Welsh Water has set ambitious targets for reducing greenhouse gas emissions across their entire operation.
To help meet these goals, they are implementing measures that reduce electrical energy consumption at key wastewater treatment sites.
The Activated Sludge Plant is a very effective process for the removal of biodegradable nutrients from wastewater streams, but typically requires high amounts of energy to supply oxygen to the biomass.
It can also be difficult for operators to optimise these process units, due to the highly variable incoming load they receive, and the complex interactions within the plant.
The project reduced aeration energy consumption by more than 25% and was put forward for both the IWA and WWT Innovation awards, which it won. Read more...
Following similar projects undertaken for Northumbrian Water, Yorkshire Water and United Utilities, Perceptive Engineering was commissioned by DCWW to conduct a detailed assessment of process performance at a municipal site in South Wales.
The Perceptive Audit suggested there was a significant potential for energy saving – 17% reduction in aeration energy – without compromising the quality of final treated water. A data-driven, model predictive control scheme was commissioned in 2012. Welsh Water’s engineers installed ammonia probes on the inlet and outlet of the ASP (one probe at each point).
After commissioning, site operators were able to open the controller constraints to fully exploit efficiency gains. Based on the first few months of operations, electrical blower energy has reduced by more than 25%. Ammonia control is more robust than before and the risk of compliance failure is reduced.
The site has seasonal consent limits; the next phase of the project is to adjust ammonia targets closer to the higher winter-time values, which will permit further energy savings. Once this is proven, seasonal selection will be made automatically by the new control scheme.
“We are exploring how we can best control the process during TRIAD periods, when minimum energy consumption is the target. The Perceptive system will help us to do this while staying within compliance limits. We are also going to investigate if we can automatically capture additional energy savings during high tariff periods."
Adam Fairman, Energy Innovation and Programme Manager, DCWW