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Capacity limitations of tertiary sand filters have been a challenge experienced by wastewater treatment facilities during high flow storm events. High flows during storm events typically lead to shorter filter run times, increased operating costs, and reduced effluent quality while stressing existing facilities due to increased filter backwashing requirements. The Niagara County Sewer District No.1 Water Pollution Control Center is one such facility that experiences significant flow increases during storm events and the associated problems that these conditions cause.

The normal operating scenario during wet weather events consisted of tertiary filters rapidly reaching terminal headloss, filling of backwash holding tanks, and subsequent total shutdown of the filters. During these periods of filter bypassing, the effluent quality deteriorated including:

Significantly reduced TSS, BOD5, phosphorus, and settable solids removals

Deteriorated process water quality (in-plant and industrial reuse)

Deteriorated disinfection system performance

Several objectives were set forth at the beginning of this undertaking. Foremost, it was desired to significantly increase filter run times and filtering capacity during wet weather events without sacrificing effluent quality. With the increased emphasis on minimizing bacterial loading to the nation's waterways, an additional goal was set to improve the efficiency and cost effectiveness of the existing disinfection system.

A complete retrofit with a deep bed, coarse mono media filtration system, including simultaneous air-water backwash, was selected as the system that best met the Sewer District's needs. The key to the selection of the deep bed filtration system was the large diameter media that allows deeper penetration of solids into the filter bed. The new filtration system's performance has been vastly superior to the previous filtration system. The Sewer District has met their goal of increasing filtering capacity and filter run times, eliminating bypassing of the filters, while providing a higher quality effluent.

Document Type: Research Article


Publication date: January 1, 2001

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  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

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