short, the installation space can be reduced. Further, clogging of the filter medium 33 of the fixed bed bioreactor 3 can be suppressed.

In this example, the treated water from the fixed bed bioreactor 3 is disposed of as the final treated water, but sand filtration or sand filtration +
It is also conceivable to provide a filtration tank having an ultrafiltration membrane or the like to completely prevent the suspended solids SS from flowing out. Further, this filter tank may be provided at a later stage of the fluidized bed bioreactor 2.

[0041]

Effects of the Invention As explained above, according to the present invention, the conventionally used flocculant is not required and soluble organic matter (D-
It is possible to obtain tertiary treated water with extremely low levels of TOC) and suspended solids (SS).

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a tertiary treatment device for wastewater according to the present invention.

FIG. 2 is an explanatory diagram of the operation of an embodiment of the present invention.

FIG. 3 is an explanatory diagram of the operation of an embodiment of the present invention.

FIG. 4 is a configuration diagram showing a conventional tertiary treatment device for wastewater.

[Explanation of symbols]

1 Ozone treatment tank 2 Fluidized bed bioreactor 3 Fixed bed bioreactor 5 Secondary treated water 8 Partition wall 9 Ozone contact part 10 Water guide part 11　Air diffuser 17 Processing section 18 Precipitation part 21 Air lift wall 23　Air diffuser 33 Filter media 34 Distributor 35 Cleaning nozzle

Claims (1)

[Claims] [Claim 1] Introducing an ozone treatment tank that introduces secondary treated water and converts components that are difficult to biodegrade contained in the secondary treated water into components that are easily biodegradable through ozone treatment, and the treated water of the ozone treatment tank. A fluidized bed bioreactor is introduced into which the easily biodegradable components are removed by fluid contact with the aerobic biofilm formed on the surface of the carrier, and the treated water of the fluidized bed bioreactor is introduced, and the suspended water contained in the introduced water is introduced. A tertiary treatment device for wastewater, comprising: a fixed bed bioreactor for removing substances.