Skip to main content


Buy Article:

$17.50 plus tax (Refund Policy)

Or sign up for a free trial


Economic drivers have influenced the development of anaerobic digestion in the UK towards treating thicker sludges whilst reducing retention times. At the same time legislation from the European parliament and public perception has put the onus on water companies to provide a better quality product both low in pathogens and with greater stabilisation. The introduction of Treated and Enhanced Treated standards has led water companies to re examine their digester process trains in order to meet the new requirements. United Utilities response to these diverse pressures was to undertake fundamental studies in the anaerobic digestion process, which resulted in the development of the Enzymic Hydrolysis technology. There are now 4 full scale plug flow digestion plants either constructed or under construction incorporating the Enzymic Hydrolysis reactor.

This paper discusses the benefits of converting the anaerobic digestion process to plug flow by looking at the first year of operational data from Bromborough STW. Bromborough STW treats sewage sludge from a 230,000 pe catchment and is the second full scale installation of Enzymic Hydrolysis within United Utilities. The design and build of the plant is detailed and experience gained during construction and commissioning of the plant discussed. The adoption of a standardised and modular plant design has provided a simple and reliable process, which can readily be incorporated into existing plants in a minimum of time. Commissioning of the process is also standardised and reliable startup is achieved in a matter of days.

Data collected from the Enzymic Hydrolysis process and the anaerobic digesters during the first 18 months of operation is discussed and the ability of Enzymic Hydrolysis to produce both Class B and Class A biosolids reviewed. Furthermore the effectiveness of the hydrolysis achieved under plug flow conditions is examined and the implications for volatile solids reduction and increased biogas production assessed. An energy balance for the plug flow plant is presented, and the advantages of a sustainable biological process, operating at mesophilic temperatures and not requiring supplemental heating, chemical addition, heat recovery or inter stage cooling is considered.

Finally the paper briefly reviews upcoming projects and proposes that plug flow Enzymic Hydrolysis Digestion will allow greater digester loading and a better biosolids product than currently possible with completely mixed anaerobic digesters.

Document Type: Research Article


Publication date: 2005-01-01

More about this publication?
  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

    A subscription to the Proceedings of the Water Environment Federation includes access to most papers presented at the annual WEF Technical Exhibition and Conference (WEFTEC) and other conferences held since 2000. Subscription access begins 12 months after the event and is valid for 12 months from month of purchase. A subscription to the Proceedings of the Water Environment Federation is included in Water Environment Federation (WEF) membership.

    WEF Members: Sign in (right panel) with your IngentaConnect user name and password to receive complimentary access. Access begins 12 months after the conference or event
  • Subscribe to this Title
  • Membership Information
  • About WEF Proceedings
  • WEFTEC Conference Information
  • Learn about the many other WEF member benefits and join today
  • Ingenta Connect is not responsible for the content or availability of external websites
  • Access Key
  • Free content
  • Partial Free content
  • New content
  • Open access content
  • Partial Open access content
  • Subscribed content
  • Partial Subscribed content
  • Free trial content
Cookie Policy
Cookie Policy
Ingenta Connect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more