Recycling alternatives can be accomplished either on-site or off-site and may depend on a company's staffing or economic constraints. On-site recycling alternatives result in less waste leaving a facility. The disadvantages of on-site recycling lie in the capital outlay for recycling equipment, the need for operator training, and additional operating costs. In some cases, the waste generated does not warrant the installation costs for in-plant recycling systems. However, since on-site alternatives do not involve transportation of waste materials and the resulting liabilities, they are preferred over off-site alternatives.
For instance, sand used in casting processes at foundries contains heavy metal residues such as copper, lead, and zinc. If these concentrations exceed Toxicity Characteris tics Leaching Procedure (TCLP) standards, the sand is a hazardous waste. Recent experiments demonstrated that 95% of the copper could be precipitated and recovered (McCoy and Associates 1989). In another example, a pho-toprocessing company uses an electrolytic deposition cell to recover silver from rinse water used in film processing equipment. By removing the silver from the wastewater, the wastewater can be discharged to the sewer without additional pretreatment.
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