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FACILITY CONCEPT E g� <br /> t ►Y • <br /> The six heavy metals used by electroplating and printed circuit S �, <br /> board firms which are currently discharged into the sewer and g <br /> 0 <br /> are now subject to pretreatment standards are copper, chromium, 8:: g �"1 77 <br /> nickel, cadmium, zinc and .lead. These metals along with $►J Sit o 8 <br /> cyanide, which is also present in some of these waste waters, <br /> will be treated at the Facility so that participating firms can <br /> comply with discharge regulations. <br /> A preliminary Facility concept has been developed as part of a <br /> proposal submitted by MRC to the MWCC, as well as the °po <br /> conceptual feasibility work done for the Metropolitan <br /> Councils' Resource Recovery Task Force. While certain ; q. o• <br /> components of the Facility's scope may change as a result of C o e: • ; <br /> pilot scale testing and preliminary design work, major = �e <br /> components described in this section are expected to be <br /> incorporated into the Facility's final design. c <br /> Explicit in the Facility's design is treatment and recovery. <br /> The treatment technologies include those processes which render f ca <br /> the aqueous inorganic wastes received by the Facility more e <br /> amenable to recovery, less expensive to handle and/or less z o 0 <br /> hazardous to manage. The use of these treatment processes may <br /> occur as in-plant modifications in the electroplating or H <br /> printed circuit- shops participating in the project, or done at <br /> the Facility itself. The recovery systems, on the other hand, <br /> are those processes designed to extract raw materials (chrome, <br /> nickel, zinc, etc.) from appropriately treated wastes. A <br /> general process flow sheet is presented in Figure 1. This c �o <br /> shows the overall relationship of the incoming feed stocks to ;� �• <br /> the Facility's various treatment technologies and recovery • <br /> systems. The incoming feedstock includes ion exchange �g <br /> canisters, metal-specific waste water solutions (batch dumps) <br /> and solids (metal-specific and mixed metal sludges). The <br /> following individual treatment and recovery systems that are to = <br /> be involved in the proposed Facility are described in detail. _ <br /> m • <br /> Ion Exchange e <br /> . o <br /> nH <br /> The ion exchange process is a stoichiometric chemical reaction <br /> whereby an ion from a solution is exchanged for a similarly <br /> charged ion that is attached to an immobile solid particle. s ` <br /> These particles make up a granular solid called an ion exchange <br /> resin. This process is utilized in the metals pre-treatment a "' <br /> process to concentrate the metals present in the waste water at p: <br /> the plant so that transportation of the metals to the Facility - <br /> for recovery will be more economical. Ion exchange may also be <br /> used to treat spent plating baths as an end of pipe treatment <br /> but its greatest value is in the recovery applications. <br /> A-2 • r o`v <br /> Z C <br /> 1 <br />