The present invention is directed toward waste collection sites, and particularly toward the distribution of leachate at such sites. The invention further relates to an improved geotextile which may be advantageously used to distribute leachate.
Waste collection sites are, of course, well known and unavoidable requirements of today""s societal structures. Such sites can require large amounts of valuable land, particularly in urban areas where land is most in demand. Also, while desirable uses can be made of such lands (for example, golf courses have been built on such sites), such desirable uses typically have to wait until the land is no longer being used for collect further waste and the often high pile of waste has stabilized. While use and stabilization of such sites can take many years, there is nevertheless a desire to have that accomplished as quickly as possible, not only to increase the safety of those who might have to be at the site but also to allow for the desired use of others (for example, golfers) and to enhance the environment of those who live in the area as soon as is reasonably possible.
Toward that end, bioreactor landfills have been used to modify solid waste landfills by re-circulating and injecting leachate/liquid and air to enhance the consolidation of waste and reduce the time required for landfill stabilization. To accomplish this, vertical injection pipes and horizontal pipe fields have most often been used. With these structures, a liner is commonly provided at the bottom of the site, which liner may be used to trap leachate which has run through the collected waste above, with pipes in that area used to collect the leachate and draw it out for re-circulation by pumping it out and distributing/dispersing the leachate back into the upper portions of the waste site through, for example, perforated pipes and/or horizontal trenches.
Unfortunately, vertical injection pipes and horizontal pipe fields have been costly, time consuming to install and maintain, and not entirely effective for a number of reasons. As one example, the pipes are susceptible to clogging. As another example, the necessary use of a large number of pipes in a pipe field in order to widely distribute the leachate over a large area is not only costly, but even then virtually impossible to evenly distribute the leachate over that large area. That is, the leachate will be distributed in large part to those areas adjacent to the pipes or trenches and less so to the areas between the pipes or trenches. Typical trench spacing may be 100 to 200 feet horizontally and 40 feet vertically. As a result, such spacing significantly risks uneven or differential settling of the waste. Such differential settling, particularly in the context of such systems being in place for a number of years during which time additional layers of tons of additional waste are added on top of the original waste layers and pipe fields (and during which time heavy equipment is frequently moving around on top of the site), causes such pipe systems to be very susceptible to stress cracks and other damage, particularly given the common use of high density (stiff) resin to manufacture the pipes.
The present invention is directed toward overcoming one or more of the problems set forth above.
In one aspect of the invention, a fluid distribution structure is provided for use with a waste collection site. The structure includes a permeable material adapted for placement on one level of collected waste and adapted to receive another level of collected waste thereon, and further includes a pipe extending upwardly from the permeable material and adapted to receive the fluid. The permeable material includes a top layer, a bottom layer, and a spacing layer between the top and bottom layers, and the pipe has a lower end secured to the permeable material to discharge the fluid between the permeable material top and bottom layers. The fluid may be liquid, including leachate, or gas, or a combination thereof.
In different forms of this aspect of the invention, the top layer is one of a woven geotextile, needle punched non-woven geotextile or continuous filament geotextile, and/or the bottom layer is one of a woven geotextile, needle punched non-woven geotextile or continuous filament geotextile.
In another form of this aspect of the invention, the pipe lower end has discharge openings therein disposed above the bottom layer, and the top layer is secured around the discharge openings whereby fluid discharged from the openings is between the top and bottom layers.
In still another form, the pipe lower end includes an outwardly tapered discharge manifold, and the top layer is secured around the manifold whereby liquid discharged from the manifold is between the top and bottom layers. The manifold may be a downwardly facing cone over an aggregate fill adapted to allow flow of the fluid therethrough. The cone may also be perforated about its surface to discharge fluid out of the cone and beneath the top layer.
In further forms, one or more feeder headers extend generally horizontally through a level of collected waste above the one level of collected waste and discharge fluid into a plurality of horizontally spaced pipes.
In still another form of this aspect of the invention, the permeable material bottom layer has a flow rate FB of liquid therethrough, and the top layer has a flow rate FT of liquid therethrough, where FB less than FT.
In yet another form of this aspect of the invention, the spacing layer maintains a space between the top layer and the bottom layer, with the space being open to permit flow of liquid therein to distribute the liquid through the permeable material. The spacing layer may, in one form, be a geonet, geogrid, or mesh.
In another aspect of the present invention, a waste collection site is provided, including three layers of waste. A first geocomposite is between the first two layers of waste, and a second geocomposite is between the second and third layers of waste. A first plurality of pipes extend upwardly into the second layer of waste from the first geocomposite, and a second plurality of spaced pipes extending upwardly into the third layer of waste from the second geocomposite. At least one feeder header feeds leachate into an upper end of each of the pipes. The first and second geocomposites each include a top layer, a bottom layer, and a spacing layer between the top and bottom layers, and each of the pipes has a lower end secured to the geocomposite to discharge leachate between the top and bottom layers.
In one form of this aspect of the present invention, the pipe lower ends have discharge openings therein disposed above the bottom layer, and the top layer is secured around the discharge openings whereby leachate discharged from the openings is between the top and bottom layers. The spacing layer of the geocomposites may be disposed between the discharge openings and the top layer at each pipe lower end.
In another form of this aspect of the invention, the pipe lower ends include an outwardly tapered discharge manifold, and the top layer is secured around the discharge manifold whereby leachate discharged from the manifold is between the top and bottom layers. The discharge manifold may be a downwardly facing cone over an aggregate fill adapted to allow flow of leachate therethrough, and the cone may be perforated about its surface to discharge leachate out of the cone and beneath the top layer.
In yet another form of this aspect of the invention, the feeder header includes generally horizontal pipes in at least one of the second and third layers of waste, wherein the horizontal pipes discharge leachate into the tops of the first and second plurality of pipes.
In still another form of this aspect of the present invention, the bottom layer of the first geocomposite has a flow rate F1B of leachate therethrough, and the top layer of the first geocomposite has a flow rate F1T of leachate therethrough, where F1B less than F1T. Similarly, the bottom layer of the second geocomposite may have a flow rate F2B of leachate therethrough, and the top layer of the second geocomposite a flow rate F2T, where F28 less than F2T.
In a still further form of this aspect of the invention, the spacing layer maintains a space between the top layer and the bottom layer, with the space being open to permit flow of leachate therein to distribute the leachate through the geocomposite.
Additionally, the spacing layer may comprise one of a geonet or mesh, and the top and/or bottom layers may comprise one of a woven geotextile, needle punched non-woven geotextile or continuous filament geotextile.
In still another aspect of the present invention, a method of distributing leachate at a waste collection system is provided, comprising the steps of providing a geocomposite on one level of collected waste, adding collected waste above the material layer, and inputting leachate at spaced locations in the added collected waste above the material layer. The provided geocomposite includes a top layer, a bottom layer, and a spacing layer between the top and bottom layers, and inputting leachate includes injecting leachate between the top and bottom layers of the geocomposite whereby the spacing layer allows flow of the leachate between the top and bottom layers.
In one form of this aspect of the invention, the provided geocomposite has a bottom layer with a flow rate FB of leachate therethrough and a top layer with a flow rate FT of leachate therethrough, where FB less than FT.
In yet another aspect of the invention, a method of modifying a non-woven needle punched geotextile is provided, including the steps of calendaring the non-woven needle punched geotextile, and needle punching the non-woven needle punched geotextile after the calendaring step.
In one form of this aspect of the invention, the calendaring step includes passing the non-woven needle punched geotextile between two heated cylinders. The non-woven needle punched geotextile may also be pressured between the heated cylinders.
In another form of this aspect of the invention, the needle punching creates openings greater than 0.3 mm.
In yet another form, the needle punching step comprises passing the calendared non-woven needle punched geotextile through a needle loom.