Project Appreciation and Objectives
The majority of activated sludge process (ASP) control systems use feedback control, with dissolved oxygen (DO) and/or ammonia sensors providing the measured value input. When correctly set up these systems can provide stable, reliable and economical aeration. Further energy efficiency savings would be possible if a reliable feed forward load sensor were available to improve the response time to changes in incoming load. Existing sensors for organic load are dip probes; whilst these operate reliably on final effluents they will not achieve this in the more demanding application of settled sewage.
This lack of a reliable feed-forward load sensor currently limits the control options available to designers, and this will become more important as companies seek to further optimise energy use. Additionally the ability to better control the treatment process to deal with fluctuating loads would enhance OPA scores and encourage further consideration by the regulator of more dynamic consenting.
WRc has developed a non-contact optical sensing system that is not susceptible to fouling. This project provides the opportunity for wastewater operators to take a stake in its development to ensure that the delivered system fully matches their needs. Their commitment will also provide a prospective manufacturer with sufficient confidence to invest in its production, something which is currently a barrier to progress for this technology.
Benefits to Clients
- Energy cost savings on ASP plants, estimated as £5000/year and £40,000/year on medium and large plants respectively.
- Improved plant control reducing risk of compliance failures.
- Important building block in catchment management for smart rather than capital-intensive solutions.
- Development and testing of a laboratory prototype which provides acceptable performance on sewage samples.
- Design and construction of a pre-production prototype.
- Site trials of the prototype at two test sites, 6 months of site testing in all.
- A fully tested instrument capable of reliable, affordable, and effective measurement of organic load of settled and crude sewage for the ASP control and inlet monitoring applications.
- Fully defined engineering specification for production and engagement of a manufacturer to produce further instruments under licence and agreed commercial terms.
Related WRc Work
- EC Loadmon project, 1998-2002, technical lead and coordination by WRc.
- Non-contact final effluent monitor development 2004-5.
- Energy Bench-marking 2006, ongoing.
- Non-intrusive load monitor development, 2008 ongoing.