Patent Publication Number: US-10316504-B2

Title: Vacuum sewage system with monitoring system and method of use

Description:
The present invention relates generally to sewage systems which utilize differential pressures to produce sewage transport through the system and, in particular, to such a sewage system having a monitoring system for determining the conditions prevailing at various locations in the system. The present invention also relates to methods for using such a system. 
     SUMMARY OF THE INVENTION 
     In one embodiment of the present invention, a vacuum sewage system includes a collection station, a vacuum pump located at the collection station, a sewage pump located at the collection station, a collection tank located at the collection station, a control system located at the collection station, a valve pit, a first conduit extending from the collection station to the valve pit, a second conduit extending from the valve pit and terminating in a closed end, a valve located in the valve pit for selectively permitting sewage and waste water to flow from the valve pit toward the collection station upon activation of the valve, an electric air admission controller for selectively opening and closing the valve, a first sensor associated with the electric air admission controller and a second sensor located adjacent the closed end of the second conduit. 
     In one embodiment, the electric air admission controller is replaced by a solenoid 
     In another embodiment, the control system includes a programmable controller. The control system may also include means for communicating with the first and second sensors. The means for communicating with the first and second sensors can include wireless communication means. 
     In another embodiment of the present invention, the first conduit has a section with a repeating series of risers, low points and down slopes. The down slopes may be inclined at an angle of 0.1% relative to a horizontal plane. 
     In one embodiment of the present invention, a method of operating a vacuum sewage system includes the steps of utilizing a sensor to detect system vacuum level at a location in the system, comparing the detected system vacuum level to a previously specified system vacuum level, detecting the operating time of a sewage pump and comparing the detected operating time of the sewage pump with a previously specified operating time range. If the detected system vacuum level is at or below the previously specified system vacuum level and the detected operating time of the sewage pump is within the previously specified operating time range, a valve is selectively opened and closed in a previously specified timing cycle so as to admit air into the sewage system. The method of this embodiment further includes the steps of detecting the vacuum level at a sewage collection station and comparing the detected vacuum level at the sewage collection station with a first previously specified collection station vacuum level. If the detected vacuum level at the sewage collection station is below the first previously specified collection station vacuum level, a first vacuum pump is operated while continuing to detect the vacuum level at the sewage collection station and comparing the detected vacuum level at the sewage collection station to a second previously specified collection station vacuum level. If the detected vacuum level at the sewage collection station is below the second previously specified collection station vacuum level during operation of the first vacuum pump, a second vacuum pump is operated. The valve is selectively opened and closed so as to admit air into the sewage system in the previously specified timing cycle until the detected system vacuum level reaches or exceeds the previously specified system vacuum level. 
     In one embodiment, the previously specified system vacuum level is approximately 12 inches of mercury. 
     In another embodiment, the previously specified sewage pump operating time range is less than approximately 3.5 minutes. 
     In another embodiment, the first previously specified collection station vacuum level is approximately 16 inches of mercury. The second previously specified collection station vacuum level may be approximately 15 inches of mercury in some embodiments. 
     In another embodiment of the invention, the previously specified timing cycle for the valve is 20 seconds open and 10 minutes closed. 
     In one embodiment, the system vacuum level is detected at the end of a conduit. 
     In another embodiment, an electric air admission controller is used to operate the valve. Alternatively, a solenoid may be used to operate the valve. 
     In one embodiment of the present invention, a method of operating a vacuum sewage system includes the steps of determining an anticipated peak operating time of the sewage system, specifying a purge start time prior to the anticipated peak operating time, at the specified purge start time, selectively opening and closing a valve in the sewage system in a previously specified timing cycle so as to admit air into the sewage system, detecting the vacuum level at a sewage collection station and comparing the detected vacuum level at the sewage collection station with a first previously specified collection station vacuum level. If the detected vacuum level at the sewage collection station is below the first previously specified collection station vacuum level, a first vacuum pump is operated while continuing to detect the vacuum level at the sewage collection station and comparing the detected vacuum level at the sewage collection station to a second previously specified collection station vacuum level. If the detected vacuum level at the sewage collection station is below the second previously specified collection station vacuum level during operation of the first vacuum pump, a second vacuum pump is operated. The valve is selectively opened and closed for a previously specified time period so as to admit air into the sewage system in the previously specified timing cycle. 
     In one embodiment of the invention, the first previously specified collection station vacuum level is approximately 16 inches of mercury. In another embodiment of the invention, the second previously specified collection station vacuum level is approximately 15 inches of mercury. 
     In one embodiment, the previously specified timing cycle for the valve is 20 seconds open and 10 minutes closed. In another embodiment, an electric air admission controller is used to operate the valve. In one embodiment, a solenoid is used to operate the valve. 
     In one embodiment of the invention, the previously specified time period is approximately 30 minutes. 
     In one embodiment of the present invention, a method of operating a vacuum sewage system includes the steps of specifying a sewage pump cavitation point, utilizing a sensor to detect system vacuum level at a location in the system, comparing the detected system vacuum level to a previously specified system vacuum level, detecting the operating time of a sewage pump and comparing the detected operating time of the sewage pump with a previously specified operating time. If the detected system vacuum level is below the previously specified system vacuum level and the detected operating time of the sewage pump is longer than the previously specified operating time, a first vacuum pump is operated while monitoring the vacuum level at a sewage collection station The monitored vacuum level at the sewage collection station is compared with a first previously specified collection station vacuum level, the operation of the sewage pump is monitored and the first vacuum pump is continued in operation until either the monitored vacuum level at the sewage collection station reaches or exceeds the first previously specified collection station vacuum level or until the sewage pump reaches a point just below its cavitation point, whichever occurs first. The method further includes the steps of continuing to monitor the operating time of the sewage pump during operation of the first vacuum pump and comparing the operating time of the sewage pump to a previously specified operating time range. When the monitored operating time of the sewage pump is within the previously specified operating time range, the method includes performing the following additional steps: selectively opening and closing a valve in the sewage system in a previously specified timing cycle so as to admit air into the sewage system, detecting the vacuum level at the sewage collection station, comparing the detected vacuum level at the sewage collection station with a second previously specified collection station vacuum level, if the detected vacuum level at the sewage collection station is below the second previously specified collection station vacuum level, operating the first vacuum pump, continuing to detect the vacuum level at the sewage collection station during operation of the first vacuum pump and comparing the detected vacuum level at the sewage collection station to a third previously specified collection station vacuum level, if the detected vacuum level at the sewage collection station is below the third previously specified collection station vacuum level during operation of the first vacuum pump, operating the second vacuum pump and continuing to selectively open and close the valve so as to admit air into the sewage system until the detected system vacuum level reaches or exceeds the previously specified system vacuum level. 
     In one embodiment of the invention, the previously specified system vacuum level is approximately 12 inches of mercury. 
     In another embodiment of the invention, the previously specified sewage pump operating time is approximately 4.5 minutes. In one embodiment, the previously specified sewage pump operating time range is less than approximately 3.5 minutes. 
     In another embodiment of the invention, the first previously specified collection station vacuum level is approximately 22 inches of mercury. In another embodiment, the second previously specified collection station vacuum level is approximately 16 inches of mercury. In one embodiment, the third previously specified collection station vacuum level is approximately 15 inches of mercury. 
     In another embodiment of the invention, the previously specified timing cycle for the valve is 20 seconds open and 10 minutes closed. 
     In one embodiment, the system vacuum level is detected at the end of a conduit. 
     In another embodiment, an electric air admission controller is used to operate the valve. In one embodiment, a solenoid is used to operate the valve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a vacuum sewage system according to one embodiment of the present invention. 
         FIG. 2  is a detail view of the areas indicated in  FIG. 1  by reference “ FIG. 2 .” 
         FIG. 3  is a partial sectional view of a valve pit and electric air admission controller that are components of the system of  FIG. 1 . 
         FIG. 4  is an elevational view of a collection station that is a component of the system of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION 
       FIGS. 1 and 2  illustrate a vacuum sewage system  10  according to one embodiment of the present invention. System  10  generally includes a series of conduits  20 , holding tanks  30 , valve pits  40 , electric air admission controllers (“EAAC”)  50 , check valves  60 , sensors  70  and a collection station  80 . 
     Conduits  20  are typically laid out in a saw-toothed pattern with a repeating series of risers  21 , low points  22 , and downslopes  23  (each series collectively called a “lift”). In certain prior art devices, the downslopes are inclined at an angle of 0.2%. In one embodiment of the present invention, downslopes  23  are inclined in the direction of arrow “A” at an angle of 0.1%. Laser leveling and surveying technology may be used to accurately position downslopes  23 . Reducing the angle of incline of downslopes  23  can reduce the number of lifts required in system  10  (in some applications reducing the number of lifts by 50%) which permits larger networks of conduit  20 . The 0.1% downslope angle also reduces vacuum loss throughout system  10 . 
     Referring to  FIGS. 2 and 3 , conduits  31  transport sewage to holding tank  30 , which is maintained at atmospheric pressure. A sensor pipe  32  and a discharge conduit  33  extend into tank  30 . A first end  32 A of pipe  32  extends downwardly into tank  30  to a point spaced above the inlet opening  33 A of a discharge conduit  33 . The second end  32 B of pipe  32  extends into a valve pit  40 . Discharge conduit  33  extends into the valve pit  40  to a valve  41 . Numerous types of valves  41  are known in the industry. One example of a valve  41  that can be used with system  10  is disclosed in U.S. Pat. No. 4,171,853. Valve  41  is operated by a controller  42 . The section of discharge conduit  33  downstream from valve  41  is maintained at vacuum or low pressure by vacuum pumps (described below). Discharge conduit  33  ultimately discharges into collection station  80 , which is also maintained at vacuum or low pressure. 
     In use, sewage is discharged through conduit  31  into tank  30 . Under preselected pressure conditions in tank  30  (i.e. when the sewage content of tank  30  is such that a discharge cycle is warranted) valve  41  is opened by controller  42 . Opening valve  41  creates a differential pressure between the relatively low pressure or vacuum portion of discharge conduit  33  downstream from valve  41  and the relatively higher or atmospheric pressure portion of discharge conduit  33  upstream from valve  41 . This pressure differential causes discharge of the sewage in tank  30  through inlet opening  33 A of discharge conduit  33 , past valve  41 , through the portion of discharge conduit  33  downstream from valve  41  and ultimately to collection station  80 . 
     Collection station  80  generally includes a shed or other enclosure  81 , a collection tank  82 , one or more vacuum pumps  83 , sewage pumps  84 , sewage discharge conduit  85  and a control system  86  which, in the embodiment shown, includes a programmable controller including wireless communication means, and a wireless communication antenna  87 . Conduits  20  discharge into collection tank  82 . Vacuum pump  83  is associated piping  83 A and draws a vacuum on collection tank  82  and through conduits  20  of system  10 . Sewage pumps  84  discharge sewage from collection tank  82  through discharge pipe  85  to a sewage treatment facility (not shown.) Control system  86  and antenna  87  communicate with sensors  70  as described below. 
     Upon completion of a transport cycle, valve  41  is automatically closed and the vacuum sewage transport system of the invention is restored to the stand-by condition. With the saw-toothed arrangement of conduits  20  discussed above, sewage that was not transported to collection station  80  will generally come to rest in the low points  22  and will not seal the conduit  20  when the transport cycle ends. This permits the same vacuum pressure to be distributed throughout the conduits  20 , including that portion of the conduit above the material in the low portion  22  of the conduit. However, vacuum sewage systems can sometimes experience a condition known as “waterlogging.” Waterlogging occurs when residual waste matter in conduit  20  accumulates to the point that fills all or a significant portion of the conduit cross section (such as two-thirds or more) as shown in  FIG. 2 . This prevents the vacuum pressure produced by vacuum pump  83  from being communicated through the entire network of conduits  20 . 
     EAAC&#39;s  50  may be used to monitor the vacuum level at the location of the EAAC. One suitable EAAC is described in U.S. Pat. No. 5,044,836. If the localized vacuum level drops, due to factors such as waterlogging, the EAAC can activate a valve  41  and admit additional air into system  10 , thereby clearing the waterlogged condition. With the present invention, sensors  70  located at the ends of conduits  20  and elsewhere in system  10  can be used to monitor vacuum levels throughout the system, not just at EAAC&#39;s  50 . In one embodiment of the invention, sensors  70  are pressure transducers that measure the vacuum level and convert it to a voltage scaled to the vacuum level. Other types of sensors may be used in addition to or instead of pressure transducers. Sensors  70  include wireless communication technology for transmitting vacuum-level readings to control system  86 . In this manner, collection station  80  can monitor the conditions in system  10  and clear residual sewage and maintain vacuum pressure. For example, when an insufficient vacuum is detected at one or more of sensors  70 , control system  86  can activate vacuum pump  83  to increase vacuum in the system and clear residual sewage. In addition, or alternatively, control system  86  can send a signal to one or more of EAAC&#39;s  50  to activate its associated valve  41  to introduce additional air into the system, thereby clearing residual sewage. Use of sensors  70  and EAAC&#39;s  50  in this manner is particularly useful in clearing residual waste matter that may be more likely to accumulate in systems  20  that utilize downslopes  23  angled at 0.1% as discussed above. Locating check valves  60  behind the various lifts in conduits  20  prevents backflow through system  10 . The use of check valves  60  positioned in this manner may be particularly beneficial when used in connection with the 0.1% angle downslopes  23  of conduits  20 . 
     The system of the present invention may be programmed to detect certain parameters which indicate a potential waterlogging situation. For example, if the vacuum detected by a sensor  70  at the end of a conduit  20  is less than 12 inches of mercury but the operating time of sewage pump  84  is normal, for example, less than three and one-half minutes, the system  10  may be experiencing a waterlogged condition. In one method of eliminating a waterlogged condition according to an embodiment of the present invention, one or more EAAC&#39;s  50  are cycled on and off to admit air into system  10 . For example, EAAC&#39;s  50  may be utilized to open valves  41  for 20 seconds followed by a 10 minute closed period. In conjunction with operating EAAC&#39;s  50 , one of the vacuum pumps  83  is activated when the vacuum at station  80  drops below a pre-set level. For example, normal vacuum at station  83  may be between 16 inches of mercury and 20 inches of mercury and a vacuum pump  83  may be operated when that pressure drops to 16 inches of mercury or below. Additional vacuum pumps  83  may be activated in a timed sequence subsequent to activation of the first vacuum pump  83  if the vacuum level at station  80  drops below 15 inches of mercury. The activation cycle of EAAC&#39;s  50  and vacuum pumps  83  may be continued until the vacuum at the end of conduit  20  rises above 12 inches of mercury. 
     System  10  of the present invention may also be utilized to run a purge cycle to clear system  10  prior to anticipated peak operating times. A purge start time can be selected such as, for example, two hours before an anticipated peak operating time. These anticipated peak operating times may, for example, be a time when it is anticipated users will be waking in the morning to prepare for school, work or other activities or returning home for the day. To purge system  10 , one or more EAAC&#39;s  50  may be cycled on and off. For example, EAAC&#39;s  50  may be utilized to open valves  41  for 20 seconds followed by a 10 minute closed period. In conjunction with operating EAAC&#39;s  50 , one of the vacuum pumps  83  is activated when the vacuum at station  80  drops below a pre-set level. For example, a vacuum pump  83  may be operated when the pressure at station  80  drops to 16 inches of mercury or below. Additional vacuum pumps  83  may be activated in a timed sequence subsequent to activation of the first vacuum pump  83  if the vacuum level at station  80  drops below 15 inches of mercury. The activation cycle of EAAC&#39;s  50  and vacuum pumps  83  may be continued for a pre-set time period, for example, for 30 minutes. 
     System  10  of the present invention can also be used to reduce or eliminate the effects of friction losses associated with heavy usage. Under heavy use situations, sewage pump  84  may operate for longer than desired time intervals as a result of the increased work required to move large amounts of sewage through conduits  20 . This increased work is attributable at least in part to increased friction between the large amounts of sewage moving through the system and the interior surfaces of conduits  20 . For example, the system  10  may be programmed to remediate a friction loss situation when the vacuum detected at the end of a conduit  20  drops below 12 inches of mercury and the operation time of sewage pump  84  is greater than four and one-half minutes. This situation may be addressed by a two stage process. In the first stage, one or more of the vacuum pumps  83  are operated until the vacuum level at the station increases to 22 inches of mercury or until a point just below the cavitation point of sewage pump  84 , whichever occurs first. When the operating time of sewage pump  84  drops back to its normal range such as, for example, less than three and one-half minutes, a second remediation stage is begun in which the purge cycle described above is carried out until the vacuum at the end of conduit  20  rises above 14 inches of mercury. 
     Although the present invention has been shown and described in detail the same is to be taken by way of example only and not by way of limitation. Numerous changes can be made to the embodiments described without departing from the scope of the invention. For example, EAAC&#39;s  50  could be replaced with solenoids that activate valves  41 . Furthermore, the methods described above for addressing a waterlogged condition, purging the system and/or reducing friction loss in high flow situations may be performed using different pressure and timing parameters than those specifically described above.