On-Line Control of Polymer Addition to Prevent Massive Sludge Washout

An experimental method that quantifies the effect of polymer dosing on sludge settling characteristics is proposed. This method consists of recording batch settling curves at a grid of sludge and polymer concentrations. The effect of the polymer was found to depend on the mixing time between the dosing of the polymer and the start of the batch sedimentation. The recorded effects could be successfully implemented in a 1D dynamic settler model. From the literature it was concluded that keeping the sludge blanket below a certain critical height is an effective way of controlling the effluent suspended solids. From a model-based analysis this strategy appeared to be sound. Different control strategies using, respectively, the sludge blanket height [feedback (FB)], the hydraulic loading [feedforward (FF)], the solids loading (FF), or the sludge volume loading (FF) were tested for their ability to keep the sludge blanket below the critical height. The control strategy based on the hydraulic loading was the leas...

[1]  G. Daigger.  Development of refined clarifier operating diagrams using an updated settling characteristics database , 1995 .

[2]  J. R. Müller,et al.  Wastewater flow management to maximise the capacity of sewage treatment plants , 1998 .

[3]  A. E. Greenberg,et al.  Standard methods for the examination of water and wastewater : supplement to the sixteenth edition , 1988 .

[4]  Doug J. Lumley,et al.  Investigations of Secondary Settling at a Large Treatment Plant , 1988 .

[5]  Ulf Jeppsson,et al.  Modelling Aspects of Wastewater Treatment Processes , 1996 .

[6]  Gustaf Olsson,et al.  Knowledge based diagnosis of solids-liquid separation problems , 1996 .

[7]  Size and density of flocculated sludge flocs , 1997 .

[8]  Gustaf Olsson,et al.  Establishing Cause-Effect Relationships in Activated Sludge Plants - what Can Be Controlled , 1994 .

[9]  Peter Krebs.  Success and shortcomings of clarifier modelling , 1995 .

[10]  Frank Pacard,et al.  New insights in dynamic modeling of a secondary settler-I. Flux theory and steady-states analysis , 1997 .

[11]  Wei-Ling Chiang,et al.  Effluent suspended solid control of activated sludge process by fuzzy control approach , 1996 .

[12]  G. Olsson.  State of the Art in Sewage Treatment Plant Control , 1976 .

[13]  Andrea Deininger.  INFLUENCE OF COMBINED SEWAGE INFLUENT ON SECONDARY CLARIFIERS OF ACTIVATED SLUDGE PLANTS , 1994 .

[14]  Willy Verstraete,et al.  Design and verification of a model secondary clarifier for activated sludge , 1996 .

[15]  Short-term effects of additives on sludge sedimentation characteristics , 1999 .

[16]  Peter Krebs,et al.  Inlet-structure design for final clarifiers , 1995 .

[17]  Henrik Aspegren,et al.  Real time control for minimizing effluent concentrations during storm water events , 1996 .

[18]  D. Jenkins,et al.  Polymer addition as a solution to Nocardia foaming problems , 1997 .

[19]  A. C. Van Haandel.  Activated sludge settling. II: Settling theory and application to design and optimisation , 1992 .

[20]  Mogens Henze,et al.  Rising sludge in secondary settlers due to denitrification , 1993 .

[21]  Marinus K. Nielsen,et al.  Combined control of sewer and treatment plant during rainstorm , 1996 .

[22]  W. Verstraete,et al.  On-line quantification of settling properties with in-sensor-experiments in an automated settlometer , 1996 .