Carmel in NLC's "Best Practices"

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Carmel Included in National League of Cities "Best Practices"

Date: March 7, 2008

Carmel, IN - Carmel was recently notified that its Wastewater Treatment process will be added to the “Best Practices” database for the National League of Cities (NLC). This database provides the 18,000 members of the NLC with information on a wide range of issues.

Carmel had previously submitted an entry called “A High Tech Approach to Wastewater Treatment” to the NLC’s Award of Municipal Excellence competition. The NLC selected Carmel’s process to highlight in the database from that entry.

Carmel installed the first municipal BioPasteur system in the U. S. to process solid biological waste (sludge) from municipal wastewater. With that process, it produces Class A biosolids which can be blended with soil and other materials to produce a form of topsoil. The BioPasteur system began operating at Carmel’s Wastewater Treatment Facility at 96th Street and Hazel Dell Parkway in October 2005.

Before installing this system, Carmel had to transport its biosolids up to 40 miles away to find acceptable land application sites. Utility Department personnel began exploring options to upgrade the sludge handling process, enhance environmental protection, reduce costs to Carmel for waste treatment and convert a liability into an asset.

Here’s how it’s different from traditional processing:

  • Sludge is stored prior to the BioPasteur process. From the mixing tank the sludge is ground and pumped through a series of heat exchangers.
  • The BioPasteur process heats the sludge to a temperature of 160 degrees F or higher. The sludge is held at the elevated temperature for 30 - 60 minutes. The pasteurization process is followed by anaerobic digestion then dewatered to meet all requirements to produce Class A biosolids.

Benefits include:

  • No impact on other portions of the treatment plant; no operating changes were necessary.
  • Carmel is using existing wastewater treatment facilities that are already paid for.
  • The process produces few odors -- a substantial consideration since the plant is near high quality residential developments and a new parkway.
  • The methane gas produced from anaerobic digestion is utilized within the process to conserve energy, making it a “Green Energy Project.”
  • The potential to generate revenue because there is a market for Class A Biosolids

Carmel continues to grow which will increase the volume of waste to treat. Class A biosolids are expected to save the city approximately $200,000 per year in fuel cost savings, employee labor, equipment maintenance and permitting. Carmel has plans to market the biosolids and generate revenue from this new asset.