Patent Publication Number: US-9409190-B2

Title: Pressure washing system for wet wells

Description:
FIELD OF THE INVENTION 
     The invention relates generally to in-situ systems for washing wet wells. 
     BACKGROUND OF THE INVENTION 
     Sewage treatment systems use a number of waste water holding facilities generally referred to as wet wells. Wet wells generally consist of a large tank having concrete walls. These tanks are periodically filled, or partially filled with sewage which has a tendency to deposit debris and organic matter on the walls of the wet well. Over a period of several hours, the debris and organic matter deposited on the walls of the wet well can lead to foul smells emanating from the wet well. In order to prevent the foul odors and built up crusting on the walls of the wet wells, they can be washed periodically to remove the debris and organic matter from the walls. In-situ systems for washing wet wells have usually involved the use of low pressure water sprayed to the walls in order to dislodge the debris clinging to the walls. Some systems have even employed the use of the sewage water itself to wash the walls. 
     While washing the walls of wet wells with municipal water (or even sewage) can be effective, the volume of water required is generally quite high. These systems require large amounts of water, large pumps, large fittings and tubing and increased installation and maintenance costs. A more efficient system which uses less water and which is less expensive to install and maintain would be beneficial. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the present invention, there is provided a system for automatically washing down a plurality of walls of a wet well. The system includes a high pressure water pump for creating a flow of high pressure water. An elongated header is mounted adjacent each wall of the wet well. Each elongated header is dimensioned to extend along a length of the entire wall to which it is mounted such that the elongated header spans the entire wall. The system further includes a plurality of high pressure water nozzles formed on each of the elongated headers. The high pressure water nozzles are positioned on each elongated header to wash a portion of the wall to which the elongated header is mounted adjacent to with high pressure water. Each elongated header is coupled to the high pressure water pump via a solenoid valve, with each solenoid valve being coupled to a control unit. The control unit is configured to open and close the solenoid valves such that the flow of high pressure water is directed to one elongated header at a time. 
     With the foregoing in view, and other advantages as will become apparent to those skilled in the art to which this invention relates as this specification proceeds, the invention is herein described by reference to the accompanying drawings forming a part hereof, which includes a description of the preferred typical embodiment of the principles of the present invention. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of the system for washing a wet well made in accordance with the present invention. 
         FIG. 2  is a side view of a portion of the system shown in  FIG. 1  showing the pivoting system for pivoting the header portion of the invention. 
         FIG. 3  is a top schematic view of the header portion of a system for washing a wet well shown in  FIG. 1 . 
         FIG. 4  is a side view of the high pressure pump portion and control unit portions of the system shown in  FIG. 3 . 
         FIG. 5  is a top schematic view of the header portion of a system for washing a wet well made in accordance with another aspect of the present invention. 
         FIG. 6  is a front view taken along perspective A of the system for washing a wet well shown in  FIG. 5  showing details of the elevator system portion of the invention. 
         FIG. 7  is a side view of a portion of the system for washing a wet well shown in  FIG. 5  showing details of the elevator system portion of the invention. 
     
    
    
     In the drawings like characters of reference indicate corresponding parts in the different figures. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring firstly to  FIG. 1 , a system for washing the walls of a wet well made in accordance with the present invention is shown generally as item  10  and consists of a high pressure water pump  16  capable of generating a flow of high pressure water, preferably from a municipal water source  9 . High pressure water pump  16  is coupled to an elongated header  18  which is mounted to wall  12  of the wet well. A plurality of nozzles  20  are formed on header  18  and are positioned on the header such that the nozzles are oriented toward surface  14  of wall  12 . The number, style and orientation of nozzles  20  is selected such that the high pressure streams  34  emanating from the nozzles when pump  16  is activated overlap sufficiently to clean an elongated continuous portion of surface  14  immediately adjacent header  18 . Elongated header  18  is coupled to high pressure pump  16  via high pressure water lines  32  and  24  with solenoid valve assembly  21  interposed between water lines  32  and  24 . Solenoid valve assembly  21  includes a plurality of solenoid valves  22 ,  22   a ,  22   b  and  22   c . Each of the solenoid valves is identical and is electrically coupled to control panel  30  which controls the operation of each of the solenoid valves. Each solenoid valve operates in either a closed or open state. As in all valves, when solenoid valve  22  is in its open state, water flows through the valve and high pressure water from pump  16  can flow to header  18 . When solenoid valve  22  is in its closed state, the flow of high pressure water is shut off. 
     Pump  16  preferably consists of an electric motor  26  coupled to a high pressure pump  28 . Electric motor  26  is preferably a 10 hp motor, however any suitable electric motor and pump combination capable of delivering a flow of water at a pressure of 1000 psi and a flow rate of greater than about 10 gallons per minute will be sufficient. Such motor and pump combinations are readily available on the market from a variety of different vendors. Pump  28  is supplied by municipal water via a standard ¾ inch water line  9 . A backflow preventer  36  and an inline filter  38  are preferably coupled to pump  28  between the pump and water line  9 . 
     Solenoid valve assembly  21  consists of a plurality of solenoid valves mounted on a rack or rail. One end of each solenoid valve is preferably coupled to a high pressure header  40  which is in turn coupled to high pressure water line  24  from pump  28 . The other end of each solenoid valve is coupled to an elongated header via another high pressure water line. In the example shown, solenoid valve  22  is coupled to elongated header  18  via high pressure line  32 . As shown in  FIG. 3 , a wet well may consist of a rectangular structure having four walls  12 ,  12   a ,  12   b  and  12   c , with a separate header  18 ,  18   a ,  18   b  and  18   c  mounted to each wall, respectively. Each separate header would be coupled to the high pressure water source by a separate solenoid valve. Hence, headers  18 ,  18   a ,  18   b  and  18   c  in  FIG. 3  would be coupled to solenoid valves  22 ,  22   a ,  22   b  and  22   c  in  FIG. 1 , respectively. In this way the flow of high pressure water to each separate header would be controlled by a separate solenoid valve. Control panel  30 , as shown in  FIG. 1 , is coupled to each solenoid valve and controls the opening and closing of each valve. Control panel  30  is provided with a logic controller or control circuit of some kind which alternates the opening and closing of solenoid valves  22 ,  22   a ,  22   b  and  22   c  sequentially so that only one solenoid valve is opened at a time. This ensures that all of the high pressure water generated at pump  28  is directed to only one elongated header at a time. As a result, the wet well is washed one wall at a time. By allowing one wall to be washed at a time, the size of the high pressure pump  28  and motor  26  can be minimized and the capacity of the water source  9  can be more modest. Therefore, a standard ¾ inch water line is usually all that is required to operate the wet well washing system made in accordance with this invention. 
     Referring now to  FIGS. 2 and 3 , each wall in wet well  7  has at least one header mounted thereto. If the wall of the wet well is very long, then it is possible to mount two headers together in coaxial alignment in order to span the wall. Hence, wall  12  may be spanned by two elongated headers, namely headers  18  and  18   d . Headers  18  and  18   d  are identical, and each is supported by a pair of brackets mounted to wall  12 , namely brackets  44  and  46  and brackets  48  and  50 , respectively. Each header is mounted to its pair of brackets such that the header can pivot along its longitudinal axis. Each header is also coupled to a pivoting mechanism as shown in  FIG. 2 . Pivot mechanism  42  is mounted to the wall of the wet well a few feet above the elongated header. Pivot mechanism  42  includes a pivot arm  52  which can be moved up or down (shown with dotted lines). Pivot arm  52  is coupled to lever arm  56  mounted to the elongated header by cable  54 . Pivot arm  52  is pivoted up and down by an electric motor (not shown) contained within pivot mechanism  42 . As pivot arm  52  raises and lowers, the header is likewise pivoted about its long axis. As the header  18  is pivoted, nozzles  20  are pivoted between two angular positions relative to the wall (i.e. pivoted up and down) and high pressure water streams  34  are directed up and down in a sweeping fashion. This up and down sweeping movement of the high pressure water sprays emanating from nozzles  20  aids in washing debris off the wall of the wet well, thereby increasing the efficiency of the wash system. 
     The operation of the system shall now be discussed with reference to  FIG. 1  with additional features of the invention being discussed. After installation, water line  9  is opened to supply pump  28  with a source of clean municipal water at normal municipal water pressure. Control panel  30  includes a control circuit which is configured to operate the system once every few hours each day in order to wash the walls of the wet wells. For example, the control panel could be configured with a program cycle of once every four hours, meaning that the wash system is activated once every four hours or about 6 times per day. When the control panel activates the wash system, the control panel starts water pump  16  and opens one of the solenoid valves (say solenoid valve  22 ) while leaving all of the remaining solenoid valves closed. When solenoid valve  22  is opened, a flow of high pressure water is delivered to header  18  which causes nozzles  22  to spray high pressure water streams  34  towards surface  14  of wall  12 . Preferably, nozzles  22  are each configured to deliver a flat jet of high pressure water to wall  14  which has sufficient force to physically dislodge any debris clinging to surface  14 . After a time interval of two to three minutes, control panel  30  closes solenoid valve  22  and opens another solenoid valve, say solenoid valve  22   a . After 2 to 3 minutes, control panel  30  then closes solenoid valve  22   a  and opens solenoid valve  22   b . Solenoid valve  22   b  remains open for two to three minutes before control panel  30  closes valve  22   b  and opens solenoid valve  22   c , and so forth. The solenoid valves are opened then closed in succession, so that only one elongated header is supplied with high pressure water at a time and only one wall, or section of a wall, is washed at a time. Each solenoid valve is opened for only an interval of time (usually only a few minutes), the duration of which is selected to ensure that the section of wall being washed at that time is cleaned adequately. After a total time period of between about 8 minutes to 30 minutes, the control panel closes the last solenoid valve and then shuts down motor  26 . Control panel  30  may be further configured to activate the pivot motor associated with the header to which the solenoid valve is coupled to so that when a particular solenoid valve is activated, the header to which that valve is coupled is pivoted up and down. This maximizes the efficient and complete washing of the portion of the wall adjacent the header. 
     The control circuit contained in control panel  30  may consist of a standard commercially available programmable logic controller board having an onboard timer and sufficient outputs to handle all of the solenoid valves and pivot motors in addition to the pump motor. The solenoid valves may consist of standard 120 v solenoid valves which are commercially available from a number of different vendors. The number of solenoid valves will vary depending on the number of headers used, which in turn is a function of the size of the wet well being washed. For the example shown in  FIG. 3 , it is expected that six separate headers would be used, one header each for walls  12   a  and  12   c , and two coaxially aligned headers for walls  12  and  12   b . The system would therefore require six solenoid valves to ensure that only one header would be operated at a time. 
     Referring now to  FIG. 5 , an alternate embodiment of the present invention shall now be discussed. The alternate embodiment deals with an alternate means for sweeping the inside surface of the wet well by raising and lowering the headers rather than by oscillating the nozzles. System  100  consists of a plurality of headers  102 ,  104 ,  106  and  108  movably mounted to wet well walls  110 ,  112 ,  114  and  116 , respectively. As in the previous embodiment, headers  102 ,  104 ,  106  and  108  consist of elongated pipes having spray nozzles  118  spaced along the headers and directed towards the walls so as to spray the walls with a blast of wash water. Elevator actuators  120 ,  122 ,  124  and  126  are coupled to headers  102 ,  104 ,  106  and  108 , respectively and are configured to raise and lower the headers as required to wash a section of the walls. Referring now to  FIGS. 6 and 7 , each elevator actuator consists of an electric motor configured to turn a pulley coupled to its respective header so as to lift and lower the header a predetermined distance. The elevator actuators shall now be described with reference to actuator  120 ; however, it will be appreciated that each of the actuators are identical in structure. 
     Actuator  120  consists of an electric motor  128  coupled to a chain  130  via sprocket  141 , which is in turn coupled to a sprocket  132  on a rotatable shaft  134  mounted to brackets  142 . Pulleys  136  are fixed along shaft  134  and rotate along with the shaft. Cables  138  couple header  102  to pulleys  136  and permit the header to be raised or lowered as pulleys  136  rotate. Support brackets  140  each have elongated slot  146  to ensure that header  102  moves up and down steadily without knocking against the wall. Each electric motor  128  is coupled to a control unit (not shown) virtually identical to the control panel described with reference to the previous embodiment. When activated, all of the electric motors operate to either raise or lower the headers simultaneously. As in the previous embodiment, each header is coupled to a solenoid valve (not shown) which is in turn coupled to the control panel and to a high pressure water pump. When activated, the control panel operates the actuators to slowly raise and lower the headers while the high pressure water pump is operating so as to sweep a section of the walls of the wet well clean with the high pressure water emanating from nozzles  118 . The nozzles themselves are fixed in position on the header, so instead of washing a section of the wall by oscillating, the header raises and lowers a predetermined distance such that the nozzles sweep a section of the walls. As in the previous embodiment, the solenoids (not shown) are operated so that only one section of header is fed with high pressure water at a time. While system  100  is shown in a rectangular wet well, it will be appreciated that this system of sweeping a section of wet well wall is particularly well suited with a circular wet well. Raising and lowering the headers is particularly effective where the walls of the wet well are curved, such as a circular wet well. 
     The present invention has several advantages over the prior art. In particular, the system uses a relatively small, inexpensive and easily serviced or replaced electric motor to drive the pump since the system only needs to wash a portion of the wet well at any time. A standard 10 hp electric motor is sufficient to operate the system at a pressure of about 1000 psi and a volume flow rate of 10 gallons per minute. The system can be scaled up to nearly any size wet well without having to use a larger water pump or motor simply by adding additional headers and solenoid valves. Furthermore, since the system uses a smaller water pump and motor, the system can utilize standard ¾ inch water lines and fittings. The system is also quicker and uses much less water. Since the pump operates for only 2 to 3 minutes per header, only about 10 minutes is required to fully wash all of the walls of the wet well. Operating the system for 10 minutes consumes only about 100 gallons of water. This makes the system economical to run. The net result is a system which is less expensive and easier to install, less expensive to operate and less expensive to maintain. 
     A specific embodiment of the present invention has been disclosed; however, several variations of the disclosed embodiment could be envisioned as within the scope of this invention. It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims