Flare pits have been used by the upstream oil and gas industry for decades to store and/or burn produced fluids at well sites, compressor stations and batteries. Since produced fluids contain liquid hydrocarbons, process chemicals, crude bitumen or salt water, flare pit (FP) waste usually contains high levels of hydrocarbons, metals, and salts. Bioremediation by land application is the most common method practiced by the oil and gas industry to treat FP waste. High rate slurry phase and solid phase biotreatment methods are viable alternatives to the low cost yet inefficient land treatment option. They can also be used as a rapid biotreatability-screening tool.
The slurry phase biotreatment of flare pit waste using 2-L slurry reactor showed an initial decrease in petroleum concentrations, however biodegradation decreased or ceased with time, leaving recalcitrant compounds. The nutrient concentrations (above 350 mg N/L as ammonium nitrogen) did not exhibit statistically significant effects on hydrocarbon degradation. The primary effect of waste composition was highly significant, with higher soil clay content resulting in lower biodegradation.
A laboratory solid phase bioremediation study was conducted over a period of 270 days using a statistical partial factorial experimental design. The effects of nitrogen, phosphorus and salinity levels and incubation temperature on the biodegradation of hydrocarbons in the flare pit waste were investigated. A soil contaminated with flare pit hydrocarbons was treated with nitrogen (500, 1250, or 2000 mg/kg of soil), phosphorus (100, 250, or 400 mg/kg of soil) and salt (yielding electrical conductivity of 0, 20, or 40 dS/m) and incubated at three temperatures (20 °, 30 ° and 40 °C). The highest oil and grease (O&G) reduction of 34% was observed in the soils incubated at 30 °C. Soil temperature had more influence on bioremediation rates than did N or P levels. The high P levels, up to 400 mg P/kg soil, had no detrimental effect on hydrocarbon biodegradation. High salinity levels reduced the oil biodegradation rate.
In oil fields around the world, flare pits have been used for decades to store and/or burn produced fluids at older oil and gas well sites, compressor stations and batteries. The produced fluids usually contain a variety of liquid hydrocarbons, process chemicals, crude bitumen and salt water. The usual practice is to store and intermittently burn these produced fluids in earthen pits called "flare pits". The end result is the creation of a highly complex waste known as flare pit (FP) waste. Alberta, the oil province of Canada, is home to about 30,000 flare pit sites.(1) In 1996, the provincial Comparative studies have shown that thermal methods are the most effective (2), but the application of such methods is expensive and poses logistical problems in some locations. For example, in Alberta, the FP sites are scattered over a large geographical area, wherever oil production has taken place. Thermal methods are most cost-effective if used as an ex-situ centralized treatment technique.(2,3) Since FP wastes are found in relatively small quantities scattered over a large number of sites, flexible on-site or in-situ techniques, such as bioremediation, is more cost effective.