Patent Publication Number: US-2005126993-A1

Title: Aerator alarm unit

Description:
BACKGROUND OF THE INVENTION  
      This invention relates generally to aeration of sewage. More particularly, this invention relates to the treatment of sewage discharged from houses and other buildings which are not connected to a municipal sewer system, in which aerobic microorganisms within a stand-alone sewage treatment device are stimulated to process the sewage so that it is cleaned to a level acceptable for discharge into the environment. The present invention of the Aerator Alarm Unit (“AAU”) ensures effective aeration of the sewage, so that the aerobic microorganisms have the necessary elements for sewage treatment. Thus, the Aerator Alarm Unit, working in conjunction with a sewage treatment tank, provides an effective means for disposing of sewage produced by buildings outside of a local municipal sewer system.  
      There are several versions of conventional sewage treatment tanks which use aerobic microorganisms to break down sewage. One such device is seen in U.S. Pat. No. 5,549,818. This conventional sewage treatment device consists of a cylindrical tank which encompasses a funnel-shaped clarifier. The clarifier divides the cylindrical tank into an outer chamber, between the outer wall of the tank and the clarifier, and an inner chamber, inside the clarifier. Air is introduced into the outer chamber by multiple air droplines, which are connected to an air compressor and which pump air bubbles into the sewage in the outer chamber. Sewage flows into the outer chamber where it comes in contact with the air bubbles. The introduction of air facilitates the breakdown and digestion of the sewage by aerobic microorganisms present in the sewage. The aerated sewage then proceeds into the clarifier through an opening at the bottom of the funnel-shaped clarifier. Inside the clarifier is a quiescent zone. This area of calm in the inner chamber of the device allows for settling to occur, with the solids falling back out of the clarifier and collecting on the bottom of the treatment tank. Accordingly, the waste water becomes cleaner as it progresses upward in the funnel-shaped clarifier, continuing to allow gravity to separate the solids from the water. So, by the time the sewage has progressed up through the clarifier, it has been substantially cleaned. This treated effluent exits near the top of the clarifier and is discharged. This aerobic clarification process has also been combined with additional cleaning stages, such as in an earlier invention by the present inventors set forth in U.S. Pat. No. 6,228,258.  
      Alternatively, multi-tank aerobic sewage treatment devices which do not employ a clarifier also exist. For example, a diffusion bar aerobic treatment plant was earlier described by the present inventors in patent application Ser. No. 10/222,600. These prior patents by the present inventors are fully incorporated herein, as they provide additional details concerning the types of aerobic sewage treatment devices with which the present invention may be used. Obviously, these descriptions are merely illustrative, and do not limit the scope of the Aerator Alarm Unit described herein. The Aerator Alarm Unit is fully functional with any aerobic sewage treatment device.  
      While current aerobic sewage treatment devices employ some sort of aeration unit, they do not include an incorporated monitor which ensures that the aerator is functioning properly. It is critically important that the aerator unit on an aerobic sewage treatment device operate properly, since the device depends on the action of aerobic microorganisms to break-down the sewage. Aerobic microorganisms cannot perform this work unless the oxygen/air level within the sewage is maintained at the appropriate level. More specifically, if the oxygen/air level in the sewage drops too low, then the aerobic microorganisms will begin to die, and there will not be a sufficient number of microorganisms to effectively process the sewage flowing through the device. Another possible aerator problem would be any sort of condition that might cause damage to the physical mechanism of the aerator, since this could cause a complete loss of oxygen/air flow to the aerobic microorganisms (since this would, again, result in the inability of the aerobic sewage treatment device to process sewage effectively). The AAU is superior to existing aeration means because it incorporates sensing and alarm elements in conjunction with the aerator, to ensure both 1) that the sewage treatment device receives adequate aeration for effective sewage treatment and 2) that the aerator does not experience conditions that might damage its operating mechanisms. By monitoring the pressure between the aerator and the sewage treatment device, the AAU can effectively warn the user/owner of a problem concerning either the sewage treatment device or the aerator.  
      Currently available sensor arrangements do not accomplish these two related goals. Instead, the currently available sensors focus on detecting high-water within the sewage treatment device. The standard current industry arrangement for detection of a high water condition is to use a mercury encapsulated switch inside of a floating vessel or a mechanical weight—operated switch inside of a floating vessel to detect the high water condition. The vessel with the switch inside will rise with the level of the water and will eventually close the mercury switch, causing an electrical path back to an alarm circuit. So, while these sensors can detect a sewage overflow situation, they do not monitor to ensure effective aeration within the sewage treatment device, and they do not actually monitor the backpressure to the aerator to protect against damage to the aerator from excessively high pressure.  
      The present invention of the Aerator Alarm Unit is superior to existing technology because it uses a single device to monitor both the aerator and the sewage treatment device. The AAU incorporates a sensor-alarm panel with an aerator unit (which uses a compressor to pump air into the sewage treatment device), replacing and upgrading the separate and distinct (as well as more limited) sensor technology currently available with an integrated and compact unit. The sensor-alarm panel typically includes both a high and low pressure sensor, and one or more alarm elements. The alarm elements can be, for example, audible and/or visual, with an audible sound alarm and/or a visual light signal activated if the sensor panel monitors a potentially problematic situation. Typically, the sensor-alarm panel is set up to monitor for high pressure, while also monitoring for low (or even no) pressure. Thus, the alarm will activate whenever the air pressure in the air supply tube between the aerator and the aerobic tank of the sewage treatment device falls below or rises above normal operating pressures. This ensures that the aerator provides an adequate air supply to the aerobic sewage treatment device (while also ensuring that the aerator will not be damaged due to excessively high pressure buildups), by continuously monitoring the air pressures and activating an alarm to notify the owner/operator should a potential problem be detected.  
      The AAU has many advantages over the currently available sensors. First, the AAU senses for a low pressure situation, to ensure that the aerator is providing sufficient aeration to the sewage treatment device, while simultaneously sensing for a high pressure situation, to ensure that the aerator mechanism will not be damaged. The high pressure sensor may also act to alert the user/owner in the event of a high water situation. Thus, the AAU simultaneously monitors both the aerator and the sewage treatment device. In the AAU, the sensor mechanisms are all located outside of the sewage treatment device, increasing the reliability and lifespan of the sensors (since they are not exposed to the unfavorable environmental conditions inside the tank and may be maintained and repaired more easily). This is another significant improvement over current sensor technology. Finally, the compact nature of the AAU is an improvement, since it simplifies installation and reduces the chances of problems in linking components. So in a multitude of ways, the AAU is superior to the current state of the art.  
     SUMMARY OF THE INVENTION  
      The Aerator Alarm Unit (“AAU”) is a device which comprises an aerator (for pumping air/oxygen into the aerobic sewage treatment device), as well as a sensor-alarm panel. These two elements are most typically designed to operate independently, so that the aerator will continue to pump air/oxygen to the sewage treatment device regardless of whether or not the sensor alarm panel has monitored conditions outside of the normal operating range (although in an alternative embodiment, the aerator could connect to the sensor alarm panel via a kill switch, such that the aerator would be deactivated if the alarm had run for more than a pre-set amount of time without being manually deactivated). For the sake of efficiency, in the preferred embodiment both the aerator and the sensor-alarm panel would typically operate based on a single power source, and would be attached in close proximity (either within a single housing or with the sensor-alarm panel housing mounted upon the housing for the aerator).  
      The aerator is essentially an external air compressor unit, which acts to pump the air necessary for aerobic treatment of sewage in an aerobic sewage treatment device. The sensor alarm panel includes sensor elements and alarm elements. The sensor elements are designed to monitor operating conditions, and to activate the alarm elements in the event that conditions outside of the normal operating conditions are detected. In the preferred embodiment, the sensor elements monitor high and low air pressure. Thus, the alarm elements would be activated whenever the air pressure from the aerator to the sewage treatment device falls below or rises above normal operating conditions.  
      For example, if the sensor elements detect that the aerator is failing to maintain pressure (which might indicate a break in the supply line or a mechanical failure concerning the aerator, causing low pressure), then the alarm elements would activate. Or if the sensor elements detect that there is high pressure (which could be caused, for example by high water in the sewage treatment device blocking the inlet and/or outlet pipes into the aerobic tank of the sewage treatment device, or by blockage of the diffuser/air supply line), then the alarm elements would activate. In this way, the alarm warns the user if the sewage treatment device needs immediate attention in order to (1) function properly so that clean sewage is discharged (preventing pollution/contamination due to inadequate aerobic treatment of sewage) or (2) prevent damage to the aerator powering the aerobic sewage treatment device (so that the aerobic sewage treatment device continues to operate over time and will not malfunction, and so that the aerator&#39;s life is extended).  
      An optional element available on the preferred embodiment is a switch which allows the Aerator alarm Unit to be set for different modes. The first switch setting places the Aerator Alarm Unit in test mode. Test mode activates the alarm(s), enabling the user to ensure that the alarms are functioning properly. The second switch setting places the Aerator Alarm Unit in run mode. This is the normal operation mode for the AAU (in which it monitors the pressures and activates the alarm if necessary). The third switch setting places the Aerator Alarm Unit in mute mode. This mode disconnects the audio alarm, so that the AAU runs as normal but will only activate the remaining alarm elements (for example, visual alarm elements). In the preferred embodiment, the alarm elements include both an audible alarm and a visual alarm. So, for example, in mute mode, the Aerator Alarm Unit would activate only the visual alarm if the sensor elements monitor pressures outside of the normal range.  
      Typically, the Aerator Alarm Unit would mount atop the sewage treatment unit that it services, so that if the sewage treatment device is buried underground, the Aerator Alarm Unit would project up above the surface. Alternatively, it could be placed elsewhere at some location above ground (and connected to the sewage treatment device via an extended air supply line), while the entire sewage treatment device is buried beneath the surface of the ground. Regardless, the Aerator Alarm Unit must have some access to an open ventilation source, from which it can draw its air supply.  
      By using a sensor-alarm panel that operates by monitoring the aerator, several important goals may be accomplished. First, the sensor-alarm panel will typically be housed in association with the aerator itself, above ground and external to the sewage treatment device aerobic tank. This design allows for effective monitoring of the sewage treatment device&#39;s effectiveness without the need to place the sensor elements within the harsh environment of the sewage treatment device aerobic tank. By removing the sensor elements from the inside of the sewage treatment device aerobic tank and instead placing them outside the tank in conjunction with the aerator, the reliability and lifespan of the sensor elements is increased because there is less chance of 1) environmental erosion affecting the sensor elements and/or 2) damage or deterioration to the wiring between the sensor elements and the alarm. Furthermore, the sensor-alarm panel and aerator of the present invention function in a cooperative manner, since this design improves the lifespan of the aerator while also allowing the sensor-alarm panel to directly monitor the performance of the critical aerator element as well as the overall functioning of the sewage treatment device. In other words, this integrated design provides additional monitoring capability.  
      Placing the sensor elements outside of the aerobic tank of the sewage treatment device in association with the aerator also simplifies periodic maintenance and testing of the alarm elements. Since the alarm elements in the present invention are located above ground, ease-of-access is greatly improved. Finally, it is much easier to retrofit existing sewage treatment devices to add in sensing/alarm capabilities using this unit (rather than using float switch technology or other such means), since the sewage treatment device itself does not have to be opened up and altered internally. Instead, the standard aerator for existing aerobic sewage treatment devices can simply be replaced with an entirely new Aerator Alarm Unit, or a sensor-alarm panel could even be connected to the existing standard aerator in a retrofit. Regardless of retrofit technique, it would be relatively straightforward to use prepackaged equipment in order to improve an existing aerobic sewage treatment device in the manner set forth herein by the applicants by adding an external monitor and alarm in connection to the aerator.  
      When the Aerator Alarm Unit is installed for use with an aerobic sewage treatment device, the AAU pumps air into the aerobic tank of the sewage treatment device via an air feed tube. The air feed tube distributes air to whatever mechanism is in place within the aerobic tank of the sewage treatment tank (such as a diffuser or air droplines), so that air will be emitted out into the aerobic tank, aerating the sewage. Injecting air into the sewage activates and stimulates the aerobic microorganisms in the sewage, which causes the aerobic microorganisms to multiply and increases the amount of sewage that they digest. This aerobic process eliminates sewage contaminants to a great extent, cleaning the sewage.  
      As the aerator of the AAU operates, the sensor-alarm panel monitors the air pressure in the tube between the aerator and the sewage treatment tank. In normal run mode, the AAU will pump air continuously down into the sewage treatment tank. If the sensor alarm panel monitors a problem (either high or low pressure outside of the normal operating range), then the alarm elements will be activated to notify the owner/user of a potential problem so that they can check the situation and call for repair service if necessary. In this manner, the AAU keeps the aerobic sewage treatment device operating effectively (by ensuring that it has the appropriate amount of air necessary for aerobic sewage treatment) and improves the operable lifespan of the aerator (by allowing quick maintenance to keep the proper conditions for durable aerator operation).  
      It is an object of the present invention to aerate sewage in preparation for discharge. In doing so, this invention operates in conjunction with an aerobic sewage treatment device in order to facilitate aerobic microorganisms breaking down sewage. It is another object of this invention to monitor the air pressure between the aerator and the sewage treatment device. It is yet another object of this invention to monitor for high and low pressure. It is still another object of this invention to notify the user/owner whenever it senses conditions outside of the normal operating range. It is still another object of this invention to employ both audible and visual alarm elements for notifying the user/owner. It is still another object of this invention to be easy to install. It is still another object of this invention for it to simplify periodic maintenance and testing, and to provide an easy method of retrofitting existing aerobic sewage treatment devices. It is still another object of this invention to provide a test mode, allowing the user/owner to test the functioning of the alarm elements.  
      It is yet another object of this invention to locate the aerator, sensor elements, and alarm elements above ground and external to the sewage treatment device. It is yet another object of this invention to increase the lifespan of the aerator. It is yet another object of the present invention to improve the effectiveness/efficiency of an aerobic sewage treatment tank. It is still another object of this invention to prevent damage to the aerator of a sewage treatment device. It is still another object of this invention to provide aeration capabilities and sensor-alarm capabilities in a single, compact unit. It is still another object of this invention to be used in conjunction with existing aerobic sewage treatment devices to produce discharge water which meets or exceeds national (as well as state or local) water quality requirements. These and other objects will be apparent to those skilled in the art field. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
      Reference will be made to the drawings where like parts are designated by like numerals and wherein:  
       FIG. 1  is a cut-away side view, showing the AAU located atop a sewage treatment device;  
       FIG. 2  is a cut-away side view, showing the AAU connected to a sewage treatment device via an extended air supply line;  
       FIG. 3  is a side view of the AAU, showing the sensor-alarm panel attached to the aerator via a bracket;  
       FIG. 4  is a top view of the AAU;  
       FIG. 5  is a front view of the AAU; and  
       FIG. 6  is a schematic diagram of the electrical circuit of the preferred embodiment of the AAU, demonstrating the interconnected electrical nature of the sensor-alarm panel and the aerator.  
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT  
      The Aerator Alarm Unit (“AAU”)  10  is a device which comprises an aerator  20  (for pumping air/oxygen into the aerobic sewage treatment device  40 ), as well as a sensor-alarm panel  30 . These two elements are most typically designed to operate independently, so that the aerator  20  will continue to pump air/oxygen to the sewage treatment device  40  regardless of whether or not the sensor alarm panel  30  has monitored conditions outside of the normal operating range (although in an alternative embodiment, the aerator  20  could connect to the sensor alarm panel  30  via a kill switch, such that the aerator  20  would be deactivated if the alarm had run for more than a pre-set amount of time without being manually deactivated). However, for the sake of efficiency, in the preferred embodiment both the aerator  20  and the sensor-alarm panel  30  would typically operate based on a single power source, and would be attached in close proximity (either within a single housing or with the sensor-alarm panel  30  housing mounted upon the housing for the aerator  20 ).  
      The aerator  20  is essentially an external air compressor unit, which acts to pump the air necessary for aerobic treatment of sewage in a sewage treatment device  40 . In the preferred embodiment, for example, the aerator  20  functions as set out by NSF/ANSI  40  standard for aerobic treatment units. The sensor alarm panel  30  includes sensor elements and alarm elements. The sensor elements are designed to monitor operating conditions, and to activate the alarm elements in the event that conditions outside of the normal operating conditions are detected. In the preferred embodiment, the sensor elements monitor high and low air pressure. Thus, the alarm elements would be activated whenever the air pressure from the aerator  20  to the sewage treatment device  40  falls below or rises above normal operating pressure conditions.  
      For example, if the sensor elements detect that the aerator  20  is failing to maintain pressure (which might indicate a break in the supply line or a mechanical failure concerning the aerator  20 , causing low pressure), then the alarm elements would activate. Or if the sensor elements detect that there is high pressure (which could be caused, for example by high water in the sewage treatment device  40  blocking the inlet and/or outlet pipes into the aerobic tank of the sewage treatment device  40 , or by blockage of the diffuser and/or air supply line), then the alarm elements would activate. In this way, the sensor-alarm panel  30  warns the user if the sewage treatment device needs immediate attention in order to (1) function properly so that clean sewage is discharged (preventing pollution/contamination due to inadequate aerobic treatment of sewage) or (2) prevent damage to the aerator  20  powering the aerobic sewage treatment device  40  (so that the aerobic sewage treatment device  40  continues to operate over time and will not malfunction, and so that the aerator&#39;s life is extended).  
      Normal operating conditions will vary depending upon the needs of the particular aerobic sewage treatment device  40  at issue. Obviously, the low end of the normal operating condition range should be set based on the minimum sufficient air pressure that must be provided to the aerobic sewage treatment device  40  in order to effectively aerate the sewage (so that the aerobic microorganisms will have sufficient air to break down the sewage). Persons skilled in the art field will understand and be able to determine this minimum pressure level for a particular sewage treatment device  40 . In fact, the particular sewage treatment device  40  at issue typically defines this pressure level within its instruction materials. Factors which might affect the appropriate minimum pressure level would include the size/volume of the tank to be aerated, column inches of water pressure, the depth of the aerobic tank, the sewage flow rate through the aeration tank (i.e. the amount of time that the sewage spends in the tank), and the size of the air discharge holes in the diffuser or air droptubes (since the air pressure must be sufficiently high to keep water out of the discharge holes, so that water cannot enter the air supply line  45 ).  
      The high end of the normal operating condition pressure range could be set based on the lower of two factors: 1) the back-pressure exerted whenever the sewage in the aeration tank of the sewage treatment device  40  is in an overflow condition, or 2) the back-pressure level (due to blockage, etc.) which will result in structural damage to the aerator  20  itself (which likely would be set forth in the instructions included with the aerator  20 ). Obviously, the back-pressure for an overflow situation need not be used, if the main concern is merely protecting the aerator  20  from damage; by taking this overflow back-pressure into account, however, the high pressure level sensor further monitors the condition of the sewage treatment device  40 . Accordingly, the actual normal operating range for the AAU  10  must be set at the time it is connected to the sewage treatment device  40  it will service (unless, of course, the particular AAU  10  is specifically designed for use with a particular sewage treatment unit  40 ).  
      Typically, then, the normal operating range for the preferred embodiment would be infinitely adjustable, so that the high and low pressure levels (for the normal operating condition range) could be set anywhere between 0-5 pounds per square inch (above atmospheric pressure; i.e. positive pressure). Clearly, this range for the preferred embodiment is not limiting, and could vary depending on the needs of the particular sewage treatment device  40  being serviced. The preferred embodiment of the AAU  10  has its preferred normal operating range listed based on the pressures of typical aerobic sewage treatment devices employed and sold by the inventors; it is possible that the normal operating pressure condition range could extend to include other pressures than set forth for the preferred embodiment (depending upon the needs of the sewage treatment device  40 ).  
      The preferred embodiment of the AAU  10  employs a dual air switch type of sensor-alarm panel  30 . The alarm elements of this configuration will be activated when the air pressure created by the aerator  20  falls below or rises above the normal operating pressures. The dual air switch type sensor-alarm panel  30  would be activated (based on a low pressure situation), for instance, if the aerator  20  failed to maintain the minimum operating pressure due to some sort of mechanical failure within the aerator  20 , or if there was a break in the air supply line  45  (creating a leak). The alarm would also be activated (based on a high pressure situation) during a high water condition in which the inlet and outlet pipes within the aerobic tank of the sewage treatment device  40  are being blocked by an over fill of water in the tank. This would cause the pressure in the tank to rise significantly above normal operating limits. A high pressure condition could also exist if there were a blockage of the diffuser element within the aerobic tank of the sewage treatment device  40  (i.e. the element for dispersing air into the sewage) or the air supply line  45  leading from the aerator  20  to the sewage treatment device  40 . The alarm condition will remain activated until pressure returns to within the normal operating pressure range. This high pressure detection feature of the sensor-alarm panel  30  could significantly increase the life of the aerator  20 , since the aerator life is shortened when a maintained back pressure is applied to the aerator  20  for a prolonged period of time.  
      In the preferred embodiment, the actual sensing element used to monitor for high and low pressure outside the normal operating condition range is a dual air switch  33 . The dual air pressure switch  33  has two rubberized diaphragms encased into a single housing. The air pressure from the aerator  20  inputs between the two diaphragms. Against the outside of each of the diaphragms are two micro-switches. One micro-switch is arranged in the normally open position, and the other is arranged in the normally closed position. When the air pressure increases to the normal operating range, the normally closed switch is opened so that electrical current will not flow to the alarm circuit. This circuit monitors the low air pressure side of the switch. If the air pressure falls below the normal operating range, the micro-switch will close causing an electrical path back to an alarm circuit. If the air pressure increases to outside the normal operating range, the normally open micro-switch will close providing an electrical path back to the alarm circuit. This circuit monitors the high air pressure side of the switch. While this sort of dual air pressure switch  33  performs the high and low pressure monitoring in the preferred embodiment, obviously other sensor arrangements are possible.  
      For example, a second sensor arrangement could incorporate two separate single air pressure switches, each of which is set to a different pressure setting. One switch would be set to open at a low pressure setting, and the other would be set to close at a high pressure setting. The two switches could then be joined together by means of air tubing and an air tubing tee, which would feed both air switches simultaneously and, in effect, give the same result as the dual air switch  33  explained above. Any sensor arrangement which converts the physical air pressure information into electrical inputs that affect whether or not the sensor-alarm panel  30  circuit activates alarm elements would likewise operate. Persons skilled in the art field will comprehend alternative sensors and sensor arrangements, all of which are included within the scope of this invention.  
      In the preferred embodiment, the audible alarm is buzzer  37  that sounds as a warning, and the visual alarm is a lamp  38  that illuminates to notify the user/owner of a potential problem. Clearly any number of other types of audible and visual devices might serve as alarm/warning/notification elements. The sensor-alarm panel  30  circuit simply activates the alarm elements in the event that non-normal operating conditions are detected, and the alarm elements then warn the user/owner according to their design/function. By way of example, the audible alarm could alternatively be a bell, a horn, a whistle, activation of an electronic speaker device (such that it emits a sound), or an automated telephone call. Examples of alternative visual alarms could include a flashing LCD light, activation of an electronic monitor with a warning message, transmission of an e-mail message, or transmission of a printed warning message to a designated site (akin to telex or facsimile).  
      In the preferred embodiment, the sensor-alarm panel  30  is housed within a separate case, which is typically mounted to the case of the aerator unit  20 . In the preferred embodiment, the sensor-alarm panel  30  housing is rigidly attached to the housing of the aerator  20  via a bracket  39 . And in the preferred embodiment, a single power source operates both the aerator  20  and the sensor-alarm panel  30 . While any electrical power source may operate the AAU  10 , the preferred power source is AC current from a standard electrical socket. Thus, in the preferred embodiment, the power cord  12  for the aerator  20  is also connected to power the sensor-alarm panel  30 . The power cord  12  connects the aerator  20  and the sensor-alarm panel  30  in parallel, to operate both elements of the AAU  10  off the same power source.  
      The preferred embodiment further makes use of an air sensing port in the aerator  20 , which is attached to the sensor-alarm panel  30  via an air pressure sensing line/tube  13 . It is through this connection that the air pressure at the bottom of the aerator  20  (i.e. the pressure in the air output port  14 , which connects via the air supply line  45  to the sewage treatment device  40 ) is monitored by the dual air switch  33  of the sensor-alarm panel  30 . In other words, the air pressure sensing line  13  provides the relevant air pressure to the sensor-alarm panel  30 , in order to determine whether or not the air pressure is within the normal operating range.  
      An optional element available on the preferred embodiment is a switch  35  which allows the Aerator Alarm Unit  10  to be set for up to three different modes. In essence, the different modes are built into the circuitry of the sensor-alarm panel  30  as an electrical switch. The first switch setting places the Aerator Alarm Unit  10  in test mode. Test mode activates the alarm(s), enabling the user to ensure that the alarms are functioning properly. So in test mode, voltage is applied to the alarm elements of the circuit, to ensure that the circuitry and the physical elements of the alarm elements are operating properly. The second switch setting places the Aerator Alarm Unit  10  in run mode. This is the normal operation mode for the AAU  10  (in which it monitors the pressures and activates the alarm if necessary). In essence, this is the static state of the sensor-alarm circuitry, allowing normal operation.  
      The third switch setting places the Aerator Alarm Unit  10  in mute mode. This mode disconnects the audio alarm, so that the AAU  10  runs as normal but will only activate the remaining alarm elements (for example, visual alarm elements). Basically, the portion of the circuit controlling the audible alarm element becomes electrically disconnected, so that it does not actively interact with the remainder of the sensor-alarm panel  30 . In the preferred embodiment, the alarm elements include both an audible alarm and a visual alarm. So for example, in mute mode, the Aerator Alarm Unit  10  would activate only the visual alarm if the sensor elements monitor pressures outside of the normal range. The alarm elements in the preferred embodiment give an audible and/or visible warning, as set out in the NSF/ANSI  40  standard for system failure indications. Of course, additional, optional modes (such as an “off” mode) could also be incorporated into the circuitry of the sensor-alarm panel  30 .  
      Typically, the Aerator Alarm Unit  10  would mount atop the sewage treatment device  40  that it services, so that if the sewage treatment device  40  is buried underground, the AAU  10  would project up above the surface. Alternatively, it could be placed elsewhere at some location above ground (and connected to the sewage treatment device  40  via an air supply line  45 ), while the entire sewage treatment device  40  is buried beneath the surface of the ground. Regardless, the Aerator Alarm Unit  10  must have some access to an open ventilation source, from which the aerator  20  can draw its air supply.  
      By using a sensor-alarm panel  30  that operates by monitoring the aerator  20 , several important goals may be accomplished. First, the sensor-alarm panel  30  will typically be housed in association with the aerator  20  itself, above ground and external to the sewage treatment device  40  aerobic tank. This design allows for effective monitoring of the sewage treatment device&#39;s effectiveness without the need to place the sensor elements within the harsh environment of the sewage treatment device  40  aerobic tank. By removing the sensor elements from the inside of the sewage treatment device  40  aerobic tank and instead placing them outside the tank in conjunction with the aerator  20 , the reliability and lifespan of the sensor elements is increased because there is less chance of environmental erosion effecting the sensor elements and/or damage or deterioration to the wiring between the sensor elements and the alarm.  
      Furthermore, the sensor-alarm panel  30  and aerator  20  of the present invention function in a cooperative/synergistic manner, since this design improves the lifespan of the aerator  20  while also allowing the sensor-alarm panel  30  to directly monitor the performance of the critical aerator  20  element as well as the overall functioning of the sewage treatment device  40 . In other words, this integrated design provides additional monitoring capabilities, which would not be available if the sensor elements were located within the sewage treatment device  40  itself.  
      Placing the sensor elements in conjunction with the aerator  20  (outside of the aerobic tank of the sewage treatment device  40 ) also simplifies periodic maintenance and testing of the alarm elements. Since the alarm elements in the present invention are located above ground, ease-of-access is greatly improved. Finally, it is much easier to retrofit existing sewage treatment devices  40  to add in sensing/alarm capabilities using this unit (rather than using float switch technology or other such means), since the sewage treatment device  40  itself does not have to be opened up and altered internally. Instead, the standard aerator  20  for existing aerobic sewage treatment devices  40  can simply be replaced with an entirely new Aerator Alarm Unit  10 , or a sensor-alarm panel  30  could even be connected to the existing standard aerator  20  in a retrofit. Regardless of retrofit technique, it would be a relatively simple matter to use prepackaged equipment provided by the applicants to improve an existing aerobic sewage treatment device  40  by adding an external monitor and alarm in connection to the aerator  20 .  
      When the Aerator Alarm Unit  10  is installed for use with an aerobic sewage treatment device  40 , the AAU  10  pumps air into the aerobic tank of the sewage treatment device  40  via an air supply line  45 . The air supply line  45  distributes air to whatever mechanism is in place within the aerobic tank of the sewage treatment tank  40 , so that air will be emitted out into the aerobic tank, aerating the sewage. Injecting air into the sewage activates and stimulates the aerobic microorganisms in the sewage, which causes the aerobic microorganisms to multiply and increases the amount of sewage that they digest. This aerobic process eliminates sewage contaminants to a great extent, cleaning the sewage.  
      As the aerator  20  of the AAU  10  operates, the sensor-alarm panel  30  monitors the air pressure in the air supply line  45  between the aerator  20  and the sewage treatment tank  40 . Specifically, in the preferred embodiment the dual air switch  33  monitors the air pressure in the air supply line  45  leading from the aerator air output port  14  to the sewage treatment device  40  via the air pressure sensing line  13 . In normal run mode, the AAU  10  will pump air continuously down into the sewage treatment tank  40 . If the sensor-alarm panel  30  monitors a problem (either high or low pressure outside of the normal operating range), then the alarm elements will be activated to notify the owner/user of a potential problem so that they can check the situation and call for repair service if necessary.  
      In the preferred embodiment, both an audible alarm and a visible alarm would be activated in normal run mode. In mute mode, however, only the visible alarm would be activated. In this manner, the AAU  10  keeps the aerobic sewage treatment device  40  operating effectively (by ensuring that it has the appropriate amount of air necessary for aerobic sewage treatment) and improves the operable lifespan of the aerator  20  (by allowing quick maintenance to keep the proper conditions for durable aerator  20  operation). In the preferred embodiment, the user/owner may also test the alarm elements (to ensure that they are still functioning properly and will be able to effectively notify/warn the user/owner of a potential problem) using the test mode feature of the AAU  10 . Another option would be to configure the sensor-alarm panel  30  so that different alarms would be activated to notify the user/owner of high and low pressure conditions.  
      In the preferred embodiment, the aerator  20  and the sensor-alarm panel  30  operate independently, so that the aerator  20  will continue to pump air to the sewage treatment device  40  regardless of whether or not the sensor alarm panel  30  has monitored conditions outside of the normal operating range. This ensures that the sewage treatment device  40  has aeration for as long as possible (since aeration is key to effective sewage treatment), even at the risk of damaging the aerator  20 . An alternative embodiment, would connect the aerator  20  to the sensor alarm panel  30  in conjunction with a kill switch, such that the aerator  20  would be deactivated if the alarm had run for more than a pre-set amount of time without being manually deactivated. This alternative configuration would protect the aerator  20  from being damaged, but it would have the drawback of leaving the sewage treatment device  40  more unreliable and dependent upon quick human maintenance (especially since the alarm may sound under conditions that do not signal potential damage to the aerator  20 , i.e. low pressure conditions).  
      Additional alternatives would include a battery backup power supply for the AAU  10 , which would run the device in the event that the primary power source ceased functioning (so that, for example, if electrical power goes down, the sewage treatment device  40  would continue to operate effectively for a period of time), and/or a sensor-alarm panel  30  which further includes an alarm activation routine in case of power loss (notifying the user/owner that the sewage treatment device is no longer being aerated). Obviously other optional features, such as automatic notification to a service representative via a connected phone line, could also be included.  
      The precise rate of air flow and air pressure which the aerator  20  should produce will depend upon the size and type of aerobic sewage treatment device  40  at issue. A person of ordinary skill in the art field will readily understand and be able to adapt the AAU  10  to provide the particular needs of a specific aerobic sewage treatment device  40 . Considerations which could affect the flow rate of the aerator include the size and depth of the aerobic sewage treatment device, and the size of the discharge holes in the diffuser or air droptubes. And clearly, the aerator would need to provide sufficient air flow to effectively aerate the sewage in the aerobic tank of the sewage treatment device. In the preferred embodiment, the aerator  20  is designed so that under normal operating conditions it would provide the necessary flow of air to an aerobic sewage treatment device  40  as set forth by NSF/ANSI  40  standard for aerobic treatment units.  
      The specific embodiments and uses set forth herein are merely illustrative examples of the preferred embodiment of the AAU  10  invention and are not intended to limit the present invention in any way. A person skilled in the field will understand and appreciate additional embodiments and uses, as well as equivalents, which are also included within the scope of the present invention. Furthermore, any patents listed herein by way of example are specifically incorporated by reference. The scope of the invention is more fully defined in the following claims, and the only limits to the scope of the invention are those set forth explicitly in the claims below.