AUTOMATION OF BIOSOLIDS DEWATERING AND HANDLING IN WINSTON-SALEM, NORTH CAROLINA

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 trucksbays have been provided to allow for continuous loading of dewatered biosolids by switching bays as the trucks are filled. Covered, backup short-term storage has also been provided to allow for storage of dewatered biosolids when trucks are unavailable or maintenance of the loading station is required. The facility has been in operation for one year and has successfully minimized the need for operator involvement during handling of the biosolids. 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 bays have been provided to allow for continuous loading of dewatered biosolids by switching bays as the trucks are filled. Covered, backup short-term storage has also been provided to allow for storage of dewatered biosolids when trucks are unavailable or maintenance of the loading station is required. The facility has been in operation for one year and has successfully minimized the need for operator involvement during handling of the biosolids.