Operation of a Full-Scale Biotrickling Filter Reactor to Treat Off-Gas Emissions Generated from an Industrial Wastewater Treatment Plant
Abstract:The passage of the Clean Air Act Amendments (CAAA) has justified the need for increased investigation into the treatment of air streams containing volatile organic compounds (VOCs) and hazardous air pollutants (HAPs). In cooperation with the Office of Naval Research, Naval Air Station North Island (NASNI, San Diego, CA) has recently begun operation of a full-scale biotrickling filter reactor to treat VOCs, HAPs, and odorous emissions from their industrial wastewater and oil recovery load equalization and treatment tanks. The full-scale implementation of this system is a direct result of successful bench- and pilot-scale research conducted on the efficacy of the technology in treating industrial off-gases.
The bench-scale studies involved developing microbial cultures that could effectively treat four representative VOCs: toluene, xylene, methyl ethyl ketone (MEK), and n-butyl acetate. Using the characterized microbial cultures as inoculum, bench-scale testing demonstrated that all four target compounds could be simultaneously removed with greater than 95 percent efficiency in biotrickling filters. In addition, over a three-year period, a 12-inch diameter column was tested using three different sizes of a proprietary random packing material under full-scale flow regime conditions. Operated under varying air velocities and liquid recirculation rates, pressure drops were demonstrated to be below 0.2" WC/ft for full-scale system flow regimes.
From the bench-scale study results, an optimal biotrickling filter support was selected and tested in a pilot-scale biotrickling filter reactor treating spray paint booth emissions generated at the North Island Naval Facility. The microbial cultures developed during the bench-scale experiments were used as inoculum. Four different vapor contact times (39, 28, 16, and 11 seconds) were tested and conditions were optimized to achieve maximum VOC removal. Total VOC and HAP removal efficiencies ranged from 70 to 100 percent.
Similar to the contaminants treated during the pilot experiment, the primary contaminants of concern for treatment at the industrial wastewater treatment plant are phenol, methylene chloride, methyl ethyl ketone, benzene, toluene, ethylbenzene, xylene (BTEX), and hydrogen sulfide (H2S). Total VOC and H2S concentrations range from 7 to 521 ppmv and 1 to 2 ppmv, respectively. The air flowrate through the system is 3,140 m3 h−1 (1,850 scfm).
The full-scale biotrickling filter reactor is the largest and first of its kind developed for the United States Navy. The vessel is 3.1 m (10 ft) in diameter and 9.1 m (30 ft) in height. The reactor is an air downflow system and operates in cocurrent fashion with a recirculating water phase. Random, inorganic packing is used as a filter bed material. The system is automated and controlled through the use of a programmable logic controller that minimizes the need for operator attention. The system began operation in early December, 1999. This paper discusses the implementation of the system and the preliminary findings of the project.
Document Type: Research Article
Publication date: January 1, 2000
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