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8 DEVELOPME~f AND EVALLIATIO~I OF ALTERNA'~VE~ <br /> <br />in Table 6.3-1. These detention time guidelines are commonly used by the Oregon DEQ for <br />contact time criteria. <br /> <br />TABLE 6.3-1 <br />Guidelines for Chlorine Disinfection Design <br />MWMC Fac~lrties Plan, Eugene-Springfield <br /> <br /> Projected 2025 Flow Required Detention Required Chlorine <br /> Condition (mgd) Time ( rain} Dosage <br /> <br />ADWF 59 60 3,5 <br />PDWWF 227 20 3,5 <br />*PHWWF 277 15 3.5 (SE), 7,0 (PE) <br /> <br />Provide a 1 mg/L residual in all cases <br /> <br />Flows must be as measured at the disinfection facility <br /> <br />30 day chemical storage at average annual <br /> <br />14 day chemical storage at maximum month <br /> <br />6 day chemical storage at maximum week <br /> <br />Additional criteria used as a basis for sizing and selecting UV d~s~fecdon alternatives are <br />shown ~-t Table 6.3-2. <br /> <br />TABLE 6.3-2 <br />Design Critena for UV DisInfection <br />MWMC Facilities Plan, Eugene-Springfield <br /> <br /> iVlinimum Maximum TSS <br /> Condition Transmittance (%) (rog/L) <br />Secondary Effluent 65 20 <br />Primary Effluent 25 45 <br /> <br />Monthly geometric mean E, co/~ count = 126 MPN/IO0 mL <br /> <br />Maximum single sample E. coil count = 406 MPN/100 mL <br /> <br />Alternative 1: Hypochlorite Disinfection of Secondary and Primary Effluent <br />This alternative involves conversion of both the SE and PE flow streams to sodium <br />hypochlorite disLrffection. The sodium hypochlorite solution strength will be 12.5 percent; <br />sodium bisulfite will be 38 percent. This alternative will require installation o£ rite following <br />equipment: <br /> <br />· Three (3) 20,000-gallon horizontalbulk storage tanks for hypochlorite <br /> <br />MWMC_60_REV11 DOC 6-23 <br /> <br /> <br />