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<br />, Secondary Treatment <br /> <br />Secondary treatment consists of two trains of aeration basins, eight secondary cl~ers, and <br />the associated blowers and pumps that function to treat and remove organic loading (BOD) <br />and to a lesser extent 1SS from the wastewater. OIl a functional basis, secondary treatment <br />is regarded as removing roughly twice as much BOD ,r,elative to 1SS. <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 I secondary approach (or high- <br />rate clarification approach as a second choice) is proposed for peak flow management, the <br />peak flows will be split between primary -treatment and secondary treatment. Therefore, <br />o~y average flow. is considered in the cost allocation. <br /> <br />Combining the functional basis with the design criteria basis, the following allocation is for <br />secon~ary treatment: <br /> <br />. Average Flow - 1/4 <br />. BOD - 1/2 <br />. 1SS-1/4 <br /> <br />, Disinfection/Outfall <br /> <br />Fonowing 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 following allocation is for disinfection/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 tre~tment processes. The <br />three subcomp~nents used to allocate biosolids treatment, handling, C!J1d 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 st>c ~pdate <br />because, of the differing available capacities and growth percentages associat~d with <br />facilities in the subcomponents. However, in terms of allocating the facility co'mponents to <br />the wastewater parameters, .the methodology is identical- independent of which <br />subcomponent is being considered. <br /> <br />A-24 <br />