Skip to main content

A Tale of Two Filaments: BNR System Recovery from a Major Process Upset

Buy Article:

$17.50 plus tax (Refund Policy)

Or sign up for a free trial

Organic overloading from an industrial source and a blower malfunction combined to cause a BNR nitrogen removal plant to self-destruct. This is a story about the Glendale WWTP at Lakeland Florida, a 13.7 mgd facility that suffered a major process upset. Unlike other activated sludge plants experiencing organic overloading, this plant resisted conventional recovery efforts. Chlorinating RAS and re-establishing a good dissolved oxygen profile in the oxic zone did not result in system recovery. Quite to the contrary, filaments continued to flourish.

After three weeks of frustration and only transitory successes in improving mixed liquor settleability (SVI), nitrification was lost. Staff had to ask "What are we doing wrong?" The facility should have been well on the road to recovery but it wasn't. A sample of MLSS was sent out for analysis and the report indicated O21N predominated, with Thiothrix I also present. These two organisms, O21N and Thiothrix I, both thrive under septic conditions. Many times, the definition for septic conditions means only a lack of dissolved oxygen. Restoring the DO concentration was not working. After more investigation, the definition of septicity was found to also include high concentrations of acetic acid or volatile fatty acids (VFA). It was found that the VFA concentration in the influent to the activated sludge process was high.

A two-pronged remedy was developed. A nitrate solution was fed to the anoxic zones in the activated sludge basins to use the nitrate oxygen source to consume VFA under anoxic conditions. Reducing the VFA concentration in the anoxic zone could sufficiently lower the aerated zone influent VFA concentrations to allow the conventional floc forming bacteria to out-compete the filaments for food. Chlorination of RAS was continued to kill the accumulated filaments.
No Reference information available - sign in for access.
No Citation information available - sign in for access.
No Supplementary Data.
No Data/Media
No Metrics

Keywords: ANOXIC ZONES; NITRATE REDUCTION; O21N; THIOTHRIX I; VOLATILE FATTY ACIDS

Document Type: Research Article

Publication date: 2007-10-01

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
X
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