Liverpool WWTW SBR Carbonaceous Trial

Akinola, O.1, Black, J.1, Sherwood, A1. and Hornsby J1.
1United Utilities, UK



In January 2017, a Trial commenced on the Sequencing Batch Reactor (SBR) Plant at Liverpool WwTW. The 16-basin SBR Plant is normally operated in ‘nitrification mode’. Annual aeration savings of approximately £300k were previously estimated if carbonaceous operation is adopted. The Trial was carried out on 2 No. basins with a target aerobic sludge age of 4 days. The key objectives of the Trial were to assess process risk, OPEX benefits, and the likely impact on the sludge stream.  Process modelling using BioWin was carried out in advance to provide guidance on key operating parameters. Liaison with site operators and managers was necessary throughout the Trial to implement changes and monitor performance. Key Performance Indicators (KPIs) included: effluent quality (particularly ‘hard’ COD), sludge age, settleability, microscopy and energy consumption. The Trial results demonstrated effluent quality consistently below consented limits and 37% aeration energy reduction.


Basin, Carbonaceous, Configuration, Energy, MLSS, Operation, SAS, SBR


The 16-basin SBR Plant at Liverpool WwTW was designed to operate in ‘nitrification mode’, due to historical issues with ‘hard COD’ received at the Works and the need to ensure adequate treatability. There is currently no ammonia consent at Liverpool WwTW. It has been previously estimated that by adopting carbonaceous operation (i.e. not removing ammonia), annual aeration savings of approximately £300k could be achieved.

The process of transitioning from ‘nitrification mode’ to ‘carbonaceous mode’ requires some reconfiguration of the process and could entail some process compliance risk. Therefore, it was necessary to undertake a Trial to further understand the risks, limitations and reconfiguration needed.

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