Reinventing A Biosolids Management Program and Unlocking Resource Recovery with Thermal Hydrolysis


  • C M. Bullard, Amy Hanna - Hazen & Sawyer
  • Greg Knight and Kent Lackey - Black and Veatch
  • Perry Schaefer, Brenan Buckley - Brown & Caldwell
  • T. J. Lynch, Aaron Brower - City of Raleigh

An overview of the site plan.

A rendering of the new residuals handling complex as currently conceptualized.

The pre-conditioning building upper level will include a control room and dewatering equipment.

The lower level will include polymer storage and sludge pumping.

Existing cake storage bins will be repurposed as part of the new THP feeding system.

Phase 1 facilities include two digesters coupled with a single control building.

The City of Raleigh operates the Neuse River Resource Recovery Facility (NRRRF), a 75 MGD capacity advanced nutrient removal treatment facility, which serves most of the municipalities located in the eastern half of Wake County, North Carolina in the rapidly growing Research Triangle Park metropolitan area. The treatment facility includes primary and advanced secondary treatment coupled with tertiary filtration to produce a high-quality effluent with typical total nitrogen concentrations less than 3.0 mg TN/L suitable for direct discharge to the Neuse River or for utilization as a high quality reuse water through a growing reuse program. Residuals generated during the treatment process are currently managed by the City in a variety of outlet streams, including:

• Alkaline Stabilization to Class A and marketing as RaleighPlus
• Off-Site Contract Composting of dewatered unstabilized cake
• Off-Site Class B Liquid Land Application of aerobically-stabilized residuals
• On-Site Class B Liquid Land Application of aerobically-stabilized residuals

The City has had a long term interest in environmental stewardship and resource recovery and has been a long-term participant in the National Biosolids Partnership’s Environmental Management Program as a Platinum Certified Member since December 2006. As a part of their NBP-EMS program the City had conducted a residual management masterplan in 2008 with a subsequent update in 2013. The 2008 masterplan evaluated a number of management technologies and recommended upgrading the management program to include anaerobic digestion and thermal drying to produce a Class A product stream. However, economic conditions immediately following completion of the 2008 plan resulted in a delay of implementation and created a need to update the masterplan in 2013 to affirm, or change, decisions developed in the 2008 plan.

While the 2008 masterplan considered thermal hydrolysis pretreatment (THP) as an emerging technology for biosolids management, the 2013 masterplan update acknowledged the continued development and commercialization of the THP process over the intervening five years and recommended that the anaerobic digestion process be coupled with THP to produce a Class A product. Following the 2013 update the City of Raleigh retained an engineering team to develop the recommended masterplan concept into a Preliminary Engineering Report (PER) with a plan to move the project into detailed design, construction, and ultimately into commissioning.

This paper and presentation will present the approach to and results of the concept development advanced through the preliminary engineering report phase of the work. The paper will describe the facilities envisioned for the City of Raleigh’s BioEnergy Recovery Program (BERP) to be constructed on the Neuse River RRF campus.

For more information, please contact the author at

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Horizons Fall 2017 (pdf)

Horizons showcases significant water, wastewater, reuse, and stormwater projects and innovations that help our clients to achieve their goals, and can help you achieve yours. Articles are written by top engineers and process group leaders, demonstrating and explaining the beneficial application of a variety of technologies and tools.

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