Resolution No. 4793 - Laserfiche WebLink

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MWMC FACILITIES PLAN m~matched by other trait processes when it comes to meeting the low effluent CBOD and TSS concentrations. 110 ...... 11 ~ 40 ........ ~ 4 30 - rating- 3 20 -- PeRormance to ~ 2 ~ 0 .... Meet Permit ~ 0 , , , , 0 2000 2010 2020 2030 2040 2050 {~ Dry CBOB5 and TSS Weather Flow Effluent FIGURE 6.2.6-1 CSOD and TSS Operating Pedormance MWMC Facilities Plan, Springfield-Eugene Wet weather operations will also benefit from eftluent filtration. Wet weather flows into the facility can provide very dilute wastewaters with low TSS and CBOD concentrations. For this reason the 85 percent removal requirement for both CBOD and TSS during the wet season are typically the most difficult standards to meet. When wet weather flows exceed the secondary treatment capacity of the facility those flows are diverted arotmd secondary treatment and do not receive the benefit of secondary treatment which sigmificm~tly reduces the CBOD and TSS of the effluent. For the blended flow stream, higher CBOD and TSS concentrations are anticipated. In a worst-case scenario, assuming that the PWWF occurs during the peak week flow and the peak week flow occurs during the peak month, the 85 percent monthly removal reqtdrement specified in the NPDES permit for BOD would require filtration of a port, on of the SE. This is necessary to lower the TSS and CBOD adequately in the SE to compensate for the higher TSS and CBOD as a result of the blended PE and SE. This is the case for all of the alternatives, and it was assumed that filtration would be available because it will be reqttired for TSS removal reliability during the dry season. Filtered flow required under this worst-case scenario would be 10 mgd at 2010, and 30 mgd at 2025. Figure 6.2.6-2 illustrates the tertiary filtration capacity required with respect to the maximum month projected flow in order to meet the 85 percent CBOD removal requirement during the worst case wet season flows. 8-20 MWMC_80_REVI 1 DOC