GB2392152A - Liquid purification by floatation and filtration using a circulating liquid - Google Patents

Liquid purification by floatation and filtration using a circulating liquid Download PDF

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Publication number
GB2392152A
GB2392152A GB0327009A GB0327009A GB2392152A GB 2392152 A GB2392152 A GB 2392152A GB 0327009 A GB0327009 A GB 0327009A GB 0327009 A GB0327009 A GB 0327009A GB 2392152 A GB2392152 A GB 2392152A
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United Kingdom
Prior art keywords
liquid
filter
float
means
chamber
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GB0327009A
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GB0327009D0 (en
GB2392152B (en
Inventor
Peter Ignatius Swan
Richard Pierpont Moore
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Peter Ignatius Swan
Richard Pierpont Moore
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Priority to ZA9905192 priority Critical
Application filed by Peter Ignatius Swan, Richard Pierpont Moore filed Critical Peter Ignatius Swan
Priority to GB0019939A priority patent/GB2356860B/en
Publication of GB0327009D0 publication Critical patent/GB0327009D0/en
Publication of GB2392152A publication Critical patent/GB2392152A/en
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Publication of GB2392152B publication Critical patent/GB2392152B/en
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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B03SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03DFLOTATION; DIFFERENTIAL SEDIMENTATION
    • B03D1/00Flotation
    • B03D1/14Flotation machines
    • B03D1/1431Dissolved air flotation machines
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D21/00Separation of suspended solid particles from liquids by sedimentation
    • B01D21/0012Settling tanks making use of filters, e.g. by floating layers of particulate material
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B03SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03BSEPARATING SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS
    • B03B11/00Feed or discharge devices integral with washing or wet-separating equipment
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B03SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03BSEPARATING SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS
    • B03B13/00Control arrangements specially adapted for wet-separating apparatus or for dressing plant, using physical effects
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B03SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03DFLOTATION; DIFFERENTIAL SEDIMENTATION
    • B03D1/00Flotation
    • B03D1/02Froth-flotation processes
    • B03D1/028Control and monitoring of flotation processes; computer models therefor
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B03SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03DFLOTATION; DIFFERENTIAL SEDIMENTATION
    • B03D1/00Flotation
    • B03D1/14Flotation machines
    • B03D1/1412Flotation machines with baffles, e.g. at the wall for redirecting settling solids
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B03SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03DFLOTATION; DIFFERENTIAL SEDIMENTATION
    • B03D1/00Flotation
    • B03D1/14Flotation machines
    • B03D1/1443Feed or discharge mechanisms for flotation tanks
    • B03D1/1456Feed mechanisms for the slurry
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B03SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03DFLOTATION; DIFFERENTIAL SEDIMENTATION
    • B03D1/00Flotation
    • B03D1/14Flotation machines
    • B03D1/1443Feed or discharge mechanisms for flotation tanks
    • B03D1/1462Discharge mechanisms for the froth
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B03SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03DFLOTATION; DIFFERENTIAL SEDIMENTATION
    • B03D1/00Flotation
    • B03D1/14Flotation machines
    • B03D1/24Pneumatic
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/24Treatment of water, waste water, or sewage by flotation
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00Multistage treatment of water, waste water, or sewage
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B03SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03BSEPARATING SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS
    • B03B11/00Feed or discharge devices integral with washing or wet-separating equipment
    • B03B2011/006Scraper dischargers
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/001Processes for the treatment of water whereby the filtration technique is of importance
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/52Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2303/00Specific treatment goals
    • C02F2303/16Regeneration of sorbents, filters

Abstract

A coagulated liquid and an air saturated liquid are introduced near the bottom of a chamber 30. The bubbles that form when the pressure is released carry some impurities 10 to the surface 11. The liquid flows over a wall 35 and though a gravity particulate filter 2. Some of the purified liquid is saturated with air under pressure and then used for the floatation step. The liquid above the filter is held just below the top of a weir 12 leading into a channel 13, collects the floating material 10. The filter 2 can be backwashed. Preferably a reciprocating carriage 19 carries a pivoting blade 23 that moves the float material 10 towards the weir 12 in one direction and the surface 11 when it 19 returns. Details of the remotely controlled injection nozzle are also disclosed. The process can be used to purify water.

Description

1 23921 52

Hi., FLOTATION SYSTEM and ELEMENTS RELATIVE THERETO.

This invention relates to the system of removing impurities from a liquid by first causing them to be carried to its surface on fine gas bubbles and known as "OAF" or "dissolved air flotation" so named on account of the means to produce the fine gas bubbles that involves dissolving or solutionising the gas under pressure prior to its introduction and release into the liquid to be

processed. The invention specifically relates to different steps in the process including the means to dissolve the air into the pressurized liquid, the means to release the pressurised air saturated liquid into the liquid to be processed, the different means to remove the floated material and the means to connect a dissolved air flotation stage with a specific type of rapid gravity filter.

Referring first to the means to introduce the gas into the liquid; systems to effect this include the abstraction and pressurization of a percentage of the liquid to be processed, the introduction of gas under pressure to the said

percentage, its solutionising in a solutionising chamber and its return and release into the main body of the liquid.

The solutionising pressure chamber, in this instance according to this aspect of the invention, would be an elongated vertical cylindrical container with pressurised re-circulating liquid entering at the top and activating an eductor system that induces or assists the induction or aspiration of air into the center of an annular incoming jet that carries the aspirating air as well as air above the liquid, into the body of liquid in the container the level of which is maintained at the point for maximum induction, the system thus providing maximum contact between water and air under pressure to assist the dissolving action, recirculating and mixing both within the container before the saturated dissolved air liquid exits from the base of the container..

L S - 2

A major aspect of the invention relates to the means whereby a dissolved air flotation system is linked with a specific type of rapid gravity filter, namely a downflow rapid gravity filter in which the filter bed is located at a relatively high level, employs a relatively low backwash rate, has a controlled normal operating water level just below the crest level of the expended washwater receiving channel which channel extends across the whole of one side of the filter bed and may be common to adjoining filters since it is open and its outlet flow unisolated as is the case with Moore Airlift Rapid Gravity Filters with their typical structures such as an inlet channel on one side of the filter bed and a waste or expended backwash water channel on the opposite side of the filter bed separated there from by retaining walls again with a relatively shallow closely controlled normal operating liquid level a few centimetres below the crest of the expended washwater outlet, the normal operating water level being raised to backwash and employing the special filter washing techniques of Moore Filters which are ideally adapted to accommodate an adjoining "OAF" stage.

The invention provides for the linking of a specific design of filtration stage with a dissolved air flotation stage in which the actual flotation stage occurs in a primary channel adjacent to the filter bed with a common operating liquid level above the devision wall so that floated material from the flotation stage accumulates on the surface of the liquid and the effluent from the flotation stage flows over the devision wall in to the liquid above the triter bed that comprises particulate material suitable to remove filterable impurities that may remain in the effluent from the flotation stage. After passing downwards through the filtration stage the filtrate is collected by the underbed collection distribution system of the filter and delivered therefrom via outlet control to storage or use.

- 3 Removal of both floated material and expended backwashing liquid is effected into the waste channel adjoining the triter compartment located on the opposite side of the filter compartment to the flotation channel. In both cases the said channels extend across the full width of the adjoining filter compartment so that inflow to the flotation channel whilst removing floated material or backwashing the filter creates a cross current assisting the said operations.

Because operating liquid level above the filter bed is maintained just below the crest of the waste channel. This facilitates floated material or scum removal that may be required more frequently than filter backwashjng. It also facilitates and speeds up the backwashing process as will be shown later.

Regarding the removal of scum the invention includes a number of systems depending on operating conditions It is possible on account of the closeness of the operating water level to the crest of the waste channel that build up of floated material will cause it to automatically discharge over the crest.

Or discharge may be effected by periodically raising the water level; this may be automated by, for instance, suitable control of the filter outlet valve.

The movement of scum may be impeded by a tendency to adhere to the side walls and the invention includes means to break the adherence periodically as required. The invention also includes mechanically motivated scum wiping means.

According to this aspect of the invention, a floating material removal system

- 4 includes a flexible, scum wiping blade that transverses the width of the structure, is carried by a trolley system mounted on wheels, resting on opposite sides of the surround of the flotation structure, is guided by wheels or skids bearing against the side walls of the structure and is caused to reciprocate across the surface of the liquid and wipe the floated material into a receiving trough or channel; the wiper blade is mounted on a swivelling member that spans the structure, with bearing means whereby single central rope drive means from a central arm on the swivelling member, with stops that limit the swivelling action, causes the said member to rotate or swivel so that when travailing towards the scum removal trough, the blade engages the scum and when moving away from the trough, the blade is lifted above the scum by reverse pull of the rope drive As mentioned, the invention requires the top or normal operating water level above the filter to be accurately controlled, regardless of the build up of float and the invention includes means to do so accurately, utilising a Moore Diaphragm Valve or other specialist valve, controlling the filter outlet and paced by the filter top water level.

Since the filter top water level may have float build up interfering with top water level sensing, means to overcome this problem includes the provision of a separate float chamber with level communicating conduit to reflect the water level and the water level transmitted via a float with its vertical stem threading a liquid retaining tube piercing the floor of the float chamber to motivate a pilot valve controlling the Moore Diaphragm valve below or other means to pace the filter outlet valve in accordance with the required operating water level.

J - 5 Incoming liquid to be treated is delivered evenly across the bottom of the flotation channel where the said liquid is subjected to admixture with a percentage of air saturated liquid that on release creates a bloom of minute bubbles to effectively perform the flotation function. of ensnaring coagulated impurities and carrying these to the surface of the liquid..

The entrance to the flotation channel may take alternative forms but in all cases the incoming liquid to be processed, either enters or is directed initially to the bottom of the flotation channel where it has been or is about to be subjected to admixture with the percentage recirculated air saturated liquid.

The flotation process is dependent on the liquid to be processed having been dosed with a coagulant and the impurities in the liquid being captured by flocculent particles; preferably this occurs prior to the entry of the liquid into the flotation channel but the invention also provides for conditioning to occur in the actual flotation channel based on the prior administration of a quick acting coagulant and the provision of mixing or conditioning vanes in the Flotation channel the depth and volume of which could be increased.

In this regard Moore Airlift Filters with washwater storage below the filter bed lend themselves structurally to such a channel see Fig 4.

Fig 4 also shows media loss prevention means (45) a very important aspect in efficient filter bacloNashing and one that has received previous attention S.A.

patent No.82770 and U.S. patent No.4,478,726 (Moore) who also originated the provision of a sloping approach to the washwater outlet crest 12 now enhanced.

- 6 y An., The filter of the invention is equipped with means to effect backwashing of the filter bed including an underbed distribution system that includes means to evenly distribute air agitation of the filter bed, the necessary compressors or blowers, washwater motivation means, valves, piping and controls and may also use the special backwashing techniques applicable to Moore filter patents. For example In a preferred design of the filter this would embody the process described in South African Patent No.93/8195 whereby the backwash water supply is housed in a common compartment spanning a bank of hiters and the backwash flow is motivated therefrom by displacement with compressed air which may utilise the same blower that effects fitter bed agitation.

In other words the filter of the invention has the facilities to periodically cleanse the triter bed of collected impurities as required.

The special design of the washwater weir wall with an inclined section preceding the crest of the weir sill has been enhanced by the thickening of the rear of the wall and the top thereof to provide an increased width of slope and media loss prevention characteristic enabling special air water wash combination techniques.and the operating liquid depth above the filter applicable to the specialized flotation filter of the invention.

Coming to a very important aspect of the invention and of the flotation process generally, namely, the method of releasing pressurised dissolved air liquid into the body of liquid to be subject to flotation It is recognised that a shearing action at the point of release is advantageous and that the sizing of the release aperture is critical in maintaining pressure and in releasing the correct amount of dissolved air liquid.

I To this end it is advantageous to provide control and adjustment of the said aperture. Further in order to spread the effectiveness of introducing the pressurised dissolved air liquid into the body of liquid to be subject to flotation, it can as is the case in the present invention, be most advantageous to have a number of I release points.

Since the provision of a number of release points reduces the individual size of each and since the orifices of such points may have relatively narrow openings, the invention includes means to remotely adjust, to periodically clear, or in a further step to automatically clear such blockages.

Further it is important that the correct pressure is maintained in the pressurized air solutionizing process of dissolved air flotation and as mentioned this is a function of the said release poinVs.! In a very important aspect of the invention preset pressure of the air solutionising system is automatically maintained regardless of variations of flow in the system. This is achieved by controlling the opening of the said release poinVs of the system by having a closure member of the said release points motivated by the pressure of the pressurized air solutionizing system such that any reduction in the pressure of the said system causes closure of the release points and vice versa for increases in pressure resulting in automatic preset pressure restoration.

In its simplest form the pressure is preset, in a further form the preset pressure is adjustable and in a still further form it is remotely adjustable.

- 8 An automatic preset pressure form of the invention comprises a diaphragm having connected to its one face motivating means to vary the opening of the release point/e of the pressurised air solutionising system to which pressure the same face of the diaphragm is also subject, with the opposite face of which diaphragm being subject to the required preset force or pressure' the preset pressure being elastic in that it permits movement of the diaphragm to control the opening of the release points to restore the preset pressure that would otherwise vary with fluctuations in flow.

The elastic preset pressure to which said opposite face of the diaphragm is subject may be provided by various means. It may be provided by a spring in combination with the body of liquid into which the pressurised air saturated liquid is released or in combination with the pressure of the air in which latter event the said opposite face of the diaphragm would face an enclosed compartment, connected to atmosphere; alternatively preset compressed air pressure connected to the said enclosed compartment without the spring will perform the required function or again reduced pressure drawn from the pressurised air saturated liquid itself and connected to the said enclosed compartment in combination with a spring.

The invention includes means to adjust the automatically maintained preset pressure setting - in its simplest form by adjusting a fixed initial setting by changing the strength of the said spring or by providing means to adjust the tension thereof - or by providing means to adjust the preset pressure in the said compartment or compartments, which means facilitates adjustment by remote control.

- 9 - A simple form of the invention comprises a tubular manifold that distributes and releases pressurised air saturated liquid into the body of liquid to be subject to flotation via a number of release apertures the degree of opening of which depends on the position of matching apertures on a sliding sleeve within the said manifold which sleeve is mechanically linked either to manual means to adjust its position and consequently the preset pressure or to the said mechanically linked diaphragm that may then jointly control all the release points in accordance with the above described functions. In the latter event all the said release points are jointly controlled by the preset pressure in a single diaphragm compartment.

In another form of the invention the manifold that distributes pressurised air saturated liquid may be connected to a number of individual release points, each release point being fitted with its own individual diaphragm motivation, so that the preset pressure of each release point may be individually or jointly set or controlled or remotely set by a single preset pressure source connected to the said compartments.

To summarise this aspect of the invention includes several means to remotely preset or automatically control the aperture/s of the release point/e and the pressure of the said pressurised air saturated liquid.

-10 ILLUSTRATEC) EXAMPLES OF THE INVENTION AND RELATED

ELEMENTS

Fig. 1 illustrates in vertical cross-section a structure 1, with a flotation system in channel 30 and a particulate filter bed 2, in an adjoining compartment with a common liquid level 11 above the devision wall 35 where floating material or scum 10 accumulates and in this Fig is shown being removed by reciprocating scum wiping system 19 into channel 13 that also serves to receive expended wash water from the filter.

In Fig 1, 8 is a conduit supplying liquid to be treated via valve 7 into dispersion header 4 that is shown enclosing dispersion header 6M that receives pressurised air saturated liquid and releases this through remotely controlled release orifices along the length of header 6M through corresponding orifices in dispersion header 4 (see enlarged Fig 8 that also shows alternative individual, jointly controlled, release orifice units for spreading the delivery of the said air saturated liquid across the length of the base of channel 30 and its intimate admixture with incoming liquid),. Fig 7 shows a still further alternative inlet and mixing arrangement for channel 30, possibly the most important step in the efficiency of the whole process. (Figs 9, 10 and 11 illustrate enlarged detail of the release nozzles of the invention.) For the flotation action to be initiated at this stage it is assumed that the entering liquid to be purified has been coagulated but in any case a quick acting coagulant or coagulant aid may be administered at 31 and baffles at 5 in channel 30 assist the coagulation process as well as the contact between liquid and micro bubbles. The impurities captured by the micro bubbles rise to the surface of the liquid and the effluent from the flotation process flows over the top 35 of the devision wall into the body of liquid 33 above the top 9 of the filter bed. The liquid may then pass through filter bed 2 into filter distribution

- 1 1 and collecting system 3 and out of the filter via duct 47 and outlet valve 16 paced by the water level 11, accurately controlled within close limits via level communication pipe 14, stilling box 15 and water level transmission unit 18.

When required for backwashing a filter bed air agitating supply is admitted via valve 34 and backwash water via valve 17. Before backwashing, scum wiper system 19 may be activated or, if the scum is first freed of adherence to the side walls the level 11 of the liquid above the filter may be raised to discharge scum or floated accumulation 10 over weir lip 12 using incoming liquid from channel 30 to create a cross current.

Fig. 4 illustrates in cross-section a preferred embodiment of the invention in which a Type 3 Moore Airlift Rapid Gravity Filter is combined with a flotation process step.

The identifying numbers of Fig. 1 above relate to similar functions and parts of the filter of Fig.4 except that a mechanical scum removal system has not been illustrated. Additional components include a common washwater storage compartment 44 beneath the filter, that contains filtered water from the filtration stage and that can serve additional filter units, and from which, when backwashing, backwash water is displaced by compressed air, (connections not shown). The unit of Fig 4 illustrates a single or multiple weir type inlet 43, with isolator 7, that discharges behind inlet flow deflector 48 delivering across the bottom of inleVreaction channel 30 where it is subject to admixture with air saturated liquid from release points on compressed air saturated liquid manifold 6M against deflecting shroud 42. Enlarged detail and description in

Fig 7 As before the effluent from the flotation channel flows over the enlarged top of the wall 35 that devices the flotation channel 30, from the filter bed 2, provides a velocity controlled smooth inlet to the filter chamber, and when bac Washing

by - 12 deflects rising backwash water advantageously, Due to its width and shape the top of wall 35 also precludes media entering the inlet channel during air agitation of the filter; any media coming to rest thereon is resumed to the filter bed by incoming flow.

The widening of the top of the washwater weir wall at 45 provides increased slope distance to the slope 46 that inhibits the loss of media during backwashing. In all inlet arrangements it is necessary that the liquid to be treated enters or is directed to and spread across the base of the flotation channel 30, that it is efficiently mixed with air saturated liquid at a low level in this channel and that the channel has sufficient depth. Further for maximum efficiency the liquid to be treated should be adequately coagulated and preconditioned, although the invention does provide for some conditioning in the flotation channel.

Figs. 7 is an enlarged cross sectional elevation of a preferred type of inlet arrangement with a drowned inlet weir 43 (to deter floe break up) discharging behind deflecting plate 48 that spreads the incoming flow along the floor 51 of the flotation channel but which has in this instance, a shaped discharge end that acts as a shroud to deflect the multiple issuing jets from the release points of the pressurised air saturated liquid manifold 6M to just above the incoming liquid. Even preferable, the multiple individual orifice release system of the invention located just above the incoming liquid.

In all preferred cases the pressurized air saturated liquid with remotely adjustable multiple discharge points delivers across the whole length of the flotation channel.

d9 -13 Fig 8 indicates an enlarged detail of the inlet shown in Fig 1 with air saturated liquid manifold 6M (of the type illustrated in Figs 9 or 10) located inside inlet manifold 4 with the remote controlled multiple jets of its release points, surrounded by the discharge orifices of the inlet manifold, directed downwards for dispersion against the floor 51 of the flotation channel 30.

Fig 8 further illustrates an alternative system for the release of the pressurised air saturated liquid with the multiple deployment of individual release orifices of the type illustrated in Fig 11 arranged across channel 30 with air saturated liquid header 6M located outside the channel as well as preset compressed air header 90, the pressure of which jointly controls all the release orifices.

Figs 9, 10 and 11 relate to the means to release the pressurized air saturated liquid in "Dissolved Air Flotation't and illustrate in cross section, examples of this important aspect of the invention, namely the means to control a release orifice and jointly control a number of release orifices.

Fig g illustrates a manually remote controlled manifold 6M that receives the pressurised air saturated liquid for dispersion and release via orifices 54 the openings of which may be jointly manually controlled and set by hand lever 62, magnified movement scale 6D, lock 61 and lever extension 59 that motivates an inner sliding sleeve 56, with orifices 55, corresponding with orifices 54 in manifold 6M such that the movement of orifices 55 controls the degree of opening of orifices 54. 58 is the fulcrum of lever 59 and 64 the linkage point that transmits movement to sleeve 56 via rod 65 and gland 63.

Lever 59 may extend to above the water line and the throttled orifice setting be readily adjusted or orifice blockage cleared by the momentary opening of release orifices 55 at any time.

- 14 The movement of sleeve 56 may be electrically, hydraulically or otherwise power motivated to be remotely controlled or be automated for instance to have orifice blockage cleared automatically when triggered by rise in pressure in manifold 6M or of the pressurised air saturated liquid.

In a further important inventive step of the dissolved air flotation process where a percentage of the liquid to be processed is pressurized to be saturated with air, it is important that the designated percentage be maintained regardless of variations in flow and that the designated air solutionising pressure be maintained in the air saturating system and the invention includes means to control the said release orifice/s of the pressurised air saturated liquid to fulfil this requirement.

Examples of such means are illustrated in figs 10 and 1 1 Fig 10 illustrates a multiple release orifice system similar to that of Fig 9 except that in this instance the release orifices 54 in the manifold 6M discharge vertically against shroud 42 (with positional locating pins 82 and light retaining springs 81) and the sliding orifice aperture control member 56 is motivated, via rod 65, by the differential forces on diaphragm 57 resulting from the pressure from the manifold 6M on one face of the diaphragm and the opposing preset force of spring 66 together with the pressure (or absence thereof on the opposite face of the diaphragm in compartment 79, to automatically maintain the preset pressure in manifold 6M and incidentally in the air saturating system by regulating the degree of opening of release orifices 54 to restore or correct any variation from the preset pressure.

The setting of the said preset pressure may be altered by changing the spring 66, by adjusting the strength of spring 66, by spring tensioning screw 80, or by altering the back pressure in compartment 79.

-15 The back pressure in compartment 79 may be static with connection 91 open to the liquid in which the manifold 6M is immersed or open to atmosphere via a conduit connected to 91, the preset force being provided by spring 66.

Alternatively in another aspect of the invention the spring may be replaced by a supply of compressed air, 89, connected via conduit 90 to compartment 79 the preset pressure of which may be remotely set or adjusted by pressure reducing valve 87 and needle bleed valve 85 and indicated on pressure gauge 86. In addition to automatically maintaining the preset pressure in manifold 6M and the air saturating system' partial blockage of the release orifices would be automatically compensated for by their degree of opening, also may be automatically periodically opened and flushed by the release of pressure in compartment 79 for example by solenoid valve branching off connecting conduit 90.

Fig 11 is a primary example of this latter aspect of the invention applicable to friction free control of individual release points where each release point orifice 54 is individually controlled by orifice closure member 55, motivated by diaphragm 57 via connecting rod 65 in accordance with the opposing forces applied to each side of the diaphragm 57 and resulting from the pressure in the manifold 6M, applicable to the upper face of the diaphragm via connection 6B, and the opposing preset force resulting from spring 66 and or the pressure in compartment 79 applied to the opposite side of the diaphragm which pressure could be from the liquid in which the unit is functioning or from a source of compressed air as previously described.

In a further feature of the invention where no compressed air source is available the preset pressure may be remotely set by utilising the pressure in manifold 6M via connection 6A isolating valve 83 strainer 84 throttling needle valve 85 preset pressure indicating gauge 86 and pressure regulating release

- 16 -

valve 87 with bleed discharge 88, the preset pressure being conveyed via branch conduit 92 and connection 91 to compartment 79 where it is operative in conjunction with spring 66 on the opposing side of the diaphragm to automatically maintain the preset pressure of the air saturated compressed air system. In the ideal multi release point dispersion of the air saturated liquid' the individual release point example of Fig 11 may be duplicated any number of times along manifold 6M fed by branch connections 6B in which case the preset pressure of the individual release points may be jointly set by a single preset pressure setting system commonly connected to each.

The example of Fig 11 is illustrated as part of a jointly remotely controlled multi release point system however the unit may operate singly to control release of the full pressurised saturated air liquid supply connected directly to the unit with all the remote control benefits of the invention..

The earlier description of fig 1 omitted a description of the mechanical scum

removal system of the invention illustrated in Figs 1,2 and 3. In this system a movable trolley 19, mounted on wheels 25, that rest on the filter surround 29, with side guide wheels or skids 26, reciprocates to and fro across the structure, wiping scum or collected floating material 10 over lip 12 into the scum removal channel 13 The scum skimming trolley 19 is motivate by rope drive 20 (driven by geared motor drive means 21) that motivates the trolley via arm 22 on swivelling sleeve 27 that in turncarries scum blade 23 to depend into liquid surface 11 when travailing towards lip 12 and propel scum thereto and to swivel clear of liquid level 1 1 when the scum has been wiped over 12 and automatic reversing rope drive 20 pulls over arm 22 and causes trolley 19 to reverse and

- 17 travel away from lip 12.

Whereas Fig. 1 illustrates the trolley structure in cross section elevation, Fig. 3 and 2 have been prepared to indicate the trolley structure in plan and end elevation and in these Figs., 25 are four support wheels operative an structure surround 29 with guide wheels 26 operative against the side of the structure 29. 40 are cross- members that carry the wheels and column 28 that spans the structure and threads swivelling collars 27 and 27a from which flexible scum wiper blade 23 depends and to which swivelling drive arm 22 is attached. The swivelling action of the scum blade that engages the scum in forward motion and is lifted clear in reverse motion is a special feature of the invention and Figs. 5 and 6 have been prepared in enlarged cross-section to indicate in Fig. 5 the position of the blade in forward motion and in Fig. 6 its position when the trolley is reversing and the change over action caused by the pull of the rope drive in forward motion Fig. 5 and reverse Fig. 6, the collar 27 swivelling about column 28 until reaching stops 41, attached to column 28 and transferring drive to the trolley. 39 are weights to assist in ensuring positive swivelled position and the trolley may have initial inertia or friction means to ensure swivel change over before commencing to travel.

In the above arrangement column 28 is fixed to the trolleys. In the alternative arrangement column 28 (with wiper 23 and drive arm 22 attached) swivels in end bearings mounted on the trolleys which are joined by two fixed cross-members from which stops 41 are mounted.

With regard to the pressurised air solutionising process of the invention, that relates to the percentage liquid that is circulated to produce pressurised dissolved air, Fig. 12 indicates in vertical section an air dissolving system

- 18- comprising enclosed pressurized container 68, with an incoming delivery, 75 for circulating liquid under pressure that feeds a velocity accelerating approach cone 69 to an eductor, 78, that produces an annular jet and induces air via central air inlet tube 70 and carries this to the base of the said container from where it is dispersed and deflected by circular baffle 77 back up into the body of liquid, the top water level of the body of liquid in the container being maintained at optimum by a float valve, 72 that vents excess air via exhaust pipe 71. Air exhaust valve 72 is mounted on an arm with fulcrum at 73 and is motivated by float 74 responsive to the level of the liquid in the said container and providing leverage to motivate air exhaust valve 72.

Depending on the relative delivery pressure applied to the incoming circulating liquid 75 in relation to the pressure maintained in container 68, eductor 78 would be capable of inducing an excess of air over and above that which can be dissolved in the circulating liquid with the excess vented by air exhaust valve 72 and the level of liquid in container 68 automatically maintained at the required level.

The air solutionising system can operate alternatively by pressurising the incoming air supply 70 so that the pressure differential necessary to drive eductor 78 is less but even in these circumstances a pressure differential should be maintained to provide the annular jet that carries the incoming air to the bottom of container 68 and contributes to the air solutionising efficiency of the system.

The outer periphery of the annular jet further induces air from above the liquid in the container carrying this also in the form of fine bubbles into the body of liquid in the container to again assist the solutionising efficiency of the system.

Circulating liquid containing dissolved air exits from behind the bame 77

- 19 in the base of the container at 76.

The system requires that the quantity of air entering the pressurised container 68 to be in excess but only slightly in excess of that which can be solutionised in the circulating liquid.! I,

Claims (12)

Jo DIVISIONAL PATENT APPLICATION FROM ORIGINAL U. K. PATENT APPLICATION GB 2356 860 A SAME APPI ICANTS AND INVENTORS PETER IGNATIUS SWAN AND RICHARD PIERPONT MOORE TITLE: FLOTATION FILTRATION FOR NOW THE SPECIFICATION REMAINS UNCHANGED BUT THE CLAIMS ARE CHANGED. CLAIMS
1. A method of purifying a liquid that combines:- coagulating the liquid, introducing the coagulated liquid evenly into an elongated chamber at a low level of the chamber, causing the liquid to mix with a released recirculated portion of the subsequently purified liquid which portion contained dissolved air saturated under pressure, causing impurities to attach to the resulting micro bubbles and to rise to the surface of the liquid, causing the liquid to flow over an opening between the surface of the liquid and the top of a dividing wall between the said elongated chamber and a chamber containing a rapir' gravity particulate filter, causing the liquid to flow through the filter, be collected by the under bed reticulation system of the filter, be delivered therefrom via a filtered water outlet controller paced by the water level in the filter to maintain the water level in the filter just below the level of the weir crest of a channel extending along the opposite side of the filter chamber to the filter inlet and the purpose of which channel is to periodically receive floating impurities that accumulate on the surface of the liquid above the filter that have special means to induce the float thereto and which channel also receives expended filter backwash water as required during the backwashing |
of the filter with means to prevent the loss of filter media during the backwashing procedure (that may also include agitating the filter media with compressed air).
2. A method of purifying a liquid according to claim 1 in which the media loss prevention means is comprised by a sloping approach to the crest of the division wall between the filter chamber and the expended washwater receiving channel augmented by increased thickening of the division wall or the thickening of the top of the wall to accommodate increased amount of slope over and above what would be applicable from the thickness of applicable walls in normal civil structure.
3. A method of media loss prevention as claimed in claim 2 in which the increased slope to the crest of the said division wall is provided by the provision of an angled plate attached to the division wall, that may also be shaped to provide beach means accommodating the expulsion of float.
4. '- A method of purifying a liquid as claimed in claim 1 in which the top of the said dividing wall between the said elongated chamber and the said filter chamber is widened so that when backwashing the filter, filter media is retained thereon and cannot reach the said elongated chamber and is subsequently carried book into the fiber chamber by the inlet flow.
5. A method of purifying a liquid as claimed in claim 1 in which the method of introducing the said coagulated liquid evenly at a low level throughout the
length of the said elongated chamber comprises the provision of a baffle or baffle wall behind which the coagulated liquid is initially introduced and below which the coagulated liquid flows into the said elongated chamber.
6. A method as claimed in claim 5 in which the method by which the said coagulated liquid is initially introduced is by means of a weir or drowned weir or weirs behind the said baffle that may constitute similar inlets to parallel purification units to equally divide the overall flow thereto.
7. A method of purifying a liquid as claimed in claim 1 for removing accumulated float in which a carriage bearing float wiping means attached to an arm or arms depending from swivelling means, is caused to reciprocate over the float area by rope drive means attached to an opposite arm of the swivelling means such that when the carriage is being driven by the said swivelling drive arm towards the float exit means, the float wiper has swivelled to engage the float and when travailing in the opposite direction away from the float exit means, by reason of the pull of the drive rope in that direction the float wiper means is caused to swivel free of the float.,,
8. A method of removing accumulated float from dissolved air purification systems as claimed in claim 7 in which the reciprocating carriage that carries float wiper means, also carries means to sever the a4,hesion of accumulated float to the side walls.
9. A method of removing accumulated float from dissolved air purification systems as claimed in claim 8 in which the float removal operation is intermittent and on initiation, the means of severing the float from the side walls is operative during the initial reciprocation of the carriage which is in reverse so that on the following forward float wiping removal stroke the accumulated float has been freed from adhesion to the side walls.
A method of purifying a liquid according to claim 1 in which the compressed air source that is used to agitate the filter media is also used to motivate the back washwater flow to the filter by displacing filtered water from the said filter, stored in an airtight chamber beneath the filter chamber and which said airtight chamber is adjoined by the lower portion of the said elongated chamber into which the said coagulated liquid is introduced and whereby the depth of the said elongated chamber is increased in an economic structure.
11. A method of purifying a liquid as claimed in claim 1 in which the operating liquid level in the container in which the said liquid is being purified is accurately maintained below the crest of the waste channel.
1 1
12. In which the means to accurately control the required liquid level of claim 11 is by transferring the level of the liquid to a separate liquid container via an interconnecting conduit that communicates with the said liquid below the surface so that the liquid in the said separate container is scum or float free and it's surface available to be accurately sensed for transmittal to motivate liquid level control means.
GB0327009A 1999-08-16 2000-08-15 Flotation filtration Expired - Fee Related GB2392152B (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
ZA9905192 1999-08-16
GB0019939A GB2356860B (en) 1999-08-16 2000-08-15 Flotation system and elements relative thereto

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Cited By (6)

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Publication number Priority date Publication date Assignee Title
WO2006106411A1 (en) * 2005-04-07 2006-10-12 Idrosistem Energy S.R.L. Apparatus for treatment of a polluted liquid, particularly for treatment of pulluted water from production residues of non-woven fabric
CN100422099C (en) 2004-05-11 2008-10-01 海南欣龙无纺股份有限公司 Treatment method for water jetting non-woven processing water
CN101066814B (en) 2007-06-08 2010-05-19 东华大学;绍兴县和中合纤有限公司 Water treating process and apparatus for cellulose fiber hydro-entangling process
ITBO20100511A1 (en) * 2010-08-05 2012-02-06 Wam Spa Apparatus for the removal of floating polluting elements from a liquid surface
EP2690070A1 (en) * 2011-03-25 2014-01-29 Doosan Heavy Industries & Construction Co., Ltd. Dissolved-air flotation-type pretreatment apparatus
CN106396156A (en) * 2016-11-15 2017-02-15 扬州兄弟环境保护设备工程有限公司 Deep oxygen dissolution integrated machine

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GB1582650A (en) * 1977-07-13 1981-01-14 Paterson Candy Int Flotation clarification process
GB2105601A (en) * 1981-09-15 1983-03-30 Lenox Inst Res Apparatus and method for clarification of water using combined flotation and filtration processes
JPH01242187A (en) * 1988-03-24 1989-09-27 Fuso Kensetsu Kogyo Kk Treatment of aqueous suspension in single tank and equipment therefor
US5591347A (en) * 1995-05-26 1997-01-07 Unicel, Inc. Single cell gas flotation separator with filter media

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1582650A (en) * 1977-07-13 1981-01-14 Paterson Candy Int Flotation clarification process
GB2105601A (en) * 1981-09-15 1983-03-30 Lenox Inst Res Apparatus and method for clarification of water using combined flotation and filtration processes
JPH01242187A (en) * 1988-03-24 1989-09-27 Fuso Kensetsu Kogyo Kk Treatment of aqueous suspension in single tank and equipment therefor
US5591347A (en) * 1995-05-26 1997-01-07 Unicel, Inc. Single cell gas flotation separator with filter media

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100422099C (en) 2004-05-11 2008-10-01 海南欣龙无纺股份有限公司 Treatment method for water jetting non-woven processing water
WO2006106411A1 (en) * 2005-04-07 2006-10-12 Idrosistem Energy S.R.L. Apparatus for treatment of a polluted liquid, particularly for treatment of pulluted water from production residues of non-woven fabric
CN101066814B (en) 2007-06-08 2010-05-19 东华大学;绍兴县和中合纤有限公司 Water treating process and apparatus for cellulose fiber hydro-entangling process
ITBO20100511A1 (en) * 2010-08-05 2012-02-06 Wam Spa Apparatus for the removal of floating polluting elements from a liquid surface
WO2012017422A3 (en) * 2010-08-05 2012-03-29 Wam Industriale S.P.A. Apparatus for removing floating pollutant elements from a liquid surface
EP2690070A1 (en) * 2011-03-25 2014-01-29 Doosan Heavy Industries & Construction Co., Ltd. Dissolved-air flotation-type pretreatment apparatus
EP2690070A4 (en) * 2011-03-25 2014-08-13 Doosan Heavy Ind & Constr Dissolved-air flotation-type pretreatment apparatus
US9440864B2 (en) 2011-03-25 2016-09-13 Doosan Heavy Industries & Construction Co., Ltd. Dissolved air flotation-type pretreatment apparatus
CN106396156A (en) * 2016-11-15 2017-02-15 扬州兄弟环境保护设备工程有限公司 Deep oxygen dissolution integrated machine

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GB0327009D0 (en) 2003-12-24

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