Primary filtration and wet weather pilot system.
Cloth Media Filtration Unit Design
Cloth media filtration has been used in tertiary applications for over 20 years. Its proven performance and operational advantages model a viable solution for primary filtration or wet weather treatment applications.
The outside-in flow path in cloth media filters, specifically the AquaPrime filter, allows for three zones of solids removal, discussed below. These three zones become even more critical in wet weather applications due to the high solids environment in primary filtration and wet weather treatment applications.
Floatable Zone: The top, or floatable, zone is where floatable scum is allowed to collect on the water surface. As the water level increases, the scum is removed by flowing over the scum removal weir, where it’s then directed to the plant’s waste handling facilities. The floatable scum is removed typically one to three times per day by opening a floatable valve.
Filtration Zone: The middle, or filtration, zone is where the majority of solids are removed through filtration. Here, solids deposit on the outside of the cloth media, forming a mat as filtrate flows through the media. Once a predetermined liquid level or time is met, the backwash shoe contacts the media directly and solids are removed by vacuum pressure using the backwash pump. During backwash, fibers fluidize to provide an efficient release of stored solids deep within the fiber.
Solids Zone: The bottom, or solids, zone is where heavier solids collected on the bottom of the tank are removed on an intermittent basis from the hopper using collection laterals and the backwash pump.
Pilot Testing
A pilot trailer and three stand-alone units have been specifically designed for primary filtration and wet weather filtration applications. The unit is currently traveling around the United States and is collecting data at various plants. These primary filtration studies show excellent removal efficiencies in both TSS and BOD across all pilot testing sites: 75-85 percent removal of TSS and 45-60 percent removal of BOD, a 20-30 percent increase over conventional primary sedimentation.
Energy Reduction
Cloth media filtration produces significant energy and capital cost savings as a result of carbon diversion. The high organic energy content of the VSS removed in cloth media filtration means more biogas energy production in the anaerobic digestion process. Further, due to reduced organic loading, the process reduces electrical energy required for aeration in secondary treatment.
Other benefits include the possibility of expanding plant capacity by reducing the organic loading upstream of the secondary process. It is also compact, requiring 10-20 percent of the footprint of a conventional sedimentation solution.
Conclusion
AquaPrime cloth media filtration is a viable technology for treating many different primary and primary effluent applications, both municipal and industrial. The technology provides a high-quality effluent, easy operation, and major operating savings in reduced energy consumption in the treatment facility. IWW
About the Author: John D. Dyson is a product channel manager for Aqua-Aerobic Systems Inc.
References
Caliskaner, Onder; Tchobanoglous, George; Young, Ryan; and Laybourne, Sarah. “Demonstration of Primary Effluent Filtration for Carbon Diversion to Save Energy and Increase Plant Capacity,” Proceedings, WEFTEC 2014, New Orleans, LA, 2014.
