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Riechers Spence & Associates Job #: 21 02 049.0 <br /> Consulting Civil Engineers Date: 10/21/02 <br /> 13. Estimate effluent BOD loading <br /> BODe = sBODe + (1 4 gOD IO1gTSSS) (TSS, g/m3) _ <br /> = 15 g/m3 + (0.704)(0.85)(50 g/m3) = 44.92 mg/I <br /> Due to the high sBOD influent loading the effluent sBODe is estimated at 15 <br /> g/m3 and the TSS concentration is estimated at 50 g/m3 (the secondary <br /> clarifier will be designed to meet TSS concentrations below 30mg/1). <br /> Process Control <br /> To maintain high levels of treatment performance with the activated sludge <br /> process under a range of operating conditions, special attention must be <br /> given to process control. It is essential that the dissolved oxygen level be <br /> maintained at the desired level, thus a dissolved oxygen probe is installed in <br /> the system to control the blower operation. The amount of return activated <br /> sludge (RAS) and the amount of waste activated sludge (WAS) is controlled <br /> by the operator. When the sludge level in the reactor reaches the maximum <br /> level as determined by a 30 minute settling test (performed by placing the <br /> mixed liquor in a 11 cone to determine the sludge volume in ml/I after 30 <br /> minutes of settling), the operator is wasting the excess sludge by pumping to <br /> a sludge thickening tank for dewatering. If sludge levels are below the <br /> minimum as determined by the 30-minute settling test, the operator will add <br /> nutrients to enhance the biomass volume. <br /> 21 <br />