Skip to main content


Buy Article:

$9.50 plus tax (Refund Policy)

Or sign up for a free trial

Laboratory and full-scale investigations of recuperative thickening for anaerobic digestion were conducted ) in Spokane, Washington at the Advanced Wastewater Treatment Plant (SAWTP). Recuperative thickening is defined as removing digesting solids from the anaerobic digestion process, thickening the solids and returning the thickened solids to the anaerobic digestion process. Recuperative thickening provides a function analogous to secondary clarification in the activated sludge process. Recuperative thickening allows operation of anaerobic digestion at independent hydraulic and solids residence times.

A simple laboratory test was developed for measuring gas production as a surrogate for methane forming bacteria activity. Laboratory tests showed gas production was not significantly reduced by exposure to 15 minutes of intense aeration. Laboratory tests also showed significant gas production from a mixture of digested and waste activated sludge (WAS) thickened using conventional dissolved air flotation thickening (DAFT). In one test there was immediate gas production and a second test observed no gas production for a 12 to 24 hour period followed by gas production.

A full scale test of recuperative thickening was conducted from September 2000 to May 2001. The following benefits of recuperative thickening were observed:

Use of existing DAFT capacity allowed implementation with essentially no capital cost.

Co-thickening with WAS allowed no increase in thickening labor or power costs.

Polymer use increased for thickening and decreased for dewatering. The net result was a net reduction of polymer requirements by 15-percent with an annual savings of 28,000.

Biosolids production was reduced 22-percent with a resultant annual savings of 85,000.

Recuperative thickening of 25-percent of the digesting solids increased solids retention time in the anaerobic digesters from 15.7 days to 24.0 days.

Anaerobic digestion volatile solids reduction increased from 50-percent to 64-percent.

Recuperative thickening did not affect effluent quality.
No Reference information available - sign in for access.
No Citation information available - sign in for access.
No Supplementary Data.
No Data/Media
No Metrics

Document Type: Research Article

Publication date: 2001-01-01

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