Eugene/Springfield Water Pollution Control Facility 1984-1991

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Page 30 Section D: PLANT OPERATIONS is 12,260, the maximum weekly average is 18,390, and the maximum daily total pounds of TSS discharged is 24,520. Plant Effluent TSS Concentrations/Novern- ber through April (Limits: 30 mg/L monthly, 45 mg/L weekly): Peak Peak Dally Monthly Weekly Average Average Average 1985 6 mg/L 8 mg/L 12 mg/L 1986 10 mg/L 18 mg/L 26 mg/L 1987 8 mg/L 12 mg/L 15 mg/L 1988 8 mg/L 12 mg/L 18 mg/L 1989 7 mg/L 9 mg/L 16 mg/L 1990 6 mg/L 10 mg/L 14 mg/L 1991 6 mg/L 7 mg/L 10 rng/L Plant Effluent TSS Pounds Discharged/No- ~ vember through April (Limits: 12,260 lbs. monthly, 18,390 lbs. weekly, 24,520 lbs. daily): Peak Peak Peak Monthly Weekly Daily Average Average Average 1985 4,1211bs 7,6201bs 18,3601bs 1986 11,2801bs 23,0631bs 37,8401bs 1987 4,0401bs 9,0491bs 21,0501bs 1988 5,6301bs 17,2801bs 59,3001bs 1989 4,1001bs 10,3901bs 28,1601bs 1990 3,9901bs 7,7901bs 23,1601bs 1991 2,6701bs 4,6701bs 10,2501bs AVERAGE PERCENT REMOVAL OF BUD The waste di scharge permit requires monitoring of the average percentage removal of Biological Oxygen Demand (BOD). The calculation is per- formed at least three times a week. Secondary treatment facilities that use the activated sludge process are normally designed to achieve greater than 90 percent removal of BOD. The plant has averaged 94 percent removal of BOD. AVERAGE PERCENT REMOVAL of TSS The waste discharge permit also requires monitor- ing of the average percentage removal of Total Suspended Solids (TSS). The calculation is per- formed at least three times a week. Secondary treatmentfacilitiesosing the activated sludge pro- cessare normally designed to achieve greater than 90percentremoval ofTSS. Theplanthasaveraged 95 percent removal of TSS. CHLORINE USED The waste discharge permit requires the plant to maintain daily reports of the amounts of chlorine used. Chlorination is used exclusively to disinfect plant effluent and is the last treatment process before the effluent is discharged. The average quan- tity of chlorine used is 480 pounds a day. EFFLUENT CHLORINE RESIDUAL Monitoring chlorine residual is required daily and is taken on one grab sample a day. The discharge permit does not allow the plant to discharge any chlorine residual from May through October. Us- ing sulfur dioxide for dechlorination has success- fu11y maintained zero chlorine residuals for those months. Effluent chlorine residual is allowed during No- vemberthrough April. The waste dischargepermit does not specifically limit the amount of chlorine residual in the plant effluent during this period. However, to keep chemical costs down, effluent chlorine residuals are closely monitored during these periods to ensure that only those residuals exist that are necessary to carry out adequate disinfection. The average effluent chlorine re- sidual to accomplish adequate disinfection has been 0.5 rng/L.