Processing Techniques for Solid Waste

The purpose of this subsection is to introduce the reader to the tech-niqiies and methods used to recover materials, conversion products, and energy from solid wastes. Topics to be considered include (I) processing techniques for solid waste, (2) processing techniques for hazardous wastes, (3) materials-recoveiy systems, (4) recovery of biological conversion products, (5) therm processes, and (6) waste-to-energy systems. 

Processing Techniques for Solid Wastes Processing techniques are used in solid-waste-management systems to (I) improve the efficiency of the systems, (2) to recover resources (usable materials), and (3) to prepare materials for recoveiy of conversion produc ts and energy. The more important techniques used for processing solid wastes are summarized in Tables 25-61 and 25-62. 

Stochastic or probabilistic techniques can be applied to either the moisture module, or the solution of equation (3) — or for example the models of Schwartz Crowe (13) and Tang et al. (16), or can lead to new conceptual model developments as for example the work of Jury (17). Stochastic or probabilistic modeling is mainly aimed at describing breakthrough times of overall concentration threshold levels, rather than individual processes or concentrations in individual soil compartments. Coefficients or response functions and these models have to be calibrated to field data since major processes are studied via a black-box or response function approach and not individually. Other modeling concepts may be related to soil models for solid waste sites and specialized pollutant leachate issues (18). 

All the NPPs have their own systems for managing the solid and liquid radioactive waste generated at the site. The very low level waste (VLLW) and the low and intermediate level short lived radioactive waste (L IL SL) waste is eonditioned in accordance with the waste acceptance criteria for the landfill type and the SFR repository respectively. Standard techniques are used processing liquid and solid waste. Cement and bitumen are used as matrix for conditioning. 

Manual Component Separation The manual separation of solid-waste components can be accomplished at the source where solid wastes are generated, at a transfer station, at a centralized processing station, or at the disposal site. Manual sorting at the source of generation is the most positive way to achieve the recoveiy and reuse of materials. The number and types of components salvaged or sorted (e.g., cardboard and high-quality paper, metals, and wood) depend on the location, the opportunities for recycling, and the resale market. There has been an evolution in the solid waste indus-tiy to combine manual and automatic separation techniques to reduce overall costs and produce a cleaner product, especially for recyclable materials. 

TABLE 25-62 Summary of Techniques Used for Processing Solid Wastes... 

At some plants the blast furnace dust is recycled as feedstock to the sinter plant. At plants without sintering operations, blast furnace dust is sometimes mixed with other byproduct residues, briquetted, and recycled back to the blast furnace. In other plants, the dust is landfilled or stockpiled.1 Several techniques are available for removing the zinc and lead. The majority of blast furnace sludge is land disposed as solid waste or stockpiled. Because of the similarity between wastewater sludges generated by sinter plants and blast furnaces, these streams are commingled and cotreated.1 The blast furnace slag is cooled and processed to be reused for various applications such as onsite in-land reclamation and landfill construction. 

The main objectives of this chapter are to (1) review the different modeling techniques used for sorption/desorption processes of organic pollutants with various solid phases, (2) discuss the kinetics of such processes with some insight into the interpretation of kinetic data, (3) describe the different sorption/ desorption experimental techniques, with estimates of the transport parameters from the data of laboratory tests, (4) discuss a recently reported issue regarding slow sorption/desorption behavior of organic pollutants, and finally (5) present a case study about the environmental impact of solid waste materials/complex... 

Reactor Wastes. The same fimdamental approach of immobilization and disposal is being taken for reactor wastes. Work has been underway in AECL for several years on immobilization techniques (21). These include volume reduction processes of incineration for combustible materials and reverse osmosis for concentrating solids from aqueous streams. The concentrates from these processes will be immobilized in bitumen. The deep underground disposal facility developed for fuel wastes will most likely also be used for the iinnobilized reactor wastes. 

Incineration is often regarded as a very efficient technique for municipal solid waste (MSW) management. However, the environmental impacts of MSW incineration need to be carefully taken into account. The most relevant problem with MSW incineration is flue gas treatment. However, another often overlooked issue is the disposal of solid byproducts of the incineration process. MSW incinerators essentially produce two types of solid by-products, that is, slag, or bottom ash, and fly ash, often mixed with various other chemicals used for flue gas treatment. Bottom ash and—even more—fly ash are regarded as dangerous wastes mainly due to their potentially toxic elements (PTE) content and their tendency to leach such PTE to the environment. 

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