Proceedings

United Utilities (UU) produce approximately 190,000 tDS of sewage sludge pa as a result of wastewater treatment processes. A significant proportion of this sludge is processed at Anaerobic digestion facilities across UU’s catchment areas.

To meet energy generation targets whilst reducing risk of sludge backlogs, it was essential that UU developed a strong resilience position through prioritisation of asset maintenance budgets for AMP7.

Aqua Enviro undertook lithium tracer testing across 12 of UU’s sites, which were carefully selected based upon highest risk of sludge bottlenecks. By assessing current mixing efficiency, active volume, proportion of dead zones and short-circuiting, it was possible to identify where investment must be prioritised to maximise generation and ensure a consistent route for sludge within each catchment area. This study presents the findings of the tracer studies and explains how these were utilised to inform UU’s AMP7 biosolids resilience strategy.