Comparison of Open and Enclosed Belt Filter Presses and Evaluation of Automation to Improve Performance and to be More Sustainable

Many features on belt filter presses (BFPs) should be evaluated prior to selection. Open BFPs are preferred over enclosed presses by most wastewater operators, including the DC Water (formerly District of Columbia Water and Sewer Authority, DCWASA) operation and maintenance (O&M) staff that operate the Blue Plains Advanced Wastewater Treatment Plant (AWTP), since they provide better operational and maintenance access. However, there are a limited number of plants in the United States where due to odor and ventilation cost reasons, have installed enclosed presses. A detailed evaluation of BFP features, design criteria, and advantages and disadvantages was performed, several tours were performed, and discussions with O&M personnel and representatives from the major BFP manufacturers were completed. Based on the compilation of information, the DC Water staff decided to restrict options to a “base BFP bid.” The BFP equipment submittal for the Final Dewatering Facilities (FDF) project will now include open presses with an I-beam frame and external frame mounted enclosures for odor containment.The automation of wastewater treatment plant (WWTP) dewatering equipment has been successful at some United States installations to optimize performance and to be more sustainable by reducing polymer consumption and energy consumption of downstream processes, especially with varying feed solids characteristics.However, automation of solids dewatering control systems has experienced some problem areas. One has been with the lack of accuracy and reliability of instrumentation. Second, getting “buy-in” from WWTP operators to properly clean, maintain and periodically calibrate the installed analyzers. Thirdly, environmental variables (such as pH) which were independent of the solids dewatering process could affect the instrument output. Overselling analyzer capability, and under emphasizing the work involved with maintenance requirements to keep an analyzer reporting accurate data, has contributed to failed installations. Therefore, successful solids dewatering automation requires: 1) proven, accurate and self-cleaning monitoring instruments, 2) “buy-in” from the plant operators to properly clean and maintain the probes, and 3) an automation “champion” on staff who wants to make the system work.