Smith J A  and Carliell-Marquet C M.
Department of Civil Engineering, University of Birmingham


The digestibility of sewage sludge is affected by a number of factors. Activated sludge that has been dosed with iron (Fe) (to remove phosphorus) does not generate as much biogas when it is mesophilically digested as activated sludge that has not been Fe-dosed. The digestibility comparison of non Fe versus Fedosed sludge was carried out in three ways:

(1) Batch tests of sludge from 12 works

(2) Batch tests of sludge dosed with Fe in the laboratory, and

(3) Bench-scale semi-continuous trials comparing an Fe-dosed sludge with Fe and with the Fe removed (using EDTA) or with phosphorus removed (using NaOH).

All results show a similar biogas reduction of ~12%. The mechanism/s responsible for reduced digestibility are not clear but are probably related to the bioavailability of phosphorus within the digester.


Activated sludge, biogas, chemical phosphorus removal, digestibility, iron-dosing, metal fractions.


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