Abstract:
A fluid treatment system, includes a pressurizable tank, a compressed air source, and a float disposed inside the tank, the float rising or falling in response to a level of fluid in the tank; and a float-actuated switch assembly connected to the float. The float-actuated switch assembly starts introduction of compressed air into the tank from the compressed air source. A purge valve may be provided to allow fluid to flow out of the tank during the introduction of compressed air into the tank. The float-actuated switch assembly may include a magnetic switch.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of Invention 
   This invention relates to a fluid treatment system and method. 
   2. Description of Related Art 
   Contaminants such as iron may be removed from water by dissolving air in the water to facilitate precipitation of the contaminants. One way to introduce air into water is to use an air pump to create a pressurized air head in a closed water tank. The pressurized air head forces air to dissolve in the water. 
   As air is dissolved in the water, the air head is diminished and must be replenished. To replenish the air head, some systems control the air pump using a timer; e.g., the timer causes the air pump to operate at predetermined times, forcing a predetermined quantity of air into the tank. Other systems control the air pump using a pressure switch installed inline before or after the tank, or a flow switch that turns on the air pump when water is flowing. 
   SUMMARY OF THE INVENTION 
   A disadvantage of systems that use a timer, pressure switch or flow switch for air pump actuation is that they do not provide direct control of the air volume. During periods of high water demand, the air pocket, also referred to as “air head,” may be excessively or completely diminished before the next air pump cycle starts. During periods of low demand, such as while occupants of a house are away on vacation, the air pump operates needlessly, thus wasting energy. Furthermore, in such systems, the air pump cycle typically results in excess air being forced into the tank, and the excess air therefore needs to be bled off during or after the air pump cycle. This also wastes energy, and also wastes water because water is bled out of the tank as the air pocket increases. 
   It would be advantageous to have a system and method in which an air pump is actuated based on the water level in the tank, or on the air level in the tank, instead of relying on a timer. This invention provides such a system and method. 
   In embodiments, the invention uses a float-actuated switch assembly, which directly responds to the water level in a water tank, to actuate the introduction of air into the water tank. As used herein, “air” shall encompass not only ambient air, but also any oxygen-rich gas that may be provided from a source other than ambient air, such as from a compressed oxygen-rich gas tank or the like. “Oxygen-rich gas” includes any gas that contains oxygen in an amount effective to reduce contaminants, and thus includes pure oxygen and ozone as well as atmospheric air that is compressed and stored in a tank. “Air” shall also generally encompass any gas that may be used to remove contaminants or otherwise treat a fluid. Thus, while the exemplary embodiments described below use an air pump to introduce air into the tank, the invention is equally applicable to a system in which, for example, air is introduced by controlling a valve to open in order to let compressed air flow into the tank. 
   These and other objects, advantages and salient features of the invention are described in or apparent from the following detailed description of exemplary embodiments. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments of the invention will be described with reference to the drawings, wherein like numerals represent like parts, and wherein: 
       FIG. 1  illustrates an exemplary water treatment system according to the invention; 
       FIG. 2  illustrates an enlarged cross section of a cap and switch assembly according to the invention; and 
       FIG. 3  illustrated another exemplary water treatment system according to the invention. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   This invention uses a water level-responsive switch to initiate replenishment of pressurized air head in a fluid-containing tank. Exemplary embodiments are described in detail below. 
     FIG. 1  illustrates an exemplary water treatment system  10  according to the invention. The system  10  includes a pressurizable water tank  100 , an air pump  200 , and a purge valve  300 . A power source  400  supplies power to the system  10 , and a power supply switch  500  is preferably provided between the power source  400  and the air pump  200 . The power supply switch  500  preferably allows power to be supplied to both the air pump  200  and the purge valve  300 , preferably simultaneously. Thus, in this embodiment, the power supply switch is connected to the air pump  200  via a power supply line  210 , and to the purge valve  300  via a power supply line  310 . The power supply switch  500  is also connected to the power source  400  via a power supply line  510 . 
   Hereafter, it will be assumed that the power supply  400  is a standard AC power outlet, and that the air pump  200  and the purge valve  300  operate on a standard AC current. However, it will be appreciated that DC power may be used instead of AC power, if desired. For convenience in installation, the power supply lines  210 ,  310  and  510  may be electric cords with standard two- or three-prong plugs, and the power supply switch  500  may include two standard receptacles into which the plugs may be inserted. Alternatively, the power supply switch  500  may include a single standard receptacle, and a separate splitter (not shown) may be plugged into the receptacle. 
   Although the purge valve  300  and air pump  200  are depicted and described as being connectable to the same power source and controlled by the same switch device, those skilled in the art will appreciate that the purge valve  300  and air pump  200  may alternatively be connected to separate power sources, and/or may be turned on and off by separate switches. For example, signals from a switch assembly  118 , described in more detail below, may be split and sent to both a switch that controls the air pump  200  and a switch that controls the purge valve  300 . 
   The tank  100  includes a cap  110 , an inlet diffuser  116 , a float  120 , and an outlet tube  130 . Water  140  fills part of the tank, and above the water is formed a pressurized air head  150 . The inlet diffuser  116  sprays and disperses water throughout the air head  150 , thereby providing more water-to-air contact which provides for more effective oxidation. 
   The purge valve  300  may, for example, be a solenoid valve or any other type of valve that is able to be controlled based directly or indirectly on a signal from the switch assembly  118 . The purge valve  300  is normally closed to prevent water from flowing through a purge line  320 . When the purge valve  300  is opened, it allows water to flow through the purge line  320 . The primary purpose of the purge valve  300  is to release water in order to allow more air into the tank  100 . If iron is to be treated (i.e., removed from the water), a filter (not shown) is typically used as part of the system, and the purge valve  300  is preferably installed after the filter. Thereby, the purge valve  300  is always releasing aerated and/or filtered water, and therefore has less chance of being clogged or caused to malfunction by contaminants. 
   Accordingly, in this embodiment, when the power supply switch  500  is energized (as will be described in more detail hereafter), the air pump  200  is energized by the power supply switch  500 , and the purge valve  300  is also energized by the power supply switch  500 , substantially simultaneously with energization of the air pump  200 . Therefore, air is forced by the air pump  200  through air inlet line  220 , through the cap  110  and into the tank  100 , thereby increasing the amount of air in the tank  100 . At the same time, water is forced out through the outlet tube  130 , through the purge valve  300  and out through the purge line  320 . The purge line  320  may lead to an existing drain line, a floor drain, to the outside or to any other suitable discharge point. The flow rate through the purge line  320  is typically about 0.25-1.0 gallons per minute (gpm). 
   It should be appreciated that it is possible that a user may, for example, coincidentally turn on a water faucet  3302  or the like while water is flowing through the purge valve. This does not pose any problem, because water may still flow through the outlet line  330  while the purge valve  300  is open. 
   The cap  110  includes an inlet port  112  and an outlet port  114 , connected to the inlet diffuser  116  and the outlet tube  130 , respectively. The cap  110  also includes an air inlet port  115  to which the air inlet line  220  connects. A switch assembly  118 , described in more detail below, is provided in the cap  110 . 
   Although not depicted in the drawings, it is preferable that check valves, i.e., valves that allow fluid flow in one direction, but not the other, are provided in the air inlet line  220  and in a water inlet line (not shown) that connects to the inlet port  112 . A check valve may also be provided after the purge valve  300  to prevent water from flowing back through the purge valve  300 . 
   It should be appreciated that the system shown in  FIG. 1  may in fact be part of a larger water treatment system including additional tanks for filtering or other processes. For example, one or more filter tanks  3304  may be provided downstream from the tank  100 , to capture particulates of iron or other contaminants precipitated from the water. In such a system, the filter tank(s)  3304  would typically be positioned between the tank  100  and the purge valve  300 . as shown in  FIG. 3 . In systems designed to treat only low levels of hydrogen sulfide, a filter tank may not be needed, and therefore the purge valve  300  would typically be positioned directly downstream from the tank  100  as shown in  FIG. 1 . However, it should be appreciated that the purge valve  300  may be located anywhere in the system, as long as it allows water to escape the tank  100  as air is being pumped into the air head  150 . For example, the purge valve  300  could be located on the tank  100  itself. One or more filter tanks may also be installed as prefilters before the tank  100 . 
     FIG. 2  shows an enlarged cross sectional view of the cap  110 . As depicted, the cap  110  may include a threaded portion  119  by which it is attached to a mating threaded portion (not shown) provided in the top of the tank  100 . The cap  110  may, for example, be formed of a polymeric material such as plastic or resin. In a preferred embodiment, the cap  110  is made of PVC schedule  80 . 
   A float guide  124  may be attached to the cap  110 . A float rod  122 , which has a bottom end that connects to the float  120 , passes through and is slidable within the float guide  124 . A flared fitting  125  may be provided at the lower end of the float guide  124 . The flared fitting  125  can help to reduce the possibility of the float  120  getting stuck if there are contaminants in the water that may adhere to the float rod  122 . 
   A switch actuator  1182 , which is part of the switch assembly  118  (see  FIG. 1 ), is attached to the float rod  122  at or near an upper end of the float rod  122 . The switch actuator  1182  slides up and down within an actuator passage  1188  formed in the cap  110 . An air-tight seal may be formed between the float rod  122  and the bottom end of the actuator passage  1188 , but this is problematic for various reasons and therefore it is preferable that the top end of the actuator passage  1188  be sealed by a threaded plug  1189  or the like, as shown, or permanently sealed by, e.g., not forming the actuator passage  1188  all the way through the cap  110  during formation of the cap  110  (that is, by forming the actuator passage  1188  as a blind bore), or by permanently affixing a cap over the actuator passage  1188  by adhesive, plastic welding or the like. By so doing, it becomes unnecessary to provide an air-tight seal between the float rod  122  and the bottom end of the actuator passage  1188 . One advantage of using a threaded plug  1189  as shown are ease of assembly, and of disassembly for cleaning, if needed. Another advantage is that the plug  1189  allows for fine tuning of the switch actuator height to activate the “ON” switch  1184 , described in more detail below. Thus, the plug  1189  preferably is set to a predetermined depth, which may be determined empirically and then applied to all like systems. 
   When the float rod  122  is at the top of its stroke within the actuator passage  1188 , the switch actuator  1182  actuates an “ON” switch  1184 , and when the float rod  122  is at the bottom of its stroke within the actuator passage  1188 , the switch actuator  1182  actuates an “OFF” switch  1186 . An “ON” signal and an “OFF” signal are transmitted respectively through signal lines  1185  and  1187 . The signal lines  1185  and  1187  together form a signal cable  1181  (see  FIG. 1 ) through which the signals are transmitted to the power supply switch  500 , turning power to the air pump  200  and the purge valve  300  on or off accordingly. The signals may, for example, be sent to a relay (not shown) in the power supply switch  500 , and the relay may accomplish the switching as appropriate. The relay is preferably a latching relay, so that it will keep the air pump  200  running, even after the switch actuator  1182  leaves the vicinity of the “ON” switch  1184 , until the switch actuator  1182  reaches the vicinity of the “OFF” switch  1186 . Alternatively, a microprocessor or the like may be provided within the power supply switch  500  as a controller to receive the “ON” and “OFF” signals, and the microprocessor may control the switching. 
   If desired, the purge valve  300  and purge line  320  may be eliminated in, for example, the following manner. A separate sensor, such as a flow switch, acoustic sensor or the like may be provided to detect flow of water through the outlet line  330 . This sensor would send a signal to the switch of the air pump  200  to indicate whether water was flowing through the outlet line  330 . Actuation of the air pump  200  would then occur when (1) the “ON” signal was received from the switch assembly  118  and (2) when a “water flowing” signal was received from the flow sensor. In other words, when water was flowing because a faucet  3302  or the like was turned on, the system would know that it was possible to force more air into the tank  100 , and therefore would actuate the air pump  220  if the float  120  indicated that more air was needed in the tank  100  at that time. The switching in this case would be slightly more complicated than in the case of using the purge valve  300 , but could still be accomplished by those skilled in the art by using a relay or a microprocessor or the like. 
   The buoyancy of the float  120 , the length of the float rod  122 , and the distance between the switches  1184  and  1186  are preferably selected in such a combination that the water level does not drop below about twenty-seven inches when the air head  150  is at its maximum height, and does not raise above about fourteen inches before the air pump  200  is actuated to recharge the air head  150 . Of course, these distances may change depending on the size, specific requirements or the like of a given system. It has been discovered that a long, slender float  120  is more advantageous than, for example, a short, fat float, for the reason that by using a long, slender float, the distance between the minimum and maximum height of the air head  150  can be made greater than the distance between the switches  1184  and  1186 . As one example, a cylindrical float that is one inch in diameter, eighteen inches in length and has a mass of about 113 g (approximately 4 ounces) enables the distance between the minimum and maximum height of the air head  150  to be as much as twelve inches or more, even though the distance between the switches  1184  and  1186  is only about four inches. This is advantageous because it reduces the cycle time of the air pump  200 . In other words, if there were only a short distance between the minimum and maximum height of the air head  150 , then the air pump  200  would need to be turned on more often to recharge the air head  150 . It is contemplated that the optimum aspect ratio of the float  120 , i.e., the ratio of the float&#39;s diameter to the float&#39;s height, is within a range of from about 1:10 to about 1:30, preferably about 1:15 to about 1:25, and more preferably about 1:18. However, any other desired aspect ratio of the float may still be used within the scope of the invention. 
   In a preferred embodiment, the switch actuator  1182  is a magnet, and the switches  1184  and  1186  are magnetically actuated switches. Thus, the switches  1184  and  1186  may be completely embedded within the cap  100 , and need not be exposed to the atmosphere or to the inside of the tank  100 . However, other embodiments are also possible, such as an embodiment (not shown) in which the switch actuator  1182  is simply a projection projecting from the float rod  122 , and the projection physically contacts the switches, which in this case may be microswitches or the like. 
   Some advantages of the system described above include:
         The system does not require a vent, because air is proportionately added, and overcharging with air will not occur. Therefore, in contrast to water treatment systems that use a vent, there are no problems of leaking or clogged mechanical or electronic vents.   Water exiting from the purge valve is clean, filtered water, and therefore is less likely to cause clogging or malfunctioning of the purge valve.   The introduction of air into the tank is based directly on water level; therefore, it is not actuated too frequently or too infrequently, as is the tendency with timer, flow switch or pressure switch-based systems.       

   While the invention has been described in conjunction with the specific embodiments described above, these embodiments should be viewed as illustrative and not limiting. Various modifications, improvements, substitutes or the are possible within the spirit and scope of the invention. 
   For example, while the cap  110  is shown and described as including the inlet port  112 , the outlet port  114 , the air inlet port  115  and the switch assembly  118 , any or all of these elements may be provided elsewhere, such as in a side or top wall of the tank  100 . However, it is typically much more convenient, in terms of both manufacturing and installation, to include these elements in the cap  110  as shown.