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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D39/00—Filtering material for liquid or gaseous fluids
  • B01D39/02—Loose filtering material, e.g. loose fibres
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J19/30—Loose or shaped packing elements, e.g. Raschig rings or Berl saddles, for pouring into the apparatus for mass or heat transfer
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/30—Details relating to random packing elements
  • B01J2219/302—Basic shape of the elements
  • B01J2219/30223—Cylinder
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/30—Details relating to random packing elements
  • B01J2219/304—Composition or microstructure of the elements
  • B01J2219/30466—Plastics
• • 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

Definitions

• the present invention relates to an improved filtration medium for use in the biological and mechanical treatment of water for a range of uses and, more particularly, for water used in recirculating systems.
• the management of recirculating aqueous systems has an important bearing on the aquaculture, aquarium and water purification industries.
• Nitrates produced as the end products ofthe nitrification processes are then disposed of either by the regular replacement of a proportion ofthe water in the system, by the harvesting of plant material which feeds on the nitrates, or through the further anaerobic conversion of nitrates to free nitrogen by other bacteria.
• Nitrification gives rise to the formation of certain dust-like particulate material which is referred to by those with knowledge ofthe art as "biofloc". This material accumulates within the system, and more particularly, within the media and requires periodic removal in order that the performance and flow characteristics ofthe biological media might be maintained.
• Narious types of media have been used for bacterial colonisation. These media usually take the form of a fibrous, lattice-like or porous bed through which the water is passed in any direction. The media may be fully submerged, partly submerged or free draining. Gravel, oyster shells, sand, woven materials, plastic shapes and so on are all employed for water treatment and the efficacy of such media depends, among other things, on the total surface area offered within the media bed for colonisation by nitrifying bacteria and the ease with which the flowing water finds exposure to these surfaces.
• Porous materials such as activated charcoal, scintered glass and materials with scratched or stippled surfaces have also been used in an attempt to maximise the surface area available for colonisation by bacteria. Such materials are quickly colonised but, after a time, the very small voids and pores that attracted the bacteria become filled with biofloc, dead unicellular algae and other small particles. Water flow through these pores is then restricted; biological action deteriorates and the biological performance ofthe medium begins to approximate that of a non-porous medium of similar shape and size. Often within a matter of months, such porous materials require aggressive cleaning, which also removes the bacteria, or partial replacement.
• Solids can be entrapped and or removed from the system in a number of ways. Solids can be collected in a settling chamber, of any design, in which the velocity ofthe water is reduced sufficiently for the solids to fall to the bottom where they can accumulate for decomposition or removal. Solids can also be entrapped in any type of mesh or gauze which can be removed for regular cleaning or replacement or may remain in place to provide a site for decomposition. Solids may also be trapped in a medium which can be cleaned in situ. Some systems attempt to use the biological medium for the dual purpose of biological treatment and solids capture, with the solids either remaining in the media until ultimate decomposition, or until the media is removed in whole or in part for cleaning, or is cleaned in situ.
• the excessive accumulation of organic particulates within the media can substantially increase the biological oxygen demand ofthe system, with decaying solid matter and beneficial aerobic bacteria competing for the available oxygen.
• the efficacy of biological filtration depends to a considerable extent on the delivery of an adequate supply of dissolved oxygen to the aerobic nitrifying bacteria, and the periodic or continuous removal of decaying solid wastes is regarded as desirable practice by those with knowledge ofthe art. If the biological media is relied upon for the collection of decaying solids there arises the difficulty of removing such solids without excessive damage to the delicate bacterial films on the surfaces ofthe media.
• An ideal filtration medium comprises cylindrical or tubular elements, because ofthe large available surface area, and because ofthe ease of cleaning by back washing or the like, with minimal damage to any bacterial films that are being relied upon to treat the water.
• Japanese patent No. JP59-123596 describes the use of extruded plastic foam cylinders 3- 10mm in diameter, 3-10mm in length and with a wall thickness of 0.1-0.14mm. The outer surfaces ofthe cylinders described therein are scratched, using an apparatus described, to provide an enhanced environment for colonisation by bacteria and to ameliorate the ongoing deterioration of porous media described previously herein.
• Japanese patent No. JP07-068288 describes a technique for the rapid biological treatment of waste waters in which are used cylindrical, toroidal or disc-shaped elements manufactured from porous polyvinyl formal of SG 1.0— 1.25.
• One embodiment therein describes the use of cylindrical elements of 0.5- 10mm diameter and 0.5- 10mm length, with preferred dimensions 2-5mm diameter and 2-5mm length. Pore size is described as no more than 2,000 microns.
• a biological and mechanical filtration medium comprising a plurality of randomly disposed hollow cylindrical or tubular elements of predetermined size and density.
• the filtration medium comprises a plurality of massed cylindrical or tubular elements which are randomly dispersed in any plane.
• the cylindrical or tubular elements have an outside diameter in the range of about 2.7 to 3.5mm, a length in the range of about 3.0 to 4.5mm, a wall thickness of about 0.2 to 0.4mm, and a ratio of length to diameter of about 1.5 : 1.
• the cylindrical or tubular elements are fabricated from plastics material having a specific gravity of about 0.85 to 0.95, and have a relatively smooth non-porous surface finish, which is amenable to the establishment of a bacterial film thereon over a relatively large surface area.
• the bacterial film which forms on the inner surfaces ofthe tubular elements is protected from mechanical damage during agitation.
• the tubular elements are fabricated from extruded plastics material, cut off to the required length(s), the ends ofwhich may be at any angle to the longitudinal axis ofthe tubular element.
• the filtration medium of massed tubular elements comprises about 90% of void or open space, providing minimal resistance to fluid flow.
• the filtration medium is contained within a larger volume filtration vessel for filtration, backwashing and rinsing procedures.
• the filtration medium can be agitated by mechanical hydraulic or pneumatic means such that the cylindrical elements, and the particulate material entrapped within and between the elements are separated therefrom and dispersed.
• the filtration medium comprises a mass biological medium comprised of small plastic cylinders measuring approximately 2.7-3.5mm in diameter and 4.0-5.0mm long with a wall thickness of approximately 0.2- 0.4mm.
• a preferred size is 3.0mm and 4.5mm length.
• the cylinders have a relatively smooth surface and are manufactured from any plastic material with a specific gravity in the range of about 0.85-0.99 (preferably 0.89-0.91).
• the optimal ratio of length to diameter of 1.5 (4.5mm:3.0mm) ofthe preferred cylindrical elements provides a medium exhibiting a large surface area, a high proportion of open space, large aperture size when the cylindrical elements are massed in great numbers and the ability to separate and move freely when agitated in a column of moving water.
• the cylinders are randomly packed in large numbers into a containment vessel, of any design, through which the water to be filtered is passed.
• the geometry ofthe cylindrical shapes prevents close-packing or jamming ofthe cylindrical elements and yields a bulk material ofwhich volume is approximately 90% void space. This allows the material to retain a large quantity of solids without blocking or channelling.
• the high proportion of void space and large average aperture size also reduce the velocity ofthe water against the surface ofthe media, reducing water speed and pumping losses, increasing retention time, promoting bacterial growth and encouraging the retention of solids.
• the cylindrical elements are slightly buoyant, but become either neutrally buoyant or negatively buoyant as the build-up of introduced solids and biofloc progresses on the smooth surfaces ofthe medium. At some point, the massed cylindrical elements require cleaning in order to remove this accumulated material.
• each cylindrical particle with respect to those surrounding it changes drastically when the massed material is agitated or back-washed.
• the material then moves freely, expanding in volume as the particles separate. Because the surfaces of the cylindrical elements are relatively smooth, accumulated solids are quickly shed into the surrounding water stream, which is then diverted to waste. Additional agitation may be provided by aerating the massed material, mechanically agitating it with a mixing device, or pumping it in a fluidised state through another separation apparatus.
• Bacteria housed on the inner surfaces ofthe cylindrical elements are protected from excessive damage during agitation.
• the preferred embodiment ofthe invention is for cylindrical shaped herein described and exhibiting the following physical properties: Base material specific gravity 0.9
• the present invention relates to a mechanical medium which provides a substantial surface area, a large proportion of void space, large aperture size and the ability to be cleaned by simple agitation or back-washing.
• the present invention provides a substantial advance in biological and mechanical filtration medium providing all ofthe herein-described advantages without incurring any relative disadvantages.

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Hydrology & Water Resources (AREA)
• Environmental & Geological Engineering (AREA)
• Water Supply & Treatment (AREA)
• Engineering & Computer Science (AREA)
• Microbiology (AREA)
• Biodiversity & Conservation Biology (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Biological Treatment Of Waste Water (AREA)
• Removal Of Floating Material (AREA)

Applications Claiming Priority (3)

Publications (2)

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Citations (3)

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• 1995
  • 1995-08-11 AU AUPN4747A patent/AUPN474795A0/en not_active Abandoned
• 1996
  • 1996-08-12 WO PCT/AU1996/000504 patent/WO1997007063A1/en not_active Application Discontinuation
  • 1996-08-12 NZ NZ313929A patent/NZ313929A/en active IP Right Revival
  • 1996-08-12 EP EP96926265A patent/EP0843651A4/de not_active Withdrawn

Patent Citations (3)

Non-Patent Citations (1)

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