Chemistry: fertilizers – Processes and products – Organic material-containing
Reexamination Certificate
2000-05-31
2003-03-25
Langel, Wayne A. (Department: 1754)
Chemistry: fertilizers
Processes and products
Organic material-containing
C047SDIG001, C071S031000, C071S032000, C071S903000, C210S711000, C405S128350, C405S263000
Reexamination Certificate
active
06537340
ABSTRACT:
TECHNICAL FIELD
This invention pertains to the use of water treatment residuals resulting from drinking water treatment. More specifically, this invention pertains to methods and apparatuses for reusing water treatment residuals, such as alum residuals, generated by drinking water treatment facilities, by converting the alum-type residuals into a form which is more beneficial than has been known heretofore. Alum-type residuals in such a form may be added to other materials to form a blended topsoil.
BACKGROUND OF THE INVENTION
Water treatment residuals are produced by drinking water supply and purification plants in the treatment process. Such residuals are produced when alum or similar materials are used to cause particulate matter in the water to precipitate. Alum-treated water is then placed in one or more sedimentation basins. While in these basins, the alum associates with raw water turbidity, causing it to precipitate, thereby simultaneously clearing the water and producing alum oi alum-polymer water treatment residual. The cleared water is then removed from the basins for further treatment for use as drinking water. Over time, the water treatment residual accumulates at the bottom of the basins. The residuals are removed from the sedimentation basins and stored in lagoons or tanks. These residuals contain raw water turbidity and unreacted alum and/or alum polymer coagulants and reactive hydroxide compounds. In the past, some alum and alum polymer water treatment residuals have been disposed of in licensed, solid-waste landfill facilities after being de-watered, such as via filter presses at the sites or by other suitable methods. In many states, current state EPA policies prohibit direct land application of alum water treatment residuals. Further, concerns have been raised and associated with landfill disposal of large volumes of alum residuals. While the waste product may not pose imminent hazards to the public or the environment, the presence of alum residuals in a landfill is generally considered to be undesirable.
One alternative to disposing of alum residuals from water treatment facilities has been to reuse the material in the environment as a blended topsoil since the residual is predominantly fine particulate soil components. However, the primary environmental concern associated with alum residual reuse as a soil additive is nutrient binding by the residual. This binding is caused by hydroxides, present in the residual, which bind nutrients such as phosphorus, making them unavailable for use by vegetation.
Another concern with using alum residual is that alum residual contains very limited concentrations of vegetation nutrients in excess of typical soils, and has a diminished value as a low-grade fertilizer in comparison to sewage sludge. However, alum residual has been shown to increase soil moisture holding capacity, which is a major problem associated with course grained or highly organic soils. Additionally, alum residual has been found to reduce the compressive strength of soils, allowing increased root penetration through the soil.
The applicant has recognized the need to provide a process for reusing or recycling alum residuals, particularly alum and alum polymer residuals. Potential uses for alum-type residuals have been considered, mainly compost blending, landfill cover material blending, land application, and topsoil blending.
Compost blending involves blending alum-type residuals with composted materials prior to sale or reuse as an enhanced topsoil material. Composted material contains many nutrients that enhance the ability of soil to sustain vegetation. However, because compost materials originate from decayed organic materials, the compost materials are more acidic than typical soils. Acidic soil conditions can cause metals to be placed in solution, creating a toxic soil condition known as phytotoxicity.
Landfill cover material blending involves blending alum residuals with materials used as cover materials at licensed solid waste disposal facilities. Currently, there is a very limited supply of materials suitable for landfill covers that are also capable of sustaining vegetation. Unprocessed alum residual, however, may not be suitable due to the presence of hydroxides noted above and concomitant nutrient binding. However, use of residuals in a waste disposal facility would allow residuals to be comingled with regulated wastes, potentially creating future remediation liability.
Direct land application involves applying dry or gelatinous alum-type residuals directly to the surface of land, such as farmland, for example. The alum-type residual may be applied to the land and later plowed into the soil to blend the alum-type residual and natural soil. Such applications are of detrimental, however, because of the gelatinous nature of alum-type residual and the potential for nutrient binding. Application of the gelatinous alum-type residual will preclude adequate mixing of the residual with the soil, leaving the alum-type residual in large clumps at or near the surface of the soil after plowing. The potential for nutrient binding by hydroxides also makes this use unattractive, especially for farmland. Additionally, in many states, current state EPA policy prohibits direct land application of such alum-type residuals. Topsoil blending involves blending alum-type residual with topsoil prior to sale or reuse as landscaping topsoil. Topsoil blending would not involve licensed waste facilities, and therefore, would pose a much lower risk for long term liability exposure than landfill cover material blending. Current methods of processing, however, are not well suited for large or small scale use because alum residuals must be granular and sufficiently dewatered for blending. Previous attempts at using alum residual as a soil additive were unable to overcome the limitations of nutrient binding caused by the presence of hydroxides.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an improved method of processing alum-type residuals resulting from the treatment of water for the production of potable water.
It is another object of the present invention to provide alum-type residual in a form that is easier to work and blend with other materials than those that have been known heretofore.
It is still another object of the present invention to provide an alum-type residual with less potential for adverse chemical interactions upon mixing with other materials.
It is yet another object of the present invention to provide a process for the use of alum-type residuals from a drinking water treatment facility by processing alum-type residuals into a form which is easier to work and less reactive than previously known forms, and blending the alum-type residual with topsoil components.
It is still another object of the present invention to provide an improved blended topsoil product with improved physical properties comprising alum-type residuals and top soil components.
These and other objectives are achieved by providing a more thorough and economical method of conditioning alum-type residual than was previously known. This invention also provides a processed alum-type residual that has less reactive hydroxide components than previously known alum-type residuals. The processed alum-type residual of the present invention is also more easily mixed with other materials due to the granular texture of the processed alum-type residual. This granular texture and decreased water content of the processed residual of the present invention provides a residual that is more easily mixed with topsoil components on a large scale than was previously known.
In accordance with the present invention, a new and improved method for reusing water treatment residuals, particularly alum residuals, is provided which overcomes the problems associated with disposal of such water treatment residuals while at the same time producing a blended topsoil with improved physical characteristics.
More particularly, in accordance with the present invention, a process
Langel Wayne A.
Renner Kenner Greive Bobak Taylor & Weber
Upcyclers, Inc.
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