Project Appreciation and Objectives
High energy costs and carbon/GHG emissions associated with operating aeration plants present a major challenge to the water utilities. The new Ofwat key performance indicators will provide regulators, investors and customers with increased transparency and awareness of company performance in these areas.
The efficiency of aeration plants depends on a range of factors which include the type of process installed, the design of individual plants, and the flexibility of aeration plant control systems. In principle, the oxygen transfer rate, fundamental to aeration efficiency in aeration plants, improves with decreasing bubble size but the equipment used to produce fine and ultra-fine (micro) bubbles is likely to have a greater fouling tendency which may limit potential aeration efficiency improvements.
Building on the outputs of WRc's Portfolio study 'CP406 Managing Aeration Plants to Reduce Energy Costs and Carbon Emissions', this project will further develop and enhance the aeration efficiency and cost evaluation tool to allow accurate estimation of aeration efficiency of installed systems and demonstrate how it can be used to achieve cost savings. The package will be broadened to assess diffuser fouling in aeration tanks from changes to bubble size distributions.
Business Benefits to Clients
- Increased aeration plant efficiency across the organisation through use of the aeration efficiency and cost evaluation tool.
- A substantial, sustainable reduction in energy and costs associated with aeration plant operation.
- Quantification of expected energy/carbon savings for novel aeration processes.
- Develop a methodology for quantifying the theoretical limit to aeration efficiency of individual aerators for aeration tanks fitted with tapered aeration and surface aerators using thermodynamic benchmarking.
- Demonstrate the enhanced software tool at one activated sludge plant per contributor to familiarise participants with use of the tool and identify potential efficiency savings.
- Assess techniques for acoustic measurement of bubble size distributions, through practical testing at WRc's test facility, to determine their potential use to assess diffuser fouling.
- Update existing software tool with the capability to assess advanced aeration plant, e.g. Gravitox (UU), Hybacs, Sorubin aerator, SuperOxBox, Zimmerman fluidic oscillator.
Project Output and Implementation
An aeration efficiency and cost evaluation tool incorporating aeration efficiency benchmarking and an assessment of claimed advances for aeration equipment to support aeration plant efficiency and energy saving initiatives. Provision of guidelines to enable process optimisation teams to understand how the data requirements and benchmarking methodology in the Tool support the delivery of aeration plant efficiency, energy savings and reduction in GHG emissions.
Related WRc Work
- CP406 Managing Aeration Plants to Reduce Energy Costs and Carbon Emissions, 2011.
- Pumps - Optimisation and Replacement, CP348a, 2011.
- Comparing Energy Efficiency: Where Are We Good?, CP310, 2007-ongoing.