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MWMC FACILITIES PLAN <br /> <br />tmmatched by other trait processes when it comes to meeting the low effluent CBOD and <br />TSS concentrations. <br /> <br /> 110 11 <br /> 1 O0 ~,~,,,~ -~ 1 <br /> 10 "7''~ .......................... ,,~ ~ 8,~ 9 <br /> 80 ~ ~ ~, <br /> <br />  50 59~3 <br /> 40 ~ r <br /> 30 Desired Ope ating [/ 3 <br /> 20 Pedormance to <br /> 10 ~Meet Permit <br /> <br /> O- , ,, , 0 <br /> 2000 2010 2020 2030 2040 2050 <br /> <br /> [~- Dry Weather Flow ,~ Effluent CBODs and TSS <br /> FIGURE 6.2,6-1 <br /> CBOD and TSS Operating Pedormance <br /> MWMC Facilities Plan, Springfield-Eugene <br /> <br />Wet weather operations will also benefit from effluent filtration. Wet weather flows into the <br />facility can provide very dilute wastewaters with low TSS and CBOD concentrations. For <br />this reason the 85 percent removal requirement for both CBOD and TSS during the wet <br />season are typically the most difficult standards to meet. When wet weather flows exceed <br />the secondary treatment capacity of the facility those flows are diverted arotmd secondary <br />treatment and do not receive the benefit of secondary treatment which significantly reduces <br />the CBOD and TSS of the effluent. For the blended flow stream, higher CB©D and TSS <br />concentrations are anticipated. In a worst-case scenario, assuming that the PWWF occurs <br />during the peak week flow and the peak week flow occurs durLng the peak month, the 85 <br />percent monthly removal requirement specified in the NPDES permit for BOD would <br />require filtration of a portion of the SE. This is necessary to lower the TSS and CBOD <br />adequately in the SE to compensate for the higher TSS and CBOD as a result of the blended <br />PE and SE. This is the case for all of the alternatives, and it was assumed that filtration <br />would be available because it will be reqtdred for TSS removal reliability during the dry <br />season. Filtered flow required under this worst-case scenario would be 10 mgd at 2010, and <br />30 mgd at 2025. Figure 6.2.6-2 illustrates the tertiary filtration capacity required with respect <br />to the maximum month projected flow in order to meet the 85 percent CBOD removal <br />requirement during the worst case wet season flows. <br /> <br />6-20 MWMC_6.0_REV11. DOC <br /> <br /> <br />