WO2005077840A1

WO2005077840A1 - Mechanical aeration apparatus for treatment of sewage

Info

Publication number: WO2005077840A1
Application number: PCT/CZ2005/000017
Authority: WO
Inventors: Zdenek Sosna
Original assignee: Sbh Water Spol S Ro
Current assignee: Sbh Water Spol S Ro
Priority date: 2004-02-12
Filing date: 2005-02-11
Publication date: 2005-08-25
Anticipated expiration: 2006-08-12
Also published as: CZ2004230A3; CZ295006B6

Abstract

A mechanical aeration gear for treatment of sewage, made of a hollow centre shaft (1) to which are fastened wings (2.1, 2.2) in the shape of a half of a cylindrical surface. Every of the two wings (2.1, 2.2) is fastened on the centre shaft (1) on the opposite side of its diameter. A free end edge of every wing (2.1, 2.2) is at a distance of one half of the centre shaft (1) diameter from its surface. A stirring blades (3.1, 3.2) are fastened on the centre shaft (1) under the wings (2.1, 2.2). There are supporting ribs (4) in the shape of a capital letter << L >> between the free end of every wing (2.1, 2.2) and the centre shaft (1). A free end of the longer part of every rib (4) is fixed on the centre saft (1). A free end of every wing (2.1, 2.2) bears on and is fixed in the corner between a shorter and longer part of every supporting rib (4). The shorter part of every supporting rib (4) exceeds the free end wing (2.1, 2.2) which is fastened on the opposite part of the centre shaft diameter (1).

Description

MECHANICAL AERATION APPARATUS FOR TREATMENT OF SEWAGE Field of the invention The invention concerns a mechanical aeration gear for treatment of sewage producing fine air bubbles.

Description of prior art The mechanical aeration gear for treatment of sewage is dealt in the CZ Pat. 276137 called Deep chamber aerator. The gear consists of a centric cylindrical tube which are three sides connected to. The sides are arched or fully cylindrically bent against the rotation direction. The centric cylindrical tube is connected to a shaft which is joined through Hooke^'s universal joint to a driving motor. There is made a float space in the upper part of the cylindrical tube. This alleviates the gear, the most part of which is placed under water surface in an aeration tank containing the sewage determined for treatment. There are vertical flat hindrances in the aeration tank and they prevent the liquid rotation in the tank. When the motor makes the gear rotate, the water at the surface tears off from the chamber front part and an occurred space is fulfilled by air. Sequentially also the bottom water levels tear off from the chamber front part. Water starts to get into all chambers from the bottom, this water is mixed with air and the mixture falls off the gear centre and rises up. The water in the tank is oxidized like that and goes up to the surface. In this arrangement air bubbles are made in the diameter of approx. 10 mm, which is termed to be middle size bubbles. A disadvantage of this arrangement is that the air bubbles of a middle size goes up to the surface quite quickly. The consequence is an insufficient aeration of the tank. The bacteria in the sewage do not have enough time to use completely oxygen content in the bubble. To increase a treatment effect of this gear it is necessary to use a more high-performance engine with a higher energy consumption. The vertical hindrances negatively influencing the rotation movement in the tank are also, in some measure, disadvantageous. In case an air bubble during the rotation and rising movement in the tank hits a vertical flat hindrance, it rises along it perpendicularly to the surface. The oxygen in this bubble is used by bacteria only slightly. An disadvantage of this arrangement is small efficiency of air delivery to the tank, an insufficient stirring and a minimal treatment ability of this gear. Summary of the invention

The above mentioned defects are to some measure eliminated by a mechanical aeration gear for treatment of sewage, made of a hollow centre shaft to which are fastened wings in the shape of a half of a cylindrical surface. The invention centre lies in the fact that every of the two wings is fastened on the centre shaft on the opposite side of its diameter. A free end of every wing is at a distance of one half of the centre shaft diameter from its surface. There are fastened stirring blades on the centre shaft under the wings. There are supporting ribs in the shape of a capital letter „L" between the free end part of every wing and the centre shaft. A free end of the longer vertical part of every rib is fixed on the centre shaft. A free end of every wing bears on and is fixed in the corner between a horizontal and vertical part of every supporting rib. The shorter horizontal part of a supporting rib exceeds the outside free end wing surface which is fastened on the opposite part of the centre shaft diameter. A front part of the shorter rib part which exceeds the outside wing surface is pointed. The stirring blades and the horizontal surface form an angle α which is from 20° to 30°. The stirring blades are in the shape of flat plates. The distance between outside end edges of the stirring blades is bigger than is the biggest distance between outside surfaces of free end parts of both wings. The advantage of the arrangement according to the invention is that during rotation there is created a space, between the centre shaft and both wings, and atmospheric air is sucked into this space. Due to an intensive turbulence very fine air bubbles are created in this space. They goes up to the surface quite slowly. Bacteria have enough time to absorb oxygen. The front edges of the horizontal shorter rib parts, which exceed the free wing edges, cut fibre sludge and thus decrease a sludge index. This causes lower costs of a redundant sludge removal. Two stirring blades at a rotor end ensure efficient hydraulic movement in the tank. This gear shows decreased operating and investment costs in the comparison of the gears producing large and middle size bubbles. When reducing operation revs of one fifth, the fine air bubbles creation is stopped and water in an aeration tank is only being stirred. Consequently, an aerobe way of treatment finishes and begins an anaerobe way of treatment when nitrides and phosphates are degraded from sewage. Brief description of the drawings

Fig. 1 - shows a gear with a centre shaft, with two arched wings, with two stirring blades a supporting ribs in an axonometric view; Fig. 2 - shows the same gear in a front view; Fig. 3 - shows a profile the plane of which runs under a flange; Fig. 4 - shows stirring blades in a bottom view; Fig. 5 - shows one part of the gear with the first stirring blade in a side-view.

Detailed description of embodiments of the invention

A centre shaft is a cylindrical tube. On the centre shaft are fastened two bent wings l, 22. Every wing 2 _, 22 has in a cross section the shape of one half of a thin-walled cylindrical tube cut in the plain going through its longitudinal axis. The diameter of both wings 2J_, Z2 is the same and equals to the double of centre shaft diameter. The joining of each wing 2 _, 22 with the centre shaft 1 is made on the opposite parts of its diameter by for example welding along the whole length of the adjacent part of every wing 2Λ_, 22. Thus the inner part of every wing 2 _., 22 gradually recedes from the outside centre shaft 1 surface. A free end of every wing 2.1 , 2.2 is on the opposite diameter part. The distance of the free end of every wing 2.1 , 2.2 from the centre shaft 1 surface equals to one half of the centre shaft diameter. The length of every wing 2 _, 22 in a vertical direction corresponds to approx. Two thirds of the centre shaft 1 height. Between the free end of every wing 2.1 , 2.2 and the centre shaft 1_there are placed supporting ribs 4. All supporting ribs 4 are the same. They are in the shape of a capital letter "L". A free end of a longer vertical supporting rib 4 part is fixed on the shaft 1 A free end of every wing 2Λ_, 22 bears on the corner between a horizontal and vertical part of every supporting rib 4 and is fixed there. A shorter horizontal part of a supporting rib 4 exceeds the outside surface of that wing Zl, 22 which is fastened on the opposite diameter part of the centre shaft 1 . A front part of the shorter supporting rib 4 part exceeding the outside wing 2 _., 22 surface is pointed. The number of supporting ribs 4 at every wing 2.1 , 2.2 depends on its length. In this version example (Fig. 1 and Fig. 2) there are 7 supporting ribs 4_. Their number can be according to the wing 2Λ_, 22 length bigger or smaller. Under the wings 2Λ_, 22 there are fixed two stirring blades 3 [, 3J2 on the centre shaft 1_and these form an angle g, which is from 20° to 30°, with a horizontal plain. The stirring blades 3J., 32 are in the shape of flat plates. The distance between outside end edges of the stirring blades 3J_., 3,2 is bigger than the distance between outside surfaces of the free end parts of both wings Zl, ZZ On the upper end there is a flange 5 for a right connection or for a connection through other gears to the driving motor. There are not drawn a driving motor or any other attachments in the drawings. The most gear part, which has wings Zl, Z2, is dipped into the aeration tank with sewage meant for treatment. The max surface level of sewage is mark by a triangle (Fig. 2). During the whole gear rotation at operating revs of the electromotor also rotate the centre shaft 1, both wings Zl, Z2, all supporting ribs 7 and both stirring blades 3 _, 3_^2. The water in the aeration tank flows around both wings Zl, 2.2, and their outside surface areas from the smallest diameter which corresponds to the centre shaft 1 diameter to their biggest diameter. Due to rotation and centrifugal force the water level gradually falls in the space between the centre shaft and inner part of the wings Zl, ZZ Atmospheric air is being sucked under pressure to this space. The air flow in this space moves downwards to the stirring blades 3J_., 32 and to the tank bottom. The supporting ribs 4 and both stirring blades 3.1 , 3.2 well influence the air flow mixing during which very fine air bubbles are made. The smaller part of these air bubbles gradually bubble through to the water surface. Most of the fine air bubble flow continue towards the stirring blades 3 _., 32. Stirring blades 3J_, 3.2 rotation contributes to intensive turbulence of the air flow towards the down levels of the aeration tank and to the aeration tank bottom and to the very fine air bubbles creation. At the same time stirring blades 3 _, 3_^2 put the water and bacteria mixture in the aeration tank into rotation hydraulic movement. By this movement the way of the fine air bubbles to the water surface is prolonged. During this way bacteria have longer time for oxygen detraction and its absorption from air bubbles and for sewage treatment. At operating revs an aerobe sewage treatment is being made. The front pointed walls of the shorter rib 4_ parts exceeding outside surface of the wings 2.1 , 2.2 cut fibre sludge. Thus they decrease sludge density and sludge index. If the sludge density is decreased by this cutting, then the time between every redundant dense sludge removal is prolonged and its removal costs are decreased. When the operation revs are reduced by approx. 20 %, the influence of rotation and centrifugal force is substantially reduced too. Air suck and the creation of air bubbles in the space between the centre shaft 1_and the inner parts of the wings 2.1 , 2.2 is stopped. This space is filled by water. The stirring blades 3 _, 32 put the water and bacteria mixture in the aeration tank to calm rotation movement. The water in the aeration tank is not oxidized, it is only being stirred. Denitrification proceeds in the aeration tank during this process. Nitrides and phosphates are degraded..

Industrial applicability

The invention will be used to aeration and stirring of aeration tanks in biological sewage water treatment plants and to sludge regeneration in tanks and ponds.

Claims

1. A mechanical aeration gear for treatment of sewage, made of a hollow centre shaft (1) to which are fastened wings (2.1, 2.2) in the shape of a half of a cylindrical surface, characterized in that every of the two wings (2.1, 2.2) is fastened on the centre shaft (1) on the opposite side of its diameter and a free end edge of every wing (2.1, 2.2) is at a distance of one half of the centre shaft (1) diameter from its surface and there are fastened stirring blades (3.1, 3.2) on the centre shaft (1) under the wings (2.1, 2.2).

2. A mechanical aeration gear according to claim 1 characterized in t h a t there are supporting ribs (4) in the shape of a capital letter „L" between the free end of every wing (2.1, 2.2) and the centre shaft (1), a free end of the longer part of every rib (4) is fixed on the centre shaft (1), a free end of every wing (2.1, 2.2) bears on and is fixed in the corner between a shorter and longer part of every supporting rib (4), while the shorter part of every supporting rib (4) exceeds the free end wing (2.1, 2.2) which is fastened on the opposite part of the centre shaft diameter (1).

3. A mechanical aeration gear according to claim 1 characterized in that a front part of the shorter rib (4) part which exceeds the outside wing (2.1, 2.2) surface is pointed.

4. A mechanical aeration gear according to claim 1 characterized in that the stirring blades (3.1, 3.2) and the horizontal surface form an angle g which is from 20 ° to 30 °.

5. A mechanical aeration gear according to claim 1 characterized in that the stirring blades are in the shape of flat plates.

6. A mechanical aeration gear according to claim 1 characterized in th at the distance between outside end edges of the stirring blades (3.1, 3.2) is bigger than is the biggest distance between outside surfaces of free end parts of both wings (2.1 , 2.2).