Successful Startup, Commissioning, and Operation of a New Regional Biosolids Drying Facility

Objectives 1. Present lessons learned and findings from the startup and commissioning of a new biosolids facility with thickening, dewatering, and drying. 2. Discuss challenges and successes with training an operations team that is transitioning from hauling sludge to a third part compost facility to operating a full biosolids facility with thickening, dewatering, and drying. Status The City of Hickory (City) in Catawba County, North Carolina is currently constructing a new biosolids handling facility. Substantial completion is anticipated to be reached in the first quarter of 2025. Startup and commissioning of equipment is currently underway, and operations and maintenance staff trainings are being completed. The project team is collaborating with the operations team to develop standard operating procedures. Methodology Design The City is currently in a consortium of wastewater utilities that collectively own a regional solids management facility (RSMF) and contract the operations to a third-party. This facility receives solids from the members and produces Class A compost that is marketed and distributed as a fertilizer. A condition assessment in 2019 indicated that the entire facility was past or approaching the end of its useful life. The key recommendation of this effort was to construct new solids handling facilities at the City of Hickory's Henry Fork Wastewater Treatment Facility (HFWWTF). This recommendation was primarily due to the relatively large cost to replace equipment at the RSMF and the difficulty in beneficially using the composted biosolids product. After a technology review, site visits, and a request for proposal process, the City selected low-temperature, indirect drying for the production of Class A Biosolids at a throughput rate of 12 dry tons per day. HFWWTF was reliant on the existing RSMF facility for all sludge management, including thickening and dewatering. Therefore, the new Solids Handling Facility included the following additional infrastructure: - Solids Receiving Station -receiving station for solids trucked in from off-site facilities. - Gravity Belt Thickening -thickening for the HFWWTF WAS to reduce volume prior to dewatering. - Thickened Solids Holding -utilization of the existing Sludge Holding Tanks to provide flow equalization and temporary storage upstream of dewatering. - Belt Filter Press Dewatering - new dewatering equipment to prepare solids for drying. - Cake Storage -- new cake storage silo with live bottom to provide mass equalization and temporary storage upstream of drying. - Dried Product Storage - outdoor storage for dried biosolids product. - Odor Control - control odor infrastructure to manage odorous gasses from new infrastructure and processes. - Bulk Chemical Storage Facility -- store bulk chemicals for use in the thickening, dewatering, and odor control processes. As a regional facility operating at a wastewater treatment plant, process flows vary in their source, quality, and concentration. HFWWTF produces both primary solids and waste activated sludge (WAS). Other consortium members deliver thickened WAS (TWAS) with or without a primary solids component. Table 1 presents a summary of the major contributors and their daily average and maximum contributions (HDR, 2020). These are daily values and do not reflect actual hauling schedules. Some utilities haul weekly, while others haul monthly or less. This varying pattern of solids, sources, and loadings presents a challenge for polymer and feed rate optimization. During startup, standard operating procedures and tracking logs are being developed to allow operators to identify and maintain an optimized performance with a variety of different sludge characteristics. Startup and Training Due to the sequential and interconnected nature of the process flow and the lack of existing biosolids infrastructure, startup requires careful planning to ensure success. Each upstream process must operate in specific parameters prior to startup of the next process (i.e. the dryer cannot operate with cake lower than 16% solids). Process control checkpoints have been established to ensure process flow is available and adequate when required. Close coordination between all parties, Owner, Engineer, Contractor, and Manufacturer coordination has been and will remain critical during the startup and commissioning period. Operator training is also key to the successful completion of the project. HFWWTF staff do not typically operate or maintain solids handling equipment, therefore additional trainings are being scheduled outside of the traditional manufacturer provided sessions. These include overall systems trainings, site walkthroughs, and shadowing. Additionally, standard operating procedure documentation and tools are being developed to assist operation staff. This includes a comprehensive biosolids operations and maintenance manual providing a single reference point for the entire system. Findings Startup of the biosolids handling facility is currently ongoing. The ultimate focus of the paper will be results, conclusions, and lessons learned from this process. Initial findings point towards the following lessons learned: - Reliance on contactor scheduling accuracy and introducing backup plans for missed schedules - Startup of facilities requires precise coordination between all parties within the construction process - Process control milestones are necessary to ensure all equipment is commissioned with appropriate process flow prior to starting up equipment. - Process control milestones cannot exist in a vacuum and must be coordinated with the contractor's schedule to ensure the correct critical path is identified - Holistic system training is beneficial to operators and maintenance staff who may be experiencing new types of equipment - Creation of standard operating procedures that capitalizes on commissioning lessons-learned - How to continue efficient operations and continuous optimization of the system following startup, after the contractor and manufacturers are gone As startup and process optimization continue additional findings, including quantitative data, will be documented and shared. Significance of the Project As populations continue to increase, biosolids disposal needs will become more important for urban and rural centers alike. This not only drives the need for new equipment, but also the need to regionalize biosolids handling operations, either in a consortium or within a single utility. While beneficial, regionalization also introduces operational challenges with members providing sludge of varying quality and quantities. Coupled with the introduction of new equipment, startup, commissioning, and training is a vital process to ensure a successful transition from construction to operation. This transition increases process optimization, ultimately saving rate payers money through time, energy, and material savings. This project represents an example of a holistic approach to the startup and training period. Whole system overview trainings and standard operating procedure documentation are coupled with manufacturer provided trainings to jump start an optimized process and lead to a culture of continuous process optimization. While sometimes an afterthought, the startup and training process is critical to the overall success of a project.