Unlocking Resource Recovery at the Neuse River RRF with THP


  • Amy Hanna, Michael Bullard - Hazen and Sawyer
  • TJ Lynch, Aaron Brower, Tim Woody - City of Raleigh

The City of Raleigh is proceeding with implementation of the Bioenergy Recovery Program (BRP) at the Neuse River Resource Recovery Facility (NRRRF). The BRP will transition biosolids processing from a combination of Class B liquid stabilization, Class A alkaline stabilization and Class A off-site composting to on-site mesophilic anaerobic digestion (MAD) coupled with thermal hydrolysis pre-treatment (THP) to produce a Class A biosolids product from all its residuals while simultaneously moving toward energy neutrality through recovery of excess biogas generated via anaerobic digestion.

Expected benefits from installation of the THP+MAD process at NRRRF include:

  • Decreased anaerobic digester volume due to higher volumetric loading rates with THP pre-treatment as compared to conventional MAD.

  • Increased volatile solids reduction and biogas production as compared to conventional MAD

  • Decreased dry solids mass for final dewatering coupled with increased dewatered cake solids significantly reduces wet cake mass for ultimate product management

  • Increased marketability of a final residuals product that will meet Class A pathogen reduction requirements and have low odor potential.
  • The envisioned improvements leverage existing thickening and final dewatered infrastructure, but also represent a significant process re-configuration with the THP+MAD infrastructure. Additional unique project elements to be incorporated into the final design of the facility include: (1) FOG pre-pasteurization to maintain Class A pathogen reduction on received waste streams; (2) sidestream treatment for ammonia removal using an ANNAMOX process; and (3) gas cleaning and processing to achieve pipeline quality renewable natural gas.

    Specifically, this presentation will describe the various project elements under design at NRRRF and how they fit into an integrated package supporting the goals and objectives of the Bio energy Recovery Program. A business case evaluation of the estimated capital and net present costs of the proposed alternative in comparison with the status quo alternative and also a competing alternative of MAD and thermal drying to achieve a Class A biosolids product will be presented.

    For more information, please contact the author at ahanna@hazenandsawyer.com.

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