Patent Publication Number: US-6210646-B1

Title: Permanganate feeder for iron filter

Description:
This is a continuation-in-part of Ser. No. 08/606,183, filed on Feb. 23, 1996, which is incorporated herein by reference, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the art of water treatment systems. More particularly, the present invention is directed to an apparatus for dissolving potassium permanganate (KMnO 4 ) crystals in water to produce a uniform saturated potassium permanganate solution and for dispensing the solution to regenerate manganese oxide based iron removal water treatment systems. 
     2. Description of Related Art 
     Iron dissolved in water used for residential and commercial purposes can cause problems which make its removal desirable. For example, water with a high iron content can cause rust stains on clothing and plumbing fixtures and can make food and beverages taste unpleasant. 
     One commonly used method for removing iron from water involves flowing a stream of the water through a mineral bed containing “manganese greensand,” a material consisting of small pebble-like particles coated with manganese oxide (MnO 2 ). The manganese greensand oxidizes the dissolved iron, thereby allowing the iron to precipitate in a solid form which can be filtered out. However, this oxidation process gradually exhausts the water treatment capability of the manganese greensand, so that its ability to remove iron from water becomes degraded. When this occurs, the manganese greensand may be regenerated by exposing it to a solution containing an appropriate oxidizer most commonly potassium permanganate, which process restores its iron removal capability. Typically, the regeneration process is performed automatically at periodic intervals to prevent the mineral bed from ever becoming completely exhausted. 
     Typically, a feeder provides the potassium permanganate solution needed for regeneration. A number of different feeder designs are known. Generally, a quantity of potassium permanganate crystals sufficient to supply many regenerations is placed in the feeder. Water is added to the feeder to dissolve a portion of the potassium permanganate crystals, and the feeder is able to dispense the resulting solution to the iron removal system. 
     For the manganese greensand to be fully regenerated by the regeneration process, it must be exposed to a solution having a sufficient amount of potassium permanganate present therein. This, in turn, means that the feeder must dissolve this sufficient amount of potassium permanganate and dispense the solution to the iron removal system. One way to ensure that a sufficient amount of potassium permanganate is provided for regeneration is to add a known amount of water to the feeder containing potassium permanganate crystals, so that potassium permanganate solution having a known saturation is formed, and then to dispense all of this solution for regeneration. 
     However, it is difficult to form a saturated potassium permanganate solution, and it is especially difficult to achieve a uniform level of saturation with each regeneration as the amount of potassium permanganate crystals present in the feeder decreases. Specifically, in many feeder designs the level of saturation decreases as the amount of potassium permanganate crystals decreases. 
     One way of achieving a more uniform saturation is to wait a long period of time after adding the water to the feeder before dispensing the solution. However, with many iron removal systems this is not possible because the automatic regeneration process applies suction to the feeder to withdraw solution almost immediately after the water is added to the feeder. With such a short amount of time to dissolve the potassium permanganate, it is particularly difficult to provide a uniform saturated solution. 
     The handling of potassium permanganate also presents a number of additional difficulties. Potassium permanganate is very reactive and, over time, tends to corrode or degrade many common materials. It also stains skin, clothing, and other materials and is damaging to the environment. Accordingly, it is crucial that any leakage or spillage of potassium permanganate crystals or solution be minimized. 
     SUMMARY OF THE INVENTION 
     The principal object of the present invention is to provide a feeder which can dispense, as needed, the potassium permanganate solution required to regenerate manganese oxide based iron removal systems. 
     Another object of the present invention is to provide a feeder which is able to receive a quantity of water to dissolve potassium permanganate crystals and which is then able to dispense a sufficiently saturated potassium permanganate solution shortly after this quantity of water has been added. 
     Yet another object of the present invention is to provide a feeder which is able to dispense repeatedly a potassium permanganate solution having a level of saturation which remains uniform even though the amount of solid potassium permanganate present in the feeder decreases with each regeneration. 
     Still another object of the present invention is to provide a potassium permanganate feeder which works reliably over a long period of time. 
     An additional object of the present invention is to provide a potassium permanganate feeder which minimizes the spillage or leakage of potassium permanganate solution. 
     In accordance with the present invention, a potassium permanganate feeder is provided which is able to dispense a uniform saturated potassium permanganate solution for the regeneration of manganese oxide based iron removal systems. An inlet and outlet container are disposed in an outer container, and inlet and outlet tubes are disposed in the inlet and outlet containers, respectively. A common tube is connected at one end to the iron removal system and is connected at the other end to the inlet and outlet tubes of the feeder. An inlet check valve allows fluid to pass through the inlet tube only in the direction toward the inlet container, and an outlet check valve allows fluid to pass through the outlet tube only in the direction away from the outlet container. Potassium permanganate crystals are placed in the outer container in the space between the inlet and outlet containers. The inlet and outlet containers each include a porous barrier in the form of a screen which allows water and solution to pass through but which substantially excludes the passage of the potassium permanganate crystals. 
     When regeneration is required, the iron removal system introduces a quantity of water to the common tube which the check valves direct to the inlet tube. An automatic shut-off valve, such as a float valve, prevents overfilling. The water flows into the inlet container and through the screen to dissolve a portion of the potassium permanganate crystals to form a saturated potassium permanganate solution which then flows into the outlet container. After the quantity of water has been introduced into the feeder, the iron removal system provides a suction on the common tube which closes the check valve in the inlet tube and opens the check valve in the outlet tube. As a result, saturated potassium permanganate solution is drawn into the outlet tube to supply the iron removal system through the common tube. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic representation of the potassium permanganate feeder in accordance with the present invention. 
     FIG. 2 is a schematic representation of an iron removal system which would be used with the potassium permanganate feeder of FIG.  1 . 
     FIG. 3 is a partially cut away and partially exploded view of the potassium permanganate feeder of FIG. 1 in accordance with the present invention. 
     FIG. 4 is a partially cut away view of the potassium permanganate feeder of FIG. 1 in accordance with the present invention with the cover removed. 
     FIG. 5 is a cross-sectional view of the screen assembly of the potassium permanganate feeder in accordance with the present invention shown in FIG. 3 taken along line  5 — 5 . 
     FIG. 6 is a sectional view of the tee connector and inlet check valve of FIG. 1 in accordance with the present invention. 
     FIG. 7 is a sectional view of the elbow connector and outlet check valve of FIG. 1 in accordance with the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to FIGS. 1,  3 , and  4 , the potassium permanganate feeder in accordance with the present invention comprises an outer container  12 , which preferably includes a cover  14 , and in which are disposed an inlet container  16  and an outlet container  18 . Inlet container  16  comprises an upper cylindrical portion  19  and a cylindrical screen assembly  23  which depends therefrom. Outlet container  18  comprises an upper cylindrical portion  20  and a cylindrical screen assembly  24  and is preferably of identical construction to inlet container  16 . Upper cylindrical portions  19  and  20  are preferably made out of a structural material which does not react with potassium permanganate, such as polyvinyl chloride. Upper cylindrical portions  19  and  20  are preferably each fitted with a cover  22 . 
     With reference to FIG. 5, screen assembly  24  comprises a cylindrical screen  26  which is fitted with atop seal  28  and a bottom seal  30 . Fitted in bottom seal  30  is a circular screen  32 . Top seal  28  is fitted over upper cylindrical portion  20  to join screen assembly  24  thereto. 
     Screens  26  and  32  have a mesh size small enough to prevent most of the potassium permanganate crystals from passing through but large enough to allow water and potassium permanganate solution to pass through. Mesh sizes in the range of 100×100 to 200×200 are found to be preferable, and a mesh size of 100×100 is most preferable. Screens  26  and  32  are preferably made out of a 300 series stainless steel, which has been found to be highly resistant to corrosion potassium permanganate. Top seal  28  and bottom seal  30  are preferably made out of an elastomeric material which is not degraded by potassium permanganate, such as a silicone rubber or a fluoroelastomer rubber. 
     Inlet container  16  and outlet container  18  are each supported in feeder  10  by attaching upper portion  20  to outer container  12  by means of a bolt  34  and a wing nut  38 . Bolt  34  passes through a mounting hole  36  in outer container  12  and a corresponding mounting hole (not shown) in upper portion  19  or  20 . In this way, inlet container  16  and outlet container  18  are advantageously supported at the top by bolt  34 , rather than at the bottom by screen assembly  24  which, because of the fine mesh size of screen  26 , may have very little strength. 
     With reference to FIGS. 1,  3 , and  4 , feeder  10  is provided with a common tube  40  which extends from the outside of outer container  12  to the inside through a notch  42 . Common tube  40  further extends to the inside of inlet container  16  through a notch  44  in upper portion  20  to tee connector  46 . An intermediate tube  48  extends from tee connector  46  through a notch  50  and further extends into outlet container  18  through a notch  52  to an elbow connector  54 . 
     An inlet tube  56  is connected to tee connector  46  via an inlet check valve  58 , and an outlet tube  60  is connected to elbow connector  54  via an outlet check valve  62 . Inlet tube  56  is connected to a float valve  64 , which includes a float  66  mounted on a stem  68  slidably connected to a guide  69  and a main valve body  70  having an outlet port  71 . Outlet port  71  is in fluid communication with inlet tube  56 . Float  66  floats on the surface of water, so that float  66 , and stem  68  attached thereto move up or down as the water level moves up or down. Stem  68  extends into main valve body  70  through outlet port  71 . As stem  68  moves up or down with the water level, outlet port  71  is closed opened, respectively. In particular, when the fluid level increases to a predetermined level, outlet port  71  of float valve  64  closes up. 
     Outlet tube  60  ends in a filter assembly  72 , which includes a flared connector  74  and a filter screen  76 . Filter screen  76  has a mesh size which is preferably coarser than the mesh size used in screen  24 , such as 50×50 mesh. Filter screen  76  is preferably made out of a 300 series stainless steel and is preferably much wider than the diameter of outlet tube  60 . Preferably, filter assembly  72  is placed near the bottom of outlet container  18 . 
     With reference to FIGS. 3 and 4, outer container  12  has an overflow outlet hole  78  below the level of mounting holes  36  and notch  42 . A hose adapter  80  is sealed to overflow outlet hole  78  via a grommet  82 . A hose  84  may be attached to hose adapter  80  and may be directed to a drain (not shown). 
     As shown in FIG. 6, inlet check valve  58  is preferably connected directly to tee connector  46  and operates by means of a ball  84  entrained between a screen  86  and an O-ring  88 . Ball  84  is made out of a material which floats on water, such as hollow polypropylene. When either a vacuum is applied to inlet check valve  58  from above or the water level below is high enough, ball  84  is urged against O-ring  88 , thereby closing inlet check valve  58 . However, when water pressure is applied to inlet check valve  58  from above, ball  84  is pushed away from O-ring  88 , thereby opening inlet check valve  58 . 
     As shown in FIG. 7, outlet check valve  62  is preferably connected directly to elbow connector  54  and operates by means of a ball  90  entrained between a screen  92  and a neck  94 . Ball  90  is made out of a resilient material, such as rubber, which sinks in water. When water pressure is applied to outlet check valve  62 , ball  90  is urged against neck  94 , thereby closing outlet check valve  62 . Even when no pressure is applied from above, outlet check valve  62  is closed because gravity holds ball  90  against neck  94 . However, when even a slight vacuum is applied to outlet check  62  from above, ball  90  is pulled off neck  94 , thereby opening outlet check valve  62 . 
     With reference to FIG. 2, a representative iron removal system  200  which may be used with potassium permanganate feeder  10  is shown schematically. Iron removal system  200  includes a tank  202  which holds a filter bed  204  of a material such as manganese greensand. Tank  202  includes a pipe  206  from which fluid may be introduced at the top of filter bed  204  and a central pipe  208  which extends to near the bottom of filter bed  204 . Iron removal system  200  is provided with a source pipe  210  which is connected to a source of raw or unfiltered water (not shown), a destination pipe  212  which is connected to a destination for the treated water (not shown), and a drain pipe  214  which is connected to a drain (not shown). Common tube  40  connects iron removal system  200  to feeder  10 . 
     A top tank  202  is a rotary valve  216  which has a nozzle and venturi system  218 . Rotary valve  216  is connected to pipes  206 ,  208 ,  210 , and  212  and to common tube  40  via nozzle and venturi system  218  and is able to interconnected these fluid pathways in various ways described hereafter. 
     When iron removal system  200  is in service treating water, rotary valve  216  is configured to direct raw water from source pipe  210  to pipe  206  so that it flows through mineral bed  204  for iron removal. The treated water is then directed up central pipe  208  to destination pipe  212 . 
     When regeneration of filter bed  204  is required, iron removal system  200  undergoes several steps, including a fill step in which water is sent to feeder  10  and a solution draw step, following immediately thereafter, in which potassium permanganate solution is withdrawn from feeder  10 . In the fill step, rotary valve  216  is configured so that iron removal system  200  continues to treat water as when it is in service, except that some of the treated water from central pipe  208  is directed to common tube  40  so that it enters feeder  10 . In the solution draw step, rotary valve  216  is configured so that part of the raw water from source pipe  210  is sent directly to destination pipe  212  and part of it is directed through nozzle and venturi system  218 . This passage of water through nozzle and venturi system  218  creates a suction on common tube  40  so that potassium permanganate solution is withdrawn from feeder  10 . The potassium permanganate solution enters nozzle and venturi system  218 , where it is mixed with the flow of raw water there to become a more dilute solution. Typically, the potassium permanganate solution is roughly half as saturated after it flows through nozzle and venturi system  218 . From nozzle and venturi system  218 , the solution is directed to central pipe  208 . The solution flows downwardly through central pipe  208 , exits at the bottom of central pipe  208 , and then flows upwardly through mineral bed  204 . In this way, mineral bed  204  is exposed to potassium permanganate solution to regenerate it. After flowing through mineral bed  204  to regenerate it, the solution enters pipe  206  where it is directed to drain pipe  214  for removal. 
     To prepare feeder  10  for use, a quantity of potassium permanganate crystals  100  is placed in outer container  12  between inlet container  16  and outlet container  18 , as shown in FIG.  1 . As described above, the process of regenerating iron removal system  200  begins with the fill step, whereby iron removal system  200  supplies fill water to feeder  10  via common tube  40 . From common tube  40 , the fill water travels through tee connector  46  and then through intermediate tube  48  to elbow connector  54 . The pressure of the fill water opens inlet check valve  58  and closes outlet check valve  62 . With inlet check valve  58  open, the fill water travels down through inlet tube  56  and exits from outlet port  71  to fill inlet container  16 . The fill water from inlet container  16  slowly passes through screen assembly  23  to reach the quantity of potassium permanganate crystals  100 . The fill water dissolves a portion of the quantity of potassium permanganate crystals  100  to form a potassium permanganate solution, and the solution passes through screen assembly  24  to fill outlet container  18 . 
     During the solution draw step, which immediately follows the fill step, iron removal system  200  applies a vacuum to common tube  40 , which is communicated to inlet check valve  58  and outlet check valve  62 . The vacuum closes inlet check valve  58  and opens outlet check valve  62 , as described above. With outlet check valve  62  open, the vacuum draws up solution from outlet container  18  into outlet tube  60  via filter assembly  72 . From outlet tube  60 , the solution is drawn into iron removal system  200  through common tube  40 . Filter screen  76  of filter assembly  72  serves to prevent large particles which may damage iron removal system  200  from being drawn up into outlet tube  60 . 
     Screen assembly  23  on the inlet container  16  and screen assembly  24  on the outlet container  18  serve two important functions in the present invention. First, screen assemblies  23  and  24  isolate potassium permanganate crystals  100  from the locations where fill water is introduced into feeder  10  and where the solution is withdrawn from feeder  10 , so that the crystals will not cause blockages and will not be withdrawn from feeder  10  into iron removal system  200 . Second, screen assemblies  23  and  24  serve to distribute the flow of water uniformly over a large surface area. As a result, the flow of water through potassium permanganate crystals  100  is widely and uniformly distributed, and the dissolution of the crystals is enhanced. It has been found that the resulting potassium permanganate solution which collects in outlet container  18  is highly saturated. Moreover, it has been found that the saturation level of the potassium permanganate solution formed in feeder  10  remains relatively uniform, even after the amount of potassium permanganate crystals has been greatly reduced after successive regenerations. 
     Feeder  10  is also provided with several safety features in order to minimize leakage or spillage of potassium permanganate solution. If the level of water or solution in outer container  12  becomes too high, the excess will exit through outlet hole  78  and may be directed to a drain (not shown) by hose  84 . Although such drainage prevents spillage or leakage of potassium permanganate solution, it is undesirable because of the adverse environmental effects of potassium permanganate solution. To prevent overfilling of feeder  10  from occurring in the first place, float valve  64  automatically shuts off the flow of water into inlet container  16  when the fluid level has reached a predetermined level. Preferably, this predetermined fluid level is set at a level below that of outlet hole  78 . Although the use of float valve  64  is particularly convenient, other types of automatic shut-off valves could be used. 
     The above described embodiments are merely illustrative of the features and advantages of the present invention. Other arrangements and advantages may be devised by those skilled in the art without departing from the spirit and scope of the present invention. Accordingly, the invention should not be deemed to be limited to the above detailed description but only by the claims that follow.