Skip to main content


The full text article is not available for purchase.

The publisher only permits individual articles to be downloaded by subscribers.

or click here to sign up for a free trial


Though commonly associated with stable and robust BOD removal and nitrification, oxidation ditch systems are now being designed and operated to achieve nitrogen removal through separate anoxic zones and simultaneous nitrification-denitrification. In some cases, operating data suggest that some degree of unintentional biological phosphorus removal (Bio-P) could be occurring in these processes, but it is typically difficult to assess. The operating sequence of the proprietary Phases Isolation Ditch (PID) process, which can be designed for efficient total nitrogen removal and eliminates the need for secondary clarifiers, was modified at a 0.6 MGD treatment plant to include an anaerobic fill phase in hopes of achieving some degree of Bio-P. The objective of this investigation was to evaluate polyphosphate accumulating organism (PAO) activity in the PID process. This work was done to determine whether PAO activity could be responsible for the relatively efficient and otherwise unexplainable P removal currently being observed at this plant. Using phosphorus release rate measurements and comparing these values to that previously published in a survey of Bio-P plants, it is clear that this facility is successfully achieving some degree of biological phosphorus. However, influent Al and Fe loading is significant and could be responsible for some degree of the observed P removal.

Document Type: Research Article


Publication date: January 1, 2007

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 These proceedings are not peer reviewed.

    WEF Members: Sign in (right panel) with your IngentaConnect user name and password to receive complimentary access.
  • Subscribe to this Title
  • Membership Information
  • About WEF Proceedings
  • WEFTEC Conference Information
  • Ingenta Connect is not responsible for the content or availability of external websites

Access Key

Free Content
Free content
New Content
New content
Open Access Content
Open access content
Subscribed Content
Subscribed content
Free Trial 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