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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />available to maintain 5.0 mg/I of chlorine residual at maximum flow rate after release from the <br />contact chamber, and that 0.2 mg/l of chlorine residual be maintained in distant parts of the <br />distribution system. <br /> <br />Clearly, as stated in a preceding section, the contact time requirement is not met. For all <br />practical purposes, the existing plant has no contact time. According to the operator's daily <br />log for 1993, water samples taken from the distribution system consistently meet the residual <br />standard, equal to or greater than 0.2 mg/l. Thus, it appears that the addition of disinfectant is <br />currently serving its intended purpose at the locations sampled. However, for the purpose of <br />reliably producing water meeting the drinking water standard at all locations within the <br />distribution system, a contact chamber sized to provide a minimum of 30 minutes contact time <br />is required which can provide the necessary contact time. <br /> <br />4.5 Performance Limiting Factors and CCP <br /> <br />To establish a perspective of the WTP, the concept of "performance potential" is used. <br />Performance potential is, in the judgment of the evaluation engineer, the peak treatment <br />capability of the process element. It is important to note that the ratings of the treatment <br />processes given in this report are based upon achieving optimum performance such that each <br />process maintains its integrity as a barrier to the passage of turbidity, micro organisms, and <br />color. Performance potentials are shown in Figure 4. Note that the most significant <br />limitations are the clarification and the disinfection steps. <br /> <br />To describe factors which limit the performance of the Lyons WTP, problems identified in the <br />preceding sections should be related to plant performance. Performance is influenced by four <br />different aspects of the water treatment plant: design, operations, maintenance and <br />administration. Problems which are mostly related to design are generally the most <br />significant, although addressing other problems may improve performance with less cost. <br />Next, problems are rated as to significance; Le., designated "A", "B" or "C" as to major long- <br />term effects, major on a periodic basis or minor effects, respectively. The limiting factors <br />identified in this evaluation are shown in Table 6. The table is not intended to be all-inclusive. <br />Additional factors may be identified when the recommended operational studies and design <br />improvements are initiated. <br /> <br />The problems related to causes other than design, namely problems pertaining to operations, <br />maintenance and administration, are often interdependent. An approach to such problems can <br />be called a "Composite Correction Program" (CCP)(USEPA Handbook). The objective of a <br />CCP is to achieve a desired level of performance from an existing facility without major <br />modifications. The CCP systematically focuses on identifying, defining and correcting the <br />performance-limiting factors. A CCP approach is recommended for the Town of Lyons WTP. <br /> <br />25 <br />