Filters For Future - What Every Utility Needs to Know About Tertiary Treatment


  • Patricia Drummey Stiegel PE, Olivia Flynn PE, Joe Rohrbacher PE - Hazen and Sawyer

Tertiary filtration of treated wastewater is becoming more common as plants face low limits for total phosphorus (TP), total nitrogen (TN), Biological Oxygen Demand (BOD), or Ultimate Oxygen Demand (UOD). Filters are also used to meet recycled water/reuse limits in South Carolina and across the country. This presentation will give an overview of available technologies, including disk filters with various media types such as woven cloth, pile cloth, and stainless steel, sand filters with multiple configuration and media types, compressible media filters, and membrane filters.

Site-specific considerations for filter technologies include hydraulic grade line, overall facility footprint, backwash flow, and compatibility with chemical additions such as coagulant to assist in meeting TP limits and supplemental carbon for low TN limits. General cost and energy efficiency comparisons will also be included.

This presentation will explore several case studies, including a plant in Virginia that recently constructed deep bed filters sized to treat a portion of their flow. The project received partial grant funding as the filters were designed for Total Phosphorus removal. The facility is currently performing exceptionally well. A second case study will be presented on a pilot of various media types that were tested for solids and TP removal at a North Carolina plant with existing traveling bridge filters. The plant is unable to pass peak hydraulic flows through the filters, resulting in reportable bypass events. Pilot results showed that due to the limitation in media depth, the current dual media configuration with sand and anthracite provides the most reliable solid and phosphorus removal. A design to enhance the backwash ability of the current media is expected to increase the peak hydraulic capacity of the facility.

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Horizons Fall 2017 (pdf)

Horizons showcases significant water, wastewater, reuse, and stormwater projects and innovations that help our clients to achieve their goals, and can help you achieve yours. Articles are written by top engineers and process group leaders, demonstrating and explaining the beneficial application of a variety of technologies and tools.

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