Patent Publication Number: US-2021170454-A1

Title: Method and apparatus for cleaning large pipes, such as storm drain conduits

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of U.S. patent application Ser. No. 15/910,303, which was filed on Mar. 2, 2018 and entitled “Method And Apparatus For Cleaning Large Pipes, Such As Storm Drain Conduits.” The complete disclosure of the above application is hereby incorporated by reference for all purposes. 
    
    
     BACKGROUND OF THE INVENTION 
     The subject matter of this application relates to cleaning of conduits through which liquids are transported primarily by gravity flow, and in particular to a method and apparatus for cleaning storm drains, sanitary sewers and related conduits of accumulated clay, sand, gravel, trash, and other sediment. 
     Underground conduits are used to drain many types of liquid wastes from numerous and varied sources and to transport such liquid wastes to places where they are accumulated for treatment or discharge into places such as large bodies of water. Periodic cleaning of such conduits is required to maintain their capacity. Various ways for cleaning sanitary sewers are well-known. 
     Storm drain conduits, more than sanitary sewers, are likely to suffer from accumulation of various materials introduced into them as a result of occasional heavy rains falling on city streets, parking lots, and other paved areas. Storm drain conduits also receive runoff that has originated as rainfall on open land or from snowmelt and that is drained through conduits ultimately discharging into storm drain conduit systems in suburban or urban areas. 
     Rocks, gravel, sand, mud, and other suspended materials are often carried into and through storm drain conduits by storm runoff that is high in volume. Once the runoff volume decreases after a storm the speed of water flow through a storm drain conduit is reduced. Once the speed of flow of water decreases below about 3 miles per hour a great deal of the material carried in storm runoff settles and becomes sediment on the bottom of a storm drain conduit, remaining in place once runoff from a particular storm subsides. Such sediments accumulate over time, often to the point of greatly impeding flow through such storm drain conduits so that subsequent storm runoff may be blocked to the point of backing up, leaving the storm drain conduits ineffective. 
     Various apparatus and methods are used to clean deposited materials from storm drain conduits at lesser cost than by manually digging such materials out and carting them away. Various ways of cleaning storm drain conduits use water to flush deposited materials from storm drain conduits, but commonly used step cleaning methods and equipment primarily designed for cleaning sanitary sewers require large amounts of clean water to flush deposits from such storm drain conduits. The costs for hauling clean water to storm drain conduit cleaning sites and for hauling away dirty water and the materials removed from the storm drain conduits are significant. 
     In one commercially used manner of cleaning sanitary sewers and storm drain conduits a nozzle arrangement called a sewer jet is provided with a very high-pressure flow of water utilized to loosen sediment. The nozzle arrangement is sent a limited distance upstream through the drain conduit being cleaned, with the nozzles directing streams of highly pressurized water in a downstream direction within the storm drain conduit. The nozzle arrangement is moved a limited distance upstream and then retracted in a downstream direction. Forceful streams of highly pressurized water from the nozzles, with pressures in excess of 1300 psi and usually in the range from 2000 psi to 3000 psi, are used to dislodge and loosen sediment and then the connecting hose is retracted to pull a portion of the loosened sediment and accompanying water back downstream to a location where access to the interior of the sewer is available. The dirty water and sediment can be collected by a vacuum truck, to be hauled away for separation and disposal. While some sewer cleaning units are equipped to provide higher volumes of pressurized water to the nozzle arrangement, most such units are limited to 80 gallons per minute. 
     For the very high pressure utilized in such known systems the water utilized must be clean of substantially all particles larger than 100 μm, in order to avoid destructive wear on the piston pumps utilized to develop the high pressures required. In one previously known apparatus for cleaning sanitary sewers, low viscosity dirty water and entrained sand, gravel, and other sediment removed from a sanitary sewer is pumped into a tank where sediment is allowed to settle out. Water is then removed from an upper portion of the tank through a screen and is cleaned further in a centrifugal cleaning device. The cleaned water is then reused for further sewer cleaning, but such a recycling system can only separate solids of a higher specific gravity from a slurry liquid with a very low viscosity as liquid has to pass a 100 μm screen. Materials loosened in storm drain conduits typically have a much higher concentration of suspended and colloidal solids. Further, with the exception of the blast from the nozzle, the volume of flow from the nozzle is not enough in and of itself to affect a flow in the conduits to convey the solids. 
     Storm drain conduits are often located along highways, and cleaning thus requires traffic control around the cleaning equipment. This may require the work to be done only during certain non-rush-hour periods of the day. In that case, set-up and tear-down of storm drain conduit cleaning equipment encroaches on the time during which storm drain conduits can be cleaned. 
     The number of large trucks involved in hauling clean water to and dirty water away from a site where a storm drain conduit is being cleaned using such conventional methods is expensive. Such trucks can also present problems for traffic in the vicinity and can cause undesirable wear and tear on streets and highways where storm drain conduits are being cleaned. Further, the clean water may be in precious supply due to location, and the dirty water still requires treatment for disposal or eventual reuse. 
     What is desired, then, is apparatus and a method for its use in cleaning conduits such as storm drain conduits of various sizes efficiently and without needing great amounts of water to be hauled to and away from a site where a conduit is being cleaned, thus saving clean water that could be used for other purposes, reducing traffic, and reducing costs to allow more storm drain conduits to be cleaned affordably keeping more sediments from going downstream contaminating our waterways. 
     SUMMARY OF THE INVENTION 
     The invention disclosed in the present application incorporates apparatus and methods for its use for flushing deposited sediment from conduits such as storm drain conduits of various sizes, and provides for repeated reuse of a quantity of water for cleaning such conduits. 
     In accordance with the method disclosed in this application, water that is not so clean as is required for the use of high-pressure piston pumps and small orifice nozzle tips can be used to wash sediment from a storm drain conduit. The presence of some mud or slurry, increasing its specific gravity and viscosity and thus the ability to loosen and convey heavier particles than clean water, may be desired in a flow of water used and reused to clean storm drains, pipes, and sewers according to the disclosures herein, to increase efficiency and reduce waste of available production time. 
     In accordance with the disclosure herein a large-volume flow of water at a moderate pressure is directed through hose to a set of nozzles in a nozzle assembly to break up, dislodge and emulsify sediment within a pipe such as a storm drain conduit, and the water can then carry the sediment downstream within the storm drain conduit. The sediment-laden water can then be pumped from the downstream end of a length of storm drain conduit or other large pipe being cleaned. 
     Sediment-laden water may be removed from the storm drain conduit and screened to remove large items, gravel, and coarse sand. Sand may thereafter be removed centrifugally and the water, which may continue to contain substantial quantities of suspended solids such as clay or mud, and thus may have an increased viscosity and an increased specific gravity, may then again be pumped to the nozzle arrangement in the storm drain conduit or other pipe being cleaned, where the increased viscosity and specific gravity can facilitate moving material downstream through the storm drain conduit or other pipe being cleaned. 
     In one embodiment of the method disclosed in this application, a set of nozzles, fed with water by a pressurized hose, may be introduced at a downstream end of a length of storm drain conduit or other pipe needing to be cleaned. The force of a significant volume of water ejected from the nozzles at a significant exit velocity, in a generally downstream direction, may be used to propel the set of nozzles upstream through the storm drain conduit, and at the same time to pull along a water supply hose feeding the nozzles. 
     The foregoing and other objectives and features of the invention will be more readily understood upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: 
         FIG. 1  is a partially schematic diagram of exemplary apparatus for use in cleaning accumulated sediments from a storm drain conduit. 
         FIG. 2  is a top plan view of a portion of the apparatus shown in  FIG. 1 . 
         FIG. 3  is a partially schematic diagram of storm drain conduit cleaning apparatus that is a variation of the apparatus shown in  FIG. 1 . 
         FIG. 4  is a somewhat schematic illustration of an integrated, easily transported arrangement including the storm drain conduit cleaning apparatus shown in  FIGS. 1 and 2 . 
         FIG. 5  is a partially cutaway isometric drawing of a nozzle system that may be used as a part of the apparatus disclosed herein for cleaning accumulated sediments from a storm drain conduit. 
         FIG. 6  is a schematic illustration of the apparatus for use in cleaning accumulated sediments from a storm drain conduit and preparing the dirty water for further use. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to the drawings that form a part of the disclosure herein, a storm drain conduit cleaning system  20  shown in  FIG. 1  utilizes a high-volume flow of water from a nozzle assembly  22  fed by a nozzle assembly feed hose  24 . The nozzle assembly  22  may be introduced, through an access point such as a manhole  23 , into a storm drain conduit  26  or similar conduit at a downstream end  28  of a length of the storm drain conduit  26  to be cleaned. A high-volume flow of water is discharged from the nozzle assembly  22  to break up and loosen accumulated sediment  27  and flush loosened sediment downstream through the storm drain conduit  26 , in the direction of the arrow  29 , toward the downstream end  28  of the length of storm drain conduit being cleaned. 
     A barrier  30  such as an inflatable body may be installed below the downstream end  28  of the segment to be cleaned, to block the downstream end of the segment and prevent water and entrained matter from proceeding further downstream. Dirty water, including the loosened sediment flushed downstream through the segment of the storm drain conduit  26  being cleaned, is collected at the outlet or downstream end  28  of the segment being cleaned, and is removed and introduced into a water cleaning system  31  shown in  FIGS. 1 and 2 . Depending to some extent upon the volume of water and the amount of sediment involved, the dirty water and suspended matter may be lifted from a point of collection at the downstream end  28  by use of a high-volume pump or sump pump  32  and then delivered to the cleaning system  31  through a suitable discharge conduit  34 . 
     Alternatively, as shown in  FIG. 3 , the dirty water and included sediment may be removed from the point of collection at the downstream end  28  through one or more suction hoses  36  and conducted to a vacuum tank  38  that may be carried on a truck  40 . Those liquids and entrained solids can then be pumped through conduit  76  to deliver them to cleaning system  31 . 
     In either case, the sediment that has been transported downstream through the length of storm drain conduit  26  being cleaned is removed at the downstream end  28 , together with the water that had been delivered into the storm drain conduit  26  by the nozzle assembly  22 . In the water cleaning system  31  much of the sediment is separated out, and the water is cleaned sufficiently to permit it to be pumped again to the nozzle assembly  22 , where it is used again to break up, loosen, and flush additional sediment to the downstream end  28  of the length of storm drain conduit  26  being cleaned. 
     Referring now also to  FIG. 4 , the storm drain conduit cleaning system  20  may include a suitable supporting framework to make the system mobile, i.e., a skid, flatbed, roll-off box, a truck, or a trailer  50  on which a water cleaning tank system  52  and other components of the water cleaning system  31  shown in  FIGS. 1 and 2  are located. The water cleaning system  31  includes a power supply  54  such as an internal combustion engine, arranged to drive a hydraulic fluid pump or electric generator  56  of suitable capacity to drive pumps. A suitable control system  58  mounted on the truck or trailer may be arranged to control the power supply  54  and provide electrical or hydraulic power through conduits  59  to motors arranged to drive various water pumps included in the storm drain conduit cleaning system  20 , as will be described presently. 
     The water cleaning system  31  may include a nozzle assembly supply pump  60  driven by a motor  61  and a water cleaning system pump  62  driven by a motor  63 , all mounted on the truck or trailer  50 . Both water pumps  60  and  62  may be high-volume centrifugal pumps driven by the motors  61  and  63 , regulated by the control system  58  also mounted on the truck or trailer  50 . The nozzle assembly supply pump  60  should have a capacity of at least 350 gallons per minute at an output pressure of at least 100 psi. A higher capacity output would be desired in some large diameter storm sewers, and may be accomplished economically with the addition of pumps added either in parallel, in series, or both. 
     The water cleaning system pump  62  does not need to have a volumetric capacity equal to that of the nozzle system supply pump  60 , nor does it need as great a pressure capacity. For the sake of simplicity and economy of repair and maintenance, however, it may be economically efficient for both the nozzle system supply pump  60  and the water cleaning system pump  62  to be of the same type and capacity. 
     Referring again to  FIGS. 1 and 2 , the water cleaning system  31  includes the water cleaning tank system, which may include a main reservoir or outer tank  66  and also includes a vortex sediment separator tank  68  that may be located centrally within the outer tank  66 . At least the lower part  120  of the vortex separator tank  68  may be generally conical and may be spaced a small distance above the bottom  134  of the outer tank  66 . 
     Supported above the main tank  66  of the water cleaning system is a sloped screen  70  driven to vibrate, as by a vibrator motor  72 . The screen  70  may have a size 10 mesh or 20 mesh, for example. Dirty water and entrained materials pumped from the collection area at the downstream end  28  of the length of storm drain conduit  26  being cleaned are conducted through the conduit  34  from the sump pump  32  and discharged onto the screen  70 , as shown in  FIGS. 1 and 2 . Alternatively, as shown in  FIG. 3 , uncleaned water and included materials may be delivered from the vacuum tank  38  to the screen  70  by a pump  74  outside the vacuum tank  38 , or by a pump  75  within the tank  38 , or the vacuum tank may be pressurized later to force the dirty water through a suitable conduit  76 . 
     Rocks, gravel, and grit larger than coarse sand are removed from the flow of dirty water by the screen  70  and roll, bounce, or slide down the screen  70  to a suitable collection bin  78  to be carried away. The screened water and suspended material small enough to pass through the screen fall into the top of the vortex separator tank  68 , passing over intersecting horizontal pipes  136 , into a circular trough  80 . Pans  77  may be provided beneath the portions of the screen  70  to direct screened water into the trough  80  and prevent it from dropping directly into the portion of the main tank  66  outside the vortex sediment separator tank  68 . 
     The circular trough  80  may resemble a pair of funnels arranged concentrically, but oppositely, with a wide-mouth outer funnel  82  being an outer wall of the circular trough  80 , and with an inverted funnel  83  centered within the outer funnel  82 , with its smaller end abutting against and interconnected with the intersection of the horizontal pipes  136 . The outer rim of the inverted funnel  83  is located at the same height as the mouth, or inner rim, of the outer funnel  82  and is of a slightly smaller diameter than the mouth of the outer funnel  82 , so that the lower margins of the funnels  82  and  83  define a circular slot  118 . Sand and other fine particulate material suspended in the water that has passed through the screen  70  can descend through the trough  80  and exit through the slot  118  near the inner surface of the vortex separator tank  68 . The particulate material can then settle toward the bottom of the conical lower portion  120  of the vortex separator tank  68 , where a discharge port  122  is provided. 
     A discharge conduit  124  leads water and entrained sediment from the discharge port  122  at the bottom of the conical lower portion  120  to the cleaning system pump  62 . The cleaning system pump  62  delivers the water through a conduit  126  to a sand removal apparatus  128  that removes a large majority of entrained sand from the water and returns the substantially sand-free water into a space  130  between the outer funnel-shaped wall  82  of the circular trough  80  and the wall  84  of the vortex separator tank  68 , preferably through tangentially oriented ports  132  that encourage spiral flow downward toward the bottom of the vortex sediment separator tank  68 . 
     The sand removal apparatus  128  may, for example, include a group of devices  86  called desander cones that utilize centrifugal action to remove the heavier-than-water sand particles from the water received from the cleaning system pump  62 . Such desander cones  86  are available, for example, from Tibban Mfg. Inc., as its Tetragrene model MP 380112-1-T. Each such desander cone  86  may have a capacity of about 165 gallons per minute of dirty water at a nominal supply pressure of 30-50 pounds per square inch. As shown in  FIGS. 1-3 , then, several such desander cones  86  may be used in parallel, all connected to an inlet header  88  and each connected to a respective outlet conduit  94 . Alternatively, all the desander cones  86  may discharge water into an outlet header  90 , shown in broken line in  FIGS. 1 and 3 , leading to one or more outlet conduits  94 . While four desander cones  86  are shown in  FIG. 2 , it may be desirable to utilize five or more. Sand removed from the screened water by the desander cones  86  is deposited and accumulated on a sloped screen  92  that may have a size 100 mesh and may be conveniently located above the screen  70 . The sand can slide down the screen  92  into the collection box  78 , to be collected with the gravel and other materials separated from the water by the screen  70 , for eventual disposal or use for fill. Most residual water discharged with sand from the desander cones  86  passes through both screen  92  and screen  70 , returning to the vortex sediment separator tank  68 . 
     Each outlet conduit  94  may have an outlet end portion  96  connected to a respective one of the tangential ports  132  spaced apart around the circumference of the vortex separator tank  68 . The ports  132  are preferably oriented to direct the water discharged from it in a spiral flow pattern in the space  130  that may assist in causing sand and other suspended material exiting the circular trough  80  through the slot  118  to settle near the bottom of the conical lower portion  120  of the vortex separator tank  68 . 
     As a result of the circulation described, the cleanest water in the vortex separator tank  68  is likely to be found near the center of the upper surface of the water surrounded by the inverted funnel  83 , and thus surrounded by the circular trough  80 , where the horizontal pipes  136  extend across the center of the top of the vortex separator tank  68 . These pipes have large openings  138  in the bottom of each near the center of the vortex separator tank  68 , and relatively clean water can enter the pipes  136  through the openings  138  and be discharged into the surrounding outer tank  66  through the open outer end  139  of each pipe  136 . 
     After removal of sand from the screened water the suspended material remaining in the water flowing through the pipes  136  into the outer tank  66  is primarily mud or clay and is of very small particle size. Such particle size may, however, be mostly too great for such water to be pumped through the high-pressure pumps utilized currently in commercially available storm drain conduit cleaning systems without causing unacceptable wear. Such water including such suspended material, however, can reliably be pumped by the nozzle system supply pump  60  and cleaning system pump  62  at the significantly lower pressures required by the sewer cleaning system  20  described above, yet at a pressure and volume of flow adequate for dislodging and transporting accumulated material in storm drain  27  to the downstream end  28 . 
     The cleaned water in the main, or outer, water tank  66  of the water cleaning tank system  52  is available to be removed through a discharge port to the nozzle assembly supply pump  60 . The nozzle assembly supply pump  60  provides the cleaned water to the nozzle assembly feed hose  24 , part of which may preferably be wound on a suitable hose reel  104  that can support the hose while it is pressurized. The nozzle assembly feed hose  24  can thus be extended as required while delivering water to the nozzle assembly  22 . While a single nozzle assembly feed hose  24  is preferable, where the flow of water required is greater than 400 gallons per minute it may be desirable to use a pair of parallel nozzle assembly feed hoses  24  in order to facilitate handling the hoses and to facilitate bending the hoses as may be required for them to pass through access openings such as storm sewer catch basins and manholes  23  and/or into an available downstream end  28  of a length of a storm drain conduit  26  or other conduit that is to be cleaned. 
     It is critical that the nozzle assembly feed hose  24  be of ample strength and size to carry the desired amount of water. It is also desirable that the nozzle assembly feed hose  24  be both flexible and as close to neutral or even positive buoyancy as possible, to minimize friction, as will be explained below. One such hose available would be Kuri Teck K-Tough hose sold by Kuriyama of America, Inc. which has a specific gravity of about 1.42. 
     As may be seen best in  FIG. 5 , the nozzle assembly  22  may include a receiver-manifold  105  including a rear end to which the nozzle assembly feed hose  24  may be suitably coupled by a conventional coupler  107 . A plurality of nozzles  106 , for example six, are mounted on the receiver-manifold  105  and connected so as to be supplied with water from the nozzle assembly feed hose  24  with minimal loss of pressure. The nozzles  106  are directed rearwardly and back along the nozzle assembly feed hose  24  and diverge from each other at a respective acute angle  109 , of 0-40 degrees, for example, from a central axis  111  of the nozzle assembly  22 . The nozzle assembly  22  can thus provide a strong, high-volume, stream of water from each nozzle  106 , directed so as to urge the nozzle assembly  22  along the conduit being cleaned and also direct the stream of water from each nozzle  106  toward the interior surface of the storm drain conduit  26 , to loosen sediment from the storm drain conduit  26  and wash or flush it downstream within the conduit  26 . 
     The nozzles  106  can cumulatively provide enough water flow volume to carry the loosened sediment downstream within the storm drain conduit  26  toward the downstream end  28  of a length of the storm drain conduit  26  that is being cleaned. For example, six nozzles  106 , each having a circular outlet orifice with a diameter of ½ inch can deliver a total of at least 350 gallons per minute, with a nozzle exit velocity in the range of 90-125 feet per second, thus at least 90 feet per second and preferably at least 115 feet per second, when the pressure at the outlets of the nozzles is at least about 100 psi. This volume is sufficient to carry sediment downstream within a storm drain conduit having a diameter of 24 inches, even at a very shallow grade. At the same time, with the six nozzles  106  directed as described, the combined thrust from the nozzles  106  is sufficient to propel the nozzle assembly  22 , together with the nozzle assembly feed hose  24 , upstream a considerable distance along a length of storm drain conduit  26  that is being cleaned. The previously mentioned desired buoyancy of the nozzle assembly feed hose  24  is intended to facilitate movement of the nozzles by reducing friction between the nozzle assembly feed hose  24  and the bottom of the storm drain conduit  26 . 
     An additional, forwardly directed nozzle  108  and an associated control valve  110  mounted on the receiver-manifold  105  make it possible to provide a forwardly directed stream of water from the nozzle assembly  22  to loosen sediment in a storm drain conduit  26  that is so completely obstructed by accumulated sediment that there is insufficient room for the nozzle assembly  22  to proceed upstream before some of the sediment is loosened and moved. Where the segment of storm drain conduit  26  to be cleaned already defines a sufficiently open path the control valve  110  can be closed so all of the water passing through the nozzle assembly  22  can assist in moving the nozzle assembly  22  upstream. 
     A protective housing  112  defining ample openings corresponding with the locations of the nozzles  106  and  108  may be provided to facilitate movement of the nozzle assembly  22  within a storm drain conduit  26  and avoid having the nozzle assembly  22  be snagged on a sewer wall surface irregularity or on a rock or other piece of sediment. The housing  112  may, for example, include an outer shell of a strong, tough, low-friction plastic, such as HDPE, having a modified cylindrical, or bullet, shape, with tapered ends  114  and  116 , and openings at the ends for the nozzle assembly feed hose  24  and the nozzle  108 . 
     The nozzle assembly supply pump  60  is capable of delivering to the nozzle assembly  22  enhanced but still dirty water, that is, water which has been screened, and from which sand has been removed, but which includes suspended clay and mud. Such dirty water has a greater viscosity and specific gravity than clean water and thus is capable of providing greater support for the conveyance of sand and gravel loosened by the flow of such water from the nozzles. Additionally, the greater volume of such dirty water provided within a storm drain conduit being cleaned by the storm drain conduit cleaning system  20  disclosed herein (by comparison with the well-known sewer cleaning systems using high-pressure low-volume sewer jets) effectively carries loosened sediment downstream through the section of storm drain conduit being cleaned. Loosened sediment thus does not need to be pulled downstream by retracting the nozzle assembly periodically, as is necessary in previously known step cleaning methods for cleaning storm drain conduits. 
     As a result of the nozzle assembly  22  being able to propel itself and bring the nozzle assembly feed hose  24  along, and since operation can be continuous and is independent of ability of trucks to provide clean water, lengthy segments of a pipe  26 , at least as long as 200 feet, can be cleaned before the nozzle assembly  22  and nozzle assembly feed hose  24  must be moved to an access opening at the downstream end  28  of another segment of the pipe or storm drain conduit  26  being cleaned. This can greatly reduce the time needed for cleaning a storm drain conduit  26 , by comparison with the conventional methods. 
     Water can be reused after treatment as shown schematically in  FIG. 6 . It will be understood that reused water from which gravel and sand have been removed will accumulate quantities of clay and mud and will thus become more and more dense and viscous with continued recirculation through the storm drain conduit cleaning system  20 . For example, it is desired to eventually have a slurry of water and entrained mud and clay with a specific gravity of at least about 1.05 and at least viscosity such that the dirty water does not pass through a static #20 mesh screen (or #10 mesh screen) but at least partially passes through a vibrating #20 mesh screen (or #10 vibrating mesh screen). In some examples, the #20 mesh screen (static and/or vibrating) may have openings that are 850 microns or 0.0331 inches in diameter. The desired viscosity of the dirty water may, for example, be about 30 to about 600 centipoise. In some examples, the desired viscosity may be such that at least some of the dirty water passes through a static #20 or #10 mesh screen when the frame that houses it is manually struck with a rubber mallet by an adult person of average strength (such as by applying about 600 to about 1200 pounds force on the static #20 or #10 mesh screen and/or on the pipe adjacent to the static #20 or #10 mesh screen), which momentarily disrupts the surface tension of the dirty water. The above specific gravity and viscosity values are particularly significant because dirty water with such values allow for more effective removal of accumulated sediment from the pipe being cleaned as compared to other pipe cleaning apparatus and methods. 
     Thickeners may alternatively, or additionally, be added to the water in main tank  66  (and/or other water containers) to provide water with the above specific gravity and/or viscosity values. This may provide the enhanced water to clean the pipe instead of, or in addition to, recycling some of the accumulated suspendable solids sediment from the pipe being cleaned. Examples of suitable thickeners include clays, gums, and/or polymers. 
     Once viscosity is so high that it degrades the ability of the dirty water to pass through the vibrating primary screen  70  (such as a vibrating #20 or #10 mesh screen), and thus periodically during the course of operation of the storm drain conduit cleaning system  20 , a portion of the suspended solids and mud can be removed from the dirty water, as by mixing in polymers  151  that use ionic charges to coagulate the particles suspended in the dirty water and separate them from the relatively clear water. This may be accomplished by removing a portion of the dirty water from the reservoir tank  66  via a conduit  149  to a third smaller pump  150  and pumping it into a static mixer  152  where polymers  151  of either positive or negative charge, or both, are added to mix with and separate some of the suspended solids from the clear water. Then both the water and coagulated solids are sent to either a special screen  154  or to the primary screen  70 . The clear water passes through the screen and the coagulated lumps  155  of solids bounce down the screen  70  to the solids collection box  78  to be mixed with the other solids. The relatively clear water is then returned into the circuit as it mixes with incoming dirty water and passes into the vortex separator tank  68 , thus lowering the viscosity of the dirty cleaning water. 
     For example, coagulating polymers can be mixed with water containing a great deal of suspended solids, using a static mixer  140 , basically a long pipe  152 , into which the polymers can be injected, as shown in  FIG. 1 . Dirty water can be supplied from the tank  66  through a conduit  149 , using a pump  150  through which the dirty water is made to flow into the static mixer  140 . The polymers may be of positive and negatively charged types that cause suspended small particles to coalesce. The pipe  152  is preferably equipped with internal baffles which cause the flow of water through the pipe  152  to be turbulent enough to mix the polymers with the dirty water efficiently as both pass through, so that the polymers can cause the matter suspended within the water to coagulate and coalesce, enabling the coagulated solids to be removed from the water more easily as by the polymer-treated water proceeds from the static mixer  140  through a conduit  153  to the screen  70 , or a separate additional screen  154  above it, existing specifically for keeping coagulated solids  155  bouncing down its surface while allowing water to pass through all three screens back into the vortex separator. 
     Removal of suspended solid material, particularly once it has been coagulated by the use of polymers, can also be accomplished using centrifuges  142  that are well-known for use in water purification plants for removing suspended material from water. 
     Alternatively, so that the water can be reused in the storm drain conduit cleaning system  20  described above, the coagulated entrained solid material can be removed from water, after the use of polymers, simply by allowing the water to drain from the suspended solids in a dewatering tank  144 . Such a dewatering tank  144  may, for example, be a large cylindrical tank lined with a porous layer through which water can pass and then flow to an outlet at an end of the cylindrical tank to be collected for reuse. The drained coagulated solid material remaining within the dewatering tank  144  can then be removed, as through a door at an end of the tank, to be disposed of appropriately. 
     Some water can be reclaimed from separated but wet sediment by treating the wet sediment in a belt filter press  146 . The wet material is spread upon a wide, porous, moving belt and then passed beneath a second belt. The two belts are squeezed together, and remaining water is pressed from the sediment and collected beneath the belts so that the water can be reused in the storm drain conduit cleaning system  20 . The remaining solid materials are then scraped from the belts for collection and disposal. 
     The present disclosure also includes methods of cleaning large pipe that include any suitable combination of the above steps. For example, the methods may include enhancing water or providing enhanced water for use in cleaning the large pipe (such as providing the enhanced water adjacent to the large pipe for use in cleaning the large pipe). The enhanced water has a specific gravity of at least 1.05 and a viscosity such that the enhanced water does not pass through a static #20 mesh screen (or #10 mesh screen) but at least partially passes through a vibrating #20 mesh screen (or #20 mesh screen). The methods also may include discharging a quantity of the enhanced water through a nozzle assembly and directed toward a quantity of accumulated sediment in a segment of pipe to be cleaned such that the quantity of accumulated sediment is loosened and suspended solids are generated from at least a portion of the loosened sediment. 
     In some examples, enhancing water or providing enhanced water may include blocking a downstream end of the segment of pipe to be cleaned, removing water and loosened sediment from the pipe being cleaned, at the downstream end of the segment of pipe being cleaned, and storing at least a portion of the removed water and suspended solids from the loosened sediment with the enhanced water in a container, which may increase the specific gravity of enhanced water in the container to at least 1.05 and increasing the viscosity of the water in the container such that the quantity of water does not pass through a static #20 mesh (or #10 mesh) screen but at least partially passes through a vibrating #20 mesh (or #10 mesh) screen. In some examples, the viscosity of the enhanced water may be between about 30 centipoise and about 600 centipoise. 
     In some examples, enhancing water or providing enhance water may include providing water and adding one or more thickeners to that water such that the resulting enhanced water has a specific gravity of at least 1.05 and a viscosity such that enhanced water does not pass through a static #20 mesh screen but at least partially passes through a vibrating #20 mesh screen. In some examples, the viscosity of the enhanced water may be between about 30 centipoise and about 600 centipoise. 
     It will be appreciated that the present invention is not restricted to the particular embodiment that has been described, and that variations may be made therein without departing from the scope of the invention as defined in the appended claims, as interpreted in accordance with principles of prevailing law, including the doctrine of equivalents or any other principle that enlarges the enforceable scope of a claim beyond its literal scope. Unless the context indicates otherwise, a reference in a claim to the number of instances of an element, be it a reference to one instance or more than one instance, requires at least the stated number of instances of the element but is not intended to exclude from the scope of the claim a structure or method having more instances of that element than stated. The word “comprise” or a derivative thereof, when used in a claim, is used in a nonexclusive sense that is not intended to exclude the presence of other elements or steps in a claimed structure or method.