Optimal aeration control in a nitrifying activated sludge process

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• 作者：L. Å ; mand^a ; ^b ; ^{linda.amand@ivl.se} ; B. Carlsson^b
• 关键词：Activated sludge process ; Aeration control ; Optimisation ; Supervisory ammonium control
• 刊名：Water Research
• 出版年：2012
• 期刊代码：57_00431354
• 类别：civ
• 出版时间：1 May, 2012
• 卷：46
• 期：7
• 页码：2101-2110
• 文件大小：671 K

摘要

An important tool to minimise energy consumption in activated sludge processes is to control the aeration system. Aeration is a costly process and the dissolved oxygen level will determine the efficiency of the operation as well as the treatment聽results. What aeration control should achieve is closely linked to how the effluent criteria are defined. This paper explores how the aeration process聽should be controlled to meet the effluent discharge limits in an energy efficient manner in countries where the effluent nitrogen criterion is defined as average values over long time frames, such as months or years. Simulations have been performed using a simplified Benchmark Simulation Model No. 1 to investigate the effect of different levels of suppressing the variations of the effluent ammonium concentration. Optimisation is performed where the manipulated variable for aeration聽(the oxygen transfer coefficient, K_La) is minimised with the constraint that the average daily flow-proportional ammonium concentration in the effluent should reach a desired level.聽The optimisation results are compared with聽constant dissolved oxygen concentrations and supervisory ammonium control with different controller settings.聽The results demonstrate and explain how and why energy consumption can be optimised by tolerating the ammonium concentration to vary around a given average value. In these simulations, the optimal oxygen peak-to-peak amplitude range between 0.7 and 1.8 mg/l depending on the influent variation and ammonium level in the effluent. These variations can be achieved with a slow ammonium feedback controller.聽The air flow requirements聽can be reduced by 1-4%compared to constant dissolved oxygen set-points. Optimal control of aeration requires up to 14%less聽energy聽than needed for fast feedback control of effluent ammonium.