Simulation and control of sludge blanket height in settling tanks

In order to achieve accurate prediction and effective control of the sludge blanket height (SBH) in real operation, a stable and reliable SBH algorithm was selected based on measured suspended solids (SS) profiles, and then incorporated into a layered and dispersive settling tank model derived from mass balance analysis. The secondary settling tank in COST 624/682 benchmark wastewater treatment plant under storm weather was used for steady-state and dynamic simulations of settling tank operation under two different control strategies, constant return rate and constant return ratio. The later performs were more effectively and steadily in controlling the SBH and underflow SS concentration when large fluctuation of influent hydraulic load occurred, thus reducing the risk of effluent sludge escape.