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6. DEVELOPMENT AND EVALUATION OF ALTERNATIVES <br /> <br /> criteria. The resulting exhaust air flow rates for all area and the assumed facility sizes are <br />· s.ummarized in Table 6.2.5-1. <br /> <br /> TABLE 6.2.5-1 <br /> Exhaust Flow Rates by Area <br /> MWMC Facilities Plan, Eugene-Springfield <br /> <br /> Odor Source Unit Size Assumptions Air Total Air Flow Rate <br /> Changes <br /> <br /> Headworks Channels 4 Channels, 5' Wide, and 75' Long 20 (under 2000 CFM <br /> with 4' Average Headspace. vacuum) <br /> <br /> Truck Loadout Bay 50' Long, 20' Wide, and 20' High. 12 4000 CFM <br /> <br /> Primary Clarifier Floc 4 Units,35' Diameter with 2' Average 12 800 CFM <br /> Wells Headspace. <br /> <br /> Primary Clarifier Effluent 4 Units, 135' Outer Diameter and 130' 12 7600 CFM <br /> Launders Inner Diameter with 3' Average <br /> Headspace. <br /> <br /> Primary Sludge Thickener 2 Units, 50' Diameter with 12' 12 5100 CFM <br /> Average Headspace <br /> <br /> Equipment Enclosures Various 2500 CFM <br /> Existing Odor Control Existing Connected Load 18000 CFM <br /> Total Flow Rate 41,000 CFM <br /> CFM = Cubic feet per minute <br /> <br /> The odor control system will be designed to achieve the specified removal efficiency based <br /> on hydrogen sulfide concentration, which is used as the surrogate for total odor. The design <br /> removal efficiencies, based on inlet hydrogen sulfide concentration, are summarized in <br /> Table 6.2.5-2. <br /> <br /> TABLE 6.2.5-2 <br /> Design Removal Efficiencies <br /> MWMC Facilities Plan, Eugene-Springfield <br /> <br /> Inlet H2S Concentration Minimum H2S Removal <br /> Technology (ppm) Efficiency (%) <br /> <br /> Bioscrubber >10 99.0 <br /> <10 95.0 <br /> ppm: parts per million by volume <br /> <br /> Alternative 1--Conventional Open-Space Organic Media Biofilter <br /> This system consists of an above- or partially belowgrade configuration with retaining wall <br /> or soil berm filled with an organic media, such as a mulch or composted yard debris, to <br /> grow sulfur-reducing bacteria. The media allows the cultivation of a fixed-film growth that <br /> consumes the odors as air travels upward through the filter bed and into the atmosphere. <br /> The odorous air is evenly distributed throughout the biofilter by distribution piping located <br /> <br /> MWMC_6.0_REVl 1.DOC 6-17 <br /> <br /> <br />