DOMESTIC REFUSE

The minerals processing industry has made contributions to all areas of technology, both in terms of products and processing. Technologies developed in the mineral industry are used extensively in the chemicals industry as well as in municipal and industrial waste treatment and recycling industry, eg, scrap recycling, processing of domestic refuse, automobiles, electronic scrap, battery scrap, and decontamination of soils. 

Site history - industrial contamination, mining, domestic refuse, old foundations, cellars, tunnels ... 

Extensive available level sites have sometimes previously accommodated gas works, chemical works, munitions factories, or industrial or domestic refuse tips. These sites require special consideration as regards protection of the stmcture to be built, the constmction workforce and the building occupants. 

An important application of fluidisation which has attracted considerable interest in recent years is fluidised bed combustion. The combustible material is held in a fluidised bed of inert material and the air for combustion is the fluidising gas. The system has been developed for steam raising on a very large scale for electricity generation and for incineration of domestic refuse. 

The results of the inventory on solid wastes are combined to form three waste categories special wastes, wastes resembling domestic refuse and building rubble/ gangue material. 

Due to the extensive use of plastics in packaging, most of the plastics waste is found in domestic refuse. Table 1.3 summarizes the plastics waste generated by... 

The particulate matter carried forward in gas streams can also cover a wide range of materials including inorganic mineral matter, organic particles and "natural" materials like wood particles. Inorganic substances possibly with carbon particles, are common foulants in combustion systems where fossil ftiels like oil and coal or waste materials like domestic refuse are burnt. Even with "clean" fuels such as natural gas, problems of fouling may arise as a result of poor combustion... 

These ratios indicate that there is a need for a very different secondary air supply in the combustion of urban waste compared with coal. In addition, because the deposits associated with domestic refuse combustion are generally alkali metal salts of relatively low melting point, it may be necessary to consider diluting the gases leaving the combustion space to reduce their temperature to below 650°C, the sintering temperature of the salts. The dilution may be achieved by the use of tertiary mr but this will, of course, reduce the thermal efficiency of the equipment. 

All the temperatures for the coal ash are significantly higher than the corresponding temperatures for the refuse derived fuel. The reason for these differences is that the ash produced by the combustion of domestic refuse, is different in chemical composition from the ash associated with coal combustion. 

In general, the empirical test methods developed over the years for traditional fossil friels (coal, oil and natural gas) are not applicable to waste materials because they have been developed to match the expected impurities in the fossil fiiels rather than those that may be present in the waste. Assessment is further complicated by the diflflculty of obtaining a representative and reliable sample of the waste for testing. The problem is acute in solid wastes such as domestic refuse, where considerable variations in consistency can occur. Sampling of other solid wastes such as plastic offcuts (from a particular source) or straw, are likely to be more reliable. Ultimately it will be necessary for the operator to determine optimum operating conditions in the light of empirical experience as described in Chapter 17. 

Fig. 17.24 presents some data obtained using the probe during the combustion of simulated domestic refuse. 

Domestic refuse would normally produce leachate with the highest BOD (high strength leachate) but may be low in individual hazardous components. However, even domestic refuse will not be free of hazardous materials. According to Jones-Lee and Lee (1993), it has been estimated that each person (in the USA) contributes 4 litres.yr of hazardous chemicals to their household waste stream. These chemicals can include pesticides, paint residues, and mercury from fluorescent tubes and batteries. Commercial waste may also produce a high strength leachate, while waste classified as "inert" is, in effect, seldom inert and often contains a proportion of degradable components which may lead to the production of a leachate capable of [>ollution. 

Pfeffer, J.T. (1974) Temperature effects on anaerobic fermentation of domestic refuse. Biotech. Bioeng., 16,771-787. 

The consumer society produces more and more refuse. A number of sol utions to this problem have been proposed. In some countries refuse is burnt to generate electric power. In Germany, producers must take back unwanted packaging for recycling. In other 5 cou ntries, householders are asked to separate out refuse so that it can be recycled more easily. This text describes an experimental plant in Holland designed to recycle domestic refuse. 

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