Patent Application
20210039147
Landfills typically have a pit or “cell” where solid waste is deposited for permanent disposal. The waste that is deposited in such a cell generally has to pass a “paint filter” test, meaning that the waste needs to be solid enough in composition so that it does not permeate through filters such as those used to filter paint. By maintaining that the waste in the disposal cell has a certainly level of solidity, the waste may not be prone to permeating through the barriers and liners maintained at the boundaries of the cell. Nevertheless, disposal cells generally include multiple, permanent layers of low-permeability materials to prevent waste from leaching out of the landfill into the surrounding soil.
Often, at least some of waste that arrives at the landfill is too fluidic to pass the paint filter test. For example, in well-drilling applications, cuttings that are separated from the mud, despite being separated, may still include too much hydrocarbon or other fluids to allow the cuttings to be placed directly into the disposal cell. Accordingly, a drying pad may be provided. In a drying pad, the wet waste is spread out, open to the atmosphere and the sun, so it may dry. Dirt, sawdust, etc. may be added to the fluidic waste to further dry it. Thus, heavy equipment is often called for, which is used to spread the fluidic waste and mix in the drying additives. The drying pads can be quite large (e.g., acres), and generally are required to have a very low permeability, given the fluidic-waste application and the desire to avoid such waste fluid leaching into the soil around the drying pad. Accordingly, an impermeable membrane, typically a compacted clay layer or geosynthetic clay liner are used to prevent any fluids from permeating the soil beneath the drying pad.
As mentioned above, however, heavy equipment is used on the drying pad to work and move the material. To avoid this equipment damaging the relatively fragile liners and/or compacted clay, several feet of soil can be placed on top of the clay and liner. This design works well and is generally the standard in the industry for drying pads. However, despite the presence of the sacrificial soil layer, the liner and/or clay beneath is eventually damaged during the life of the drying pad. Thus, continual maintenance, and the time, energy, and expense associated therewith, is required to keep the drying pads working to prevent leachate.
Embodiments of the disclosure provide a method for constructing a drying pad for a wet waste. The method includes adding a polymer additive to a soil to create a polymer-augmented soil, and spreading the polymer-augmented soil over a base soil to create drying pad comprising a polymer-augmented soil layer on top of the base soil. The polymer-augmented soil is configured to have the wet waste deposited thereon so that the wet waste dries on top of the polymer-augmented soil layer without leaching into the base soil and produces a dried waste for transfer to a disposal cell. The method also includes removing the polymer-augmented soil layer from the base soil after the dried waste is transferred to the disposal cell.
Embodiments of the disclosure further provide a drying pad for a landfill. The drying pad includes a base soil layer, and a polymer-augmented soil layer disposed on top of the base soil layer, wherein the polymer-augmented soil layer includes a polymer additive, and is harder and less permeable than the base soil layer.
Embodiments of the disclosure also provide a method for drying a wet waste in preparation for disposal in a landfill. The method includes selecting an area proximal to a disposal cell for a drying pad, loosening a layer of soil in the area selected for the drying pad, adding a polymer additive to the loosened soil to create a polymer-augmented soil, spreading and compacting the polymer-augmented soil on a base soil to create a polymer-augmented soil layer, curing the polymer-augmented soil layer, depositing the wet waste directly on the cured polymer-augmented soil layer so that the wet waste dries on top of the polymer-augmented soil layer and produces a dried waste, after the wet waste dries to produce the dried waste, transferring the dried waste to the disposal cell, removing the polymer-augmented soil layer from the base soil after transferring the dried waste to the disposal cell, and transferring the polymer-augmented soil layer to the disposal cell after removing the polymer-augmented soil layer from the base soil.
The present disclosure may best be understood by referring to the following description and accompanying drawings that are used to illustrate embodiments of the invention. In the drawings:
The following disclosure describes several embodiments for implementing different features, structures, or functions of the invention. Embodiments of components, arrangements, and configurations are described below to simplify the present disclosure; however, these embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, the present disclosure may repeat reference characters (e.g., numerals) and/or letters in the various embodiments and across the Figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed in the Figures. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. The embodiments presented below may be combined in any combination of ways, e.g., any element from one exemplary embodiment may be used in any other exemplary embodiment, without departing from the scope of the disclosure.
Additionally, certain terms are used throughout the following description and claims to refer to particular components. As one skilled in the art will appreciate, various entities may refer to the same component by different names, and as such, the naming convention for the elements described herein is not intended to limit the scope of the invention, unless otherwise specifically defined herein. Further, the naming convention used herein is not intended to distinguish between components that differ in name but not function. Additionally, in the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to.” All numerical values in this disclosure may be exact or approximate values unless otherwise specifically stated. Accordingly, various embodiments of the disclosure may deviate from the numbers, values, and ranges disclosed herein without departing from the intended scope. Finally, unless otherwise provided herein, “or” statements are intended to be non-exclusive; for example, the statement “A or B” should be considered to mean “A, B, or both A and B.”
The drying pad 104 may be positioned near the disposal cell 102, e.g., adjacent thereto, as shown. The drying pad 104 may be configured to receive relatively fluidic (wet) waste 110, and may allow the waste to be exposed to the atmosphere, the sun, etc., e.g., by providing a relatively impermeable area for the wet waste to be spread out. Once the wet waste is dried or solidified, the waste may be transferred to the disposal cell 102 for permanent disposal. In other words, the waste 110 is temporarily placed on the drying pad 104.
The polymer additive may change the characteristics of the soil, such that the soil layer 202 is less permeable and harder than the base layer 200. For example, once the polymer additive is mixed in and cured, the augmented soil layer 202 may have a permeability of between about 1×10−9 cm/s and about 1×10−7 cm/s. Further, the hardness of the soil layer 202 may be between about 400 psi and about 800 psi, e.g., about 600 psi, or greater. The soil layer 202 may have a thickness of between about 4 inches and about 12 inches, e.g., about 8 inches. Thus, the soil layer 202 may be substantially harder than compacted clay or traditional liners, but not as hard (or expensive) as, for example, concrete. As such, the soil 202 may be able to directly receive the wet waste and may support the heavy earth-moving equipment that is used to work the wet waste, while resisting damage as compared to clay or liners. Thus, in some embodiments, another layer of sacrificial soil may not need to be placed on top of the polymer-augmented soil layer 202, but in other embodiments, such a sacrificial soil layer may be used.
The method 300 may also include determining an amount of polymer additive and a polymer-augmented soil layer depth for the drying pad 104, as at 304. For example, the polymer-augmented soil layer may, e.g., to comply with regulatory requirements, be designed to have a specific permeability and/or specific hardness, e.g., in the ranges noted above. These characteristics may be at least partially based on the composition of the soil, prior to application of the polymer additive, which may impact the amount of polymer additive and the depth of the polymer-augmented soil layer. For example, soil that is more uniformly sized (“well graded”) may require more polymer additive and/or a thicker layer. Soil that is less uniformly sized (“poorly graded”) may require less polymer additive and/or a thinner layer, by comparison. Accordingly, determining at 304 may include taking soil samples to determine soil properties, which in turn are used to determine an amount of polymer additive to add and a thickness/depth for the polymer-augmented soil layer.
The method 300 may also include loosening (tilling) a layer of soil in the area that was selected, as at 306. The area may have a base soil, which may extend a depth that exceeds the depth that is loosened. Accordingly, the loosened soil and the base soil may, initially, be of the same general composition, e.g., including the same amounts of sand, gravel, clay, etc., to the extent the base soil is generally of a homogenous composition itself. The soil may be loosened using earth-moving equipment, and the area that was selected may be an acre or more in size.
Once the soil is loosened, the polymer additive may be added to the loosened soil, as at 308. This may be accomplished by mixing the polymer additive with a solvent (e.g., water). The soil may then be “worked” (e.g., moved around by the earth moving equipment) to mix the polymer additive with the soil, thereby producing a polymer-augmented soil that has generally a consistent amount of polymer additive throughout.
The polymer-augmented soil may then be spread and/or compacted on the base soil in the area, as at 310. As such, a layer of polymer-augmented soil is created (e.g., layer 202 on top of base soil 200 in
Accordingly, the wet waste for disposal may then be deposited on the polymer-augmented soil layer, as at 312. The wet waste may then be allowed to dry, as at 314, which may include passively waiting for evaporation and/or actively adding materials, such as sawdust, to the wet waste, as described above. Wet waste is defined as waste that is too fluidic to pass the paint filter test. By contrast, after drying the wet waste, a dried waste is produced. Dried waste is defined as waste that does pass the paint filter test, although it may still be somewhat fluidic in consistency or appearance.
The dried waste may then be transferred into the disposal cell 102, as at 316. In contrast to the drying pad 104, the disposal cell 102 is permanent and includes potentially several low-permeability layers configured to confine the contents of the disposal cell 102 indefinitely.
At some point, the usefulness of the drying pad 104 reaches an end, e.g., when the disposal cell 102 is full, or when no further wet waste is to be received. At this point, the drying pad 104 may be removed. To remove the drying pad 104, the method 300 includes removing the polymer-augmented soil layer, as at 318. This may include again using the earth-moving equipment to dig up the polymer-augmented soil layer and expose the base soil. The removed polymer-augmented soil layer may then be transferred into the disposal cell 102, as at 320.
The foregoing has outlined features of several embodiments so that those skilled in the art may better understand the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.
This application claims priority to U.S. Provisional Patent Application No. 62/882,793, which was filed on Aug. 5, 2019 and is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62882793 | Aug 2019 | US |
