No abstract

No abstract

Winston-Salem/Forsyth County Utilities (Utilities) is constructing a new Biosolids ManagementProject (the Project). The Project includes the addition of a new Andritz triple-pass drum dryer, additional dewatering centrifuges, and digester gas utilization equipment at Utilities' Archie Elledge Wastewater Treatment Plant (WWTP). The new dryer will be fueled, in part, with digester gas. The Project is scheduled for completion in early 2008. Biosolids from Utilities' 30-mgd Archie Elledge WWTP and 21-mgd Muddy Creek WWTP will be processed in the new facilities being constructed in the Project.Both the Archie Elledge and Muddy Creek WWTPs are currently operated by Utilities' public works staff. With the implementation of the Biosolids Management Project, Utilities is seeking to provide the best-value outcome for its rate payers relative to operations and maintenance of these new facilities and marketing of the pelletized fertilizer product. Utilities' management staff considered the option of developing a private operations and maintenance (O&M) contract for one or more of the following biosolids unit processes-dewatering, drying, hauling, disposal, and/or marketing of the Class A biosolids product. To facilitate this decision-making process, the authors worked together to:Conduct a workshop that included Utilities' management, operations, and maintenance staff as well as outside consulting specialists to develop alternative public/private operational approaches and identify the strengths/weaknesses of each approach. Conduct a survey of 13 wastewater utilities across the United States who operate biosolids dryers and market a pelletized product to determine industry experience with a wide variety of operational approaches (i.e., both public sector and private sector operations and product marketing). The survey included a look at how these organizations chose to staff similar facilities and their successes, challenges, lessons learned, and fertilizer end-user coordination. Conduct in-person site visits with key operations, maintenance, and marketing (OM&M) staff at four of these utilities to discuss, in more detail, their experience in managing similar projects. Develop an OM&M plan for Utilities' for implementing an effective OM&M Program for the Biosolids Management Project.

In the mid-1990s, the Winston-Salem/Forsyth County Utility Commission put forth an effort to lower long-term operational costs associated with handling of biosolids at the Archie Elledge Wastewater Treatment Plant. Increases in operational costs were eminent due to the loss of available land application sites for their existing land application program. The result was the design and construction of a Biosolids Dewatering Facility that includes chemical handling, centrifuge dewatering, short-term dewatered solids storage and truck loading. One of the key goals during the design and construction of the facility was to reduce or eliminate the need for operator involvement during dewatering and truck loading procedures through automation, in order to reduce operational costs. This paper will present a brief overview of the biosolids dewatering and handling facility, as well as, a more detailed description of the steps taken during design of the SCADA system to automate the handling of the wastewater biosolids from the effluent of the digesters to placement in trucks or a short term storage area. Design considerations for reducing operator involvement during the handling of wastewater biosolids include remote and automated operation of centrifuges (startup, shutdown, and monitoring), automated batching of chemicals, and automated truck positioning and loading. The biosolids handling facility has been designed to allow trucks to enter the facility, load dewatered biosolids and leave the facility without operator involvement. The responsibilities of the truck drivers for loading of the biosolids were reduced to the simple push of a button. The automated handling facility verifies proper position of the truck, loads the truck with dewatered biosolids, and stops the loading procedure when the truck is full. Dual 16th Annual Residuals and Biosolids Management Conference

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.