Meeting <1mg/l Total Phosphorus permits on small ASP sites – do we need Tertiary Solids Removal?

Rosemary Barker, Emilie Cope, Jimmy Nguyen, Thomas O’Shea, Denys Wickens, Eddison Ruswa (all Severn Trent Water) and Julie Jeavons (MWH Global)


Under the Water Framework Directive (WFD), Severn Trent Water (STW) are receiving a number of Total Phosphorus (Total P) permits <1mg/l in AMP6, with more in AMP7. Four existing single oxidation sites and one oxibox site (with Population Equivalents <5000) with Total P permits ranging from 0.5 to 0.7 mg/l have already been commissioned. On all these sites the approach has been taken to phase the solution, with the iron coagulant chemical dosing into the ASP being installed first. Performance was then monitored for 3 to 6 months, to ascertain whether Tertiary Solids Removal (TSR) is required to ensure Total P and iron compliance. After reviewing the data it has been agreed on three sites that TSR is not required. On one site further data is required to make the decision, and the results from the final site are borderline due to sporadic final effluent solids. It has also been discovered that at these lower P levels the normal assumed ratios of Ortho P to Total P no longer apply, meaning obtaining Total P data is essential when making decisions.

Please fill in your details to download the proceedings

For more information about how Aqua Enviro
can help you, contact us...

8 Appleton Court, Calder Park, Wakefield, WF2 7AR, UK

Consultancy and Laboratory services: + 44 (0)1924 242255

Conferences and Training enquiries: +44 (0)1924 257891


  • By submitting this form, you agree that we may use the data you provide to contact you with information related to your request/submission and other relevant Aqua Enviro services. You can unsubscribe from Aqua Enviro marketing emails at any time by clicking the unsubscribe link in the email. To learn more, see our Privacy Policy