Skip to main content


Buy Article:

$9.50 plus tax (Refund Policy)

Or sign up for a free trial

The Sanitation Districts of Los Angeles County (Districts) operate the Valencia Water Reclamation Plant (VWRP) to provide wastewater treatment and disposal services for approximately 170,000 residents in southern California's Santa Clarita Valley. In 2003, the plant was expanded and upgraded for biological nitrogen removal (BNR). Two existing treatment trains were converted from step-feed systems designed for BOD removal to modified Ludzack-Ettinger (MLE) operation. At the same time, three new MLE treatment units were added to accommodate a projected increase in average dry weather flow from 14 to 21.6 MGD. The current NPDES permit allows the VWRP to discharge an effluent containing, on a monthly average basis, 10 mg/L of nitrate plus nitrite nitrogen (NO3-N plus NO2-N). This limit has interim status and may be lowered to 6.8 mg/L in 2009 (also monthly average basis). Achieving the more stringent standard presents significant challenges. At the design flow of 21.6 MGD, the hydraulic retention time in the biological reactors will be a relatively short 6.7 hours. Yet, the plant must be able to treat the nitrogen loading in the influent wastewater in addition to the ammonia nitrogen (NH3-N) in a filtrate stream generated from dewatering anaerobically digested biosolids produced by the VWRP, and by a 6.5-MGD satellite plant. The filtrate NH3-N comprises approximately 20% of the overall nitrogen loading.

In anticipation of a lower effluent NO3-N limit, the Districts initiated studies to identify opportunities for maximizing nitrogen removal within the existing VWRP facilities. The VWRP provides a unique environment for such studies. The original treatment units could be operated in either a MLE or a stepfeed nitrification/denitrification (NDN) mode. In addition, features unique to MLE and step-feed NDN configurations could be combined to create a new hybrid mode of operation. During 2005–06, the Districts tested the nitrogen removal capacity of the MLE, step-feed NDN and hybrid configurations in treatment units that operated side-by-side. In full-scale testing, the hybrid produced an effluent that contained less NO3-N plus NO2-N than the step-feed and MLE configurations. Subsequently online nitrate nitrogen analyzers were installed to characterize and compare hybrid to MLE performance in greater detail. The effluent produced by the hybrid was typically lower in NO3-N by 2 mg/L throughout the day. BioWin was used to model nitrogen removal performance at the VWRP. The model was calibrated against the online nitrate nitrogen analyzer data. The model was then run to project nitrogen removal performance at wintertime wastewater temperatures and at the future 21.6 MGD flow. The effluent NO3-N levels were predicted to be slightly greater than the 6.8 mg NO3-N plus NO2-N future limit. To meet the future limit, the three existing MLE treatment units could be converted to hybrid operation, if necessary, to improve nitrogen removal performance.
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 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.

    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