Physical wastes

Cachexia refers to a physical wasting due to loss of muscle and fat. Cachexia is often found in end-stage cancer patients but is also caused by autoimmune disorders or by infectious diseases such as AIDS and tuberculosis. 

Cardiac cachexia Physical wasting with loss of weight and muscle mass caused by cardiac disease a wasting syndrome that causes weakness and a loss of weight, fat, and muscle. 

Production and waste disposal. Obviously, any wastes produced relate to the production process operated and the costs of disposal of physical wastes must be considered as part of the production costs. Detailed discussion of the concepts illustrated in Figure 2.2 is superfluous, but the consequences of unnecessary depletion of natural resources, the generation of poor customer relationships and higher costs all round, lead to the ultimate inevitable loss of business to those more efficient producers who have taken all such factors into account. Hence, the whole future of an industrial concern which does not address the issue of waste generation is clear. 

The average waste composition should be verified and specified in weight per cent. Physical waste data... 

From a practical point of view, water field capacity and hydraulic conductivity are very important physical waste parameters. These properties determine the amount of leachate and their formation rate. Based on the values of these parameters the operational conditions for liquids recirculating inside the landfill can be determined. These parameters depend mainly on waste particle size and organic matter content, which determine pore size distribution and the porosity of the medium. Field capacity is the value of water content held in the material after the gravitational water has drained away. The field capacity of municipal solid waste varies over a wide range between 14-44%i v/v (Zeiss Major, 1992/93, Bengtsson et al. 1994). According to an evaluation by Reinhardt and Ham (1974) the volume of liquid addition, which allows a water field capacity in waste to be reached varies between 0.1-0.2 m per Mg of solid waste (25,000-50,000 gallons per 1,000 tons). 

The process is designed from a knowledge of physical concentrations, whereas aqueous effluent treatment systems are designed from a knowledge of BOD and COD. Thus we need to somehow establish the relationship between BOD, COD, and the concentration of waste streams leaving the process. Without measurements, relationships can only be established approximately. The relationship between BOD and COD is not easy to establish, since different materials will oxidize at different rates. To compound the problem, many wastes contain complex mixtures of oxidizable materials, perhaps together with chemicals that inhibit the oxidation reactions. 

When viewing effluent treatment methods, it is clear that the basic problem of disposing of waste material safety is, in many cases, not so much solved but moved from one place to another. The fundamental problem is that once waste has been created, it cannot be destroyed. The waste can be concentrated or diluted, its physical or chemical form can be changed, but it cannot be destroyed. 

Froth flotation (qv) is a significant use of foam for physical separations. It is used to separate the more precious minerals from the waste rock extracted from mines. This method reHes on the different wetting properties typical for the different extracts. Usually, the waste rock is preferentially wet by water, whereas the more valuable minerals are typically hydrophobic. Thus the mixture of the two powders are immersed in water containing foam promoters. Also added are modifiers which help ensure that the surface of the waste rock is hydrophilic. Upon formation of a foam by bubbling air and by agitation, the waste rock remains in the water while the minerals go to the surface of the bubbles, and are entrapped in the foam. The foam rises, bringing... 

Physical Properties. Physical properties of waste as fuels are defined in accordance with the specific materials under consideration. The greatest degree of definition exists for wood and related biofuels. The least degree of definition exists for MSW, related RDF products, and the broad array of ha2ardous wastes. Table 3 compares the physical property data of some representative combustible wastes with the traditional fossil fuel bituminous coal. The soHd organic wastes typically have specific gravities or bulk densities much lower than those associated with coal and lignite. 

Table 3. Physical Properties of Waste-Based Fuels ...

Formation of Airborne Emissions. Airborne emissions are formed from combustion of waste fuels as a function of certain physical and chemical reactions and mechanisms. In grate-fired systems, particulate emissions result from particles being swept through the furnace and boiler in the gaseous combustion products, and from incomplete oxidation of the soHd particles, with consequent char carryover. If pile burning is used, eg, the mass bum units employed for unprocessed MSW, typically only 20—25% of the unbumed soHds and inerts exit the combustion system as flyash. If spreader-stoker technologies are employed, between 75 and 90% of the unbumed soHds and inerts may exit the combustion system in the form of flyash. 

Scrap from municipal refuse may be in the form of source-separated steel cans, a mixed ferrous fraction, metal magnetically separated from mixed waste or incinerator ash, and C D debris. An ASTM specification (E1134-86) was developed in 1991 for source-separated steel cans. The Steel Recycling Institute has a descriptive steel can specification entitled "Steel Can Scrap Specifications". PubHshed standards for municipal ferrous scrap also include ASTM E701-80, which defines chemical and physical test methods, and ASTM E702-85 which covers the chemical and physical requirements of ferrous scrap for several scrap-consurning industries. 

Turbulence. Turbulence is important to achieve efficient mixing of the waste, oxygen, and heat. Effective turbulence is achieved by Hquid atomization (in Hquid injection incinerators), soHds agitation, gas velocity, physical configuration of the reactor interior (baffles, mixing chambers), and cyclonic flow (by design and location of waste and fuel burners). 

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