Patent Abstract:
A filter system includes a set of modules, each module including screen assemblies and filter media sandwiched between the screen assemblies. A plurality of control assemblies are associated with each of the modules. Each of the control assemblies is in fluid communication with a corresponding module to control flow through the corresponding module. The control assemblies selectively control fluid in each of the modules between at least one of a forward flow through the screen assemblies to treat an influent flow, a bypass flow to bypass at least one of the modules, and a reverse flow to backwash a given filter media. A method of filtering influent includes providing an influent flow to a set of modules, each module including screen assemblies and filter media sandwiched between the screen assemblies. The influent is filtered by directing the influent through the set of modules. A given module is bypassed when the given module becomes occluded. The occluded module is backwashed by providing a reverse flow through the screen assemblies and the filter media.

Full Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to filtration equipment, and more particularly, to a modular filtration system. 
     2. Discussion of the Related Art 
     Various filtration systems have been developed for water purification, waste reclamation, fruit drink preparation or other solid/liquid separation. The filtration systems have included different sizes of filtration media that vary with the nature and size of the solids to be removed from the liquid phase. In these filtration systems, however, the flow path typically becomes occluded as the solids accumulate on the filter media. When the filtration system has become occluded, the filters must either be backwashed or removed from service in order to remove the accumulated solids. 
     One problem in filter systems is that the process must be interrupted to backwash the system. When backwashing or removing the system from service, the process is interrupted or shut-down to remove the accumulated solids from the filter media. The flow is diverted to a holding state or a recycle flow during the solids removal creating a backlog in the process. Additionally, once restarted, the flow must be tested to determine that the particles in the effluent are within the desired limits. 
     Another problem that exists in filtration systems is that the media becomes mixed during the backwashing or solids removal. Typically, the filter system includes a chamber having media that is varied from coarse to fine material. The flow starts with a coarse media to remove the larger solids, then trickles down to the finer media to remove the smaller particles. After the system has been backwashed, however, the media is mixed when the backwash flow pushes the finer media up through the coarse media. The backwash flow can also push the filter media to the edges of the chamber creating a short circuit through the media. Thus, after each backwashing, the filtration system can be rendered less effective. 
     SUMMARY OF THE INVENTION 
     A filter system includes a set of modules, each module including screen assemblies and filter media sandwiched between the screen assemblies. A plurality of control assemblies are associated with each of the modules. Each of the control assemblies is in fluid communication with a corresponding module to control flow through the corresponding module. The control assemblies selectively control fluid in each of the modules between at least one of a forward flow through the screen assemblies to treat an influent flow, a bypass flow to bypass at least one of the modules, and a reverse flow to backwash a given filter media. 
     In another aspect of the invention, a method of filtering influent can be provided. The method includes a step of providing an influent flow to a set of modules, each module including screen assemblies and filter media sandwiched between the screen assemblies. The influent is filtered by directing the influent through the set of modules. When a given module becomes occluded, it is bypassed. The occluded module is backwashed by providing a reverse flow through the screen assemblies and filter media. 
     These and other features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       To further clarify the above and other advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments of the invention, which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
         FIG. 1  is a front view illustrating the filter system in accordance with an embodiment of the present invention; 
         FIG. 2  is a first side view of the filter system illustrated in  FIG. 1 ; 
         FIG. 3  is a second side view of the filter system illustrated in  FIG. 1 ; 
         FIG. 4  is a back view of the filter system illustrated in  FIG. 1 ; 
         FIG. 5  is a cross sectional front view of the filter system illustrated in  FIG. 1 ; 
         FIG. 6  is a top view of a screen assembly in accordance with an embodiment of the present invention; 
         FIG. 7  is a first side view of the screen assembly of  FIG. 6 ; 
         FIG. 8  is a second side view of the screen assembly of  FIG. 6 ; 
         FIG. 9  is a detailed side view of the screen assembly of  FIG. 6 ; 
         FIG. 10  is a detailed top view of the screen assembly of  FIG. 6 ; 
         FIG. 11  is a top view of a backwash tube assembly in accordance with an embodiment of the present invention; 
         FIG. 12  is a first side view of the backwash tube assembly of  FIG. 11 ; 
         FIG. 13  is a second side view of the backwash tube assembly of  FIG. 11 ; 
         FIG. 14  is a schematic view of the filter system in accordance with the embodiment of  FIG. 1 ; 
         FIG. 15  is a schematic view of a filter system in accordance with another embodiment of the present invention; 
         FIG. 16  is a schematic view of a filter system in accordance with a further embodiment of the present invention; and 
         FIGS. 17A-C  illustrate positions of valves in a module control assembly in accordance with an embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The subject of this application is a filtration system including various components, which may be implemented to filter a process flow. Although particular combinations of components are used to achieve a desired process flow, variations on those combinations can be used to achieve the same filtration system. 
     As illustrated in  FIGS. 1-5  and  14  of the present invention, a filter system  10  can include a frame  11 , an influent chamber  12 , a control panel  13 , influent control assembly  20 , effluent control assembly  30 , modules  40 ,  60 ,  80 ,  100 ,  120 , control assemblies  50 ,  70 ,  90 ,  110 ,  130  and a backwash control assembly  140 . The frame  11  provides structural support for the components of the filter system  10  and is sized to meet the flow requirements of a given process. The frame  11  can be made of structural members, such as channels, angles, beams, tubes and/or plates. The structural members can be made of a metal or plastic material, such as steel, stainless steel, polypropylene or other type of structural material. The frame  11  is arranged to provide a base  14  and a side structure  15 . The base  14  provides support for the filter system  10  on a floor or substrate. The side structure  15  provides support for the control panel  13  and control assemblies  20 ,  30 ,  50 ,  70 ,  90 ,  110 ,  130 ,  140 . 
     The control panel  13  includes various controls for monitoring the flow through the filter system  10 . The control panel  13  can include relays, switches, alarms, sensors, gauges, lights and displays for monitoring and controlling certain aspects of the filter system  10 , which will become more apparent in the disclosure below. For example, an alarm can sound externally, indicate a malfunction and a malfunction location. An electrical source (not shown) is connected to the control panel  13  when the filter system  10  is in operation. 
     The influent chamber  12  is provided at the top or initial stage of the filter system  10 . Influent from an influent source flows into the influent chamber  12  to provide detention time before the flow passes through the modules  40 ,  60 ,  80 ,  100 ,  120 . The influent control assembly  20  includes valve  21 , valve  22 , relief valve  23 , valve  24 , valve  25  and a pressure control assembly  26 . The influent is in communication with the influent chamber  12  and is controlled by valve  21  and valve  22 . The valve  21 , in the preferred embodiment, can be an automatic valve, such as a solenoid valve or other structure for controlling flow. The valve  22 , in the preferred embodiment, can be a manual valve, such as a butterfly valve, ball valve, gate valve or other structure for controlling flow. 
     Overflow from the influent chamber  12  is controlled by the relief valve  23 . The relief valve  23 , in the preferred embodiment, can be a pressure relief valve, safety relief valve or other structure for providing pressure relief in a fluid line. If the influent chamber  12  becomes backed up due to positive flow not flowing through the filter system  10 , pressure could build up in the influent chamber  12 . When a predetermined pressure is exceeded in the chamber, the relief valve  23  opens to allow the excess pressure and flow to escape out of the influent chamber  12  into the environ. 
     The valve  24  and valve  25  provide a control device to direct the flow from backwashing any of the lower filter medias at controlled intervals, such as when a pressure limit is exceeded or at a certain time during a given day. The valve  24 , in the preferred embodiment, can be a manual valve, such as a butterfly valve, ball valve, gate valve or other structure for controlling flow. The valve  25 , in the preferred embodiment, can be an automatic valve, such as a solenoid valve or other structure for controlling flow. The valves  24  and  25  are in fluid communication between the influent chamber  12  and the backwash flow line. The backwash flow is preferably either recycled through the filter system  10  or temporarily stored in a holding tank. 
     The pressure control assembly  26  includes a pressure gauge, a pressure transmitter and a bypass valve. The pressure gauge measures the pressure in the influent chamber  12 . The pressure control assembly  26  sends the measured pressure reading to the control panel  13 , where a pressure difference can be calculated between the first module  40  and the second module  60  by comparing measurements from the pressure control assembly  55  to the pressure control assembly  26 . The pressure control assembly  26  can be set to a predetermined pressure difference. For example, the pressure difference can be set between about 5 PSI and 25 PSI, and more specifically at about 10 PSI. When the pressure difference is exceeded, a signal can be sent to various valves to redirect, recycle the flow and/or backwash the filter system  10 , for instance, a signal can be sent to the bypass valve in the pressure control assembly  26  to open the bypass valve, bypassing the flow to a subsequent module for further filtration. 
     The effluent control assembly  30  includes valve  31 , valve  32  and pressure control assembly  33 . The valve  31  and valve  32  provide a control device to direct the flow out from the filter system  10 . The valve  31 , in the preferred embodiment, can be a manual valve, such as a butterfly valve, ball valve, gate valve or other structure for controlling flow. The valve  32 , in the preferred embodiment, can be an automatic valve, such as a solenoid valve or other structure for controlling flow. The pressure control assembly  33  includes a pressure gauge and a pressure transmitter. The pressure control assembly measures the pressure at the effluent line and sends the measured pressure reading to the control panel  13 . The valves  31  and  32  are in fluid communication between the filter system  10  and the effluent line. The effluent flow is directed down stream to a holding tank, an apparatus for further processing, or otherwise disposed, for example, in a water reserve, river, lake or ocean. 
     The first module  40  is provided below the influent chamber  12 . The first module  40  includes an upper section  41 , a lower section  42 , a screen assembly  43 , filter media  44 , a screen assembly  45  and a backwash tube assembly  46 . The screen assemblies  43 ,  45  and filter media  44  are provided in the upper section  41  of the first module  40 . The filter media  44  is provided between the screen assembly  43  and screen assembly  45 . The screen assemblies  43 ,  45  enclose and retain the filter media  44  within the upper section  41 . The filter media  44  can include 1.0 mm walnut shells, anthracite, sand and/or garnet. For example, the filter media can be sand sized between No. 4 0.80 mm, No. 3 0.45 mm and No. 2 0.25 mm. 
     The backwash tube assembly  46  is provided in the lower section  42  below the screen assembly  45 . When the filter system  10  is backwashing the first module  40 , the backwash tube assembly  46  provides reverse flow through the filter media  44  to clean any accumulated solids from the filter media  44 . The backwash flow is directed through the first module  40  and into the influent chamber  12  where the flow is directed to the backwash flow line. 
     The control assembly  50  includes valve  51 , valve  52 , valve  53 , valve  54  and a pressure control assembly  55 . The backwash flow is directed from a backwash source to the first module  40  and is controlled by valve  51  and valve  52 . The valve  51 , in the preferred embodiment, can be an automatic valve, such as a solenoid valve or other structure for controlling flow. The valve  52 , in the preferred embodiment, can be a manual valve, such as a butterfly valve, ball valve, gate valve or other structure for controlling flow. 
     The valve  53  and valve  54  provide a control device to direct the flow from backwashing any of the lower filter media. The valve  53 , in the preferred embodiment, can be a manual valve, such as a butterfly valve, ball valve, gate valve or other structure for controlling flow. The valve  54 , in the preferred embodiment, can be an automatic valve, such as a solenoid valve or other structure for controlling flow. The valves  53  and  54  are in fluid communication with the first module  40  and the backwash flow line. 
     The pressure control assembly  55  includes a pressure gauge, a pressure transmitter and a bypass valve. The pressure gauge measures the pressure in the upper section of the second module  60 . The pressure control assembly  55  sends the measured pressure reading to the control panel  13 , where a pressure difference can be calculated between adjacent modules by comparing measurements from the pressure control assembly  26  or the pressure control assembly  75  to the pressure control assembly  55 . The pressure control assembly  55  can be set to a predetermined pressure difference. For example, the pressure difference can be set between about 5 PSI and 25 PSI, and more specifically at about 10 PSI. When the pressure difference is exceeded, a signal can be sent to various valves to redirect, recycle the flow and/or backwash the filter system  10 , for instance, a signal can be sent to the bypass valve in the pressure control assembly  55  to open the bypass valve, bypassing the flow to a subsequent module for further filtration. 
     The second module  60  is provided between the first module  40  and the third module  80 . The second module  60  includes an upper section  61 , a lower section  62 , a screen assembly  63 , filter media  64 , a screen assembly  65  and a backwash tube assembly  66 . The screen assemblies  63 ,  65  and filter media  64  are provided in the upper section  61  of the second module  60 . The filter media  64  is provided between the screen assembly  63  and screen assembly  65 . The screen assemblies  63 ,  65  enclose and retain the filter media  64  within the upper section  61 . The filter media  64  can include similar materials to those discussed above with respect to filter media  44 . 
     The backwash tube assembly  66  is provided in the lower section  62  below the screen assembly  65 . When the filter system  10  is backwashing the second module  60 , the backwash tube assembly  66  provides reverse flow through the filter media  64  to clean any accumulated solids from the filter media  64 . The backwash flow is directed through the second module  60  and into the first module  40  where the flow is directed to the backwash flow line. 
     The control assembly  70  includes valve  71 , valve  72 , valve  73 , valve  74  and a pressure control assembly  75 . The backwash flow is directed from a backwash source to the second module  60  and is controlled by valve  71  and valve  72 . The valve  71 , in the preferred embodiment, can be an automatic valve, such as a solenoid valve or other structure for controlling flow. The valve  72 , in the preferred embodiment, can be a manual valve, such as a butterfly valve, ball valve, gate valve or other structure for controlling flow. 
     The valve  73  and valve  74  provide a control device to direct the flow from backwashing any of the lower filter media. The valve  73 , in the preferred embodiment, can be a manual valve, such as a butterfly valve, ball valve, gate valve or other structure for controlling flow. The valve  74 , in the preferred embodiment, can be an automatic valve, such as a solenoid valve or other structure for controlling flow. The valves  73  and  74  are in fluid communication with the second module  60  and the backwash flow line. 
     The pressure control assembly  75  includes a pressure gauge, a pressure transmitter and a bypass valve. The pressure gauge measures the pressure in the upper section of the third module  80 . The pressure control assembly  75  sends the measured pressure reading to the control panel  13 , where a pressure difference can be calculated between adjacent modules by comparing measurements from the pressure control assembly  55  or the pressure control assembly  95  to the pressure control assembly  75 . The pressure control assembly  75  can be set to a predetermined pressure difference. For example, the pressure difference can be set between about 5 PSI and 25 PSI, and more specifically at about 10 PSI. When the pressure difference is exceeded, a signal can be sent to various valves to redirect, recycle the flow and/or backwash the filter system  10 , for instance, a signal can be sent to the bypass valve in the pressure control assembly  75  to open the bypass valve, bypassing the flow to a subsequent module for further filtration. 
     The third module  80  is provided between the second module  60  and the fourth module  100 . The third module  80  includes an upper section  81 , a lower section  82 , a screen assembly  83 , filter media  84 , a screen assembly  85  and a backwash tube assembly  86 . The screen assemblies  83 ,  85  and filter media  84  are provided in the upper section  81  of the third module  80 . The filter media  84  is provided between the screen assembly  83  and screen assembly  85 . The screen assemblies  83 ,  85  enclose and retain the filter media  84  within the upper section  81 . The filter media  84  can include similar materials to those discussed above with respect to filter media  44 . 
     The backwash tube assembly  86  is provided in the lower section  82  below the screen assembly  85 . When the filter system  10  is backwashing the third module  80 , the backwash tube assembly  86  provides reverse flow through the filter media  84  to clean any accumulated solids from the filter media  84 . The backwash flow is directed through the third module  80  and into the second module  60  where the flow is directed to the backwash flow line. 
     The control assembly  90  includes valve  91 , valve  92 , valve  93 , valve  94  and a pressure control assembly  95 . The backwash flow is directed from a backwash source to the third module  80  and is controlled by valve  91  and valve  92 . The valve  91 , in the preferred embodiment, can be an automatic valve, such as a solenoid valve or other structure for controlling flow. The valve  92 , in the preferred embodiment, can be a manual valve, such as a butterfly valve, ball valve, gate valve or other structure for controlling flow. 
     The valve  93  and valve  94  provide a control device to direct the flow from backwashing any of the lower filter media. The valve  93 , in the preferred embodiment, can be a manual valve, such as a butterfly valve, ball valve, gate valve or other structure for controlling flow. The valve  94 , in the preferred embodiment, can be an automatic valve, such as a solenoid valve or other structure for controlling flow. The valves  93  and  94  are in fluid communication with the third module  80  and the backwash flow line. 
     The pressure control assembly  95  includes a pressure gauge, a pressure transmitter and a bypass valve. The pressure gauge measures the pressure in the upper section of the fourth module  100 . The pressure control assembly  95  sends the measured pressure reading to the control panel  13 , where a pressure difference can be calculated between adjacent modules by comparing measurements from the pressure control assembly  75  or the pressure control assembly  115  to the pressure control assembly  95 . The pressure control assembly  95  can be set to a predetermined pressure difference. For example, the pressure difference can be set between about 5 PSI and 25 PSI, and more specifically at about 10 PSI. When the pressure difference is exceeded, a signal can be sent to various valves to redirect, recycle the flow and/or backwash the filter system  10 , for instance, a signal can be sent to the bypass valve in the pressure control assembly  95  to open the bypass valve, bypassing the flow to a subsequent module for further filtration. 
     The fourth module  100  is provided between the third module  80  and the fifth module  120 . The fourth module  100  includes an upper section  101 , a lower section  102 , a screen assembly  103 , filter media  104 , a screen assembly  105  and a backwash tube assembly  106 . The screen assemblies  103 ,  105  and filter media  104  are provided in the upper section  101  of the fourth module  100 . The filter media  104  is provided between the screen assembly  103  and screen assembly  105 . The screen assemblies  103 ,  105  enclose and retain the filter media  104  within the upper section  101 . The filter media  104  can include similar materials to those discussed above with respect to filter media  44 . 
     The backwash tube assembly  106  is provided in the lower section  102  below the screen assembly  105 . When the filter system  10  is backwashing the fourth module  100 , the backwash tube assembly  106  provides reverse flow through the filter media  104  to clean any accumulated solids from the filter media  104 . The backwash flow is directed through the fourth module  100  and into the third module  80  where the flow is directed to the backwash flow line. 
     The control assembly  110  includes valve  111 , valve  112 , valve  113 , valve  114  and a pressure control assembly  115 . The backwash flow is directed from a backwash source to the fourth module  100  and is controlled by valve  111  and valve  112 . The valve  111 , in the preferred embodiment, can be an automatic valve, such as a solenoid valve or other structure for controlling flow. The valve  112 , in the preferred embodiment, can be a manual valve, such as a butterfly valve, ball valve, gate valve or other structure for controlling flow. 
     The valve  113  and valve  114  provide a control device to direct the flow from backwashing any of the lower filter media. The valve  113 , in the preferred embodiment, can be a manual valve, such as a butterfly valve, ball valve, gate valve or other structure for controlling flow. The valve  114 , in the preferred embodiment, can be an automatic valve, such as a solenoid valve or other structure for controlling flow. The valves  113  and  114  are in fluid communication with the fourth module  100  and the backwash flow line. 
     The pressure control assembly  115  includes a pressure gauge and a pressure transmitter. The pressure gauge measures the pressure in the upper section of the fifth module  120 . The pressure control assembly  115  sends the measured pressure reading to the control panel  13 , where a pressure difference can be calculated between adjacent modules by comparing measurements from the pressure control assembly  33  or the pressure control assembly  95  to the pressure control assembly  115 . The pressure control assembly  115  can be set to a predetermined pressure difference. For example, the pressure difference can be set between about 5 PSI and 25 PSI, and more specifically at about 10 PSI. When the pressure difference is exceeded, a signal can be sent to various valves to redirect, recycle the flow and/or backwash the filter system  10 . 
     The fifth module  120  is provided below the fourth module  100  and the effluent line. The fifth module  120  includes an upper section  121 , a lower section  122 , a screen assembly  123 , filter media  124 , a screen assembly  125  and a backwash tube assembly  126 . The screen assemblies  123 ,  125  and filter media  124  are provided in the upper section  121  of the fifth module  120 . The filter media  124  is provided between the screen assembly  123  and screen assembly  125 . The screen assemblies  123 ,  125  enclose and retain the filter media  124  within the upper section  121 . The filter media  124  can include similar materials to those discussed above with respect to filter media  44 . 
     The backwash tube assembly  126  is provided in the lower section  122  below the screen assembly  125 . When the filter system  10  is backwashing the fifth module  120 , the backwash tube assembly  126  provides reverse flow through the filter media  124  to clean any accumulated solids from the filter media  124 . The backwash flow is directed through the fifth module  120  and into the fourth module  100  where the flow is directed to the backwash flow line. 
     The control assembly  130  includes valve  131  and valve  132 . The backwash flow is directed from a backwash source to the fifth module  120  and is controlled by valve  131  and valve  132 . The valve  131 , in the preferred embodiment, can be a manual valve, such as a butterfly valve, ball valve, gate valve or other structure for controlling flow. The valve  132 , in the preferred embodiment, can be an automatic valve, such as a solenoid valve or other structure for controlling flow. 
     The backwash control assembly  140  includes valve  141 , valve  142 , valve  143  and valve  144 . The backwash flow is directed from a backwash source to any of the modules  40 ,  60 ,  80 ,  100 ,  120 . The valve  141 , in the preferred embodiment, can be a manual valve, such as a butterfly valve, ball valve, gate valve or other structure for controlling flow. The manual valves in the filter system  10  are provided to allow an operator to manually shut down a section of the filter system for repair or replacement of specific components or to redirect flow to other desired areas. 
     The valve  142  and valve  143  can be control valves to prevent flow from returning or otherwise being misdirected through the lines. The valve  142  is provided in the backwash line and valve  143  is provided in a compressed air line. The compressed air line is in communication with an air source. The compressed air forces air into the backwash line to push the backwash flow up through the filter media being backwashed. The valve  144 , in the preferred embodiment, can be an automatic valve, such as a solenoid valve or other structure for controlling flow. The valve  144  is in fluid communication with the compressed air line. The compressed air flow is controlled by valve  144 . 
     As shown in  FIGS. 6-10 , a screen assembly  200  includes a first screen  201 , a first backing screen  202 , a filter cloth  203 , a second backing screen  204 , a second screen  205  and a seal  206 . The filter cloth  203  is provided between the first backing screen  202  and the second backing screen  204 . The filter cloth  203  can be selected to have a specific mesh size to meet a desired application. The first screen  201  is provided above the first backing screen  202  and the second screen  205  is provided below the second backing screen  204 . The seal  206  can be provided around the outer edge of the screen assembly  200  to seal and enclose the first and second screens  201 ,  205 , the first and second backing screens  202 ,  204  and filter cloth  203  as shown in  FIG. 9 . The seal  206  can be made of a pliable material, such as plastic, foam or rubber. The seal  206  defines an effective portion of the screen assembly  200 . The screen assembly  200  can be sized according to the influent parameters of the given process. For example, the effective portion of the screen assembly  200  can have a diameter of about 33.25 inches. 
     The screen assembly  200  can include fasteners  210  to attach components such as a backwash tube assembly. The fasteners  210  can include bolts  211 , nuts  212  and washers  213 . The bolts  211  can be eyebolts made of a metal or plastic material, such as steel, stainless steel, polypropylene or other type of structural material. For example, the bolts  211  can be ¼ inch—20 stainless steel eyebolts. The nuts  212  can be hex nuts, locking nuts or other structures for fastening, which are sized to match each of the bolts  211 . Each of the bolts  211  can be inserted into the side of the screen assembly  200  having the second screen  205  and attached with one of the washers  213  and nuts  212  on the side having the first screen  201 . For example, the fasteners  210  can include two fasteners  210  equally spaced from a center point and aligned along a line passing through the center point as shown in  FIG. 6 . 
     Fasteners  220  can be used to tie the components of the screen assembly  200  together along the perimeter. The fasteners  220  include bolts  221 , nuts  222  and washers  223 . The bolts  221  can be made of a metal or plastic material, such as steel, stainless steel, polypropylene or other type of structural material. For example, the bolts  221  can be a ¼ inch—20 stainless steel bolts. The nuts  222  can be hex nuts, locking nuts or other structures for fastening, which are sized to match each of the bolts  221 . Each of the bolts  221  can be inserted into one side of the screen assembly  200  and attached with one of the washers  223  and nuts  222  on the other side. For example, the fasteners  220  can include twelve fasteners  220  equally spaced along the perimeter of the screen assembly as shown in  FIG. 6 . 
     The first and second backing screens  202 ,  204  can have a perforation pattern  230  made from apertures  231 , as shown in  FIG. 10 . For example, the apertures  231  can be about 0.25 inch diameter holes spaced at about 0.312 inches apart from each other along a horizontal line and spaced about 0.624 inches from the next aperture along the same horizontal line. Also, the apertures  231  can be spaced at about 0.27 inches apart from each other along a vertical line and spaced about 0.54 inches from the next aperture along the same vertical line. 
     Referring to  FIGS. 11-13 , a backwash tube assembly  300  includes a fitting  301 , a sleeve  302 , tubing  303  and backwash tubing  310 . The fitting  301  is attached to the sleeve  302  and the sleeve  302  is attached to the tubing  303 . A control assembly is attached to the fitting  301  to provide backwash flow to the backwash tube assembly  300 . The backwash tubing  310  can be shaped to provide a backwash spray around the screen assembly  200  and can be made of a material, such as steel, stainless steel, plastic or other type of tubing material known to one skilled in the art. For example, the backwash tube assembly  300  can be arranged in the shape of a circle, square, triangle, octagon, or other arrangement for dispersing a fluid. If the backwash tube assembly is octagonal shaped, the backwash tubing  310  can include a tee  311 , elbows  312 , tubing  313  and tubing  314 . The elbows can be eight (8) 45 degree elbows made of 304 stainless steel. The tubing  313  can be three (3) short lengths of tubing and tubing  314  can be four (4) long lengths of tubing. The tubing  313  is arranged on radial lines equally spaced at 90 degrees from the tee  311 . The tubing  314  is arranged on radial lines equally spaced at 45 degrees from the tee  311 . The tee  311 , elbows  312  and tubing  313 ,  314  are arranged to form an octagonal shape as shown in  FIG. 11 . The backwash tubing  310  includes orifices  315  spaced along the tee  311 , elbows  312  and tubing  313 ,  314  to provide an outlet for the backwash flow. The orifices  315  can be about 0.125 inch to about 0.172 inch diameter holes drilled into the backwash tubing  310 . 
     In  FIG. 14 , an embodiment of the operation of the filter system  10  is disclosed. For example, the filter system is arranged as disclosed above. Each of the modules includes a layer of sand between the screen assemblies. In normal operation, the influent flow is introduced into the influent chamber  20  in a forward flow, meaning flow through the filter system caused mainly by forced or pressurized flow through the filter system. The flow is distributed across the influent chamber  20  then through the first module  40 . While passing through the first module  40 , the flow is passes through the upper section  41  to the lower section  42 . In the upper section  41  the flow first passes through the screen assembly  43  then the filter media  44  and finally the screen assembly  45 . The screen assemblies and filter media are selected to filter particles from the flow to treat the influent. The treatment of the influent starts with the largest particles being removed from the first module  40 , then gradually providing finer media throughout the other modules until the smallest particles to be treated are removed in the fifth module  120 . After the flow passes through the fifth module  120 , the flow is filtered and is directed out from the filter system  10 . 
     Filter media can be arranged to include larger media at the top of the filter system  10  and smaller particles at the bottom. For example, the first module  40  can include about 1.0 millimeter walnut shells, anthracite or No. 4 (0.80 millimeter) sand; the intermediate modules can include walnut shells, anthracite, No. 3 (0.45 millimeter) sand or No. 2 (0.25 millimeter) sand; and the fifth module  120  can include 0.2 garnet. Another aspect of providing variations in the backwash flow is to account for the different types of media provided in each module. The modules prevent the different types of filter media from being mixed together when the filter system is backwashed. 
     When any of the modules become occluded, a backwash flow is introduced into the filter system  10 . The modules may become occluded after solids are built up on the screen assemblies and/or in the filter media. Each of the pressure sensors are set to monitor the pressure in the respective section of the filter system  10 . For example, the pressure sensors can be preset to a limit of about 5 PSI to about 15 PSI, and more specifically at about 10 PSI. For example, the pressure sensors can be set to open the bypass valves at about 8 PSI on any one module and about 9 PSI on another. Each module is set to a desired pressure differential, to meet a given process requirement. The pressure settings can be programmed at the process site with a PLC or remotely using a modem from a computer. Once the pressure differential across a module exceeds the preset limit, the control assembly bypasses the occluded portion by opening a bypass valve creating a bypass flow. The bypass flow then continues to be filtered in the remaining modules bypassing the occluded module. 
     The pressure sensors can be set to trigger the backwash flow at a desired pressure, e.g., 10 PSI, when all five modules become occluded. The backwash flow can then be introduced to one or more modules to unclog them. This option reduces the amount of time needed to backwash the filter system  10 . Another option would be to set the pressure sensors at the bypass valves at about 10 PSI and the pressure sensors at the backwash control assembly at about 8 PSI to about 9 PSI. In this manner, the filter system  10  will backwash each module when the module becomes occluded. The bypass valves can also be used to bypass a module that cannot be backwashed due to a malfunction in the system. 
     Once the fifth module is occluded, however, the filter system is shutdown until the occluded modules are backwashed to reset the filter system  10 . Usually, the entire filter system is backwashed at this point. An aspect of the present invention is that each individual module can be backwashed independently. To unclog a module, a backwash flow is introduced through backwash valves to a backwash tube. The backwash flow is pressurized to provide a reverse flow through the screen assemblies and filter media to remove accumulated particles from the filter system  10  and to a backwash outlet. The backwash flow can be introduced to a module during operation or when the filter system is shut down. The filter system  10  includes control assemblies outside the modules to provide easy accessibility to the components of the filter system  10  for maintenance and repair. 
     The backwash flow can be set to a desired interval to backwash each module separately at a specified time. Each module can also be set to a desired backwash duration. For example, the duration may be set to backwash for a few seconds to multiple minutes, such as about fifteen minutes. The duration and quantity of the backwash is calculated over a 24 hour period and stored in a computer. The filter system  10  can be preset to backwash during a specified time of each day to meet any given water requirements in another section of operation at a plant. In addition, an alarm can be provided to sound externally from the PLC to indicated a malfunction and the location of the malfunction. 
     The filter system  10  can be provided in parts for easy assembly, maintenance and repair. For example, the filter system  10  can be provided with an upper section  16  and a lower section  17  having a seal  18  between the upper and lower sections  16 ,  17  as shown in  FIGS. 2-5 . Additionally, any one or more of the modules can be the removed to repair or replace damaged media without replacing all of the filter media in the filter system  10 . 
     As illustrated in  FIG. 15 , an alternative embodiment of a filter system  400  is disclosed. The filter system  400  is operated in a normal forward flow when the influent flows sequentially through a set of modules  410  without backwashing or bypassing any of the modules. The set of modules  410  includes a first module  411 , a second module  412 , a third module  413 , a forth module  414  and a fifth module  415 . Each of the modules  410  include a screen assembly and filter media similar to those discussed above with respect to the filter system  10 . The filter systems also includes an influent control assembly  420 , a module control assembly  430 , a backwash control assembly  440 , a pressure control assembly  460  and an effluent control assembly  470 . Each of these control assemblies may include one or more of each of the following: valves, pressure sensors, piping, switches and other components known in the art to control fluid flow. 
     The influent control assembly  420  includes valves  421  through  428 . Valve  421  is positioned between the influent source and the inlet to the filter system  400 . Valve  422  is positioned between valve  421  and the first module  411 . Valve  423  is arranged in a fluid line connected between the first module  411  and the second module  412  and positioned between the line connecting valve  421  and valve  422 . Valve  424  is arranged in a fluid line connected between the second module  412  and the third module  413  and positioned between the line connecting valve  423  and valve  425 . Valve  425  is arranged in a fluid line connected between the third module  413  and the fourth module  414  and positioned between the line connecting valve  424  and valve  426 . Valve  426  is arranged in a fluid line connected between the fourth module  414  and the fifth module  415  and a recycle line to an influent feed tank. Valve  426  is positioned between the line connecting valve  425  and valves  427 ,  428 . Valve  427  controls the flow to the recycle line to direct the flow towards the influent feed tank. Valve  428  controls the flow to the fifth module  415 . 
     The module control assembly  430  includes valves  431  through  438 . Valves  431  and  432  are positioned between the first module  411  and the second module  412 . Valve  431  controls flow up through the first module  411 . Valve  432  controls flow down through the second module  412 . Valves  433  and  434  are positioned between the second module  412  and the third module  413 . Valve  433  controls flow up through the second module  412 . Valve  434  controls flow down through the third module  413 . Valves  435  and  436  are positioned between the third module  413  and the fourth module  414 . Valve  435  controls flow up through the third module  413 . Valve  436  controls flow down through the fourth module  414 . Valves  437  and  438  are positioned between the fourth module  414  and the fifth module  415 . Valve  437  controls flow up through the fourth module  414 . Valve  438  controls flow down through the fifth module  415 . 
     The backwash control assembly  440  includes valves  441  through  451 . Valves  441 ,  442  are in fluid connection with the first module  411 . Valve  441  is positioned between the first module  411  and a backwash outlet. Valve  442  is positioned between the first module  411  and the backwash inlet to direct flow from a backwash source up through the first module  411 . Valves  443 ,  444  are in fluid connection with the second module  412 . Valve  443  is positioned between the second module  412  and the backwash outlet. Valve  444  is positioned between the second module  412  and the backwash inlet to direct flow from the backwash source up through the second module  412 . Valves  445 ,  446  are in fluid connection with the third module  413 . Valve  445  is positioned between the third module  413  and the backwash outlet. Valve  446  is positioned between the third module  413  and the backwash inlet to direct flow from the backwash source up through the third module  413 . Valves  447 ,  448  are in fluid connection with the fourth module  414 . Valve  447  is positioned between the fourth module  414  and the backwash outlet. Valve  448  is positioned between the fourth module  414  and the backwash inlet to direct flow from the backwash source up through the fourth module  414 . Valves  449 ,  450  are in fluid connection with the fifth module  415 . Valve  449  is positioned between the fifth module  415  and the backwash outlet. Valve  450  is positioned between the fifth module  415  and the backwash inlet to direct flow from the backwash source up through the fifth module  415 . Valve  451  is positioned between the backwash source and valves  442 ,  444 ,  446 ,  448  and  450 . Valve  451  is a main shutoff valve for the backwash control assembly  440 . 
     The pressure control assembly  460  includes pressure sensors  461  through  466 . Pressure sensor  461  monitors the pressure in the first module  411 . Pressure sensor  462  monitors the pressure difference between the first module  411  and the second module  412 . Pressure sensor  463  monitors the pressure difference between the second module  412  and the third module  413 . Pressure sensor  464  monitors the pressure difference between the third module  413  and the fourth module  414 . Pressure sensor  465  monitors the pressure difference between the fourth module  414  and the fifth module  415 . Pressure sensor  466  monitors the pressure difference between the fifth module  415  and the effluent line. When a preset limit of pressure is exceeded in one of the pressure sensors  461  through  466 , the given pressure sensor sends a signal to a combination of valves to regulate the flow. 
     The effluent control assembly  470  includes valves  471  and  472 . Valves  471  and  472  are positioned between the fifth module  415  and the effluent line. Valve  471  directs effluent flow to a water discharge for further processing, use or disposal. Valve  472  directs flow to a test line for testing the fluid content and recycling through the filter system  400 . 
     In normal forward flow operation, valve  421  is open, as it will be whenever the filter system  400  is in operation. Valve  422  and valve  471  are open, as they will be whenever the filter system  400  is in operation, other than during certain times during backwashing discussed below. The valves in the module control assembly  430  are open to allow flow to pass downward through each of the modules. The valves in the backwash control assembly  440  are initially closed. Valves  423  through  428  are initially closed. Valve  472  is closed other than during effluent testing as noted below. During normal flow, the influent enters the top of the first module  411  and passes through each of the successive modules  412  through  415  to exit the bottom of the fifth module  415  and out the effluent flow line to the water discharge. 
     When a preset pressure change across the first module  411  is exceeded due to solids accumulating in the first module  411 , a signal is sent to indicate that the module requires backwashing. First, valve  423  opens to provide alternate flow to the second module  412  bypassing the first module  411 . Second, valves  422  and  431  close to isolate and bypass the first module  411 . Third, valves  441 ,  442  and  451  open to allow backwashing of the first module  411 . The backwash flow enters the bottom of the first module  411  through valve  442  and out valve  441  to a backwash outlet. The backwash flow removes any accumulated solids in the filter media in the first module  411 . After backwashing for a defined period, all valves return to the normal forward flow position discussed above. 
     When a preset pressure change across the second module  412  is exceeded due to solids accumulating in the second module  412 , a signal is sent to indicate that the module requires backwashing. First, valve  424  opens to provide alternate flow to the third module  413  bypassing the second module  412 . Second, valves  432  and  433  close to isolate and bypass the second module  412 . Third, valves  443 ,  444  and  451  open to allow backwashing of the second module  412 . The backwash flow enters the bottom of the second module  412  through valve  444  and out valve  443  to the backwash outlet. The backwash flow removes any accumulated solids in the filter media in the second module  412 . After backwashing for a defined period, all valves return to the normal forward flow position discussed above. 
     When a preset pressure change across the third module  413  is exceeded due to solids accumulating in the third module  413 , a signal is sent to indicate that the module requires backwashing. First, valve  425  opens to provide alternate flow to the fourth module  414  bypassing the third module  413 . Second, valves  434  and  435  close to isolate and bypass the third module  413 . Third, valves  445 ,  446  and  451  open to allow backwashing of the third module  413 . The backwash flow enters the bottom of the third module  413  through valve  446  and out valve  445  to the backwash outlet. The backwash flow removes any accumulated solids in the filter media in the third module  413 . After backwashing for a defined period, all valves return to the normal forward flow position discussed above. 
     When a preset pressure change across the fourth module  414  is exceeded due to solids accumulating in the fourth module  414 , a signal is sent to indicate that the module requires backwashing. First, valve  426  opens to provide alternate flow to the fifth module  415  bypassing the fourth module  414 . Second, valves  436  and  437  close to isolate and bypass the fourth module  414 . Third, valves  447 ,  448  and  451  open to allow backwashing of the fourth module  414 . The backwash flow enters the bottom of the fourth module  414  through valve  448  and out valve  447  to the backwash outlet. The backwash flow removes any accumulated solids in the filter media in the fourth module  414 . After backwashing for a defined period, all valves return to the normal forward flow position discussed above. 
     When a preset pressure change across the fifth module  415  is exceeded due to solids accumulating in the fifth module  415 , a signal is sent to indicate that the fifth module  415  requires backwashing. Although the fifth module can be independently backwashed using the following steps, the entire filter system  400  is usually backwashed once the fifth module  415  becomes occluded. If the fifth module  415  is bypassed, the effluent usually cannot be discharged as product and should be recycled. To backwash the fifth module independently, valves  427  and  428  open to provide flow to the influent feed tank. Then, valves  438  and  471  close to isolate the fifth module  415 . Next, valves  449 ,  450  and  451  open to allow backwashing of the fifth module  415 . The backwash flow enters the bottom of the fifth module  415  through valve  450  and out valve  449  to the backwash outlet. The backwash flow removes any accumulated solids in the filter media in the fifth module  415 . After backwashing for a defined period, all valves return to the normal forward flow position discussed above after restart flow has been evaluated. 
     During restart flow, valve  471  remains closed and valve  472  opens to allow recycle wasting restart flow. Restart flow is evaluated after the backwash cycle in the fifth module  415 . The flow is wasted or returned to the influent feed tank to insure that the product meets a defined water quality. After a predetermined restart flow period, the valves are returned to the normal forward flow positions. 
     As illustrated in  FIG. 16 , a further embodiment of a filter system  500  is disclosed. The filter system  500  is operated in a normal forward flow when the influent flows sequentially through a set of modules  510  without backwashing or bypassing any of the modules. The set of modules  510  includes a first module  511 , a second module  512 , a third module  513 , a forth module  514  and a fifth module  515 . Each of the modules  510  include a screen assembly and filter media similar to those discussed above with respect to the filter system  10 . The filter system  500  also includes an influent control assembly  520 , a module control assembly  530 , a backwash control assembly  540 , a pressure control assembly  560  and an effluent control assembly  570 . Each of these control assemblies may include one or more of each of the following: valves, pressure sensors, piping, switches and other components known in the art to control fluid flow. 
     The influent control assembly  520  includes valves  521  through  525 . Valve  521  is positioned between the influent source and the inlet to the filter system  500  at the first module  511 . Valve  522  is positioned in a fluid line between the valve  521  and the influent source and provides control to direct flow to a line between the first module  511  and the second module  512 , and to direct flow to a line between the second module  512  and the third module  513 . Valve  523  is positioned in a fluid line connected between the third module  513  and the fourth module  514  and positioned between the line connecting valve  522  and valve  524 . Valve  524  is arranged in a fluid line connected between the fourth module  514  and the fifth module  515  and positioned between the line connecting valve  523  and valve  525 . Valve  525  controls the flow to the recycle line to direct the flow towards the influent feed tank. 
     The module control assembly  530  includes valves  531  through  534 . Valve  531  is positioned between the first module  511  and the second module  512 . Valve  531  controls flow between the first module  511  and the second module  512 . Valve  532  is positioned between the second module  512  and the third module  513 . Valve  532  controls flow between the second module  512  and the third module  513 . Valve  433  is positioned between the third module  513  and the fourth module  514 . Valve  533  controls flow between the third module  513  and the fourth module  514 . Valve  534  is positioned between the fourth module  514  and the fifth module  515 . Valve  533  controls flow between the fourth module  514  and the fifth module  515 . Each of the valves in the module control assembly  530  includes a tee configuration having three operating positions. In position  1 , flow enters from the influent control assembly  520  and is directed down through the module below the valve as shown in  FIG. 17A . In position  2 , flow enters from the influent control assembly  520  and is directed down through the module above the valve as shown in  FIG. 17B . In position  3 , flow passes from one module located above the valve to another module located below the valve and is restricted from communication with the influent control assembly  520  as shown in  FIG. 17C . 
     The backwash control assembly  540  includes valves  541  through  551 . Valves  541 ,  542  are in fluid connection with the first module  511 . Valve  541  is positioned between the first module  511  and the backwash outlet. Valve  542  is positioned between the first module  511  and the backwash inlet to direct flow from the backwash source up through the first module  511 . Valves  543 ,  544  are in fluid connection with the second module  512 . Valve  543  is positioned between the second module  512  and the backwash outlet. Valve  544  is positioned between the second module  512  and the backwash inlet to direct flow from the backwash source up through the second module  512 . Valves  545 ,  546  are in fluid connection with the third module  513 . Valve  545  is positioned between the third module  513  and the backwash outlet. Valve  546  is positioned between the third module  513  and the backwash inlet to direct flow from the backwash source up through the third module  513 . Valves  547 ,  548  are in fluid connection with the fourth module  514 . Valve  547  is positioned between the fourth module  514  and the backwash outlet. Valve  548  is positioned between the fourth module  514  and the backwash inlet to direct flow from the backwash source up through the fourth module  514 . Valves  549 ,  550  are in fluid connection with the fifth module  515 . Valve  549  is positioned between the fifth module  515  and the backwash outlet. Valve  550  is positioned between the fifth module  515  and the backwash inlet to direct flow from the backwash source up through the fifth module  515 . Valve  551  is positioned between the backwash source and valves  542 ,  544 ,  546 ,  548  and  550 . Valve  551  is a main shutoff valve for the backwash control assembly  540 . 
     The pressure control assembly  560  includes pressure sensors  561  through  566 . Pressure sensor  561  monitors the pressure in the first module  511 . Pressure sensor  562  monitors the pressure difference between the first module  511  and the second module  512 . Pressure sensor  563  monitors the pressure difference between the second module  512  and the third module  513 . Pressure sensor  564  monitors the pressure difference between the third module  513  and the fourth module  514 . Pressure sensor  565  monitors the pressure difference between the fourth module  514  and the fifth module  515 . Pressure sensor  566  monitors the pressure difference between the fifth module  515  and the effluent line. When a preset pressure is exceeded in one of the pressure sensors  561  through  566 , the given pressure sensor sends a signal to a combination of valves to regulate the flow. 
     The effluent control assembly  570  includes valves  571  and  572 . Valves  571  and  572  are positioned between the fifth module  515  and the effluent line. Valve  571  directs effluent flow to a water discharge for further processing, use or disposal. Valve  572  directs flow to a test line for testing the fluid content and recycling through the filter system  500 . 
     In normal forward flow operation, valves  521  and  571  are open, as they will be whenever the filter system  500  is in operation. Valve  521  directs flow into the first module  511  from an influent source. The valves in the module control assembly  530  are arranged in position  3  to allow flow to pass downward through each of the modules. The valves in the backwash control assembly  540  and valves  522  through  525  are initially closed. Valve  572  is closed other than during effluent testing as noted below. Valve  572  is opened to test product water quality or to waste restart flow. When it is necessary to backwash the fifth module  515 , the discharge from the fourth module  514  may not be acceptable as product water. Thus, the flow is usually recycled while the fifth module  515  is being backwashed. Once the fifth module  515  is returned to operation, restart flow is recycled through the filter system  500  for a period until the treated flow meets a specified water quality. When the treated flow meets the specified water quality, the flow is returned to normal flow through the filter system  500 . During normal flow, the influent enters the top of the first module  511  and passes through each of the successive modules  512  through  515  to exit the bottom of the fifth module  515  and out the effluent flow line to the water discharge. 
     When a preset pressure change across the first module  511  is exceeded due to solids accumulating in the first module  511 , a signal is sent to indicate that the module requires backwashing. First, valve  522  opens to provide alternate flow to the second module  512  bypassing the first module  511 . Second, valve  521  closes to isolate and bypass the first module  511 . Third, valve  531  moves to position  1  to isolate the first module  511  and direct flow to the second module  512 . Then valves  541 ,  542  and  551  open to allow backwashing of the first module  511 . The backwash flow enters the bottom of the first module  511  through valve  542  and out valve  541  to the backwash outlet. The backwash flow removes any accumulated solids in the filter media in the first module  511 . After backwashing for a defined period, all valves return to the normal forward flow position discussed above. 
     When a preset pressure change across the second module  512  is exceeded due to solids accumulating in the second module  512 , a signal is sent to indicate that the module requires backwashing. First, valve  531  moves to position  2  and valve  532  moves to position  1  to isolate the second module  512  and direct flow through the third module  513 . Second, valves  543 ,  544  and  551  open to allow backwashing of the second module  512 . The backwash flow enters the bottom of the second module  512  through valve  544  and out valve  543  to the backwash outlet. The backwash flow removes any accumulated solids in the filter media in the second module  512 . After backwashing for a defined period, all valves return to the normal forward flow position discussed above. 
     When a preset pressure change across the third module  513  is exceeded due to solids accumulating in the third module  513 , a signal is sent to indicate that the module requires backwashing. First, valve  523  opens to provide alternate flow to the fourth module  514  bypassing the third module  513 . Second, valve  532  moves to position  2  and valve  533  moves to position  1  to isolate the third module  513  and direct flow through the fourth module  514 . Third, valves  545 ,  546  and  551  open to allow backwashing of the third module  513 . The backwash flow enters the bottom of the third module  513  through valve  546  and out valve  545  to the backwash outlet. The backwash flow removes any accumulated solids in the filter media in the third module  513 . After backwashing for a defined period, all valves return to the normal forward flow position discussed above. 
     When a preset pressure change across the fourth module  514  is exceeded due to solids accumulating in the fourth module  514 , a signal is sent to indicate that the module requires backwashing. First, valve  524  opens to provide alternate flow to the fifth module  515  bypassing the fourth module  514 . Second, valve  533  moves to position  2  and valve  534  moves to position  1  to isolate the fourth module  514  and direct flow through the fifth module  515 . Third, valves  547 ,  548  and  551  open to allow backwashing of the fourth module  514 . The backwash flow enters the bottom of the fourth module  514  through valve  548  and out valve  547  to the backwash outlet. The backwash flow removes any accumulated solids in the filter media in the fourth module  514 . After backwashing for a defined period, all valves return to the normal forward flow position discussed above. 
     When a preset pressure change across the fifth module  515  is exceeded due to solids accumulating in the fifth module  515 , a signal is sent to indicate that the fifth module  515  requires backwashing. Although the fifth module  515  can be independently backwashed using the following steps, the entire filter system  500  is usually backwashed once the fifth module  515  becomes occluded. Effluent from module  514  may not be acceptable as product or as waste in some environs. Consequently, when module  515  is occluded, the filtration process is usually suspended and the entire filter is backwashed. If module  515  is to be backwashed independently, the valve  525  opens to provide flow to the influent feed tank. Then, valve  534  moves to position  2  and valve  571  closes to isolate the fifth module  515 . Next, valves  549 ,  550  and  551  open to allow backwashing of the fifth module  515 . The backwash flow enters the bottom of the fifth module  515  through valve  550  and out valve  549  to the backwash outlet. The backwash flow removes any accumulated solids in the filter media in the fifth module  515 . After backwashing for a defined period, all valves return to the normal forward flow position discussed above after restart flow has been evaluated. 
     During restart flow, valve  571  remains closed and valve  572  opens to allow recycle wasting restart flow. Restart flow is evaluated after the backwash cycle in the fifth module  515 . The flow is wasted or returned to the influent feed tank to insure that the product meets a defined water quality. After a predetermined restart flow period, the valves are returned to the normal forward flow positions. 
     The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. For example, the quantity of modules and filter media is determined by the specific characteristics of the particular flow to be treated. Although the disclosed embodiments of the invention include five modules, other embodiments can include more or less, such as two to fifteen modules. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Technology Classification (CPC): 1