Evaluation of plant-wide WWTP control strategies including the effects of filamentous bulking sludge.

The main objective of this paper is to evaluate the effect of filamentous bulking sludge on the predicted performance of simulated plant-wide WWTP control strategies. First, as a reference case, several control strategies are implemented, simulated and evaluated using the IWA Benchmark Simulation Model No. 2 (BSM2). In a second series of simulations the parameters of the secondary settler model in the BSM2 are automatically changed on the basis of an on-line calculated risk of filamentous bulking, in order to mimic the effect of growth of filamentous bacteria in the plant. The results are presented using multivariate analysis. Including the effects of filamentous bulking in the simulation model gives a-more realistic-deterioration of the plant performance during periods when the conditions for development of filamentous bulking sludge are favourable: compared to the reference case where bulking effects are not considered. Thus, there is a decrease of the overall settling velocity, an accumulation of the total suspended solids (TSS) in the middle layers of the settler with a consequent reduction of their degree of compaction in the bottom. As a consequence there is a lower TSS concentration in both return and waste flow, less biomass in the bioreactors and a reduction of the TSS removal efficiency. The control alternatives using a TSS controller substantially increase the food to microorganisms (F/M) ratio in the bioreactor, thereby reducing both risk and effects of bulking sludge. The effects of ammonium (NH(4)(+)), nitrate (NO(3)(-)) and reject water control strategies are rather poor when it comes to handling solids separation problems.

[1]  Alejandro Rivas,et al.  Model-based optimisation of Wastewater Treatment Plants design , 2008, Environ. Model. Softw..

[2]  Ingmar Nopens,et al.  Wastewater treatment models in teaching and training: the mismatch between education and requirements for jobs. , 2009, Water science and technology : a journal of the International Association on Water Pollution Research.

[3]  J Alex,et al.  Modelling of aeration systems at wastewater treatment plants. , 2006, Water science and technology : a journal of the International Association on Water Pollution Research.

[4]  P A Vanrolleghem,et al.  Benchmark simulation model no 2: general protocol and exploratory case studies. , 2007, Water science and technology : a journal of the International Association on Water Pollution Research.

[5]  U Jeppsson,et al.  Benchmark simulation Model no 2 in Matlab-simulink: towards plant-wide WWTP control strategy evaluation. , 2006, Water science and technology : a journal of the International Association on Water Pollution Research.

[6]  U Jeppsson,et al.  Impact of reactive settler models on simulated WWTP performance. , 2006, Water science and technology : a journal of the International Association on Water Pollution Research.

[7]  Sylvie Gillot,et al.  The COST Simulation Benchmark: Description and Simulator Manual , 2001 .

[8]  J Colprim,et al.  A hybrid supervisory system to support WWTP operation: implementation and validation. , 2002, Water science and technology : a journal of the International Association on Water Pollution Research.

[9]  Ulf Jeppsson,et al.  Risk assessment modelling of microbiology-related solids separation problems in activated sludge systems , 2008, Environ. Model. Softw..

[10]  Mogens Henze,et al.  Activated sludge models ASM1, ASM2, ASM2d and ASM3 , 2015 .

[11]  H Siegrist,et al.  Modelling seasonal dynamics of "Microthrix parvicella". , 2006, Water science and technology : a journal of the International Association on Water Pollution Research.

[12]  W. Gujer,et al.  Activated sludge model No. 3 , 1995 .

[13]  K V Gernaey,et al.  Application of multivariable statistical techniques in plant-wide WWTP control strategies analysis. , 2007, Water science and technology : a journal of the International Association on Water Pollution Research.

[14]  I. Takács.  A dynamic model of the clarification-thickening process , 1991 .

[15]  J. B. Copp,et al.  Benchmark Simulation Model No 2: finalisation of plant layout and default control strategy. , 2010, Water science and technology : a journal of the International Association on Water Pollution Research.

[16]  Hansruedi Siegrist,et al.  Reduction of biomass decay rate under anoxic and anaerobic conditions , 1999 .

[17]  Willi Gujer,et al.  Development of a mathematical model for “aerobic bulking” , 1994 .

[18]  S Winkler,et al.  Progress in sensor technology--progress in process control? Part 1: sensor property investigation and classification. , 2003, Water science and technology : a journal of the International Association on Water Pollution Research.

[19]  Ignasi Rodríguez-Roda,et al.  Systematic Procedure to Handle Critical Decisions during the Conceptual Design of Activated Sludge Plants , 2007 .