GB2338427A

GB2338427A - A venturi jet unit assembled from a series of parts

Info

Publication number: GB2338427A
Application number: GB9812976A
Authority: GB
Inventors: Nigel John Wake; Garry Richard White
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-06-17
Filing date: 1998-06-17
Publication date: 1999-12-22
Anticipated expiration: 2018-06-17
Also published as: GB9812976D0; GB2338427B; GB2338427A8

Abstract

The venturi jet for entraining air in a stream of water comprises a T junction 1 having a water inlet 2, an air inlet 5 and an aerated water outlet 6. Fitted within the water inlet 1 is a first reducing bush or socket 8 in which a second reducing socket 9 and a cylindrical jet 10 are secured. By passing water through the first and second reducing sockets which have a diminishing cross section its velocity is increased so that the stream issuing from the jet 10 can draw in air from inlet 5. The aerated water passes through a bush 14 and reducing socket 15 fitted in outlet 6 into a pipe 7 from where it can be directed by a pipe 16 into the bottom of a sewage treatment tank. The embodiment of Figure 2 shows a that a plurality of venturi jet units may be provided in a single assembly so that, for example, aerated water could be supplied to two treatment tanks.

Description

2338427 VENTURI UNIT This invention relates to a Venturi unit for use in a

system for aerating a streamofwater. More particularly, it concerns a Venturi jet unit for providing a stream of aerated water for use in a system for treating sewage, and more especially the treatment of aqueous fluids in such a system, and from which at least a portion of solid matter has been separated.

One form of plant for the treatment of sewage involves a series of compartments into which the sewage is passed, and portions of material from the sewage are passed in sequence from one compartment to the other for further treatment. Raw sewage is passed into a primary settlement tank, where solid matter accumulates at the bottom, leaving supernatant aqueous liquid containing dissolved or suspended matter. As additional flow is introduced into the primary settlement tank, a portion of the supernatant liquid is displaced and flows over a weir or through perforations into a receiving sump from which it is pumped into a second tank containing a submerged filter which is colonised by of aerobic microorganisms that purify the liquid. The liquids are aerated as they are pumped to the bottom of the bed, in order to provide the necessary oxygen for the microorganisms, as it passes upwards through the bed.

Depending upon the rate of inflow of raw sewage into the primary settlement tank, the liquids after passing upwards through the bed will either flow back into the above-mentioned receiving sump, or be displaced, as a consequence of the incoming flow, into a secondary settlement tank where any material that has been displaced from the filter bed, e.g. dead microorganisms, is settled, and water, which is at least partially purified, overflows for disposal, use, further treatment, etc.

1 In order to aerate the aqueous liquid which is passed to the bottom of the filter bed, it is known to use a Venturi jet unit. Water flowing through such a jet will entrain air from an air inlet, the resultant aerated water being passed through a downpipe to the bottom of the filter bed.

The jet unit itself has certain essential parts, i.e. intakes for air and water, an outlet for aerated water, and a nozzle providing a jet through which water passes under high velocity for entraining air from the air inlet. Commerciallyavailable units of this type are normally formed from a single block, e.g. by moulding or machining, the construction being expensive. Moreover, efficient operation of a Venturi jet unit is dependent upon the correct combination of certain factors, including the initial water pressure, the velocity and volume of water passing through the nozzle, and the length of the downpipe for supplying aerated water to the bottom of the filter bed.

There is consequently a need for a jet unit of simple manufacture, which can be manufactured to allow easy adjustment before installation to meet the requirements of a particular sewage system, pumps, etc.

One embodiment of this invention provides a Venturi jet unit for entraining air in a stream of running water which comprises a junction member having a first inlet for water, leading through a region of diminishing cross section and terminating in a jet, an outlet for water from said jet, said outlet having a larger diameter than said jet, and a second inlet for air, communicating with the interior of said junction member upstream of said outlet whereby, in operation, air can contact water issuing from said jet, wherein the jet is a cylindrical tube fitting tightly within at least one reducing bush, fitting tightly within the junction member to provide said region of diminishing cross section.

2 A second embodiment of this invention provides a multiple Venturi jet unit for entraining air in a stream of running water which comprises a first T-junction member, having an inlet and a pair of opposed outlets, with a water supply pipe providing a tight fit with the inlet, each outlet communicating with a respective jet through at least one respective reducing bush each fitting tightly within a first intake of a respective second T-junction member said jets being substantially coaxial with said first intakes and respective outlets, each of said second T- junction members having a second intake, for air-supply to water issuing from a respective jet, each of said second intakes communicating with a first end of a respective bend unit by means of tightly fitting connecting members, each bend unit having a second end, said second ends being directed towards one another and being coaxial with respective outlets of a third T-junction member and communicating with said outlets by a respective tightly fitting intermediate member, said third T- junction member having an intake intermediate of said outlets and communicating with a tightly fitting air supply pipe lying substantially parallel to said water supply pipe.

The invention will be further described by reference to the accompanying Drawings, in which:

Figure 1 represents a section through one embodiment of a jet unit according to the invention, and Figure 2 represents a section through another embodiment of the invention.

As shown in Fig 1, the unit comprises a T-piece [11 having a first inlet [21 for water [31 provided by a pump as described above. A second inlet [41 is provided for air [51, and an outlet [61 is provided for aerated water passing out 3 of the unit. The outlet [61 communicates with a downpipe [7] for conducting the aerated water to the bottom of a filter bed.

Water supplied to the first inlet [21 by means of a pump as described above is passed downwards through a first reducing socket [81 and a second reducing socket [91 to a jet [101 which is preferably in the form of a hollow cylinder. By passing the water through the reducing sockets, the cross section of the stream is reduced and its velocity consequently increased, so that the stream of water, issuing f rom the jet [101 at a higher velocity than the initial input of water [31, draws in air [51. The air [51 passes into the second inlet [41 through an elbow-member [111 engaging the inlet [41 through a bush [121 and connecting pipe [131.

The aerated stream of waterfromjet [101 passes downwards into the pipe [71, which engages the outlet [61 through a tightly-fitting bush [141 and reducing socket [151.

The downpipe [71 is of length sufficient to reach the bottom of the filter bed and engages a pipe [161, through a bend unit [171, which provides a tight fit with the downpipe [71 and pipe [161. The function of pipe [161 is to concentrate and direct the flow of aerated water under the bed.

A further embodiment of the invention is shown in Fig 2 of the accompanying Drawings. This provides a unit by means of which aerated water can be directed in opposing directions. In this embodiment, water for aeration is directed downwards through pipe [241, running substantially parallel to an air supply pipe [381, lying in front of the water supply pipe [241, as viewed in Fig 2 of the Drawings. The lower end of the water supply pipe [241 terminates in a first T-junction member [21], the end of pipe [241 being a tight fit in the 4 inlet [221. The T-junction member [211 has a pair of outlets [23, 2Y1 leading to respective jets [25, 25'] by means of respective reducing bushes [26, 26T Optionally, further bushes [43, 4Xl may be provided between the reducing bushes [26, 261 and jets [25, 259. The reducing bushes [26, 26,1 are a tight fit in respective intakes [28, 28'] of second T-junction members [27, 27'], with connecting pipes [42, 42') being a tight fit with the interiors of the outlets of the first T- junction member [21] and the interior of the reducing bushes [26, 26']. Coaxial with the jets [25, 25'] are outlets [29, 29,1 for aerated water. These communicate with outlet pipes [39, 39'] by means of reducing bushes [41, 41'] and optional bushes [40, 40'].

Air is supplied to the second intake [30, 301 of the respective Tjunction members from pipe [381. This fits tightly within the inlet [371 of a third Tjunction member [351 which, in the view shown in Fig 2, lies in front of the water supply pipe [241. The third T-junction member [35] has a pair of oppositely-directed outlets [34, 34']. Intermediate members [36, 36,1 fit tightly within these outlets and also into the ends of respective bend units [31, 311 communicating respectively with the second inlets of the second Tjunction members [27, 27']. A tight positive fit is provided by respective pipes [32, 32'] fitting in the lower end of the bend units [31, 3VI. A tight fit between the pipe [32, 32'] and the respective inlets [30, 30'] is provided by bushes [33, 331.

It is generally preferred that the individual elements that are assembled to form the Venturi jet units according to the invention are formed from a durable plastics material such as UPVC. Other materials may be employed if desired. It is convenient to ensure a firm and positive connection between the members by means of solvent welding, but other means, such as grub screws can be employed, alternatively or in addition.

For use, the Venturi unit according to this embodiment of the invention is positioned in a gap between two substantially rectangular filter beds, with the respective outlets [39, 39'] being directed beneath these beds.

It will be seen that the Venturi units according to the invention are assembled from a series of relatively simple units, which can be made up in standard sizes. These units are the T-junction units, jets and pipes of appropriate cross section, with bushes and reducing bushes. Consequently, assembly of the Venturi jet units according to the invention is easy and the various sizes may be adjusted as desired in order to provide the most effective supply of water and entrainment of air within the water to provide the best effect. Venturi units can be adjusted, for instance, by increasing the length of the jets [10, 25, 25'], in order that they should have the most effective position with respect to the downpipe [71 or outlet [39, 39'] and also with respect to the air intakes. The rate of flow of water through the jets is determined by the hydrostatic bead, by the flow generated by the pump, and by the chosen diameter of the jets.

Within the limits implied above, the dimensions of the various elements in the units according to the invention may be selected as desired. Piping is manufactured commercially in a number of standard sizes, and it is convenient for the dimensions of the various elements to be so chosen as to make use of such readily available material. For instance, a standard reducing socket is available, having an external diameter of 50mm and an internal diameter of 40mm, reducing to an outlet end having an internal diameter of 20mm. Other sizes may be chosen, however, as appropriate.

6 1 Manufacture of Venturi units from a series of elements as described above provides a straightforward and cost-effective method of assembling Venturi jet units, avoiding the need for machining and moulding parts.

7 1

Claims

1. A Venturi jet unit for entraining air in a stream of running water which comprises a junction member [11 having a first inlet [21 for water, leading through a region of diminishing cross section and terminating in a jet [101, an outlet [61 for water from saidjet [101, said outlet having a larger diameter than said jet, and a second inlet [41 for air, communicating with the interior of said junction member [11 upstream of said outlet whereby, in operation, air can contact water issuing from said jet, wherein the jet [101 is a cylindrical tube fitting tightly within at least one reducing bush [8, 91, fitting tightly within the junction member [11 to provide said region of diminishing cross section.

2. A Venturi jet unit as claimed in Claim 1 wherein the outlet [61 from the junction member [11 is connected to a downpipe [71 through a reducing bush [151.

3. A Venturi jet unit as claimed in Claim 2 wherein the downpipe [71 communicates by way of a bend unit [171 with outlet [161, said downpipe [71 and outlet [161 fitting tightly at respective ends of said bend unit [161.

4. A Venturi jet unit as claimed in any one of Claims 1 to 3 wherein the second inlet [41 communicates with an upwardly-directed elbow unit [111 for the supply of air, connection between said inlet [41 and elbow unit [111 being established by tightly fitting members [12, 131.

5. A multiple Venturi jet unit for entraining air in a stream of running water which comprises a first T-junction member [211, having an inlet [221 and a pair of opposed outlets [23, 23'], with a water supply pipe [241 providing a tight fit with the inlet [221, each outlet [23, 231 communicating with a respective jet [25, 25'] through at least one respective reducing bush [26, 26'], each 8 fitting tightly within a first intake [28, 28'] of a respective second T- junction member [27, 2TI, said jets [25, 2WI being substantially coaxial with said first intakes [28, 281 and respective outlets [29, 29'], each of said second Tjunction members [27, 271 having a second intake [30, 3TI, for air-supply to water issuing from a respective jet [25, 25% each of said second intakes [30, 301 communicating with a first end of a respective bend unit [31, 31,1 by means of tightly fitting connecting members [32, 33, 32', 33'], each bend unit having a second end, said second ends being directed towards one another and being coaxial with respective outlets [34, 34'] of a third T-junction member [351 and communicating with said outlets by a respective tightly fitting intermediate member [36, W], said third T-junction member having an intake [371 intermediate of said outlets [34, 341 and communicating with a tightly fitting air supply pipe [381 lying substantially parallel to said water supply pipe [241.

6. A multiple Venturi jet unit as claimed in Claim 5 wherein said outlets [29, 291 of said second T-junction members [27, 2T1 communicate with respective outlet pipes [39, 39'] through respective tightly-fitting intermediate members.

7. A Venturi jet unit substantially as hereinbef ore described with ref erence to either Figure of the accompanying Drawings.

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