LANDFILL GAS CONTROL PROJECT TO MITIGATE HYDROGEN SULFIDE EMISSIONS AT THE CAROLINE COUNTY SANITARY LANDFILL

摘要

This paper presents a case study of a successful landfill gas (LFG) control project, initiated in response to concerns with hydrogen sulfide (H_2S) emissions, odors, and LFG migration. An increase in malodorous emissions from the site was noted after gypsum-containing material was used as an alternate daily cover (ADC). In addition, the LFG monitoring network indicated elevated methane concentrations at the facility boundary. To control odors, fifteen passive vents with passive wellhead flares were installed and the problem landfill mound was closed and capped in November 1996. The passive wellhead flares were determined to be less than sufficient treatment devices. In June 1997, the LFG passive vents were connected to aboveground LFG collection piping and active extraction commenced. The schedule for system activation was critical due to the facility's proximity to the site of an international Boy Scout Jamboree, which began in the middle of July 1997, on the military base adjacent to the landfill. The H_2S concentrations in the extracted LFG were above OSHA and NIOSH exposure limits, thus causing construction activities near the extraction wells to require Level B personal protective equipment. Considering the elevated H_2S concentrations (greater than 10,000 ppm), a pilot-study program to evaluate the most suitable treatment technology was conducted. The study used an interim blower/flare station and a scrubber tower where a chemical solution was introduced into the extracted LFG to remove H_2S prior to combustion at the utility flare. Upon conclusion of the pilot-study, a final treatment system design was developed, and the equipment representing the permanent blower/flare station was installed. The LFG collection and control system is comprised of two complete and separate blower/flare stations connected to a wellfield consisting of 28 extraction wells. This paper chronicles the actual field conditions and operations and discusses several unique challenges faced during the project. The alternatives and solutions pursued in order to achieve the project objectives are also presented. The paper addresses health and safety issues regarding chemical compounds present in the LFG, the LFG collection and control system design and construction, operations and maintenance, site monitoring data and system performance test results, as well as some estimates for historical and future H_2S production rates.