Abstract:
A sewer comprising a barrier disposed to prevent or reduce the flow of air in the headspace, oppose the escape of gases and/or liquid droplets from within the liquid into the headspace of the sewer, and also oppose the drawing in and entrainment of headspace air and gases into the liquid contained within the sewer. The sewer comprises a conduit and a barrier fixed within the interior of the sewer, which extends longitudinally along the sewer conduit so as to separate the sewer conduit into a liquid conductive channel disposed below the barrier and a gas conductive channel disposed above the barrier. The barrier may move up and down within the sewer responsively with varying water flow within the sewer. The barrier may comprise an elastomeric sheet. The barrier may be tubular at areas of steep plunge.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to sewers, and more particularly to improvements thereto for reducing interaction between liquid flow in a sewer and air occupying the space above the liquid level, referred to herein as the “headspace”, by imposing a physical barrier between liquid and air. 
       BACKGROUND OF THE INVENTION 
       [0002]    Sanitary and storm sewers conduct fluent wastes away from infrastructure such as buildings and roads. Most sewers rely upon gravity to induce flow of fluent wastes. Both gravity operated and pressurized sewers are open to ambient air at one point or another. Sewers are susceptible to formation of objectionable gases and other substances which may be formed in fluent wastes and released to ambient air. Hydrogen sulfide is one such gas which arises from bacterial decomposition of organic materials such as sewage solids which are mixed with water to form a fluent mixture. Also, other substances and hydrocarbon compounds such as methane can form with other chemical products of sewage systems. Methane itself is a colorless odorless gas which is objectionable because it is flammable and because in sufficient quantity, it can displace oxygen. Sulfur and other compounds typically generate objectionable odors and may also be reactive and even toxic. Air within the headspace in sewers is dragged along by the flowing sewage resulting in airflow within the sewer headspace. Flowing air in the sewer headspace may result in sewer pressurization, particularly at locations where there is a change in sewer cross section, junctions, changes in longitudinal slope, inverted siphons, and other obstacles to sewer air flow. This in turn causes the sewer air and its objectionable gases to be forced out of the sewer into the surrounding atmosphere and neighborhoods. 
         [0003]    In addition, flowing sewer air becomes entrained with liquid sewage, particularly at locations where liquid sewage falls steeply or vertically into downstream sewers or standing liquid sewage. Downstream of such locations, increased turbulence from energy dissipation results in increased sewer pressurization accompanied with sewage aerosol droplets and release of entrained air. This, in turn, causes increased potential for the release of sewer air and its objectionable gases to the surrounding atmosphere and neighborhoods. 
         [0004]    Sewers typically extend for long distances and in so doing pass by many occupied buildings. Release of objectionable gaseous or gas borne contaminants into the ambient air near these buildings is objectionable, and occurs if no steps are taken to prevent this from happening. A mixture of sewer air, hydrogen sulfide, methane, and diverse chemical contaminants escaping from a sewer system and entering into areas of human activity is objectionable and intolerable. 
         [0005]    Sewer air treatment facilities have been developed to remove and treat the liquid borne gases from the sewer air. While such facilities have been proven relatively effective at removing the objectionable gases from the sewer air, they are treating the symptom and not dealing with the underlying causes, which is the flow of air in the headspace and its contamination with sewage born gases. Another approach has been to use chemicals for neutralizing sewage components that generate the objectionable gases. However, these require extensive and continuous use of potentially harmful chemical that must be used in proportion to need, can be depleted by reacting with sewage before the entire length of the sewer has been remediate by chemical neutralization, and may also be depleted by evaporation or entrainment with gases escaping from liquid sewage. 
         [0006]    There remains a need for eliminating or reducing the flow of air in the headspace of sewers, its contamination with sewage borne gases, and entrainment and re-release of sewer air into and out of liquid sewage within sewer conduits. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides an answer to the above stated need by interposing a physical barrier between liquid sewage and the headspace thereabove. The barrier may be flexible and movable in a direction perpendicular to liquid flow so as to accommodate fluctuations in volume of flow while still providing the barrier function. 
         [0008]    The barrier may for example take the form of a flexible water impermeable, gas impermeable blanket which spans the interior diameter of an associated sewer conduit and is supported at least at one end within the sewer conduit so as to rest on liquid sewage occupying the sewer conduit. The end opposite that which is supported may be unattached to the sewer conduit or alternatively may be supported within the sewer conduit. The blanket may isolate the liquid sewage from air occupying the headspace above the liquid sewage. This will both oppose the air within the headspace from being dragged along into the liquid sewage that establishes a current of air within the headspace, and will also prevent the sewer air from being drawn in and entrained in the sewage. It will further entrap and oppose escape of gases and sewage droplets which may come out of suspension within the liquid sewage or be sprayed out at locations of turbulence. All of these occurrences will assist in preventing fouling of ambient air outside yet near the sewer. 
         [0009]    The barrier may be arranged to rise and fall within a sewer conduit for example, to accommodate fluctuations in depth of liquid sewage. 
         [0010]    The barrier may be formed in serial sections to collectively cover long expanses of sewer. Each of these serial sections may be independently supported to the interior wall of the sewer. 
         [0011]    The barrier may be of floatable material itself or portions of the barrier may incorporate floats to assure that the barrier remain above liquid contained within the sewer. 
         [0012]    The barrier may be formed with some portions along which the barrier forms a sheet and others wherein the barrier forms a tube. The latter situation may come into play at locations where the sewer undergoes a vertical or steep non-vertical plunge or the like. In such situations, the barrier may be tubular, so as to conduct liquid sewage past the plunge. In such situations, sheet construction of the barrier could potentially interfere with intended operation. 
         [0013]    It is an object of the invention to provide a barrier at the liquid-to-gas interface within a sewer for opposing drag-induced air flow and migration of gases along the headspace of the sewer and also opposing drawing of headspace gases into entrainment within the liquid as well as preventing the release of entrained gases within the sewage. 
         [0014]    It is an object of the invention to provide improved elements and arrangements thereof by apparatus for the purposes described which is relatively inexpensive, dependable, and fully effective in accomplishing its intended purposes. 
         [0015]    These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Various objects, features, and attendant advantages of the present invention will become more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein: 
           [0017]      FIG. 1  is a cross sectional view of a sewer construction according to at least one aspect of the invention. 
           [0018]      FIG. 2  is a cross sectional view taken along line  2 - 2  in  FIG. 1 . 
           [0019]      FIG. 3  is a cross sectional view similar to  FIG. 2 , but showing a slightly decreased volume flow of liquid contained within the sewer construction from that of  FIG. 1 . 
           [0020]      FIG. 4  is a cross sectional view similar to  FIG. 2 , but showing a slightly increased volume flow of liquid contained within the sewer construction from that of  FIG. 1 . 
           [0021]      FIG. 5  is a cross sectional view similar to  FIG. 2 , but showing the sewer construction entirely filled with liquid. 
           [0022]      FIG. 6  is a cross sectional view similar to  FIG. 1 , but showing a greater length of the subject sewer construction. 
           [0023]      FIG. 7  is a cross sectional view of a sewer construction according to the tubular aspect of the invention, wherein there is an abrupt change in elevation of the system. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    Referring first to  FIG. 1 , there is shown a sewer construction according to at least one aspect of the invention wherein the sewer construction is provided with a barrier preventing the imposition of drag forces at the surface of flowing liquid  102  in sewer  100 , upon the air within the sewer headspace  104 , thereby preventing the flow of air in the headspace. The barriers is also opposing the escape of gases and droplets (not visible) generated within liquids  102  contained within the sewer  100  into the headspace  104  of the sewer  100  and also opposing the drawing in and entrainment of headspace air and gases into the liquid  102  contained within the sewer  100 . The sewer  100  will be understood to be a system comprising of at least one sewer conduit  106  and ancillary components such as a manhole, a vent, or another sewer  108  which opens to the exterior of the sewer  100  to permit air and or liquids to enter the sewer  100 . 
         [0025]    The sewer conduit  106  is typically made from concrete, cast iron, steel, brick, and other durable substances, and comprises a circumferential wall  110  for confining liquids such as the liquid  102  within the sewer  100  and a longitudinal axis  112 . The liquid  102  may be any liquid intended to be collected for conveyance and/or disposal, such as water from rainfall, domestic wastewater containing solid waste, or any liquid which is collected in a system which is open to the environment as opposed to a sealed system such as a pressurized domestic water supply. The sewer conduit  106  may have an entry opening  114  such as that shown formed in the manhole or vent  108 . The entry opening opens the interior of the circumferential wall  110  to the environment, for allowing access to the interior of the sewer for maintenance, enabling inflow or outflow of air, or enabling collection of liquids to be discharged. The sewer  100  terminates in a discharge opening (not shown) for discharging collected liquids contained within the sewer conduit  106  to the exterior thereof, such as the head works of a sewage treatment plant. 
         [0026]    The sewer conduit  106  is provided with a suitable support mechanism for fixing or holding the barrier in operable position within the interior of the sewer conduit  106 . The barrier may comprise an elastomeric sheet  116  for example. It is preferred that the barrier be gas impermeable, water impermeable, and flexible. Many available elastomeric substances such as natural and synthetic rubbers and plastics, among others, satisfy these demands and are suitable for forming the barrier. The support mechanism may comprise a hoop  118  provided with an pivotally supported arm  124  pivotally anchored to the hoop  118  at a swivel joint  122 . The arm  124  may comprise a clamp  120  for grasping the elastomeric sheet  116 . Of course, the support structure may take any convenient form such that it solidly engages the circumferential wall  110  and reliably holds the barrier. Similarly, the arm  124  may be replaced by different arrangements, including but not limited to the direct fastening of the barrier blanket itself to the wall of the sewer. 
         [0027]    The barrier is disposed to extend longitudinally along the sewer conduit  106 , generally parallel to the longitudinal axis  112 . Most sewer systems are gravity operated, and are built with slight inclination from a purely horizontal direction to promote flow in a desired direction. Therefore, the support mechanism is located upstream from the barrier where the barrier may be supported at only one end. As will be described hereinafter, it is possible to support the barrier at more than just one point. 
         [0028]    The barrier separates the sewer conduit into a liquid conductive channel disposed below the barrier for conducting the liquid  102 , and a gas conductive channel disposed above the barrier. It will be understood that the air conductive channel, which comprises the headspace  104  and the liquid conductive channel, which is that space occupied by the liquid  102 , are to be regarded as semantic distinctions as these channels are not separate physical elements unto themselves. Rather, the channels refer to the spaces occupied respectively by air  104  and by the liquid  102 . These spaces or volumes vary with the flow of the liquid  102 , as flow refers to volume of the liquid  102  occupying the sewer  100 . To facilitate this variation while simultaneously performing its function of segregating the liquid  102  from gases of the headspace  104 , the barrier is disposed to move radially with respect to the longitudinal axis  112 . That is, the barrier may be located at any of many points ranging from proximate the bottom of the sewer conduit  106  to proximate the top thereof, as seen in  FIG. 1 . 
         [0029]    It should be noted at this point that orientational terms such as top and bottom refer to the subject drawing as viewed by an observer. The drawing figures depict their subject matter in orientations of normal use, which could obviously change with different sewer systems. Therefore, orientational terms must be understood to provide semantic basis for purposes of description, and do not limit the invention or its component parts in any particular way. 
         [0030]    The motion of the barrier is enabled by a pivotal connection  120  of the arm  124 . The pivotal connection  120  enables the arm  124  to swing in an arcuate motion through an arc  126 . Of course, the arm  124  could be replaced by a linearly moving device for example or other arrangement provided it enables the barrier to track height of the liquid  102  within the sewer conduit  106 , including the barrier blanket itself. Any motion which effectively enables the barrier to track height of the liquid  102  will be referred to as radial motion as that motion extends in directions which radiate from the longitudinal axis  112 . 
         [0031]    The barrier may also have the characteristic that it responds spontaneously to variations in the height or volume of the liquid  102 . Where the barrier is provided by the elastomeric sheet  116 , it will be seen that with the elastomeric sheet  116  secured to the sewer conduit  106  at a fixed point, the liquid  102  itself and gravity will combine to impose forces which raise and lower the elastomeric sheet  116  with rising and falling flow or volumes of the liquid  102 . This action is spontaneous in that no external controls or motive forces need be applied to cause the elastomeric sheet  116  to accommodate variation in flow or volume. 
         [0032]      FIG. 2  shows the elastomeric sheet  116  spanning the interior diameter of the sewer conduit  106 , as it would with the liquid  102  occupying about half of the total cross sectional area of the sewer conduit  106 . 
         [0033]    Variations of height of the liquid  102  within the sewer conduit  106  may be accommodated in part by the ability of the elastomeric sheet  116  to have its edges  128 ,  130  turn upwardly ( FIG. 3 ) or downwardly ( FIG. 4 ) as the volume of the liquid  102  varies.  FIG. 5  shows how the elastomeric sheet  116  may deflect should the sewer conduit  106  fully fill with the liquid  102 . 
         [0034]      FIG. 6  shows a serial arrangement of barrier elements within a sewer construction  200 . It will be appreciated that as the elastomeric sheet  116  becomes longer and longer, installation, removal, and maintenance thereof become increasingly problematic. Extremely long runs of elastomeric sheet  116  may cause problems in orderly operation, such as twisting or other deformations which could prevent effective operation. To forestall such problems, the barrier may be formed in repeating sections. 
         [0035]    The sewer construction  200  may comprise a sewer conduit  206  in which a first elastomeric sheet  216 A and a second elastomeric sheet  216 B are provided serially so as to provide essentially continuous coverage of the liquid  202  contained within the sewer conduit  206  apart from minor gaps which may be present therebetween, particularly at junctions and locations of lateral inflow by other sewers. Each barrier element such as the elastomeric sheets  216 A,  216 B may be secured at the top of the sewer conduit  206  by respective support mechanis, which may comprise a hoop such as the hoop  118  of  FIG. 1 , or which may take other forms. Regardless of its form, the support structure may include a swivel  222 A or  222 B for pivotally anchoring a respective arm  224 A or  224 B comprising a respective clamp  220 A or  220 B adapted to engage and operably support its respective elastomeric sheet  216 A or  216 B, which may be continuous as shown or in distinct separate sections. The respective clamp  220 A or  220 B may simply be the direct fastening of the respective elastomeric sheet  216 A or  216 B to the sewer. The serial arrangement of barrier elements depicted in  FIG. 6  may be extended along the entirety of the sewer conduit  206  to implement a sewer construction  200  protected along its entire length against interaction of headspace gases and the liquid  202 . 
         [0036]    Flow of the liquid  202  is in a direction indicated by an arrow  228 . It will be seen that the swivels  222 A,  222 B are located upstream with respect to flow of the liquid  202  from their respective elastomeric sheets  216 A,  216 B. Spacing of the swivels  222 A,  222 B and the respective elastomeric sheets  216 A,  216 B from one another may be modified to suit conditions so as to minimize any portion of the liquid  202  which may be exposed to the headspace  204  between adjacent elastomeric sheets  216 A,  216 B. 
         [0037]      FIG. 7  shows further aspects of the invention. In  FIG. 7 , a sewer construction  300  includes an abrupt drop in elevation wherein a first generally horizontal section  306  of sewer conduit communicates with a vertical section  340  of sewer conduit, which in turn communicates with a second generally horizontal section  342  of sewer conduit. The sewer construction  300  copes with this abrupt drop by providing a barrier which negotiates the expanse of drop is in the form of a tube  344 . 
         [0038]    It will be seen that the distal end  346  of a barrier element in the form of a sheet  348 , the same configuration as the elastomeric sheet  116  of  FIG. 1 , may terminate at the same anchorage point  350  as that used to support a proximal end  352  of the tube  344 , or may terminate either downstream or upstream of point  350  as appropriate or deemed necessary by practical considerations. The tube  344  may be supported about the full circumference of its proximal end by a hoop structure  354  formed as part of that structure providing the anchorage point  350 . The tube  344  may distend and collapse depending upon the volume of liquid  302  flowing therethrough at any one time. The tube  344  may be superseded by another sheet barrier element (not shown) at the distal termination (not seen in  FIG. 7 ) of the tube  344 . The sewer construction  300  may be summarized as comprising a barrier which in turn comprises a sheet (such as the sheet  348 ) along some of the length of the associated sewer conduit assembly (comprising for example the sewer conduits  306 ,  340 , and  342 ) and a tube (such as the tube  344 ) along other portions of the length of the sewer conduit assembly. Although the sewer conduits  306 ,  340 ,  342  may be provided in sections for ease of fabrication and assembly, it will be recognized that after assembly, they collectively form a single sewer conduit. 
         [0039]    The invention may also be considered a method of operating a sewer which contains both liquid and also air within a headspace located above the liquid. The method may comprise a fundamental step of providing a barrier within the sewer along a portion or the majority of the length of the sewer, which barrier extends longitudinally along the sewer and is interposed between the liquid contained within the sewer and the air of the headspace. 
         [0040]    The method may also include the steps of anchoring a first end of the barrier at a fixed point within the sewer, anchoring a second end of the barrier at a fixed point within the sewer, enabling the barrier to move radially with respect to the longitudinal axis of the sewer so as to vary the respective volumes of the sewer above the barrier and below the barrier, and causing the barrier to move radially with respect to the longitudinal axis of the sewer spontaneously responsive to the volume of liquid contained within the liquid conductive channel. 
         [0041]    The steps of the method refer to apparatus shown and described with connection to  FIGS. 1-7 . The steps may be practiced in any feasible order and combination independently of other steps. 
         [0042]    Although presented in terms of a sewer the usual purpose of which is to dispose of storm water or sewage or both, the present invention is obviously adaptable to the purpose of other liquid systems which rely on gravity for at least a portion of their extent. For example, irrigation and liquid transfer systems, canals, tunnels and other liquid transport and conveyance systems, fire suppression systems, and still others will be understood to fall within the scope of the term “sewer” as employed herein. 
         [0043]    The present invention is susceptible to modifications and variations which may be introduced thereto without departing from the inventive concepts. For example, a barrier or a portion thereof may be rigid rather than flexible. Sewer conduits may be oblong, rectangular, or otherwise configured in cross section (such as the cross section shown in  FIG. 2 . 
         [0044]    While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is to be understood that the present invention is not to be limited to the disclosed arrangements, but is intended to cover various arrangements which are included within the spirit and scope of the broadest possible interpretation of the appended claims so as to encompass all modifications and equivalent arrangements which are possible.