Abstract:
An aerobic bacteria waste digester uses a rocking paddle to mix a waste fluid. A pair of spaced-apart inflatables engaged with the paddle and alternately inflated provide buoyancy forces to drive the rocking action. The paddle has two decks and a peripheral skirt. The paddle is of a trestle-type construction with light weight planks forming the decks. The position and motion of paddle surfaces and air bubbled through the fluid from below, is able to enhance bacteria colony growth and thus the rate of bio-mass digestion.

Description:
This application claims date priority of provisional patent application 61/572,083 filed on Jul. 11, 2011 and which is co-pending and incorporates the same subject matter as this application, 61/572,083 and also U.S. Pat. No. 8,133,386 issued on Mar. 13, 2012 and is hereby incorporated by reference herein in their entirety: said application. 
    
    
     BACKGROUND 
     The present disclosure relates to the field of large-scale water treatment, and more particularly to the treatment of aqueous borne waste from municipal, commercial and industrial operations; but is not limited thereto. In patents: U.S. Pat. No. 5,762,418, U.S. Pat. No. 6,029,955, U.S. Pat. No. 6,036,357, U.S. Pat. No. 6,322,056, U.S. Pat. No. 6,554,259, U.S. Pat. No. 6,599,426, U.S. Pat. No. 6,926,437, and U.S. Pat. No. 7,083,324, the present inventor defines apparatus and methods for treating sludge and other materials. The present invention extends this body of knowledge and particularly utilizes the combination of gravity and buoyancy and automated inflation to buoyant elements to assist in mixing for improved efficiency in aerobic bacteria growth in waste digesters. 
     BRIEF SUMMARY 
     It is well known that potable water is essential to healthy living and that in many parts of the world today primary water sources tend to be contaminated by waste waters from domestic effluents, and commercial and industrial operations. It is believed that a large percentage of hospitalizations in emerging countries is due to the human consumption of contaminated water. The present disclosure relates to the treatment of aqueous effluents, especially domestic sewage, using the forces of buoyancy and gravity in digester tanks. These processes use bacteria to consume effluent&#39;s organic waste products and require aggressive mixing for effective results. By using the aforementioned forces relatively little additional energy is required and therefore solar-electrical power becomes a viable alternative for such operations especially in areas where utility-electric power is expensive or absent. Aerobic bacteria are able to obtain the oxygen they need for the digestion processes directly from the aqueous effluent. To operate a practical process the effluent is oxygenated by bubbling oxygen gas or air through the fluid. These gases may be introduced into solution using porous diffusers located at the bottom of the digester tank. Mixing allows more time for oxygen to enter solution and keeps the bacteria, the organic matter and the oxygen evenly distributed throughout the tank. 
     The present disclosure defines an apparatus and its method of use for digesting an organic sludge as an aqueous mixture within a biological digester tank. Mixing of the aqueous mixture is induced by the action of a rocking paddle using the buoyancy force of inflatable sacks such as tire inner tubes in order to produce a cyclic up and down motion of the paddle within the tank. The digesting process uses aerobic bacteria and is accelerated by oxygenation of the organic sludge by injecting an oxygen bearing gas into the digester tank in the form of bubbles which rise from the bottom of the digester tank through the aqueous mixture. 
     In one aspect of the apparatus, the rocking paddle is mounted on a supporting beam so that it is free to move in a see-saw type motion within the aqueous mixture, wherein one end of the paddle moves lower within the aqueous mixture while the other end moves higher and then motion of the ends of the rocking paddle reverse in a continuing cycle. 
     In another aspect of the apparatus, the inflatable sacks are fixedly secured to the paddle so that by alternate inflations they are able to alternately raise first one end and then the opposing end of the rocking paddle by their buoyancy force. 
     In another aspect of the method, an air supply is used to alternately and simultaneously inflate one of the inflatable sacks while deflating the other in a continuously reversing process. The air bleed from one of the inflatable sacks, while it is deflating, is used to inflate the other one of the inflatable sacks and vice-versa thereby reducing the energy required for the inflations. 
     In another aspect of the apparatus, alternately each opposing end of the rocking paddle moves downwardly or falls through the aqueous mixture due to the force of gravity when its inflatable sack is deflated. Since the rocking paddle is a rigid body when one end moves upwardly the opposing end must move downwardly. 
     In another aspect of the apparatus the rocking paddle presents a plurality of surfaces which are oriented to force the rising gas bubbles to move in a lateral motion thereby extending their contact time with the aqueous mixture which improves oxygen absorption and the rate of growth of the bacteria resulting in an improved rate of digestion. 
     These and other aspects may, in various implementations, provide advantages such as: a relatively small capital investment, low operating and maintenance costs, fully automated operation, and high throughput for a given tank size. The details of one or more embodiments of these concepts are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of these concepts will be apparent from the description and drawings, and from the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is an example schematic diagram showing a side-elevational view of a mixing tank. 
         FIG. 2  is an example top plan view of an upper deck of a paddle thereof; 
         FIG. 3  is an example partial view thereof taken at sectional line A in  FIG. 1 ; 
         FIG. 4  is an example perspective view of an alternate mounting and support arrangement of the paddle shown in  FIG. 2 ; 
         FIG. 5  is an example perspective view of a further alternate mounting supported on a side wall of the mixing tank; and 
         FIG. 6  is an example block diagram of an inflation system of the apparatus. 
     
    
    
     Like reference symbols in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     A digester such as the subject apparatus  10  described herein is used for processing an organic aqueous sludge with aerobic bacteria, together referred to herein by the term “mixture  20 .” The process occurs within a digester tank  30 . Air or oxygen gas may be introduced at the bottom of tank  30  so that bubbles of the gas rise though the mixture  20  thereby supporting growth of colonies of the aerobic bacteria to enhance the rate of the digestion process. This is clearly shown and described in the incorporated references. 
       FIG. 1  shows the apparatus  10  which includes a paddle  100 , which may be rotatably mounted within tank  30  in any one of several ways including the embodiments described herein but is not limited thereto. 
     Paddle  100  may be a rigid, elongated metal structure  115  including C-frames  106 , I-frames  108  and interconnecting struts  102  as shown in  FIG. 1 . These elements may be arranged and joined by welding or otherwise to receive planks  220  which may be made of wood or other relatively lightweight material.  FIG. 3  shows typical planks  220  secured by portions of an I-frame  108 . At the right side of  FIG. 1 , the metal structure  115  is shown without planks  220  so as to provide a better understanding of how the structure  115  may be made up. At the left side of  FIG. 1 , the metal structure  115  is shown with planks  220  inserted into the structure  115  as exemplified by  FIG. 3 . The paddle  100  may be made up of the elements shown or may be constructed in an alternate manner as would be known by those of skill in the art. However, an open frame, trestle-like, structure with light weight planks is a superior and highly novel approach providing cost saving and light weight. It should be clear that struts  102  may be made up of L-iron, C-iron, square or triangular tubing, or other structural shapes. Structural engineers will be able to calculate the stresses developed within metal structure  115  and will be able to provide appropriate size, shape, strength, and configuration of the struts  102  in order to achieve a stable and rigid paddle  100 . Many such configurations of the elements and of the overall configuration of structure  115  may be suitable for the intended use described herein. 
     Paddle  100  may include an upper deck  104  which is shown in  FIG. 2  in plan view, and a lower deck  105 . Upper deck  104  is continuous from end to end as shown in  FIG. 2 , while lower deck  105  is medially discontinuous in order to provide clearance for gas bubbles to enter between upper  104  and lower  105  decks providing certain advantages as described below. The application of two decks, an upper continuous deck  104  and a lower discontinuous deck  105  which is positioned below the upper deck  104  in the manner shown in  FIG. 1  is considered to be an important novelty of the present apparatus as will be recognized in the following description of operation. Weights W may be attached at any position on paddle  100  and generally with equal weights on both the left and right sides of paddle  100 . An additional structural element  95  is shown in  FIG. 3  and may be used for mounting an attitude or tilt switch  425  as shown. 
     Paddle  100  is rotationally mounted so as to be able to rock back-and-forth to providing mixing action within mixture  20  as previously described. One or more piers  80 , may be used to support paddle  100  and its means for rocking as generally shown in  FIG. 1 . In one embodiment piers are secured to the bottom of tank  30 . 
       FIG. 3  shows details of an embodiment of the mounting of paddle  100 . Lower plate  92  is mounted to pier  80  and upper plate  98  is mounted to the upper deck  104  of paddle  100 . Between plates  92  and  98  are positioned bearing  90 A which abuts a lower spacer  94 , and an upper spacer  93 . Bearing  90 A may be made up of side-by-side, axially aligned, steel pipe pieces with every other one of the pipe pieces welded to spacer  94 , and  93  respectively. Upper plate  98  is therefore able to rotate about hinge pin  97  both CW and CCW. The spacers  93  and  94  prevent a collision between upper and lower plates  98  and  92  for large rotational angles during rocking action. This hinge structure may be mounted on each of the piers  80  used for supporting paddle  100 , said piers  80  being spaced laterally across paddle  100 . 
       FIG. 4  shows details of an alternate embodiment of the mounting of paddle  100 . Here, rigid, stationary, structural shaft  300  may be fixedly secured to vertical supports  310  reinforced by struts  320  which are positioned at angles to achieve leverage. The shaft  300  may have second bearings  90 B mounted thereon which engage upper plate  98 . Elements  310  and  320  are fixed to lower plate  92 . Therefore, upper plate  98  is able to rock while lower plate remains motionless secured to a pier  80 . In  FIG. 4 , upper plate  98  is shown by phantom line in order to better view details below. 
       FIG. 5  shows details of a further alternate embodiment that may be used for mounting paddle  100 . Here, wall mounted bearings  90 C may be split babbitted journal bearings or may be other types of bearings. In this approach, paddle  100  will be secured rigidly to shaft  300  with both paddle and shaft able to rotate together. Paddle  100  is not shown in  FIG. 5  but may be mounted atop shaft  300 . In this arrangement, no piers  80  or other mountings on the floor of tank  30  are required. 
     Clearly, other types of mounting arrangements may be conceived by those of skill in the art for mounting paddle  100  within tank  30  so that it is able to rock back and forth while it is able to maintain its longitudinal orientation within tank  30 . 
     Arrow “B” in  FIG. 1  indicates motion wherein, as discussed, paddle  100  moves with rocking motion in order to agitate and mix mixture  20 , and especially to assure maximal mutual contact between the sludge and the aerobic bacteria of mixture  20  for improving the speed of the digestion process. Oxygen laden gas bubbles move upward within the tank as disbursed from below and come into contact with paddle  100 . As an example, when the left side of paddle  100  is tilting downwardly by an angle alpha as exemplified in  FIG. 3 , gas bubbles rising up through mixture  20  on the left side of the tank  30  are forced by lower deck  105  to move toward the center of paddle  100  and generally will move into the medial open space of lower deck  105 . Meanwhile, gas bubbles rising up on the right side of paddle  100  will be forced to move at an angle since they are restricted by the right side of the lower deck  105  and will follow the its surface which is tilted upwardly. Taking this angular path causes the gas bubbles to move through the mixture for a longer time and to therefore come into contact with a much larger number of aerobic bacteria. This results in accelerated growth of such bacteria colonies. Also, when the bubbles move into the space between upper and lower decks they are forced to move angularly also by the under surface of the upper deck  104 . The gas bubbles move along the surfaces of both decks  104  and  105  at the same time causing significant quantities of the bacteria to be contacted. 
     As shown in  FIG. 1 , skirts  4  may run along the ends and sides of paddle  100  and tend to herd the rising bubbles under paddle  100 . All of the above herding and directing of the bubbles results in a significant improvement in oxygenation within the mixture resulting in improved growth of the bacteria colonies that provide digestion of bio-products within the mixture. 
     The means for rocking paddle  100 , as disclosed in the referenced documents are inflatables such as bladders  400 A and  400 B, inner tubes, air bags and similar items. Bladders  400 A and  400 B may be fixed to the upper surface of paddle  100  in any practical way at opposite ends thereof as shown by the example dashed lines in  FIG. 2 . A typical placement of one such bladder  400 A is shown in  FIG. 1  at the left end of paddle  100 . Each said bladder, when inflated, provides buoyancy to one end of paddle  100 . By inflating and deflating the bladders in an alternating sequence, the paddle  100  may be caused to tilt downwardly on one side and then followed by the opposing side in a continuous rocking motion. 
     In  FIG. 6  inflatable bladders  400 A and  400 B may be inflated and deflated manually through Schrader valves  410 . 
     During normal operation the bladders alternate between an inflated state and a deflated state with the gas within one of the bladders delivered to the other of the bladders and then from the other of the bladders back to the one of the bladders during each cycle of the paddle  100 . The solid lines in  FIG. 6  represents gas lines or conduits. Attitude sensing tilt switch  425 , which, as said and shown in  FIG. 3 , may be mounted medially on paddle  100  at position  95  is able to sense (determine) when paddle  100  tilts to the left and to the right. The attitude switch  425  provides an electrical signal (dashed lines) to valves  430 A and  430 B which may be, for instance, Snap-Tite 32258-3NB-AR11 solenoid valves. When a bladder is in an extreme downward position, maximum tilt of paddle  100 , air in the other bladder is immediately transferred into the low bladder causing it to achieve a significant buoyancy, raising the low bladder and lowering the high, now deflated, bladder. When the reversal is complete, the air is transferred back to the first bladder and the process repeats. 
     The bladders  400 A and  400 B are located on the paddle  100  as described. The attitude switch  425  is located centrally on paddle  100 , and the pump  420  and valves  430 A and  430 B are typically located to one side of paddle  100  on the ground adjacent to tank  30 . Pump  420  may be an air-pressure driven dual diaphragm pump such as a Price Pump model AOD1 which is driven by a source of air pressure, and is able to continuously provide air pressure at one of its ports and suction at a second one of its ports. Valves  430 A and  430 B are dual action, dual path type valves and are electrically operated so that port  1  of both valves are open at the same time, or alternately, port  2  of both valves are open at the same time. Ports  1  and ports  2  are not open and are not closed at the same time. Ports  3  are always open so that air flows between either ports  1  and  3  or ports  2  and  3 . 
     For instance, now referring to the system shown in  FIG. 6 , and assuming bladder  400 B is inflated and has reached its highest point within mixture  20 , that is, the buoyant force of bladder  400 B has raised the left side of paddle  100  ( FIG. 1 ) to its highest point. At that time attitude switch  425 , being adjusted to sense this position of paddle  100 , electrically switches valves  430 A and  430 B to open their ports  1  and close ports  2  respectively, so that air in bladder  400 B is now sucked by pump  420  through ports  1  and  3  of valve  430 B, through pump  420  and then through ports  3  and  1  of valve  430 A and into bladder  400 A. With bladder  400 B deflated and bladder  400 A inflated, bladder  400 B being at its lowest point within mixture  20 , paddle  100  is caused to rise on its right side by the buoyancy force of bladder  400 A. When bladder  400 A reaches its highest point, i.e., the right side of paddle  100  fully raised, switch  425  closes ports  1  and opens ports  2  of valves  430 A and  430 B. Air in bladder  400 A is then suctioned from bladder  400 A, through ports  2  and  3  of valve  430 B and through pump  420  and then forced by pumping pressure through ports  3  and  2  of valve  430 A and into bladder  400 B which at this time is at its lowest point within mixture  20 . The buoyant force of bladder  400 A causes paddle  100  to reverse positions so that bladder  400 B moves to its highest point and this completes the cycle of paddle motion for mixing mixture  20  said paddle motion repeating this cycle on a continuous basis. 
     A number of embodiments have been described herein. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of this disclosure. Accordingly, other embodiments are within the scope of the following claims.