Moreover the enhanced apparent volumetric compression ratio of the boundary zone discussed above, may be provided by forming the upper gas discharge surface of the element above the boundary zone with a downward and outward slope at an angle of depression in the range of about 10 to about 80 relative to the horizontal. Boon, completed September 15, , in fulfillment of a grant from the Association of Metropolitan Sewerage Agencies and the British Water Research Centre under the partial sponsorship of the U. Thus an increase or decrease in flow rate through a passage respectively increases or decreases the total pressure loss. Also, it is apparent that a general or special purpose computer may be provided and programmed to make the necessary conversions of data, and, if desired, actuate process control devices. Another technique that has been found to produce benefits similar to those which result from postponement of dynamic wet pressure reduction is the application of surface active agent s in either liquid or gaseous form during the cleaning period to the interface between the diffusion elements and the liquid medium. One may choose a diffusion element having any one or all of the above preferred characteristics. For example water vapour may enter the system and become mixed with the cleaning gas because the water vapour is a normal or usual component of certain kinds of treating gas e. In particular there will be a need to convert said observed conditions of dynamic wet pressure to a basis comparable with the 2 SCFM per square foot rate employed in establishing the dynamic wet pressure ranges.

A plurality of flow regulating means is distributed about a submerged portion of the network for receiving the aforementioned gases and for discharging them at predetermined flow rates. A measure of success was obtained in that there was reduction of flow resistance and apparently some prolongation of the life of the elements. Suitable provision not shown should be made for expansion and contraction where necessary. Date of ref document: Through experience it should also be possible to determine the time interval during which cleaning gas should be applied at a given flow rate in order to adequately restrain foulant deposition. What I like best is its exceptional attack with active pickups. Also, preferably, the element is one whose sides, including for example extreme vertical edges and vertical or near vertical surfaces of steps near the periphery of the element, are porous, at least semi-permeable and free of adherent material preventing bubble emission. According to this theory, as the active or most active pores begin to clog through deposits of foulants, flow is reduced.

Withdrawal of ram permits one to remove the resultant compacts from die cavity For this reason, the combination of a side of reduced permeability and a sealing means at the above described edge represent a preferred embodiment of the present invention.

This facilitates the use of metallic conduits in the non-submerged portions of the network, including for example those conduits, such as downcomer pipes, which convey the treating gas from a position above the surface of the liquid medium down into the liquid medium.

In Figure 11, annular horizontal shelf 27 includes an inner upstanding lip 27A which helps retain in place a sealing means of substantially rectangular cross section, upon which rests the marginal edge of the lower surface of diffusion element 35D. Figure 2 shows in perspective a broken out and enlarged portion of one of the air headers 11 with its diffusers The remainder of the side of element 35G is a lower cylindrical surface which need not necessarily have any impermeable coating thereon.

An air supply A, which can be a separate compressor or a tap into the plant aeration air system is used to supply a slow rate of air through a bubble pipe B, having its lower, open end located at the same elevation as the discharge surface of the diffuser elements.

If the system pressure again increases, additional less active pores, characterized by an even higher pressure loss, will then become active. Other portions of the network may be formed of other materials, including for example metallic conduits and fittings. These larger and smaller percentages of thickness reduction can be effected by performing the pressing in a press having a ram and die cavity, with spaced, opposed compression faces having respectively smaller and larger clearances in central and surrounding portions of the space between the faces, whether the smaller clearances are provided by a protuberance on the compression face of the die cavity or by other means.


As shown in Figures 3 through 5, side wall means 26 is connected with the periphery of lower wall means The most preferred diffusion element is a ceramic plate of circular outline having a stepped edge, depicted in Figures 3 and 4, and includes circular central flat area 70, annular bevelled edge 71, annular flat surface 72, outer annular bevelled surface 73 and horizontal annular surface 74, whose respective outer diameters are 4.

Figure 12, like Figure 7, is an example of a sealing means located at the edge between a side surface and an upwardly facing upper surface of the diffusion element. Notwithstanding the apparent success of in place gas cleaning of tubing-type diffusers and the long-standing knowledge of and early attempts at in place gas cleaning of the multi-pore area release diffusion elements customarily employed in the tank-type aeration facilities generally used by large cities and counties, gas cleaning in place has not been generally adopted for such facilities.

LAG – Achat Lag / Avis Lag / Comparatif Lag – EasyZic

Put differently, cleaning may be commenced when something less than all of the elements in a given group have reached the predetermined extent of fouling at which cleaning is seriew be commenced. Diffusion element supporting means, spaced upwardly and outwardly from the lower wall means, are provided on said side wall means.

A compressor 5 is provided to feed filtered atmospheric air through valve 6A, flow indicator 7A, and branch conduit 18A to air main 8. The values given are for bubble release pressure in water of new nasse as manufactured, i.

It is also preferred to fabricate the element of jaccobacci materials, i. If foulant deposits form at a location in the diffusion element which is not readily supplied with water by the liquid medium or treating gas, it can be beneficial to supply water vapour in admixture with -the cleaning gas for forming aggressive aqueous solutions that assist in cleaning.

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Such a method of operation holds promise of considerably lengthening the useful lives of diffusion elements. It is preferred however to apply the cleaning gas intermittently and to seriex the application of cleaning gas at or before the time when jacobacci has progressed to a predetermined extent.

However, attachment of the diffuser elements by central or other fasteners which extend through holes in the active diffusion surface produce detrimental effects, the prediction of which would not have been obvious. The property of reduced permeability relative to the upwardly facing gas discharge surfaces including substantial non-permeabilityis beneficial when combined with the sealing means at the above described edge.

The two embodiments show the sealing means below. Thus, according to this preferred alternative, the height of wall 28 jscobacci be equal to or slightly greater or less than the height of the diffusion element.

But Jackson was only one of a number of individuals who experimented with in place cleaning with gaseous cleaning agents in a variety of plants. Redmon, entitled “Diffusion Element”, filed in the U.

EP0049154A1 – In place gas cleaning of diffusion elements – Google Patents

The frictional resistance component of pressure loss varies inversely with pore diameter. In order for a gas to flow through a gas discharge passage of a diffusion element and bubble into a liquid medium, there must ‘be a relatively higher pressure in the gas at the influent end of the passage as compared to the pressure in the liquid at the effluent end of the passage. Accordingly various iacobacci were made to develop satisfactory processes for cleaning the aeration devices in place, i.

The flow regulating means are sized or adjusted to deliver cleaning gas alone or in admixture with treating gas at a substantially similar rate to each of a plurality of plenums, each of the plenums being connected directly or indirectly with one or more diffusion elements whereby the hasse or more diffusion elements connected with each plenum can be supplied with gas at a substantially similar rate as compared to the diffusion elements connected to the other plenums.

I can play all and any style, said to slap it sounds great! The side or periphery of element 35D is in opposed, facing relationship with generally upstanding wall means 28 across a narrow vertical space or crevice According to a preferred embodiment a combined bonded assembly is formed by the pipe, by lower wall means 15 and by the air flow regulator member or a sleeve member 25 in which the air flow regulator member is mounted. On the other hand, the invention can be embodied in an even wider variety of forms than can be specifically discussed and illustrated herein.


Regulating valve is adjusted against a relatively high pressure from compressor C to a relatively low rate of flow, i. Country of ref document: A particularly desirable characteristic of the preferred diffusion elements is that of relative uniformity of bubble release pressure throughout the gas effluent surfaces of the elements. Boon, completed September 15,in fulfillment of a grant from the Association of Metropolitan Sewerage Agencies and the British Water Research Centre under the partial sponsorship of the U.

Alternatively, a portion of the diffusion element which would otherwise discharge air into a crevice of the type described above can be sealed by appropriately positioning a seal of lesser height than the element, by applying an impermeable coating to the surface, or by sufficiently compressing such sides or any portion thereof having access to water so as to render same substantially impermeable. Operating at diminished hydrostatic head includes reducing the submergence of the diffusion elements during at least a portion of the time during which cleaning is being conducted.

As shown in greater detail in Figure 20A, the vertical leg of tee and the sealing ring constitute a test probe. The magnitude of the surface tension component of the pressure loss varies inversely with the effective hydraulic radius of the passage at the location where bubbles are formed. Estimated flows based on bubble release pressure may be derived for the edges of the element.

In certain cases the majority of the wall areas in the plenums may be defined by the influent surfaces of the diffusion elements, such as where the elements are in the form of elongated tubes of relatively small diameter compared to their length. Alternatively, where the normal plant procedure is to conduct cleaning intermittently during one or more extended cycles of operation, there may be continuous cleaning from time to time, for example when seasonal or other factors cause the concentration of foulants in the liquid medium or treating gas to increase to an unusually high level.

The exemplary apparatus includes a tank Figure 20 having bottom wall and side walls O-ring seal 80 is compressed against four surfaces, including diffusion element surfaces andhorizontal annular shelf 27 and the inner surface of wall means By manipulation of valves 6A and 6B one may commence, terminate or control the flow of aerating and cleaning gas whereby the foregoing elements constitute means for feeding aeration gas and for continuously or intermittently feeding a mixture of aeration gas and cleaning gas to the distribution network.

It is of interest to note that sewage treatment plant designers are generally familiar with the tubing-type diffusers for the sewage treatment ponds or lagoons used by small communities. Increases and decreases in the aforementioned pressures may be detected by measurement of changes in the pressure in the conduits of the distribution network between the compressors. In one such embodiment, conduit 18B enters but does not communicate with air main 8 at the point of intersection shown in Figure 1 and extends continuously within air main 8 and downcomer 9 to a discharge outlet in pipe 10 downstream of the coupling and below the surface of the liquid in the tank.

The distribution network comprises air main 8 which is generally supported above the level of liquid in the tank 1, and which feeds into a downcomer pipe 9, extending vertically from air main 8 to a horizontally disposed distributor pipe 10 supported substantially horizontally a short distance above bottom 2.

More particularly the invention relates to the cleaning of multi-pore diffusion elements while submerged in liquid media including such foulants.