From Tech Trends November 1995

Flare Pit Wastes - Test Results

Canada, which has an abundance of flare pit waste sites, selected flare pit wastes as the third waste to be tested in its Bio-Reactor. The Canadian Bio-Reactor Project tests the premise that hydrocarbon contaminated soils and soil-like wastes with high levels of salts can be treated effectively and efficiently by combining leaching with soil biological process by exerting strict controls on all inputs, the physical-chemical environment and the fate of the transformed waste products. TECH TRENDS has previously reported on the results of the first two wastes treated in the Bio-Reactor. A major Bio-Reactor Project axiom has been that good structure is essential for bioremediation of solid wastes. However, with the third waste to be treated, results suggest that super sophisticated controls and procedures may not be necessary to eliminate hydrocarbons from wastes as long as the basic needs of the microorganisms are satisfied in the combined leaching and bioremediation.

Flare pit wastes are common at sites in oil and gas producing regions; and most, if not all will require remediation. Flare pits are located at well sites and some pipeline pump stations where waste gases are burned off; and, periodically liquid waste hydrocarbons may be diverted to pits. Pits may also contain brine, condensates, lube oils, tank bottom sludges, pigging waxes and other wastes that comprise a cornucopia dS m-1) and had a 7.5 pH. The waste had very heavy clay clods form contained 8.5% hydrocarbons, a high level of brine salts (EC > 30 and balls of tar-like material and posed handling and wettability problems. Factors tested in the Bio-Reactor included the potential value of aggregation (i.e., does particle size have an effect); cultivation; inoculation practices; and waste depth under uniform conditions of nutrients, water and forced aeration (i.e., how deep can be wastes be layered before aeration becomes a problem --20 cm versus 40 cm).

Treatment in the Bio-Reactor resulted in a 30% decrease in hydrocarbons during the seven-month period for the "best" (i.e., amended) treatment. Unexpectedly, there were also substantial losses in the "worst" (i.e., no amendment) treatment which was characterized as having very poor structure and porosity. It did not matter whether or not the waste was aggregated, cultivated, or inoculated or to which depth it was piled. Differences in hydrocarbon loss rates among waste aggregated, cultivated, inoculated or piled to 20 or 40 cm depth appeared to be small. All of this suggests that the ability of microorganisms to function well under what appear to be very adverse conditions was underestimated.

The Bio-Reactor can effectively treat flare pit wastes by first removing the salts through leaching and then reducing the hydrocarbon contents through bioremediation.

Although the treated material has relatively high residual hydrocarbon levels, these hydrocarbons have a low bioavailability so that the material is non-toxic in a battery of tests and will pass leachate requirements.

As a side note, see the companion article in this issue of TECH TRENDS, p. 3, which discusses the serious analytical problems encountered and the remedy.

For more information, call the Bio-Reactor Project's Project Manager, Lin Callow, of Gulf Canada Resources, Ltd. at 403-233-3924.

For progress reports and more detailed reports, contact Lisa Crichton at the Canadian Association of Petroleum Producers (CAPP) by phone at 403-267-1100 or by FAX at 403-261-4622. There is a charge for the reports. Information in this article is from the August 1995 issue of the "BIO-REACTOR PROJECT Newsletter," published by CAPP.

The Bio-Reactor Project is co-funded by the CAPP; by Environment Canada through its contributions to the Development and Demonstration of Site Remediation Technology Program (DESRT), GASReP and Federal Program on Energy Research and Development; and by the Alberta Environmental Research Trust. The research is conducted by the Alberta Environmental Centre in Vegreville and the University of Calgary. The Bio- Reactor is located at the Morrison Petroleums, Ltd. Nevis Sour Gas Plant.

For your information, the results of Bio-Reactor treatment of Waste 1, agricultural topsoil, and Waste 2, saline diesel invert mud drill cuttings, were reported in the May 1994 issue of TECH TRENDS (Document No. EPA 542-N-94-004) and can be ordered by sending a request to NCEPI by fax (513-489-8695) or by mail (P.O. Box 42419, Cincinnati, OH 45242-20419).