A drop of pollutant in a pure solution creates a container of pollution. Segregating wastes and nonwastes reduces the quantity of waste that must be handled. Various technical changes and modifications provide more precise and reliable separation of materials unavoidably mixed together in a waste stream by taking advantage of different characteristics of materials, such as boiling or freezing points, density, and solubility. Separation techniques such as distillation, supercritical extraction, membranes, reverse osmosis, ultrafiltration, electrodialysis, adsorption, separate pollutants or mixed wastes back to their constituent parts (Table 6). Although simple in principle, these processes become high-tech in the precision with which they are applied to facilitate other options in the hierarchy such as recycling, treatment, and disposal.
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