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Criteria for Prescriptive Design Build Focused on DC Water’s Biosolids Program Objectives and Constraints
Author: Gary Newman, Brown and Caldwell (BC), Perry Schafer (BC), Don Stern (Parsons), Tom Chapman (BC), Eron Jacobson (BC), Edmond Low (BC), Jeff Garber (BC), Salil Kharkar (DC Water) and Duncan Mukira (DC Water)
Preprint, Residuals and Biosolids 2012, March 25-28, 2012, Raleigh, NC
The primary objectives of DC Water’s Biosolids Management Program are to reduce the costs of
solids processing and managing biosolids from the 370-mgd-capacity Blue Plains Advanced
Wastewater Treatment Plant (BPAWTP), and to improve DC Water’s sustainability profile.
Costs will be reduced by largely replacing the current Class B lime stabilization process with a
new Class A anaerobic digestion process that will reduce the quantity of solids hauled to
beneficial use by over 50 percent. Class A biosolids will be achieved through the use of the
Thermal Hydrolysis Process (THP) preceding digestion. DC Water will further benefit through
the recovery of biogas from the digestion process to generate electric power (offset electric
power purchases from the local utility) and produce steam to support the THP. Because the
economic benefits of the program are substantial, there is urgency to implement the program and
begin receiving these benefits. For this and other reasons, the design-build-delivery method was
selected to procure the main processing elements of the program.
This paper expands on the development of design concepts to meet the project objectives and the
incorporation of these concepts within the Request For Proposals (RFPs) for design-build
services. Besides meeting the over-arching program objectives, the new solids processing
elements - called the Main Process Train (MPT) – must be “inserted” into the existing BPAWTP,
resulting in design challenges related to site constraints, site infrastructure constraints (power and
utilities to serve the MPT), the need to interface with the existing plantwide distributed control
system, and incorporation of existing facilities into the MPT. The inclusion of the proprietary
THP process (by Cambi™) posed further constraints.