AU725812B2

AU725812B2 - Method and apparatus for treating wastewater

Info

Publication number: AU725812B2
Application number: AU75510/98A
Authority: AU
Inventors: Norihiko Hirano
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-06-06
Filing date: 1998-06-05
Publication date: 2000-10-19
Anticipated expiration: 2018-06-05
Also published as: JP3285884B2; KR100492683B1; CN1228064A; KR20010029446A; WO1998055407A1; CN1095449C; AU7551098A

Description

SPECIFICATION

Method and Apparatus for Treating Wastewater TECHNICAL FIELD The present invention relates to a wastewater treatment apparatus which is suited for small-to-medium-size treatment of wastewater, in particular, domestic wastewater and sewage, and which is superior in quality of treated water, easy in maintenance and control, and inexpensive.

BACKGROUND ART Conventionally, "the batch-type activated sludge method" has been used for small-to-medium-size treatment of sewage.

With this method, a single bath is used to carry out intermittent aeration, settlement and discharge; however, to stably treat water being treated and having variable water quality, the operation control thereof is required to be carried out carefully, thereby causing aproblemin difficulty of maintenance and control.

As another method, "the contact aeration method" is well known which can be said as a method being easy in maintenance and control; however, if only this method is used, the removal of nitrogen, which is required at present, is insufficient, thereby causing a problem.

Furthermore, the so-called "oxidation ditch method" is used which is easy in maintenance and control, and withstands changes in the amount of treatment. This method is a kind of floating biological method wherein biological treatment is carried out by introducing sewage into a circulation water line and by carrying out aeration while the sewage is circulated and flown.

With this method, in order to carry out aeration and flowing, a rotor system is generally used wherein sewage is stirred mechanically to carry out aeration and flowing; however, since this mechanical aeration is surface aeration, the depth of the water cannot be increased, thereby causing a problem of increasing the area of installation, and also causing a problem of requiring high drive power for flowing when a blow type for air blowing is used.

Instead of these kinds of mechanical aeration and flowing systems, "the aeration method by dropping water flow" has also been proposed (Japanese Patent Publication No. 37195 of 1989) on the basis of means wherein a step is provided in a circulation water line.

With this method, the abovementioned problems with the mechanical aeration system can be solved; however, since the system uses the so-called dropper wherein the source of aeration and the source of flowing are integrated, anaerobic treatment required for the removal of nitrogen and phosphorus now being at issue becomes insufficient. In particular, anaerobic agitation indispensable for efficient removal of nitrogen cannot be carried out, as a result, causing a problem in making high-level wastewater treatment difficult.

Accordingly, objects of the present invention are to solve the abovementioned problems of the conventional art, and to provide a novel wastewater treatment apparatus suited for small-to-medium-size sewage treatment in particular. In other words, the present invention is intended to provide a high-level wastewater treatment apparatus which is simple in equipment, compact, inexpensive, easy in maintenance and control, and superior in quality of treated water.

DISCLOSURE OF INVENTION In order to attain the abovementioned objects, the following means are adopted.

In Claim 1, a secondary wastewater treatment method for carrying out biological treatment by circulating primarily treated water in a water line after removal of deposits, impurities and the like contained in wastewater, wherein a weir for forming a shooting flow energy absorber having an openable lower portion is provided inside the abovementioned water line so as to be able to carry out aerobic treatment by only overflow, anaerobic treatment by only underground flow, and both aerobic treatment and anaerobic treatment by both overflow and underground flow is adopted.

With this means, aerobic treatment for oxidizing and decomposing organic substances and anaerobic treatment for mainly carrying out denitrification can be selected or combined as desired, whereby it is possible to carry out efficient wastewater treatment suited to the properties of wastewater such as sewage.

In Claim 2, the wastewater treatment method in accordance with Claim 1, being capable of adjusting the ratio of aerobic treatment and anaerobic treatment as desired by adjusting the lower opening amount of the abovementioned weir, is adopted.

With this means, by making the lower opening amount of the weir adjustable, aerobic treatment and anaerobic treatment can be selected or combined as desired; in addition, by adjusting the ratio of overflow and underground flow, that is, the ratio of aerobic treatment and anaerobic treatment, efficient wastewater treatment suited to the properties of wastewater is made possible.

In Claim 3, in a secondary wastewater treatment apparatus for biologically treating primarily treated water in a circulation water line after removal of deposits, impurities and the like contained in wastewater, a circulation pump for discharging treated water drawn from the final end portion of the abovementioned circulation water line, and a weir disposed in the middle of the circulation water line and comprising a vertical wall and an inclined wall to form a shooting flow energy absorber are provided.

Furthermore, the wastewater treatment apparatus can select as desired either one or both of anaerobic treatment carried out by passing underground circulation water from an opening portion under the weir and/oraerobic treatment carried out by shooting and splashing circulation water overflowing from above the weir by using one of the means for "vertically moving the abovementioned weir body itself," for "vertically sliding an open/close plate disposed on the vertical wall surface of the abovementioned weir body having an opening portion formed between the weir body and the bottom portion of the water line and being secured," for "rotating an open/close valve disposed at the opening portion under the abovementioned weir body having the opening portion formed between the weir body and the bottom portion of the water line and being secured," or for "inclining a vertical wall constituting the abovementioned weir body in the flowing direction." By this means, in acase when the weir body which is movable vertically is fixed at the bottom of a bath, only aerobic treatment can be carried out by overflowing water to be treated from above the weir and by shooting and splashing the water.

In addition, in the case when the weir body is secured at the upper position of the water line, only anaerobic treatment can be carried out by underground-passing circulation water from under the weir without overflowing water to be treated from above the weir. Furthermore, in a case when the weir body is secured at an intermediate position of the water line in the vertical direction, both aerobic treatment and anaerobic treatment can be carried out by overflowing water to be treated from above the abovementioned weir body and by underground-passing circulation water from the opening portion below the weir.

By only adjusting the position of the weir in accordance with the properties of water to be treated in this way, either one or both of aerobic treatment and/or anaerobic treatment can be selected as desired and appropriate.

Next, in a case of adopting a means for vertically moving the open/close plate provided on the veirtical wall surface of the weir body having a submerged opening portion formed between the weir body and the bottom portion of the water line and being secured, the open/close plate acts as an adjustment member capable of selecting either one or both of aerobic treatment and/or anaerobic treatment as appropriate.

In other words, by selecting the securing position of this open/close plate appropriately, the opening amount of the submerged opening portion and the upper end position of the weir are changed, whereby the ratio of aerobic treatment and anaerobic treatment can be adjusted more easily.

Furthermore, in a case when the rotatable open/close valve is provided at the submerged opening portion formed between the secured weir body and the bottom of the water line, the open/close valve changes the opening amount of the submerged opening portion, whereby the ratio of aerobic treatment and anaerobic treatment can be adjusted easily.

Furthermore, in a case of the means for inclining the vertical wall constituting the abovementioned weir body with respect to the inclined wall, this vertical wall capable of being inclined acts as an adjustment member capable of selecting either one or both of aerobic treatment and/or anaerobic treatment as appropriate. In other words, the opening amount of the submerged opening portion is changed by the inclination amount thereof, whereby the ratio of aerobic treatment and anaerobic treatment can be adjusted easily.

In Claim 4, the wastewater treatment apparatus in accordance with Claim 3, wherein the angle of the inclined wall formed on the downstream side of the abovementioned weir body is made changeable, is adopted.

This weir wherein the angle of the shooting flow water surface is made variable can adjust the dropping angle and the dropping speed of circulation water overflowing from above the weir as desired, thereby acting to adjust the amount of water shooting and splashing, that is, the amount of aeration.

In Claims 5 and 6, a submerged weir is provided at the bottom portion of the circulation water line around the weir body in accordance with Claims 3 and 4, respectively.

The submerged weir disturbs the flow of circulation treatment water underground-passing under the weir, and acts to amplify the effect of anaerobic agitation.

In Claims 7 and 8, in the wastewater treatment apparatus in accordance with Claims 5 and 6, respectively, the discharge port of the circulation pump is provided toward the submerged opening portion for forming underground flow formed under the weir.

The discharge port of the circulation pump provided toward the submerged opening portion acts to securely underground-pass circulation water through the submerged opening portion, and allows circulation water to securely collide with the submerged weir, thereby amplifying the effect of anaerobic agitation.

In Claim 9, by using a wastewater treatment apparatus for carrying out high-level treatment by supplying secondarily treated water treated by the wastewater treatment method in accordance with Claims 1 or 2, and by providing a plurality of flexible fiber-like contact materials having portions shaken by circulation flow at intervals in the flowing direction in the circulation water line, the contact materials are allowed to hold onto organisms to form a biological treatment zone, and the secondarily treated water is circulatingly flown while aeration is carried out at the upstream of the biological treatment zone, thereby carrying out aerobic treatment and anaerobic treatment.

Furthermore, in Claim 10, by using a wastewater treatment apparatus for carrying out high-level treatment by supplying secondarily treated water treated by the wastewater treatment apparatus in accordance with one of Claims 3 through 8, and by providing a plurality of flexible fiber-like contact materials having portions shaken by circulation flow at intervals in the flowing direction in the circulation water line, the contact materials are allowed to hold onto organisms to form a biological treatment zone, and the secondarily treated water is circulatingly flown, thereby carrying out aerobic treatment and anaerobic treatment.

By the means in accordance with Claims 9 or 10, in addition to the secondary treatment using the shooting flow energy absorber, by carrying out high-level treatment of the biological treatment using the contact materials, a higher degree of purified treated water can be obtained.

Furthermore, since the means uses "flexible fiber contact materials having portions shakenby circulation flow," the flow resistance of the contact materials against the circulation flow becomes low. Moreover, organisms hold-onto ability becomes more efficient and secure, thereby forming excellent biological films.

In Claims 11 and 12, a strand formed of bundled fibers is used as a flexible fiber-like contact material in accordance with Claims 9 and 10, respectively.

By this means, the strand formed of bundled fibers is shaken in water and separated, whereby the surface area thereof to which organisms attach and wherein organism films are formed becomes larger.

In Claims 13 through 16, the flexible fiber-like contact materials in accordance with Claims 9-through 12, respectively, comprise carbon fibers.

Carbon fibers are superior in biological absorption and thus function as effective contact materials.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a plan view schematically showing a first embodiment of a wastewater treatment apparatus in accordance with the present invention at the first and second treatment steps thereof before high-level treatment; (p FIG. 2 is a view taken on arrow line X-X of FIG. 1 of the same embodiment; FIG. 2 is a view showing a condition wherein a movable weir body provided in the apparatus is fixed on the bottom of the bath; FIG. 2 is a view showing a condition wherein the weir body is secured in a nearly intermediate position of the bath in the vertical direction; and FIG. 2 is a view showing a condition wherein the body is secured at the upper position of the bath; FIG. 3 is a view taken on arrow line X-X of FIG. 1, showing a modified example of the weir; FIG. 3 is a view showing a condition wherein a vertical-slide-type open/close plate provided at the vertical wall portion of the secured weir on the upstream side is fixed on the bottom of the bath; and FIG.

3 is aview showinga condition wherein the open/close plate is secured at an upper position and a submerged opening portion is formed under the weir body; FIG. 4 is a view taken on arrow line X-X of FIG. 1, showing another modified example of the weir; FIG. 4 is a view showing a condition wherein an open/close valve provided at the lower opening portion of the secured weir is in a vertical condition and closes the submerged opening portion; and FIG.

4 is aview showinga condition wherein the open/close valve is in a horizontal condition and opens the lower area of the weir body; FIG. 5 is a view taken on arrow line X-X of FIG. 1, showing yet another modified example of the weir; FIG. 5 is a view showing a condition wherein the lower end of the vertical wall constituting the weir, capable of being inclined, is fixed on the bottom of the bath; and FIG. 5 is a view showing a condition wherein the vertical wall is inclined to the downstream side to form a submerged opening portion in the lower area of the weir body; FIG. 6 is a view taken on arrow line X-X of FIG. 1, showing that the discharge port of the circulation pump is provided toward the submerged opening portion under the movable weir and that a submerged weir is formed around the submerged opening portion at the bottom of the bath; FIG. 7 is a plan view schematically showing a wastewater treatment apparatus in accordance with a second embodiment of the present invention, provided with a labyrinth-shaped circulation water line; FIG. 8 is a plan view schematically showing a wastewater treatment apparatus in accordance with a third embodiment of the present invention, having a helical shape; FIG. 9 is a plan view schematically showing a wastewater treatment apparatus comprising an apparatus for primary treatment and secondary treatment using a shooting flow energy absorber and a high-level treatment apparatus provided with contact materials, arranged in parallel; FIG. 10 is an external perspective view schematically showing the wastewater treatment apparatus, with the primary treatment portion omitted; FIG. 11 is a partial sectional view taken on line XI- XI shown in FIG. 9, showing a condition wherein the contact material is mounted in the circulation water line; FIG. 12 is a schematic view showing another embodiment of the high-level treatment apparatus; and FIG. 13 is a graph showing experiment data in a case when wastewater treatment is carried out by using the secondary treatment apparatus using the shooting flow energy absorber and the high-level treatment apparatus using the contact materials; FIG. 13 is a graph showing changes in BOD concentration; FIG. 13 is a graph showing changes in total nitrogen concentration; and FIG. 13 is a graph showing changes in ammonia nitrogen concentration.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described on the basis of embodiment examples.

First, by referring to FIGS. 1 through 8, a secondary treatment method and apparatus using a shooting flow energy absorber will be described.

First, the numeral 1 (la, lb and Ic) shown in FIGS. 1 through 8 represents a treatment bath body.

In a nearly rectangular treatment bath body la constituting a wastewater treatment apparatus in accordance with a first embodiment of the present invention in FIG. 1, a partition wall 2a is formed in an open condition at one end thereof in the central longitudinal direction in the area inside the treatment bath, and a U-turn-shaped circulation water line 3a partitioned by the partition wall 2a is formed.

Near this circulation water line 3a, a primary treatment apparatus I comprising a screen apparatus, a settlement bath, a sludge dewatering apparatus, a flowrate adjustment bath and the like (these are not shown) is provided. Raw wastewater R, such as sewage, first flows into this primary treatment apparatus I, and the so-called "primary treatment" for removing deposits, impurities and the like in the raw wastewater R is carried out.

Furthermore, in the primary treatment apparatus I, primarily treated water T1 is obtained while the flowrate is adjusted, and flows from the primary treatment apparatus I to the circulation water line 3a constituting a primary treatment apparatus II.

Next, a circulation pump represented by the numeral 4 is provided between a suction pipe 9a directly connected to the water line final end portion 7a of the circulation water line 3a and a discharge pipe 9b (a pipe for forming a discharge port for circulation water) directly connected to the water line start end portion 7b thereof, and is used to circulate and flow water to be treated inside the circulation water line 3a.

By changing the discharge amount (or discharge speed) of the water to be treated discharged from the circulation pump 4, the circulation speed of water to be treated can be selected as appropriate.

The numeral 5 shown in FIG. 1 represents a weir body, which is provided in the middle of the circulation water line 3a near the water line start end portion 7b and away from the end portion 7b by a predetermined distance so as to divide the circulation water line 3a in the width direction thereof.

The weir body 5 is provided near the water line start end portion 7b as described above, because anaerobic agitation described below can be carried out effectively by efficiently utilizing the flow speed of water to be treated discharged from the abovementioned circulation pump 4 via the discharge pipe 9b, and biological treatment can thus be carried out efficiently.

A weir body 5a shown in FIG. 2 is an embodiment of a weir wherein the body 5a itself is provided so as to be movable in the vertical direction by a method selected as appropriate.

As a method of vertically moving this weir body 5a, a desired means can be adopted; for example, a method wherein the side ends of the weir body 5a are fitted in dovetail grooves provided in the vertical direction on the side walls of the water line, and the weir body 5a is slid vertically and secured with an appropriate means at a desired position, or a method wherein a rack-pinion mechanism is provided on the weir body and the side walls of the water line, and the weir body is set and secured at a desired position by gear rotation, or the like.

It is preferable that the position of the weir body is adjusted mechanically and automatically; however, in this case, by using the gear of the abovementioned rack-pinion mechanism as drive power or by suspending the weir body 5a by a simple crane or the like, it is conceived that the weir body is secured at an appropriate position.

As shown in FIGS. 2 through the weir body 5a has a shape having a vertical wall 6a at the upstream side and an inclined wall 6b which is used as a water flow surface when water to be treated overflowing from above the weir body drops (shoots) in an inclined downward direction.

In other words, the vertical wall 6a is disposed toward the upstream side and functions to hold back water to be treated; and the inclined wall 6b used as the other wall functions to allow the water to be treated held back by the vertical wall 6a overflowing from the upper end of the weir body 5a to shoot and splash, and forms the so-called "shooting flow energy absorber." The inclined wall 6b is engaged so that the angle a thereof with respect to the vertical wall 6a can be changed.

This engagement can be attained by the pivot connection of the vertical wall 6a and the water-flowing inclined wall 6b for example, and by securely holding the inclined wall 6b at a desired angle.

By changing this angle a, the flowing-down speed and angle of water to be treated along the inclined wall 6b can be changed. In other words, by changing the shooting and splashing condition of water to be treated, the amount of involvedair, theamountof aeration, is changed, whereby aerobic treatment can be adjusted. The angle a of the inclined wall 6b is usually adjusted to about 45' 5 to 100, and the treatment is carried out.

Primary and secondary wastewater treatment methods using the wastewater treatment apparatus in accordance with the present embodiment will be described below concretely.

As described already, raw wastewater R such as sewage first flows into the primary treatment apparatus I comprising a screen apparatus (not shown) for removing solid matter and the like, a settlement bath (not shown) for settling and removing suspension, a flowrate adjustment bath (not shown) for adjusting flowrate and the like so as to become primarily treated water T1, then supplied into the circulation water line 3a, and biologically treated (regarding the pretreatment apparatuses such as the screen apparatus, the settlement bath, the flowrate adjustment bath and the like, it is possible to use appropriate apparatuses in accordance with the properties of water to be treated).

Activated sludge for floating organism treatments has been supplied into the circulation water line 3a beforehand, and maintained and circulated together with inflow water to be treated. Therefore, pollutants in the water to be treated is biologically decomposed and removed while flowing circulatingly in the anaerobic or aerobic condition or in both conditions (hereinafter referred to as "secondary treatment").

And this secondarily treated water T2 is extracted from the circulation water line 3a by an overflow pipe (or a communication pipe) for example, and guided to an aftertreatment apparatus, not shown, such as a settlement bath (when treatment ends at the secondary treatment) or a high-level treatment apparatus described below (when highlevel treatment is further carried out). In addition, as means for supplying and extracting water to be treated, the desired means can be adopted as appropriate.

"The secondary treatment" is herein described in more detail; in the secondary treatment apparatus provided with a shooting flow energy absorber, when only aerobic treatment is carried out, the weir body 5a is fixed on the bottom B of the bath as shown in FIG. 2 the whole amount of circulating water to be treated is overflowed from above the weir body and shot and splashed, whereby the so-called "aeration" is carried out by utilizing the introduction of air. This increases the amount of oxygen dissolving and remaining in the water to be treated, and active biological treatment by aerobic microorganisms is carried out (hereinafter referred to as "aerobic treatment").

On the other hand, when circulation water to be treated is biologically treated by using anaerobic microorganisms, the weir body 5a is disposed upper as shown in FIG. 2 so as to hold back the surface layer area of the circulation water and to form underground flowing water by passing the circulation water to be treated through a submerged opening portion 8 formed between the weir body 5a and the bottom B of the bath.

With this, the water to be treated does not overflow from above the weir body 5a, whereby aeration is not carried out, and only the underground flowing water is biologically treated anaerobically (hereinafter referred to as "anaerobic treatment").

Furthermore, when the weir body 5a is secured at a nearly intermediate position in the vertical direction as shown in FIG. 2 part of the circulation water to be treated is overflowed from above the weir body 5a and shot to carry out aerobic treatment; in addition, by passing the circulation water to be treated through the submerged opening portion 8 formedbetweenthe weir body 5a andthebathbottomB, anaerobic treatment can also be carried out for underground flowing water.

By adjusting the securing position of the weir body in the vertical direction in accordance with the properties of water to be treated, the ratio of aerobic treatment for overflowing water and anaerobic treatment for underground flowing water can be adjusted as desired. In the case of wastewater including large amount of ammonia nitrogen, for example, the rate of anaerobic treatment is increased to accelerate nitrification and denitrification treatment.

In other words, the secondary treatment apparatus in accordance with the present invention can carry out aerobic treatment by aeration and anaerobic treatment without exposure to air simultaneously; in addition, it is useful as awastewater treatment apparatus applicable to water to be treated having a wide range of properties by appropriately adjusting the ratio of the two.

Furthermore, in the secondary treatment apparatus in accordance with the present invention, it is possible to adopt a weir body 5b provided with an open/close plate 11 which is slidable in the vertical direction along the vertical wall 6a as shown in FIG. 3.

This weir body 5b is secured at a nearly intermediate position of the bath la, and a submerged opening portion 8 is formed between the weir body 5b and the bottom B of the bath at all times. However, the submerged opening portion 8 can be opened/closed as desired by vertically sliding the open/close plate 11 mounted on the surface of the vertical wall 6a of the body 5b along the vertical wall 6a.

As shown in FIG. 3 this open/close plate 11 is provided so as to be slidable up to a position higher than the upper end of the secured weir body 5b. Therefore, it is possible to carry out only anaerobic treatment for the underground flowing water passing through the submerged opening portion 8 by completely holding back the flow of the surface layer of the circulation water to be treated.

Furthermore, only by adjusting the position of the open/close plate 11, the circulation water can be overflowed from above the secured weir body 5b, and the circulation water can also be passed through the submerged opening portion 8 to form underground flowing water; the ratio of the two can also be selected as appropriate.

As shown in FIG. 4, instead of the abovementioned open/close plate 11, this open/close valve 12 shaped like a butterfly-shaped valve or the like may be provided at the submerged opening portion 8 so as to cross the bath 3a. With this configuration, as shown in and of the same figure, the opening amount of the submerged opening portion 8 is adjusted by rotating the open/close valve 12, thereby to adjust the rate of the amount of the overflowing water and the amount of the underground flowing water.

Furthermore, a weir body 5c provided with a vertical wall 6a formed in the shape of a plate as shown in FIGS. 5 and can also be adopted. This vertical wall 6a is inclined in the downstream side direction with the upper end position of the weir body 5c used as an axis to form a submerged opening portion 8, whereby underground flowing water can also be formed.

By adjusting the amount of the inclination of the vertical wall 6a, circulation water to be treated can be overflowed from above the secured weir body 5c, the circulating water to be treated can also be passed from the submerged opening portion 8, and the ratio of the two can also be selected as appropriate.

In this respect, the weir body 5c is the same as the abovementioned weir bodies 5a and In the case of the weir bodies 5b and 5c, the inclined wall 6b is also made adjustable just as in the case of whereby the speed and angle of water to be treated flowing down the inclined wall 6b can be changed.

Next, FIG. 6 shows an embodiment wherein a submerged weir is provided at the bottom B of the bath around the submerged opening portion 8 in the lower area of the weir body The submerged weir 10 in accordance with the present embodiment acts to disturb underground flowing water (water to be treated flowing at the bottom B of the bath) passing through the submerged opening portion 8; by providing this submerged weir 10, the effect of anaerobic agitation can be amplified.

By providing the discharge pipe 9b so as to discharge circulation water to be treated in the direction of the submerged weir 10, the circulationwater to be treated collides with the submerged weir 10 efficiently, and the effect of anaerobic agitation can be enhanced securely (even in the case of adopting the weir bodies 5b and 5c, wherein the same effect can be obtained by providing the submerged weir In the embodiments described above, the U-turn-shaped circulation water line 3a provided with the partition wall 2a in the longitudinal direction of the treatment bath body la is adopted; however, in a narrow installation space, it is possible to form a labyrinth-shaped circulation water line 3b by providing partition walls 2b in a zigzag pattern in a nearly square bath body lb just as the embodiment shown in FIG. 7.

In the case of this embodiment, the whole of thewastewater treatment apparatus can be made flat and more compact. The shape and installation method of the weir body 5 (5a, 5b, and the installation method of the submerged weir 10 and the discharge pipe 9b are made similar to those of the configurations shown in the abovementioned FIGS. 1 through 6.

Furthermore, just as the embodiment shown in FIG. 8, a circulation water line 3c can be formed in a flat helical shape by using a helical (or spiral) bath 1c. In this case, flow in the circulation water line 3c becomes smooth; furthermore, by discharging secondary treated water T2 into a space formed at the central portion, and by utilizing this space at the central portion as a settlement bath for example, the apparatus can be configured more compactly.

Next, an embodiment regarding a high-level treatment apparatus installed to further purify treated water secondarily treated by the abovementioned means will be described on the basis of FIGS. 9 through 12.

First, the code II shown in FIGS. 9 and 10 represents a secondary treatment apparatus using a shooting flow energy absorber, and the code III shown in the same figures represents a high-level treatment apparatus using contact materials.

Both the apparatuses II and III are arranged in parallel, and this arrangement has the external appearance of a rectangular shape on the whole. In the treatment bath 1 of each of the apparatuses II and III, partition walls 2a and 2c, each being open at one end, are formed to form U-turn-shaped circulation water lines 3a and 3d.

In the secondary treatment apparatus II, a weir body 5b, 5c) used as a shooting flow energy absorber is provided in the middle of the circulation water line 3a as described above; in the high-level treatment apparatus III used as the other apparatus, contact material holding rods 13 are provided at predetermined intervals at the upper portion of the water line so as to cross the circulation water line 3d, and a plurality of fiber-like contact materials 14 are suspended at predetermined intervals on each of the rods 13.

The fiber-like contact material 14 shown enlarged in FIG.

11 is a strand formed by bundling a required amount of extra-fine carbon fibers or the like, and the holding rod 13 comprises an iron rod, the surface of which is covered with polyvinyl chloride to insulate the carbon fibers. The holding rod 13 is supported by a holder 20 installed at the upper portion of the side wall of the bath body 1 forming the circulation water line 3d (see FIG. 11).

High-level treatment will be described below concretely; the secondarily treated water T2 treated by the secondary treatment apparatus II is taken in from the circulation water line 3a by an overflow pipe (or a communication pipe) 15 and flows into the settlement bath 16 of the high-level treatment bath III. In the settlement bath 16, the secondarily treated water T2 is separated into solid and liquid, that is, settled sludge and top clear water.

Instead of the overflow pipe (or the communication pipe) a system for simultaneously carrying out aeration and flow acceleration by using an air lift pump 21 (not shown in FIG.

see FIG. 12) can be adopted so that the secondarily treated water T2 is pumped and dropped into the water line 3d. In this case, aeration by dropping can be further carried out; therefore, the efficiency of aerobic treatment (oxidation and decomposition of organic substances and nitrification of ammonia nitrogen) and anaerobic treatment (denitrification of nitrate nitrogen) can be raised. Adesiredpumping apparatus, such as an Archimedes pump, can be used depending on the properties of water to be treated.

Next, the secondarily treated water T2 flown into the water line 3d is introduced into a biological film zone 19a (the area in the circulation water line, wherein the fiber-like contact materials 14 are suspended) formed at predetermined portions from the settlement bath 16 to the circulation water line 3d.

Before starting the high-level treatment utilizing the biological film zone 19a, seed sludge is supplied into the water line and running-in is carried out for a required period just as in the case of the active sludge method or the biological film contact oxidation method conducted conventionally. With this, large amounts of strong biological films can be formed on each fiber-like contact material 14.

As a result, biological oxidation by aerobic treatment due to dissolving and remaining oxygen on the upstream side of the biological film zone 19a, and remaining components not treated by the secondary-treatment are removed; furthermore, denitrification treatment is carried out aerobically in the downstream side area wherein dissolving oxygen has been consumed.

In setting the range of this biological film zone 19a, the interval and quantity of the fiber-like contact materials 14, the amount of aeration and circulation speed are adjusted appropriately in consideration of the quality of water to be treated and the quality of water to be discharged.

In this case, since the holding rods 13 for securing the contact materials 14 are removably mounted on the circulation water line 3d in the present embodiment, the adjustment thereof can be carried out easily. In addition, the method of mounting the contact materials 14 is not limited to that of the present embodiment, but an appropriate method can be adopted; by adopting a means for removably mounting them from the upper portion of the water line, the setting operation of the biological treatment zone 19a can be carried out easily.

Furthermore, since the strand formed of bundled extra-fine fibers is used in the present embodiment, the monofibers are separated from one another in the water line and microorganisms firmly attach to the surface of each monofiber, whereby the attachment density of microorganisms is high, the attachment is firm, and falling hardly occurs.

Moreover, each contact material 14 is installed so as to suspend and shake in water, and biological films can be formed easily and firmly.

With the carbon fibers used for the contact material 14, thick biological films are formed firmly, and biological treatment efficiency (removal speeds and removal ratios of SS, BOD, TN and TP) is high, whereby the quality of treated water can be raised. In particular, it is confirmed that the PAN-based carbon fibers are superior in the attachment condition of microorganisms.

Since the fiber-like contact materials 14 are suspended in the circulation water line 3d as described above, biological treatment is carried out without impairing the circulation flow of water to be treated and without causing clogging due to sludge; in addition, since the extra-fine fiber contact materials 14 are used, the density of the biological film is high. Therefore, treatment efficiency is high, and sludge falls off less, whereby the solid-liquid separation of water to be treated can be carried out easily. Furthermore, since the accumulation of sludge hardly occurs in comparison with the conventional circulation water line treatment, the flowing speed can be made lower, whereby the treatment efficiency can be raised further, and the quality of water to be treated can be enhanced.

The high-level treated water T3 biologically treated while flowing in the abovementioned biological film zone 19a is extracted from the circulation water line 3d, undergoes required aftertreatment 18, and is discharged, after pollutants still included in the treated water are removed by a final treatment bath 17.

FIG. 12 shows an embodiment of still another high-level treatment apparatus being compact in shape.

In this embodiment, after flowing into a settlement bath 16 by an appropriate means, the secondarily treated water T2 is pumped by an air lift pump 21a, aeration and flow acceleration are carried out simultaneously by drop into a circulation water line 3e, and the treated water circulatingly flows in the elliptical circulation water line 3e.

Hereafter, while biological treatment such as denitrification is carried out by a biological film zone 19b 11 j, configured in the same way as the embodiment shown in FIGS.

9 and 10, water is pumped by an air lift pump 21b disposed at the final end portion 22 of the circulation water line 3e, and dropped and supplied into the start end portion 23 of the circulation water line 3e, whereby circulation flow is repeated further (in the embodiment of the secondary treatment II shown in FIGS. 9 and 10, treated water is also extracted by an air lift pump, not shown, from the final end portion of the circulation water line 3d, dropped and flown to the start end portion of the circulation water line 3d, whereby circulation flow is repeated).

The high-level treated water T3 having undergone the high-level treatment is then extracted in the middle of the circulation water line 3e, undergoes aftertreatment in a final treatment bath 17 and an aftertreatment bath 18 provided in a space formed inside the circulation water line 3e, and discharged outside the apparatus.

Experiment data in the case when aerobic treatment was carried out in the secondary treatment apparatus using the shooting flow energy absorber and aerobic and anaerobic treatments were carried out in the high-level treatment apparatus using the contact materials will be described below on the basis of FIG. 13.

In the experiment, BOD concentration, total nitrogen concentration and ammonia nitrogen concentration were measured with respect to inflow raw water secondarily treated water (T2) and high-level treated water (T3) on June 6, June 27 and July 3, 1997, respectively.

FIG. 13 is a bar graph indicating the results of the measurement on which the ordinate represents concentration (mg/L) and the abscissa represents the measurement date, and showing the measurement values of the inflow raw water secondarily treated water (T2) and high-level treated water (T3) measured at the respective measurement dates.

First, as shown in FIG. 13 it is found that the BOD concentration in the secondarily treated water (T2) greatly decreased in comparison with the BOD concentration of the inflow raw water and that the BOD concentration in the high-level treated water (T3) further decreased on every measurement data.

In other words, it becomes clear that the combination of aerobic secondary treatment and anaerobic high-level treatment was effective, and that the contact filter materials trapped aerobic outflow sludge in anaerobic treatment during the high-level treatment process, thereby delivering a stable purifying capability.

Next, as shown in FIG. 13 it is confirmed that the treatment of total nitrogen was carried out obviously even in a short period (about one month) after the start, and the data on July 3 indicates that the concentration of total nitrogen is 10 mg/L or less. In the case when anaerobic treatment capability by the contact filter materials is raised further, it is expected that the concentration of total nitrogen is lowered further.

Furthermore, since the concentration of ammonia nitrogen decreased with the passage of days as shown in FIG. 13 it is found that nitrification required as a precondition for the removal of total nitrogen proceeded properly, and that almost all of the ammonia nitrogen in the inflow raw water R was nitrified in accordance with the data on July 3.

As described above, in any embodiments described above, the quality of water to be treated can be improved by using simple apparatuses.

INDUSTRIAL APPLICABILITY As clarified in the abovementioned descriptions, the industrial applicability of the invention disclosed by the present application is as follows: By providinga weir for forming a shooting flow energy absorber having an openable lower portion in a water line wherein wastewater is circulated to carry out biological treatment, and by using a wastewater treatment method wherein aerobic treatment by only overflow, anaerobic treatment by only underground flow, and both aerobic treatment and anaerobic treatment by both overflow and underground flow can be carried out, aerobic treatment and anaerobic treatment can be selected or combined as desired, whereby it is possible to carry out efficient secondary wastewater treatment suited to the properties of wastewater such as sewage.

By making the lower opening amount of the weir provided in the water line adjustable, the ratio of aerobic treatment and anaerobic treatment can be adjusted, whereby aerobic treatment and anaerobic treatment can be selected or combined as desired; in addition, the ratio of aerobic treatment and anaerobic treatment can be adjusted as desired in accordance with the properties of wastewater, and efficient secondary wastewater treatment can be attained.

More concretely, it is possible to provide a wastewater treatment apparatus comprising a circulation pump t.

for discharging water to be treated from the final end portion to the start end portion of a circulation water line and a weir disposed in the middle of the circulation water line and comprising a vertical wall and an inclined wall for forming a shooting flow energy absorber, wherein either one or both of aerobic treatment carried out by shooting and splashing circulation water overflowing from above the weir and/or anaerobic treatment carried out by passing underground circulation water from an opening portion under the weir, conducted by vertically moving the weir body itself as an integrated unit, or by vertically moving an open/close plate disposed on the vertical wall surface of the abovementioned weir body having an opening portion formed between the weir body and the bottom portion of the water line and secured, or by rotating an open/close valve disposed at the opening portion under the abovementioned weir body having an opening portion formed between the weir body and the bottom portion of the water line and secured, or by inclining a vertical wall formed like a plate constituting the weir body can be selected as desired.

In other words, in the case when the weir body which is movable vertically is secured at the upper position, overflow of circulation water from above the weir is eliminated, and circulation water is flown out only from the submerged opening portion formed between the weir and the bottom portion of the circulation water line, whereby only anaerobic treatment can be carried out.

In the case when the weir body is fixed at the bottom of the bath, water to be treated is overflowed from above the weir body and shot and splashed, whereby only aerobic treatment can be carried out. In the case when the weir body is secured at an intermediate position of the water line in the vertical direction, water to be treated is overflowed from above the weir, and the underground circulation water from under the weir is passed, whereby aerobic treatment and anaerobic treatment can be carried out.

By using means capable of selecting the position of the weir body as desired as described above, awastewater treatment apparatus capable of selecting either one or both of aerobic treatment and/or anaerobic treatment carried out by passing underground circulation water from the opening portion under the weir can be provided.

In the case when the open/close plate provided on the vertical wall surface of the weir body which is secured so as to form the opening portion between the weir body and the bottom portion of the water line is moved vertically, and in the case when the open/close valve is provided at the opening portion between the secured weir body and the bottom portion of the water line, either one or both of aerobic treatment and/or anaerobic treatment can be selected appropriately and easily by adjusting the vertical position of the open/close plate or the rotation position of the open/close valve.

In the case when the vertical wall constituting the abovementioned weir body is inclined with respect to the inclined wall, this vertical wall capable of being inclined acts as an adjustment member capable of selecting either one or both of aerobic treatment and/or anaerobic treatment appropriately, and the opening amount of the submerged opening portion is changed depending on the amount of inclination, whereby the ratio of aerobic treatment and anaerobic treatment can be adjusted easily.

By providing a submerged weir at the bottom portion of the circulation water line around the weir, the flow of circulation water is disturbed, the effect of agitation can be generated, and the effect of anaerobic agitation of underground circulation water can be amplified; by providing the discharge port of the abovementioned pump toward the 39 submerged opening portion, the effect of anaerobic agitation can be amplified further.

By forming the circulation water line in a labyrinth shape by providing partition walls in a zigzag pattern in a nearly square bath body or by forming the circulation water line in the shape of a flat helical water line, water to be treated can be circulated smoothly, and efficient secondary wastewater treatment can be carried out even in a narrow area.

In addition to the abovementioned effects due to the secondary treatment apparatus using the shooting flow energy absorber, by carrying out wastewater treatment using a high-level treatment apparatus having a biological film zone formed in the circulation waterline by using contact materials, organic substances can be decomposed, removed and denitrified effectively.

The present invention can provide a wastewater treatment method and apparatus which is simple in equipment, compact, inexpensive, easy in maintenance and control, suited for small-to-medium-size treatment of sewage, and applicable to both aerobic treatment and anaerobic treatment; in addition, the present invention can provide a wastewater treatment method and apparatus capable of carrying out treatment as desired in accordance with the properties of wastewater.

Claims

1. A secondary wastewater treatment method for carrying out biological treatment by circulating primarily treated water in a water line after removal of deposits, impurities and the like contained in wastewater, wherein a weir for forming a shooting flow energy absorber having an openable lower area is provided inside said water line so as to be able to carry out aerobic treatment by only overflow, anaerobic treatment by only underground flow, and both aerobic treatment and anaerobic treatment by both overflow and underground flow.

2. A wastewater treatment method in accordance with Claim 1, being capable of adjusting the ratio of aerobic treatment and anaerobic treatment as desired by adjusting the lower opening amount of said weir.

3. A secondary wastewater treatment apparatus for biologically treating primarily treated water in a circulation water line after removal of deposits, impurities and the like contained in wastewater, comprising a circulation pump for discharging treated water drawn from the final end portion of said circulation water line, and a weir disposed in the middle of said circulation 42 water line and comprising a vertical wall and an inclined wall to form a shooting flow energy absorber, wherein either one or both of anaerobic treatment carried out by passing underground circulation water from an opening portion under the weir and/or aerobic treatment carried out by shooting and splashing circulation water overflowing from above weir by using one of the means for vertically moving said weir body itself, for vertically sliding an open/close plate disposed on the vertical wall surface of said weir body having an opening portion formed between said weir body and the bottom portion of said water line and secured, for rotating an open/close valve disposed at the opening portion under said weir body having the opening portion formed between said weir body and the bottom portion of the water line and is secured, or for inclining a vertical wall constituting said weir body can be selected as desired.

4. A wastewater treatment apparatus in accordance with Claim 3, wherein the angle of the inclined wall formed on the downstream side of said weir body is made changeable.

A wastewater treatment apparatus in accordance with Claim 3, wherein a submerged weir is provided at the bottom portion of said circulation water line around said weir body.

6. A wastewater treatment apparatus in accordance with Claim 4, wherein a submerged weir is provided at the bottom portion of said circulation water line around said weir body.

7. A wastewater treatment apparatus in accordance with Claim 5, wherein the discharge port of said circulation pump is provided toward the submerged opening portion for forming an underground flow formed under said weir.

8. A wastewater treatment apparatus in accordance with Claim 6, wherein the discharge port of said circulation pump is provided toward the submerged opening portion for forming an underground flow formed under said weir.

9. A wastewater treatment apparatus for carrying out high-level treatment by supplying secondarily treated water treated by the wastewater treatment method in accordance with Claim 1 or 2, wherein by providing a plurality of flexible fiber-like contact materials having portions shaken by circulation water to be treated at predetermined intervals in the flowing direction in said circulation water line, said contact materials are allowed to hold onto organisms to form a biological treatment zone, and said secondarily treated water is circulatingly flown to carry out said aerobic treatment and said anaerobic treatment.

A wastewater treatment apparatus for carrying out high-level treatment by supplying secondarily treated water treated by said wastewater treatment apparatus in accordance with any of Claims 3 through 8, wherein by providing a plurality of flexible fiber-like contact materials having portions shaken by circulation water to be treated at predetermined intervals in the flowing direction in said circulation water line, said contact materials are allowed to hold onto organisms to form a biological treatment zone, and said secondarily treated water is circulatingly flown to carry out said aerobic treatment and said anaerobic treatment.

11. A wastewater treatment apparatus in accordance with Claim 9, wherein said flexible fiber-like contact material is a strand formed of bundled fibers.

12. A wastewater treatment apparatus in accordance with Claim 10, wherein said flexible fiber-like contact material is a strand formed of bundled fibers.

13. A wastewater treatment apparatus in accordance with Claim 9, wherein said flexible fiber-like contact material is formed of carbon fibers.

14. A wastewater treatment apparatus in accordance with Claim 10, wherein said flexible fiber-like contact material is formed of carbon fibers.

A wastewater treatment apparatus in accordance with Claim 11, wherein said flexible fiber-like contact material is formed of carbon fibers.

16. A wastewater treatment apparatus in accordance with Claim 12, wherein said flexible fiber-like contact material is formed of carbon fibers.