Skip to main content


Buy Article:

$9.50 plus tax (Refund Policy)

Or sign up for a free trial

The City of Chattanooga operates the Moccasin Bend Wastewater Treatment Plant, which serves as the regional POTW for the entire metropolitan area. The Moccasin Bend plant was recently upgraded to have a full secondary treatment capacity of 140 mgd with an additional 100 mgd of “wet-weather” treatment capacity.

Beginning in the early 1980's, blended biosolids from the plant were dewatered using diaphragm filter presses supplemented with high-solids centrifuges. All dewatered solids were disposed of at a local sanitary landfill, which resulted in wasted volume and high disposal costs. Planning for the recent plant upgrade included an exhaustive evaluation of biosolids handling and disposal options. This led to the selection of a dual process biosolids handling approach. Primary solids are digested using two-stage (thermophilic/mesophilic) anaerobic digestion, and the digested solids are dewatered using high-solids centrifuges. Secondary waste-activated sludge (WAS) is dewatered and dried using vacuum drying filter presses. Both processes produce final sludges which meet Class A standards. Final biosolids disposal is by land application.

In May 2001, the City received bids from two manufacturers of WAS dewatering equipment. An equipment procurement contract for 7,770,281 was issued to U.S. Filter Dewatering Systems for the vacuum drying filter presses. This contract included design of the process installation. CTI provided design for the ancillary systems as well as overall design coordination. In August 2003 bids were received, and a 6,144,000 construction contract was later awarded for the installation of the filter press and support components.

The system was specified to dewater and dry 43 tons (39,000 kg dry wastewater solids weight) per day (based on 24-hour-per-day operation) of WAS with a minimum feed solids content of 1.5 percent dry wastewater solids. Lime and ferric chloride are used for sludge conditioning prior to dewatering. U.S. Filter's bid performance guarantees were a Class A final product with a minimum of 78 percent filter cake total solids content conditioned with a maximum of 20 percent lime (100 percent CaO) and 9 percent ferric chloride (100 percent FeCl3). The installed system consists of the following primary components:

Six 2m × 2m, 110 chamber J-Vap filter presses

Three 9,600,000-BTU/hour gas-powered water heaters (boilers)

Three 5,400,000-BTU/hour evaporative cooling towers

Four 150-HP water-ring vacuum pumps

Four 500-gpm sludge transfer pumps

Six 500-gpm filter press feed pumps

Two 2,000-pound/hour lime slaking systems

It is believed that the Chattanooga installation is the largest vacuum drying filter press biosolids handling system in the world.

The underlying technology of the system, lessons learned from the procurement/installation process, and operational performance of the installed system are described.
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