PATENT SPECIFICATION
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`(11)
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`1 560 581
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`(21) Application No, 38179/76
`(22) Filed 15 Sep. 1976
`(31) Convention Application Nos. 613327 (32) Filed 15 Sep. 1975
`677697
`16 Apr. 1976 in
`(33) United States of America (US)
`(44) Complete Specification Published 6 Feb. 1980
`(51) INT. CL.3—AOLK 63/04
`CO2F 3/06 3/34 //
`FO4F 1/18
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`1560581
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`(54) WATER FILTRATION DEVICE
`
`(71) We, HENRY EVAN ORENSTEN
`and VIVIAN CAROL ORENSTEN, of
`8724 Westmoreland Lane, St. Louis Park,
`Minnesota, United States of America, both
`citizens of the United States of America, do
`hereby declare the invention, for which we
`pray that a patent may be grantedto us, and
`the method by whichit is to be performed.
`to be particularly described in and by the
`following statement:
`This invention relates to a submersible
`air-induction type waterfiltration device for
`an aquarium.
`An aquarium is a minature ecosystem.
`The aquatic life within this ecosystem pro-
`duce metabolites and wastes, consume ox-
`ygen, and slowly poison their own environ-
`ment. Some form of water purification or
`filtration is eventually needed to reduce
`mortality and disease.
`There are several fundamentally different
`approaches to aquarium purification or fil-
`tration. In one approach which relies heavi-
`ly on bacterial action, water in the aquarium
`tank (or holding tank or stock tank, as the
`case may be) circulates through a filter bed
`or otherfiltration device located inside the
`tank.
`In another approach,
`the filter
`medium or device is external to the tank,
`and a pump, siphon, or the like, draws
`water from the tank, so that it can be passed
`through the external filter and returned to
`the tank in substantially purified form. In
`the first (submerged filter) approach, che-
`mical and/or mechanical filtration means
`can be combined with the bacterial action in
`the filtration process.
`When the filter medium is submerged
`within the water in the tank,
`it
`is not
`absolutely necessary to use a powerful water
`
`pump. Relatively inexpensive ‘‘air-
`induction” pumps can be used. These
`pumps force a stream of air into the tank,
`and the air stream induces a flow of water
`through the filtration device submerged in
`the tank. Although air induction is not as
`efficient or powerful as, for example, an
`impeller action exerted directly upon the
`water, substantial flow rates can be achieved
`with this air-induction technique, e.g. flow
`rates in excess of 30 gallons per hour, using
`an air pump with 3 watts of power.
`As noted previously,thefiltration process
`which takes place in the tank can be
`mechanical, chemical, biological, or some
`combination of any of these. The combina-
`tion of biologicalfiltration with other means
`of filtration appears to be the most effective
`and the least disturbing to the aquatic
`ecosystem, since it takes advantage of the
`so-called nitrogen cycle to convert
`toxic
`metabolites and wastes in the water (e.g.
`ammonia) to relatively harmless or relative-
`ly less harmful substances (e.g. nitrites and
`ultimately to nitrates or even fixed nit-
`rogen). For a detailed discussion of the
`nitrogen cycle, see Stephen H. Spotte, Fish
`and Invertebrate Culture, Wiley-Inter-
`Science, New York, New York 1970, pp3-
`21. Pages 9-13 of this work by Spotte
`contain a detailed discussion of airlifts and
`airlift conduits.
`It is well known that organic matter in the
`aquarium water can build up in a filtration
`device (e.g. in the so-called “under-gravel”
`filter, which includes a bed of gravel serving
`as the filtration medium) and provide a
`nutrient medium for micro-organisms (bac-
`teria, algae, etc.) which are capable of
`reducing levels of toxicity in the water. In
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`a a
`
`for breaking up the stream of air into air
`nother context, it has been suggested that a
`bubbles,
`“dirty” filter (which contains a: possible
`(c)
`extending upward from said air
`nutrient medium for bacteria) should be
`directing means and said diffusing element,
`retained in a filtration system as long as is
`a filtration element positioner operably
`reasonably possible, e.g. by replacing only
`associated with said base for holding a
`part of the filter material when it becomes
`filtration element
`in a generally vertical
`clogged and begins to resist fluid flow too
`position,
`strongly. See Tropical Fish Hobbyist, Vol.
`(d)
`a generally vertically extending fil-
`XX,Sept. 1971, pp 85-88. In actual practice,
`tration element positioned upon said posi-
`it has been found that the complete replace-
`tioner and extending upwardly therefrom,
`mentor cleaningof a biologicalfilter device
`said filtration element having a hollow,
`can bring on a condition known as “new
`generally vertically extending core open at
`tank syndrome”, i.e. increased mortality or
`its upper and lower ends and a porous
`disease in the aquaticlife which is generally
`surface, said lower end being positioned by
`attributed to the temporary lack ofsufficient
`the said positoner.
`biological water-purifying action. Furth-
`The invention is based on the discovery
`ermore, even a well-cultured biologically
`that an unusually efficient biological filter-
`active filter element may not be adequate
`ing action for both fresh water and marine
`for marine tanks or crowded fresh water
`aquariums can be obtained with an air-
`tanks.
`induction filtration system in which the air
`Oneof the most convenienttypes offilter
`stream, after passing through a diffuser
`structures is the type where the filtration
`element or the like,
`is introduced at the
`medium is arranged about a hollow longitu-
`bottom of the hollow axial core of an
`dinal core. The filtration medium is pro-
`integral porous submerged filter element,
`vided with enough integrity (e.g. by a
`thus causing waterto flow throughthefilter
`suitable forming process or by use of rein-
`element from its exposed outer surface to
`forcing devices or members) ta be handled
`the hollow inner core. In order to provide
`as a removable filtration element. One of
`this improved filtering action, it is particu-
`the advantages of these integral, porous
`larly important that the porousintegralfilter
`filtration elements is that the hollow core
`elements be capable of permitting an un-
`can be used to house a second filtration
`usually high flow rate through the pores or
`medium, e.g. a bed of elemental carbon
`interstices of the filter medium, even when
`particles or the like. Thefiltration medium
`the filter medium has become partially
`can comprise cellulosic material, inorganic
`clogged due to the deposition or entrapment
`fibers, synthetic organic fibers, or thelike.
`of detritus, fecal matter etc., present in the
`The fibers can be woven or non-woven. For
`waterof the aquatic life support system. For
`an example ofafilter medium which is a
`example, the surface area and porosity of
`porous, physically solid unit with sufficient
`the filter element should be sufficient to
`integrity to be handled as an integral car-
`permit a flow rate well
`in excess of 40
`tridge or insert, see U.S. Patent 3,313,421
`gallons per hour (e.g. 50-100 gallons per
`(Falkenberg et al),
`issued April 11 1967.
`hour), with an air pump rated at 1.5 to 3
`Unfortunately, it can be somewhat difficult
`watts of power; when thefilter element is
`to make full use of such integral filter
`fresh and unclogged, and well over 25
`cartridges in a biologically active air-
`gallons per hour when the filter element
`induction system.
`contains a significant amount of sediment
`The state of the art is believed to be
`(e.g. detritus). In operation, a mass oftiny
`illustrated by the following U.S. Patents:
`air bubbles passes up the hollow axial core
`Nos. 3,149,608, 3,232,271, 3,276,428,
`of
`the filter element drawing this vast
`3,292,579, 3,313,421, 3,487,440 and
`volume of water
`through the filtration
`3,557,753.
`medium and up along with the flow of
`According to the invention there is pro-
`bubbles. Although high flow rates are pre-
`vided a submersibleair-induction type water
`ferably achieved with a minimum of power,
`filtration device for an aquarium which
`high wattages (e.g. 50 watts or more) can be
`includes a base for positioning of said device
`used,
`if desired.
`on the aquarium floor and positioned on
`In one embodiment of the invention,
`said base a plurality of air-induction filtra-
`additional filtering action can be provided
`tion arrangements, each of said plurality of
`with other mechanical and/or chemicalfil-
`air-induction filtration arrangements com-
`tering devices, e.g. a mass of elemental
`prising:
`carbon particles (such as activated charcoal
`an air inlet means integral with said
`(a)
`particles) inserted within one or moreof the
`base, said air inlet means being in fluid
`hollow axial cores.
`communication with an air directing means
`It has also been discovered that increased
`for directing a stream of air upwards,
`flow rates can be obtainedbyaffixing an air
`(b)
`an air-permeable diffusing element,
`lift conduit of a certain length to the upper
`superposed upon said air directing means,
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`1 560 581
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`end of the hollow core of at least one of the
`filtration elements preferably to the upper
`endof eachfiltration element. For example,
`the use of a relatively short air lift conduit
`(e.g. from about 1 to 10 inchesin length or
`about 2.5-25 cm) was found to increase the
`flow rate by about 25% to 75% over the
`flow rate obtained using the same system
`without the air lift conduit, provided the
`entire air lift conduit is submerged. Present-
`ly available data indicate that the optimum
`air lift conduit length for every air pressure
`and water flow rate is such that the upper
`end of the conduit
`is in closely spaced
`relationship to the surface of the body of
`water in the aquarium. The increased flow
`rates obtained with this embodiment serve
`to increase the level of the water purifica-
`tion or filtration action of the system and
`thereby improve the health of the aquatic
`life within the ecosystem.
`Still another discovery is that water filtra-
`tion devices of this invention are useful in
`combination with other water purification
`systems, e.g. the systems disclosed in U.S.
`Patent No. 3,957,634 and U.S. Patent
`3,722,685.
`In any of these embodiments, “new tank
`syndrome” can be reduced or avoided by
`pre-culturing of one or morefiltration ele-
`ments with living colonies of nitrifying
`microorganisms. Since the filtration device
`contains a plurality of porous integralfiltra-
`tion elements, it is relatively easy to main-
`tain at least one fully cultured filter element
`in the tank at all times - and this cultured
`filter element can be one which was original-
`ly fresh [or “clean”’] and was subsequently
`cultured while in service in the tank.
`In the accompanying drawings:
`Figure J is a perspective view of a fully
`assembled filtration device ofthis invention,
`including a decorative cover means which
`camouflages the internal workings of the
`device.
`Figure 2 is a sectional view taken along
`lines 2-2 of Figure 1.
`Figure 3 is a sectional view taken along
`lines 3-3 of Figure 1, with parts broken away
`to show details of the structure of the
`filtration elements.
`Figure 4 is a top plan view of the base or
`support member shown in Figures 2 - 3.
`Figure 3 is a perspective view of a
`complete aquatic life support system includ-
`ing the fully assembled filtration device of
`this invention, which includes both a de-
`corative cover means for camouflaging the
`internal workings of the device and an air
`lift conduit, in combination with the exter-
`nal filtration system described in U.S. Pa-
`tent No. 3,957,634.
`Figure 6 is a fragmentary view showing
`the same device as shown in Figure 2, but
`with the addition of the air lift conduit.
`
`This invention seeks to maximize the
`biological action of nitrifying microorgan-
`isms such as algae and/or autotrophic bac-
`teria such as Nitrosomonas sp., Nitrobacter
`sp., and/or heterotrophic bacteria or the
`like. In use, the aquatic life support system
`and the filtration system are preferably
`operated to favor establishment and mainte-
`nance of autotrophic bacterial colonies; for
`example, sudden changes in pH orsalinity
`or hardness or soluble carbonate concentra-
`tion should be minimized or avoided and
`antibiotic, bacteriostatic, and bacteriocidal
`treatments
`should generally be avoided
`completely. High flow rates, however, seem
`to have little, if any, adverse effect upon
`colonies of autotrophic bacteria in the biolo-
`gical filter elements.
`A plurality of integral porous filtration
`elements are included in the filtration de-
`vice. As pointed out previously, this facili-
`tates the continuous maintenanceofa living
`colony of nitrifying microorganisms in the
`tank. It is not necessary that any of the
`filtration elements be pre-cultured, pro-
`vided that a sufficient “run-in” period is
`used. During the “run-in” period, the fish
`population should be kept to a minimum.
`Even a small fish population will excrete
`sufficient wastes
`to provide a nutrient
`medium in thefiltration elements and, as a
`result, the desired bacterial culture. Com-
`pared to ‘under gravel’’ filtration systems,
`aquarium system maintenance can be great-
`ly simplified and reduced. For example,
`frequency of water changes and cleaning of
`the system (e.g. gravel beds) can be re-
`duced. Ordinarily,
`it
`is
`sufficient
`to
`periodically replace one of the clogged or
`dirty filtration elements, leaving the other
`elementin place for continued maintenance
`of biological action. This alternating re-
`placement of filter elements can continue
`moreor less indefiniely, thus maintaining a
`high flow rate as well as a high level of
`biological filtering action.
`In this invention,
`the advantages of an
`external filter can be combined with the
`advantages of a submerged filter, while
`minimizing the disadvantages of both. The
`integralfilter elements of this invention are,
`in effect, sealed in place in the filtration
`device to minimize by-passing of the filtra-
`tion medium. Matting or compressing of a
`particulate or
`fibrous filter bed can be
`avoided. Stagnant areas in the aquarium
`tank are minimized. If a decorative gravel
`bed or the like is included in the tank, such
`bed can be arranged to provide a secondary
`filtering or purifying action with a minimum
`of risk that stagnant areas will be intro-
`duced.
`the invention
`Among the features of
`which are believed to contribute to the
`attainment of
`these advantages are the
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`1 560 581
`concens
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`peripheral water flow inducing effect cre-
`ated by the flow ofair up through a hollow
`core of an integral filter element and the
`surprisingly high flow rates, e.g. more than
`135 gallons per hour for
`the preferred
`embodiment operating at peak efficiency.
`Considerably higher
`flow rates can be
`obtained when the air
`lift conduit
`is
`arranged in register with the top of the
`hollow core of each filter element, as
`mentioned previously. To accommodate
`such high flow rates, an unusually porous
`filter element structure is preferred, which
`will be described in detail subsequently.
`Turning now to a detailed description of
`the drawing, Figure 1 illustrates the com-
`pletefiltration device 10 with the decorative
`cover means 100 in place, such that the only
`internal workings of the filtration device
`which can be seen are the air hoses 5 and 6
`which are connected to air inlets 15 and 16
`(Figure 4) to convey air streams from a
`suitable air pump means (not shown). For
`convenience ofillustration, only portions of
`hoses 5 and 6 are shown. Cover means 100
`includes circular openings 161 at the top.
`For decorative purposes, openings 161 are
`intended to simulate the mouths of a twin
`volcano. Openings 161 are in register with
`the hollow axial coresin filtration elements
`50 and 60, the hollow coresbeing defined by
`serrated hollow axially disposed elements61
`(Figures 2 and 3). Thus, the air which is
`introduced via hoses 5 and 6 through inlet
`conduits 15 and 16 passes through these
`hollow cores and emerges from openings
`161. This air flow draws water through
`openings 103 in the molded ridges 101 of
`cover 100. The water drawn through open-
`ings 103 flows through the filtration ele-
`ments 50 and 60,
`i.e. from the exposed
`surfaces of elements 50 and 60 through to
`the hollow cores defined by axial cylindrical
`elements 61. The water
`flow, when it
`reaches the hollow axial cores is substantial-
`ly purified and is returned to the main body
`of water in the aquatic life support system
`by flowing out through openings 161 along
`with the aforementioned flow ofair. In the
`preferred embodiment of cover means 100
`shown in Figures 1 - 3, a flange means {11
`extends outward from the lower periphery
`of the cover. The flange is provided with
`U-shaped openings 115 to accommodate air
`inlets 15 and 16 (Figure 4). Since flange 111
`rests upon the floor 150 of the aquarium
`tank (Figure 3), sand or gravel or other
`decorative particles (not shown) can be
`heaped up around the bottom of cover 100,
`covering flange 111 and helping to hold
`cover 100 in place. An additional aid for
`holding cover 100 in place is opening 105 on
`the top surface of cover 100. This opening
`can serve as an exhaust for any air trapped
`under the central high point of this surface
`
`of the cover, Extending downward from
`openings 161 are ring-like or tubular loca-
`tors or fasteners, i.e. positioners 124, which
`are constructed and arranged to have a
`frictional engagementaction with thefiltra-
`tion elements. This frictional engagement
`helps to properly position cover 100 as well
`as to hold it in place.
`It should be noted that, since relatively
`low density materials such as the polyolefins
`can be used in the fabrication of one or
`more elements of the filtration device (e.g.
`polyolefin fibers can be usedin thefiltration
`elements 50 and 60), the entire filtration
`device 10 may have a tendency tofloat to
`the surface of the water in which it
`is
`submerged. In addition to the anchorin
`action provided by particles (not shown)
`heaped up on flange 111, a very secure
`attachmentto the floor 150 of the aquarium
`can be achieved with an addtional anchoring
`
`soans, in this case, suction cup 41 (Figure
`Theprincipal functional elements of the
`filtration device 10 which are housed by
`cover 100 are the base or support member
`11 and thefiltration elements 50 and 60,
`supported and positioned by base member
`11. The base member 11 includes an air
`directing and diffusing system comprising
`air inlet 15 and 16, conduits 17 and 18, and
`recess means 13 and 14. These recesses
`define all but
`the top surface of an air
`chamber. The top surfaces of the two air
`chambers are provided by removable air
`diffuser elements 31 and 32. These elements
`are porous, sheet-like disc members prefer-
`ably fabricated from synthetic organic
`polymeric materials (e.g. polyolefins such as
`polypropylene). These diffuser elements 31
`and 32 serve substantially the same function
`as the familiar “air stone’, e.g. element 72
`in Figure 2 of the aforementioned Newsted-
`er U.S. Patent No. 3,487,440, but have
`several advantages over conventional air
`stones. The porous discs 31 and 32 tend to
`be biologically inert and resistant to clog-
`ging. Once clogged,
`they are easily re-
`placed. Furthermore, they provide efficient
`diffuser action while occupying a tiny
`volume, thus simplifying the design of the
`device. The diffuser elements break up the
`flow of air passing through inlets 15 and 16
`and airways 17 and 18 thereof into a mass of
`tiny air bubbles which passes up the hollow
`axial cores offiltration elements 50 and 60.
`Diffuser elements 31 and 32 are inter-
`posed between, first, shoulders 13 and 14 of
`the wails of recesses 13 and 14, and second,
`the bottom ends of positioners 23 and 24,
`which are provided with frictional engage-
`ment features similar to positioners 124.
`Since the positioners 23 and 24 have a
`circular cross-section and annular ends, the
`Jower annular ends of positioners 23 and 24
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`1 560 581
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`serve as retaining rings for diffuser elements
`31 and 32. The upper endsof positioners 23
`and 24 are arranged to provide for frictional
`engagement with the hollow cylindrical core
`elements 61. Thus, positioners 23 and 24
`serve a dual function; they retain diffusers
`31 and 32 in place while helping to properly
`position and hold filter elements 50 and 60.
`A peripheral sealing effect is provided by
`circular flanges 21, which are integral with
`base member11, and 121, which are integral
`with cover 100. The positioners 23 and 24,
`on the other hand, are removable to permit
`easy replacement of diffusers 31 and 32.
`Filter elements 50 and 60 are cylindrical
`and have hollow longitudinal, axial cores;
`the hollow cores being defined by serrated
`hollow cylindrical elements 61. The filtra-
`tion medium of filter elements 50 and 60
`consists essentially of a plurality of layers of
`synthetic organic polymeric fibers (e.g. fi-
`bers of a polyolefin such as polypropylene).
`Natural organic fibers (e.g. of the cellulosic
`or proteinaceous type) which can be biodeg-
`radable, are generally not used. The sedi-
`ment which becomes trapped in the filtra-
`tion medium during the use of the filtration
`device 10 is ordinarily adequate byitself to
`provide a nutrient medium for nitrifying
`microorganisms, and it
`is ordinarily un-
`necessary to include biodegradable fibers in
`the filtration medium.
`The fibrous structure in the filtration
`medium 51 can be woven or non-woven, but
`is preferably non-woven. In either event,
`interstices in the fibrous structure provide
`the pores ofthe filter medium. The porous
`structure is sufficiently interconnected to
`provide water permeability from the outer
`surfaces of the filters 50 and 60 to the inner
`cores defined by serrated cylindrical ele-
`ments 61. The pores extending from the
`outer surface to the inner core, regardless of
`whether
`they are tortuous or generally
`linear, can be assumed to have a width-like
`dimension analogous to the diameter of a
`cylinder. Thus, in the context of this inven-
`tion,
`the term ‘‘pore size” refers to the
`diameter or width of these generally cylin-
`drical or tortuous pores. In actual practice,
`it may be difficult to assign an accurate
`measurement to the “pore size” of filter
`elements 50 and 60. It is important that the
`pore size be relatively large, so that each
`filter element, when fresh and free from
`trapped sediment, will permit a water flow
`through the filtration medium of at
`least
`about 50 gallons per hour, preferably at
`least 60 or 70 galions per hour. Thus, two
`filter elements, when fresh. can provide a
`flow of filtered water out of openings 161
`which exceeds one hundredgallons per hour
`or even one hundred-thirty-five gallons per
`hour (About 380 L/hr or even 510 L./hr.).
`Commercially available air pumps can pro-
`
`vide sufficient air flow into inlets 15 and 16
`to induce this high flow rate. For example, a
`suitable type of air pumphas a highefficien-
`cy dual output design with about 3 watts of
`power or more. Surprisingly, the high flow
`rate does not disturb the fish in the tank.
`Regardless of the manner in which the
`“pore size” offilter elements 50 and 60 is
`measured,
`these filter elements are func-
`tionally equivalent to filters having a pore
`size well
`in excess of 10 microns, e.g.
`20-1,000 microns, less than about 500 mic-
`rons being generally preferred. To maintain
`the openness and high porosity of
`the
`filtration medium,
`fibrous layers 51 are
`interposed between windings 55 of reink-
`forcing strands or bands. These windings 55
`preferably comprise multifilament strands
`similar in structure to multifilament yarn or
`twine.
`Althougha high flow rate is achieved with
`the system as shown in Figures 1-3,
`the
`preferred embodiment of
`this invention
`includes air lift conduit 80 (Figure 6) which
`serves to increasethe flow rate as previously
`mentioned. Air lift conduit 80 fits into
`circular opening 161 andfrictionally engages
`with the interior of positioner 124, thereby
`extending the hollow longitudinal, axial
`core of hollow cylindrical element 61 and
`causing the purified water to be returned to
`the main body of water in the aquatic life
`support system by flowing through opening
`81 along with the flow of air.
`In the
`preferred embodiment air lift conduits are
`affixed in the circular openings above each
`filtration element.
`Although the air lift conduit feature of
`this invention is not bound by any theoryit
`is believed that for maximum efficiency of
`operation, the flow of water and air bubbles
`through the hollow core of the filter is
`preferably channelled upward into a non-
`porous conduit which speeds up the flow
`rate of the mass of water and dispersed air
`bubbles, resulting in faster drawing of water
`through the filter element into the hollow
`core.
`Although nitrifying microorganisms can
`be very effective in converting toxic dis-
`solved gases such as ammonia intorelatively
`harmless nitrate salts or fixed nitrogen, they
`may havelittle or no effect upon an increas-
`ing concentration of certain other gases such
`as carbon dioxide. As is known in the
`aquarium art, an increasing concentrationof
`carbon dioxide can shift the pH downward
`to the point where the acidity of the water
`can be a hazardto certain species of aquatic
`life, e.g. certain marine fish which are
`accustomed to a mildly alkaline pH. It is
`also knownin the art that particulate carbon
`(e.g. activated charcoal) can help to lower
`the carbon dioxide level in the aquarium
`water
`(e.g. by removing dioxide-forming
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`1 560 581
`SRO
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`U.S. Patent No. 3,957,634, andafiltration
`compounds). This technique can be advan-
`device 10 of this invention, which is attached
`tageously used in the context of this inven-
`to flow control plate 229. The tank 225 in
`tion. Thus,
`in the preferred embodiment
`Figure 5 is divided into an upper chamber
`shown in Figures 2 and 6, an activated
`and a lower chamber 223 by the aforemen-
`particulate elemental carbon bed 71, which
`tioned flow control plate 229, as in U.S.
`serves as an additionalfiltration medium,is
`Patent 3,722,685. Externalfilter system 211
`enclosed within a hollow cylindrical forami-
`is comprised of body 231 of
`the filter
`nous retaining means 73 which is in turn
`housing, a motor housing 221, a hanger
`enclosed within the hollow axial core of
`means 224 for engaging a side wall of tank
`filter element 60. A second carbonfiltration
`225: conduit 214 serving as an inlet means
`medium can be enclosed within a hollow
`and conduit 216 serving as an outlet means.
`core of filtration element 50,
`if desired,
`Asdescribed in detail in the aforementioned
`thoughthis generally appears to be unneces-
`U.S. Patent 3,722,685, contaminated water
`sary. The bedof carbon (i.e. some form of
`is drawn up through conduit 214 from below
`elemental carbon) is made easily insertable
`control plate 229, and filtered and purified
`and removable by means of the foraminous
`wateris returned to the lower chamber 223
`retaining means 73.
`underflow control plate 229 via conduit 216.
`Aswill be apparent from Figures 2 and 3,
`Filtration device 10 includes air lift conduit
`the reinforcing windings 55 provide filtra-
`means 80, air hose 5 and is supplied with air
`tion elements 50 and 60 with a high degree
`by air pump 241 through air hose 5. Filtra-
`of structural integrity. These filter elements
`tion device 10 can be used as a “back-up”
`can be handled very much like any other
`system for externalfilter system 211, and to
`replaceable parts. It must be remembered,
`increase thefiltration capacity of aquatic life
`however, that these elements 50 and 60,
`support system 210, and to eliminate “new
`unless they are pre-cultured (e.g. by soaking
`tank syndrome” by providing aquatic life
`in a nutrient medium followed by innocula-
`support system 210 with a fully cultured
`tion) are less effective when fresh. After a
`filter element when cultured filter elements
`period of use, however, proper culturing of
`in external filter system 211 are replaced
`the filter elements appears to be an inherent
`with fresh, uncultured elements.
`feature of this invention.
`In operation of the device in Figures 1 to
`The structure of removable and replace-
`4, an air pump (not shown)
`forces air
`ablefilter elements 50 and 60 is based upon
`through hoses or tubes or conduits 5 and 6
`commercially available filter elements such
`to air inlets 15 and 16. Air inlets 15 and 16,
`as the “Microwind” (trade designation of
`100
`along with air conduits 17 and 18 and
`the Cuno Division of AMF). Alternatively,
`35
`recesses 13 and 14 cooperate to provide an
`polyolefin multifilaments wound onarigid
`air directing means, the purpose of whichis
`hollow core element and having an effective
`to direct the air stream upwardto the hollow
`pore size above 10 microns, preferably at
`axial cores of filter elements 50 and 60
`least 50 microns can be used (e.g.
`the
`through diffuser elements 31 and 32, thus
`“Precision” filters made by Precision En-
`inducing a flow of water through openings
`gineering Company).
`103, then throughthe filtration medium 51
`Oneof the advantagesof the structure of
`of eachfiltration element, and then into the
`filtration device 10 is that it is suitable for
`holiow cores defined by cylindrical elements
`fabrication from a variety of inexpensive
`61. The bacterial cultures which build up in
`andeasily shaped materials which are biolo-
`thefiltration medium 51 convert toxic subst-
`gically inert or biologically compatible with
`ances such as ammonia to relatively less
`the water purification process taking place
`harmful materials such as nitrites, nitrates,
`in device 10. In the preferred embodiment
`or fixed nitrogen. The induced waterflow,
`of this invention, cover 100, base member
`having been substantially freed of ammonia
`11, air inlet means 15 and 16, conduit means
`and the like is then further purified in its
`17 and 18, positioners 23 and 24, cylindrical
`movement through activated elemental car-
`elements 61 and air lift conduit means80 are
`bon bed 71, and the purified water emerging
`all formed or molded from plastics (i.e.
`from opening81 in air lift conduit 80 (Figure
`synthetic thermoset or
`thermoplastic re-
`6) is biologically acceptable to even relative-
`sins), the preferred plastics being thermo-
`ly concentrated fish populations in marine
`plastic resins of the nitrile, styrene, olefin,
`or fresh water aquariums(filtration device
`or di-olefin families or copolymers (includ-
`10 is particularly well suited both for rela-
`ing terpolymers, etc.) thereof, e.g. acrylo-
`tively small home or hobby aquariums
`nitrile-butadiene-styrene.
`ranging from about 5 gallon capacity up to
`Figure 5 illustrates a complete aquaticlife
`about 50 or 60 gallon capacity and for larger
`support system 210 comprised of an aquatic
`aquariumsas well). If desired, the possibil-
`life support tank 225 containing water 227
`ity of excessive spray at the surface of the
`(which can be fresh water, sea water,
`body of water in the aquarium can be
`simulated sea water, or the like), an exter-
`reduced by placing a cap (not shown) over
`nal filter system 211 [such as described in
`
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`1 560 581
`
`opening 81 and providing openings(also not
`shown)near the upperend of conduit 80. At
`some point
`in the operation of filtration
`device 10, either of filter elements 50 or 60
`may become so clogged as to substantially
`reduce the overall water flow, e.g. the water
`flow may be reduced to 25 gallons per hour
`or less per filtration element or less than 50
`gallons per hour for the twofilter elements
`in combination. At this point in the opera-
`tion of the device, it is preferable to replace
`one of the two filtration elements. Thus,
`even if a fresh, uncultured filter elementis
`substituted for, say, filter element 50, filter
`element60 will continue to provide biologial
`filtering action,
`thus generally avoiding
`“new tank syndrome’. Since the flow of air
`and water
`through the filtration device
`follows a parallel arrangement,
`the flow
`through filter elements 50 and 60 will
`generally be apportioned according to an
`inverse relationship to the fluid flow resist-
`ance of the respective filtration medium 51.
`Thefresh filter elements will provide a high
`flow rate while the clogged or “dirty”
`element will provide biological filtering ac-
`tion. Although more waterwill flow through
`the fresh filter element, all of the water in
`the system will eventually be exposed to the
`beneficial biological action of the