Patent Application
20180237350
This invention relates to soils, particularly artificial soils, and methods for manufacturing artificial soils.
Topsoil degradation and loss continue to be significant problems. Topsoil is the topmost layer of soil that supports plant growth and is therefore essential to supporting life on the Earth. Despite its importance, it is estimated that the United States is losing topsoil 10 times faster than a replenishment rate, which is the rate at which topsoil is produced naturally. Other industrialized countries are losing topsoil at even more frightening rates. For example, topsoil loss rates in China are estimated to be 40 times faster than the replenishment rate. As a result, more land is becoming more unproductive as the nutrients in the topsoil are depleted or the topsoil is lost altogether. When combined with an increase in demand for agricultural products as the population of the Earth grows, topsoil degradation and loss become even more worrisome.
Topsoil loss may be through erosion by water and by wind. It is thought that the topsoil carried away by erosion is ultimately discharged into the oceans of the world and is not recoverable. Other causes of topsoil loss may include strip mining and earthworks, such as road construction. In each, the topsoil may be stripped away or the topsoil is left exposed and is lost through erosion.
In the agricultural industry, farmers have developed no-till agricultural techniques by which seeds are planted without tilling the topsoil. These types of techniques reduce topsoil loss by leaving residual roots and debris from a previous year's planting in place. The untilled roots and debris form a layer of cohesiveness which binds the topsoil in place and thereby resists erosion. However, no-till techniques only slow down topsoil loss. And, the problems do not end with only topsoil loss.
Degradation of topsoil may be by overproduction by which the soil is depleted of essential nutrients. This is one reason that fertilizers are used, that is to replace essential nutrients for plant growth, which are often crops. Fertilizers may be in liquid or solid form and may be distributed on the soil prior to or following planting. While the fertilizers provide essential nutrients, such as nitrogen and phosphorus, other nutrients may be beneficial for plant growth. These may include potassium-containing compounds and calcium-containing compounds that modify the pH in the soil.
Commercial fertilizers often require significant energy in their production. Other less energy-intensive fertilizers include organic-based fertilizers from animals, including humans, in the form of feces and urine. These organic-sourced fertilizers are plentiful and cheap. In many developed countries, industry, hospitals, and households produce human feces and urine that are mixed with water and are centrally collected at a wastewater treatment plant. So, they are available in bulk.
A process at the wastewater treatment plant removes much of the contaminants (i.e., bio, organic, and inorganic contaminants) from the water. The solids, including feces, are commonly referred to as sewage sludge and may also be referred to as biosolids. The treated water is discharged from the wastewater treatment plant as an effluent. The biosolids are then further treated or are disposed of via landfill or incineration.
Treatment of the biosolids may further remove contaminants. However, fecal coliform bacteria and other bacteria may remain in the treated biosolids. This problem may be exclusive to human originated biosolids. While not directly harmful to human health, the presence of fecal coliform bacteria in water may indicate the presence of pathogens that are directly harmful to human health. Human originated biosolids may be tested to determine whether they present a danger for use as fertilizer.
In the U.S., biosolids from treatment plants may be rated by the level of fecal coliform bacteria present in accordance with 40 C.F.R. § 503. These classifications are referred to as Class A Biosolids and Class B Biosolids. Class A Biosolids have a lower level of fecal coliform bacteria than Class B Biosolids. According to that regulation, Class B Biosolids are limited in use and may be applied only to land utilized to grow fodder. Class A Biosolids are not restricted as to their application and so may be used to grow crops for human consumption.
While available, these classes of biosolids are not a replacement for topsoil but may be applied as a fertilizer to enhance the available essential nutrients of degraded topsoil. Moreover, there are other problems with use of these biosolids. For one, they may not be indiscriminately applied to land with existing plants. Direct contact with plants may destroy them. In addition, extensive application of biosolids followed by precipitation may wash the biosolids into nearby water sources and so may contaminate local drinking water.
Instead, human originated biosolids are often applied prior to plant growth, are worked into the soil, or are diluted prior to application. As a result of possible bacterial contamination and the difficulties and timing of application of biosolids, large quantities of biosolids are left unused. This resource is often landfilled or incinerated as a result.
There remains a need for reducing topsoil degradation and loss and for providing a viable alternative to topsoil that aids vegetation growth and crop production.
The present invention overcomes the foregoing and other shortcomings and drawbacks of human originated biosolids heretofore known for growing vegetation. While the invention will be described in connection with certain embodiments, it will be understood that the invention is not limited to these embodiments. On the contrary, the invention includes all alternatives, modifications and equivalents as may be included within the spirit and scope of the present invention.
In accordance with the principles of the present invention an artificial soil for growing vegetation comprises a mixture of biosolids from a wastewater treatment plant, at least one of synthetic gypsum and a gypsum-depleted by-product from a process that produces gypsum separately from the gypsum-depleted by-product, and a calcium compound from at least one of a lime kiln dust, a fluidized bed ash, and a ball mill lime.
In one embodiment, the at least one of the lime kiln dust, the fluidized bed ash, and the ball mill lime is present in an amount sufficient to heat the mixture to at least about 132° F. following mixing.
In one embodiment, the mixture further includes at least one of silica and alumina. In one embodiment, the at least one of silica and alumina is from the one of the lime kiln dust, the fluidized bed ash, and the ball mill lime. In one embodiment, the artificial soil further includes hydrated lime.
In one embodiment, the gypsum-depleted by-product is from a process that produces the synthetic gypsum.
In one embodiment, the mixture includes at least about 1/9 by volume of biosolids.
In one embodiment, the mixture includes from about ⅛ to about ½ by volume of the calcium compound.
In accordance with the principles of the present invention, a method of manufacturing an artificial soil comprises mixing biosolids from a wastewater treatment plant with at least one of synthetic gypsum and a gypsum-depleted by-product from a process that produces gypsum separately from the gypsum-depleted by-product and at least one of a lime kiln dust, a fluidized bed ash, and a ball mill lime.
In one embodiment, during mixing, the at least one of the lime kiln dust, the fluidized bed ash, and the ball mill lime is added in an amount sufficient to heat the mixture to at least about 132° F.
In one embodiment, mixing further includes mixing hydrated lime with the biosolids.
In one embodiment, mixing the at least one of the gypsum and gypsum-depleted by-product with the biosolids is prior to mixing the biosolids with the at least one of the lime kiln dust, the fluidized bed ash, and the ball mill lime.
In one embodiment, the gypsum-depleted by-product is from a process that produces the synthetic gypsum.
In one embodiment, prior to mixing, the method comprises adding about 50 vol. % biosolids to about 50 vol. % of the synthetic gypsum.
In one embodiment, mixing includes adding from about 1/9 to about ½ by volume of the at least one of the lime kiln dust, the fluidized bed ash, and the ball mill lime in the mixture.
In one embodiment, mixing includes adding at least one of silica and alumina.
In one embodiment, addition of the at least one of silica and alumina is included in the at least one of the lime kiln dust, the fluidized bed ash, and the ball mill lime.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description of the embodiments given below, explain the principles of the invention.
With reference to
The artificial soil 10 may be applied to land which lacks topsoil or to soil that is degraded. Embodiments of the invention may therefore permit a layer of topsoil to be manufactured, which can facilitate immediate plant growth at locations which would not otherwise support vegetation for many years. These locations may include newly constructed earthworks, such as roads, strip mines, and landfills among others. Embodiments of the present invention are not limited to these exemplary applications. As an example, the artificial soil 10 may be directly applied to crop land to enhance natural topsoil already present. As another example, the artificial soil 10 may be mixed with natural topsoil prior to distributing the mixture on land. The artificial soil 10 may act as an extender in these situations. As yet another example, the artificial soil 10 may be mixed with clay, which generally does not support plant growth, prior to distributing that mixture on land.
In the exemplary embodiment shown in
The load hopper 32 directs the mixture 34 onto a conveyor belt 36 or other materials transfer device. As shown, the conveyor belt 36 carries the mixture 34 proximate silos 40 and 42. The silo 40 may house the LKD 20 or the fluidized bed ash 24 in a position to discharge it in continuous fashion on the mixture 34 as it passes beneath the silo 40. The silo 42 may house the hydrated lime 22 or the ball mill lime 26 in a position to discharge it onto the mixture 34 as it passes beneath the silo 42. The discharge from any single one of the silos 40, 42 may be by way of an auger, vane feeder, or belt conveyor though the system is not limited to these named devices. Although two silos 40 and 42 are shown, a single silo may be sufficient to deposit any one or a combination of the LKD 20, the hydrated lime 22, the fluidized bed ash 24, and the ball mill lime 26 onto the mixture 34. The volumetric ratio of the mixture 34 to any one of the LKD 20, the hydrated lime 22, the fluidized bed ash 24, and the ball mill lime 26 may be adjusted by changing the speed of the conveyor belt 36 past the silos 40, 42 and/or the feed rate of the individual materials from the silos 40, 42 to the conveyor belt 36.
Once deposited onto the mixture 34, one or more of the LKD 20, the hydrated lime 22, the fluidized bed ash 24, and the ball mill lime 26, and the mixture 34 are carried into a mixer 44. By way of example only, the mixer 44 may be a pug mill or a paddle mixer. The mixer 44 thoroughly mixes each of the mixture 34 and one or more of a combination of the LKD 20, the hydrated lime 22, the fluidized bed ash 24, and the ball mill lime 26.
During or immediately subsequent to mixing, the temperature increases to about 143° F. or higher, for example to at least about 230° F. In one embodiment, the ratio of the lime-containing materials (i.e., the LKD 20, the hydrated lime 22, the fluidized bed ash 24, and the ball mill lime 26) in the artificial soil 10 is sufficient to heat the artificial soil 10 to above about 132° F. for at least about 72 hours. The temperature may increase to about 230° F. or to about 270° F. within about 35-40 minutes of mixing. By way of example, the ratio of lime-containing material to biosolids 16 may be from about 4 wt. % to about 25 wt. % lime-containing material per ton of biosolids 16. By way of specific example, the LKD 20 may be in the range of about 4 wt. % to about 18 wt. % per ton of biosolids 16. The ratio may depend on the efficacy of the lime-containing materials. There may be some variation in the potency of each of these lime-containing materials. As the potency decreases, the amount of the lime-containing material added must be increased and as the potency increases, the amount of lime-containing material can be reduced. In one particular example, 10 wt. % of the LKD 20 to biosolids 16 may be sufficient to heat the artificial soil 10 following exit from the mixer 44 to a temperature of about 132° for about 72 hours. In that regard, the artificial soil 10 may be classified as a Class A material.
With reference to
With reference to
The water treatment process has many purposes. One purpose is to oxidize any calcium sulfite to calcium sulfate. In
Additional treatment of the stream after removing the synthetic gypsum 12 may include a secondary water treatment process in a clarifier 60. Addition of various flocculation polymers in the clarifier 60 facilitates flocculation of fine, unsettled particles. The flocculated particles settle under gravity. Other additives may be added to the clarifier 60 or at other locations, for example other additives may include biocides to control the bacteria content.
Once the flocculated particles settle in the clarifier 60, they are pumped through an additional dewatering step, such as through a hydrocyclone 62. The discharge from the hydrocyclone 62 may be introduced into a decanter centrifuge 66 which may further dewater the waste stream followed by a pug mill 64. In addition to recycled water being discharged from the decanter centrifuge 66, the OFS 14 (i.e., gypsum depleted by-product) is also discharged. OFS 14 may appear as an orange, paste-like sludge. Synthetic gypsum 12, by contrast, is a pure white material. The OFS 14 is a waste product, or by-product, of the FGD process following removal of commercially pure gypsum. Similar to the gypsum 12, in one embodiment, the OFS 14 may include a significant proportion of water. By way of example only, the OFS 14 may include from about 35 wt. % to about 50 wt. % moisture, though the OFS may average about 43 wt. % moisture. Typically, the OFS 14 is dumped in a landfill. Details regarding products and methods of making products that include OFS are found in commonly-owned U.S. Pat. Nos. 8,303,842; 8,389,439; 8,669,203; and 9,045,367, which are incorporated by reference herein in their entireties. It will be appreciated that while the gypsum 12 and the OFS 14 are described as being produced from related processes, embodiments of the present invention are not limited to a single process that produces synthetic gypsum 12 and the OFS 14. For example, synthetic gypsum 12 may be produced from a process in which no OFS is manufactured.
With reference to
In that regard, the filtered sewage is pumped into a tank where the solids settle under gravity. This stage may include multiple settling processes. The settled sludge is continuously scraped from the bottom of the tank and pumped away for further treatment. In a second stage, the water and any unsettled sludge is pumped to an aeration tank in which air is pumped through the water. Oxygen in the air encourages the bacteria present to break down any residual solids in the tank after sludge removal. The aerated water may be pumped to another settling tank where any residual solids form sludge at the bottom of the settling tank. A final filtering process through a bed of sand and/or carbon may remove any remaining solid particles from the water before the water is released to the environment.
Wastewater treatment may also include biological nutrient removal processes in which microorganisms remove organic matter, nitrogen, and phosphorous. This process may also include exposing the microorganisms to ultraviolet light to inactivate pathogenic microorganisms.
The sludge from the settling processes may be pumped into a digester in which anaerobic digestion reduces the volume of the sludge while producing methane and carbon dioxide gases. Following digestion, the remaining sludge may be used in the formation of the artificial soil 10 as the biosolids 16 shown in
With reference to
With reference to
With reference to
With reference to
The artificial soil 10, shown in
In order to facilitate a more complete understanding of the invention, the following non-limiting examples are provided. The biosolids in each of the examples below were provided by the Clermont County Wastewater District in Ohio. Also, in each of the examples that follow, it is believed that the temperature of the mixture reached at least approximately 172° F. and remained at that temperature for from 2 to 4 hours after mixing in a cement mixer.
One 5 gallon bucket of biosolids was mixed with one 5 gallon bucket of ball mill lime. The mixing ratio was about 1 to 1 by volume. The ball mill lime was provided by Zimmer Power Station. The two buckets were dumped into a cement mixer and then mixed.
Table 1 lists analytical results for a sample of the ball mill lime used in the Examples.
The resulting mixture was poured into a 13 inch by 24 inch wooden tray to a depth of about 6 inches. Grass seed was distributed across the top of the artificial soil. The grass seed was a “Kentucky 31” mixture of blue grass, fescue, clover, and other seed. In normal environmental conditions, the grass seed germinated in about 2 days. A picture of the grass after approximately 3 weeks in the soil of Example 1 is shown in
One 5 gallon bucket of biosolids was mixed with ¼ of a 5 gallon bucket of LKD. The mixing ratio was one to about one quarter by volume. The buckets were dumped into a cement mixer and then mixed.
Table 2 lists the equivalent oxide composition of the LKD used in the Examples.
The resulting mixture was poured into a 13 inch by 24 inch wooden tray to a depth of about 6 inches. Grass seed was distributed across the top of the artificial soil. The grass seed was a “Kentucky 31” mixture of blue grass, fescue, clover, and other seed. In normal environmental conditions, the grass seed germinated in about 2 days. A picture of the grass after approximately 3 weeks in the soil of Example 2 is shown in
The table below provides another exemplary composition of the LKD usable in artificial soils. By way of further example, the constituents usable in artificial soil may range from the composition of Table 2 to the composition provided in Table 3.
One 5 gallon bucket of biosolids was mixed with ¼ of a 5 gallon bucket of LKD of Example 2 and one 5 gallon bucket of ball mill lime of Example 1. The buckets were dumped into a cement mixer and then mixed.
The resulting mixture was poured into a 13 inch by 24 inch wooden tray to a depth of about 6 inches. Grass seed was distributed across the top of the artificial soil. The grass seed was a “Kentucky 31” mixture of blue grass, fescue, clover, and other seed. In normal environmental conditions, the grass seed germinated in about 2 days. A picture of the grass growing in the soil of Example 3 is shown in
One 5 gallon bucket of synthetic gypsum from the Zimmer Power Station at Moscow, Ohio, was mixed with one 5 gallon bucket of ball mill lime of Example 1 and one 5 gallon bucket of biosolids. The buckets were dumped into a cement mixer and then mixed. See
The resulting mixture was poured into a 13 inch by 24 inch wooden tray to a depth of about 6 inches. Grass seed was distributed across the top of the artificial soil. The grass seed was a “Kentucky 31” mixture of blue grass, fescue, clover, and other seed. In normal environmental conditions, the grass seed germinated in about 2 days. A picture of the grass after approximately 3 weeks in the soil of Example 4 is shown in
One 5 gallon bucket of ball mill lime of Example 1 was mixed with one 5 gallon bucket of synthetic gypsum of Example 4 and ¼ of a 5 gallon bucket of biosolids. The buckets were dumped into a cement mixer and then mixed.
The resulting mixture was poured into a 13 inch by 24 inch wooden tray to a depth of about 6 inches. Grass seed was distributed across the top of the artificial soil. The grass seed was a “Kentucky 31” mixture of blue grass, fescue, clover, and other seed. In normal environmental conditions, the grass seed germinated in about 2 days. A picture of the grass after approximately 3 weeks in the soil of Example 5 is shown in
One 5 gallon bucket of ball mill lime of Example 1 was mixed with one 5 gallon bucket of biosolids and one 5 gallon bucket of topsoil. The buckets were dumped into a cement mixer and then mixed.
The resulting mixture was poured into a 13 inch by 24 inch wooden tray to a depth of about 6 inches. Grass seed was distributed across the top of the artificial soil. The grass seed was a “Kentucky 31” mixture of blue grass, fescue, clover, and other seed. In normal environmental conditions, the grass seed germinated in about 2 days.
One 5 gallon bucket of OFS from the Zimmer Power Station was mixed with one 5 gallon bucket of biosolids and one 5 gallon bucket of gypsum of Example 4. The buckets were dumped into a cement mixer and then mixed. Table 5 lists an exemplary compositional analysis of OFS usable in artificial soils.
The resulting mixture was poured into a 13 inch by 24 inch wooden tray to a depth of about 6 inches. Grass seed was distributed across the top of the artificial soil. The grass seed was a “Kentucky 31” mixture of blue grass, fescue, clover, and other seed. In normal environmental conditions, the grass seed germinated in about 2 days. A picture of the grass after approximately 3 weeks in the soil of Example 7 is shown in
One 5 gallon bucket of biosolids was mixed with one 5 gallon bucket of synthetic gypsum of Example 4. The buckets were dumped into a cement mixer and then mixed.
The resulting mixture was poured into a 13 inch by 24 inch wooden tray to a depth of about 6 inches. Grass seed was distributed across the top of the artificial soil. The grass seed was a “Kentucky 31” mixture of blue grass, fescue, clover, and other seed. In normal environmental conditions, the grass seed germinated in about 2 days. A picture of the grass growing in the soil of Example 8 is shown in
One quarter of a 5 gallon bucket of limestone sand was mixed with ⅛ of a 5 gallon bucket of LKD and one 5 gallon bucket of biosolids. Tables 6A and 6B collectively provide an exemplary analytical composition of limestone sand.
Alternative compositions of limestone sand are found in
The resulting mixture was poured into a 13 inch by 24 inch wooden tray to a depth of about 6 inches. Grass seed was distributed across the top of the artificial soil. The grass seed was a “Kentucky 31” mixture of blue grass, fescue, clover, and other seed. In normal environmental conditions, the grass seed germinated in about 2 days. A picture of the grass after approximately 3 weeks in the soil of Example 9 is shown in
One 5 gallon bucket of OFS of Example 7 was mixed with one 5 gallon bucket of biosolids and one 5 gallon bucket of ball mill lime of Example 1. The buckets were dumped into a cement mixer and then mixed.
The resulting mixture was poured into a 13 inch by 24 inch wooden tray to a depth of about 6 inches. Grass seed was distributed across the top of the artificial soil. The grass seed was a “Kentucky 31” mixture of blue grass, fescue, clover, and other seed. In normal environmental conditions, the grass seed germinated in about 2 days. A picture of the grass after approximately 3 weeks in the soil of Example 10 is shown in
One 5 gallon bucket of OFS of Example 7 was mixed with one 5 gallon bucket of biosolids and ½ of a 5 gallon bucket of synthetic gypsum of Example 4 and ½ of a 5 gallon bucket of LKD of Example 2. The buckets were dumped into a cement mixer and then mixed.
The resulting mixture was poured into a 13 inch by 24 inch wooden tray to a depth of about 6 inches. Grass seed was distributed across the top of the artificial soil. The grass seed was a “Kentucky 31” mixture of blue grass, fescue, clover, and other seed. A picture of the soil after approximately 3 weeks is shown in
One 5 gallon bucket of OFS of Example 7 was mixed with one 5 gallon bucket of biosolids and ½ of a 5 gallon bucket of synthetic gypsum of Example 4 and one 5 gallon bucket of ball mill lime of Example 1. The resulting mixture was poured into a 13 inch by 24 inch wooden tray to a depth of about 6 inches. Grass seed was distributed across the top of the artificial soil. The grass seed was a “Kentucky 31” mixture of blue grass, fescue, clover, and other seed. A picture after approximately 3 weeks is shown in
In each of the examples above, each of a 5 gallon bucket of ball mill lime, a 5 gallon bucket of LKD, a 5 gallon bucket of OFS, and a 5 gallon bucket of biosolids weighs about 45 pounds.
Potential applications for artificial soils that support plant growth include topsoil replacement in areas that lack sufficient soil quantity and/or quality of soil, such as around new construction.
The following tables provide a comparison of various characteristics of each of the Examples 1-12, above.
As described above, a fluidized bed ash may be usable in artificial soils described herein. An exemplary fluidized bed ash composition is provided in the table below.
While the present invention has been illustrated by the description of one or more embodiments thereof, and while the embodiments have been described in considerable detail, they are not intended to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages, products and applications will readily appear to those skilled in the art. The invention is therefore not limited to the specific details, representative method and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope of the general inventive concept.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/462,139 filed on Feb. 22, 2017, the disclosure of which is expressly incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62462139 | Feb 2017 | US |
