JP2013247860A - Recycled soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide recycled soil which is produced by using inexpensively and stably available recycled material and has functionality that improves existing soil.SOLUTION: Recycled soil contains: water-retaining raw material comprising at least one kind of incinerated ash produced from general or industrial wastes or water and sewage sludge, dehydrated cake obtained by dehydrating and drying water and sewage sludge, and mechanically dried aggregate; and silt raw material comprising at least one kind of molten slug, gypsum waste material, crushed-stone powder and screenings.

Description

  The present invention relates to recycled soil using recycled materials such as waste.

  In recent years, attention has been focused on recycled soil using waste recycling materials. As one of such things, Patent Document 1 describes planting soil such as plants and vegetables using a dehydrated cake obtained by recycling waste.

Dehydrated cake is a solidified sludge generated from the municipal water and sewage treatment plants, meets certain safety standards, and exhibits a neutral pH of 7 to 8 in aqueous solution.
Since dehydrated cake is a recycling material that is continuously generated in a large amount in each local government, by using such a material, inexpensive planting soil can be continuously supplied. Moreover, since the amount of waste can be reduced by using recycled materials, the problem of shortage of waste disposal sites is also solved.

JP 2007-306844

  Recycled soil is expected to be used as soil for planting soil such as plants and vegetables as described in Patent Document 1 as well as soil for ground and roadbed material for paving. Recycled soil may be used alone or mixed with existing soil.

When the recycled soil is used alone in the above applications, it is required to have excellent water retention and water permeability. Conventionally, sand powder is blended in order to improve soil water retention and water permeability. However, sand powder is expensive to process for fine particle formation and particle size adjustment.
Moreover, when it mixes and uses for the existing soil, it not only has the outstanding water retention and water permeability, but the function which improves the property of soil is also calculated | required. For example, plants may not grow on strongly acidic or strongly alkaline soils or may adversely affect the human body. When mixed with such soils, the existing soil must be neutral for recycled soil. The function which can be brought close to is required. Conventionally, it has been difficult to produce soil having such a function using only recycled materials as raw materials, and it has been necessary to blend artificially chemically synthesized soil improvement materials and the like.

  The problem to be solved by the present invention is that it is possible to produce a recycled material that can be stably obtained at low cost as a raw material, and has excellent water retention and water permeability, and has a functionality for improving existing soil. Is to provide.

Recycled soil according to the present invention made to solve the above problems is
Incinerated ash produced from general waste or industrial waste or water and sewage sludge, dehydrated cake obtained by dewatering and drying water and sewage sludge, and water retention raw material consisting of at least one kind of mechanically dried aggregate,
Molten slag,
Silt raw material consisting of at least one of gypsum waste, crushed stone powder, and screenings,
It is characterized by comprising.

  The machine-dried aggregate is formed by mechanically drying water and sewage sludge into granules of 10 mm or less. When manufacturing recycled soil to be used as a surface material for soil, it is desirable to use a machine-dry aggregate adjusted to a particle size of 5 mm or less by sieving the machine dry aggregate to prevent the particle size of the soil from becoming too large. . The machine dry aggregate has water permeability because it has a lower water content than incinerated ash and dehydrated cake. Molten slag is produced by melting general waste (city waste), industrial waste or water and sewage sludge at a high temperature, decomposing and removing heavy metals and harmful substances, and then cooling. Gypsum waste is recycled by separating and recycling paper after crushing and crushing gypsum boards that are discarded when building is newly constructed or demolished. Crushed stone powder is a waste material generated during wet processing such as washing crushed stone in a quarry, quarry, sand making factory, etc., and is a sandy fine particle having an extremely fine particle size. The screenings are prepared by sieving crushed rocks or slags to adjust the particle size. Gypsum waste, crushed stone powder, and screenings are all low-cost silt raw materials.

  Any of the raw materials contained in the recycled soil according to the present invention is a waste recycling material. Incinerated ash, dehydrated cake, and machine-dried aggregate are excellent in water retention. In addition, since the particle size of the molten slag can be adjusted to an appropriate size, pores having an appropriate size can be formed inside the soil to impart water permeability. Furthermore, gypsum waste, crushed stone powder, and screenings are low-cost silt raw materials, and both water retention and water permeability of recycled soil can be improved by finely adjusting the particle size. It is desirable that the water retention material and the molten slag are mixed in a proportion of 20% to 70% of the total amount of the recycled soil, and the silt raw material is mixed in a proportion of 20% or less of the total amount of the recycled soil.

  Among the silt raw materials, gypsum waste is a gypsum waste mainly composed of calcium sulfate, so that the recycled soil containing the gypsum waste contains a lot of calcium. Since the adsorption property of calcium to soil is higher than the adsorption property of sodium, by mixing the recycled soil according to the present invention with alkaline soil containing a lot of sodium, sodium is discharged from the soil to neutral or weak alkaline soil. It can be modified.

  The gypsum waste material preferably contains phosphate gypsum. Phosphoric gypsum is a waste calculated as a by-product when producing phosphoric acid from phosphate ore. Conventionally, calcium carbonate has been used as an improving material for bringing acidic soil with excess aluminum closer to neutral soil. However, calcium carbonate has a low solubility in water, so it can only improve the soil surface. could not. On the other hand, gypsum phosphate can discharge aluminum in the same manner as calcium carbonate, and has higher water solubility than calcium carbonate, so it can modify the soil to the lower soil. Moreover, phosphorus which is a large amount essential element can be included in soil by including a phosphate gypsum.

The recycled soil according to the present invention includes at least one of incinerated ash produced from general waste or industrial waste or water and sewage sludge, dehydrated cake obtained by dewatering and drying water and sewage sludge, and machine-dried aggregate. The water retaining material and the water permeable slag excellent in water permeability, and the silt material consisting of at least one of gypsum waste, crushed stone powder, and screenings are excellent in water retaining property and water permeability. Any of the above-mentioned silt materials can be manufactured at a lower cost than before because the processing cost is lower than that of sand powder.
Further, when gypsum waste is used as a silt raw material, the recycled soil to be produced contains a large amount of calcium because it contains gypsum waste, which is a gypsum waste mainly composed of calcium sulfate. Since the adsorption property of calcium to soil is higher than that of sodium, sodium can be discharged from alkaline soil and modified to neutral or weak alkaline soil.
Since the recycled soil according to the present invention can be produced using a waste material generated in large quantities as a raw material, the raw material can be stably obtained at low cost.

  The recycled soil according to the present embodiment is at least one of incinerated ash produced from general waste or industrial waste or water and sewage sludge, dewatered cake obtained by dewatering and drying water and sewage sludge, and mechanically dried aggregate. And a silt raw material comprising at least one of gypsum waste material, crushed stone powder, and screenings.

  As described above, dehydrated cake is a recycled material that is generated continuously and in large quantities in each municipality. In addition, incineration ash of general waste or industrial waste or water and sewage sludge, and machine-dried aggregate obtained by adjusting the particle size by drying water and sewage sludge are also recycled materials generated continuously and in large quantities in each local government. It is. Therefore, they are expected to be stably supplied at present and in the future.

  Molten slag is produced by melting general waste (city waste), industrial waste, or water and sewage sludge at high temperatures, decomposing and removing heavy metals and harmful substances, and then cooling and producing them in an appropriate size. Use after adjusting the particle size. By reusing the molten slag, it is possible to circulate resources. Molten slag also shows neutral pH 7-8 in an aqueous solution, similar to a purified water sludge dehydrated cake. Among the molten slags, there is also a molten slag that forms a foam by gasifying the gas in the slag during cooling.

  There are many municipal waste melting treatment facilities nationwide, and more than 800,000 tons of molten slag are produced annually. Therefore, the molten slag is also expected to be supplied stably over the present and future.

  Gypsum waste is recycled by separating and recycling paper after crushing and crushing gypsum boards that are discarded when building is newly constructed or demolished. Nearly 2 million tons of gypsum waste are discharged annually. Therefore, it is expected that gypsum waste will be supplied stably in the present and future. Crushed stone powder is a waste material generated during a wet process such as washing crushed stone in a quarry, quarry, sand making factory, etc., and is a fine sandy particle having a very small particle size. The screenings are prepared by sieving crushed rocks or slags to adjust the particle size. Gypsum waste, crushed stone powder, and screenings are used for fine particle size adjustment to increase the water permeability and water retention of the soil.

  Conventionally, when fine particle size adjustment is performed, sand powder is used which is costly for processing for making fine particles or adjusting the particle size. In contrast, gypsum waste, crushed stone powder, and screenings are low in processing costs. In particular, crushed stone powder and screenings are raw materials that have been finely divided or adjusted in particle size in advance, so that no processing costs are required. Therefore, by using crushed stone powder or screenings instead of sand powder, it is possible to produce soil made of only waste recycling materials at low cost. There is little demand for these because they easily purify mud with rainwater and the like, and most of them are landfilled as industrial waste. In view of such a current situation, it is preferable to use gypsum waste, crushed stone powder, and screenings as silt raw materials as in this example.

  Hereinafter, an embodiment of the recycled soil according to the present invention will be described. The recycled soil of this example contains 20% to 70% of the total amount of soil each containing a water retention raw material (a raw material including at least one of dehydrated cake, incinerated ash, and mechanically dried aggregate), and gypsum. The silt raw material which consists of at least 1 type of waste materials, crushed stone powder, and screenings was mix | blended and included so that it might contain in the ratio of 30% or less. In addition, paper sludge and recycled crushed stone, which are waste recycling materials, were blended as appropriate as in the above raw materials. Paper sludge is granulated ash obtained by carbonizing the waste produced in the paper making process, and has excellent water absorption. When paper sludge is blended, the weeds do not spread moisture, so the effect of suppressing weed growth can be expected.

  The recycled soil according to the present example is excellent in water retention and water permeability because it contains the water retention material, the molten water slag that is excellent in water permeability and the particle size can be adjusted to an appropriate size, and the silt material. In particular, recycled soil containing gypsum waste, which is a gypsum waste mainly composed of calcium sulfate as a silt raw material, contains a large amount of calcium. Since the adsorption property of calcium to soil is higher than the adsorption property of sodium, sodium can be discharged from alkaline soil and modified to neutral or weak alkaline soil.

The recycled soil according to this example has large pores between the aggregates inside the soil, and small pores inside the aggregates. If this recycled soil is used as planting soil, the activities of soil microorganisms and soil small organisms are activated, and an environment in which many nutrients necessary for the growth of plants and the like are generated is formed. Suitable for training. Moreover, the recycling soil containing a gypsum waste material as a silt raw material contains not only calcium mentioned above but many sulfur. Since calcium and sulfur are essential elements in large quantities such as plants, the recycled soil of this embodiment can be suitably used as planting soil containing nutrients necessary for growing plants and the like.
When the recycled soil according to the present embodiment is used as planting soil or turf floor soil, it is desirable to include machine-dried aggregate as a water retention material. This is because the specific gravity of the machine-dried aggregate is smaller than that of other water retaining materials, so that the degree of compaction can be prevented from becoming too high.

  As another example, recycled soil containing gypsum phosphate gypsum as a gypsum waste material was produced. Phosphoric gypsum is a waste calculated as a by-product when producing phosphoric acid from phosphate ore. Since the gypsum phosphate is more water-soluble than calcium carbonate that has been used to improve acidic soils, it can exert a soil improvement effect up to the subsoil. Moreover, in addition to the calcium and sulfur mentioned above, phosphorus can also be included by including a phosphate gypsum. Since phosphorus is also a large amount of essential elements such as plants, the recycled soil of this embodiment can also be suitably used as planting soil.

Claims (4)

Incinerated ash produced from general waste or industrial waste or water and sewage sludge, dehydrated cake obtained by dewatering and drying water and sewage sludge, and water retention raw material consisting of at least one kind of mechanically dried aggregate,
Molten slag,
Recycled soil characterized by comprising as raw materials a silt raw material comprising at least one of gypsum waste, crushed stone powder, and screenings.   The water-retaining raw material and the molten slag are each contained in a proportion of 20% to 70% of the total amount, and the silt raw material is contained in a proportion of 30% or less of the total amount. Recycled soil as described.   The recycled soil according to claim 1 or 2, wherein the gypsum waste material contains gypsum phosphate.   Recycled soil according to any one of claims 1 to 3, characterized in that it contains paper sludge.