CN115135836A

CN115135836A - Sewage treatment system

Info

Publication number: CN115135836A
Application number: CN201980103579.5A
Authority: CN
Inventors: 洪凤昶; 沈仁台; 尹怜植
Original assignee: Pandi Human Korea Co ltd
Current assignee: Pandi Human Korea Co ltd
Priority date: 2019-12-30
Filing date: 2019-12-30
Publication date: 2022-09-30
Also published as: WO2021137310A1

Abstract

A sewage treatment system which treats overflow water as much as possible during a combined drainage pipeline sewage treatment, the system comprising: a sand settling chamber for preliminarily filtering foreign matters in the sewage to be treated; at least two radial multistage filtering devices, wherein the sewage to be treated passes through the radial multistage filtering parts after passing through the sand setting chamber and flows radially from the center, thereby being purified; a membrane filtration device for filtering the sewage to be treated, which has passed through the radial multistage filtration device, by using a membrane; and a sterilizing chamber which sterilizes the sewage to be treated which has passed through the membrane filtering device. The disclosed sewage treatment system accurately controls the purification speed of a filter device according to precipitation or rainfall, so that when dealing with 1Q or more of sewage, untreated overflow water can be prevented from occurring while maintaining stable quality of treated water. Particularly in case of rain, when 3Q sewage is treated, the treatment efficiency of the conventional primary settling chamber is drastically reduced, and the sewage treatment system of the present disclosure can treat the sewage into water having a normal water quality by introducing the radial multistage filtering device.

Description

Sewage treatment system

Technical Field

The present disclosure relates to a sewage treatment system for maximally treating combined water drainage pipeline overflows (CSOs), and more particularly, to a sewage treatment system capable of effectively treating an increased amount of sewage collected by a combined water drainage pipeline system, the increased amount of sewage being increased by rainwater in a rainfall event.

Background

The drainage pipeline system for delivering sewage to a sewage treatment plant is mainly divided into a combined drain system and a divided drain system. The combined drainage pipeline system conveys sewage and rainwater together through the same drainage pipeline, and the split drainage pipeline system conveys sewage, rainwater and underground water respectively through different drainage pipelines.

In korea, the dominant proportion of water pollution sources is gradually turning from point sources to non-point sources. A point source pollutant refers to a pollutant emitted from a single, identifiable source of pollution, such as a particular house, factory, or farm. Thus, domestic sewage, factory wastewater, and animal husbandry wastewater are classified as point-source pollutants. Since these contaminants are present at a specific point, it is easy to determine the discharge path or volume of the waste and to identify the discharge point of the waste. Non-point source contaminants refer to contaminants that occur in a wide range of areas, such as general homes, shopping malls, fish farms, courtyards, agricultural land and urban road surfaces. Since these contaminants originate at points that cannot be determined, it is difficult to determine the discharge path or volume of the waste and to identify the discharge point of the waste.

The combined drainage pipeline overflow classified as a non-point source contaminant is characterized by a high concentration of the contaminant and by a considerable volume. Therefore, it is practically difficult to treat the entire amount of CSOs generated in the event of intensive rainfall because a large amount of rainfall runoff suddenly flows into a sewage treatment plant together with domestic sewage. On the other hand, since the main function of the existing initial rainwater (first flush) management facility is to remove suspended solids in the initial rainwater rain, it is difficult to properly treat a large amount of rainwater and domestic sewage to the extent of satisfying the sewage discharge standard.

Therefore, when the load of sewage amount exceeds the treatment capacity of the sewage treatment plant, a large portion of untreated sewage inevitably overflows into the natural water body, thereby causing environmental pollution. In addition, such highly polluted high-speed rainfall runoff together with sewage entering a sewage treatment plant may cause floating of sand and/or slurry deposited in a grit chamber or settling tank, thereby disrupting the balance of microbial reactions in the bioreactor, resulting in effluent that fails to meet effluent quality standards. Therefore, there is a need to provide a solution to such problems.

Literature of the related art

Patent literature

[ patent document 1] Korean patent No. 10-1877408.

Disclosure of Invention

Technical problem

The present disclosure is made to solve the problems occurring in the related art and to propose a new sewage treatment concept in which an early treatment stage of a sewage treatment plant is set as a filtering stage, not a settling stage. By this arrangement, not only can the efficiency of sewage treatment be improved, but also the floor space of a sewage treatment plant can be greatly reduced, and the capacity of a plant can be greatly increased by making the bioreactor of a downstream stage optional.

That is, the existing sedimentation tank (called primary sedimentation tank) is replaced with at least two radial-flow multi-stage filtration devices (radial-flow multi-process filtration devices) which are periodically operated during dry periods and irregularly operated during rainy periods to perform washing at intervals adaptively adjusted according to the load of the amount of sewage. Through this design, the sewage treatment system according to the present disclosure can treat sewage, so that the treated sewage has better water quality than that of a conventional sewage treatment plant.

Technical scheme

A sewage treatment system according to a first aspect of the present disclosure for maximally treating a combined drainage pipeline overflow (CSOs) in a combined drainage pipeline system, the sewage treatment system comprising: the sand setting chamber is used for preliminarily removing foreign matters in the sewage to be treated; at least two radial flow multistage filtration devices designed to allow the sewage to flow radially from the center thereof to the outside for filtration; a membrane filtration device for filtering the sewage passing through the radial flow multistage filtration device using a membrane filter; and a sterilizing tank for sterilizing the treated sewage discharged from the membrane filtering device.

A sewage treatment system according to a second aspect of the present disclosure for maximally treating combined drainage pipeline overflow (CSOs) in a combined drainage pipeline system, the sewage treatment system comprising: the sand setting chamber is used for preliminarily removing foreign matters in the sewage to be treated; at least two radial flow multistage filtering devices designed to flow the contaminated water radially outwards from the center thereof for filtering; a bioreactor for removing organic matter, nitrogen and microorganisms from the wastewater passing through the radial flow multistage filtration device; a membrane filtration device that filters the sewage passing through the bioreactor using a membrane filter, or a settling tank that allows suspended solids and organic matters in the sewage passing through the bioreactor to settle to the bottom; and a sterilizing tank for sterilizing the treated sewage discharged from the membrane filtering device.

According to a third aspect of the present disclosure, in the sewage treatment system according to the first aspect of the present disclosure, the maximum sewage treatment capacity is 1Q under the condition that sewage is treated sequentially through the grit chamber, the radial flow multistage filtering device, the membrane filtering device, and the sterilizing tank. And when the amount of sewage supplied to the sewage treatment system exceeds 1Q, the radial flow multistage filtering device sends a portion corresponding to 1Q of the supplied sewage to the membrane filtering device, and the remaining portion is sent to the sterilizing tank.

According to a fourth aspect of the present disclosure, in the sewage treatment system according to the second aspect of the present disclosure, under the condition that sewage is treated sequentially through any one of the grit chamber, the radial flow multistage filtering device, the bioreactor, the membrane filtering device and the sedimentation tank, and the sterilizing tank, the maximum sewage purification treatment capacity is 1Q; when the amount of sewage supplied to the sewage treatment system exceeds 1Q, the radial flow multistage filtering device transfers a portion corresponding to 1Q of the supplied sewage to the bioreactor, the membrane filtering device and the sterilizing bath, and directly sends the remaining portion to the sterilizing bath.

According to a fifth aspect of the present disclosure, in the sewage treatment system according to the first aspect of the present disclosure, each of the radial flow multistage filtering devices comprises at least three cylindrical microporous filters which are concentrically arranged and have different diameters, respectively, wherein the mesh sizes of the microporous filters are gradually reduced from the innermost microporous filter to the outermost microporous filter.

According to a sixth aspect of the present disclosure, in the sewage treatment system according to the second aspect of the present disclosure, each of the radial flow multistage filtering devices comprises at least three cylindrical microporous filters which are concentrically arranged and have different diameters, respectively, wherein the mesh sizes of the microporous filters are gradually reduced from the innermost microporous filter to the outermost microporous filter.

According to a seventh aspect of the present disclosure, in the sewage treatment system according to the first aspect of the present disclosure, at least two radial-flow multistage filtering devices have the same filtering capacity or have different filtering capacities, and, in either case, if the filtering speed of one of the at least two radial-flow multistage filtering devices is reduced due to clogging of pores, the sewage is filtered using the other radial-flow multistage filtering device during at least one period of cleaning the radial-flow multistage filtering device in which the pores are clogged.

According to an eighth aspect of the present disclosure, in the sewage treatment system according to the second aspect of the present disclosure, the at least two radial-flow multistage filtering devices have the same filtering capacity or have different filtering capacities, and, in either case, if the filtering speed of one of the at least two radial-flow multistage filtering devices is reduced due to clogging of pores, the sewage is filtered using the other radial-flow multistage filtering device during at least one period of cleaning the pore-clogged radial-flow multistage filtering device.

These and other aspects, advantages, and salient features will become apparent from the following detailed description, the accompanying drawings, and the appended claims.

Advantageous effects

Unlike conventional sewage treatment systems, the sewage treatment system according to the present disclosure uses a radial flow multistage filtration device, instead of a primary sedimentation tank, and thus has a reduced floor area by 35% or more and a sewage retention time by 49% or more, as compared to conventional sewage treatment systems.

The sewage treatment system according to the present disclosure adaptively adjusts the cleaning interval of the filtering device according to weather (i.e., sunny or rainy days) or rainfall intensity, thereby always maintaining a predetermined effluent quality and preventing untreated overflow from being directly discharged into a natural water body. Particularly, in a rainfall event in which the amount of wastewater to be treated is increased to 3Q, the wastewater treatment system using the radial flow multistage filtering apparatus can treat wastewater to the extent that it is achieved under normal conditions, whereas the conventional wastewater treatment system using the primary sedimentation tank shows a significant drop in wastewater treatment efficiency.

In addition, the sewage treatment system according to the present disclosure exhibits a high removal rate of suspended solids by using a radial flow multistage filtering device instead of the primary settling tank used in the conventional sewage treatment system. Therefore, the sewage treatment system according to the present disclosure can increase the removal efficiency of suspended solids and BOD materials by 2 times as compared to the primary sedimentation tank. Therefore, the sewage treatment system according to the present disclosure can prevent the pore clogging of the membrane filter, and treat the sewage to the extent that the conventional three-stage water treatment process can be achieved, even without using a bioreactor or an aeration tank (aeration tank) at the downstream stage.

Drawings

Fig. 1 is a flow chart illustrating a process sequence for treating sewage in a conventional sewage treatment system.

Fig. 2 is a flowchart illustrating a flow sequence for treating sewage in a sewage treatment system according to a first embodiment of the present disclosure.

Fig. 3 is a flowchart illustrating a flow sequence for treating sewage in a sewage treatment system according to a second embodiment of the present disclosure.

Fig. 4 is a schematic view illustrating a radial flow multistage filtration apparatus of a sewage treatment system according to a first embodiment of the present disclosure.

Fig. 5 is a perspective view illustrating a radial flow multistage filtration apparatus of a sewage treatment system according to a second embodiment of the present disclosure.

Best mode for carrying out the invention

The above objects, features and advantages and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings. Reference should now be made to the drawings, in which the same reference numerals are used throughout the different drawings to designate the same or similar components. It will be understood that, although the terms "one side," "another side," "first," "second," etc. may be used herein to describe various elements, these elements should not be limited by these terms. In addition, when it is determined that detailed description of known technologies related to the present invention may possibly cover the gist of the present invention, the detailed description thereof will be omitted.

Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic view of a conventional sewage treatment system 10 in which sewage collected through a combined flow drain line system passes through a grit chamber 1, a primary sedimentation tank 2, a bioreactor or aeration tank 3, a secondary sedimentation tank 4 or a membrane filtration device 4' and a disinfection tank 5 in this order, and the treated sewage is discharged to the environment.

Here, it is assumed that "sewage to be treated" (hereinafter, referred to as "sewage") is fed to the sewage treatment system 10 in an amount of 1Q during sunny or dry weather. In this case, the grit chamber 1 preliminarily removes foreign matters in the sewage to be treated. In the settling chamber 1, heavy solids (e.g., solids and sand) having a relatively high specific gravity may settle to the bottom, while light solids having a relatively low specific gravity float to the surface. The settled and floating material is removed from the settling chamber 1. The sand settling chamber 1 alone cannot sufficiently treat the sewage to an extent suitable for discharge into the environment. The grit chamber 1 provides only a pre-treatment function. The sewage passing through the grit chamber 1 still contains particulate contaminants. These particulate contaminants, which have a lower specific gravity than the particulate contaminants removed by the grit chamber 1, are then precipitated in the primary sedimentation tank 2. Therefore, the primary sedimentation tank 2 requires a large floor space and a long residence time. The sewage passing through the primary sedimentation tank 2 flows into the bioreactor 3, in which microorganisms grow at a high concentration to improve the efficiency of removing organic matter and nitrogen. This process produces activated sludge as a by-product, and the activated sludge is settled to the bottom in the secondary sedimentation tank 4. The supernatant in the secondary sedimentation tank 4 passes through a disinfection tank 5 and then leaves the sewage treatment system.

Recently, Membrane Bioreactors (MBR) or membrane filtration devices 4' have been used instead of the bioreactor 3 or secondary sedimentation tank 4. The membrane bioreactor 4' is a membrane-related treatment device that replaces the settling tank used in the final treatment stage of a conventional biological process. In the membrane bioreactor 4', it is necessary to maintain a high concentration of bacteria to improve the efficiency of removing organic matter and nitrogen, and to remove suspended solids and microorganisms using a membrane filter to improve the solid-liquid separation efficiency. Therefore, the membrane bioreactor can solve the problems brought by the earlier biological process.

The term "1Q" used in the description of the present disclosure refers to an amount of sewage that the sewage treatment system can normally treat during dry or clear weather. The terms "2Q", "3Q" and "4Q" refer to 2 times, 3 times and 4 times "1Q", respectively. Therefore, in the case of the conventional sewage treatment system shown in fig. 1, excessive sewage, i.e., sewage exceeding "1Q", is treated only by the grit chamber 1 and the primary settling tank 2 and then discharged into the natural water body. That is, the excessive sewage bypasses the bioreactor 3 provided at the downstream stage to avoid affecting the active reaction of the microorganisms in the bioreactor 3. This method is currently used in most countries, including korea.

However, if new innovative technologies are developed in the future, the sewage standards for treating early rain falls will become more stringent during wet or rainy weather. That is, during wet or rainy weather, it is preferable to be able to continuously treat incipient rain rainfall and domestic sewage in an amount of up to 4Q. However, no country in the world has such a system.

For example, in order for the conventional sewage treatment system to completely treat sewage having a volume exceeding 1Q to 4Q, it is necessary to increase the treatment capacity of each of the grit chamber 1 and the primary settling tank 2 to 4 times the treatment capacity designed to treat the amount of sewage of "1Q". In this case, the sewage treatment system requires a considerable site area. In wet or rainy weather, when water exceeding 1Q enters a sewage treatment system, the large volume of water entering the system may contain very high concentrations of organics and suspended solids. Therefore, it would be highly desirable if such wastewater could be converted to wastewater containing low levels of suspended solids and low concentrations of organic matter.

In other words, when sewage exceeding 1Q flows into the sewage treatment system during wet or rainy weather, since the grit chamber 1 is designed to treat sewage equivalent to "1Q", there is a possibility that the grit chamber 1 cannot preliminarily treat all foreign substances in excessive sewage containing non-point-source pollutants, which occurs in a wide area such as residential areas, shopping malls, fish farms, courtyards, farmlands, and urban road surfaces, due to the high flow rate of sewage. In the grit chamber 1, heavy objects having a relatively large specific gravity, such as stones and sand, cannot sink in water due to the rapid flow of sewage, but may float to the surface. That is, the debris chamber 1 may not be able to perform a simple primary cleaning process.

In this case, the sewage passing through the grit chamber 1 contains organic matter in a high concentration as in the initial rain fall, and heavy solids having a large specific gravity, such as stones and sand, taken away from the grit chamber 1. Even in the primary sedimentation tank 2 having a 1Q treatment capacity, heavy solids and suspended solids having a large specific gravity are hardly sedimented to the bottom due to the rapid flow of sewage. The insufficiently precipitated 1Q wastewater flows into the bioreactor 3, thereby disrupting the balance of the microbial reactions in the bioreactor 3. Therefore, the efficiency of the biological decomposition in the bioreactor 3 is decreased. The resulting sewage having poor treatment effect has a problem that the effluent standard cannot be satisfied.

In addition, the excessive sewage, i.e., the sewage exceeding 1Q, is not subjected to all processes of the sewage treatment system, but is subjected to only the processes of the grit chamber 1 and the primary settling tank 2. Therefore, the sewage containing a large amount of suspended solids and high concentration of organic matter is directly discharged into a river or stream, thereby polluting the river or stream. Even in the case where the treated sewage is discharged into a river or stream through the disinfection tank 5, the sewage cannot be sufficiently disinfected because the sewage to be treated contains a high concentration of suspended solids and a high concentration of organic matter.

Fig. 2 is a flowchart illustrating a sequence of unit processes performed in the sewage treatment system 100 according to the first embodiment of the present disclosure, and fig. 3 is a flowchart illustrating a sequence of unit processes performed in the sewage treatment system according to the second embodiment of the present disclosure. Fig. 4 is a schematic diagram illustrating a radial flow multistage filtration apparatus 70 of a wastewater treatment system 100, according to a first embodiment of the present disclosure.

According to the first embodiment of the present disclosure, the sewage treatment system 100 is designed to treat as many combined drainage pipeline overflows (CSOs) as possible when purifying the sewage collected by the combined drainage pipeline system. Referring to fig. 2 and 4, the sewage treatment system 100 includes a grit chamber 60 for primarily removing foreign materials in sewage to be treated; a radial flow multistage filtering device, in which sewage flows radially outward from the center thereof so as to be purified while passing through the radial flow multistage filtering unit 73; a membrane filtration device 82 for removing organic matter, nitrogen gas, etc. in the sewage using a membrane filter, and a sterilization tank 90 for sterilizing the treated sewage.

As shown in fig. 3 and 4, a sewage treatment system 100 according to a second embodiment of the present disclosure is a sewage treatment system capable of treating as much amount of merged drain pipe overflow collected through a merged drain pipe system as possible. The system 100 includes a sand settling chamber 60 for primarily removing foreign materials from sewage to be treated; a radial flow multistage filtering apparatus 70 for flowing the contaminated water radially outward from the center thereof, through the radial flow multistage filtering apparatus 73, for filtering; a bioreactor 81 for removing organic matter, nitrogen, etc. from the sewage; a membrane filtration unit 82 or a sedimentation tank 83, and a disinfection tank 90 for disinfecting the treated sewage.

The sewage treatment system 100 according to the present disclosure is used to treat sewage collected by a combined drainage pipeline system. In rainy seasons, the combined drainage pipeline system is easily subject to overflow, and the sewage treatment system 100 according to the present disclosure can be effectively used to solve such problems. The sewage treatment system 100 according to the present disclosure is constructed by modifying an existing sewage treatment system. Specifically, the settling tank of the conventional sewage treatment system is replaced with at least two radial-flow multistage filtering devices 71 and 72 to solve the problem of insufficient sewage treatment capacity of the sewage treatment system due to an excessively long retention time in the settling tank of the conventional sewage treatment system.

According to the present disclosure, the number of radial flow multistage filtration devices may be at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19. One of ordinary skill in the art can readily determine the appropriate number of radial flow multi-stage filtration devices based on the volume of waste water or system capacity during rainfall events.

As described above, the function of the grit chamber 60 is to primarily filter foreign materials in the sewage to be treated. In the grit chamber 60, heavy solids (e.g., solids and sand) of relatively high specific gravity can settle to the bottom, while light solids of relatively low specific gravity float to the surface. The settled and floating material is removed from the settling chamber 1. The sand settling chamber 1 alone cannot sufficiently treat the sewage to an extent suitable for discharge into the environment. The grit chamber 1 provides only a pre-treatment function.

The structure of the radial flow multistage filtering apparatus 70 according to the present disclosure is such that, as shown in fig. 4, sewage flows into the center of the filtering apparatus and then flows radially outward, passing through the radial flow multistage filtering unit 73 (corresponding to the filtering module 39 in fig. 5). Thereby, the sewage is purified. The radial-flow multistage filtering unit 73 includes a curtain-wall filter 74 (corresponding to the component denoted by reference numeral 41 in fig. 5) having a cylindrical wall of a predetermined thickness, in which a fiber medium is contained; a first fine mesh filter 75 (corresponding to a member denoted by reference numeral 43 in fig. 5) arranged outside the curtain wall type filter 75, and a second mesh filter 76 (corresponding to a member denoted by reference numeral 45 in fig. 5) installed outside the first fine mesh filter 75.

The curtain wall type filter 74, the first fine mesh filter 75 and the second fine mesh filter 76 of the radial flow multistage filtering device 73 are arranged in such a manner that the mesh size is gradually reduced from the innermost filter to the outermost filter, thereby appropriately filtering the sewage flowing radially outward.

According to a preferred embodiment, the curtain-walling filter 74 has a mesh size of about 500 to 5000 μm, the first fine mesh filter 75 has a mesh size of about 100 to 200 μm, and the second fine mesh filter 76 has a mesh size of about 40 to 100 μm. However, the mesh size of the filter is not limited thereto. Further, the curtain wall type filter 74, the first fine mesh filter 75, and the second fine mesh filter 76 are preferably made of metal such as stainless steel, but the material thereof is not limited thereto. The detailed structures of the curtain wall type filter 74, the first fine mesh filter 75 and the second fine mesh filter 76 will be described in detail below in conjunction with fig. 5.

When the fine mesh filter filters the sewage, the radial flow multistage filtering device 70 allows the sewage to flow in a radial direction, so that the filtering speed is increased and thus the treatment efficiency is improved, compared to the conventional sedimentation tank. The radial flow multistage filtering apparatus 70 can also remove heavy objects such as stones and sand brought in from the sand settling chamber 60.

As shown in fig. 2 and 3, the sewage treatment system according to the present disclosure includes at least two radial flow multistage filtering devices 70. For example, the at least two radial flow multistage filter devices 7 comprise a first radial flow multistage filter device 71 and a second radial flow multistage filter device 72. When the filtration speed of the first radial flow multistage filter device 71 decreases due to clogging of the pores of its fine mesh filter, the sewage input from the grit chamber 60 to the first radial flow multistage filter device 71 is blocked at least during the cleaning of the first radial flow multistage filter device 71. At the same time, the second radial flow multistage filter device 72 is opened to receive the sewage input from the grit chamber 60 and during the cleaning of the first radial flow multistage filter device 71, the second radial flow multistage filter device 72 is responsible for filtering the sewage.

In a preferred embodiment of the present disclosure, when sewage corresponding to the amount of "1Q" is supplied, the operation time of the first radial-flow multistage filtering device 71 may be varied within a range of 3 to 10 hours, depending on the filtering capacity thereof. For example, when the sewage corresponding to the amount of "1Q" is generally treated by the first radial flow multistage filtering device 71 during sunny or dry weather, the design of the first radial flow multistage filtering device 71 may be such that the fine mesh filter thereof is pore-clogged after an interval of about 6 hours. Therefore, the first radial flow porous filter device 71 needs to be cleaned every 6 hours, with a cleaning time of about 20 to 40 minutes, depending on the filtering capacity of the filter device.

For example, according to the preferred embodiment, when the fine mesh filter of the first radial flow multistage filtering device 71 is clogged with pores and the first radial flow multistage filtering device 71 requires a washing time of about 30 minutes, the sewage feed stream from the grit chamber 60 is branched to the second radial flow multistage filtering device 72, and the second radial flow multistage filtering device 72 is operated for about 40 to 60 minutes to filter the sewage when the first radial flow multistage filtering device 71 is washed. When the cleaning of the first radial flow multistage filter device 71 is completed, the sewage feed stream from the grit chamber 60 is diverted back to the first radial flow multistage filter device 71.

In this case, the first radial flow multistage filter device 71 and the second radial flow multistage filter device 72 may be designed to have the same filter capacity or different filter capacities. When the first and second radial flow multistage filtering devices 71 and 72 have different filtering capacities, one of the first and second radial flow multistage filtering devices 71 and 72 must have a sufficient filtering capacity to treat the sewage in a period of time required for cleaning the other radial flow multistage filtering device. In the case where one of the two radial flow multistage filtration devices is designed to operate only during the period of time required to clean the other radial flow multistage filtration device, the overall footprint required for the wastewater treatment system may be reduced since the diameter of one of the radial flow multistage filtration devices may be relatively small.

When the first radial flow multistage filtering device 71 and the second radial flow multistage filtering device 72 have different filtering capacities, there may occur a case where an excessive amount of sewage exceeding "1Q" is supplied to the sewage treatment system. In this case, as shown in fig. 2 and 3, the sewage may be discharged into the natural water body after passing through the radial flow multistage filtering device 70 and the sterilizing bath 90.

On the other hand, in another preferred embodiment of the present disclosure, when the first radial flow multistage filtering device 71 is designed to treat sewage corresponding to the amount of "1Q" and pore clogging occurs after 6 hours of its operation, if an excessive amount of sewage exceeding the amount of "1Q" is supplied, the operation time of the first radial flow multistage filtering device 71 may be changed and the pore clogging period of the fine mesh filter may be shortened depending on the amount of supplied sewage.

For example, when there is a sewage inflow of 3Q or more, the operation time of the first radial-flow multistage filtering device 71 is reduced to about 2 hours or less. That is, the material having a large specific gravity, such as stone or sand, which flows out of the sand setting chamber 60 due to the excessively fast flow rate of the sewage, must be filtered by the radial flow multistage filtering device 71. Therefore, the operation time thereof will be set to about 2 hours, which is 1/3 of 6 hours required for the first radial-flow multistage filtering device 71 to process the amount of sewage equivalent to "1Q". That is, when there is a sewage inflow of 3Q, the first radial-flow multistage filtering device 71 is cleaned every 2 hours of operation, and the interval time (cleaning time) for cleaning the first radial-flow multistage filtering device 71 may be 20 to 40 minutes. For example, when about 30 minutes is required for cleaning, the second radial-flow multistage filtering device 72 is controlled to operate for about 40 to 60 minutes, and then the sewage feed stream from the grit chamber 60 is returned to the first radial-flow multistage filtering device 71.

In this case, the first radial flow multistage filter device 71 and the second radial flow multistage filter device 72 may be designed to have the same filter capacity or different filter capacities. When the first radial flow multistage filtering device 71 and the second radial flow multistage filtering device 72 have different filtering capacities, one of the first and second radial flow multistage filtering devices 71 and 72 must have a sufficient filtering capacity to treat the sewage in a period of time required for cleaning the other radial flow multistage filtering device. In the case where one of the two radial flow multistage filtration devices is designed to operate only during the period of time required to clean the other radial flow multistage filtration device, the overall footprint required for the wastewater treatment system may be reduced since the diameter of one of the radial flow multistage filtration devices may be relatively small.

Therefore, unlike the conventional sewage treatment technology, the present invention can realize the purification of sewage even when the load of the sewage amount is rapidly increased during rainfall by flexibly operating the cleaning cycle of the multistage filtering device. In addition, since the multi-stage filtration apparatus installed at the initial stage can remove a large amount of suspended solids and remarkably reduce BOD, a bioreactor, which is generally installed at the final stage, can be omitted. The bioreactor will be described in detail below.

Preferred embodiments of the multistage filtering apparatus used in the system of the present disclosure are disclosed in korean patent No. 10-1400313 entitled "water treatment plant" registered on 21.5.2014 and korean patent No. 10-0823240 entitled "maintenance method of initial rainwater sewage treatment plant" registered on 11.4.2008, which are incorporated herein by reference in their entireties for all purposes.

For example, a multi-stage filtering apparatus disclosed in Korean patent No. 10-1400313 is illustrated in FIG. 5 of the accompanying drawings. Fig. 5 is a partial cross-sectional view to illustrate the internal structure of a multi-stage filtration device 70 that occurs according to one implementation of the present disclosure.

The multistage filtering apparatus 70 according to the present embodiment includes: a concrete structure 13 having a substantial box shape and providing an inner space; a pretreatment unit provided in the concrete structure 13 and primarily treating the sewage introduced through the inlet pipe 17 while passing through; a filtering module 39 installed in the main treatment area 55 in the concrete structure 13 and separated from the pretreatment unit by a partition wall 27, the filtering module 39 receiving sewage from the pretreatment unit through a bottom surface thereof and secondarily treating the sewage by allowing the sewage to flow radially; a drain weir 53 for discharging the filtrate, which has passed through the filtering module 39, to the outside of the concrete structure 13 through the drain pipe 19; and a filtering and washing device 51 for washing the filtering module 39 when not in operation.

The concrete structure 13 includes a bottom portion 13 constructed on the ground of the excavated space to provide a horizontal supporting surface; a vertical wall portion 13a mounted to the edge of the bottom portion 13, and a top portion (not shown) disposed on top of the wall portion 13 a. The upper surface of the top portion of the structure may be covered with soil created by excavation.

The bottom 13b is provided with

recesses

13c and 13d on both sides thereof, respectively. The

recesses

13c and 13d provide space for the

pumps

15a and 15b, respectively.

A fixedly mounted water inlet pipe 17 extends through the wall portion 13a from the exterior to the interior of the concrete structure 13 and is a conduit for conveying contaminated water from the exterior to the interior of the structure 13. Polluted water is a generic term for various polluted waters, including initial rainfall runoff, sewage and wastewater containing non-point-source pollutants.

The pretreatment unit is composed of a first treatment unit 21 and a second treatment unit 29, and is partitioned by a partition wall 25. The pre-treatment unit may remove coarse particles having a predetermined size or more from the contaminants contained in the contaminated water.

For this purpose, the first treatment unit 21 is internally provided with a coarse screen 23. The coarse screen 23 is a hollow basket-shaped member made of a metal mesh for filtering out various debris introduced through the inlet pipe 17 together with contaminated water. Such debris includes, for example, butts, leaves, trash, etc. floating on the water.

The inner space where the coarse screen 23 is installed is a vertical passage and is opened toward the pit 13c at the bottom thereof, and the coarse screen 23 is spaced from the inner wall surface of the first treating unit. Therefore, even if the inside of the coarse screen 23 is crowded with the collected debris so that the contaminated water is not smoothly discharged from the coarse screen 23, there is no fear that the contaminated water may flow back through the water inlet pipe 17 since the contaminated water may flow out from the gap between the outer surface of the coarse screen 23 and the inner wall surface of the concrete structure.

After passing through the coarse screen 23, the contaminated water flows into the second treatment unit 29 through the lower part of the partition wall 25.

The second treatment unit 29 directs the upward flow of contaminated water through the coarse screen 23 and screens out solids smaller than the debris removed by the coarse screen. The second treatment unit 29 consists of three screens 31. The screen 31 is a plate-shaped member having a plurality of perforations (not shown) arranged at different heights in the vertical direction.

The mesh 31 is produced by press working, which means pressing a stainless steel plate into a desired shape. The screen 31 is corrugated with mutually parallel ridges and grooves. The top of each ridge and the bottom of each groove have a plurality of perforations (not shown). The three screens 31 have different sized perforations.

For example, the lowermost screen 31 has the largest perforations (not shown) and the uppermost screen 31 has the smallest perforations.

The corrugated shape of the screen 31 provides the advantage of preventing clogging of the perforations (not shown).

The diameter of each perforation (not shown), the number of perforations formed in each screen 31, or the number of screens 31 may vary. The mesh 31 may be produced by a synthetic resin molding process.

The pump 15a installed in the pit 13c under the first and second treating

units

21 and 29 functions to pump contaminated water stagnating in the first and second treating

units

21 and 29 out of the concrete structure 13 through the outflow pipe 16 when the input of sewage is stopped. The function of the pump 15a also includes pumping out the cleaned water for cleaning the first and second treating

units

21 and 29.

The contaminated water treated by the second treatment unit 29 flows through the weir 27a and enters the main treatment zone 55 through the draft tube 33, wherein the weir 27a is located at the top of the partition wall 27.

Conduit 33 is a vertical conduit that receives contaminated water flowing through weir 27a and directs the contaminated water to flow downwardly for introduction into inlet conduit 35.

The primary treatment zone 55 is a water tank in which treated water passing through the filtration module 39 is temporarily collected. The treated water collected in the main treatment zone 55 is guided to flow over the drainage weir 53 and then discharged to the outside of the concrete structure through the drainage pipe 19.

The drain weir 53 is a member for guiding the treated water in the main treatment zone 55 toward the drain pipe 19. A drain weir 53 is fixed to the wall of the main treatment zone 55.

Drain weir 53 is formed at a position lower than the top of second fine mesh filter 45 to be described later. In other words, the height of an imaginary horizontal line extending from the top of the second fine mesh filter 45 is higher than the upper end of the drain weir 53 by a certain value H, so that the water passing through the filter module 39 easily flows over the drain weir 53. The H value depends on the scale or desired capacity of the water treatment system.

The main treatment zone 55 is internally provided with a water inlet pipe 35 which laterally guides the contaminated water conveyed through the draft tube 33 and has a vertically extending portion; a guide diffuser (guide diffuser)37 fixed to one end of the vertically extending portion of the inlet pipe 35; a support plate 49 fixed to the upper end of the guide diffuser 37; a filter module 39 supported on a support plate 49; and a filtering and cleaning device 51 installed above the filter module 39 to backwash the filter module 39.

The guiding diffuser 37 is a funnel-shaped member fixed at its lower end to the inlet tube 35. The pilot diffuser 37 receives the contaminated water through the inlet pipe 35 and directs the contaminated water to the filter module 39. In particular, since the inlet pipe 37 is tapered, the inner diameter thereof becomes larger from the lower end to the upper end. Thus, as the contaminated water is directed by the guide diffuser 37, the contaminated water flow is gradually slowed while the contaminated water flows upward in the main treatment zone. Therefore, the contaminated water is brought into a static state at the surface layer thereof, so that the contaminated water can be easily filtered by the filter module 39.

The support plate 49 fixed to the upper end of the guide diffuser 37 is a horizontal member for supporting the upper filter module 39. The support plate 49 blocks the lower end of the filter 39 to prevent contaminated water from flowing down, so that the contaminated water can flow radially.

The inner space and the outer space, which are connected by the upper ends of the guide diffuser 37 and the support plate 49 and the inner wall of the second fine mesh filter 45, are a contaminated area and a clean area, respectively. The contaminated zone is a space for containing untreated contaminated water and contaminants, and the clean zone is a space for containing treated water.

In addition, the support plate 49 is provided with two drain holes (not shown) and a drain valve (not shown). The drain hole is opened and closed through the door plate. When the filter module 39 is cleaned, the drain hole is opened.

Filter module 39 is secured to the top surface of support plate 49) and purifies the contaminated water flowing upward through the guide diffuser 37 by allowing the contaminated water to flow radially therethrough.

The filter module 39 includes a curtain wall filter 41 having a cylindrical shape and a predetermined thickness, a cylindrical mesh filter 47 installed in the curtain wall filter 41 as a frame, a first fine mesh filter 43 installed outside the curtain wall filter, and a second fine mesh filter 45 installed outside the first fine mesh filter 43.

The mesh filter 47, the curtain wall type filter 41, and the first and second fine mesh filters 43 and 45 are different in diameter but the same in center. That is, the filters are arranged in a concentric circular pattern when viewed from above. The height of the first fine-mesh filter 43 is smaller than that of the curtain wall type filter 41, and the height of the second fine-mesh filter 45 is smaller than that of the first fine-mesh filter 43.

The curtain wall type filter 41, the first fine mesh filter 43 and the second fine mesh filter 45 are designed to have different heights in order to cope with the clogging problem of the filters. In other words, when the

filters

41, 43, 45 are clogged in a certain area, the water overflows the curtain wall type filter 41, then overflows the first fine mesh filter 43, and finally overflows the second fine mesh filter 45, thereby being discharged to the outside of the filtering apparatus.

The fibrous media may be installed in a curtain wall filter 41. The fiber media is a filter media made of fibers for filtering contaminants contained in contaminated water. In particular, the fibrous media includes low density fibrous media, medium density fibrous filter media, and high density fibrous filter media layered in that order from the inside out, spaced apart from one another. The thicker the overall thickness of the curtain wall filter 41, the higher the filtration efficiency.

The first fine mesh filter 43 has smaller pores than the curtain wall filter 41. The first fine mesh filter 43 filters out contaminants passing through the curtain wall filter 41.

The contaminants passing through the first fine mesh filter 43 are filtered by the second fine mesh filter 45. The second fine mesh filter 45 has a denser structure than the first fine mesh filter 43, and filters out contaminants at the end. The water passing through the second fine mesh filter 45 is treated water, wherein the concentration of contaminants is below a threshold value, which fills a main treatment zone 55 arranged outside the filter module 39, flows over a drain weir 53 and is discharged to the environment through the drain pipe 19.

In the process of treating contaminated water through the above process, when the inflow of sewage is stopped, the treated water in the main treatment zone 55 cannot flow through the drain weir 53 but stays in the main treatment zone 55.

In this case, the treated water remaining in the main treatment zone 55 will be pumped out of the concrete structure 13 through a treated water discharge pipe (not shown) by operating a pump (not shown) in the pit 13 c. The pumping may continue until the bottom portion 13b is completely exposed.

Furthermore, a filter cleaning device 51 for backwashing the filter module 39 is mounted above the filter module 39. When the main treatment zone 55 is empty, the filter cleaning device 51 will be operated. For example, when rainfall ends or at a dry season, the filter cleaning device 51 operates to clean the filter module 39.

In particular, the filter washing device 51 is rotated with the aid of a reaction force corresponding to a spray pressure of washing water sprayed through a nozzle (not shown), and sprays the washing water toward the entire structure of the filter module 39 while circling over the filter module unit 39. The washing water is supplied to the filter module through the washing water supply pipe 51 a.

According to the present disclosure, bioreactor 81 may not be used, as shown in fig. 2. As the wastewater passes through the radial flow multi-stage filtration apparatus 70 according to the present disclosure, suspended solids and BOD material are greatly reduced. Therefore, the membrane filter of the membrane filtration device 82 can be used to remove the remaining suspended solids and microorganisms without using the bioreactor 81.

In accordance with the present disclosure, the radial flow multi-stage filtration device 70 significantly removes suspended solids from the wastewater, thereby greatly reducing the BOD of the wastewater. Therefore, even if the membrane filtration device 82 is used for a long period of time, the problem of membrane clogging does not occur. As described above, since the sewage treatment system employs a physical process to treat sewage, not a biological process, the sewage treatment system can be continuously and continuously operated, so that the treatment efficiency can be continuously maintained even in rainy weather.

Further, as shown in fig. 3, the sewage treatment system according to the present disclosure may be a combined treatment system in which a bioreactor 81 and a membrane filtration device 82 or a sedimentation tank 83 may be combined as a post-treatment stage. In the case where the microorganism in the bioreactor 81 is maintained at a high concentration, it is possible to improve the removal rate of organic matter and nitrogen. In addition, suspended solids and microorganisms are removed by the membrane filtration unit 82. Alternatively, suspended solids, microorganisms and/or sludge are settled and removed in the settling tank 83. In addition, the bioreactor 81 may be a membrane bioreactor, wherein the bioreactor and the membrane filtration device are integrated. In this case, the membrane bioreactor is a device for removing organic matter, nitrogen and microorganisms. Bioreactor 81 may be replaced with any existing device that can remove organic matter, nitrogen, and microorganisms.

The sterilizing bath 90 serves to sterilize the sewage at the final stage of the purification of the sewage. The disinfection can be achieved by, for example, adding chlorine, and the disinfection tank 90 is responsible for performing the final stage of the sewage purification.

Hereinafter, the present disclosure will be described in more detail with reference to examples and comparative examples, but the scope of the present disclosure is not limited by the following examples.

Comparative example 1

In dry seasons, the sewage stays in a grit chamber of a conventional sewage treatment system consisting of a grit chamber, a primary sedimentation tank, a bioreactor, a secondary sedimentation tank and a disinfection tank for 20 minutes, as shown in fig. 1. Thereafter, the sewage is supplied to the primary sedimentation tank. The primary settling tank, bioreactor and secondary settling tank were operated under the conditions shown in table 1.

[ Table 1]

Example 1

In dry seasons, sewage was treated in a sewage treatment system which was different from the conventional sewage treatment system used in comparative example 1 only in that the primary settling tank was replaced with 16 radial flow multistage filtering devices and the secondary settling tank was replaced with a membrane filtering device. The other elements were the same as in comparative example 1, and the wastewater was treated under the conditions shown in Table 2. The curtain wall filter 41 of the radial flow multistage filter device is provided with a fibrous media embedded therein. The curtain wall type filter 41 has a mesh size of about 1000 μm, the first fine mesh filter 43 has a mesh size of about 140 μm, and the second fine mesh filter 45 has a mesh size of about 74 μm. Of the 16 radial flow multistage filtering apparatuses, 15 radial flow multistage filtering apparatuses were operated simultaneously to treat sewage, and one radial flow multistage filtering apparatus was used during cleaning.

[ Table 2]

As shown in tables 1 and 2, the floor space and retention time were greatly reduced. Suspended Solids (SS) removal rate and BOD removal rate were measured from the treated water sampled from a position downstream of the primary settling tank in comparative example 1 and the treated water sampled from a position downstream of the radial flow multi-stage filtration apparatus in example 1. The results prove that the SS removal rate and the BOD removal rate are obviously improved. The results are summarized in table 3.

[ Table 3]

SS removal rate according to Korea environmental division No. 2004-188 bulletin ¹⁾ Detection using the official water pollution test method as specified in chapter 4, paragraph 8 of the test method; BOD removal Rate according to Notice No. 2004- ²⁾ The test was carried out using the test method specified in chapter 4, paragraph 5 of the official water pollution test methods.

Comparative example 2

In rainy season, sewage was treated in a conventional sewage treatment system consisting of a grit chamber, a primary settling tank, a bioreactor, a secondary settling tank and a sterilizing tank as shown in FIG. 1 under the conditions shown in Table 4. In this embodiment, the amount of sewage supplied to the primary settling tank is 3Q. In the present comparative example, when 3Q sewage was supplied, 1Q sewage was sent to the sewage treatment system, and 2Q sewage was discharged to a nearby natural water body through the disinfection tank without being subjected to other treatment processes.

[ Table 4]

Example 2

In rainy season, under the conditions shown in table 5, sewage was treated in the same manner as in example 1. In this embodiment, 3Q sewage is supplied to the sewage treatment system. In this embodiment, the flow rate of sewage is maintained at 3Q. The sewage of 1Q is sent to a post-treatment stage of a sewage treatment system, and the sewage of 2Q is discharged into a natural water body through a disinfection tank. As shown in table 5, this example exhibited higher processing efficiency than comparative example 2. In the present embodiment, the cleaning cycle of each radial flow multistage filtering apparatus is shortened, so that 3Q of sewage can be treated.

[ Table 5]

As shown in tables 4 and 5, the required field area and the stay time in rainy season are greatly reduced. The SS removal rate and BOD removal rate were measured in the treated water sampled from a position downstream of the primary settling tank of comparative example 2 and the treated water sampled from a position downstream of the radial flow multi-stage filtration apparatus of example 2. The results are summarized in table 6.

[ Table 6]

Parameter(s)	Comparative example 2	Example 2	Remarks for note
				Floor area	2,500m ²	1638m ²	The reduction is about 35 percent
Residence time	0.8 hour	0.4 hour	The reduction is about 50 percent
				Total residence time	About 11.6 hours	About 9.2 hours	The saving is about 21 percent
SS removal Rate (%)	About 10	About 80	Increase by about 70% P
				BOD removal Rate (%)	About 5	About 50	Increase by about 30% P

According to the Korean environmental ministry No. 2004- ¹⁾ Detection using the official water pollution test method as specified in chapter 4, paragraph 8 of the test method; BOD removal Rate according to Notice No. 2004- ²⁾ Official water pollution testing partyChapter 4, paragraph 5 of the method.

Example 3

The sewage was treated under the conditions shown in Table 7, and the sewage treatment system of comparative example 1 and the sewage treatment system comprising the grit chamber shown in FIG. 3, the radial flow multi-stage filtration device, the membrane filtration device and the disinfection tank, which are the same as those used in example 1, were compared.

[ Table 7]

According to the data shown in Table 8, the required field area and the sewage retention time of comparative example 1, comparative example 2 and example 3 were compared, and the comparison results showed that the required field area and the sewage retention time were both greatly reduced.

[ Table 8]

Although the present invention has been described with reference to preferred embodiments for the purpose of clarity of understanding, the preferred embodiments are for the purpose of describing the technical essence of the present invention, and it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit or scope of the present invention.

All such simple modifications and variations of the present invention are within the scope of the present invention, the particular scope of the present invention being clearly defined by the appended claims.

[ description of reference numerals in the drawings ]

10,100 sewage treatment system

1,60, a sand setting chamber;

2: primary sedimentation tank

3,81 bioreactor

4: two-stage sedimentation tank

4',82 Membrane filtration device

5,90 sterilizing groove

70 radial flow multistage filtering device

71 first radial flow multistage filtration device

72 second radial flow multistage filtration device

73 radial flow multistage filter unit

41 or 74 curtain wall type filter:

43 or 75 first Fine-mesh Filter

45 or 76 second fine-mesh filter

Claims

1. A wastewater treatment system for maximizing treatment of combined drainage pipeline overflows (CSOs) during treatment of the CSOs, the wastewater treatment system comprising:

the sand setting chamber is used for preliminarily removing foreign matters in the sewage to be treated;

at least two radial flow multistage filtering devices, each device being designed to allow the sewage passing through the grit chamber to flow radially outward from the center thereof for filtering;

a membrane filtration device using a membrane filter to filter the sewage passing through the radial flow multistage filtration device; and

and the disinfection tank is used for disinfecting the treated sewage discharged from the membrane filtering device or the sedimentation tank.

2. A wastewater treatment system for maximizing treatment of combined drainage pipeline overflows (CSOs) during treatment of the CSOs, the wastewater treatment system comprising:

at least two radial flow multistage filtration devices, each designed to allow the sewage passing through the grit chamber to flow radially outward from the center thereof for filtration;

and the bioreactor is used for removing organic matters, nitrogen and microorganisms in the sewage passing through the radial flow multistage filtering device.

A membrane filtration device that filters the sewage passing through the bioreactor using a membrane filter, or a settling tank that allows suspended solids and organic matter to settle to the bottom; and

and a sterilizing tank for sterilizing the treated sewage discharged from the membrane filtering device or the sedimentation tank.

3. The sewage treatment system according to claim 1, wherein the maximum sewage treatment capacity of the sewage treatment system is 1Q when sewage passes through the grit chamber, the radial flow multistage filtration device, the membrane filtration device and the disinfection tank in this order, and the radial flow multistage filtration device allows a portion of the supplied sewage corresponding to 1Q to be introduced into the membrane filtration device and the remaining portion of the supplied sewage to be introduced into the disinfection tank when the amount of sewage supplied to the sewage treatment system exceeds 1Q.

4. The sewage treatment system according to claim 2, wherein when the sewage passes through the grit chamber, any one of the radial flow multistage filtering device, the bioreactor, the membrane filtering device and the sedimentation tank, and the disinfection tank in this order, a maximum sewage treatment amount of the sewage treatment system is 1Q, and when an amount of the sewage supplied to the sewage treatment system exceeds 1Q, the radial flow multistage filtering device allows a portion of the supplied sewage corresponding to 1Q to pass through any one of the bioreactor, the membrane filtering device and the sedimentation tank, and the disinfection tank in this order, and the remaining portion of the supplied sewage directly flows into the disinfection tank.

5. The sewage treatment system according to claim 1 wherein the radial flow multistage filtering device is comprised of at least three cylindrical fine mesh filters having different diameters and arranged concentrically, and the mesh sizes of the fine mesh filters are gradually decreased from the innermost fine mesh filter to the outermost fine mesh filter.

6. The sewage treatment system of claim 2, wherein the radial flow multistage filtering device is composed of at least three cylindrical fine mesh filters having different diameters and arranged concentrically, and the mesh sizes of the fine mesh filters are gradually decreased from an innermost fine mesh filter to an outermost fine mesh filter.

7. The wastewater treatment system of claim 1, wherein the at least two radial flow multistage filtering devices have the same treatment capacity or have different treatment capacities, wherein, when the filtering speed of one of the at least two radial flow multistage filtering devices is decreased due to clogging of pores of its fine mesh filter, another radial flow multistage filtering device is used to filter wastewater at least for a period of time during cleaning of the clogged radial flow multistage filtering device.

8. The wastewater treatment system of claim 2, wherein at least two radial flow multistage filtration devices have the same treatment capacity or have different treatment capacities, wherein when the filtration rate of one of the at least two radial flow multistage filtration devices is reduced due to clogging of pores of its fine mesh filter, another radial flow multistage filtration device is used to filter wastewater at least for a period of time during cleaning of the clogged radial flow multistage filtration device.