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USRE22701E - Liquid clarification - Google Patents

Liquid clarification Download PDF


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USRE22701E US22701DE USRE22701E US RE22701 E USRE22701 E US RE22701E US 22701D E US22701D E US 22701DE US RE22701 E USRE22701 E US RE22701E
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    • B01D21/00Separation of suspended solid particles from liquids by sedimentation
    • B01D21/0018Separation of suspended solid particles from liquids by sedimentation provided with a pump mounted in or on a settling tank
    • B01D21/00Separation of suspended solid particles from liquids by sedimentation
    • B01D21/0039Settling tanks provided with contact surfaces, e.g. baffles, particles
    • B01D21/0042Baffles or guide plates
    • B01D21/00Separation of suspended solid particles from liquids by sedimentation
    • B01D21/10Settling tanks with multiple outlets for the separated liquids
    • B01D21/12Settling tanks with multiple outlets for the separated liquids with moving scrapers
    • B01D21/14Settling tanks with multiple outlets for the separated liquids with moving scrapers with rotating scrapers
    • B01D21/00Separation of suspended solid particles from liquids by sedimentation
    • B01D21/24Feed or discharge mechanisms for settling tanks
    • B01D21/00Separation of suspended solid particles from liquids by sedimentation
    • B01D21/24Feed or discharge mechanisms for settling tanks
    • B01D21/2427The feed or discharge opening located at a distant position from the side walls
    • B01D21/00Separation of suspended solid particles from liquids by sedimentation
    • B01D21/24Feed or discharge mechanisms for settling tanks
    • B01D21/2433Discharge mechanisms for floating particles
    • B01D21/2438Discharge mechanisms for floating particles provided with scrapers on the liquid surface for removing floating particles


2 Sheets-$11861; l

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`E. M. 'KELLYA Erm.

LIQUID GLARIFICATION Griginal Filed June 2l, 1941 Dec. 4, 1945.

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-lnri'ginal Filed .Jun-e' 21, 1941 2 Sheets-Sheet 2 Num :.Qvfa/ y v04m,... L w Y c u 0 x mi .imm NMPP?. A /v/ ard 5PZ rf inw@ RUM .Q

Reuma Dee. 4, i945 y 22,701 n LIQUID cLAmFrcA'rIoN Earl M. Kelly and 4Arthur M. Kivarl, Los Angeles,

, Calif., Robert P.

Kite, Larchmont, N.

Elliott J. Roberts, Westport, Conn., and David B. Sutherland, Montclair, N. J., assignors to The` Dorr Company, a corporation of Delaware Original No. 2,324,400, dated July 13, 1943, Serial.v No. 399458, June 21, 1941. Application for reissue August 28, 1945, Serial No. 613,122

13 Claims.

This invention relates to the clarification or purification of liquids and especially those that are impure or polluted such as sewage, trade and vdairy wastes, packing and cannery wastes, oil

renery wastes, and the like 'that are character-- ized in that some constituents/thereof must be removed from the water before it can be either re-used or released into water-courses like rivers and streams, or into the'ocean.

Such constituents may comprise any particles of turbidity that interfere with the clarity of the water and also particles of matter of organic origin which is not removed from the water would cause its pollution. Such constituents, in general, exist in the waste waters in the form of suspended matter whose settleability ranges from normally readily settleable solids such as grit, up through varying degrees of .normally semi-iloatability and difficult settleability to colloids and oil or grease that are normally nonsettleable.

So one object of this invention'is to devise an improved method and apparatus for the efllcient removal by reduced pressure flotation of iloatable or suspended matter from liquids that contain them. Such liquids are well exemplified by sewage. Sewage is treated usually by inowing it is another object of this invention tovdevise equipment for the clariilcation thereof that isl covered whereby the liquid being treated is maintained out of view. V

-A still further object of this invention is to cause certain normally non-iloatable suspended solids to be floated with a concurrent improvement in settling the non-floatable and normally settleable suspended solids.

20 ed is sub-atmospheric, namely, under the effect The invention is preferably embodied in equipment wherein the polluted liquid has gas dii-l fused therein, called hereafter gassed liquid; 'the gassed liquid is conducted' to, 'and released in proximity to the surface of. a body of liquid being treated, on the surface of which liquid there is effective a pressure that is less than that on the gassedliquid. Normallythe gassed liquid is supplied under atmospheric pressure while the pressure on the surface of the liquid being treat- A of vacuum. Moving means are provided for skimming floated matter, including scum, foam,'oil or grease, into an arrangement that includes a dam over which the floatingy matter is removed g5 from the zone of treatment of the liquid.

Important in such an arrangement is the control for maintaining of a constantliquid level it to relatively large settling basins often called sedimentation tanks or clariilers. Sewage is held in them in quiescence so that those suspended solids that will settle, do settle and deposit on the bottom ot the clarier as sediment. Mechanical means are. usually provided for raking the sediment from the tankv bottom to discharge. These clariers have the'slze controlled by the overflow rate and detention time necessitated by the settling rates of the suspended solids .to be settled. This makes these clarier tanks relatively large, in some cases a hundred or more feetin diameter. Some of the suspended material is iloatable, which tends to rise to the surface of the liquid in the clarifier and form into a disagreeable scum. The skimming or such tanks has presented a serious mechanical problem.

Therefore another object of this invention is to devise equipment that will remove settleable matter from polluted liquids rapidly and without the necessity of the usual long detention perind, whereby the equipment can be made substantlally smaller. And a further object is to arrange such equipment so it will also remove for the body of liquid being treated, and preferably it should be adjustable. In the preferred embodiment of this invention, this is accomplished by maintaining in what may be called a control box, a relatively small or minor body of liquid being treated apart from the main body so esto be substantially -free from scum or floating solids but in hydraulic communication therewith at the bottom portion while in gaseous com'- munication at its top .portion with the gaseous but reduced pressure atmosphere overlying the f liquid being treated.

noatable matter as scum about as fast as accumulated on of theliquid.

Sewage and the like polluted liquids are usu- 'ally either unsightly or odorlferous, 'or both, so

`'Another characteristic oi' this invention is that associated with the .minor or auxiliary body of liquid in the control bbx,l there are suction-applying means primarily for applying the effect of vacuum to the main body oi liquid which'automatically lcease applying lsuction when excess liquid accumulates above the desired liquid level. These means are exemplied by a suction pipe' orunozzle connected' to a` wet vacuum pump. and the .pipe may also be pivotally adjustable for controlling the height of vthe controlled liquid level.V Clarined or treated liquid is removed fromthe equipment in quantity equal to the liquid incoming thereto for treatment, so the machine is continuous in operation. Also, the clariiled liquid that is removed, is .derived-from a zone ot materially lessened elect of 'vacuum and also from a place whereat the withdrawn liquid is shielded from descending of settling solids.

The sequential gassing and vacuum, or reduced pressure, treatment seems to cause not only the normally oatable matter but importantly a substantial quantity of normally non-fioatable and normally diilicultly settleable suspended solids, as

well as semi-heating solids, to rise or to be buoyed to the liquid surface from whence they are removed by the skimming means. Other suspended solids seem to have their settleability increased, so that as a. result of the vacuum treatment, solids from some liquids settle to the bottom of the tank and deposit as sediment, whereupon they are independently removed. When treating some liquids, the clarified liquid can be removed from the tank through the vacuum suction pipe, while in treating other liquids, it may be desirable to remove the treated liquid from another zone or zones of the tank.

Since it has been found that the vacuum is ef-A fective to the maximum to float suspended solids substantially only when they are exposed to the vacuum elects at the liquid surface, it is important that thevelocity of the suspended solids fed to the machine shall be such that solids reach the region of the liquid surface of the body of liquid being treated. To this end, the liquid to be treated is' preferably supplied to the tank by means of a draft tube that is so calibrated and so shaped that the suspended solids in the feed passing up` through the draft-tube are emitted therefrom into that zone in which the vacuum becomes effective on them. The design and shape of the draft-tube should be such as to give a velocity of the feed liquid up the draft-tube so that there is discouraged any dropping back down in the draft-tube of settling solids because oncethey start downwardly, the pull of the vacuum is not very strong on them. At the same time.

` this is that it causes the bubbles. buoying up the floated solids to be shaken loose therefrom, whereupon those solids descend and thus escape being is best. Therefore, that latter ngure is recommended. It takes 13:6 inche'sof water to equal one inch of mercury. Therefore, in order to I have at least some degree of vacuum effective on all the liquid in the tank. except of course that' .v on the bottom thereof, the tank should be of 65 the order of 9 x 13.6 inches indepth, or roughly 10 feet. In such a tank,while there is vacuum equal to about 9 inches of mercury effective on the liquid level in the tank, at one foot below the liquid level, the vacuum equals labout 8 inchesl of mercury, and so on down. each foot -of -depth taking oil about one mercury inch of effectivevness of the vacuum. Beyond flveffeet (or 5 mer? cury inches), however, there seems to be little vacuum effect. but this is desirable for it leaves that zone of liquid below the five foot level, in relative quiescence in which those solids of high specific gravity settling thereto, are permitted unmolestedly to form a sediment on the tank bottom, from which they can be removed as desired. 'I'he point of their withdrawal is preferably from a region within the treatment tank that is under the effect of vacuum equal to five inches or less of mercury, because this assures no floating material being carried oil with the sediment. Discharge of materials from such a machine naturally has to be through the medium of a liquid-sealed barometric or hydrostatic leg or its equivalent, for otherwise the effect'of vacuum would be lost by air-leakage.

It is generally desirable that nothing be interposed between the liquid level and the effect of the vacuum that interferes with the effectiveness of the vacuum. In order to keep the liquid level clean and clear of vacuum-obstructing material, this invention teaches that it is advisable to remove fromthe liquid level scum or other oating material (sometimes calledherein fioat) about as fast as formed so that there is no adverse accumulation thereof, and with the least disturbance of the underlying liquid. In order to accomplish this persistent and non-turbulent cleaning of the liquid level, it is also necessary to maintain the liquid level at a constant height so that floating material can be constantly and eiectivelyremoved therefrom, Where skimming is important of itself, the character of the scum may be controlled somewhat by the height of the liquid level as compared with the elTective level of the overflow Weir or dam of the scum discharge arrangement. If for instance, a material being handled forms a thick compactscum and it is desired to discharge this scum with a minimum of water-content, then the liquid level of the tank can be lowered to an elevation several inches below the scum overflow Weir independent of the scum discharge arrangement, through the medium of control features of the auxiliary compartment or control box with its adjustable suc- 45 tion nozzles. If on the other hand, the n handled does not form a compact scum water content is unimportant, the liquid vation of the tank can then be adju point from which most or all of the oat i.

by gravity over the dam into the scum discharge v outlet. One purpose of getting the scum or float out as soon as possible is so that the air bubbles attached to the solids arenot detached, for if detached in any substantial quantity, the buoyed up solids will settle and go out with the emuent.

The flotation effects attained by this vacuum treatment on suspended solids take place within a rather limited range of degrees of vacuum, so asl much as possible of the floatable material must 60 assuredly be conveyed into that horizontal layer of liquid'subject to such vacuum. This is assisted to some extent by rst diiusingv dissolving air or gas in the liquid fed to the vacuum tank whereby when the suspended particles encounter the lessened pressure in the tank. the dissolved and entrainedgas is released to form gas bubbles that attach themselves to solid particles and tend Ato float most of the suspended material into that area of limited vacuum effect. Aeration or gassing of the liquidl prior to its release into body of liquid being treated under the eiect of vacuseless for the notation function. large bubbles are detrimental because they cause undue agitation on being released.

facilitates the subsequent sedimentation.

prior to its release in the liquid body in order to remove from it substantially all large or coalesced bubbles. Rising vbubbles enlarge in ascending, and an expanding bubble tends to detach itself from the solid that is buoying up or floating.

` Therefore, the ilner or-smaller the bubbles developing from the liquid under vacuum the better, for merely large entrained air bubbles'v are In fact the the 1ers-behind non-acatabie and semeabie solids can assume their normal free settling rates.

'l'husin a machine embodying this invention, settleable solids settle better. The vacuum and the rising force exerted by the air bubbles on the suspended solids act like a collector, especially when there are grease or other foamor frothforming substances present, as is especially true i'n sewage and the like wastes. The vacuum apparently has a de-aerating effect. For instance, it makes activated sewage sludge sink. It has a depressant eifect on settleable solids, although not on slick solids. This type of action resulting from the eifect of vacuum, when sewage and the like are treated, iioats grease-bearing particles and other floatable material away from 'the settleable inorganics, so that the sediment separated and discharged by the apparatus of this invention is fairly clean. The vacuum will cause to float normally non-floatable inorganic matter of some types such as lime sludge derived from water softening, as magnesium hydroxide, borax, potash and the like. l

With respect to the treatment of sewage, lit is to be recalled that sewage coming to a treatment plant at times has a relatively high temperature. This, together with fiat sewer grades and long flow lines, often results in considerable anaerobic bacterial action taking place in the sewage prior to clarification treatment, with the result that there are usually present inthe incoming sewage substantial 1 quantities of. gas bubbles, buoyed scum, and floating, partially-digested sewage sludge. 'I'he discharge of large quantities of cannery wastes into sewerage systems aggravates this problem and increases the floating scum. 'I'he apparatus of this invention is quite effective von these conditions, forinot only are the vscum and the sludge separated, butthe sewage being treated in the machine is de-gassed.

I'he presence of finely-divided gas' bubblesin sewage or otherliquid has a Vdecidedly detrimental effect on clarification by sedimentation; so to rid the sewage of its entrained gas, substantially .And again, as sewage 'and the like wastes are usually highly odorous, the vacuum removal oi this invention ridsthe liquid of its entrained gases and thereby reduces their odor-giving content.

The trade-mark Vacuator" has been given to and used in connection with embodiments of this invention, prior to the tiling of this application, so that termfor'short, may be used hereinafter.'

A maior characteristic of a Vacuator is the vacnum removal from liquids not only of normally iioatable matter but also of normally non-float- 'able matter. -A further characteristic is the simultaneous independent removal from liquids of Thus it is a machine that accomplishes removal In some cases, the Vacuator`may be used as a by one path, while b y another path there is passed from the Vacuator, de-scummed liquid with non-iloatable solids unremoved from suspension therein. O ther uses may call for three separate discharge paths leading from the Vacuator namely (l) for scum, (2) for clarifier eiiiuent, and (3) for sediment or sludge. The Vacuator has yproven that it can do a fair joh of removing suspended solids at as high an overflow rate as 10,000 gallons per sq. ft. per 24hours.

Fig. 1 is a vertical sectional view of a continuous type of apparatus for separating and remov' ing of suspended matter from a liquid body. In connection withthis gure itis to be noted that a large main separating tank prominently appears and that a small or auxiliary liquid-level control tank or chamber is shown at the righthand side of the large maintank.

lary liquid-level control tank or chamber. In Fig. 2 the parts are shown at a larger scale than in Fig. 1. y

Fig. 3 is a horizontal sectional view taken -as on the line 3-3 of Fig'. 2 looking in the direc? tion of the arrows.

' Fig. 4 is a plan-view o f the apparatus of Fig. 1. In this ligure vcertain vparts of the top of a main separating tank thereof have Abeen broken away to show more clearly the construction of certain functional parts therein.

In the accompanying drawings; i0 represents 'a main tank, Il its bottom or floor, I2 its closed roof or top, |32. scum discharge duct o'r pathway elongated edge, dam or weir that is not normally submerged, I6 a.l funnel section of the scum discharge duct I3 that supports the weir I5 and a ramp Il leading up to the weir. IH represents '45 an upstanding draft-tube, I! a feed inlet pipe or conduit of which the draft-tube forms a func'- tional terminal. 2|) represents a flared outlet section of the draft-tube IB, 2| a spider therein by which the draft-tube is supported from shaft 5022 rotatably penetrating, in a gas-tight man-4 ner, the tank roof I2, which shaft is provided with a worm gear 23 that is'rotated Aby a worm 24, driven by a motor 25. 2B indicates scum raking arms, extending substantially radially from the shaft 22, and A2'I indicates scum sweeps carried by the arms 28`that are adapted for scum also for controlling the height of the liquid ,level L in the main tank. 3l indicates a freely com' 55 municating passageway provided by a pipe extending between the upper section of the main tank and the upper section'of the auxiliary or secondary tank Il; 32 indicates a closed top or roof on the secondary tank 30, while 33 indicates a liquid pathway or communicating pipe extendingbetweenthebottomilofthetanklandto the interior liquid-holding portion of the main l5 indicates a wet-vacuum pumpingmeans 75|uchngairorgasfromtheinteriorofthosec-- pended matter desired to be removed therefrom. Y

skimmer only, so that scum is discharged from it Fig. 2 is a vertical sectional view of the auxil. y

having a barometric or hydrostatic leg Il, l5, ank

free of scum accumulations thereon.

ondary tank 30 by such conduit means as a pipe 36 that terminates in an adjustable inlet end or nozzle 31. Pipe 36 and nozzle 31 can be duplicated as shown. 1f duplicated both -pipes 36 will merge into a single pipe 38 leading to the pump 35. The inlet ends or nozzles 31 are pivotally adjustable by means of hand-operated shafts 39 that extend through the casing of the second tank 30. 4|) indicates a valve that can be inserted in each suction pipe 36. 4I indicates a discharge pipe line extending from the vacuum pump 35, as shown. 42 indicates a port-hole or inspection glass 'in the top of the secondary tank 30. 43 indicates a waterY jet or spray to which water is supplied by pipe 44 that is controlled by valve 45, for washing the underside f the glass 42 46 indicates a gauge glass on the tank 3D. rA protected electric'light 41 mayA be located within the tank adjacent the port-hole glass 42 to illumine the contents of the tank for better view thereof through the port-hole.

50 indicates baffling means within the main tank I0 forming a. ring-like or annular eilluent take-off system for the main tank, for shielding the withdrawn liquid from descending or settling solids at the place of withdrawal of the eilluent liquid from the liquid body in the tank. This is preferablyprovided with a downwardly inclined top member 5I, a cylindrical member 52, a horizontal closure member 53 having apertures 54 therein located at intervals. 55 indicates a treated liquid, or eilluent take-off discharge pipe valved at 55' that is provided with a barometric or hydrostatic leg 56 that dips into a basin or pool 51 formed by means of an adjustable dam or Weir 58, over which liquid flows to discharge through effluent discharge pipe 59.

Fig. 1 shows an 'optional assembly of sediment or sludge rakin'g mechanism, supported from and rotating with the draft-tube I8. It comprises rake arm 63 extending generally outwardly from the draft-tube I (and, if necessary, braced with tie rods as shown) that are provided with sediment or sludge impelling or plowing means such v65, from which sediment can be discharged through pipe 66 and pump 61 ldownwardly through pipe 68 leading to a no-pool part 12 of lthe depressed sump 69.

' polluted liquid supplied for treatment. This pipe 16 delivers the liquid into a. wet-well or sump 11, wherein the liquid passes under an adjustable curtain baille 18. 19 indicates a gassi'ng station or gas diffusing means-for causing gas or air to be dissolved and entrained in the incoming liquid. In the drawing it is shown as a diusing or gassing impelle'r on a shaft driven by a motor 6D.

8| indicatesy a, de-aerating or de-gassing flowthrough passage or channel, in which there isA an adjustable height weir 62'ove'r which the liquid cascades before entering the Vacuator feed pipe I9. This passageway 8| is for de-aerating the liquidto rid it of enlarged entrained gas bubbles.


33 indicates a cover on the de-aerating passagel way to make the apparatus sightly. 84 indicates agate valve and means for operating it to open or close the entrance to the feed pipe I9. B5 indicates a junction box and 86 a pipe, whereby the newly incoming liquid can be by-passed around the Vacuator, if desired, since the pipe 86 joins into the sump 81, that is adjacent the pool 51. The discharge line 4I from the vacuum pump 35 all liquid isdiscarded through pipe 59.

Y 9D represents a manhole cover in the top I2 of the tank I0 for entrance. purposes.v 9| indicates an electrical light for illuminating the interior of the tank l0. 92 indicates.aglass-bearing porthole in the top of the tank I0 for visual inspection purposes, and 93 indicates a water jet or nozzle, supplied from pipe 94 with its valve a5, for washing scum from the underside of the glass of the port-hold 92.

It is to be observed that the inlet pipe I9 to the tank I0 has ,as its vertically-extending terminal the draft-tube .I8. Under thosek circumstances` where it is desired to have the drafttube rotatable, there is provided a liquid-tight slip-'joint as at 95 whereby the lower section of the rotatable draft-tube can rotate freely around the stationary upstanding' end of the pipe I9 without loss of liquid therebetween.

|00 .representsl a pipe or conduit for conducting gas, to the gassing station 19, if|desired inr stead of air, to be diffused in the liquid being treated, a gas such as CO2 that is inert to an oxy' gen demand of the liquid.'

- The operation of the Vacuator is as follows: the incoming new liquid to be treated therein first is to have gas, such as air, diffused therein. This is done in a gas-dissolving station, in the embodiment illustrated by means of usual aeration by the use of an aerating impeller IGI. Thereafter, the larger. bubbles, and at least some entrained air, are de-aerated from the liquid in the passageway 8|. The gassed and cie-aerated liquid then passes through the feed pipe I9 and upwardly inthe draft-tube I8 due to the eiect of vacuum within the main tank I0. There is maintained within the tank lIII an ever-changing body of liquid being treated, which reaches to a liquid level LA that is carefully controlled by meansv of the control assembly 30. The liquid rises in the control or secondary tank or compartment 3U through the pipe 33. The vacuum pump 35 in 4exerting a gas-exhausting suction through nozzles 31 on the interior of the secondary tank 30 5,5` above the liquid level L therein also produces a vcorresponding effect of vacuum in the upper section of the main tank I0 that is above its liquid level L, through the medium of thev freely comlmunicating passageway or pipe 3l that extends between the upper sections of the main and secondary tanks.

The liquid level L in the secondary tank 30 is controlled through'the adjustment of the nozzles 31, for the pump 35 is a wet-vacuum pump.

.65 If the liquid level tends to rise about the level of the nozzles 31, liquid is pumped therethrough until the liquid level in both tanks returns' to normal. Any liquid sucked up by the pump 35 is discardedthrough pipe 4I. It is to be noted '-70 that the minor body of liquid being treated that is hydrostaticallycontained withinV the secondary tank 30 is shielded from having any scum or floating material reaching it, because it is connected to the main tank at a point below which the scum has been released.

also discharges into this sump 81, from which,

the tank at a, diminished velocity. due to the flare 2li of the draft-tube I8. The velocityis diminished so that there is substantially no turbulence created above the draft-tube and its' `tends to shake bubbles loose from the solids to which the bubbles have become attached. As soon as the liquid is released from the drafttube I8. the lessened pressure or effect of vacuum, causes' the dissolved and ilnely divided entrained gas in the liquid to come out vof the solution, -whereupon lbubbles of gas are developed that cling to' suspended solids encountered by the vgas bubbles. In sewage and the like wastes, there is enough oil and'grease on the suspended solids to'act as an adhesive to cause the bubbles to adhere to the solids, whereupon the bubbles cause the solids to whichthey are attached to be buoyed up-and to float to the liquid level L. Accumulation of the floated solids forms a floating layer of scum.

It is desirable to continually. remove the scum to leave the liquid level as free thereof as possible. To this end, the scum arms 26 are rotated with shaft 22 from motor 26. 4The scum arms with their sweeps 26 push scum in front of them until the ramp 21 is encountered, when the sweeps 21 in riding up onto the ramp, push the scum before them, and .over the scum dam I6. The scumI falls from or cascades over the dam into the funnel section I6 of the scum removing ductmeans that includes the pipe IB, through which pipe plus its barometric leg'll, the scum is discharged from the main tank Il) and intothe pool ,or basin 1| `in a manner which prevents any air leakage into the tank Ill to otherwise spoil or diminish. the vacuum therein. l

`Liquid from which the oated material has been removed, is discarded from the tank as treated liquid or einuent through the eiiiuent take-oil assembly 50, byrising upwardly through the apertures N into the annular. baiiied space,

from whence it flows to discharge through pipe v 55. whichvalso is a barometric leg since it terminates in pool 61, to prevent air leakage into the tank I0. The assembly 6l shields the drawnoiI eilluent fromv descending'or settling solids,

and the assembly is located at a depth in the tank at` which the effect of vacuum is equal to the order of inches of mercury. 'It is the placev or region where there is a minimum of suspended solids and a minimum of sedimented solids. In

g those cases where the Vacuator is to be used'only to de-scum the liquid treated, the eilluent take-off will constitute the only other discharge duct from-the tank besides the scum removal duct. In such an instance, the eiiluent liquid will have entrained in it, those suspended solids. that have escaped or been immune to the flotation eil'ects of the vacuum. l

However, in other cases, it will be desirable to make a further separation by riding the eilluent liquid of its suspended solids that have escaped the vacuum notation. 'Ihis can be accomplished.

Liquid passes'up the draft-tube in the main'v tank I0 and is emitted into the body of liquid in m action, is desirable as turin theembodlment of the invention shown because the suspended solids that have escaped otation will descend and settle on the floor Il of the tank In by sedimentation processes, and will 5 accumulate as sediment on the iioor. The sludge rakes 64 in being moved at speeds that have a substantially non-rolling eiIect on the sediment, v l

by the traveling rake arms 63 due to rotation of the shaft 22 and draft-tube l6,'wil1 impel the sediment inwardly toward the centerof the tank III until the sediment reaches the sludge sump 65, -from whence the sediment or sludge can be removed by the pump 61 and discarded through 4 pipe 68 into the sump 12. In such a case, it can be seen that the sediment and the eiliuent liquid are discharged from Athe tank I0 by separate and independent paths. The level at which the eiiiuent take-ofi is located is deep enoughin the tank to be at a point where the effect of vacuum is so slight that practically all floating material is thereabove, for it is quite important that no, or

substantially no, oating material pass from thev tank with the treated eiiiuent. More particularly, the location of the eflluent take-off should be suniciently below thellquid level of the tank that the effect of the vacuum at that take-oil? level is less than or equivalent to not substantially moreA than 5 linches of mercury. Since the feed to the vacuator is continuousand the scum and so' tion of the machine is continuous, and the liquid being treated in the vacuator is an ever-changing body of liquid. Thesludge can be taken out trolled by the adjusted height of the suction noz-A zles 21 in the secondary tank or compartment 3|), by the adjustment of the nozzles 31, the liquid level in the tank Ill can be raised or lowered rel-1 atively to the height of the scum overflow dam l5. Ii the discharging scum is desired to be dewatered as much as possible, then the .liquid level is dropped somewhat below the scum dam I6. On

' the other hand, in Aorder to make the discharging scum more iluid, it may be desirable Ato have more water go out with it, in which case the liquid level in the tank I0 is raised with respect to the scum dam, by means of suitable adjustment of the pivvoted vacuum suction nozzles 31.

A Vacuator may be looked upon as an emcient substitute, at least in many instances, for a pres- '50 ent-day mechanically-cleaned clarifier, for experience has shown that a Vacuator is effective `,in ridding the liquid being treated of a substantial lportion of its suspended solids in about the proportion of 75% of floated suspended solids and 25% ofsettled solids. When the grease or oil content of the liquid is high, the floated solids removal is higher than otherwise. Further, the sludge discharging from a Vacuator is cleaner in that it has fewer, smaller and lighter particles entrained in it, for the sludge has in eiIect been exposed to what may be called a washing treatment. In a clarifier, the detention capacity is from one to three hours, whereas goed results have been obtained in a Vacuator having only threeminutes detention, although from one to the eillue'nt take-offs are continuous, the opera-l From the sump 12 the mixture of discharged -v creased.

Vcompared with an ordinary clarifier.

'Initial operation for starting up a Vacuator 1 can be carried out by one of two methods. The

Preferred method'is to close-all valves 84 and 55' n on the'inlet and outlet piping respectively so that the tank Ill can be filled by a pump (not shown) When the water level reaches the elevation of the scum dam I5, the pumping can be discontinued,

the air-outlet connections closed to wit, air out-` flow pibes controlled byvalves lll' the vacuum -pump 35 started, and as soon as the vacuum sauge used in connection with the pump 3i registers equivalent -to the hydrostatic leg in the tank, valves 8l and 55 in the inlet and outlet piping respectively can be opened simultaneously, and flow through the inverted slphon I9 and I8 will automatically start. Obviously all hydrostatic legs must be kept sealed with liquid.

The respective water levels in the feed and effluent compartments will automatically adjust themselves, depending upon the loss of head through the unit and the elevation of the overflow weir in an etlluent box.

The other method of starting consists in maintaining sumcient water in the boxes or pools in which the hydrostatic legs are located, starting the vacuumpump and thus pulling the water up into the tank as the absolute pressure is de- For shut-downs of several hours duration, all valves in lthe inlet and outlet piping can be closed when the flow has stopped, and the vacuum pump can then be shut down without emptying the tank contents. For shut-downs of longer duration, the device can be emptied by stopping the vacuum pump and admitting air slowly through a suitable valve in the tank cover.

The normal adjustments obtainable during regular operation consists principally of:

1. Control of water level elevation; and

2. Speed variation of skimmer mechanism.

, If for instance a material being handled forms a thick compact scum and vit is desired to discharge this scum with a minimum water content, then the water level in the control box should be adjusted by raising or lowering the nozzle to an elevation several inches below the scum dam. If, on the other hand, the material handled does not form a compact scum or its water content is not important, the water-level elevation can then be. adjusted to substantially that of the scum dam so that most or all of thescum will flow into the scum outlet by gravity. In some extreme or unusual cases it may be advantageous to raise the water level 'above the scum dam.

The presence of finely-divided gas bubbles in sewage or other liquid has a decidedly detrimental effect on clarification by sedimentation; so

` to'rid the sewage of its entrained gas, substantially facilitates the subsequent sedimentation.

And again, assewage and the like wastes are usually highly odorous. the vacuum removal of this invention rlds the liquid of its entrained gases 65 and thereby reduces their odor-giving content.

In the gassing, or diffusing of a gas in sewage, it has beenV found that sewage and certain other polluted waste liquids, have an loxygen demand. This is commonly referred to as B. O. D., which is an abbreviation of biochemical mgen demand.

If one attempts to diifuse air in such a liquid. the

` oxygen demand is so great that instead of the air being dissolved or entrained in the liquid. the oxygen of the air enters into chemical combination, with the result that when the aerated liquid gets into the scum flotation apparatus, ythe lessened pressure onthe liquid fails to develop' gas bubbles as it would, due tothe air c'om'ing out 'of solution-and entrainment.l Consequently, it is proposed by this invention, in connection Iwith oxygen demanding liquids, to practice the gassing step heretofore described, by the'use of lsome gas that is inert to the oxygen demand of the liquid. For instance, in ythe treatment of sewage, itA has been found that the gassing step can be satisfactorily carried out by the use of carbon dioxide (CO2) gas. This has the advantage not only of being readily soluble in the l sewage liquid, but upon encountering the lessened' pressure, due to the effect of vacuum in the scum oating apparatus, the C0: comes out of solution and develops a maximum of very small bubbles, that are highly eifectlve for flotation purposes.

Since the solubility of nitrogen in water is twice that ofoxygen, it is indicated that a nitrogen bearing gasvcan well be used. Of course, if the gsssmg be. donewitn a gas .other thansmtng gassing must be done in a manner so that the gas is not allowed to be wasted, so under such conditions, the gasing station 19 would have* to be provided with a pipe or duct |00 that conveys the COz'or other inert gas for release directly into the agitation zone of the aerating or gassing element I9. The point of this feature of .this invention is the supplying, to an oxygen demanding liquid, ofa gas that is inert to the oxygen demand or the liquid. Maximum solution and entrainment of the gas in the liquid is desired with a minimum of chemical reaction of with the liquid.

We claim: l. The process of removing suspended solids from their carrying liquid which comprises mainthe gas from the surface of the body at a point functionally remote 'from the point or application of the suction. and continually removing from the body clarified liquid.

1 2. The process ol' removing suspensions from a liquid bearing'them which comprises establishing and enclosing liquid divided into a major liquid body and a minor liquid body with both bodies havingv a common atmosphere and with liquid inthe minor body having a vertically fluctuatlns liquid level, Supplying feed liquid to the major body,-removing floating scum from the major liquid body, discharging eilluent from the enclosed liquid from a place functionally remoteAA from the oating scum, sucking liquid from the minor body when the liquid level thereof rises above a predetermined elevation, and sucking gas from above such liquid when the liquid level thereof falls below such predetermined elevation. 3. Apparatus for the removal 0f suspensions from a liquid bearing them which comprises a closed tank adapted to h'old a liquid body whose taining an enclosed body or liquid being treated removing means adapted to pump liquidthrough the suction means when the liquid level rises thereabove and thus controlling the liquid level of the tank. and means for removing treated liquid from the tank having an inlet in the tank `that is disposed functionallyA remote from the inlet to the floating material removing means.

4. APPBlatus according to claim 3, including means providing an v auxiliary compartment as sociated with the tank for holding in its lower portion liquid derived from the liquid of the tank and having its topportion in gaseous communication with the space above the liquid in the tank. with the addition that the inlet of the suctionv means is adjustable and is associated with th'e auxiliary compartment for controlling the liquid level of the liquid therein.

5. Apparatus for the removal of suspensions from liquids comprising a closed ytank adapted to hold a liquid body having a normally vertically fluctuating liquid level, tube means by which gassed liquid may be fed intothe tank and delivered in the region of the surface level of the liquid in the tank, comb d wet and dry suction means adapted to maintainsub-atmospheric/ pressure within the tank including a pipe having an inlet disposed within the vertical limits of they iluctuating liquid level, and a pump connected with said pipe e'ective to draw liquid therethrough when the inlet is submerged and to draw gas therethrough when the inlet is unsubmerged,

a scum-discharge duct leading from the tank including a liquid seal thereon exteriorly of the tank, means for sweeping floating scum into the scum duct, and means for conducting treated liquid vfrom the tank including a liquid-sealed lower end outside the tank. l 6. Apparatus according to claim 5 with the addition of av dam' provided at the upper intake end portion of the scum discharge duct over which iloating material must pass before entering said duct. and wherein said suction means includes adjustable means for varying the liquid level relative to the dam. l 4'L Apparatus for removal of impurities from liquids comprising a closed tank adapted to hold a liquid body, tube means isby which gas-containing liquid may be fed to the tank and delivered at the lregion of the liquid level in the tank, suction-producing means for maintaining vaca uum within the tank, --a- 4scum-discharge duct including a dam at -the upper end thereof and having a. liquid-sealed lower end, means for sweeping floating material in the tank over the dam and into the scum duct, means for removing treated liquid from the tank at an elevation lower than that of said dam and having a liquidsealed lower end. said suction-producing means having a positionable suction inlet disposed at l an elevationvproximate to that of the upper edge l savor rated fromA the positionable suction inlet.

9. Apparatus for removal of suspended matter .I from liquid comprising a tank adapted to hold -a main body of liquid being treated, tube means leading into the tank ,and 4having a terminal from which gas-containing liquid being treated is delivered within the tank, means for maintaining adjacent the main liquid body a second body of liquid whose liquid level is subject to atmosphere with the main body, means for connecting the atmosphere of the second body with that-of the main body, means providing a pas'- l5 rial floating on the-main body, means for removing treated liquid from the g tank, and suction means essentially embodying a gas-liquid pump and a pipe having an inlet disposed cooperatively within the vertical limits of the fluctuating level of the second liquid body serving for alternately withdrawing liquid through the pipe inlet when submerged and gas when unsubmerged for thereby controlling the liquid level of the second liquid bodyas well as gfor applying vacuum to the comf mon atmosphere of the main and second liquid bodies. 10. Apparatus Vfor the treatment of (liquids having suspensions therein which comprises a closed tank adapted to hold liquid with at least la portion of which whose liquid level uctuates vertically. tube means terminating inthe tank -for supplying gas-containing feed liquid there- -to, scum-receiving means having an inlet disposed to receive oatng scum, means for passing `scum fromv the tank through said receiving means 'whileminimizing leakage of air there- 4 having an inlet disposed functionally remote from the scum inlet but within the range of iluctuationsof the liquid level for sucking liquid whenthe inlet is submerged and gas when nonsubmerged whereby sub-atmospheric pressure is 'maintained on the tank liquid, effluent discharge conduit means leading from the tank having an inlet seetion'that `is disposed functionally remote from the scum-receiving means, liquid-seal means exteriorly of the tank associated with thev eilluent discharge means for minimizing leakage of air therethrough, and means for shielding from suspended and settling solids the inlet section of the conduit means. l 11. Vacuum flotation apparatus comprising a closed tankadapted to hold a body of liquid therein having a liquid level, feed inlet means having a rotatable feed-emission terminal and a fixed delivery section leading thereto vby which gas-containing liquid suspension is fed into the tank and released into the liquid body at the region of the surface level thereof` suction means for applying sub-atmospheric pressure to the surface of the liquid in the tank, a -scum-discharge duct leading from the tank proximate to the liquid level therein, means for sweeping oating scum thereinto, 'a motor-driven shaft extending vertically into the tank, conduit means leading from the tank for conducting treated liquid therefrom, independent liquid-seal means ported and rotated from said shaft, and the scumv l the noot-sweeping means is functionally sepavertical fluctuations and which has a. common sageway for flow of liquid from one body to the other, means forv removing from the tank matethrough, suction means leading from the tank forv the. scum duct and for the conduit means sweeping means being also from said shaft.

12. An apparatus for `performing a continuous process for separating and removing oi' suspended matter from a liquid which comprises a closed top main separating tank adapted for the establishment therein 'of an ever-changingm'ain body of liquid for treatment normally maintained at a pre-determined liquid level and of a gas-holding portion that directly overlies said liquid body whose pressure is maintained substantially Vlower than vthatof the outside atmosphere; means providing an auxiliary liquidheight control compartment having a 4lower liquideholding portion adapted for the establishment therein of an auxiliary body of liquid derived from the mainv tank and an overlying gas-holding portion; means defining a freely communicating gas passageway between said gas-holding portions; pumping means for resupported and rotated means the normal liquid level'of the body of liquid in the main tank and alsoto remove any liquid tending to rise above thel so-e'stablished normal liquid level; means for continuously submergedly delivering a liquid-solids suspension into the main tank while permitting no substantial leaking of outside air into the main tank; meansA for continuously releasing liquid from the main tank without permitting any'substantlal leakage of outside air into the main tank; an open top'trough located within the main tank having a horizontally extending transfer edge at an elevation proximate ,that of the nozzle intake means; and means for transferring material from said open top trough to the exterior of the apparatus without permittingany .substantial leakage of outside air into the tank.'v

moving gas from said gas-holding portions and adapted for maintaining substantially sub-atmospheric pressure conditions therein and oomprising on the intake side thereof pipinghaving 13. An apparatus according to claim 12, also having means for impelling floatable matter from the surface of the body of liquid in the main tank towards and over the horizontally extending transfer edge ofthe trough and thus into the open mp trough.



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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2604443A (en) * 1949-10-18 1952-07-22 Russell V Fipps Spraying system for sludge separators
US2679477A (en) * 1949-09-15 1954-05-25 Process Engineers Inc Sewage treatment
US2929508A (en) * 1957-12-27 1960-03-22 Phillips Petroleum Co Polymer skimmer

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2679477A (en) * 1949-09-15 1954-05-25 Process Engineers Inc Sewage treatment
US2604443A (en) * 1949-10-18 1952-07-22 Russell V Fipps Spraying system for sludge separators
US2929508A (en) * 1957-12-27 1960-03-22 Phillips Petroleum Co Polymer skimmer

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