EFFECT OF MEASUREMENT ERROR OF SETTLING VELOCITY ON SECONDARY SEDIMENTATION TANK DESIGN

A simple nonlinear regression technique is presented for obtaining the equation of settling velocity as a function of sludge concentration based on the data obtained from multiple batch settling tests. The equation obtained is incorporated into a computer procedure for sizing a secondary sedimentation tank. The proposed procedure is used for assessing the effect of measurement error associated with the settling velocity on the design of a secondary sedimentation tank through Monte Carlo simulation. The results obtained indicate that the mean of absolute percentage error associated with the limiting solids flux capacity of a secondary sedimentation tank varies almost linearly with the level of measurement error associated with the settling velocity. It is also observed that the required clarification area can be estimated more accurately than the required thickening area. It is further noted that a better estimate of thickening area can be obtained when the desired underflow solids concentration is chosen at a lower level.