Liquid purification or separation – Processes – Separating
Reexamination Certificate
2000-05-01
2002-07-16
Reifsnyder, David A. (Department: 1723)
Liquid purification or separation
Processes
Separating
C210S800000, C210S807000, C210S758000, C210S209000, C210S304000, C210S512100, C210S519000, C055S459100, C055S459300
Reexamination Certificate
active
06419843
ABSTRACT:
FIELD OF USE
The invention relates generally, but is not so limited, to sewer devices, and more particularly to sewer devices used to reduce odorous gas emissions and to reduce hydrogen sulfide corrosion and abrasive wear in waste water conveyance, collection and treatment systems.
BACKGROUND OF THE INVENTION
Throughout past decades, sewers have been utilized to efficiently transport waste water or sewage from locations where it was generated to waste water treatment plants and other destinations. These sewers consist generally of pipelines locate below ground level and oriented with a slight downward grade in the direction of the sewage flow. Gravity acts upon the sewage to cause it to flow within the pipelines toward its ultimate destination. These pipelines are sometimes interconnected by “drop structures” that allow the sewage to flow from one line into the drop structure, drop vertically therewithin, and then to flow out of the drop structure into additional pipes or other structures.
One problem that occurs during the transport of sewage is the release of sulfides from the sewage. Sulfides form as a result of bacterial reduction of sulfates within the sewage in an anaerobic environment. As sewage ages, the level of sulfides increases. Drop structures within a sewer system can provide a beneficial aeration of the sewage flow by introducing additional dissolved oxygen into the flow. The dissolved oxygen reacts with the sulfides, resulting in less chemical volatility in the sewage. This aeration is particularly beneficial where the sewage is fresh and contains a relatively small amount of dissolved sulfides, such as hydrogen sulfide (H
2
S).
Unfortunately, in most practical applications, sewage contains a significant amount of potentially volatile dissolved molecular hydrogen sulfide gas. Turbulence within the sewage flow can cause this dissolved gas to be released into the surrounding air. Significant sources of turbulence in sewage flow, and hence the emission of hydrogen sulfide gas in a sewer, occur in drop structures such as interceptor drop maintenance holes, joint structures, forcemain discharges and wet well drops in sewer pumping stations. Thus, while drop structures can reintroduce dissolved oxygen into the sewage flow, lowering the level of hydrogen sulfide gas, they can also cause the release of hydrogen sulfide gas. The hydrogen sulfide emissions often cause corrosion with the drop structures and adjacent sewer lines, and cause odor problems even the most elegant, pristine neighborhoods.
One known type of drop structure comprises an influent line, a maintenance hole and an effluent line. The influent line runs almost horizontally at a relatively shallow depth below the ground surface in the form of a pipe. The maintenance hole is located below the street level maintenance hole manhole cover. The maintenance hole is generally cylindrical in shape with a vertical longitudinal axis. The effluent line is another almost horizontal pipe that exits slightly above the bottom of the maintenance hole. Turbulent waste water flow is created when the sewage, which has a substantial amount of potential energy, exits from the influent line near the top of the maintenance hole and tumbles down like a waterfall to the side wall and base of the maintenance hole. Then the sewage pools and eventually flows out the effluent line. This turbulent action releases hydrogen sulfide gas into the air. To reduce the problem of gas release, while still allowing beneficial aeration of the sewage, the potential and kinetic energy in the sewage must be dissipated.
One known method is to create a wall hugging spiral flow down the maintenance hole to dissipate the energy by friction. The spiral flow is generated by the insertion of a vortex form connected to the influent line near the top of the maintenance hole. The vortex form is generally helical in shape and is placed directly below the manhole cover near the top of the maintenance hole. The vortex form channels and diverts the flow from its languid state into a spiral flow descending down the cylindrical wall of the maintenance hole. The vortex form can be made of concrete with applied protective coating, or made of a noncorrosive material, metal or plastic, such as PVC, High Density Polyethylene (HDPE) or other like materials. The vortex form may be manufactured at the factory or on-site.
Two problems remain to be solved when applying this known method of using a vortex form in a drop structure for sewage flows. First, the upstream flow velocities within the influent line are usually not large enough to create a stable spiral flow on the vertical wall of a typical maintenance hole. Thus, the flow, rather than continuing to spiral down the cylindrical wall of the maintenance hole, will generally revert to a turbulent descending flow similar to waterfall, losing the effective energy dissipation of the spiral flow and releasing significant amounts of hydrogensulfide gas into the air. Second, quite often the maintenance hole is used for additional lateral influent connections at elevations lower than the main influent pipe. Consequently, the lateral influent connections disrupt the spiral flow and create a turbulent waterfall of sewage to the bottom of the maintenance hole, again releasing significant amounts of hydrogen sulfide gas into the air. The additional influent pipe may run in any direction, but at a lower depth than the main influent pipe.
SUMMARY OF INVENTION
It, therefore, is an object of this invention to provide an improved sewer apparatus for an interceptor drop maintenance hole or any similar flow drop structure.
Another object of the invention is to provide an improved sewer apparatus that significantly reduces odorous gas emissions from the sewer.
A further object of the invention is to reduce hydrogen sulfide corrosion in waste water conveyance, collection and treatment systems.
A benefit of this invention is the improved way in which it helps to protect sewer structure and lines from abrasive wear.
Another benefit is the way the invention improves the quality of wastewater by wastewater aeration.
Another important benefit is the way the invention improves rehabilitation of the existing sewer drop structure. The vortex form and conduit assembly, prefabricated as one unit, can be installed into the drop structure without flow bypassing.
The foregoing objects and benefits of the present invention are provided by an improved sewer apparatus and method. The improved sewer apparatus comprises a maintenance hole and an influent line for carrying sewage to the maintenance hole, a vortex form which accepts the sewage from the influent line, the vortex form comprising a spiral channel of decreasing diameter disposed substantially within the maintenance hole, and a conduit also disposed within the maintenance hole and fluidly connected to the vortex form and extending substantially downwardly from the vortex form to a flow exit near the maintenance hole base. The sewage flowing from the influent line enters the vortex form and is channeled by the vortex form into a spiral flow with a diameter smaller than the maintenance hole wall diameter. The reduction in the diameter of the channel outer wall causes the centrifugal forces acting upon the sewage flow to increase, forcing the flow to continue in intimate contact with the outer wall of the channel. The sewage then flows from the reduced diameter of the vortex channel into the conduit and, aided by gravity and the sewage flow's acquired rotational velocity, continues its spiral descent towards the maintenance hole base, in substantially intimate contact with the conduit wall. The spiral flow then exits the conduit near the maintenance hole base into an energy dissipating pool.
The improved sewer apparatus creates an accelerated sewage flow sufficient to create substantial intimate contact with the vortex form and conduit wall throughout the sewage flow's descent in the maintenance hole. This intimate contact creates frictional forces that reduce the kinetic energy of the flo
Briggs and Morgan P.A.
Niederluecke Kurt J.
Reifsnyder David A.
Stone Jeffrey R.
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