Solidification Disposal Outline
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- Solidification Outline
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Solidification refers to technology of isolating or encapsulating harmful materials within the waste using a solidifying agent. Stabilization converts to a chemical form, minimizing solubility of harmful pollutants within the waste and reduces harmfulness. As stabilization and solidification must happen simultaneously due to the disposal process, it is most frequently expressed as the word solidification.
Solidification was usually used for the disposal of radioactive waste and can be easily transported for the main purpose of solidification. It makes an appropriate solid material that can be stored for a long time. Such solid material decreases the possibility of exposure to pollutants and must not be decomposed. It must be cheap and be easily produced.
Solidification of sludge improved the physical/chemical ikon of the sludge by adding solidifying agent to the dehydrated cake or sludge and during final disposal, it stabilizes and makes harmless the harmful materials such as heavy metal as well as accelerating efficiency. The solidification of sludge makes harmless or changes into a state where elution is difficult. This is so that underground water or soil is not polluted through environmental medium such as harmful sludge with heavy metal contained. Therefore, arsenate and leachate during environmental pollution, transportation and disposal process is prevented.
Solidification Disposal Reaction Principle
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- Reaction Principle of Solidification
- Although the reaction principle of solidification differs slightly according to the solidifying agent, generally in the limestone group, there is absorption exothermic reaction, ion exchange reaction, pozzolan reaction and carbonization group and pozzolan reaction and hydration reaction for the cement group.
- <Conceptual Map Regarding Basic Principle of Solidification Reaction>
Solidification Method
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- Solidification/Stabilization Disposal Method
- Many solidification stabilization methods, with the purpose of safety and final disposal of harmful wastes, are currently being used or are in development. In the case of heavy metals, the inorganic processes of cement based sludge processes and lime based processes are most frequently used. The Hwasung harmful waste disposal plant that is in charge of processing and disposing harmful wastes in the country solidifies and safely reclaims heavy metal wastes and incinerator ashes using the cement based processes.
· It is easy to handle wastes
· Reduces surface area where loss and transfer of pollutants may occur
· Solubility of pollutants within the waste is reduced
· Toxicity of waste reduced
- Type of Solidifying Agents
- The solidifying agents used for sludge solidification is classified into inorganic solidifying agents and organic solidifying agents. For inorganic agents, there is cement, limestone, pozzolan and clay and it is cheap and purchasing it is easy. Organic agents have an advantage of having a high disposal cost and a high watertightness.
<Solidification Ingredient of Sludge>
| Inorganic Solidification | Organic Solidification |
|---|---|
| Cement | Urea formaldehyde |
| Limestone/Cement | Polybutadine |
| Pozzolan/Limestone | Polyester |
| Pozzolan/Cement | Epoxy |
| Clay/Cement | Acrylamide gel |
| Soluble Silicate/Cement | Bitumen |
<Property Comparison of Solidification Technology>
| Inorganic Solidification | Organic Solidification |
|---|---|
| Cheap cost | High disposal costs |
| Long term stability of physicochemical good | Very high watertightness and can be applied to diverse wastes |
| Can be applied to diverse wastes | Diverse increase of final solidifying agent volume |
| Cheap purchase of solidification ingredients | Weak stability in microorganism and UV rays |
| Processing cheap in high temperature and high pressure | Long term weakening of polymer structure to specific substances in the wastes |
| Diverse increase of solidifying agent volume due to solidifying ingredients | Limited applied cases regarding other wastes apart from radioactive wastes |
| Small solubility and good watertightness | Weak data regarding industrialized disposal method |
| Good mechanical and structural properties | Advanced technology is needed and harmful materials such as catalytic agents are used |
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- Solidification/Stabilization Disposal Method Types
- · Cement based Processes
· Lime based Processes
· Thermoplastic techniques-bitumen, paraffin and polyethylene
· Surface encapsulation techniques
· Self-cementing techniques
· Glassification etc.
Such solidification/stabilization technology of waste has wide applications according to the specific form of waste and most of them are most appropriate for inorganic wastes. To add, since disposal costs and pre-processing is needed, it has economic feasibility constraints. The things to be careful of when selecting methods for waste solidification waste are the cost of the process, increase of the material volume and the change of disposal properties.
Advantages and Disadvantages of Solidification Disposal
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- Advantages of Sludge Solidification Disposal
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· Excellent sewage and pure water sludge ikon change application
· Makes material that can be handled easily by changing the physical property of waste
· Can stop movement (melting) to the environment by integrating chemically (Reduction of solubility of pollutants within the waste)
· Reduction of surface area where the loss and transfer of pollutants may occur
· Can reuse as construction material, reclamation land and mud capping material
· Has a low influence on environment
· Cheap construction costs
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- Disadvantages of Sludge Solidification Disposal
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· Long disposal cycle compared to disposal methods using heat
· Low reduction effect due to subsidiary material insertion such as solidifying agents (total solid weight increased)
· If disposed byproduct cannot be reused, additional disposal cost needed
· Low cases of domestic installation
· Low market stability regarding solids
· Wide site area needed
· Lack of systematic test/operation data regarding sludge solidification
Process Flow Chart
- <Basic Flow Chart of Sludge Solidification Disposal>
- <Operational Conditions of sewage Sludge Solidification Disposal>