US3707235A

US3707235A - Wastewater concentrator with plural distributors

Info

Publication number: US3707235A
Application number: US126080A
Authority: US
Inventors: Walter J Talley Jr
Original assignee: Sweco Inc
Current assignee: Sweco Inc
Priority date: 1971-03-19
Filing date: 1971-03-19
Publication date: 1972-12-26
Anticipated expiration: 1989-12-26
Also published as: US3727768A

Abstract

There is disclosed herein equipment and methods for screening and concentrating wastewater overflow from combined sewer systems and the like. Exemplary equipment includes a separator employing a substantially cylindrical rotating screen. Influent is piped upwardly into the equipment and deflected outwardly by plural distributors toward the inner surface of the screen in a manner to achieve a desired flow rate and flow pattern of the influent onto the screen. Means including the distributors are provided for controlling the flow rate and for suitably directing the influent in a plurality of substantially discrete inclined streams toward the inner surface of the rotating screen. The screen is rotated at a speed to achieve a desired centrifugal force. Effluent passes through the screen to an outlet and the remaining concentrate passes to an outlet. The screen is in the form of a screen cage having a plurality of removable screen panels for facilitating replacement of damaged screens or changing screen type or mesh size. Cleaning means is provided for directing a cleaning fluid periodically at the screen. The methods disclosed involve the manner in which the influent, effluent, concentrate and backsplash are handled, and the manner in which the influent is screened to achieve a fluid concentrate which may be pumpable to other treatment equipment for ultimate disposal.

Description

United States Patent Talley, Jr.

[451 Dec. 26, 1972 [541 WASTEWATER CONCENTRATOR WITH PLURAL DISTRIBUTORS [72] Inventor: Walter J. Talley, Jr., Brentwood Park, Calif.

[73] Assignee: Sweco, Inc., Los Angeles, Calif. [22] Filed: March 19, 1971 [21] Appl. No: 126,080

Related US. Application Data [63] Continuation-impart of Ser. No. 42,165, June I,

1970, abandoned.

Primary Examiner-Samih N. Zaharna Assistant ExaminerF. F. Calvetti Attorney-Lyon & Lyon [57] ABSTRACT There is disclosed herein equipment and methods for screening and concentrating wastewater overflow from combined sewer systems and the like. Exemplary equipment includes a separator employing a substantially cylindrical rotating screen. lnfluent is piped upwardly into the equipment and deflected outwardly by plural distributors toward the inner surface of the screen in a manner to achieve a desired flow rate and flow pattern of the influent onto the screen. Means including the distributors are provided for controlling the flow rate and for suitably directing the influent in a plurality of substantially discrete inclined streams toward the inner surface of the rotating screen. The screen is rotated at a speed to achieve a desired centrifugal force. Effluent passes through the screen to an outlet and the remaining concentrate passes to an outlet. The screen is in the form of a screen cage having a plurality of removable screen panels for facilitating replacement of damaged screens or changing screen type or mesh size. Cleaning means is provided for directing a cleaning fluid periodically at the screen. The methods disclosed involve the manner in which the influent, effluent, concentrate and backsplash are handled, and the manner in which the influent is screened to achieve a fluid concentrate which may be pumpable to other treatment equipment for ultimate disposal.

9 Claims, 5 Drawing Figures PATENTED B I972 3.707. 235

sum 3 or 3 I INVENTOR.

I WAATEEJ MALEV WASTEWATER CONCENTRATOR WITH PLURAL DISTRIBUTORS CROSS REFERENCE TO RELATED APPLICATIONS The concepts disclosed herein are directly related to those disclosed in applicants co-pending application Ser. No. 42,165 (now abandoned in favor of Ser. No. 211,763, filed Dec. 23, 1971) entitled IMPROVED WASTEWATER CONCENTRATION" filed June 1, 1970, of which the present application is a continuation-in-part, the disclosure of which is incorporated herein by reference. This co-pending application discloses a wastewater concentrator constructed and operated similar to that disclosed herein; however, the present wastewater concentrator with plural distributors is an improvement thereoven The concepts disclosed herein also are related to those disclosed in US. Pat. No. 3,539,008 entitled SCREENING APPARATUS EMPLOYlNG ROTAT- ING CYLlNDRlCAL SCREEN AND STATIONARY FEED MEANS," and US. Pat. No. 3,511,373, both of which are assigned to the assignee of the present application and the disclosures of which are incorporated herein by reference. Briefly, said US. Pat. No. 3,539,008 discloses apparatus involving a rotating substantially cylindrical screen in combination with a stationary distribution means for screening an influent. The screen and distribution means may be used in combination with a downstream planar vibratory separator for further screening of the concentrate from the rotating screen. Said US. Pat. No. 3,511,373 discloses apparatus similar to that of the foregoing patent and is directed to means for facilitating cleaning of said rotating screen. Reference is also made to related applications, filed concurrently herewith, Ser. No. 42,098, now abandoned, entitled UP-FLOW SEPARATOR," filed in the name of Theodore R. Westfall; Ser. No. 42,099, now abandoned, entitled IMPROVED ROTATING SCREEN SEPARATOR, tiled in the name of Philip H. Mook; and Ser. No. 42,100, now US. Pat. No. 3,627,130, entitled WASTEWATER CON- CENTRATION," filed in the names of Walter J. Talley, Jr. and Howard W. Wright, Jr. These applications contain a similar disclosure to that set forth in said application Ser. No. 42,165, now abandoned, but include claims directed to various of the structural and operational features disclosed therein.

BACKGROUND OF THE lNVENTlON This invention relates to the screening of a liquidsolids influent to achieve a desired separation of liquids and solids, and more particularly to screening of storm water, sewage or storm water overflow from combined sewer systems and the like.

Although the present inventive concepts are useful in screening various materials, they have particular application for water pollution control and, thus, will be described in this environment and particularly for finemesh screening for primary treatment of storm water overflow from combined sewer systems. As set forth in a research report on treatment of storm water overflow entitled Rotary Vibratory Fine Screening of Combined Sewer Overflows prepared by Cornell, Howland, Hayes and Merryfield in connection with Department of the interior Contract 14-12-128 and dated March 1970, the majority of the existing combined sewers throughout the nation do not have adequate capacity during heavy storm periods to transport all waste and storm-caused combined flows to a treatment facility. The overflow is bypassed to a receiving stream, thus causing pollution in the nation s water courses.

As further described in said report, the Federal Water Pollution Control Administration published a report in 1967 reviewing the effects and means of correcting combined sewer overflows on a national basis Of the 200 million people residing in the United States approximately million are served by combined or separate sewer systems, and of the 125 million, approximately 29 percent are served by combined sewers. Combined sewers are designed to receive all types of waste flows, including storm water, for ultimate treatment at a treatment facility. In determining the size of the combined sewer, it has been common engineering practice to providecapacity for three to five times the dryweather flow. During intensive storm periods, however, the storm-caused combined flow may be two to 100 times the dry-weather flow, making overflow conditions unavoidable. To compound the problem, most treatment facilities are not designed to handle the hydraulic load of the combined sewer and, therefore, are required to bypass a portion of the storm-caused combined flow to protect the treatment facility and treatment process from damage. The nations treatment facilities bypass flows an estimated 350 hours during the year, or about 4 percent of the total operation time. The pollutional impact of the storm-caused combined overflow of the waters of the nation has been estimated as equivalent to as much as percent of the strength of the domestic sewage biochemical oxygen demand. This amount creates a major source of pollution for the nation 's water courses. The Cornell et al. report further describes certain tests, results and recommendations with respect to the use of high-rate fine-mesh screens for primary treatment of storm water overflow from combined sewer systems, the equipment described being similar to that disclosed in said U.S. Pat. No. 3,539,008 and US. Pat. No. 3,511,373.

The present application relates to a wastewater concentrator involving certain improvements over those disclosed in said aforementioned applications and patents. Briefly, the present application is directed to a wastewater concentrator similar to that disclosed in said co-pending application Ser. No. 42,165, but involves the use of plural distributors and a larger screen cage which provides significantly improved results in terms of peak hydraulic capacity, substantial reduction of splashback from the screen, increased screen life and performance at a lower concentrate percentage.

In light of the foregoing, it is a principal object of the present invention to provide improved screening equipment.

A further object of this invention is to provide an improved screening device employing a rotating screen and distribution means associated therewith.

An additional object of this invention is to provide an improved screen device employing a rotating screen and plural distribution means for feeding flows of influent to said screen.

will become apparent through a consideration of the following description and drawings.

SUMMARY OF THE INVENTION There is disclosed herein a screening apparatus, such as for use in screening of storm water overflows from sewer systems, comprising a substantially cylindrical rotary screen device disposed for rotation within a housing, feed means for directing an influent toward the inner surface of the screen, and outlet means for receiving (a) the effluent which passes through the screen, (b) the concentrate which does not pass the screen, and (c) backsplash from the screen.

The feed means includes an upwardly extending feed pipe, or the like, for supplying the influent to plural distributors. In an exemplary embodiment, two distributors are used, and deflector means are associated with the feed pipe for deflecting portions of the influent to the respective distributors which in turn direct the portions of influent toward the inner surface of said screen as a plurality of substantially discrete inclined streams. The deflector means may be adjustable for varying the rate of flow of influent to one or both of the distributors.

The rotary screen is in the form of a substantially cylindrical cage and includes a plurality of screen panels, which may be removed for repair, cleaning or replacement with different mesh screens or different screen cloth. The screen panels preferably are square and arranged in two rows within the screen cage. The use of square screen panels allows the same to be removed and repositioned, after rotation of the panel by 90, 180 or 270, for equalization of screen wear and thus increased screen life.

The speed of rotation of the screen is selected to provide a desired centrifugal force, or g-loading of influent on the screen, the g-loading being a function of the radius of the screen and the square of the rpm thereof. The velocity of flow of influent onto the screen is selected within a preferable range below which suitable impingement does not occur, and above which excessive splashback and possible screen damage may occur. A typical flow velocity is in a range around approximately to feet per second to each distributor, and an exemplary preferred screen speed is approximately 60 rpm for a 60 inch diameter screen, it being appreciated that other suitable flow velocities, screen speeds, diameters, and the like may be employed without departing from the present concepts. The influent preferably is screened to achieve a relatively fluid concentrate, as distinguished from a dry concentrate, so that the same may be readily transported or pumped for further treatment or disposal.

A screen cleaning apparatus may be provided for spraying cleaning fluid through the screen at desired intervals as described in said application Ser. No. 42,165.

4 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional elevational view of a preferred screening apparatus according to the present invention;

FIG. 2 is a perspective view of a double distributor of the apparatus of FIG. 1;

FIG. 3 is a partial perspective view of a rotary screen cage of the apparatus of FIG. 1;

FIG. 4 is a graph depicting exemplarly hydraulic split vs. solids loading; and

FIG. 5 is a partial view of a deflector of the apparatus of FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENTS Turning now to the drawings, and particularly to FIG. 1, a rotary screening device is illustrated including an outer substantially cylindrical housing 10 containing a rotary screen cage 11, and influent feed pipe means 12 and two distribution domes or distributors I3 and 14 for supplying influent toward the inner surface of the screen cage 11. The device also includes an effluent outlet 15, a concentrate outlet 16, and a backsplash outlet 17. A drive assembly 18 is provided for rotating the screen cage 11. The feed pipe means 12 includes an inlet pipe 19 and a smaller coaxially mounted pipe 20. impingement plates or

diverters

21 and 22 are provided for respectively deflecting influent from the pipe 19 to the distributor I3 and from the pipe 20 to the distributor 14.

As will be more fully explained subsequently, an influent, such as storm water overflow having enormous amounts of water and relatively little solids, is fed to the feed pipe means 12 and deflected downwardly and outwardly by the

impingement plates

21 and 22 to the dis tributors l3 and 14, and outwardly therefrom toward the inside of the rotating screen cage 11. The screen cage includes a plurality of screen panels, and the influent is screened resulting in a highly liquid effluent and a flowable concentrate. The effluent is discharged by outlet 15 and the concentrate is discharged by outlet 16. The screen cage 11 is rotated at a speed to provide a suitable centrifugal force for the screening action, and the

impingement plates

21 and 22 are positioned to provide the desired flow rate of influent toward the screen cage. The distributors l3 and 14 in combination with the

plates

21 and 22, are provided to direct the influent as a plurality of substantially discrete inclined flows toward the inner surface of the screen cage.

These screening concepts serve to reduce pollution caused, for example, by overflow of combined stormsanitary sewage systems during periods of heavy rain fall. As much as one third of the sewage solids settle to the bottom of large combined sewers and in periods of heavy rain, they flow into streams, lakes, rivers and coastal waters without treatment. Thus, during storm peaks, up to percent of the untreated sanitary sewage may overflow into receiving waters. As a result, combined treatment systems often lose more pollutants to their rivers and streams than they take out in the treatment plant itself.

As will appear from the following description and drawings, the present apparatus and concepts meet many storm-sanitary pollution control requirements for a compact, low cost, high volume, primary treating system. The present apparatus is capable of relieving a combined sewage system of its hydraulic overload during storm periods, while sending a pollutant concentrate to the treatment plant.

Exemplary apparatus is approximately 7 feet in diameter and 6% feet high, and employs two rows of square screen panels on the revolving screen case, with each row having 18 panels approximately inches square. A combination of influent flow velocity and centrifugal force can allow approximately 90 to 95 percent of a hydraulic flow of 3 to 4 million gallons per day to pass through the screens. The remaining concentrate containing a high percentage, such as 99 percent, of the floatable and settleable solids is discharged separately into the hydraulically relieved sewage system.

Considering the construction of the apparatus in more detail, the housing 10 includes a base 24, a substantially cylindrical upstanding wall 25, and a top cover 26 to provide a substantially closed container. The screen drive assembly 18 may be mounted within a housing 27 on the top of the apparatus, and includes a motor 29 and gear box 30 suitably mounted for driving a drive pulley 31 by means of V-

belts

32 and 33. A pair of

bearings

34 and 35 are suitably mounted on top of the apparatus, and a shaft 36 is journaled in the

bearings

34 and 35 and coupled to the drive pulley 31. The drive shaft 36 has a collar 37 secured thereto, as by welding. A central collar 38 affixed to the screen cage 11 is bolted to the collar 37 to enable the shaft 36 to rotate the screen cage.

The cover 26 may be a lift-off cover, if desired, to enable access to the interior of the apparatus. The wall 21 of the housing 10 may include a window 41 for observation of the interior of the apparatus. Suitable bracing is provided within the housing for structural purposes and for firmly supporting the various pipes. An angle bracket 42 and braces 43, for example, are provided as illustrated in FIG. 1 to secure the various components within the housing.

The screen cage 11 will be described in more detail subsequently, but generally includes a cage formed of a lower angle ring 46, an upper bar ring 47, and a plurality of upstanding bars 48 extending between the angle ring 46 and bar ring 47 as best seen in FIG. 3. Eighteen bars 48 have been used for an exemplary cage approximately 60 inches in diameter. Support ribs 50 are connected between the various bars 48 and the central collar 38 which is secured to the collar 37 affixed to the shaft 36 as noted earlier.

Removable screen panels

52 and 53 having a frame and screening material of metal or cloth secured thereto are inserted in two rows between the vertical bars 48 and clamped thereto in a substantially sealed relationship.

As noted previously, an influent to be screened is supplied through the influent pipe 12 and directed upwardly through the pipes 19 and toward the

impingement plates

21 and 22. The plates deflect the flow to the distributors l3 and 14 and from there out wardly toward the inner surface of the

screen panels

52 and 53 of the screen cage 11. The vertical position of the

plates

21 and 22 are adjustable as will be explained subsequently so as to control the rate of flow of influent. The lower distributor 13 is secured in a suitable manner to the upper end of the pipe 19. This distributor 13 may include a central sleeve 60 secured, as by welding, to the pipe 19, and includes a plurality of inclined plates 62 secured to the outer surface of the sleeve 60. A portion 63 of each plate 62 may be bent upwardly as shown in FIG. 2, or separate spacers may form the portions 63, and be secured to the underside of the next succeeding plate so as to form a rigid structure.

The upper distributor 14 may be constructed in a similar manner of a central sleeve, which may be formed by the pipe 20, and a plurality of inclined plates 64 secured to the outer surface of the pipe 20. A portion 65 of each plate 64 may be bent upwardly as shown in FIG. 2 and be secured to the underside of the next succeeding plate 64 so as to form a rigid structure as is the case with the distributor 13. The upper distributor 14 may be secured in any suitable manner, such as by means of vertical spacer rods 66 as seen in FIGS. 1 and 2, or, alternatively, the

pipes

19 and 20 may be secured together as by gussets, so as to form a rigid structure of the two

distributors

13 and 14. If desired, the spacers 66 may be threaded to enable adjustment of the spacing between the two

distributors

13 and 14.

The lower impingement plate 21 may be coupled to the pipe 20 by means of a flange 68 affixed to the periphery of the pipe and bolts 69. This arrangement allows adjustment of the position of the plate 21 with respect to the upper end of the pipe 19, and thus adjustment of the rate of flow of influent to the lower distributor 14. The upper impingement plate 20 may be secured to a rod 70 which extends upwardly through the shaft 36. The upper end of the rod 70 may be threaded into a threaded bushing 71 which is secured to the upper end of the shaft 36. The rod 70 thus may be adjusted up or down to vary the position of the plate 22 with respect to the upper end of the pipe 20, and may be locked in position by a locknut 72. With this an rangement, the plate 22 rotates with the screen cage 11, but may be made stationary if desired by other suitable supporting structure. Both of the

impingement plates

21 and 22 may have respective downwardly extending lips 74 and 75 for providing better deflection of the influent toward the

distributors

13 and 14 The

distributors

13 and 14 function to direct influent, which has been deflected by

respective impingement plates

21 and 22, into substantially inclined streams toward the inner surface of the

screen panels

52 and 53.

An interior wall or divider 76, which is substantially cylindrical, is secured within the housing and extends almost up to the horizontal surface of the flange of the angle ring 46. This divider forms, in combination with the housing wall 25, an annular chamber 77 for receiving effluent and directing the same to the effluent outlet 15. The effluent, as is known to those skilled in the art, is the material which passes through the screen panels in the screen cage 11. The divider 76 also encloses a concentrate chamber or bowl 78 which has an inclined bottom 79 for directing concentrate to the concentrate outlet 16.

A backsplash pan 81 may be used and positioned within the chamber 78 and coupled with a support 82. The pipe 17 communicates with the interior of the pan 81. The top of the pan 81 is approximately at the elevation of the bottom of the screen panels and the radius of the upper portion of the pan 81 is slightly smaller than the interior diameter of the screen cage 11 so as to receive any influent which may splash back from the inner surface of the screen cage 11 and screen panels. The radius of the pan 81 typically may be about 2 inches less than the radius of the screen cage 11. Concentrate flows through the gap between the interior of the cage 11 and the exterior of the pan 81 to the chamber 78. The purpose of the backsplash pan 81 is to enable any influent which splashes from the screen cage 11 to be collected for either recycling with incoming influent or sent to another separator device for screening to ensure that the maximum desired split between effluent and concentrate is achieved. However, through the use of plural distributors and a lower feed velocity of influent toward the screen panels, it has been discovered that such backsplash found in earlier devices is almost eliminated.

Turning again to the

influent impingement plates

21 and 22, the same are adjustable up and down as noted earlier. The purpose of this adjustment is to enable control of an orifice area 85 between the impingement plate 21 and the upper end of the pipe 19. A partial detailed view of this plate 21 is shown in FIG. 5, and the same includes an inverted frusto-conical member 87 which acts, in combination with the top edge of the pipe 19, to form the adjustable orifice area 85. Similarly, the orifice area 86 between the lower surface of the plate 22 and upper end of the pipe 20 can be controlled or varied. This arrangement allows control of the split of influent between the two

distributors

13 and 14 as well as control of the rate of flow of influent toward the screen panels. The

plates

21 and 22 may have other shapes, such as a segment of a sphere. However, it is desired that the flows of influent toward the inner surface of the screen cage 11 from

distributors

13 and 14 be substantially perpendicular (as viewed in FIG. I) to the inner surface of the

screen panel

52 and 53 rather than significantly inclined upwardly or downwardly. If these flows are sharply inclined downwardly, the concentrate is excessively liquid; but, on the other hand, if the flows are precisely horizontal and thus perpendicular to the inner surface of the screen panels, the flows do not fan out sufficiently to give a wide sweeping flow onto the inner surface of the screen panels. Accordingly, it is desired that the flow of influent be almost perpendicular to the inner surface of the screen panels but at a slight downward angle to obtain a divergent flow, or fan-out of the flow, by the time the influent hits the screen panels. Each flow of influent from a distributor should fan out to anywhere from substantially the entire height of the respective row of screen panels to approximately one-half the height of the row of screen panels, or slightly less, such as to provide an impingement area of influent onto the screen panels about 6 inches high. That is, the inclined flows from distributor 13 should fan-out and cover a height of about 6 inches of the approximately inch high panels 53. The same is true for the flows from distributor 14. Thus, it is desired that the flows fan-out slightly, but still flow substantially horizontally from the

orifices

85 and 86, the fanning-out being accomplished by the respective distributors l3 and 14 into two groups of essentially discrete inclined streams. If only a portion of the height of the screen panels is swept by the influent flows, the panels can be turned over end-for-end or 90 after a period of use to maximize screen life.

As discussed earlier, the majority of the existing combined sewers throughout the nation do not have adequate capacity during heavy storm periods to transport all waste and storm-caused combined flows to a treatment facility. The overflow is bypassed to a receiving stream, thus causing pollution problems. One of the principal applications of the present apparatus is in screening enormous amounts of water with solids, such as storm overflow, to separate out the solids and provide a relatively fluid, as distinguished from dry, concentrate which can then be properly handled by a sewage treatment facility. The effluent can be suitably disposed of, as for example in a stream or applied to secondary treatment. In this manner, the enormous amounts of water do not overtax the sewage treatment facility, while still enabling proper treatment of the maximum amount of solids from the overflow.

One of the principal objectives is to achieve a high split, that is, ratio of effluent (screened product) to concentrate (unscreened product), while still obtaining a slightly fluid concentrate which can flow continuously from the apparatus and be supplied, as by pumping, to subsequent primary treatment equipment without the problems involved in handling a solids concentrate. A typical ratio is better than 90 to 10 with the apparatus described herein and with a typical influent flow of about 2500 gallons per minute. A number of factors affect this split, one of the principal factors being the centrifugal force involved in the screening operation, which varies as the square of the screen cage rpm and as a direct function of the radius thereof. There is a band of optimum performance in terms of centrifugal force. it has been found that a centrifugal force of around 3 gs appear to be optimum in achiev' ing the maximum split, although it is to be understood that the force can be below or above this value somewhat. This approximate force or band around 3 gs can be obtained with a screen cage speed of approximately 60 rpm for a screen cage about 60 inches in diameter, or alternatively approximately 88 rpm for a screen cage about 36 inches in diameter. Substantially higher speeds do not improve the split and can actually degrade the split. Additionally other factors are important in achieving the maximum split, and these include the velocity of the feed of influent, such as approximately 5 to 10 feet per second to each distributor, which can be selected by varying the size of the orifices and 86 through adjustment of the

plates

21 and 22; directing of the flows of influent substantially perpendicular to the inner surface of the screen cage as noted earlier; maintaining the screen panels clean; the orientation of the screen cloth in the screen panels; and recycling or other screening of backsplash from the screen cage.

The centrifugal force is important in achieving the maximum force on the solid and water particles for separation of the water from the solids, but must not be excessive because the solids will then tend to cling to the screen and blind or clog the screen and, additionally, screen damage may result from high forces. At the optimum force or band of force, the concentrate flows by gravity down from the screen. The provision of almost perpendicular flows to the inner surface of the screen is important as noted earlier so as to achieve the maximum separation with the minimum of backsplash or other deflection of influent from the screen cage. As

fluent reaches the screen. If too high, too much influent reaches the screen and excessive backsplash may occur, and the high forces may cause premature blinding of the screen and/or damage thereto. The backsplash represents unscreened influent, much of which is believed to be deflected from the bars 48 of the screen cage, and the backsplash can be recycled or otherwise further screened to optimize the split. It will be apparent that the screen panels must be clean to achieve the best screening action, and a cycle of influent feed and spray cleaning with a cleaning fluid is preferred as described in application Ser. No. 42,165. The orientation of the screen cloth within the cage is important from a wear-life standpoint. It is preferable that the screen cloth be bias mounted, as described in said lastnamed application, to form the screen panels rather than positioning the cloth such that the wires or thread of the screen cloth run vertically and horizontally. The bias mounting disposes the wires or thread at substantially 45 angles resulting in better screen life because the screen wires are stressed and flexed equally and uniformly by the flows of influent. This longer life allows the screen cage to run longer with less down-time therefore improving the efficiency of screening. Also,

the slope of the

inclined plates

62 and 64 of the

distributors

13 and 14 affects the height of which the flows impinge on the screen panels and, thus affects screen life. A 6 inch drop at the edge of the plate where the radial length of the plate is 28 inches gives a slope of 21 percent which has been found suitable for a 60 inch diameter cage.

Furthermore, it is believed that the direction of rotation of the screen cage with respect to the inclination of the

plates

62 and 64 may contribute to obtaining the most efficient screening operation. The direction of rotation of the screen cage 11 is preferably as indicated in FIG. 2 (counter clockwise). The flows of influent leave the

inclined plates

62 and 64 at substantially the angle of the

plates

62 and 64 and are believed to aid in sweeping large solid particles from the rotating screen.

Screen cleaning is achieved by means of

supply pipes

90 and 91 having respective groups of

nozzles

92 and 93. The nozzles provide sprays of cleaning fluid through the screen panels. it is desired to clean the screens before they get dirty which can be measured in terms of degradation of the split, for example, down to 90-to-l0.

Turning again to the screen cage, and particularly FIG. 3, preferably the

screen panels

52 and 53 are square and arranged in upper and lower rows as shown. it is also desirable that they be removable for repair or replacement and can be readily locked in place in the screen cage. Channels for receiving the side edges of the

screen panels

52 and 53 are provided by T-brackets 95 which are secured to the bars 48 by threaded

stubs

96 and 97 and respective wing-

nuts

98 and 99. Braces 101 are secured between adjacent ribs 50, and a gasket 102 is affixed onto each brace 101 to form a seal with the top of each respective upper screen panel 52. The side edges of the frame of each screen panel which abuts with the bars 48 may have a bead of resilient material thereon to form a seal between the screen panels and bars 48. A similar bead of material can be used between the lower edge of the frame of panel 52 and upper edge of the frame of panel 53. Each panel includes an angle frame 104 and the screen fabric 105 may be secured thereto with an epoxy adhesive. Exemplary screen fabric is 165 TBC providing 47 percent open area. Metal or synthetic fabrics can be used. Stainless steel fabric has been found suitable. A removable cover 106 may be provided for the top of the screen cage.

The interior of the housing 10 may be vented to the atmosphere. A plate 108 may be attached to the shaft 36 above the cover portions 26 and 27 of the housing. Operation of the screening apparatus causes a higher pressure area toward the periphery of the screen cage 11, and air is drawn in between the plate 108 and cover portions 26-27. This flow of air past the plate 108 can aid in maintaining the

bearings

34 and 35 clean and moisture free. The plate 108 prevents material from splashing onto the bearings from the cover portion 26-27 where the shaft 36 extends therethrough.

The following represent exemplary test data for apparatus as described herein, and as referred to below as a 21 inch deep (high) screen cage with double distributor unit. This unit involved a screen cage of approximately inches in diameter and approximately 21 inches high with two rows of approximately 10% inch square screen panels, with IS panels in each row. Reference to a 16 inch deep screen cage with single distributor unit refers to a similar unit as more particularly described in said application Ser. No. 42,165, involving a single distributor and an approximately 60 inch diameter screen cage having a height of approximately 16 inches.

Tests as indicated in Table I below provide a basic comparison between the l6 inch and 21 inch units. These tests were performed with influent of clear tap water and then with influent containing paper pulp solutions at two separate concentration levels. The paper pulp solutions were made up in a 1300 gallon stock tank employed in conjunction with a hydraulic test stand, and these solutions were re-circulated through the unit. in the test stand operation, influent was continuously pumped into the unit from the stock stank. The unit separates this influent into the effluent, concentrate and splashback streams which were all measured and re-circulated directly back into the stock tank. This enables a steady-state evaluation of the units to be made. The performance of each unit is set forth in Table I below.

TAB LE 1 Combined (oncow Hydraulic Splasliruma, plus Combined tram, split, bat-k, splash, split. Unit influent apm. pun-nut ppm. g.p.|n. litl't'lilll.

(lean water, 2,!00 gpnuum. 3.57 35 WI 5.23 16" deep screen (age with single distributor i ..{ll7 ppm. paper pulp, 2.1m) apin... 143 6.81) 35 17s H. 47 234 ppm. paper pulp. 13,100 ppm 220 Ill. -17 3.5 255 111i (lt'all water, 2.100 ppm [l2 5.33 T llll 5.6" 21"decp scrum! cag with rioulslo distributor... v.{lli' ppm. paper pulp, .',|nl)ii mum... lfiti 7. 42 T 163 7. 7 1 2341).]Ll1l. paper pulp, Lilli) L'.|].ll| 200 l. 52 7 .307 1.35

Additional tests on the 21 inch unit with the double distributor were made. These tests were performed with a re-circulating solution containing approximately 234 parts per million (ppm) by weight of paper pulp, and are set forth below.

Case No. l The deflector 22 for the top distributor 14 was adjusted to its fully raised position (approximately 2 inches above distributor 14). The deflector 21 for the bottom distributor 13 was adjusted vertically so that there was a 58-inch clearance between the outermost lower lip of the deflector and the top of the distributor. The influent to the unit was 2,100 GPM; the concentrate flow measured 210 GPM; the splashback flow measured 7 GPM; and the effluent flow, by the difference, may be taken as 1,883; the hydraulic split was 10.0 percent.

Case No. 2 With the bottom deflector 21 in the same position as for the previous case but with the top deflector 22 moved down 1 inch toward the top distributor, the influent flow remained 2,100 GPM; the concentrate flow became 170 GPM; the splashback remained 7 GPM; and the effluent, again by difference, was 1,923; the split was 8.1 percent.

GPM; the effluent, by difference, was 1,352; and the split was 8.0 percent.

Case No. 6 With other conditions the same as Cases Nos. 4 and 5, the total influent was reduced to 1,000 GPM; the concentrate became PGM; the splashback reduced to 22 GPM; the effluent, by difference, was 903 GPM; and the split was 8.1 percent.

Case No. 7 With the top deflector 22 still lowered 1 inch from its maximum up position, the bottom deflector 21 was placed in service but was lowered with references to Cases Nos. 1 and 2. The bottom apex 107 (FIG. 5) of the cone 87 of the lower deflector 21 was placed one-eighth inch above the top of the pipe 19 associated with the lower distributor 13. With the bottom deflector 21 in this position, the influent was measured at 2,050 GPM; the concentrate measured 160 GPM; the splashback measured 7.6 GPM; the effluent, by difference, was 1,882 GPM; and the split was 7.8 percent. A comparison of Case No. 4 with Case No. 7 indicates that the increased screen area in the cage under test contributes significantly to the overall performance.

Table 11 below provides a summary of Cases 1 through 7 above.

TABLE I1 Eflfluont Combined Concrn- Splas11- (by (111- Hydraulic cone. plus Combined November 24 test lnlluent, trato, back, ferenca), 5 it, splash, s it, ronditions ppm. g.p.m. 51.1mm. g.p.m. percent gpni. porn-n1.

("rrsi-luuwflflun. 2,100 210 7 1,883 10.0 217 10.3 (ass 2 2, 100 170 7 1,023 8.1 177 B. 1 C 11.80 3 2, 100 100 30 1, S .1. 2 220 10. 5 Cast 4 2,100 160 30 1,010 7. T 51. (I (1ase5 1,500 118 30 1,352 8.11 148 0.0 Case 0 1,000 75 22 .103 8. 1 J? l). 7 (Jase 7 2, 050 7.11 1,882 7. 8 168 8. 2

Case No. 3 With the bottom deflector 21 35 Case No. 8 With the machine adjusted as in Case completely closed off so that fluid flow was prevented on the bottom distributor l3 and with the top deflector 22 raised to its original Case No. 1 position so that all of the influent was sent over the top distributor 14 only, the influent measured 2,100 GPM; the concentrate measured 190 GPM; the splashback increased to 30 GPM; the effluent, again by difference, was 1,880; and

No. 7, additional paper pulp was incrementally added to the recirculating test stand fluid. This gave a measure of performance of the unit as a function of influent solids loading, other conditions being held constant.

0 Table [11 below gives the results of this test. P16. 4 is a graph of hydraulic split vs. paper pulp loading for Case No. 8.

TABLE I11 l.p.|n.

paper ivy (1.11.111. (.1.p.m. Hydraulic Combined Sam p10 referent-r wright. in Ur.p.1n. conceit splashsplit, split number influent. influent irate hat-.1; pllt'l llt prrel nt 2315 l, 050 164 7. 6 8. 0 8. 3 321 2. 050 T. 6 .1. 0 .I. 4 4001 J, 100 212 7. 5 10. 1 10. 5 101 l, 100 240 7. 5 11. 4 11. t lilil 2, 1.00 250 8. Ii 13. 3 13. 8 831 2,100 320 x. )s 15. 2 15. 7 1, 000 2, 100 340 .l. 5 10. J 11'). 7 1, 310 2, 100 375 10. 3 17. .J is. 3 1, 701 2, 100 425 12. 0 20. 2 20. b 2, 11 8 2,100 530 13. 3 25. 2 25. .l .I, 100 570 16. 7 .27. l 28. 0

It was observed that the hydraulic split did not deteriorate with time during periods between cleaning cycles. That is, in the absence of grease, the hydraulic split on paper pulp solution appeared to depend upon influent solids loading and to remain constant at a given value for very long periods.

When evaluating this data, it is believed helpful to combine the concentrate with the splashback in order to arrive at a figure for all that material which does not go through the screens and to compare this total with the effluent which does go through the screens in order to arrive at a value for combined hydraulic split. Accordingly, the tables include the value for combined split computed on this basis.

Although exemplary apparatus in accordance with the present invention has been described herein as including two distributors and deflectors, a larger number of the same may be used to increase the hydraulic capacity of the unit. Although an exemplary unit having a diameter of approximately 60 inches and 21 inches high has been described, different sizes may be employed. Likewise, a different number of rows of screen panels and different numbers of panels per row may be used. The exemplary apparatus had a l4 inch diameter pipe l9, inch diameter pipe 20, approximately 17%

inch diameter plates

21 and 22, approximately 10% inch

square panels

52 and 53, and an approximately 0-% inch spacing between the

distributors

13 and 14 at the center aperture thereof.

The present embodiments of this invention are to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims therefore are intended to be embraced therein.

What is claimed is:

1. Screening apparatus comprising support means, and a rotary substantially cylindrical screen structure supported by said support means; drive means coupled with said screen structure for rotating said screen structure,

distributor means supported by said support means and disposed within said screen structure for feeding influent to be screened toward the inner surface of said screen structure, said distributor means comprising at least two vertically spaced distributors for feeding at least two respective vertically spaced groups of influent each as a plurality of substantially discrete streams on and around said inner surface of said screen structure and inclined with respect to the axis thereof, and

feed means extending upwardly into said screen structure for feeding influent to said distributor means, said feed means including pipe means for receiving influent from a source of influent and deflector means positioned with respect to said pipe means for proportioning the influent and deflecting the same downwardly onto said respec tive distributors to form said groups of influent fed onto said inner surface of said screen structure.

2. Screening apparatus as in claim 1 wherein said feed means includes a first pipe member for receiving said influent and supplying a portion of said influent to a first of said distributors, and includes a second pipe member for receiving a portion of said influent and feeding said latter portion to a second of said distributors, and said deflector means includes adjustable deflectors mounted with respect to said first and second pipe members to allow proportioning of the flow of influent onto said distributors.

3. Screening apparatus as in claim 2 wherein said second pipe member is coaxially mounted within said first pipe member, and the first of said deflectors is mounted adjacent an upper end of said first pipe member for deflecting a portion of influent downwardly toward the first of said distributors, and said second deflector is mounted adjacent an upper end of said second pipe means for feeding another portion of said influent downwardly toward the second of said distributors.

4. Screening apparatus as in claim 1 wherein each of the said distributors includes a plurality of inclined plates for forming said inclined streams of influent fed onto said inner surface of said screen structure.

5. Screening apparatus as in claim 1 wherein said screen structure includes a frame having disposed therein a plurality of screen panels, said screen panels being arranged in rows one above the other, each row receiving influent from a respective distributor.

6. Screening apparatus comprising support means, and a rotary substantially cylindrical screen structure having a plurality of screen panels therein, said screen structure being supported by said support means,

drive means coupled with said screen structure for rotating said screen structure,

distributor means supported by said support means and disposed within said screen structure for feeding influent toward the inner surface of said screen structure, said distributor means comprising at least two vertically spaced distributors for feeding at least two respective vertically spaced groups of influent each as a plurality of substantially discrete inclined streams on and around said inner surface of said screen structure, each of said distributors including a plurality of inclined plates for directing said inclined streams onto said inner surface of said screen structure at an angle with respect to the axis thereof, and

feed means extending upwardly into said screen structure for feeding influent to said distributor means, said feed means including pipe means for receiving influent from a source of influent, and said feed means including deflectors adjustably positionable with respect to said pipe means for proportioning the influent and deflecting the same downwardly onto said respective distributors to form said groups of influent fed onto said inner surface of said screen structure.

7. Screening apparatus as in claim 6 wherein the flow rate of each group of influent is proportionable by said deflectors within a range of approximately 5 to 10 feet per second.

8. Screening apparatus as in claim 7 wherein said screen structure has a diameter of approximately 5 feet.

9. Screening apparatus comprising a rotary substantially cylindrical screen structure,

stationary distributor means disposed within said screen structure for feeding influent to be screened toward the inner surface of said screen structure, said distributor means including at least traitsa'izciisattsiaarsssg'assess; at least two respective vertically spaced groups of influent each as a plurality of substantially discrete streams onto said inner surface of said screen structure with said streams being inclined with respect to the axis thereof, and

feed means extending upwardly into said screen structure for feeding influent to said distributor means, said feed means including a first pipe for second deflector means adjustably positionable receiving influent from a source of influent and with respect to an upper end of said second pipe cooperating with a lower of said distributors and for deflecting influent downwardly onto an upper including deflector means adjustably positionable one of said distributors, said pipes and deflector with respect to an upper end of said first pipe for means enabling proportioning of said influent onto deflecting influent downwardly onto said lower of said distributors and formation of said groups of said distributors, and said feed means including a influent. second pipe coaxially mounted with respect to said a a a u a first pipe for receiving influent and including

Claims

1. Screening apparatus comprising support means, and a rotary substantially cylindrical screen structure supported by said support means; drive means coupled with said screen structure for rotating said screen structure, distributor means supported by said support means and disposed within said screen structure for feeding influent to be screened toward the inner surface of said screen structure, said distributor means comprising at least two vertically spaced distributors for feeding at least two respective vertically spaced groups of influent each as a plurality of substantially discrete streams on and around said inner surface of said screen structure and inclined with respect to the axis thereof, and feed means extending upwardly into said screen structure for feeding influent to said distributor means, said feed means including pipe means for receiving influent from a source of influent and deflector means positioned with respect to said pipe means for proportioning the influent and deflecting the same downwardly onto said respective distributors to form said groups of influent fed onto said inner surface of said screen structure.

6. Screening apparatus comprising support means, and a rotary substantialLy cylindrical screen structure having a plurality of screen panels therein, said screen structure being supported by said support means, drive means coupled with said screen structure for rotating said screen structure, distributor means supported by said support means and disposed within said screen structure for feeding influent toward the inner surface of said screen structure, said distributor means comprising at least two vertically spaced distributors for feeding at least two respective vertically spaced groups of influent each as a plurality of substantially discrete inclined streams on and around said inner surface of said screen structure, each of said distributors including a plurality of inclined plates for directing said inclined streams onto said inner surface of said screen structure at an angle with respect to the axis thereof, and feed means extending upwardly into said screen structure for feeding influent to said distributor means, said feed means including pipe means for receiving influent from a source of influent, and said feed means including deflectors adjustably positionable with respect to said pipe means for proportioning the influent and deflecting the same downwardly onto said respective distributors to form said groups of influent fed onto said inner surface of said screen structure.

9. Screening apparatus comprising a rotary substantially cylindrical screen structure, drive means coupled with said screen structure for rotating said screen structure, stationary distributor means disposed within said screen structure for feeding influent to be screened toward the inner surface of said screen structure, said distributor means including at least two vertically spaced distributors each including a plurality of inclined plates for forming and feeding at least two respective vertically spaced groups of influent each as a plurality of substantially discrete streams onto said inner surface of said screen structure with said streams being inclined with respect to the axis thereof, and feed means extending upwardly into said screen structure for feeding influent to said distributor means, said feed means including a first pipe for receiving influent from a source of influent and cooperating with a lower of said distributors and including deflector means adjustably positionable with respect to an upper end of said first pipe for deflecting influent downwardly onto said lower of said distributors, and said feed means including a second pipe coaxially mounted with respect to said first pipe for receiving influent and including second deflector means adjustably positionable with respect to an upper end of said second pipe for deflecting influent downwardly onto an upper one of said distributors, said pipes and deflector means enabling proportioning of said influent onto said distributors and formation of said groups of influent.