Abstract:
An apparatus and method for improving the operation of sewer systems includes a first set of sewer lines connected to a source of other water and a second set of sewer lines of smaller diameter than the sewer lines of said first set connected to sources of sanitary effluent, the first and second sets of lines being separately connected to a sewerage treatment plant. The second set of sewer lines has at least a portion thereof that extends inside the first set of sewer lines and the first set of sewer lines can be an existing sanitary sewer system. The apparatus can include at least one sanitary effluent process device connected to the second set of sewer lines such as a pumping station, a grinder pump or a vacuum system to assist the flow of the sanitary effluent through the second set of sewer lines.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. provisional patent application serial No. 60/401,714 filed Aug. 7, 2002. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to an apparatus and a method for separating sanitary effluent from storm water and/or infiltrated water in a municipal sewer system. 
     Municipal sewer systems include a web of pipes that convey wastewater from homes, businesses and industries and storm water from drains to treatment plants. The smallest pipes, typically twelve inches in diameter or less, are know as “collectors” that are connected to service lines running to the sanitary plumbing of buildings. The collectors are connected to “mink lines”, typically larger than twelve inches in diameter, and carrying one to ten million gallons per day. The trunk lines connect to “interceptors” that carry the wastewater to a treatment plant. The interceptors are of large diameter, often as much as ten feet. 
     The wastewater plumbing system in a typical house, office building or manufacturing facility combines toilet effluent with other wastewater, such as from sink and bath drains, to be carried by a single service line to the collector line at the street. Hereinafter, such combined wastewater will be termed “sanitary effluent”. The municipal sewer systems combine and carry in the same pipes the sanitary effluent from buildings, storm water from outside drains and any ground water leaking into the system (infiltrated water). When the treatment plant and the associated web of pipes are built, the system is sized to process a predetermined number of gallons per unit of time, the maximum flow capacity, including a certain rainfall amount. As additional buildings are connected to the system, less of the predetermined flow capacity is available for storm water. Thus, the system becomes susceptible to rainfall amounts less than the planned certain rainfall amount causing numerous overflows into streams and lakes and backups into buildings through the service lines. Overflows also can occur in systems where the storm water is carried in a separate set of pipes. Such overflows and backups cause serious environmental and health problems. 
     Also, some sewer systems were designed with less capacity than is required to carry typical rainfall amounts thereby always overflowing during normal rainfalls. Typically, such systems were installed before there was much concern for the effect of the overflow on the environment. 
     However, no matter what the configuration of an existing sewer system, it either now has or will in the near future have flow capacity problems causing overflows, backups and leaks. Consequently, the local governments responsible for maintaining these sewer systems face enormous expenses to repair or replace the existing pipes and/or add capacity. 
     SUMMARY OF THE INVENTION 
     The present invention concerns an apparatus and method for improving the operation of sewer systems while reducing the cost of increasing system capacity. The apparatus according to the present invention includes a first set of sewer lines connected to at least one storm water drain, and/or source of infiltrated water, and/or source of sanitary effluent, and a second set of sewer lines of smaller diameter than said sewer lines of said first set connected to sources of sanitary effluent, the first and second sets of lines being separately connected to a sewerage treatment plant. The second set of sewer lines has at least a portion thereof that extends inside the first set of sewer lines and the first set of sewer lines can be an existing sanitary sewer system. The apparatus can include at least one sanitary effluent process device connected to the second set of sewer lines such as a pumping station, a grinder pump or a vacuum system to assist the flow of the sanitary effluent through the second set of sewer lines. The apparatus can provide the same flow volume in a smaller diameter pipe that is under pressure. 
     The method according to the present invention includes the steps of: a. providing a first set of sewer lines connected between at least one source of storm water, and/or source of infiltrated water, and/or source of sanitary effluent, and at least one sewerage treatment plant; b. providing a second set of sewer lines connected between a source of sanitary effluent and the sewerage treatment plant; and c. installing at least a portion of said second set of sewer lines in said first set of sewer lines. Step b. can include installing a sanitary effluent collector line spaced from a collector line of the first set of sewer lines and connecting a service line from the source of sanitary effluent to the sanitary effluent collector line. Step c. can include running the sanitary effluent collector line to a manhole associated with the collector line of the first set of sewer lines and connecting the sanitary effluent collector line to a portion of the second set of sewer lines installed in the first set of sewer lines. Step c. can be performed by in situ forming of pipe included in the second set of sewer lines. 
     A sewer system according to the present invention reduces the size of the pipe required to carry sanitary effluent and/or increases the capacity of the sewerage treatment plant to treat sanitary effluent. Since the storm water and infiltrated water are separated from the sanitary effluent, they may require little or no treatment freeing plant capacity to treat the sanitary effluent. In some cases, treatment plant expansion can be delayed or eliminated. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which: 
     FIG. 1 is a schematic block diagram of a typical prior art sewer system; 
     FIG. 2 is a schematic block diagram of a sewer system in accordance with a first embodiment of the present invention; 
     FIG. 3 is a cross-sectional view through one of the collector lines of the system shown in FIG. 2 with a nested sanitary collector line; 
     FIG. 4 is a schematic block diagram of a portion of the system shown in FIG. 2 with process devices added; and 
     FIG. 5 is a schematic block diagram of a sewer system in accordance with a second embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     There is shown in FIG. 1 a typical sanitary sewer system  10  of known construction. Each one of a plurality of building sewer systems  11   a  through  11   c  collects wastewater discharged from sources in the associated building and combines that wastewater as a discharge to a sanitary sewer system. Each one of the building sewer systems  11   a  through  11   c  is connected by an associated one of a plurality of service lines  12   a  through  12   c  respectively to a collector line  13   a . Thus, sanitary effluent from such sources as toilets, and other wastewater such as from sink drains, tub and shower drains, clothes washer drains and floor drains are combined to flow into the collector line  13   a . Also, one or more storm drains, such as a storm drain  14 , can be connected to the collector line  13   a . The collector line  13   a  and collector lines  13   b  through  13   c  feeding from other areas are connected to a trunk line  15   a . In a similar manner, other service lines, storm drains and collector lines are connected to trunk lines  15   b  and  15   c . The trunk lines  15   a  through  15   c  are connected to an interceptor line  16   a  leading to a sewerage treatment plant  17  that is connected to other interceptor lines  16   b  and  16   c . Thus, wastewater, including sanitary effluent and storm water combined, flows through the collector lines, the trunk lines and the interceptor lines in a typical sanitary sewer system  10 . 
     While the prior art sewer system  10  is adequate for most conditions, a heavy rain entering the storm drain  14  can cause a problem by exceeding the capacity of the system to carry all of the entering water to the treatment plant  17 . Overflow relief devices  18  are provided to release the wastewater from the system into drainage ditches, ponds, rivers and lakes. Although the overflow devices  18  are shown at the junction of the collector lines with the trunk line and the junction of the trunk lines with the interceptor line, the overflow devices can be connected at any suitable points in the sewerage system. A sewerage system operating near capacity may have frequent overflow problems causing contamination of swimming and boating areas with fecal matter and other wastes. Also, exceeding the system capacity causes backup through the service lines  12   a  through  12   c  typically flooding buildings with the combined sanitary effluent and storm water. The present invention seeks to solve the overflow and backup problem and increase the water treatment capacity of the sewer system by separating the sanitary effluent from the storm water as both flow through the system. 
     There is shown in FIG. 2 a first embodiment sanitary sewer system  20  according to the present invention wherein the sanitary effluent is completely separated from the remainder of the building wastewater. As also shown in FIG. 1, each of the building sewer systems  11   a  through tic is connected by an associated one of-the plurality of service lines  12   a  through  12   c  respectively to the collector line  13   a . Thus, wastewater from such sources as sink drains, tub and shower drains, clothes washer drains and floor drains is combined to flow into the collector line  13   a . However, the sanitary effluent from the toilets is connected to each of a plurality of sanitary effluent service lines  22   a  through  22   c  to carry the sanitary effluent to a sanitary effluent collector line  23   a  separate from the original collector line  13   a . While new construction can be built with the required separated plumbing, existing building would require conversion. As an alternative, the new service lines  22   a  through  22   c  could be connected to and the old service lines  12   a  through  12   c  disconnected from the existing plumbing. Sanitary effluent collector lines  23   a  through  23   c  are connected to a sanitary effluent trunk line  25   a  that is connected to a sanitary effluent interceptor line  26   a  with other sanitary effluent trunk lines  25   b  and  25   c . The sanitary effluent lines  23   a  through  23   c ,  25   a  through  25   c , and  26   a  are interconnected at connectors  28  that do not require overflow protection. Thus, the sanitary effluent is separated from the other wastewater and will not overflow or back up into the buildings when storm water overloads the system  20 . 
     Although the sanitary effluent lines  22   a  through  22   c ,  23   a  through  23   c ,  25   a  through  25   c  and  26   a  could be run parallel to the other lines  12   a  through  12   c ,  13   a  through  13   c ,  15   a  through  15   c  and  16   a , it is preferred that sanitary effluent lines run inside the other lines where possible to avoid digging separate trenches. Since existing sewer lines typically run through developed land, the installation of parallel lines can be extremely costly and very disruptive to homes and businesses. Thus, the existing sewer system  10  can be retrofitted with the new sanitary effluent lines. The sanitary effluent pipes will be of a smaller diameter than the corresponding pipes of the existing system  10  since the volume of sanitary effluent wastewater to be carried is less and the addition of pressure increases the flow rate. FIG. 3 shows the smaller diameter sanitary effluent connector line  23   a  extending inside the larger diameter collector line  13   a  that now only conveys storm water. Although the line  23   a  is shown spaced above a bottom of the line  13   a , such representation is only for the purpose of clearly illustrating two separate lines and the sanitary effluent connector line  23   a  typically would rest on the bottom of the connector line  13   a . Similarly, the sanitary effluent trunk line  25   a  would run inside the trunk line  15   a  and the sanitary effluent interceptor line  26   a  would run inside the interceptor line  16   a.    
     In order to properly convey the sanitary effluent wastewater to the treatment plant  17 , one or more process devices may be required. For example, as shown in FIG. 4, a first process device  29   a  is connected between the collector line  23   a  and the trunk line  25   a . A second process device  29   b  is connected between the trunk line  25   a  and the interceptor line  26   a . The process devices  29   a  and  29   b  can be pumping stations, grinder pumps, vacuum systems, or any other type of device used to assist the flow through the lines of the sewer system  20 . The process devices can be inserted at any point in the sewer system  20  and different types can be used together as required. 
     Since the flow through the sanitary effluent lines  23   a ,  25   a , and  26   a  is assisted by pressure or vacuum, the flow rate is greater than in a prior art gravity system for the same diameter pipe. Thus, the cross-sectional area required to flow the same volume is reduced leaving more room in the other wastewater lines  13   a  through  13   c ,  15   a  through  15   c  and  16   a  thereby increasing the capacity to carry storm water. When there is an overflow condition, the water escaping from the overflow devices  18  is not contaminated with effluent. Also, the wastewater flowing in the lines  12   a  through  12   c ,  13   a  through  13   c ,  15   a  through  15   c  and  16   a  either does not have to be treated at the plant  17  or requires only a secondary treatment. Thus, another advantage of the present invention is the freeing of significant capacity of existing plants to treat additional wastewater from the sanitary effluent lines and a reduction in the size of new treatment plants. 
     In some situations, it is desirable not to provide the sanitary effluent service lines  22   a  through  22   c  shown in FIG. 2, such as when retrofitting an existing system. There is shown in FIG. 5, a second embodiment sanitary sewer system  30  wherein the service lines  12   a  through  12   c  are connected to the sanitary effluent connector line  22   a  that runs parallel to the collector line  13   a . Both of the collector lines  13   a  and  22   a  run into a manhole  31  wherein the line  22   a  can be inserted into the line  13   a . From the manhole  31 , the sanitary effluent lines run inside the corresponding existing sewer lines as in the system shown in FIG.  2 . 
     The sewer system according to the present invention can be installed as a complete new system or during the repair of an existing system wherein the existing collector, trunk and interceptor lines are used as a first set of sewer lines that are connected to a source of storm water. The sanitary effluent lines according to the present invention are a second set of smaller diameter sewer lines that can be made of any suitable material such as plastic or composition materials and these lines can be placed in sections that are connected together or formed in situ during installation. A sewer system according to the present invention will prevent, or at least reduce overflows, and will eliminate backups into buildings. A sewer system according to the present invention provides a relatively inexpensive way to solve pollution problems and to modernize and expand existing sewer systems. 
     In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.