CA2771637A1

CA2771637A1 - Apparatus for treating wastewater

Info

Publication number: CA2771637A1
Application number: CA 2771637
Authority: CA
Inventors: Hong Bok Choi
Original assignee: EcoDays Co Ltd
Current assignee: EcoDays Co Ltd
Priority date: 2011-08-12
Filing date: 2012-03-12
Publication date: 2013-02-12
Also published as: KR20130017962A

Abstract

A sewage and wastewater treatment apparatus in which a pretreatment unit and a main treatment unit are connected to each other in an integrated process is disclosed. The apparatus includes: a pretreatment unit separating low density material from the sewage and wastewater using a low-density material separation; a storage tank storing the sewage and wastewater supplied from the pretreatment unit;
and a main treatment unit treating the sewage and wastewater supplied from the storage tank in anaerobic digestion to produce methane gas such that fine bubbles are transformed into big bubbles during the ascending of the methane gas and that agitation of the sewage and wastewater is carried out.

Description

APPARATUS FOR TREATING WASTEWATER

BACKGROUND OF THE INVENTION
Field of the Invention The present invention relates generally to an apparatus for treating sewage and wastewater, and more particularly, to an apparatus for effectively treating high density sewage and wastewater by which a low density material separation type pretreatment process and an anaerobic digestion main treatment process are combined into a single process such that the low density materials contained in sewage and wastewater are separated using density difference in the pretreatment process and that agitation and solid-liquid separation are carried out by anaerobic digestion in the main treatment process.

Description of the Related Art In general, treatment of sewage and wastewater is to eliminate harmful material and pollution from sewage and wastewater discharged from plants and offices.

The treatments may be classified into a physical treatment, a chemical treatment, a biological treatment, a thermal treatment, and an advanced oxidation process (AOP) according to kinds and types of sewage and wastewater.

The sewage and wastewater treatment process includes a pre-treatment process of treating sewage and wastewater primarily and a main treatment process of secondarily treating the pre-treated sewage and wastewater.

The pre-treatment process performs an important role of enhancing efficiency of the main treatment process.
In the pre-treatment process, oil component, various fruit seeds, various foods that are dissolved slow, indecomposable vinyl are pre-treated.

Thus, sewage and wastewater is primarily decomposed in the pre-treatment process and may be transformed into organic material to be easily treated in the main treatment process.

During the main treatment process, the sewage and wastewater transformed into organic material during the pre-treatment process is treated by anaerobic digestion.

However, the existing pre-treatment process has drawbacks. That is, an existing pre-treatment unit does not have a function of selecting and separating low density material and very-slowly-decomposing material of which particle solids are introduced into the pre-treatment unit is introduced into the main treatment process without pre-treatment so that the main treatment process may be excessively increased to treat such material and treatment efficiency may be remarkably deteriorated.

Even in the main treatment process, since the sewage and wastewatertreatedinthe pre-treatment process contains various materials such as low-density fat and oil, non-decomposable wastewater sludge, easily-decomposable solids (foods) , it is very difficult to build an anaerobic digester satisfying all decomposition conditions for the respective materials.

Thus, a completely mixed flow reactor anaerobic digester employed in the existing main treatment process is designed by assuming that features of all materials of sewage and wastewater are under the same conditions.
That is, since the completely mixed flow reactor anaerobic digester is designed and driven based on a material having the longest decomposing time for increase of efficiency, low density organic matters and microorganisms exist in the anaerobic digester so that efficiency of the anaerobic digestion is very low.

Moreover, since it is substantially impossible to cope with the existing anaerobic digestion (long treatment time, low generation of methane, and increase of post-treatment costs due to a lot of staying material after the anaerobic digestion) against the situation where the existing mostly-used disposal of waste is completely banned under the marine dumping ban, solutions of radically solving this problem are required.

Upf lowAnaerobic Sludge Blanket (UASB) maybe a typical method among the solutions.

However, UASB has difficulties on mixing, securing of microorganism, big scale apparatuses, management of rapid drop of pH, especially cannot cope with treat introduced solid material, and thus has limit on efficiency.

In addition, since the anaerobic digestion is used just to reduce pollutants from sewage and wastewater, the problem of low efficiency is solved through a rear side water treatment or by spraying sewage and wastewater on soil.

However, since recently methane is spotlighted as alternative energy and has an important impact on global warming, increase amount and use of methane in organic material directly mean to increase production of energy and to protect environment.

Thus, technology of increasing production of methane from organic material as much as possible to make the rear side water treatment and staying solid treatment be easy should be required. However, it is difficult to achieve this purpose yet.

SUMMARY OF THE INVENTION

The present invention has been made in view of the aboveproblem,andthepresentinventionprovidesanapparatus for treating sewage and wastewater by applying low density separation method to a pretreatment process to separate low density fat and oil components, organic material, and suspended matter from sewage and wastewater, by decomposing pollutants with organic acid to accelerate a following anaerobic digestion, and by applying anaerobic digestion in a main treatment process to convert the fat and oil introduced from the pretreatment process into digestion gas without separation.

In accordance with the aspects of the present invention, there is provided an apparatus for treating sewage and wastewater, including: a pretreatment unit separating low density material from the sewage and wastewater using a low-density material separation; a storage tank storing the sewage and wastewater supplied from the pretreatment unit;
and a main treatment unit treating the sewage and wastewater supplied from the storage tank in anaerobic digestion to produce methane gas from the sewage and wastewater such that stayed time of the methane gas is increased during the ascending of the methane gas and that agitation of the sewage and wastewater is carried out.

As described above, the apparatus for treating sewage and wastewater according to the present invention has the following advantages.

First, since the pretreatment process using the low density material separation and the main treatment process usingtheanaerobicdigestionareintegratedintooneprocess, the lowdensitymaterialcontainedinthesewageandwastewater is separated in the pretreatment process due to density difference and the agitation and the solid-liquid separation are carried out by the anaerobic digestion in the main treatment process so that high concentration sewage and wastewater may be effectively treated.

Second, in the pretreatment unit, since the low-density 1o material separators are disposed in multiple layers in the first reactor, the stay chambers are formed in the lower side of the low-density material separator by the sewage and wastewater, and the low density material floats on the water surface within the stay chambers and are not discharged with the sewage and wastewater when the sewage and wastewater is discharged, the low density material such as fat and oil component of the sewage and wastewater maybe easily separated before the main treatment and may be decomposed organic acid to accelerate following anaerobic digestion so that the fat and oil component is transformed into digestion gas without being separated independently.

Third, in the pretreatment unit, since gas is supplied or discharged through the gas pipes connected to the stay chambers to control the water level within the stay chambers, the low density material may be removed more effectively.

Fourth, in the main treatment unit, the first and second activating devices with different shapes are arranged in the second reactor. The stay chambers for gas are formed in the first and second activating devices. The gas generated from the ascending sewage and wastewater is gathered in the stay chambers and ascends through the transfer pipes sequentially. During this ascending, since the lower sides of the transfer pipes contact the water surface, the low density material on the water surface is transferred into the upper chamber and the solids under the water surface remain so that the solid-liquid separation is carried out.
Fifth, in the main treatment unit, when the gas and the sewage and wastewater ascend additionallyandpass through the anaerobic reaction activating devices, the gas is discharged from the lower chamber spontaneously to form a space and high density material such as the solids and microorganism requiring a longer decomposing time are introduced into the space so that the high density material is transferred into the lower chamber as much as the amount of the discharged gas resulting in improving treat rate and efficiency.

Sixth, in the main treatment unit, the gas gathered in the lower chamber of the second reactor is discharged such that the sewage and wastewater drops from the upper chamber to the lower chamber, resulting in agitating without driving power. Simultaneously, solids and microorganisms are transferred into the lower chamber to prevent pH from being decreased in the lower chamber.

Seventh, in the main treatment unit, since it is substantially impossible to observe the internal side of the reactor and to cope with a trouble because the anaerobic digestion treats very highconcentrated sewage and wastewater, the apparatus of the present invention prevents trouble from occurring fundamentally by repeating processes such as the agitation by the gas transfer, the agitation by discharging gas, and fluidity caused by gas stay.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, features and advantages of the present invention will be more apparent from the following detailed description in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic view illustrating an apparatus for treating sewage and wastewater including a pretreatment unit, a storage tank, and a main treatment unit according to an exemplary embodiment of the present invention;

FIG. 2 is a side view illustrating an internal structure of the pretreatment unit of FIG. 1;

FIG. 3 is a partially-enlarged view of a transfer pipe of the apparatus for treating sewage and wastewater of FIG.

2;

FIG. 4 is a side sectional view schematically illustrating an internal structure of a second reactor of the main treatment unit of FIG. 1;

FIG. 5 is a perspective view of a first plate activating unit in the second reactor of FIG. 4;

FIG. 6 is a view partially illustrating gas gathered in a first stay chamber ascending through the first activating unit of FIG. 5;

FIG. 7 is a perspective view a second block activating unit of FIG. 4;

FIG. 8 is a side view schematically illustrating the gas gathered in the first stay chamber ascending through the second activating devices of FIG. 7; and FIG. 9 is a section view showing another example of the main treatment unit of FIG. 4 in which a gas circulation unit is additionally disposed to a side of the second reactor.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, an apparatus for treating sewage and wastewater according to exemplary embodiments of the present invention are described in detail with reference to the accompanying drawings.

As illustrated in FIG. 1, an apparatus 1 for treating sewage and wastewater according to an exemplary embodiment of the present invention includes a low-density material separation type pretreatment unit 2, a storage tank 3 for storing treated water supplied from the pretreatment unit 2, and a main treatment unit 4 for treating the treated water supplied from the storage tank 3 in anaerobic digestion to produce methane gas from the sewage and wastewater such that stayed time of the methane gas is increased during the ascending of the methane gas and that agitation of the sewage and wastewater is effectively performed.

In the apparatus, the pretreatment unit 2 removes particle solids contained in the high concentration sewage and wastewater in the low-density material separation, pre-treats the removed particle solids to be fed to the main treatment unit 4.

The pretreatment unit 2, as illustrated in FIGS. 2 and 3, includes a first reactor 5 in which the sewage and wastewater is introduced into to be treated and discharged out, an agitator 7 provided in the first reactor 5 to agitate and uniformly mix up the sewage and wastewater and bubbles, at least one low-density material separator 9 dividing an internal space of the first reactor 5 into upper and lower chambers, allowing the ascending sewage and wastewater and a gas to pass therethrough sequentially such that low density material floats on the water surface within a stay chamber V due to the bubbles generated from the sewage and wastewater introduced during the ascending or a gas injected thereinto from the outside, and controlling a level of the water surface to prevent the low density material floating on the water surface from ascending such that the low density material is separated from the sewage and wastewater, and a particle solid discharging pipe 11 disposed near the water surface formed at the lower side of the low-density material separator for discharging the low density material floating the water surface W to the outside when the water level of the stay chamber V descends.

In this apparatus for treating sewage and wastewater, the sewage and wastewater may be introduced into and stored in the tank-shaped first reactor 5.

That is, the first reactor 5 includes a wastewater introducing pipe 13 connected to the lower side thereof such that the sewage and wastewater is supplied into the first reactor 5 the wastewater introducing pipe 13.

The sewage and wastewater introduced through the wastewater introducing pipe 13 fills up the internal space of the first reactor 5 by gradually ascending from the bottom .

During this process, sludge with a preset weight or heavier contained in the sewage and wastewater is deposited in a precipitation tank.

A gas pipe 15 is connected to a side of the first reactor 5. The gas pipe 15 is communicated with the stay chamber V to discharge the gas gathered by the low-density material separator 9 to the outside or to inject an external gas into the stay chamber V.

The first reactor 5 includes a treated water discharging pipe 17 connected to the upper side to discharge the water treated while passing through the low-density material separator 9 to the storage tank 3.

The first reactor 5 includes a deposit discharging pipe 19 connected to the lower side to condense and discharge the deposits, so that the deposits deposited from the upper side in the first reactor may be discharged along a slope to the deposit discharging pipe 19.

The agitator 7 includes a motor assembly M disposed on the top of the first reactor 5 and an impeller B mounted around a rotating shaft S of the motor assembly M.

In this case, the impeller B may be mounted around the lower side of the rotating shaft S and may be disposed under the uppermost water surface W1.

Sizeandnumberof the impeller Bmaybeproperlyselected according to treatment capacity of the first reactor 5.
When the motor assembly M is driven, the impeller B

may rotate and mix up the sewage and wastewater full in the first reactor 5 uniformly.

The low-density material separator 9 includes a single or a plurality of low-density material separators.

In more detail, the low-density material separator 9 includes a blocking plate 21 dividing the internal space of the first reactor 5 into the upper and lower chambers and formed with a plurality of passing holes h, and a plurality of transfer pipes 23 protruding downwardly from the lower sideof the blocking plate2landcommunicatedwiththepassing holeshsuchthatthesewageandwastewaterflowstherethrough.

In the low-density material separator 9, the blocking plate is made of a thin plate and is disposed transversally in the first reactor 5 to divide the internal space of the first reactor 5 into the upper and lower chambers.

Thus, the sewage and wastewater filled in the lower side of the blocking plate 21 may move to the upper side of the blocking plate 21 only when passing through the passing holes handthe transferpipes 23 communicated with the passing holes h.

Since the transfer pipes 23 have internal passages, the sewage and wastewater may be transferred to the upper and lower chambers through the transfer pipes 23.

At least one of the transfer pipes 23 protrudes downwardly from the blocking plate 21 by a preset length.
When the first reactor 5 is filled with the sewage and wastewater, the water surface W is formed and gradually ascends and finally reaches the lower ends of the transfer pipes 23 so that the stay chambers V are formed by the blocking plate 21, the outer rims of the transfer pipes 23, and the water surface W.

In this case, the water surface W is formed on the same line as the lowermost ends of the transfer pipes 23.
Thus, when the stay chamber V is additionally filled with gas generated from the sewage and wastewater or an external gas is additionally injected through the gas pipe 15, the water level descends and the sewage and wastewater move to the lower side of the transfer pipes 23 and finally ascend into the upper chamber through the transfer pipes 23.

At this time, the sludge floating on the water surface W, especially, low density materials such as scum, oil component, and fruit seeds are filtered by the lower rims of the transfer pipes 23 and thus prevented from moving to the upper chamber together with the ascending sewage and wastewater. Thus, the low density material is separated from the sewage and wastewater.

Moreover, as illustrated in FIG. 3, at the lower rims of the transfer pipes 23 filters 25 are formed.

The filters 25 may filter the sludge floating on the water surface W, especially scum, oil component, and fruit seeds more effectively.

The low density materials are not discharged and float on the water surface W fora long time so that time for natural decomposition may be secured and only decomposed material may be transferred into the upper chamber.

Meanwhile, on the water surface formed in the stay chamber, the water level descend as the gas generated from the sewage and wastewater is gathered in the stay chamber V or the amount of the external gas injected into the stay chamber V through the gas pipe 15 is increased.

The water level descends to the same height as that of an inlet 27 of a particle solid discharging pipe 11. In this case, material with relatively low density of the low densitymaterial floating on the water surface W is discharged to the outside through the inlet 27 of the particle solid discharging pipe 11 except for material with relatively high density so that the accumulation of the low density material is decreased.

Thus, the relatively-low density material is discharged through the particle solid discharging pipe 11 and the relatively-high density material resides on the water surface so that the secondary separation is performed.

On the contrary, when a valve 6 of the gas pipe 15 is open, the gas gathered in the stay chamber V is discharged out so that a pressure of the stay chamber V is decreased and the water surface W ascends so that the accumulation of the low density material is also increased.

In this case, the water surface W is formed above the particle solid discharging pipe 11 so that the low density material is not discharged out through the particle solid discharging pipe 11 but floats on the water surface W for a long time resulting in disintegrating organically.

Therefore, the valve 6 of the gas pipe 15 is properly controlled such that the low density material may be effectively separated by adjusting the level in the stay chamber V or through the biological treatment of floating the low density material for a long time to be decomposed.

During the above-mentioned process, high density material of the foreign matter contained in the sewage and wastewateraredepositeddownandforeign matterofrelatively low density floats on the water surface W in the stay chamber V around the transfer pipes 23 resulting in being decomposed.

The low density material floating on the water surface W may be removed secondarily by which the low density material is discharged through the particle solid discharging pipe 11 to the outside when the level reaches the height of the particle solid inlet 27.

In more detail, the particle solid discharging pipe 11 includes the inlet 27 throughwhichthe low densitymaterial is introduced and an outlet 29 through which the introduced low density material is discharged.

The inlet 27 has a large sectional area such that the low density material floating on the water surface W may be easily introduced into the particle solid discharging pipe 11. On the contrary, the outlet 29 has a sectional area less than that of the inlet 27 so that the low density material may be effectively discharged.

The inlet 27 is lower than the water surface W and higher than the lowermost ends of the transfer pipes 23.
Thus, when the level descends and reaches the height of the inlet 27, the low density material such as scum, oil, etc. floating on the water surface W enters the inlet 27 and is discharged through the outlet 29 to be removed secondarily.

The uppermost particle solid discharging pipe 35 of the particle solid discharging pipe 11 is configured such that an inlet 33 is disposed near the uppermost water surface Wl and an outlet 31 extends out of the first reactor 5 and is connected to the lower side of the first reactor 5.
Thus, since the low density material such as scum, oil component, and fruit seed enters the inlet 33 of the particle solid discharging pipe 35 and returns back to the lower side of the first reactor 5 through the outlet 31 even when the low density material floats on the uppermost water surface Wl, the low density material still resides in the first reactor 5 and is prevented from being transferred to the main treatment unit 4.

Meanwhile, the high density material of the sludge contained in the sewage and wastewater is deposited down and is accumulated on the bottom of the first reactor 5.
The deposited high density material is discharged to the outside through the deposit discharging pipe 19.

The operations of the pretreatment unit 2 will be described as follows.

As illustrated in FIGS. 2and3, the sewage and wastewater is introduced into the first reactor 5 through the wastewater introducing pipe 13 and the gas injection pipe 15.

The sewage and wastewater introduced into the f irst reactor 5 ascends and reaches the lower sides of the transfer pipes 23 of the first low-density material separator 9.

As a result, the water surface W of the sewage and wastewater is formed on the same line as that the lower sides of the transfer pipes 23 and the stay chambers V are formed around the transfer pipes 23 so that the gas generated from the sewage andwastewaterandinjectedfromtheoutsidethrough the gas pipe 15 is gathered.

The level of the sewage and wastewater gradually ascends as the sewage and wastewater is supplied and the sewage and wastewater moved to the upper chamber through the transfer pipes 23.

Since the starting point where the material at the lower side of the first reactor 5 moves to the upper chamber is at the lowermost portions of the transfer pipes 23, the material floating in the sewage and wastewater is separated due to the density difference and moved to the upper chamber.
The density difference between the floating materials is determined by surface tension generated by a length of the funnel-shaped transfer pipes 23 and the water surface.
That is, the longer the funnel-shaped transfer pipes 23 is and the wider the water surface W is the larger the density difference is.

Thus, the majority of bubbles generated in the first reactor 5 stays on the uppermost end of the level of the sewage and wastewater and the water surface W of the sewage and wastewater is mostly formed with the low density material by the surface tension.

Consequently, since the low density materials are in the upper chamber at the ends of the transfer pipes 23, material separation in which density of material is lower as the position in the first reactor 5 is high.

In the first reactor 5, the motor assembly M of the agitator 7 is driven so that the sewage and wastewater may be mixed up uniformly by the rotation of the impeller B.

The low density material such as scum, oil component, and fruit seed of the sludge floating on the water surface W is blocked by the lower rims of the transfer pipes 23 and does not move to the upper chamber.

The sawtooth-shaped filters 25 are formed at the lower rims of the transfer pipes 23 to filter and prevent the low density materials from moving to the upper chamber primarily.
In this case, the filtered low density materials float on the water surface for a long time and may be disintegrated organically.

Moreover, since the valve 6 of the gas pipe 15 is properly controlled to adjust the amount of the gas gathered in the stay chambers V and to control the level of water, the discharged amount of the low density material may be controlled.

That is, the amount of the gas generated from the sewage and wastewater is gathered in the stay chambers V and the external gas injected into the stay chambers V through the gas pipe 15 is increased, the level of water is lowered down and simultaneously the accumulation of the low density material is decreased (in a case when the amount of the low density material is relatively small).

On the contrary, in a case when the valve 6 of the gas pipe 15 is open, since the gas gathered in the stay chambers V is discharged to the outside, the pressure in the stay chambers V is decreased and the level of water ascends so that the accumulationof the lowdensitymaterial is increased .
In this case, since the water surface W is formed above the inlet 27 of the particle solid discharging pipe 11, the low density material is not discharged to the outside through the particle solid discharging pipe 11. That is, the low density material floats on the water surface W for a long time.

When the level of water descends and reaches the height of the particle solid discharging pipe 11, the low density material floating on the water surface W is discharged to the outside through the particle solid discharging pipe 29 so that the low density material may be removed secondarily.

That is, when the water surface descends and reaches the height of the inlet 27, the low density material such as scum, oil, etc. floating on the water surface W may be introduced through the inlet 27 and then be discharged out.

Even in a case when the low density material such as scum, oil component, and fruit seeds floats on the water surface formed at the uppermost end of the first reactor 5, the low density material enters the inlet 33 of theparticle solid discharging pipe 35 and returns back to the lower side of the first reactor 5 so that the low density material may reside in the first reactor 5 still and may be prevented from being transferred to the main treatment unit 4.

As described above, thelow- dens ity material separator 9 easily separates fat and oil components from the sewage and wastewater and decomposes the same into organic acid to accelerate the following anaerobic digestion so that the fat and oil component may be transformed into the digested gas without separation and treatment.

The high density material of the sludge contained in the sewage and wastewater is deposited down the lower side and accumulated on the bottom of the first reactor 5.

Meanwhile, the storage tank 3 is disposed between the pretreatment unit 2 and the main treatment unit 4 to make play a role of an acid fermenter, to store the sewage and wastewater temporally and to feed the sewage and wastewater to the main treatment unit 4.

Since the storage tank 3 stores the sewage and wastewater treated in the pretreatment unit 2 temporally, the storage tank 3 maybe omitted when the pretreatment unit 2 is connected directly to the main treatment unit 4.

The main treatment unit 4, as illustrated in FIGS.
4 to 6, includes a second reactor 40 in which the sewage and wastewater is introduced to be treated by the anaerobic reaction and discharged, anaerobic reaction activating devices C1, C2, C3, and C4 arranged in multilayer in the second reactor 40 in which solid-liquid separation occurs and agitation is carried out during methane gas and the sewage and wastewater ascend, a gas circulation unit 43 discharging gas in the lower side of the second reactor 40 to the upper side to make the sewage and wastewater flow to the lower side so that the agitation may occur and solid materials flow down, and a treated water circulation unit 45 disposed at a side of the second reactor 40 to circulate the treated water in the upper side to the lower side.

In the main treatment unit 4, the second reactor 40 has an internal space into which the sewage and wastewater is introduced and stored. An introducing pipe 47, through which the sewage and wastewater enters the second reactor 40, is connected to the lower side of the second reactor 40 and the sewage and wastewater may be introduced into the second reactor 40.

The second reactor 40 includes a gas discharging pipe 49 and a treated water discharging pipe 51 connected to the upper side thereof. Thus, the gas generated during the anaerobic reaction in the second reactor 40 is discharged through the gas discharging pipe 49 and the treated water is discharged through the treated water discharging pipe 51.

When the sewage and wastewater is supplied into the second reactor 40, methane gas is generated at the lowermost side of the second reactor 4 0 and gradually ascends and finally reaches the anaerobic reaction activating devices C1, C2, C3, and C4.

The anaerobic reaction activating devices C1, C2, C3, and C4 include first activating devices C1 and C2 that are arranged in the lower side of the second reactor transversally to bring a primary anaerobic reaction and to activate the solid-liquid separation and agitation by the generated gas, and second activating devices C3 and C4 that are arranged transversally in the upper side of the second reactor 40 to bring a secondary anaerobic reaction and to mix the sewage and wastewater uniformly in every block.

The sewage and wastewater introduced into the second reactor 40 pass through the first activating devices C1 and C2 and the second activating devices C3 and C4 sequentially to ascend and the anaerobic treatment, the solid-liquid separation, and the agitation may be carried out simultaneously.

In more detail, each of the first activating devices C1 and C2, as illustrated in FIGS. 5 and 6, includes a plate shape 53 blocking the internal space of the second reactor 40 transversally and at least one first fluid transfer pipe 57 protruding downwardly from the plate 53 to form a through-hole 55 such that the sewage and wastewater and gas may pass therethrough.

When the sewage and wastewater is introduced into the second reactor 40, the sewage and wastewater ascends from the lower side to the upper side of the second reactor 40 so that the sewage and wastewater passes through the first activating devices C1 and C2 sequentially through the at least one first fluid transfer pipe 57.

The solid-liquid separation and agitation may be carried out while the sewage and wastewater passes through the first activating devices Cl and C2 sequentially.
The ascending sewage and wastewater reaches the lower end line of the first fluid transfer pipe 577 to form the water surface.

As such, when the water surface is formed on the lower end line of the first fluid transfer pipe 57, a plurality of the first stay chambers V is formed around the first fluid transfer pipe 57.

In this case, the first fluid transfer pipe 57 may be relatively long so that a larger first stay chamber V
may be formed.

That is, preferably, the first fluid transfer pipe 57 is longer than a second fluid transfer pipe 70 provided in the later-described second activating devices C3 and C4.

Thus, since the amount of gas gathered in the first stay chambers V of the first activating devices Cl and C2 is greater than that in the first stay chambers V of the second activating devices C3 and C4, more amount of gas may be supplied from the lower chamber to the upper chamber of the second reactor 40 when the gas circulates the upper and lower chambers by the later-described gas circulation unit 43 and due to this a large amount of treated water may be transferred from the upper chamber to the lower chamber so that efficiency of agitation may be improved.

The gas ascended from the lower chamber of the second reactor 40 is gathered in the first stay chambers V of the first activating devices C1 and C2. When a preset amount of the gas is gathered, the gathered gas is scattered in all directions by the pressure of the first stay chambers V so that the gathered gas pushes the sewage and wastewater out of the first stay chambers V.

At this time, since the water surface and the lower end line of the first fluid transfer pipes 57 are on the same line, the gas pushed the sewage and wastewater out of the first stay chambers V is injected into the first fluid transfer pipes 57.

Deposition occurs spontaneously by the surf ace tension of the sewage and wastewater on the water surface so that only the lowest density wastewater (in which at least microorganisms and SS type solids only exist) is injected into the first fluid transfer pipes 57.

Thus, the low density wastewater ascends through the first fluid transfer pipes 57 but the relatively high concentration microorganism and solid material do not flow to the upper chamber. Time where the microorganism and solid material stay in the lower chamber is increased.

Thus, the solids contained in the sewage and wastewater are separated into the low concentration density solids and the high density solids.

Moreover, since microorganism in the sewage and wastewater is very small, methane gas generated by the microorganism has fine bubbles that cannot be watched with naked eyes.

It is difficult to bring the agitation effect by the fine bubbles rather the fine bubbles make a negative role of floating sludge.

However, the fine bubbles transferred into the first stay chambers V for gas are transferred into the upper chamber through the first fluid transfer pipes 57 in the form of very big bubbles in a next transfer stage.

That is, a plurality of fine bubbles generated in the vicinity of the water surface is concentrated to the first fluid transfer pipes 57 with a relatively small sectional area and ascend then are combined with each other to form big bubbles so that the agitation may be carried out more effectively.

Moreover, since some of the fine bubbles around the microorganism is combinedwithabigbubblestreamtransferred through the first fluid transfer pipes 57, the fine bubbles around the microorganisms are separated from the microorganisms more easily so that contact between the sewage and wastewater and the microorganism may occur more easily and that the microorganism may be increased very fast.

Thus, the fine bubbles working as a negative factor in the existing process during this process rather plays an important role of enhancing efficiency.

The first activating devices Cl and C2 maybe configured such that the plates 53 are arranged in a single layer or in a two more layers. This configuration may be determined according to a designer's choice.

The gas passed through the first activating devices Cl and C2 ascends further and finally reaches the second activating devices C3 and C4.

Each of the second activating devices C3 and C4, as illustrated in FIGS. 7 and 8, includes at least one block-shaped unit reactor 60.

Since all the unit reactors 60 have the same structure, only one unit reactor 60 will be described.

The block-shaped unit reactor 60 includes upper and lower frames 62 and 64 disposed to correspond to each other, legs 66 connecting the upper frame 62 to the lower frame 64, oblique plates 68 provided in the upper frame 62 to divide the internal space of the second reactor 40 into an upper chamber and a lower chamber, and second fluid transfer pipes 70 provided in the oblique plates 68 to provide passages through which a fluid passes.

In the second activating devices C3 and C4, the upper frame 62 has protrusions 72 and the legs 66 have coupling holes 74 formed on the lower ends into which protrusions 72 of another upper frame 62 are inserted.

Thus, at least two unit reactors 60 are stacked to form the second activating devices C3 and C4.

The oblique plates 68 are provided in the upper frame 62 to block the fluid from being transferred.

In this case, two sets of the oblique plates 68 are arranged wherein the plates 68 of each set are downwardly oblique and have at least one second fluid transfer pipe 70 formed at the center thereof to serve as a passage through which the sewage and wastewater passes.

When the sludge is deposited on the upper surface of the oblique plates 68, the sludge moves downwardly along the oblique plates 68 and thus is prevented from being accumulated.

Although the two sets of the oblique plates 69 are described above,the present invention is not limited thereto but only one oblique plate 68 may be disposed and in this case only one second fluid transfer pipe 70 protruded.

Fluid may flow through the second transfer pipes 70.
Thus, when the unit reactors 38 are stacked in the second reactor 40, each of the unit reactors 38 arranged on the same layer contacts with each other and the oblique plates 68 are transversally arranged on the same line as that of an oblique plate of an adjacent unit reactors 38 so that the internal space of the second reactor 40 is divided into upper and lower chambers.

The second fluid transfer pipes 70 protrude downwardly from the oblique plates 68 by a preset distance, and as described above preferably have a length shorter than the first fluid transfer pipes 57 of the first activating devices C1 and C2.

The gas ascended from the lower chamber of the second reactor 40 is gathered around the second fluid transfer pipes 70 in the same process as in the first activating devices C1 and C2 to form second stay chambers V.

When a preset amount of the gas is gathered in the second stay chambers V, the gathered gas is scattered in all directions by the pressure of the second stay chambers V so that the gathered gas pushes the sewage and wastewater out of the second stay chambers V.

Thus, the gas pushed the wastewater from the second stay chambers V is injected into the second fluid transfer pipes 70 by the same process as in the first activating devices so that solids contained in the sewage and wastewater may be separated into high density solids and low density solids.
Since the second activating devices C3 and C4 have the block shape, the solid-liquid separation and agitation occur in every unit reactors differently from in the first activating devices.

Therefore, it may be considered that uniform mixing may be achieved by the solid-liquid separation and the agitation in the entire second activating devices.

The sewage and wastewater and the gas ascended after passing through the second activating devices C3 and C4 may be discharged to the outside through a gas discharging hole 49 on the top and a treated water discharging hole 51 of the second reactor 40.

As described above, the sewage and wastewater and the gas sequentially pass through the anaerobic reaction activating devices CI, C2, C3, and C4 including the first activating devices C1 and C2 and the second activating devices C3 and C4 and ascend up so that the solid-liquid separation and the agitation may be carried out.

Since the solid-liquid separation and the agitation are repeated, the treated water is in the upper chamber of the second reactor 40 and the solids and microorganism are concentrated in the lower chamber. Thus, the treated water and the microorganism and solids are separated repeatedly in every stage so that flow in a plug flow reactor (PFR) may be maintained.

As described above, the first activating devices C1 and C2 are plates and the second activating devices C3 and C4 are blocks so that the anaerobic treatment process may be carried out in various ways.

Thefirstfluidtransferpipes57of the first activating devices C1 and C2 are longer than the second fluid transfer pipes 70. The first activating devices Cl and C3 are higher than and stacked in layers more than those of the second activating devices C3 and C4.

Thus, the gas and the wastewater ascending in the second reactor 40 undergo different agitations and separation process while passing through the first and second activating devices Cl, C2, C3, and C4 with different shapes and a relatively large amount of gas is supplied from the lower chamber to the upper chamber so that a relatively large amount of treated water flows from the lower chamber to the upper chamber so that agitation efficiency may be improved.

The first and second activating devices Cl, C2, C3, and C4 may have various shapes.

Referring to FIG. 4 again, the gas circulation unit 43 is provided at a side of the second reactor 40 to supply the gas filled in the first stay chambers V in the lower chamber of the second reactor 40 into the upper chamber of the second reactor 40 so that a rapid agitation may occur.

The gas circulation unit 43 includes first to fourth pipes L1, L2, L3, and L4 communicated with the stay chambers V of the second reactor 40, a fifth pipe L5 connected to the top of the second reactor 40, a sixth pipe L6 connecting the first to fifth pipes Ll, L2, L3, L4, and L5 and first to fifth valves Si, S2, S3, S4, and S5 provided in the first to fifth pipes Li, L2, L3, L4, and L5 to open and close the first to fifth pipes Li, L2, L3, L4, and L5.

Since the gas circulation unit 43 does not require a powered device such as a pump discharging gas, the gas can be circulated without power transmission.

That is, since hydraulic head by the sewage and wastewater filled in the first reactor exerts in the stay chambers V of the first reactor, the gas gathered in the stay chambers V of the lower chamber may be easily supplied in the stay chambers in the upper chamber by the hydraulic head when the valves Si, S2, S3, S4, and S5 are opened.
The first to fifth valves Si, S2, S3, S4, and S5 may include solenoid valves.

In the gas circulation unit 43, when the gas gathered in the lower chamber is supplied into the upper chamber to circulate, the first to fifth valves Si, S2, S3, S4, and S5 are properly open and closed such that the gas may be circulated into the upper chamber through various paths.

That is, all the first to fifth valves S1, S2, S3, S4, and S5 are open so that gases in every stage maybe supplied into the upper chamber or only the first and second valves Si and S2 are open such that the gas gathered in the lowermost stay chambers may be supplied into the stay chambers of the directly upper chamber.

Otherwise, only the first and third valves Si and S3 are open such that the gas gathered in the lowermost stay chambers maybe supplied into the stay chambers of the directly upper chamber.

As such, in a case when the first to fifth valves S1, S2, S3, S4, and S5 are properly open and closed to discharge the gases in the lower chamber of the second reactor 40 and to supply the gases into the upper chamber of the first reactor, the sewage and wastewater in the upper chamber is rapidly transferred into the lower chamber to fill the space occupied by the gas such that the gases and the sewage and wastewater may be mixed with each other.

Simultaneously, highdensitysolidsandmicroorganisms may be transferred down first. Then, when the sewage and wastewater in the lower chamber is transferred into the upper chamber due to the generated gas so that low density material is transferred into the upper chamber first and the secondary solid-liquid separation is carried out.

That is, the gas in the lower chamber of the second reactor40isdischargedperiodicallyoracycle ofdischarging the gas is adjusted according to the state of the agitation and the solid-liquid separation so that the gas and the sewage and wastewaterare effectivelymixedwitheachother,agitated, and/or the solid-liquid separation occurs in the second reactor 40.

The first activating devices and the second activating devices have some similar functions. However, since the solid-liquid separation and the agitation in the second activating devices are carried out voluntarily (so, it is difficult to control) in the reactor but the solid-liquid separation and the agitation in the first activating devices may be controlled arbitrarily according to operating conditions so that various conditions may be made during the operation without applying the various conditions to early design conditions, the first activating devices and the second activating devices are vital elements in the anaerobic treatment.

No matter what there are so many kinds of the sewage and wastewater beyond time and space, the apparatus is just installed and maintains only the fixed condition.

Thus, since type and amount of the sewage and wastewater generated during theoperationdifferentfromtheearlydesign may be changed variously, it must be required a compensation device to cope with this situation.

As described above, the sewage and wastewater and the gas may be separated into the solids and the treated water or mixed with each other during the passing through the first and second activating devices CI, C2, C3, and C4. When the gas circulation unit 43 is driven, a great deal of gas is discharged from the lower chamber into the upper chamber of the first reactor. At this time, in order to fill the empty chamber, the treated water in the upper chamber of thefirstreactorisrapidlytransferredintothelowerchamber so that the secondary mixing is carried out and the agitation effect may be increased.

In spite of the gas circulation unit 43 disposed at the side of the second reactor 40, the present invention is not limited thereto, but another gas circulation unit 78, as illustrated in FIG. 9, maybe disposed at the opposite side of the second reactor 40.

In the first activating devices Cl and C2 or the second activating devices C3 and C4, the gases gathered in the stay chambers V near the fluid transfer pipes 34 and 52 in the vicinity of the gas circulation unit 78 may be easily discharged out into the gas circulation unit 43, but the gases gathered in the stay chambers Vat the relatively central region of the second reactor 40 are hardly discharged because a long distance from the gas circulation unit 43.

Therefore, another gas circulation unit 78 may be disposed at the opposite side of the second reactor 40.
As such, by disposing the gas circulation unit 78 at the opposite side of the second reactor 40, the gases gathered at the central region of the second reactor 40 may be also easily discharged out through the gas circulation units 43 and 78.

The pair of circulation units 43 and 78 or more may be disposed at the second reactor.

Meanwhile, as illustrated in FIG. 4, a circulation device 45 circulating the gas and the sewage and wastewater from the lower chamber to the upper chamber in the second reactor 40 and vice versa is selectively mounted to a side of the second reactor 40.

The circulation device 45 includes a pipe L wherein the pipe L communicates the upper chamber of the second reactor 40 with the lower chamber. A circulation pump P is disposed in the pipe L.

When the circulation pump P is driven, the sewage and wastewater and/or the solids stored in the upper chamber of the second reactor 40 are suctioned into the pipe L and are discharged out into the lower chamber so that the sewage and wastewater and the solids stored in the upper and lower chambers of the second reactor 40 are circulated.

When this circulation is performed at a preset period, pH of the first reactor is controlled (such as high pH of the upper chamber of the first reactor and low pH of the lower chamber thereof) and the sludge deposited in the anaerobic reaction activating devices C1, C2, C3, and C4 is circulated.

An accumulation preventing unit 80 is disposed at the lower side of the second reactor 40 to prevent the deposited solids from being accumulated in the bottom of the second reactor 40.

The accumulation preventing unit 80 includes a seventh pipe L7, connected to a lower side of the second reactor 40, into which the sewage and wastewater is introduced and a discharge pump P2 connected to theseventhpipeL7togenerate a suction force.

When the discharge pump P2 is driven, the deposited solids and the sewage and wastewater in the lower chamber of the second reactor 4 0 are discharged out through the seventh pipe L7 so that the sol ids maybe prevented f rombeing deposited in the lower chamber of the second reactor 40.
Following experimental data are obtained as a result of treating the sewage and wastewater in the main treatment unit 4.

[Table 1]

Conventional Present invention Treated amount of foods 17-18 30-60 (ton/day) Stayed time (day) 26-27 7-12 Gas per ton (m3/ton) 30-40 90-120 Methane content (%) 60-65 70-75 Operating temperature 35-37 35-37 ( C) Efficiency (%) 40 85 As seen from the experimental data, the apparatus of the present invention exhibits about two times treated amount of foodbytheexistingapparatus. Inaddition, the apparatus ofthepresentinvention hasaboutfourtimesgeneratedmethane gas of the existing apparatus.

Consequently, the apparatus of the present invention achieves efficiency higher than two times efficiency of treating sewage and wastewater of the existing apparatus.

The exemplary embodiments of the present invention are provided for the easy description and understanding of the present invention with specific examples but do not limit the scope of the present invention. It will be appreciated by those skilled in the art that various changes and modifications may be practiced without departing from the spirit of the present invention.

Claims

1. An apparatus for treating sewage and wastewater, comprising:

a pretreatment unit separating low density material from the sewage and wastewater using a low-density material separation;

a storage tank storing the sewage and wastewater supplied from the pretreatment unit; and a main treatment unit treating the sewage and wastewater supplied from the storage tank in anaerobic digestion to produce methane gas from the sewage and wastewater such that stayed time of the methane gas is increased during the ascending of the methane gas and that agitation of the sewage and wastewater is carried out.

2. The apparatus of claim 1, wherein the pretreatment unit comprises:

a first reactor in which the sewage and wastewater is introduced to be treated and is discharged out;

an agitator provided in the first reactor to agitate and uniformly mix up the sewage and wastewater and bubbles;
at least one low-density material separator dividing an internal space of the first reactor into upper and lower chambers to allow the sewage and wastewater and a gas to ascend therethrough sequentially, having a stay chamber formed above the sewage and wastewater by bubbles generated from the sewage and wastewater or a gas injected from the outside such that low density material floats on the water surface, that the water level is lowered down when an amount of gas gathered in the stay chamber is increased and that the floating low density material on the water surface is prevented from ascending and being firstly separated to be supplied to the main treatment unit when the gas is discharged from the stay chamber and the water level ascends; and a particle solid discharging pipe disposed near the low-density material separator to discharge the low density material floating the water surface to the outside when the water level of the stay chamber is lowered down such that the low density material is prevented from being supplied to the main treatment unit secondarily.

3. The apparatus of claim 2, wherein the first reactor comprises:

a gas pipe connected to the stay chamber to discharge the gas gathered by the low-density material separator to the outside and to inject an external gas into the stay chamber;
and a treated water discharging pipe connected to the first reactor to discharge the sewage and wastewater treated while passing through the low-density material separator to the outside.

4. The apparatus of claim 2, wherein the agitator comprises:

a motor assembly disposed on the top of the first reactor;
and an impeller mounted around a rotating shaft of the motor assembly.

5. The apparatus of claim 2, wherein the low-density material separator comprises:

a blocking plate dividing the internal space of the first reactor into the upper and lower chambers and formed with a plurality of passing holes; and a plurality of transfer pipes protruding downwardly from the lower side of the blocking plate and communicated with the passing holes such that the sewage and wastewater flows therethrough;

wherein the stay chamber is formed between the lower side of the blocking plate and the outer circumference of the transfer pipes when the water surface of the sewage and wastewater ascends and material near the water surface of the stay chamber is trans f erred upwardly through the trans f er pipes due to density difference.

6. The apparatus of claim 2, wherein the particle solid discharging pipe includes:

an inlet through which the low density material is introduced; and an outlet through which the introduced low density material is discharged;

wherein the inlet has a large sectional area such that the low density material floating on the water surface is introduced thereinto and the outlet has a sectional area less than that of the inlet so that the low density material is discharged, and the inlet is lower than the water level of the stay chamber.

7. The apparatus of claim 2, wherein one of the particle solid discharging pipes which is disposed at the uppermost side has an inlet disposed at the same height as the uppermost water surface and an outlet connected to the lower side of the first reactor such that the low density material is circulated within the first reactor.

8. The apparatus of claim 1, wherein the main treatment unit comprises:

a second reactor in which the sewage and wastewater is introduced to be treated by the anaerobic reaction and which gas and the treated sewage and waste water are discharged;

anaerobic reaction activating devices in which a first activating device and a second activating device of different shapes are arranged in the second reactor to form the second reactor into multiple layers, which a stay chamber is formed to gather the gas such that solid-liquid separation and agitation between the gas and the sewage and wastewater are carried out simultaneously while the gas passes through the first and second activating devices; and a gas circulation unit disposed at a side of the second reactor to circulate the gas in the stay chamber formed in the lower chamber of the second reactor into the upper chamber such that the sewage and wastewater of the upper chamber is transferred to fill the stay chamber of the lower chamber to make the agitation.

9. The apparatus of claim8, further comprising an accumulation preventing unit disposed at the lower side of the second reactor to prevent scum and deposited material from being deposited and accumulated.

10. The apparatus of claim 8, wherein the anaerobic reaction activating device comprising:

the first activating device arranged transversally in the lower chamber of the second reactor to bring a primary anaerobic reaction and to activate the solid-liquid separation and agitation by the generated gas; and the second activating device arranged transversally in the upper chamber of the second reactor to bring a secondary anaerobic reaction and to mix the sewage and wastewater uniformly in every block and having a shape different from that of the first activating device.

11. The apparatus of claim 10, wherein the first activating device comprises:

a plate having a plate shape or a block shape and blocking the internal space of the second reactor transversally; and at least one first fluid transfer pipe protruding downwardly from the plate to form a through-hole such that the sewage and wastewater and gas pass therethrough.

12. The apparatus of claim 10, wherein the second activating device comprises:

upper and lower frames including at least one block-shaped unit reactor disposed to correspond to each other;

legs connecting the upper frame to the lower frame;
an oblique plate provided in the upper frame to divide the internal space of the second reactor into an upper chamber and a lower chamber; and a second fluid transfer pipe provided in the oblique plate to provide a passage through which a fluid passes and being shorter than the first fluid transfer pipe.

13. The apparatus of claim 10, wherein the sewage and wastewater supplied into the second reactor ascends to form the water level on the lower end line of the first fluid transfer pipe such that the stay chamber into which gas is gathered is formed around the fluid transfer pipe and that low density solids ascend through the fluid transfer pipe due to a pressure of the gas and the solid-liquid separation and the mixing are carried out simultaneously.

14. The apparatus of claim 8, wherein the gas circulation unit comprises:

first to fourth pipes communicated with the stay chambers of the second reactor;

a fifth pipe connected to the upper side of the first reactor;

a sixth pipe connecting the first to fifth pipes; and first to fifth valves provided in the first to fifth pipes to open and close the first to fifth pipes;

wherein the gas gathered in a lower stay chamber of the second reactor is circulated into a stay chamber of an upper layer so that the sewage and wastewater of the second reactor is transferred into the lower chamber of the second reactor to fill the stay chamber out which the gas is discharged resulting in causing the agitation when the first to fifth valves are open.

15. The apparatus of claim 8, wherein the gas circulation unit is disposed at the opposite side of the second reactor so that the gas in the second reactor may be discharged out.