Successful Long Term Biosolids Planning: Culmination of a Decade Long Biosolids Master Plan

Abstract

The Elledge Wastewater Treatment Plant (WWTP) Centralized Biosolids Drying Facility is the culmination of the decade long implementation of a comprehensive biosolids management master plan conducted by the City of Winston-Salem in the early 1990's. The master plan provided the roadmap for the biosolids treatment and disposal systems for two wastewater treatment plants, Elledge WWTP and Muddy Creek WWTP, which at the time were dedicated to a liquid land application program. The master plan recommended a phased approach to implementation in which they would first migrate to a Class B cake application program through dewatering improvements at the two plants and then ultimately a Class A program. This allowed the cost of the overall transition to be phased over time as well as for technological advances in Class A systems to develop and for the regulatory framework for biosolids disposal in North Carolina to establish itself. The Elledge WWTP Centralized Biosolids Facility is the largest thermal drying system in the Carolinas at 36 dry metric tonnes per day (dmtpd) (40 dtpd) and was designed as a fully automated centralized biosolids dewatering and drying facility for the two Winston-Salem plants (Figure 1). Implementation of the final phase of the master plan included innovative design approaches including centralization of all biosolids treatment and handling at one facility and the use of three-dimensional (3D) design techniques. The thermal drying system also incorporated sustainable concepts including the use of digester gas to supply nearly 50% of all fuel usage and heat recovery for heating of the existing digesters and building heat. The centralized biosolids treatment facility is in service and has met the long term objectives for Winston-Salem originally conceived during the comprehensive biosolids master plan.