Study on Floatation Thickening of Activated Sludge by Sludge Supply after Decompression

Abstract

In the present study, the characteristics of the floatation thickening of activated sludge by the method of sludge supply after decompression of activated sludge were investigated. In the experiment, the process of floatation thickening of activated sludge was observed in the range of absolute pressure P_v = 11 ~71 kPa in the test tank and the range of MLSS=2000, 2500, 3000 and 3500 ppm. And the estimated equations and performance index were suggested. The conclusions are as follows: (1) The absolute pressure range which cloud be complete flotation thickening is P_v=21~51 kPa. (2) The height of supernatant liquor increased (thickness of concentrated sludge decreased) with time progress, dramatically, and closed to the certain constant height (final height of supernatant liquor and final thickness of concentrated sludge). (3) The dimensionless final height of supernatant liquor increases as the P_v is lower and MLSS is bigger. (4) Completion time of thickening is shorter as the P_v is lower and the influence of the MLSS is very small. (5) Inverse number of concentrated phase density (dimensionless final thickness of concentrated sludge per unit MLSS) and completion time of thickening is approximately quadratically increase with P_v / P₀ (P₀: atmospheric pressure). (6) Performance index of floatation thickening by decompression is suggested, the performance is higher as P_v is lower.