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negatively charged particles termed anions. The water treatment plant uses <br /> the ion exchange process to remove the charged wood treating chemicals from <br /> water. The ion exchange process for anions is shown in Figure 1. As <br /> indicated in this figure, each resin bead has many positively charged <br /> exchange sites. During the exchange process, the wood treating chemicals <br /> trade places with, or are exchanged for, other more desirable exchange <br /> ions. <br /> After all exchange sites have been filled with wood treating chemicals, <br /> the resin is exhausted. That is, the resin bead can remove no more wood <br /> treating chemicals. <br /> The removed wood treating chemicals are bound to the resin bead until <br /> they are removed through regeneration. As indicated in Figure 2, regener- <br /> ation is essentially the opposite of normal ion exchange. The wood treating <br /> chemicals are stripped from the resin beads and captured for recycling in <br /> the wood treating plant. The resin exchange sites are then refilled with <br /> the desirable exchange ions. <br /> At the beginning of a treatment run, all resin beads will be freshly <br /> regenerated and will start with the exchange sites filled with exchange <br /> ions. The entire resin bed is in the reserve state or ready for exchange. <br /> As water flows down through the exchangers, the exchange process begins <br /> immediately in the uppermost portion of the resin bed. As treatment continues, <br /> the uppermost zone of the resin bed becomes exhausted. The contaminated <br /> water will then pass untreated through the exhausted resin to the next <br /> zone, the active zone, where exchange takes place. The resin which is <br /> between the active zone and the bottom of the exchanger is the reserve <br /> zone. No exchange takes place here since the water enters this zone fully <br /> treated. The different zones are depicted in Figure 3. Throughout the <br /> S6 2 <br /> HII <br />