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Actiflo® High-Rate Clarification Retrofitted into Terminal Treatment Plant at Severstal na Sparrows Point LLC

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Severstal NA Sparrows Point LLC (Severstal NA) was issued new NPDES permit limits by the State of Maryland for the Humphrey's Creek Waste Water Treatment Plant, its terminal treatment facility. This facility treats most of the mill's industrial wastewater effluent and storm water runoff, and discharges the treated water to Bear Creek, a tributary to Chesapeake Bay. The new permit contained more stringent requirements for total suspended solids, oil and grease, copper, nickel, and other constituents than the facility's previous permit. Severstal NA compared the new permit limits to its existing facility's performance and decided that an upgrade was necessary. Severstal NA then contracted several industrial wastewater treatment companies to pilot test their respective systems to determine the optimal solution. N.A. Water Systems (N.A.WS), a Veolia Water Solutions & Technologies company, was given this opportunity and opted to demonstrate the ACTIFLO® process. This unique high-rate clarification process had been used extensively worldwide to treat surface waters for drinking water as well as municipal wastewater for solids removal, but had few installations in industrial applications.

The pilot testing showed that the ACTIFLO® process could effectively treat the Severstal NA wastewater at overflow rates of 40 to 60 gpm/ft2. In order to meet the more stringent effluent limitations for the metals, the ACTIFLO® process was augmented with iron coprecipitation/adsorption, higher pH adjustment, and sulfide precipitation. Based on the success of the pilot studies, N.A.WS was awarded a design-build contract to implement the upgrades. The system was designed to treat an average base flow rate of 20,000 gpm, with the capacity to handle flows up to 150,000 gpm.

The upgraded HCWWTP produces a crystal-clear treated effluent, often with turbidity less than 1 NTU. The effluent consistently complies with the very stringent limits for copper, nickel, dissolved oxygen (DO), oil and grease (O&G) and total suspended solids (TSS). The net effect is that the receiving stream, Bear Creek, is noticeably cleaner. Using this technology, Severstal NA, a responsible corporate neighbor, has responded to Maryland's current NPDES standards and efforts to protect the Chesapeake Bay with a state-of-the-art industrial treatment facility.

Keywords: ACTIFLO; clarification; metals removal; sand ballasted flocculation

Document Type: Research Article


Publication date: 2009-01-01

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