Energy & Carbon Saving via Optimisation of Activated Sludge Plants

Sloper M. 1,. and Jolly M.2, Davies, S.2.
1Black & Veatch, ,2Aqua Enviro



Thames Water have recognised that it is possible to reduce energy and carbon usage on activated sludge plants throughout the Thames region and have set up a capital programme through Eight2O. The programme looks at some of Thames Water’s 26 largest activated sludge plants with the ambition of saving 55 GW of electricity during the AMP6 period.

The programme of works involves initial site investigations with process analysis of the flow and load to the plant, the returned activated sludge rate, on site chemical usage and operation of the aeration system including blower control, dissolved oxygen set points and header pressure.

Once the optimum process parameters have been identified, minor works are programmed to be carried out to ensure the works was set to the optimum operating point. The energy and chemical usage before and after the changes are to be monitored and the savings in energy and chemical usage recorded. The programme started in 2016, details of potential energy and carbon saving are reported in this paper.


Activated sludge plant, carbon, energy saving, optimisation.


Thames Water have set up the Energy Efficiency and Carbon (EE&C) Aeration capital investment programme to undertake projects to reduce energy and carbon usage on activated sludge plants throughout the Thames region.  This programme is being delivered by Eight2O and intends to deliver Thames Water’s performance commitments to OFWAT, which are an energy saving of 55 GW and a carbon reduction of 34% during the AMP6 period.  These projects also have a secondary benefit of improving the process resilience of the activated sludge plant and the final effluent compliance of the site.

The programme consists of 26 sites, which contain some of Thames Water’s largest activated sludge plants.  These sites were chosen based on an energy inefficiency selection criteria that considered the total site energy usage, population equivalent and treated flow.  As best practice and a baseline comparison, an energy efficient site is expected to achieve an annual usage of 15 – 20 kWhr/PE.  Table 1 below shows the nine sites being delivered by Aqua Enviro as part of phase 2 of the programme.

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