DK143841B - ROTABLE BIOLOGICAL CONTACT SUPPLIER FOR USE BY WASTE CLEANING - Google Patents

Description

MEF

(19) DENMARK

| J | (12) PUBLICATION MANUAL od 1438 ^ 1 B

Dl The Patent and Trademark Office

(21) Application No. 2551/75 (51) | nt.CI.3 C 02 F 3/08 (22) Filing Day 9 · 1975 (24) Race Day 9 · May 1975 (41) Aim. available 1 1 · Nov. 1975 (44) Posted 19 Oct. 1 98l (86) International application no. - (86) International filing day (85) Transfer day "(62) Master application no."

(30) Priority 10 · May 1 972, 2520 ^ 8, US

(71) Applicant AUTOTROL CORPORATION * Milwaukee, US.

(72) Inventor Donald N. Gass, US: David G. Proeser, US.

(74) Associate Engineer Hofman-Bang & Bout ard.

(54) Rotatable biological contact device = hole for use in cleaning spll = devand.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a rotatable biological contact assembly for use in wastewater purification, which is of the large surface type comprising a plurality of means spaced along an axis and partially submerged in wastewater to be purified.

One of the known, but until recently only little-used methods metoder for biological treatment of wastewater involves the use of “contact aggregates that provide surface for the growth of O aerobic bacterial sludge. Generally, the contact assemblies are rotated in a partially submerged position in the wastewater, so that alternating exposure of the contact assembly surface to the wastewater and to the oxygen in the atmosphere produces growth of a bacterial film covering the surfaces of the contact assembly. The bacterial sludge on such surfaces consists mainly of aerobic bacteria which are capable of absorbing, adsorbing, coagulating and oxidizing the undesirable organic constituents in the wastewater and changing such constituents into harmless material forms. The use of rotary contact units also increases the transfer of oxygen to the waste water in the tank through which the contact units rotate. This promotes the propagation or synthesis of the aerobic bacteria already present in the mixed wastewater and in the bacterial film and increases the ability of the aerobic bacteria to affect the wastewater and reduce it to harmless forms.

As early as the beginning of this century, it was recognized that maximum efficiency could only be approximated by providing as large a surface as possible on which the biological sludge could grow. Thus, in the specification of German Patent No. 135,755, issued October 21, 1902, it was proposed to construct the contact assemblies as rotating wheels consisting of open porous materials, such as eagle's quill, to provide a large surface on which the bacteria will settle. and grow. Later, attempts have been made to obtain the large surface area by using closely spaced circular discs arranged along a shaft and generally constructed of a foamed plastic material. However, there are practical limits to the amount of surface that can be provided by the closely spaced discs. First, the slices must have a substantial thickness to obtain the necessary lateral stability and strength. Second, if the disks are placed too tightly together to achieve a large surface area, the growth of bacterial sludge will bridge the space between neighboring disks and actually greatly reduce the effective surface area. Third, the larger the volume of wastewater displaced by the wafers, the closer the wafers are placed together, which reduces the wastewater residence time in the tank and reduces the biological treatment.

It has also been proposed in DE Patent Application P 18 15 001.1 published on June 25, 1970, to form a contact assembly of several segment-shaped or cube-shaped filter sections disposed side-by-side on a support frame projecting from a shaft where the filter sections are composed of a number of stacked sheets forming a wasp-like structure.

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There are also related methods for biological treatment of wastewater, whereby the desirability of providing a large surface area for the growth of the biological mass has been recognized. Thus, in modern forms of drip filters, a gasket consisting of alternating straight sheets and vacuum-shaped corrugated sheets of thin plastic material (U.S. Pat.

U.S. Patent No. 3,403,095 issued September 24, 1968, and U.S. Pat.

3,260,511, issued July 12, 1966). Also in the purification of water assemblies by the oxidation of the organic material therein, in the specification to US Patent No. 3,235,234, issued February 15, 1966, discloses a submerged aggregate formed by a series of plates with outgrowths adjacent to neighboring plates to form a plurality of winding paths between the plates in both horizontal and vertical directions. The passages provide space for a flow of water and of oxygen provided by mechanical aeration equipment.

Although the above shows that it has long been recognized, both in the art of rotatable biological contact sets and in the related technique of biological treatment of wastewater, that a large surface area is required for the most efficient growth of the bacterial sludge, there is no In the prior art, a rotatable extended surface biological contact device is obtained which is capable of achieving optimum operating conditions at low cost. With the contact assembly according to the invention, a large surface is obtained in a strong, inexpensive unit which is lightweight and accommodates a minimum volume of waste water in the tank in which it operates, so that a larger volume of waste water can be retained in the tank for treatment.

The rotatable biological contact assembly according to the invention is characterized by the characterizing part of claim 1.

The contact assembly of the invention can also be described as a series of thin-walled, generally circular plates disposed side-by-side along a central axis of rotation such that adjacent plates form a plurality of radially directed spaced passageways dispersed along the perimeter of the plates and open to the periphery, and a a series of generally concentric spaced passages extending between adjacent pairs of radial passages and at each end open to a radial passage.

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The contact assembly of the invention may have several embodiments, each of which represents an improvement over the prior art, and some of the embodiments are in themselves improvements over other embodiments of the invention. In the following detailed description, the preferred embodiments of the invention will be described with reference to the accompanying drawings.

The characteristics and advantages of the various embodiments, in addition to the above, will be described in connection with the drawing, in which fig. 1, 2, 3, 4 and 5 are views of a first embodiment of a rotatable biological contact assembly according to the invention; 1 is a front elevational view of a pair of contact assemblies mounted in a treatment tank; and FIG. 2 is a side view of one of the contact assemblies of FIG. 1 in the plane along line 2-2 of FIG. 1, while FIG. 3, 4 and 5, several sections of the rotatable biological contact assembly seen in the planes along the lines are identified in FIGS. 1 and 4, FIG. 6 and 7 are views of another embodiment of a contact assembly according to the invention, in which fig. 6 is a front elevational view of the contact assembly with parts cut away for illustration, and FIG. 7 is a vertical section taken in the plane along line 7-7 of FIG. 6, FIG. 8, 9 and 10 are views of a third embodiment of a contact assembly according to the invention, in which fig. 8 is a front elevational view of the contact assembly with parts cut away for illustration, FIG. 9 is a side view of the plane taken along line 9-9 of FIG. 8, and in which FIG. 10 is a vertical section taken in the plane along line 10-10 of FIG. 8, FIG. 11 and 12 are views of a fourth embodiment of a contact assembly according to the invention, in which fig. 11 is a front elevational view of the contact assembly with parts cut away for illustration, and FIG. 12 is a front elevational view of a flat sheet which forms part of the contact assembly of FIG. 11, 143841 FIG. Fig. 13 is a plan view of a continuous strip of a shaped thin-walled sheet material which can be cut along the indicated lines to form trapezoidal sections; 14 is a sectional view of the continuous strip of FIG. 13 taken in the plane along line 14-14 of FIG. 15, FIG. Figures 15 and 16 are views of a fifth embodiment of a contact assembly according to the invention, utilizing the features of Figs. 13 and 14 show trapezoidal sections, FIG. 15 is a front elevational view of the contact assembly; and FIG. 16 is a section taken in the plane along the line 16-16 of FIG. 15th

In FIG. 1-5 representing the first embodiment of the invention, a pair of rotatable biological contact assemblies 20 and 21 are mounted in a tank 22 with a water inlet 23 and outlet 24. The contact assemblies 20 and 21 are each mounted at their rotational axis on a hollow square shaft 25 which, in turn, is mounted on the round shaft stub 26 mounted in bearings 27 mounted on the tops of the tank walls 22 and connected to a suitable drive mechanism for rotating the contact assemblies 20 and 21. The contact assemblies 20 and 21 can be used in tanks of various shapes. and · sizes, and the tank 22 does not form part of the present invention. As a result, the inlet and outlet of the tank 22 are shown in stylized form only.

Each of the contact assemblies 20 and 21 consists of a number of identical circular thin-walled shaped sheets 28. A pair of sheets 28a and 28b are assembled face-to-face to form a slice member 29, and the plates 28a and 28b of each slice member 29 abut or are associated with The plates 28b and 28a, respectively, of each neighboring disk member 29. The faces 28 are designed such that when assembled to form a disk member 29, they will define a plurality of radial passages 30 extending from a central hub and open to the periphery of the disk member. 29. The two plates 28a and 28b constituting each disc element 29 are also each shaped to define a series of concentric passages 31a, 31b, 31c, etc. which are hexagonal in cross section (see Fig. 3) and which extending between adjacent pairs of radial passages 30 and open to the radial passages 30 at each end.

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To delineate the respective radial and concentric passages 30 and 31, each plate 28 is formed with a central hub portion 32 which lies at one end plane of the plate 28 and abuts the identical hub portions 32 of the second plate 28 of each disc element 29. Each plate 28 is also formed with alternating end wall portions 33a, 33b, 33c, etc. which alternate in the plane of the central hub portion 32 and in a different offset end plane of the plate 28. The alternating end wall portions 33 are joined by inclined connecting wall portions 34a, 34b, 34c, etc., so that each plate 28 provides half of the required surfaces for defining the concentric passages 31. Each plate 28 is further provided with walls 35 which are in plane midway between the two end planes of plate 28 and which are connected by means of transition plates to the end wall portions 33 of the concentric passage 31 so that each plate 28 provides half of the surfaces defining the radial passages 30.

in addition to the radial passages 30 and concentric passages 31 formed within each disc element 29, neighboring disc elements 29 also define radial passages 36 and concentric passages 37a, 37b, 37c, etc. between themselves. Accordingly, the row of disc elements 29 disposed side by side together produces a honeycomb-like pattern of concentric passages 31 and 37, as shown in FIG. 3, and a continuous series of radial passages 30 and 36 extending along the axis of rotation of the contact assembly, as shown in FIG. 4, the concentric passages 31 and 37 opening at each end into the radial passages 30 and 36, as shown in FIG. 5th

During operation, the contact assemblies 20 and 21 are partially submerged in the wastewater in the tank 22. As the contact assemblies 20 and 21 are rotated, wastewater will enter the concentric passages 31 and 37 through the radial passages 30 and 36 as they are submerged in the wastewater, and will flowing through the concentric passages 31 and 37 and out of the radial passages 30 and 36 as they exit the wastewater. In such a way, wastewater to be treated is contacted with the entire submerged inner and outer surface of the contact assemblies 20 and 21. Similarly, the entire inner and outer surface of the contact assemblies 20 and 21 are exposed to the oxygen in the atmosphere over the wastewater as the atmosphere circulates. through the radial and concentric passages. An aerobic bacterial film will grow on the surface of the contact assemblies nourished by the alternate exposure of the surfaces to the nutrients in the wastewater and oxygen in the atmosphere. When the film builds up to a thickness that can no longer support itself, it will peel off and be washed out of the connector passages by the water movement therethrough. The sludge peeled from the contact assemblies may settle on the bottom of the tank 22 where it can be collected and removed, or the sludge may be kept in suspension in the effluent for disposal and removal at subsequent stages of treatment.

In the first embodiment as well as in the other embodiments to be described, the plates 28 are formed of thin sheet material, which may preferably have a thickness in the range of 0.5 to 0.75 mm. The plates 28 are preferably formed to the form described by standard vacuum forming methods. The material is preferably a plastics which is biologically inert. Suitable materials include polystyrene and polyethylene. The plates 28 may be joined together to form the disc elements 29, and the disc elements 29 may be joined to form the row by solution welding in the case of a suitable material, such as polystyrene, or by other forms of welding, such as ultrasonic welding, in the case of polyethylene, where solution welding not used. The large flat impact surface areas provided by the end wall 33 mitigate welding problems which may be caused by the non-radial conformity of neighboring plates.

The contact assemblies 20 and 21 present a large surface area on which biological sludge can be grown, as compared to the foam plates used to date for rotatable biological contact assemblies.

For the same diameter of the assembly, and assuming that the thickness of a disc element 29 is the same as that of the space between the flat surfaces of these previously known foam discs, the surface area may be almost twice that of the foam discs. At the same time, due to the thin-walled structure used, the contact assemblies 20 and 21 will accommodate a much smaller volume of waste water in the tank, with the result that a larger volume of waste water is retained in the tank at any given time. The resulting increased wastewater residence time increases the removal of the unwanted organic material for the wastewater. Together, similar to standard foam discs, the structure of FIG. 1-5 approx. one-tenth of their volume.

The size of the radial and concentric passages must be large enough that no bacterial sludge will build up to such an extent that the passages are blocked. As a hint of the size of the passengers, the distance between two end planes of each plate 28 may be about 17 mm.

In FIG. 1 to 5, the first embodiment of the invention has been illustrated with small diameter contact assemblies 20 and 21 to emphasize the arrangement and placement of concentric passages 31 and 37. In use, the contact assemblies according to the invention will be of much larger relative diameter and will consequently thereof having many more rows of concentric passages 31 and 37.

If large diameter assemblies are desired, handling the plates can be difficult physically. 6 and 7 illustrate a way to facilitate the handling and assembly of large diameter contact assemblies.

In the embodiment of FIG. 6 and 7, each plate of the contact assembly 40 is composed of a group of identically shaped circular sectors 41.

In the particular embodiment shown, a group of three sectors 41, each having an inner angle of nearly 120 °, is used to form each plate. Three sectors 41a forming a plate are then joined face to face with three other sectors 41b forming a second plate to form a disc element. The sectors 41 are shaped similarly to the continuous plates 28 in the first embodiment, defining a plurality of radial passages 42 and concentric passages 43, both between total sectors of each disk element and between adjacent disk elements. That is, each of the sectors 41 is configured to delineate half of each of the concentric passages 43 and half of each of the radial passages 42. Many more radial passages are provided in the contact assembly 40 of FIG.

6 and 7 than in the contact assemblies 20 and 21 of the first embodiment because of the larger diameter used so as to ensure sufficient openings for the flow of water and oxygen into and out of the concentric passages.

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To increase the aggregate strength, the edges 44 of the sectors 41a in one group of a slice element are offset from the edges 44 of the sectors 41b of the other group at a fixed angle such that no sector 41 has its edges 44 aligned with the edges 44 of the sectors of the group of either side of it. Sectors 41 may be mounted on a square hollow shaft 45 * and the inner perimeter 46 of each sector 41 is preferably bounded by a series of concentric squares of the same size as shaft 45 and angularly displaced from each other by said fixed angle. With such a construction, the square shaft 45 can be utilized to align sectors 41 with one another during assembly.

In order to increase the torque transfer capacity between the shaft 45 and the disk element assembly, the space between the outer surface of the square shaft 45 and the inner perimeters 46 of the sectors 41 and the space between neighboring sectors 41 at the shaft 45 is preferably filled with a rigid plastic foam 47 · In the embodiment of FIG. 8 to 10, the rotatable biological contact assembly 50 is formed by alternating thin-walled flat plates 51 and thin-walled shaped plates 52, each pair of flat and shaped plates 51 and 52 defining a disc element 55 and the assembly of disc elements 55 mounted on a square hollow shaft. 54 · The flat plates 51 are continuous, but the shaped plates 52 are provided with spaced apart radial cuts 55 extending from a central hub portion 56 and increasing in width with the distance from the shaft 54.

The shaped plates 52 are provided, as in the previous embodiments, with alternating end wall portions 57a, 57b, 57c, etc., which lie in two end planes of the formed plates 52, and which are connected by sloping connecting wall parts 58a, 58b, 58c, etc.

Thus, concentric passages 59a, 59b, 59c, etc. are defined between each formed plate 52 and flat plate 51 in each disc element 55, and further concentric passages 60a, 60b, 60c, etc. are delimited between the formed plate 52 and the flat plate 51. in the adjacent disk elements 55, as shown in Fig. 10. The concentric passages 59 and 60 are, respectively, open at their ends to the radial cuts 55, and the cuts 55 together with the flat plates 51 of the neighboring disc elements 55 define the radial passages 61.

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The embodiment of FIG. 8-10 have certain advantages over the previous embodiment. First, it is cheaper because only half of the plates need to be vacuum formed. Second, the distance between the end planes of each shaped plate 52 to provide approximately the same cross-sectional area of the concentric passages 59 and 60 as in the preceding embodiments will be approximately twice the distance of the shaped plates in the previous embodiments. This causes the radial passages 61 to become larger, and will further reduce the possibility of clogging.

The radial passages in the previous embodiments, like the radial passages 61, could be designed with increasing cross-sectional area as the distance from the axis of rotation increases. This has the advantage of providing capacity at the radial extremes of the radial passages to receive the increased flow which will naturally occur at such points as the contact assembly 50 rises from the wastewater.

The embodiment of FIG. 11 and 12 are similar to that of FIG. 8-10 in that the contact assembly 70 is made up of alternately flat plates 71 and shaped plates 72. However, the shaped plates 72 are continuous and are shaped in the same manner as the plates 28 in the first embodiment. That is, the shaped plates 72 include wall portions 73 midway between the end planes of the plates 72 which provide half of a number of radial passages 74.

Then, the flat plates 71 are each provided with radial cuts 75 which correspond to the location of the wall portions 73 such that each radial passage 74 is bounded by the wall portions 73 of each neighboring pair of shaped plates 72. This embodiment has the advantage of being easier to mold. because it is simpler to cut the material into flat sheets 71 than to make it into the shaped sheets. Likewise, the wall portions 73 of the formed plates 72 tend to hold the end walls and connection walls defining the concentric passages in place during assembly so that they do not flatten out and grow in diameter.

In the embodiment of FIG. 13-16, the contact assembly 80 is made up of disc elements 81 which consist of a flat circular plate 82 and a group of trapezoidal shaped sections 85 which together constitute a shaped plate. As shown in FIG. 13 and 14, n 143841 the trapezoidal shaped sections 83 can be made by cutting from a continuous shaped strip 84 having a cross-sectional shape as in FIG. 14 with alternately shaped end walls 85 arranged in two different planes and connected by connecting walls 86. The trapezoidal sections 83 are spaced apart along the circumference of each flat plate 82 so as to define the radial passages 87 between the ends of the trapezoidal sections 83. Generally concentric passages 88 are bounded between the trapezoidal section 83 and the flat plate 82 on each side thereof.

The flat plates 82 are preferably provided with an inner circular opening 89 which is larger than a square hollow shaft 90 on which the assembly is mounted. A rigid plastic foam 91 is located around the shaft 90 in the space between the shaft 90 and the central openings 89 of the flat plates 82 and between adjacent plates 82 and the shaft 90, as shown in FIG. 16. In this way, a solid rigid foam core is formed around the shaft 90.

The embodiment of FIG. 13-16 have the advantage that the shaped sections 83 can be made using plastic extrusion processes rather than the more expensive vacuum forming. The passages 88 are parallel to a tangent to the flat plates 82 and, as a result, are not strictly concentric passages. However, the parallel passages 88 are to be understood as included in the term "general concentric passages" as used herein in this specification with claims.

It will be noted in FIG. 16, that the trapezoidal sections 83 in each level are inverted by the adjacent levels. The purpose of such an arrangement is to concentrate the contact surfaces between the formed sections 83 and the flat plates 82 at as few points as possible. In addition, the number of points at which the shaped sections 83 and the flat plates 82 are welded is reduced because the shaped sections 83 on each side of a flat plate 82 can be joined to the flat plate in one step. A similar arrangement for the shaped plates 52 of FIG. 8-10 and the shaped plates 72 of FIG. 11 and 12 can be used with the same advantages.

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The contact assembly of each embodiment can be made by joining each plate with each adjacent plate so as to form a continuous joined structure along the entire length of the contact assembly. In the other extreme, individual disc means may be formed which abut adjacent discs. More generally, however, a stack of plates comprising multiple disc means will be joined together and several stacks will be mounted in a row to form a length of the contact assembly. Due to the previously described designs, a continuously joined length of contact assembly will have sufficient strength that the central shaft does not need to support the contact assembly. A continuously joined length connector may also have sufficient torque transmitting capacity that only shaft stubs need to be used at the ends of the connector to carry the connector in the tank and transfer torsional torque from the power source to the connector.

From the foregoing, it will be seen that, according to the invention, contact assemblies with large surface area, low weight and low volume can be made from low cost materials.

Claims (10)

A large-surface rotatable biological contact assembly comprising a plurality of means, spaced apart along an axis and partially submerged in wastewater to be purified, characterized in that the members are made up of parts (28a, 28b, 4la, 4lb, 51, 52 , 71, 72, 82, 85) forming double-walled disc elements (29, 53, 81) along said shaft (25, 45, 54, 90), said disc elements (29, 53, 81) forming a plurality of radially spaced apart passageways (30, 36, 42, 61, 74, 87) open at the periphery of the disc elements (29, 53, 81), the disc elements (29, 53, 81) each having a series of inner, generally concentric, separate passageways (31a, 31h, 31c, 43, 59a, 59b, 88) which are open at each end to a radially directed passage (30, 36, 42, 61, 74, 87), and that adjacent disc elements (29, 53 , 81) form additional rows of substantially concentric spaced passageways (37a, 37b, 37c, 43, 60a, 88) open at each end to a radially directed passage (30, 36, 42, 61, 74, 87 ). Assembly according to claim 1, characterized in that each disc element (29) consists of a pair of identical thin-walled shaped plates (28a, 28b), assembled face-to-face, and assembled back-to-back with the plates of neighboring disc elements (29). Assembly according to claim 2, characterized in that each plate (28a, 28b) is formed with walls defining half of a number of radial passages (35) uniformly distributed along the circumference of the plate, in such a way that radial passages (30, 36) are formed between the plates (28) of each disc element (24) and between the adjacent plates (28a, 28b) of each pair of neighboring disc elements (29). Assembly according to claim 3, characterized in that the radial passages (30, 36) are uniformly spread along the circumference of the plate (28) and that the concentric passages (31a, 31b, 31c, 37a, 37b) are each formed as a circular arc with the center of the axis of rotation. An assembly according to claims 1-4, characterized in that each plate (28a, 38b) is formed with a series of alternately arranged end walls (33a, 33b ....) lying in two separate planes generally perpendicular to each other. axis of rotation and with connecting walls (34a, 34b, 34c ....) connecting alternating end walls to one another to delimit half of the concentric passages mentioned (31a, 31b, ..... 37a, 37b), and each plate (28a, 28b) are also formed with walls defining half of a number of said radial passages (30, 36), including walls (35) which lie between the planes of said end walls of the concentric passages. Assembly according to claim 1, characterized in that each of the disc elements consists of a pair of identical thin-walled shaped plates (4a, 4lb), each group consisting of identical circular sectors (41) forming a substantially continuous circular disk, whereby the sectors (41) of each group are joined face-to-face with the sectors of the other group of said pair and are connected face-to-face with the sectors of the neighboring disk element. Assembly according to claim 6, characterized in that the sectors (41) in each group are offset in the circumferential direction from the sectors (4l) in the second group of the disk element and from the adjacent sectors in the neighboring disk elements. Assembly according to claim 1, characterized in that each of the disc elements consists of a flat thin-walled plate (51) and a shaped thin-walled plate (52), wherein the shaped thin-walled plate is joined to the flat plate and abuts against the flat plate. , in the adjacent disk element, each shaped plate (52) having such a shape as to define said concentric passages (59b, 59c, 60, 60c) with the flat plate (51) in its disk element and with the flat plate (51) in the adjacent disc element. Assembly according to claim 8, characterized in that the radial passages (61) are formed by radial cuts (55) in each shaped plate, the cuts (55) being evenly distributed along the circumference of the shaped plate. An assembly according to claim 8 or 9, characterized in that each shaped plate (72) has a shape defining one half of a number of radial passages (74) uniformly distributed along the circumference of the plate (72), and each flat plate (71) is provided with corresponding cuts (75) at the radial passages (74) of