DK142571B - Multipurpose aeration apparatus and method for making the same. - Google Patents

Description

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BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a multi-jet aeration module for supplying a liquid below the liquid level in an aeration tank comprising a plurality of radially spaced nozzles arranged to dispense liquid from a liquid supply line, mixing the liquid prior to delivery from the nozzles. gas supplied from a gas line. Such an aeration module is particularly used for the treatment of wastewater in which air or other oxygen-containing gases are introduced into the wastewater to reduce the biochemical oxygen demand. Although the term "air" will be used from time to time in the following description, it is to be understood that the invention is sufficiently broad to include the use of other oxygen-containing gases including, but not limited to, atmospheric air.

There are a number of well-known liquid treatment methods in which oxygen is supplied to the liquid to purify or, more specifically, to reduce the biochemical oxygen demand in the liquid. Eg. For example, one of the most widely used wastewater treatment systems, namely the activated sludge system, depends to a large extent on the introduction of oxygen into the wastewater to reduce the biochemical oxygen demand to acceptable limits.

There are also several known methods and systems for introducing oxygen into the liquid to be treated. One of the simplest and most inexpensive methods utilizes solely the collection of the wastewater into a pond or tank which is open, so that atmospheric air has free access to the tank. Some oxygen from the air will then be transferred to the wastewater and ultimately reduce its oxygen demand. However, this is an extremely slow process that cannot always be accomplished, especially not in key inhabited areas where the capacity of a wastewater treatment plant must be large.

In another method for reducing the biochemical oxygen demand in wastewater, the liquid is also collected in a pond or electricity. pressurized air or oxygen is introduced through a pipe or diffuser directly into the wastewater below its surface. This system increases the rate at which the biochemical oxygen demand is reduced, but gives rise to high operating costs 2 142571 in the form of a large energy consumption for air blowers or compressors and the like.

In yet another known method, large rotating brushes are used which are partially immersed in the liquid and rotated slowly so that the brushes themselves are eventually lifted out of the liquid and into the atmosphere from which they absorb air, after which they are lowered into the liquid, and a portion of the recorded is transferred to the wastewater. This system also results in a significant consumption of energy and also has one or more large rotating brushes which are exposed to pollution and wear.

It has been found that one of the most appropriate methods of introducing air into wastewater is to use nozzle aerators which utilize the venturi principle. In this method, liquid is pumped through a spray nozzle at a high velocity, thereby developing a negative pressure on the outlet side of the nozzle. A mixing chamber or mixing zone surrounds the outlet end of the liquid nozzle and is connected directly or indirectly through an air compressor to the external atmosphere. The liquid jet, which flows out of the liquid nozzle at high speed, mixes with or enters the air in the mixing zone, and air and liquid are then injected directly into the effluent under its surface through the liquid-air nozzle.

This system of nozzle aerators has a greater efficiency of the oxy-gene fluid transfer than the prior art systems. Therefore, the introduction of air or oxygen into wastewater by means of nozzle aerators is particularly advantageous in view of the plant's capacity, efficiency and operating costs.

The nozzle aeration principles have been used in a number of wastewater treatment plants including activated sludge systems in which the introduction of air or oxygen into the wastewater is carried out in what has usually been called an aeration tank. The nozzle aerators used in such systems are made of metal, usually machined castings of bronze or electricity. like. Such jet generators provide an efficient air-liquid transfer but are quite costly to manufacture. The installation of a nozzle aeration system has therefore been relatively expensive compared to other known systems.

English patent specification 621,880 discloses a nozzle aeration system with a number of radial water injection nozzles. Each of the nozzles is connected to overhead lines for injecting a waterborne stream of air bubbles into the wastewater into a tank. A central water supply line is surrounded by an annular air line which is connected to air lines leading to each nozzle. Each water-air nozzle is designed separately, and oriented separately with respect to the other nozzles of the system, and has its own air line and its own water line made of standard pipes. Therefore, the system is relatively large and heavy.

From usa. No. 3,587,975 discloses another nozzle aeration plant. The jet nozzles are located here at a suitable distance on two rectilinear radially extending arms. The arms function simultaneously as water supply channels. The air is fed through a separate duct at a distance from and above the liquid duct. From this duct, separate transverse ducts lead down to each nozzle.

The many separate channels make the plant expensive to manufacture and heavy to work with.

The object of the invention is to provide ways in which to reduce the installation costs of a nozzle aeration plant and at the same time improve the performance of such a plant not only with regard to the materials used in the manufacture of the nozzle aerators, but also with regard to the design, so that also the operating costs * can be reduced.

This object is achieved according to the invention in that the nozzle aerator consists of a liquid duct made of a tubular, thin plate with a plurality of longitudinally spaced and peripherally arranged liquid nozzles, and a parallel connected air duct made of a thin plate outer wall outside the liquid channel and forming a passage therebetween, the outer wall being provided with a number of liquid-air nozzles, the number of liquid-air nozzles corresponding to the number of liquid nozzles, and where the air-liquid nozzles are arranged coaxially with the liquid nozzles to provide of one into a shaped module. Hereby a multi-jet U2571 4 aeration module is obtained, in one piece, with adjacent parallel liquid and air ducts with pressurized liquid, from which liquid and air will be sprayed out of the liquid-air nozzles and into the waste water in the tank. This aeration module is simple and inexpensive to manufacture and has a modest flow resistance to the surrounding wastewater, which must be rotatable.

In a preferred embodiment, the liquid and air ducts are made of fiberglass, just as the liquid jet nozzles and liquid-air jet nozzles may consist of fiberglass to reduce the weight and facilitate the manufacture of the aeration module.

The radius of the air duct may be smaller than the radius of the liquid pipe, whereby the cross-section of the two ducts together takes the form of a tear drop. This reduces the liquid resistance of the module as the waste water in the tank passes the aeration module.

The aeration module unit, formed by the combination of the liquid duct and the air duct, may further comprise an outer layer of wire-wound fiberglass to strengthen the tubular structure and to increase durability.

The invention also relates to a method of manufacturing the aeration module. The method is characterized in that a thin-walled, longitudinal and constant cross-sectional liquid pipe is made of fiberglass, that several boreholes are provided in a longitudinal direction and at regular intervals in the surface of the liquid pipe, that a fiberglass nozzle is bonded or attached to the liquid pipe in each borehole. a longitudinal, thin-walled component part of a piece with a constant semicircular cross-section is made of fiberglass and fixed to the liquid pipe in such a way that an enclosed air duct is formed between the two thin-walled portions such that a number of boreholes corresponding to the number and location of boreholes in the liquid pipe is formed in the outer wall of the air duct and a fiberglass liquid-air jet nozzle is bonded or attached to the air duct in each of the boreholes in the air duct coaxially with each of the liquid nozzles in the liquid pipe. Thereby a particularly simple manufacturing method is obtained.

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By a particularly convenient method, the ducts are made of circular tubes, the air ducts being also made of a circular tube having a smaller diameter than the liquid tube and longitudinally intersected to form two semicircular segments which can then be used to form two modules.

BRIEF DESCRIPTION OF THE DRAWINGS In the following, the invention is explained with reference to the drawing, in which FIG. 2 is an enlarged top view of the aerator; FIG. 3 shows the one shown in FIG. 1 is a side view of FIG. 4, the aerator seen along line IV-IV in FIG. 3, FIG. 5 is a sectional view taken along line V-V of FIG. 3, FIG. 6 is a side elevation of a liquid lute nozzle; and FIG. 7 is a side view of a liquid nozzle.

In FIG. 1, an aeration tank 10 with wastewater to be treated is shown. The idea is circular, but can take other forms.

In the tank, there are two multi-nozzle aeration modules 11 which are immersed in the wastewater. The two modules may be of the same design and arranged in such a way that they promote the flow of waste water in the tank 10 in a counterclockwise direction. The advantage of this arrangement is that there is produced a movement of the wastewater, thereby keeping solid particles flowing.

Each of the modules 11, see FIG. 2 and 3, has an elongated shape and is provided with a plurality of liquid-air nozzles 12. A pair of flanges 13 at each end of the module 11 can receive a pair of end caps 14 which can be secured to the flanges 13 by suitable fastening means such bolts 16, see FIG. 4th

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A pipe 18 extends from that end 17 of the module 11 and is adapted to supply air or other oxygen-containing gases from a supply line 19 to the module 11. A conduit 21 extends down from the opposite end 20 of the module 11 and is arranged to supplying pressurized wastewater to module 11 from a supply line 22.

The module 11 is as shown in FIG. 5, a unit structure comprising various components, such as a cylindrical tube 23, forming the wastewater duct which is to supply wastewater to the various liquid-air nozzles 12. The duct 23 is tubular and in a preferred embodiment is made of spun lightweight fiberglass filaments. The liquid channel 23 preferably extends one piece throughout the length of the module 11 and is manufactured by known methods using a solid glass fiber wall, with no measures being initially taken for the nozzles 12.

Another means consists of an air duct 24 which is also made of lightweight fiberglass filaments. The duct 24 also preferably extends along the entire module 11 and is first manufactured as a tube or cylinder and cut longitudinally to form the substantially semicircular cylinder shown in FIG. 5. The method whereby the air duct 24 is made of a straight circular cylinder, which is divided into two identical semi-circular cylinders, has the advantage that two air ducts 24 for two modules 11 can be made out of a single fiberglass tube.

The radius of the air duct 24 is smaller than the radius of the duct 23. In the preferred embodiment, the radius of the former is generally 2/3 of the radius of the latter to provide a tear drop shape in cross-section for reasons which will become apparent hereinafter.

The air duct 24 is bonded or attached to the outer surface of the liquid duct 23 by a suitable adhesive, such as an epoxy resin 26. The resin bond can form a weld seam running along the entire length of the liquid duct 23 to provide not only air-liquid seal but also a very secure and rigid connection between the fluid and air ducts 23 and 24.

Before the air ducts 24 are secured and bonded to the duct 23, a number of longitudinally spaced apart radially flushing bores 27 are provided in the liquid duct 23 for receiving a plurality of fluid nozzles 28. As shown in FIG. 7, the liquid nozzles are provided with a flange 29 which is seen from the side in the same shape as the wall of the liquid channel 23. The flange 29 has an outer wall surface 30 which corresponds to the shape of the bore 27 in the wall of the liquid channel 23.

The liquid nozzles 28 are also attached to the liquid channels 23 and are preferably connected thereto by resin, as discussed above by the epoxy bond 26.

After the liquid nozzles 28 have been mounted on the liquid duct 23 and the duct 24 has been fixed to the outer wall surface of the liquid duct 23, a plurality of bores 31 are formed in the air duct 24, flush with and concentric with the bores 27 in the liquid duct 23 and the nozzles 28 mounted thereon .

A liquid-air nozzle 12 is then mounted on and attached to the air duct 24 at each of the bores 31. In the preferred embodiment, a resin is again used to attach the liquid-air nozzles 12 to the air duct 24.

In an alternative embodiment, the liquid-air nozzles may instead be provided with end flanges 32 as shown in FIG. 6. The individual flange 32 and its abutment against the inner wall of the air duct 24 form a stronger connection because the resin binder can cover the entire front wall surface 33 of the flange 32 instead of a narrow part of the outer periphery of the nozzle 12. Liquid must be used. -the air nozzles are attached to the air ducts 24 before the duct is attached to the liquid duct 23, since the outer dimensions of the flange 32 are larger than the diameters of the bores 31.

After the entire module including the liquid duct 23, the air duct 24, the number of liquid nozzles 28 and liquid-air nozzles 12 are assembled to form a unit structure, this entire structure is covered with a layer of fiberglass filaments 34. This outer layer of fiberglass 8 connects and retains total and complete air duct 24 with the liquid duct 23 such that the strength and stiffness of the entire module 11 is at least as great as it would be if the entire member was molded as a single piece.

In addition to the prior advantages of the multi-nozzle aeration module 11 over previously known individual nozzle aerators, other advantages will be obtained which will be discussed below.

Eg. the module 11 is approx. 6 times as strong as it would be if made of steel of similar weight. In addition, the material used is substantially more corrosion resistant than the materials used previously and has substantially greater thermal resistance than if it were made of e.g. a thermoplastic material. It is much more erosion resistant than if it was made of thermoplastic material, as well as it is much stiffer than a similar module made of thermoplastic material.

Furthermore, the module 11 is extremely light compared to aerators in other materials, which increases the possibility of maintaining and reinserting the module. It may be desirable from time to time to raise the module above the fluid level for inspection. P.g.a. In the fiberglass structure, the module 11 can be lifted by a winch or cable which can be connected to the flanges 13 and the end caps 14 by means of bores 36, fig. 5. In addition, the module 11 can be quite long, ie. 6 m or more without being exposed to deflection or backlog.

The method described provides maximum flexibility, in that the module 11 can not only be manufactured to any desired length, but can also be mounted with any number of liquid nozzles 28 and liquid-air nozzles 12. Accordingly, the same cross-sectional design of the module 11 can be used for widely different wastewater capacities.

The flexibility built into the fabrication and the use of multi-nozzle aerators 11 can also result in optimization of the liquid pump and air compressor pumping and air through the liquid and

Claims (7)

In older known aeration systems, it is not uncommon to find that the pump and air compressors are not selected to have the most effective aspect ratio because such selection would require a substantially increased number of nozzle aerators. P.g.a. The present invention has the number of liquid-air nozzles having little influence on the cost of installation, and as many as the space permits can be used. Under these circumstances, the liquid pumps and air compressors may be selected to provide an optimal aspect ratio, regardless of the number of aerator nozzles required to take full advantage of such aspect ratios. As noted above, the radius of the air duct 24 is generally 2/3 of the radius of the liquid duct 23 in the preferred embodiment. This ratio gives a tear drop shape as shown in FIG. 5 with particularly good aerodynamic properties. Eg. are the two modules 11 in the system, fig. 1, arranged to circulate the liquid in the tank 10 in a counterclockwise direction. The purpose of this circulation is to keep solid particles floating in the liquid. The droplet shape of module 11, fig. 5, the resistance of the liquid in the tank 10 decreases. In known plants, in which several groups of individual beam feeders are used, it has been necessary from time to time to increase the amount of liquid delivered from the beam feeders in order to keep the speed of the liquid at a level sufficient to prevent the settling of solid particles. The fluid resistance of the previously used groups of individual jet generators was much greater than that provided by the modules 11, and this reduced fluid resistance will ensure that no additional pumping energy is required to overcome the fluid resistance of the module 11. Patent claims. A multi-jet aeration module for supplying a liquid below the liquid level in an aeration tank comprising a plurality of jet nozzles spaced apart on a rectilinear arm, which nozzles are adapted to dispense liquid from a liquid supply line, prior to mixing the liquid from the nozzles. with gas supplied from 142571 a gas conduit characterized by a liquid duct (23) made of a tubular thin plate having a plurality of longitudinally distributed and peripherally arranged liquid nozzles (28) and a parallel connected air duct (24) made of a thin plate, which is mounted as an outer wall outside the liquid channel and forms a passage therebetween, the outer wall being provided with a number of liquid-air nozzles (12), the number of liquid-air nozzles (12) corresponding to the number of liquid nozzles (28). and wherein the air-liquid nozzles are arranged coaxially with the liquid nozzles to provide an integral module. Aeration module according to claim 1, characterized in that the liquid duct (23) and the air duct (24) are made of fiberglass. Aeration module according to claim 1 or 2, characterized in that the liquid jet nozzles (28) are made of fiberglass. Aeration module according to one or more of claims 1-3, characterized in that the liquid-air jet nozzles (12) are of fiberglass. Aeration module according to one or more of claims 1-4, characterized in that the radius of the air duct (24) is smaller than the radius of the liquid pipe (23), whereby the two ducts in combination take the form of a tear drop. Aeration module according to one or more of claims 1-5, characterized in that it comprises, in one formed structure of the aeration module (11) formed by the combination of the liquid duct (23) and the air duct (24) an outer layer (34). ) of wire-wound fiberglass. Process for the manufacture of an aeration device according to claim 1, characterized in that a thin-walled, longitudinal and constant cross-sectional liquid pipe is made of fiberglass, that several boreholes are provided in a longitudinal direction and at regular intervals in the surface of the liquid pipe. that a fiberglass nozzle is bonded and / or fixed to liquid