Liquid purification or separation – Flow – fluid pressure or material level – responsive – Maintaining stream pressure or flow
Reexamination Certificate
1994-07-11
2001-03-13
Barry, Chester T. (Department: 1724)
Liquid purification or separation
Flow, fluid pressure or material level, responsive
Maintaining stream pressure or flow
C210S205000, C210S221200, C210S199000, C134S170000, C134S171000
Reexamination Certificate
active
06200468
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the treatment of liquid media containing organic and/or inorganic foulants. More particularly the invention relates to the cleaning of multipore diffusion elements while submerged in liquid media including such foulants.
BACKGROUND OF THE INVENTION
The aeration of waste liquid media, including for example domestic sewage and industrial waste waters, is an old art. The activated sludge process, which includes aeration of liquors containing domestic sewage, has been in continuous use for about sixty years.
The liquid media treated in such aeration processes very commonly contain organic and/or inorganic foulants such as for example relatively insoluble salts which are responsible for the hardness of the water, and living and non-living organic residues which contribute to the formation of scales and slimes. Upon aeration of these media with submerged aeration devices, there is a tendency for the foulants to progressively foul such devices at the point of release of oxygen-containing gas into the liquid media, closing up or otherwise modifying the openings through which the oxygen-containing gas is released into the media with various undesirable results.
Such fouling can impair the uniformity of gas distribution from aeration devices, especially when such devices are of the area discharge type, such as for example the flat porous ceramic plates which were used to discharge air into sewage liquors in early activated sludge plants. Also, fouling can in certain circumstances increase the pressure differential required to drive oxygen-containing gas through the aeration devices at a given flow rate, thus either reducing the flow of oxygen available, and therefore the oxygen transfer rate of the aeration system, and/or increasing the amount of power consumed in maintaining the desired rate of flow, thus substantially increasing the energy requirements and cost of the process.
Since these fouling phenomena are often progressive in nature they can eventually lead to a complete or near complete disablement of the aerating devices if permitted to continue long enough. Accordingly, it is a goal of the present invention to provide methods and apparatuses for effectively monitoring the status of the aeration devices while in operation, and particularly, the dynamic wet pressure of operating aeration devices.
SUMMARY OF INVENTION
The present invention includes several aspects of a liquid treatment apparatus. In one such aspect, the invention provides a liquid treatment apparatus comprising a gas distribution network in a tank and means for introducing treating gas into the network. The apparatus includes a source of cleaning agent; means including valve means for intermittently introducing into the network the cleaning agent alone or in admixture with the treating gas; a plurality of synthetic thermoplastic or thermoset resin plenums; a plurality of flow regulators distributed about a submerged portion of the network for receiving the aforementioned treating gas and cleaning agent and for discharging them into the plurality of plenums downstream of the flow regulators, a plurality comprising at least ten diffusion elements sealingly engaged and in communication with the plenums for receiving the treating gas and cleaning agent, the elements having air diffusion pores extending therethrough, but being free of through-holes other than air diffusion pores, each of the diffusion elements being in communication with its own individual flow regulator through its own individual plenum downstream of the flow regulator for tending to promote gas flow through the diffusion elements at similar rates, the pores defining paths for discharge of the treating gas and cleaning agent and which exhibit an increase in dynamic wet pressure and/or bubble release pressure as a result of deposition of foulants; retaining means engaging the diffusion elements about their peripheries for securing the elements to the plenums; sealing means adjacent the peripheries of the diffusion elements for preventing leakage of air from the plenums past the peripheries of the elements; and measuring devices for monitoring the operation of the liquid treatment apparatus by measuring changes in operating parameters of the apparatus that indicate dynamic wet pressure changes across the diffusion elements with sufficient precision for initiating the flow of cleaning agent with sufficient frequency for maintaining the dynamic wet pressure across the diffusion elements in a range not to exceed about 25 inches of water gauge above a base condition of the elements.
A further embodiment of the first aspect of the invention includes measuring devices comprises devices for measuring pressure across or flow of gas through one or more diffusion elements; devices for measuring said changes with sufficient precision to maintain the dynamic wet pressure across the diffusion elements in a range not to exceed about 15 inches of water gauge above said base condition; and devices for measuring the hydrostatic pressure of said liquid at about the elevation of the diffusion elements, devices for measuring gas pressure within a plenum downstream of a flow-regulating means, and devices for measuring the gas pressure within a header supplying gas to said flow regulating devices.
Still further embodiments of the first aspect of the invention include apparatuses wherein the diffusion elements are divided into at least two groups and including at least one measuring device, the device includes at least one flow measuring device capable of measuring the respective flow or flows of gas through at least one selected group among the at least two groups, and the apparatus includes at least one controlling device capable of controlling flow of cleaning agent to one or more of the selected groups; apparatuses wherein the at least one controlling device is capable of passing cleaning agent to one or more of the selected groups with a flow which differs from the flow of cleaning agent, if any, to one or more other groups among the at least two groups; apparatuses wherein said at least one measuring device includes at least one pressure measuring device capable of measuring the respective pressure or pressures of gas flowing through at least one selected group among said at least two groups, and the at least one controlling device is capable of controlling flow of cleaning agent to one or more of said selected groups in response to measurements made by said measuring device; and apparatuses wherein the sealing means, retaining means and plenums jointly restrain vertical movement of said diffusion elements.
In a second aspect, the invention provides a liquid treatment apparatus comprising a gas distribution network in a tank and means for introducing treating gas into the network. The apparatus includes a source of cleaning agent; means including valve means for intermittently introducing into the network the cleaning agent alone or in admixture with the treating gas; a plurality of synthetic thermoplastic or thermoset resin plenums; a plurality comprising at least hundreds of diffusion elements sealingly engaged and in communication with the plenums for receiving the treating gas and cleaning agent, the elements having air diffusion pores extending therethrough, but being free of through-holes other than air diffusion pores, the pores defining paths for discharge of the treating gas and cleaning agent and which exhibit an increase in dynamic wet pressure and/or bubble release pressure as a result of deposition of foulants; retaining means engaging the diffusion elements about their peripheries for securing the elements to the plenums; sealing means adjacent the peripheries of the diffusion elements for preventing leakage of air from the plenums past the peripheries of the elements; and measuring means for monitoring the operation of the liquid treatment apparatus by measuring changes in operating parameters of the apparatus that indicate dynamic wet pressure changes across the diffusion elements with sufficient
Ewing Lloyd
Redmon David T.
Schmit Frank L.
Barry Chester T.
Hall Priddy Myers & Vande Sande
Sanitaire Corporation
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