CA1055169A - Support medium for biological treatment - Google Patents
Support medium for biological treatmentInfo
- Publication number
- CA1055169A CA1055169A CA240,638A CA240638A CA1055169A CA 1055169 A CA1055169 A CA 1055169A CA 240638 A CA240638 A CA 240638A CA 1055169 A CA1055169 A CA 1055169A
- Authority
- CA
- Canada
- Prior art keywords
- mesh
- medium
- sheets
- support medium
- sewage
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
- C02F3/02—Aerobic processes
- C02F3/10—Packings; Fillings; Grids
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/10—Biological treatment of water, waste water, or sewage
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Biodiversity & Conservation Biology (AREA)
- Microbiology (AREA)
- Hydrology & Water Resources (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Biological Treatment Of Waste Water (AREA)
Abstract
Abstract of the Disclosure A support medium for the biological treatment of sewage or other effluent in a system of the trickle filter type, comprising a plurality of superposed layers of a mesh-like material, the meshes of any one of said layers being placed randomly with respect to the meshes of an adjacent layer.
The preferred medium is a foamed plastics material.
The preferred medium is a foamed plastics material.
Description
10551~9 This invention relates to a support medium for the biological treatment of sewage and other effluents.
Biological treatment or disposal of sewage and other organic effluents is normally performed by contacting the effluent with bacteria and other microorganisms which grow and consume the organic content of the ef1uent. Processes involving this basic principle vary widely in detail but broadly they include:
~i) Anaerobic digestion where the effluent is contained within a tank and the micro-organisms grow under anaerobic conditions by consuming organic matter at a relatively slow rate, but with a high rate of conversion to gaseous products, such as methane and carbon dioxide.
cii) Settling ponds where aerobic microbial action depends on rate of air transfer into a relatively shallow pond containing the effluent.
Ciii) Activated sludge systems where the effluent is contained in a tank or pond, to which air is supplied to carry out the digestion under aerobic conditions and which permit a greater rate of digestion than (i) or Cii). Effluent conversion is limited by the need to re-cycle some of the microbial sludge and liquor to provide continued generation of the micro- ~- -organisms.
Civ) Trickle filter systems where the active microorganisms grow on a -support medium, effluent and air being circulated over the bacterial growth to effect conversion of the effluent.
The present invention is concerned particularly, with the trickle filter type of system but also extends to systems of the activated sludge or extended aeration types.
Typically, trickle filter plants are composed of crushed rock ;:~
retained in a bed some 6 feet C2 metres) deep and up to 200 feet (60 metres) wide. Effluent is sprayed over the top of the bed and air is allowed to circulate through the bed from the top and open (or porous) base of the bed.
Microbial growth takes place on the surface of the rock. Such plants are -1- ~
. . .
.
1~551~;9 limited in size, usefulness, and efficiency, by land use requirements, weight of rock, air accessibility, susceptibility to flies, and other factors.
Recently plastic support media have replaced rock and stone in trickle filter systems, giving the advantages of lighter weight, higher surface to volume ratios, and greater open volume for better air penetration.
This has allowed the development of deeper, more efficient beds, and also tota immersion treatments where the support medium is fully immersed in the effluent and air or oxygen is pumped through the bed.
Such plastic support media are frequently constructed in the form of solid, i.e., imperforate, sheets having a variety of corrugated patterns.
Some examples are the materials known as *Flocor tICI Aust. Ltd.) and *Surfpac tnOw Co. Aust. Ltd.). Other types of support media include discs, rings, spoked wheels and other shapes designed to facilitate microbial growth, with maximum void space to provide for adequate air circulation.
According to the present invention there is provided a support medium for the biological treatment of sewage or other effluent, said medium comprising a plurality of superposed layers of a mesh-like material, the sheets being disposed so as to avoid superposition of the apertures of at least some adjacent sheets.
Simply by randomly laying one sheet on another, it has been found that superposition of the apertures of a satisfactory number of adjacent sheets is achieved. It should be appreciated, however, that this number can be increased and the efficiency of the medium improved by d~liberately arranging the sheets to avoid superposition of the apertures.
Thus, according to another aspect of the invention, there is a support medium when used for the biological treatment of sewage or other aqueous effluent, said medium comprising a plurality of superposed sheets of a mesh-like material, the sheets being disposed so as to avoid super-position of the apertures of adjacen~ sheets.
The preferred material for the mesh is a plastics material and it * trade marks ~, ~
1~551t;9 is specifically preferred to use a foamed plastics material. Some examples of suitable materials of this latter type already manufactured are those sold under the trade names "Trical" and "Netlon".
In the preferred arrangement of the medium, the sheets or layers correspond in shape and area to the cross-section of the tank or other vessel in which they are contained, i.e. each layer spans the full cross-section of the vessel. It is, however, within the scope of the invention to use layers which are of smaller area than the containing vessel.
Thus in another aspect of the invention there is provided apparatus, such as a trickle filter, for the treatment of sewage or other aqueous effluent the apparatus comprising a vessel which is at least partly filled with the support medium.
Table 1 compares the density of packing ~i.e., a 'bulk density'), calculated surface area per unit volume and void space of the total volume of the packing for typical prior art materials used in trickle filter applications, together with the same properties for support media in accord- - -ance with the present invention.
Biological treatment or disposal of sewage and other organic effluents is normally performed by contacting the effluent with bacteria and other microorganisms which grow and consume the organic content of the ef1uent. Processes involving this basic principle vary widely in detail but broadly they include:
~i) Anaerobic digestion where the effluent is contained within a tank and the micro-organisms grow under anaerobic conditions by consuming organic matter at a relatively slow rate, but with a high rate of conversion to gaseous products, such as methane and carbon dioxide.
cii) Settling ponds where aerobic microbial action depends on rate of air transfer into a relatively shallow pond containing the effluent.
Ciii) Activated sludge systems where the effluent is contained in a tank or pond, to which air is supplied to carry out the digestion under aerobic conditions and which permit a greater rate of digestion than (i) or Cii). Effluent conversion is limited by the need to re-cycle some of the microbial sludge and liquor to provide continued generation of the micro- ~- -organisms.
Civ) Trickle filter systems where the active microorganisms grow on a -support medium, effluent and air being circulated over the bacterial growth to effect conversion of the effluent.
The present invention is concerned particularly, with the trickle filter type of system but also extends to systems of the activated sludge or extended aeration types.
Typically, trickle filter plants are composed of crushed rock ;:~
retained in a bed some 6 feet C2 metres) deep and up to 200 feet (60 metres) wide. Effluent is sprayed over the top of the bed and air is allowed to circulate through the bed from the top and open (or porous) base of the bed.
Microbial growth takes place on the surface of the rock. Such plants are -1- ~
. . .
.
1~551~;9 limited in size, usefulness, and efficiency, by land use requirements, weight of rock, air accessibility, susceptibility to flies, and other factors.
Recently plastic support media have replaced rock and stone in trickle filter systems, giving the advantages of lighter weight, higher surface to volume ratios, and greater open volume for better air penetration.
This has allowed the development of deeper, more efficient beds, and also tota immersion treatments where the support medium is fully immersed in the effluent and air or oxygen is pumped through the bed.
Such plastic support media are frequently constructed in the form of solid, i.e., imperforate, sheets having a variety of corrugated patterns.
Some examples are the materials known as *Flocor tICI Aust. Ltd.) and *Surfpac tnOw Co. Aust. Ltd.). Other types of support media include discs, rings, spoked wheels and other shapes designed to facilitate microbial growth, with maximum void space to provide for adequate air circulation.
According to the present invention there is provided a support medium for the biological treatment of sewage or other effluent, said medium comprising a plurality of superposed layers of a mesh-like material, the sheets being disposed so as to avoid superposition of the apertures of at least some adjacent sheets.
Simply by randomly laying one sheet on another, it has been found that superposition of the apertures of a satisfactory number of adjacent sheets is achieved. It should be appreciated, however, that this number can be increased and the efficiency of the medium improved by d~liberately arranging the sheets to avoid superposition of the apertures.
Thus, according to another aspect of the invention, there is a support medium when used for the biological treatment of sewage or other aqueous effluent, said medium comprising a plurality of superposed sheets of a mesh-like material, the sheets being disposed so as to avoid super-position of the apertures of adjacen~ sheets.
The preferred material for the mesh is a plastics material and it * trade marks ~, ~
1~551t;9 is specifically preferred to use a foamed plastics material. Some examples of suitable materials of this latter type already manufactured are those sold under the trade names "Trical" and "Netlon".
In the preferred arrangement of the medium, the sheets or layers correspond in shape and area to the cross-section of the tank or other vessel in which they are contained, i.e. each layer spans the full cross-section of the vessel. It is, however, within the scope of the invention to use layers which are of smaller area than the containing vessel.
Thus in another aspect of the invention there is provided apparatus, such as a trickle filter, for the treatment of sewage or other aqueous effluent the apparatus comprising a vessel which is at least partly filled with the support medium.
Table 1 compares the density of packing ~i.e., a 'bulk density'), calculated surface area per unit volume and void space of the total volume of the packing for typical prior art materials used in trickle filter applications, together with the same properties for support media in accord- - -ance with the present invention.
2-6 cm Rock FormedPlastic 2.5 x 2.5 x particles PlasticWheels 3.5cm 2.5cm Sheet Plastic Plastic Mesh* Mesh*
. __ ... .
Packing Density kgm/m 1450 37 150 69 81 Surface area m /m 99 89 225 260 310 Void space % 45 80 77 73 ~ -* Plastic mesh comprising 2.5 to 4.0mm oval cross-section meshes at quoted spacings, made from polyethylene foamed to specific gravity of approximately 0.3 gm/cm The particular advantages to be gained from use of a plastic mesh packing medium will thus be seen to include: ease of installation (as no complexities in assembly or packing are involved), high area per unit volume
. __ ... .
Packing Density kgm/m 1450 37 150 69 81 Surface area m /m 99 89 225 260 310 Void space % 45 80 77 73 ~ -* Plastic mesh comprising 2.5 to 4.0mm oval cross-section meshes at quoted spacings, made from polyethylene foamed to specific gravity of approximately 0.3 gm/cm The particular advantages to be gained from use of a plastic mesh packing medium will thus be seen to include: ease of installation (as no complexities in assembly or packing are involved), high area per unit volume
-3-~J
of packing, retention of adequate void space for aeration, and low weight of the packed bed.
The data of Table 1 illustrate the advantages, relative to previous-ly used materials, of employing a mesh support medium in bio-oxidation sew-age and effluent treatment plants. In particular the mesh materials have superior surface area while retaining ~avourable packing density and void space characteristics.
-3a-~,,, Although unfoamed, i.e., solid, plastics materials may be used to form the mesh, the maximum advantage is obtained by use of a foamed plastic mesh, which is of lighter weight than unfoamed materials and provides a higher effective surface area due to the slight surface roughness of the foamed material. Additionally, for totally immersed beds, the packing will float and thus provide support for additional weight of the microbial growth.
EXAMPLE
In an experimental sewage treatment plant a tower approximately lm x 2.8m in area and 2.8m high was packed with ta) a conventional filling of plastic spoked wheels (supplied by Mass Transfer Ltd.) and (b) sheets of 2.5 x 3.5 cm (mesh openingj foamed plastic mesh. The sheets were cut to fit the tower cross-section (approximately 2m square metres) and stacked horizon-tally in the column, the cutting and disposition of the layers being such as to avoid superposition of the apertures of adjacent layers. The relative packing surface areas for the wheel- and mesh- packed column were 225 and 260m2/m3 respectively. The plant was operated, using each type of packing, at a rate of about 41m3 per day on raw sewage of 300-500 ppm B.O.D. level us-ing the extended aeration principle wherein the support medium carrying the bacterial flock remains fully immersed in the sewage liquors, and air is pump-ed into the tank so that it penetrates through the liquor and support medium to effect bio-oxidation. The treatment plant worked equally well with both types of packing, yielding an effluent of 120 - 150 ppm B.O.D. with 180 ppm ~ -solids, which after settling and clarification gave effluent B.O.D. levels of 20-30 ppm in both cases. With such a small area difference it was not possible to detect any improvement in performance from the mesh packing. Nevertheless the experiment demonstrates that the support medium of the invention is cap-able of at least the same performance as the prior art materials and thus provides a support of lower cost and greater ease of use than the latter.
Those skilled in the art will appreciate that the invention describ-ed herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the invention includes all such variations and modifications which fall within its spirit and scope.
,
of packing, retention of adequate void space for aeration, and low weight of the packed bed.
The data of Table 1 illustrate the advantages, relative to previous-ly used materials, of employing a mesh support medium in bio-oxidation sew-age and effluent treatment plants. In particular the mesh materials have superior surface area while retaining ~avourable packing density and void space characteristics.
-3a-~,,, Although unfoamed, i.e., solid, plastics materials may be used to form the mesh, the maximum advantage is obtained by use of a foamed plastic mesh, which is of lighter weight than unfoamed materials and provides a higher effective surface area due to the slight surface roughness of the foamed material. Additionally, for totally immersed beds, the packing will float and thus provide support for additional weight of the microbial growth.
EXAMPLE
In an experimental sewage treatment plant a tower approximately lm x 2.8m in area and 2.8m high was packed with ta) a conventional filling of plastic spoked wheels (supplied by Mass Transfer Ltd.) and (b) sheets of 2.5 x 3.5 cm (mesh openingj foamed plastic mesh. The sheets were cut to fit the tower cross-section (approximately 2m square metres) and stacked horizon-tally in the column, the cutting and disposition of the layers being such as to avoid superposition of the apertures of adjacent layers. The relative packing surface areas for the wheel- and mesh- packed column were 225 and 260m2/m3 respectively. The plant was operated, using each type of packing, at a rate of about 41m3 per day on raw sewage of 300-500 ppm B.O.D. level us-ing the extended aeration principle wherein the support medium carrying the bacterial flock remains fully immersed in the sewage liquors, and air is pump-ed into the tank so that it penetrates through the liquor and support medium to effect bio-oxidation. The treatment plant worked equally well with both types of packing, yielding an effluent of 120 - 150 ppm B.O.D. with 180 ppm ~ -solids, which after settling and clarification gave effluent B.O.D. levels of 20-30 ppm in both cases. With such a small area difference it was not possible to detect any improvement in performance from the mesh packing. Nevertheless the experiment demonstrates that the support medium of the invention is cap-able of at least the same performance as the prior art materials and thus provides a support of lower cost and greater ease of use than the latter.
Those skilled in the art will appreciate that the invention describ-ed herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the invention includes all such variations and modifications which fall within its spirit and scope.
,
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A support medium when used for the biological treatment of sewage or other aqueous effluent, said medium comprising a plurality of superposed sheets of a mesh-like material, the sheets being disposed so as to avoid superposition of the apertures of at least some adjacent sheets.
2. A support medium when used for the biological treatment of sewage or other aqueous effluent, said medium comprising a plurality of superposed sheets of a mesh-like material, the sheets being disposed so as to avoid superposition of the apertures of adjacent sheets.
3. A medium as claimed in claim 1 or claim 2, wherein the mesh-like material is made from a plastics material.
4. A medium as claimed in claim 1 or claim 2, wherein the mesh-like material is made from a foamed plastics material.
5. A medium as claimed in claim 1 or claim 2 wherein the mesh-like material is made from a foamed plastics material and wherein the plastics material is a polyethylene foamed to a specific gravity of about 0.3 gcm 1.
6. Apparatus when used for the treatment of sewage or other aqueous effluent comprising a vessel which is at least partly filled with a support medium as defined in claim 1.
7. Apparatus as claimed in claim 6, wherein the sheets of the mesh-like material correspond in size and shape to the cross-section of the vessel.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU981374 | 1974-11-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1055169A true CA1055169A (en) | 1979-05-22 |
Family
ID=3700616
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA240,638A Expired CA1055169A (en) | 1974-11-28 | 1975-11-27 | Support medium for biological treatment |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5178059A (en) |
| AU (1) | AU8683075A (en) |
| CA (1) | CA1055169A (en) |
| DE (1) | DE2553602A1 (en) |
| FR (1) | FR2292672A1 (en) |
| GB (1) | GB1497130A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4503150A (en) * | 1983-11-02 | 1985-03-05 | Scotfoam Corporation | Polyurethane foam and a microbiological metabolizing system |
| WO1986004923A1 (en) * | 1985-02-26 | 1986-08-28 | Scotfoam Corporation | Polyurethane foam and a microbiological metabolizing system |
| US6284531B1 (en) | 2000-01-12 | 2001-09-04 | Hong Zhu | Multi-compartment device for cultivating microorganisms |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS52152649A (en) * | 1976-06-11 | 1977-12-19 | Nagasei Kougiyou Kk | Water treating method by using moving contact bed |
| JPS54103253A (en) * | 1978-01-30 | 1979-08-14 | Kato Masashi | Method of treating water with laminated net medium |
| US20210070641A1 (en) * | 2017-09-18 | 2021-03-11 | Drain Fields Patents Ab | Modular bio bed and ventilated system for waste water treatment |
-
1974
- 1974-11-28 AU AU86830/75A patent/AU8683075A/en not_active Expired
-
1975
- 1975-11-27 GB GB4884675A patent/GB1497130A/en not_active Expired
- 1975-11-27 CA CA240,638A patent/CA1055169A/en not_active Expired
- 1975-11-27 JP JP14214275A patent/JPS5178059A/ja active Pending
- 1975-11-27 FR FR7536293A patent/FR2292672A1/en not_active Withdrawn
- 1975-11-28 DE DE19752553602 patent/DE2553602A1/en not_active Withdrawn
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4503150A (en) * | 1983-11-02 | 1985-03-05 | Scotfoam Corporation | Polyurethane foam and a microbiological metabolizing system |
| WO1986004923A1 (en) * | 1985-02-26 | 1986-08-28 | Scotfoam Corporation | Polyurethane foam and a microbiological metabolizing system |
| US6284531B1 (en) | 2000-01-12 | 2001-09-04 | Hong Zhu | Multi-compartment device for cultivating microorganisms |
Also Published As
| Publication number | Publication date |
|---|---|
| GB1497130A (en) | 1978-01-05 |
| DE2553602A1 (en) | 1976-08-12 |
| JPS5178059A (en) | 1976-07-07 |
| FR2292672A1 (en) | 1976-06-25 |
| AU8683075A (en) | 1977-05-26 |
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