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ENV-07-112 Optimizing LNAPL Remediation at a Former Oil Terminal

Patrick Madden, P.E. and Jeffery Hansen, P.H., URS Corporation

Format:
Electronic (digital download/no shipping)

Associate Member, International Member, Petrochemical Member, Refining Member, Special/Temporary Member - $0.00
Government, NonMember - $25.00

Description:

A multiphase extraction (MPE) system was installed at a former oil terminal in 2003 for the purpose of recovering light, non-aqueous phase liquid (LNAPL). The LNAPL consists of weathered No.2 and No.6 fuel oil, initially impacting about half of a 30 acre site. The high mixing energy of the extraction process caused the LNAPL to be recovered as an emulsion, requiring extensive processing to separate the oil and clean the water for discharge. This included acid and flocculent addition followed by pH adjustment, microfiltration, air stripping, and liquid carbon treatment. A thermal oxidizer (TO) treated the soil gas extracted by the system’s liquid ring pumps. The system employed 2 full time operators and cost over $850,000 per year to operate. Net energy analysis showed that an equivalent of 42 gallons fuel was consumed for every gallon LNAPL recovered. After taking over the site in mid-2006, URS simplified operations, reduced chemical usage by 75%, and replaced the TO with a carbon system. These changes immediately saved about $275,000 per year. Further analyses of operating data demonstrated that LNAPL collection is most efficient when groundwater is low. An analysis of site characteristics and LNAPL properties showed that shutting down when the water is high would not result in LNAPL migration or lost recovery. The MPE system was shut down in April 2007 due to high groundwater levels, and individual well monitoring and recovery systems were put in place. LNAPL-only recovery methods have proven to be more flexible, dramatically less energy intensive, and much less costly to operate.

Product Details:

Product ID: ENV-07-112
Publication Year: 2007