The use of the activated sludge process (ASP) for the nitrification/denitrification of wastewaters is commonplace throughout the UK and many other parts of the industrial world. Associated with this process are significant costs arising from aeration requirements and for selected sites, the need to provide an external carbon source. These costs can constitute up to of 50% of the total running cost of the whole plant and as such, any effort to reduce them could realise significant benefits. This paper investigates the use of real time control (RTC) using online sensors and control algorithms to optimise the operation of the ASP, leading to greater efficiency and sustainability. Trials were undertaken at full scale to assess the benefit of such a system at a 250,000 population equivalent (PE) works on the south coast of the UK, using Activated sludge model No.1 (ASM 1) as a basis for the control system. Initial results indicate that it is possible to significantly reduce both aeration and chemical consumption costs whilst still delivering the required effluent quality. Over the trial period the aeration requirements were consistently reduced by 20% whereas, a reduction in methanol consumption of in excess of 50% was observed.

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