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This paper presents a simulation study with the scope to optimise the plant design and operation strategy of 2-reactors alternating activated sludge processes with only flow schedule and aeration on/off as control inputs. The methodology is to simulate the application of receding horizon optimal control (RHOC) to a range of different plant designs within this class of systems and select the combination of design and operation strategy with the best performance. Subsequently a simple feedback controller is designed that closely imitates the optimal operation strategy. Starting-point is the plant layout with maximal degree of freedom within the above-mentioned class (Fig. 1), which is commercially available under the name BIODENITRO(TM). The simulation results indicate that in the optimal combination of plant design and operation strategy the performance in terms of nitrogen removal improves significantly as compared to current practice, especially if a shorter cycle length is used. In the optimal process design the two reactors are placed in series, the first reactor is about four times as large as the second one. The possibilities of feeding influent to reactor 2 and withdrawing effluent from reactor are redundant. A conceptually simple feedback controller (OSCAR, operating a series connection of two alternating reactors) is presented that straightforwardly implements the improved operation strategy. | This paper presents a simulation study with the scope to optimise the plant design and operation strategy of 2-reactors alternating activated sludge processes with only flow schedule and aeration on/off as control inputs. The methodology is to simulate the application of receding horizon optimal control (RHOC) to a range of different plant designs within this class of systems and select the combination of design and operation strategy with the best performance. Subsequently a simple feedback controller is designed that closely imitates the optimal operation strategy. Starting-point is the plant layout with maximal degree of freedom with the above-mentioned class (Fig. 1), which is commercially available under the name BIODENITRO. The simulation results indicate that in the optimal combination of plant design and operation strategy the performance in terms of nitrogen removal improves significantly as compared to current practice, especially if a shorter cycle length is used. In the optimal process design the two reactors are placed in series, the first reactor is about four times as large as the second one. The possibilities of feeding influent to reactor 2 and withdrawing effluent from reactor 1 are redundant. A conceptually simple feedback controller (OSCAR, operating a series connection of two alternating reactors) is presented that straightforwardly implements the improved operation strategy. |
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