JP2843160B2 - Waste water tertiary treatment equipment - Google Patents

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 tertiary wastewater treatment apparatus for tertiary treatment of biologically treated secondary effluent and discharging it.

[0003]

2. Description of the Related Art Generally, wastewater such as sewage, industrial wastewater and household wastewater is settled and separated (primary treatment), and then biologically treated (secondary treatment) and discharged to rivers and the like. But,
With the recent deterioration of wastewater contamination, tertiary treatment for further purifying secondary treatment water has been performed.

FIG. 4 shows a configuration of a conventional tertiary processing apparatus.

[0005] The secondary treatment water 101 is introduced into a mixing tank 102, in which a coagulant 103 is added and stirred. The effluent from the mixing tank 102 is introduced into the settling tank 104, where the floc 106 is settled. The settled flocs are taken out as settled sludge 107. The treated water after sedimentation is further separated into suspended solids SS in a sand filtration tank 108.
After being removed, it is discharged.

[0006]

However, according to the above-mentioned conventional tertiary treatment apparatus, since the flocculant 103 is added, not only the sedimentation sludge 107 increases, but also the fertilizer cannot be used, and industrial waste is not produced. Must be treated separately.

In addition, a soluble organic substance D-TOC (Disolved
Removal of TotalOrganic Carbon) is inadequate.

Further, there is another problem that the sand filtration tank 108 is liable to be clogged, so that the cleaning work must be performed frequently.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a tertiary treatment apparatus for wastewater capable of obtaining tertiary treatment water having extremely small amounts of soluble organic substances and suspended substances. It is in.

[Structure of the Invention]

[0011]

In order to achieve the above-mentioned object, the present invention introduces secondary treated water, and easily decomposes components contained in the secondary treated water by ozone treatment. An ozonation tank for converting components, a fluidized bed bioreactor for introducing the effluent of the ozonation tank, and bringing the fluid into contact with an aerobic biofilm formed on the surface of the carrier to remove the biodegradable component; and a fluidized bed. A fixed-bed bioreactor for introducing effluent from the bioreactor and removing suspended substances contained in the introduced water.

[0012]

D-TOC in the secondary treated water is composed of a component A that is easily biodegradable (biodegradable component) and a component B that is difficult to biodegrade (biodegradable component). When the secondary treatment water is brought into contact with the ozone gas in the ozone treatment tank for an appropriate time (5 to 60 minutes), most of the component B is changed to the component A. For this reason, D-TOC after the contact with the ozone gas can be removed at a very high level in the fluidized bed bioreactor. In addition, what constitutes the suspended solid SS are bacterial flocs and micro-animals. In a fixed-bed bioreactor, a floor on which small animals such as earthworms and rotifers can grow is installed, and the small animals inhabit the floor and prey on bacteria in the water. For this reason, SS in secondary treatment water can be removed at a very high level.

[0013]

FIG. 1 shows an embodiment of a tertiary wastewater treatment apparatus according to the present invention.

This tertiary treatment apparatus includes an ozone treatment tank 1 and
The fluidized bed bioreactor 2 and the fixed bed bioreactor 3 are sequentially connected and arranged.

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

A partition 8 having upper and lower openings 6 and 7 is disposed at a position slightly deviated from the axial center of the inside of the ozone treatment tank 1. Are divided into an ozone contact section 9 and a water guide section 10. An air diffuser 11 is provided 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 treatment water 5 by bubbling. .

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

Here, the supply amount of the secondary treatment water is represented by Q _L (m ³
/ H), the volume V ₁ of the ozone contact part 9 is 0.1
^{_{Q L ~Q L (m 3)}} , i.e., contact time 0.1h~
1h, the supply amount Q _{G-O3 ozone, Q L -10Q L (N-} m
³ / h).

The fluidized bed bioreactor 2 comprises a reaction section 17 for removing soluble BOD components contained in the effluent of the ozone treatment tank 1 supplied through a pipe 14 by contact with an aerobic biofilm. Sedimentation section 18 for separating excess sludge from water
It is composed of

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

Further, in the reaction section 17, anthracite, activated carbon, large carrier 25 than the specific gravity of the ceramic or the like 1 is turned at a rate of about 1 to 10% of the reactor volume V ₂ (V / V) The biofilm is formed in contact with the suspended solids SS contained in the wastewater.

The sedimentation part 18 is composed of a jacket 28 composed of a tapered part 26 having a wide angle extending upward from the upper end of the outer cylinder 19 and a cylindrical part 27 having both ends opened at the upper part thereof, and the partition wall 20. ing.

The reaction section 17 and the sedimentation 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 is separated from the sedimentation section 1.
8.

An overflow port 30 is formed at the upper end of the cylindrical portion 27 of the sedimentation section 18, and the treated water which has been separated into solid and liquid and overflows is fixed through a pipe 31 connected to the overflow port 30. Flow into bed bioreactor 2.

Here, the volume V ₂ of the reaction section 17 is 0.5
^{_{Q L ~3Q L (m 3)}} , i.e., residence time 0.5h
～3H, volume V ₃ of the precipitation unit 18, 0.5Q _L to Q
_L (m ^3), i.e., the residence time is 0.5H～1h, aeration rate Q _{G-Air is, Q L ~10Q L (N-} m 3 / h)
Is set to

The fixed-bed bioreactor 3 is a cylindrical processing tank having a bottom. The inside of the fixed-bed bioreactor 3 is vertically partitioned by a strainer 32, an upper part is filled with a filter medium 33, and a lower part is a distributor 34, a washing nozzle. 35 are provided. Distributor 3
The pipe 31 is connected to the pipe 31 to introduce the treated water of the fluidized-bed bioreactor 2. The cleaning nozzle 35 is connected to the pipe 3
6. The filter medium 33 is connected to the pressurized air source 24 via the on-off valve 37 and is provided for periodic cleaning of the filter medium 33. An overflow port 38 is provided in the upper part of the tank, and the final treated water is discharged to a river or the like via the overflow port 38.

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

First stage: DT in ozone treatment tank 1
Oxidative degradation of OC 2nd stage; Removal of oxidized D-TOC in fluidized-bed bioreactor 2 and solid-liquid separation of microorganisms 3rd stage; Capture of microorganisms in fixed-bed bioreactor 3 <First stage; Ozonation tank Oxidative Decomposition of D-TOC in No. 1> Usually, D-TOC is 10 to 20 (m
g / l). Among the D-TOCs, the biodegradable component A is a biochemical oxygen demand (BOD ₅ : Biochemi).
cal Oxygen Demand, JIS K0102), A = CB
OD ₅ and expressed. Here, C is a constant, and the theoretical value is 0.33. The ratio of the D-BOD ₅ and D-TOC, as shown in the following equation (1) corresponds to the composition ratio of the components A.

Composition ratio of component A = A / (A + B) A + B = TOC, A = C · BOD ₅ Therefore, A / (A + B) = C · BOD ₅ / TOC (1) FIG. And experimental results of changes in D-TOC and B-TOC.

As can be seen from the figure, the D-TOC hardly changes, but the B-TOC increases with time. This fact means that component B was changed to component A and the composition ratio of component A was increased. FIG.
Table 1 shows a trial calculation of the composition ratio of the component A and the component B using the equation (1).

[0031]

[Table 1]

As understood from Table 1, the composition ratio of the component A is 0.1 to 0.8 by contacting the ozone gas for 5 minutes.
3, while the composition ratio of component B is 0.9 to 0.1.
It has decreased to seven. Thus, the ozone gas is DT
By oxidatively decomposing OC, it is possible to convert the biodegradable component B into the biodegradable component A very effectively. Therefore, in the ozone contact portion 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 to a biodegradable component.

<Second stage: Removal of oxidized and decomposed D-TOC in fluidized bed bioreactor 2 and solid-liquid separation of microorganisms> In the reaction section 17 of the fluidized bed bioreactor 2, a carrier having a biofilm formed on its surface 25 is circulating and flowing by the air supplied from the air diffuser 22. Due to the air lift action 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 micro-animals on the surface of a carrier, and usually grows to a thickness of 0.1 to 1 mm. Therefore, the reaction unit 17
Is 2 to 5 times higher than that of a conventional biological treatment reaction tank represented by an aeration tank in the activated sludge method, and has a biological activity (eg, oxygen absorption coefficient) of 100 to 50.
0 mg / l / h and about 10 mg / l / h of activated sludge method 1
It becomes 0 to 50 times. Therefore, D-BOD ₅ can be removed by 90% or more in a processing time (convection time) of about one hour.

Therefore, at least 90% of the biodegradable component A in the ozonized water flowing from the ozone treatment tank 1 at the preceding stage can be removed in the reaction section 17. For this reason, D
-TOC is reduced to about 20%.

In the sedimentation section 18, the microbial floc and the detached biofilm flowing out of the reaction section 17 are settled to be separated into solid and liquid, and the supernatant is discharged from the overflow port 30. Is supplied to the fixed-bed bioreactor 3 as treated water. Since the supernatant contains microbial flocks and micro-animals, some suspended solids SS are present.

<Third Step: Capture of Microorganisms in Fixed-Bed Bioreactor 3> In the fixed-bed bioreactor 3, the filter medium 33 acts as a carrier for micro-animals. 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 small upward flow velocity of about 0.5 to 3 m / h. For this reason, implantation of small animals, such as earthworms and wheelworms, on the filter medium 33 is promoted. Implanted small animals prey on bacteria. Therefore, at the overflow port 38, overflow water with extremely small SS, that is, tertiary treated water is obtained. In addition, D-BOD ₅ in fluidized bed bioreactor 2
, The growth of bacteria in the filter medium 33 is suppressed. For this reason, blockage of the filter medium 33 by bacteria can be suppressed.

As described above, in this embodiment, the tertiary treated water is obtained by purifying the secondary treated water by the three-stage treatment. Table 2 and FIG. 3 by comparing each water quality of the second treated water and the third treated water
Shown in

[0038]

[Table 2]

As described above, according to this embodiment, the biological treatment is performed by the fluidized bed bioreactor 2 and the fixed bed bioreactor 3 to obtain the tertiary treated water. Removes D-BOD ₅ to a high degree. Further, since the processing time is short, the installation space can be reduced. In addition, blockage of the filter medium 33 of the fixed bed bioreactor 3 can be suppressed.

In this embodiment, the treated water of the fixed-bed bioreactor 3 is disposed as the final treated water. However, after the fixed-bed bioreactor 3, sand filtration or sand filtration + ultrafiltration membrane, etc. It is conceivable to provide a filtration tank having the following formula, and to completely prevent the outflow of the suspended solids SS by the filtration tank. Further, the filtration tank may be provided at a subsequent stage of the fluidized bed bioreactor 2.

[0041]

As described above, according to the present invention, the conventionally used coagulant is not required, and the soluble organic matter (D-
TOC) and tertiary treated water with extremely small amounts of suspended solids (SS) can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an embodiment of a tertiary wastewater treatment apparatus according to the present invention.

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

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

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

[Explanation of symbols]

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

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁶ identification code FI C02F 3/06 C02F 3/06 3/08 3/08 B (58) Field surveyed (Int.Cl. ⁶ , DB name) C02F 9/00 501-504 C02F 1/78 C02F 3/02-3/10

Claims (1)

(57) [Claims] 1. An ozone treatment tank for introducing secondary treatment water, for converting a component that is not easily degraded in the secondary treatment water into a component that is easily degraded by ozone treatment, and introducing treated water for the ozone treatment tank. A fluidized-bed bioreactor that is brought into fluid contact with an aerobic biofilm formed on the surface of the carrier to remove the biodegradable component, and the treated water of the fluidized-bed bioreactor is introduced, and the suspension contained in the introduced water is introduced. A tertiary treatment apparatus for wastewater, comprising: a fixed-bed bioreactor for removing a substance.