JPH05269481A - Waste water treatment method and sewage purifying tank by biological filtering method - Google Patents

Abstract

PURPOSE:To obtain highly treated water low in BOD and SS by the biological filtration of waste water. CONSTITUTION:In a waste water treatment method due to biological filtration wherein water 7 to be treated is passed througth a biological filter bed 2 composed of a granular carrier with specific gravity of about 1 or less to remove org. matter in the water 7 to be treated by aerobic biological decomposition and suspended particles are also removed by physical filtering action, a weighting body 5 is provided above the biological filter bed 2 composed of the granulare carrier and the biological filter bed 2 is pressed in a usual treatment process by the weighting body 5 to perform treatment. The pressing of the biological bed 2 by the weighting body 5 is released in a washing process to perform washing.

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 wastewater using a biological filtration method and a wastewater purification tank therefor.

[0002]

2. Description of the Related Art Microorganisms are aerobically biodegraded in a packed bed in which a granular carrier is submerged in a treatment tank to aerobically biodegrade organic matter-containing wastewater, together with suspended particles contained therein and generated biological properties. A number of methods have been proposed so far as a method for treating wastewater for removing aggregated particles, that is, a biological filtration method (also referred to as an immersion filter method). It can be said that any of these methods is effective for downsizing the treatment equipment because the volume load of BOD can be set larger than that of the activated sludge method. However, in the biological filtration method, it is necessary to wash the biological filtration layer because the particulate carriers are clogged in the biological filtration layer in the tank due to the trapping of particles in the wastewater and the growth of the generated biofilm. Since this cleaning operation is a difficult work, how to perform it by a simple method is a very important issue in implementation. The granular carriers to be filled are classified into those having a sedimentation property whose specific gravity is obviously larger than 1 and those having a floating property whose specific gravity is smaller than 1. Many of the sedimentable carriers generally have a specific gravity of about 1.4 to 2.5, but it is extremely difficult to wash the above-mentioned biological filtration layer in a biological filtration tank using these. While washing the biological filtration layer with air bubbling, wash water is sent from the bottom to expand the biological filtration layer and expel the trapped particles, but in many cases the biological filtration layer cannot be expanded due to the large specific gravity of the carrier. , Insufficient cleaning. Therefore, there is a method of facilitating cleaning by using a floating carrier having a small specific gravity. For example, Japanese Patent Publication No. 57-46884, Japanese Patent Publication No. 63-1116, Japanese Patent Publication No. 57-59000 and many other proposals can be seen. In both cases, the treatment by the biological filtration method is carried out using the floatable carrier.

[0003]

However, many of the methods disclosed in the above patent publications are natural biological filtration layers in which the biological filtration layer formed by the floating carrier is formed by buoyancy. In this case, the decomposition of organic matter due to the inhabitation of microorganisms is exhibited without any problem, but the capture of particles is not sufficient. That is, in order to maintain aerobic conditions, air is diffused from the lower part of the biological filtration layer, but the bubbles rise between the carriers while colliding with the carriers, so that the carriers flow particularly near the passage of the bubbles. Therefore, the trapped particles leak due to the separation of the biofilm due to the collision of air bubbles and the looseness due to the flow of the filtration layer. Therefore, low BOD, which is the original function of the biological filtration layer, and low SS with high transparency.
(Suspended particles) has the drawback that a high degree of treated water cannot be obtained. Therefore, the present invention provides a method for treating wastewater by a biological filtration method for obtaining highly treated water with low BOD and low SS, and a wastewater purification tank therefor.

[0004]

The present invention has a packed bed composed of a granular carrier having a specific gravity of about 1 or less, and the water to be treated is passed through the packed bed to aerate organic substances in the water to be treated. In a method for treating wastewater by a biological filtration method, in which the suspended particles are removed by physical biological action, and a suspended particle is also removed by a physical filtration action, a weighted body of the biological filtration layer is provided at an upper position of the biological filtration layer filled with a carrier. , A normal treatment step is performed by suppressing the biological filtration layer with a weighted body, and a washing step is performed by removing the biological filtration layer from the weighted body for cleaning, and a method for treating wastewater by a biological filtration method, and a tank The interior is divided by a partition wall, a plurality of various treatment tanks are provided, and the sewage purification tank in which treated water is sequentially admitted to these treatment tanks for purification, is the latter stage of the anaerobic treatment tank second chamber of the sewage purification tank. The processing tank has a specific gravity of about 1
A biological filtration layer composed of the following granular carriers is provided, and an air diffusing pipe and an advection pipe for both aeration and cleaning are arranged below the biological filtration layer, and a washing water discharge pipe is provided above the biological filtration layer. Is placed, and the inflowing treated water is received and stored, and a weight is provided to suppress the biological filtration layer by its weight to form a biological filtration tank, and the advection pipe and biological organism of the biological filtration layer are provided at the subsequent stage. The present invention relates to a sewage purification tank comprising a treated water tank which is connected to a cleaning pump for cleaning the filtration layer and accommodates the cleaning pump.

[0005]

First, the invention of claim 1 will be described. A synthetic polymer is used as the granular carrier having a specific gravity of about 1 or less.
Examples thereof include pellets of vinyl chloride, polyethylene, polypropylene, polystyrene and the like, or molded products obtained by primary foaming or secondary foaming thereof. Inorganic granular carriers include perlite from obsidian and pearlite. These carriers have a specific gravity of 1 or less, but some of them have a specific gravity adjusted by further adding a modifier. However, many carriers have a specific gravity of about 1 or less and easily float in water. Some of them have a specific gravity slightly increased due to the attachment and growth of microorganisms, and some of them exceed 1. However, even such a substance is easy to flow due to the flow of liquid. Therefore, the present invention does not regulate individual carriers, but applies to granular carriers having a specific gravity of about 1 or less, including those that are easily flowable.

A biological filtration method for treating wastewater by filling the above-described granular carrier in a biological filtration tank will be described with reference to FIG. 1 showing a wastewater treatment method according to an embodiment of the present invention. (A) is a diagram showing a normal treatment state (hereinafter, abbreviated as a filtration state) of a biological filtration tank, wherein the biological filtration tank 1 has a biological filtration layer 2 filled with a granular carrier having a specific gravity of about 1 or less, At the bottom of the biological filtration layer 2, there is a support material 3 for supporting the biological filtration layer 2, and at the bottom thereof an air diffuser 4 for supplying oxygen to the biological filtration layer 2 and for cleaning as described later. At the top of the biological filtration layer 2,
There is a weight body 5 for suppressing loosening of the biological filtration layer 2 in the filtration state, and a wash water discharge pipe 6 for washing described later is provided above the water level in the filtration state.

Here, the wastewater treatment method is performed as follows. The water 7 to be treated first enters the container of the weight 5 and then the weight 5
Overflows and is sprayed on the biological filtration layer 2. At this time, the weight body 5 receives the water 7 to be treated, and has a function of suppressing the biological filtration layer 2 by its weight. 2A and 2B are views for further explaining the weight body 5, in which FIG. 2A is a plan view and FIG. 2B is a sectional view taken along line AA. The weighted body 5 is composed of a water receiving chamber 9 for storing the water 7 to be treated, a discharge valve 10 for draining the water stored at the time of cleaning which will be described later, and a multi-port plate 11 for weighting the biological filtration layer 2. Since the water to be treated 7 overflows in the water receiving chamber 9, it is preferable that the upper end has a V notch, but this is not always necessary. The discharge valve 10 need not be provided if it has a narrow mouth that allows the water 7 to be treated to overflow.
The narrow mouth may be blocked by particles contained in the water to be treated 7 or microorganisms growing on the wall surface of the water receiving chamber 9, and in this case, it is preferable to provide it. The multi-mouthed plate 11 requires that the granular carrier of the biological filtration layer 2 does not escape to the upper side due to air bubbles, and the air bubbles are easily discharged.
It suffices if such measures are taken and does not regulate the structure. Reference numeral 12 is a protrusion for smoothing the vertical movement of the weight body 5, and is not always necessary.

In FIG. 1A, the water receiving chamber 9 of the weight body 5 is
The treated water 7 overflowing from the water passes through the multi-ported plate 11 of the weighted body 5 and enters the biological filtration layer 2. Here the treated water 7
Is decomposed by aerobic microorganisms grown on the carrier due to air bubbles from the bottom, reaches the lower layer, passes through the support material 3, passes through the advection pipe 13, and is discharged from the biological filtration tank 1 as treated water 8.

Here, in the biological filtration layer 2, without the weight 5, the granular carrier has a specific gravity of about 1 or less, so that the carrier flows due to the air bubbles rising from the lower part.
For the purpose of only the biodegradation of the BOD component, even if the carrier flows, it has an effect as a fluidized bed and there is no problem. However, for the purpose of highly removing SS as well, when the carrier is flowing, particles in the water to be treated, or particles captured,
Further, the SS becomes high due to the outflow of particles and the like from the grown microbial film, the BOD due to the SS also increases, and the quality of the treated water 8 deteriorates. Therefore BOD,
When removing SS to a high degree, it is extremely important to suppress looseness of the biological filtration layer 2 by the weight body 5.

When the treatment of the biological filtration tank 1 is continued, the resistance increases due to the particles trapped between the carriers of the biological filtration layer 2, so that the cleaning is necessary. The biological filtration layer 2 in FIG.
The cleaning method will be described. When moving from filtration to washing,
First, the discharge valve 10 of the weight body 5 is opened, and the water in the water receiving chamber 9 is drained. As a result, the weight body 5 becomes lighter, and the biological filtration layer 2 is loosened by air bubbles from the lower part, and the carrier also flows. At the same time, the treated water from the bottom of the biological filtration layer 2 is washed with water 14
As a cleaning waste water 15 is discharged out of the system through the cleaning water discharge pipe 6 provided above the set water level of the filtration state of the biological filtration tank 1 along with the separated particles of the biological filtration layer 2.

The washing is completed by stopping the feeding of the washing water 14, and the water in the biological filtration tank 1 is discharged from the advection pipe 13 in the tank through the conduit of the treated water 8 to set the set water level in the filtered state. Return to. When the discharge valve 10 of the weighted body 5 is closed accordingly, the water 7 to be treated accumulates in the water receiving chamber 9 of the weighted body 5, overflows and is sprayed on the biological filtration layer 2, and returns to the steady state.

As described in the invention of claim 1, the invention of claim 2 is means for suppressing loosening of the biological filtration layer 2 to improve the filtration performance. As shown in FIG. 2, in a normal treatment state (filtration state), the water 7 to be treated is stored in the water receiving chamber 9, and is a weighted body that suppresses the biological filtration layer 2 by this weight. Further, in cleaning the biological filtration layer 2, it is necessary to loosen and expand the biological filtration layer 2. Therefore, by opening the discharge valve 10 of the weight body 5 and discharging the liquid of the water receiving chamber 9, the weight body 5 is lightened. However, the biological filtration layer 2 can be washed with the air bubbles and the upward flow of the washing water.

A third aspect of the present invention applies the biological filtration method according to the first and second aspects of the present invention to a sewage cleaning tank. FIG. 3 is a sectional view showing an embodiment of the dirty water cleaning tank of claim 3. The sewage cleaning tank 16 includes partition walls 17, 18, 19,
It is partitioned by 20, and is composed of an anaerobic treatment tank (first chamber) 21, an anaerobic treatment tank (second chamber) 22, a treated water tank 23, and a disinfection tank 24. The anaerobic treatment tank (first chamber) 21 and the anaerobic treatment tank (second chamber) 22 accommodate contact materials 25 and 26, and remove coarse solids and decompose organic substances by anaerobic microorganisms. The biological filtration tank 1 is provided with the structure of claim 1 or claim 2 described above, and a granular carrier having a specific gravity of about 1 or less is housed as a biological filtration layer, and aerobic microorganisms remove residual organic matter from the preceding stage. At the same time as the decomposition, filtration is performed by capturing particles. The treated water tank 23 accommodates a cleaning pump 27 for cleaning the biological filtration tank 1 via the advection pipe 13 connected to the biological filtration tank 1. The treated water tank 23 is provided to secure the treated water as washing water. The disinfection tank 24 is provided for sterilizing the treated water 8 and discharging it. An air lift pump 28 transfers the anaerobic treated water 7 ′ from the anaerobic treatment tank (second chamber) 22 to the biological filtration tank 1.

Here, the processing steps and actions of the sewage cleaning tank will be described. The water to be treated 7 is supplied from the inflow port, enters the anaerobic treatment tank (first chamber) 21, and the coarse solid matter is removed by the contact material 25 while undergoing anaerobic decomposition, passing through the advection pipe,
Transfer to the anaerobic treatment tank (second chamber) 22. Here, too, the anaerobic microorganisms attached to the contact material 26 undergo anaerobic decomposition. Next, from the bottom of the anaerobic treatment tank (second chamber) 22 to the biological filtration tank 1 by the air lift pump 28, the anaerobic treated water 7 '
Is supplied to the biological filtration layer 2 as it flows into the water receiving chamber 9 of the weight body 5 in FIG. The anaerobic treatment tanks 21 and 22 are provided with a flow rate adjusting function in which the water level fluctuates above the contact materials 25 and 26, and the capacity of the fluctuation range can absorb the flow fluctuation of the water 7 to be treated at a peak ratio of about 3. (Not shown).

In the biological filtration tank 1, air is introduced from the air diffusing pipe 4 to undergo biodegradation by aerobic microorganisms in the biological filtration layer 2, and at the same time, SS (suspended particles) are also captured between the granular carriers by a filtering action. And reach the bottom. The soluble BOD of the water to be treated is sufficiently decomposed by this step, and SS is also removed, so that it becomes highly treated water with good transparency. The treated water enters the treated water tank 23 through the advection pipe 13, overflows from the upper portion to the disinfection tank 24, and is discharged as treated water 8 out of the system.

When the above-mentioned treatment is continued, the passage resistance of the biological filtration tank 1 is gradually increased by the microorganisms grown in the biological filtration layer 2 and the captured SS, so that the biological filtration layer 2 needs to be washed. This washing command can be washed by the signal when the water level of the biological filtration tank 1 rises to the set water level or when the required time is reached by the timer setting. In this case, it is desirable that the cleaning operation is performed when the water level of the anaerobic treatment tanks 21 and 22 is low, and it is usually set at night when there is no inflow of water to be treated. This is because there is no inflow of the anaerobic treated water 7'and the cleaning wastewater is returned to the anaerobic treatment tank 21.

The cleaning is performed as follows. When the discharge valve 10 of the weight body 5 is opened, the water in the water receiving chamber 9 is discharged and the weight body 5 becomes lighter. Continue the air diffusion at the bottom, and wash water pump 27
To run. As a result, the treated water in the treated water tank 23 is sent to the bottom of the biological filtration layer 2 as the wash water 14. The granular carrier of the biological filtration layer 2 becomes to flow due to the flow rate of the washing water due to the scattered air bubbles and the upward flow, and the weight 5 is also pushed upward. The SS and the like captured during this period are peeled off and transferred from the cleaning water discharge pipe 6 provided at the upper part to the anaerobic treatment tank (first chamber) 21 as cleaning drainage. The amount of water required for washing the biological filtration layer 2 is sufficient if the volume of the biological filtration layer 2 is equal to or more than the volume of the biological filtration layer 2. After the cleaning is completed, the anaerobic treated water 7 ′ flows into the weight body 5 to return to the normal treatment state.

[0018]

EFFECTS OF THE INVENTION According to the present invention, in a biological filtration method using a granular carrier having a specific gravity of about 1 or less, it is possible to suppress a biological filtration layer which easily flows due to air diffusion from the lower part, resulting in a low BO.
D, low SS and highly treated water can be obtained. As a method for suppressing the biological filtration layer, no mechanical mechanics are required and the inflow water from the previous stage which flows into the biological filtration layer is used, so that the means is slight. Further, by incorporating the above biological filtration method into a sewage purification tank, a small-sized and high-performance purification tank can be provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a method for treating wastewater according to an embodiment of the present invention, (a) is a diagram for explaining a normal treatment step and (b) is a diagram for explaining a cleaning step.

FIG. 2 is a diagram for explaining the action of the weighting body in FIG.
(a) is a top view and (b) is the AA sectional view.

FIG. 3 is a cross-sectional view showing a wastewater purification tank according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Biological filtration tank, 2 ... Biological filtration layer, 3 ... Support material, 4 ... Air diffuser, 5 ... Weighted body, 6 ... Wash water discharge pipe, 7 ... Treated water,
8 ... Treated water, 9 ... Water receiving chamber, 10 ... Discharge valve, 11 ... Multi-port plate, 12 ... Projection, 13 ... Advection pipe, 14 ... Wash water, 15
... washing wastewater, 16 ... sewage septic tank, 17,18,19,2
0 ... Partition wall, 21 ... Anaerobic treatment tank (first chamber), 22 ... Anaerobic treatment tank (second chamber), 23 ... Treated water tank, 24 ... Disinfection tank, 2
5, 26 ... Contact material, 27 ... Washing pump, 28 ... Air lift pump

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location B01D 29/62 C02F 3/00 E 8515-4D B 8515-4D 3/10 A

Claims (3)

[Claims] 1. A packed bed comprising a granular carrier having a specific gravity of about 1 or less, and by allowing the water to be treated to pass through the packed bed, organic substances in the water to be treated are removed by aerobic biodegradation. In a method for treating wastewater by a biological filtration method in which suspended particles are removed by a physical filtration action, a weighted body of the biological filtration layer is provided at an upper position of the biological filtration layer filled with a carrier, and a normal treatment step is performed by the weighted body. 2. The method for treating wastewater by the biological filtration method, wherein the biological filtration layer is treated while being suppressed, and the washing step is performed by releasing the suppression of the biological filtration layer by a weighted body. 2. The biological filtration method according to claim 1, wherein the weighted body receives and stores the water to be treated flowing into the biological filtration layer, and holds the biological filtration layer by the weight of the received water. Wastewater treatment method. 3. A sewage purification tank for partitioning the inside of a tank with a partition wall, providing a plurality of various treatment tanks, and sequentially adsorbing water to be treated to these treatment tanks for purification. The treatment tank which is the latter stage of the two chambers has a biological filtration layer made of a granular carrier having a specific gravity of about 1 or less, and an air diffusing pipe and an advection pipe both for aeration and cleaning are arranged below the biological filtration layer. In addition, a wash water discharge pipe is arranged above the biological filtration layer, and the inflowing treated water is received and stored, and a weight is provided to suppress the biological filtration layer by its weight, thereby providing a biological filtration tank. A sewage purification tank comprising a treated water tank in which the advection pipe of the biological filtration layer and a cleaning pump for cleaning the biological filtration layer are connected in a subsequent stage and the cleaning pump is housed.