Skip to main content


Buy Article:

$9.50 plus tax (Refund Policy)

Or sign up for a free trial

The Orange County Sanitation District (OCSD) is implementing a Capital Improvements Program that includes upgrading their wastewater treatment Plant No. 1 in Fountain Valley, California to full secondary treatment. The expansion will increase both primary and secondary solids production. OCSD prepared a Long-Range Biosolids Management Plan (LRBMP) to select the most cost-effective methods for treatment and disposal of the wastewater solids. The LRBMP concluded that the waste solids from the primary and secondary treatment processes should continue to be anaerobically digested to produce Class B biosolids, which can be land applied or further processed to Class A biosolids.

The LRBMP also investigated the capacity of the existing anaerobic digestion facilities at Plant No. 1 and concluded that the digestion volume would be adequate for future loading conditions once the new primary and secondary facilities were constructed and placed into operation. However, to maintain the 15-day hydraulic retention time for meeting EPA 40 CFR Part 503 Regulations for Class B biosolids, it would be necessary to thicken the feed solids to the digesters. Preliminary estimates indicated that feed solids solids concentrations would need to be approximately 6 percent dry solids (DS) resulting in the digesters operating at solids concentrations up to about 4 percent DS.

Traditionally in the US, wastewater treatment plants operate with feed solids of 4 percent DS or less and therefore 2 to 2.5 percent DS in the digested biosolids. Digested biosolids at this concentration will tend to have approximated Newtonian fluids very similar to water, making both pumping and mixing relatively easy. However, recent trends towards mechanically and chemically thickened solids (up to 14 percent DS) have highlighted the non-Newtonian nature of the material, a Bingham plastic with a high yield stress and shear thinning properties. In turn this has led to problems with pumping and digester mixing, resulting in undersized pumps, foaming and short circuiting.

The paper discusses the preliminary design engineering study carried out for Plant No. 1. Two novel techniques for testing and using site-specific rheology data to produce hydraulic and pump evaluations are presented, and the use of a scale model and computational fluid dynamics are reviewed for the assessment of digester mixing.
No Reference information available - sign in for access.
No Citation information available - sign in for access.
No Supplementary Data.
No Article Media
No Metrics

Document Type: Research Article

Publication date: 01 January 2006

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