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<br />'Secondary Treatment <br /> <br />SecondarY treatment consists of two trains ~f aeration basins, eight secondary clarifiers,. and <br />the associated blowers and pUmps that function to treat and remove organic loading (BOD) <br />'and to a lesser extent 1$5 from the wastewater. On a functional basis, secondary .treatment <br />is regarded as . removing roughly twice as much BOD relative to TSS. <br /> <br />. For the design criteria basis, typical secondary treatment sizing is governed .by both average <br />and peak flow, but for MWMC, where the parallel primary 1 secondary approach (or high- <br />rate clarification approach as a second choice) is proposed for peak flow.manag.ementi the <br />peak flows will be split between primary treatment and secondary treatment. Therefore, <br />only average flow is considered in the cost allocation. <br /> <br />Combining the functional basis with the design criteria basis; the followinga1locatio~ is for <br />secondary treatment: . <br /> <br />· .Average Flow-1/4 <br />. BOD-1/2 <br />· 1'55-114 <br /> <br />Disinfection/Outfall <br /> <br />Following secondary treatment, the wastewater is disinfected (chlorinated and <br />dechlorinated) and discharged to the Willamette River through an outfall pipe. Both the <br />function and sizing of these facilities are entirely based on flow. The relationship between <br />the functional basis and design criteria is identical to that for the collection system facilities <br />and, therefore, the f~llowing allocation is for disinfec.tion/outfall: <br /> <br />· Average Flow-1/4 <br />· Peak Flow - 3/4 <br /> <br />Biosolids <br /> <br />Biosolids are a byproduct of wastewater treatment and are produced during the primary <br />treatment,. secondary treatment, and to a lesser degree tertiary treatment processes. The <br />three subcomponents used to alloc~te biosolids treatment, handling, and disposall reuse <br />costs for purposes of SDC calculations are: <br /> <br />. General' <br />· Dewatering <br />· Biocycle Farm <br /> <br />The definitionS of these subcomponents are presented in Appendix C, Growth Capacity <br />Allocation Documentation. The three subcomponents were developed for the SDC update <br />because of the differing available capacities and growth percentages associated with <br />facilities in the subcomponents. However, iri terms of allocating the facility components to <br />the wastewater parameters, the methodology is identical- independent of which <br />subcomponent is being considered. <br /> <br />A-24 <br />