3.2. Analysis of effluent water quality
The effluent water quality was also analyzed for various average daily inflow conditions and activated-sludge
return rates. The return rate and average daily inflow were varied from 45% to 100% and from the existing
condition of 500 m3/hr to 3,000 m3/hr, respectively. The changes in the effluent water quality in terms of SCAT
were obtained as Table 2.
As a result, if the average daily inflow was increased to 1,000 m3/hr, the minimum activated-sludge return rate
that will satisfy the effluent water quality standard of BOD 0.02 kg/m3 was found to be 80%. If the average daily
inflow was increased to 2,840 m3/hr, the return rate was needed to be increased to 100% to meet the effluent water
quality standard. Therefore, expansion of the aeration tank is required if the average daily inflow is greater than
2,840 m3/hr.