Skip to main content


Buy Article:

$9.50 plus tax (Refund Policy)

Or sign up for a free trial

The City of Phoenix operates two large WWTPs: the 23rd Avenue WWTP (63 MGD, owned by the City of Phoenix, Arizona), and the 91st Avenue Multi-Cities WWTP (180 MGD, owned by the Sub-Regional Operating Group (SROG) cities of Glendale, Mesa, Phoenix, Scottsdale and Tempe, Arizona). Both facilities employ centrifuges for thickening primary and secondary sludges, mesophilic anaerobic digestion, and centrifuges for dewatering digested sludge. Between the two facilities, roughly 650 wet tons/day of 20% total solids class B biosolids are produced, all of which is land applied locally (mileage from WWTPs is between 26 and 88 miles). No long-term biosolids storage is present at either WWTP. The 20% cake is removed daily from sludge hoppers by a contract hauler.

Except for molybdenum, biosolids from the two Phoenix facilities have consistently stayed well below 503 land application pollutant concentration limits, due in large part to effective industrial pretreatment and local limits efforts. Molybdenum concentration in biosolids has a seasonal variation in Phoenix, with the highest concentrations developing in late summer, linked to the use of molybdenum-containing products in cooling towers. During the summer of 2004, preliminary August biosolids molybdenum concentrations at both facilities (76 mg/kg at 23rd Avenue and 74 mg/kg at 91st Avenue) approached the 503 ceiling limit (75 mg/kg), prompting an intensified effort.

This case study will look at:

The multi-organization coordination efforts that are needed to help reduce the risk of land applying biosolids that do not meet 503 pollutant concentration limits, considering that no long-term biosolids storage is available at the WWTPs.

Coordination with local industries, commercial facilities, chemical suppliers, and chemical manufacturers to initiate pollution prevention measures such as product substitution or product reduction to minimize molybdenum discharges to the sewer system.

The progress to date in reducing future molybdenum concentrations.
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: 2006-01-01

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