United States Environmental Protection Agency EPA/540/MR-94/508 April 1994 SUPERFUND INNOVATIVE TECHNOLOGY EVALUATION Demonstration Bulletin Ex-Situ Anaerobic Bioremediation System: Dinoseb J.R. Simplot Company TECHNOLOGY DESCRIPTION: The J.R. Simplot Ex-situ Anaerobic Bioremediation System is a technology designed to destroy nitroaromatic compounds without forming any toxic inter- mediates. The nitroaromatic compound of interest during this demonstration was dinoseb (2-sec-butyl-4,6-dinitrophenol) an ag- ricultural herbicide used to defoliate potatoes and other legumes. (NOTE: A separate demonstration of this technology is being undertaken with 2,4,6-trinitrotoluene (TNT) as the contaminant of . interest. The results of this demonstration will be reported inde- pendently.) The theory of operation behind the J.R. Simplot bioremediation process is that dinoseb-contaminated soils (or liquids) can be treated using an anaerobic consortium of soil microorganisms. Under aerobic conditions, degradation of dinoseb forms polymerization products that are potentially toxic. Anaero- bic degradation of dinoseb takes place without the formation of these polymerization products. The J.R. Simplot technology mixes a carbon source with contaminated soil and then adds water and a phosphate buffer to create a slurry. This prompts aerobic microorganisms to consume the carbon source and oxygen, thus lowering the redox potential (Eh) of the slurry and creating anaero- bic oanditions. Anaerobic microorganisms are then stimulated to consume toxins present in the slurry. Figure 1 presents a schematic flow diagram of the J.R. Simplot bioremediation system. Initially, excavated soil is sent through a vibrating screen to remove large rocks and other debris. The rocks and debris are washed to remove surface contamination. This jrinse waiter is combined with make-up water and added to the bioreactor. Sufficient water is added until the bioreactor con- tains an amount of water sufficient to provide 1 liter of water for each kg of soil to be treated. A phosphate buffer is added to the system to control the pH. Batches of soil and potato starch (2% by wbight) are homogenized together and added to the bioreactor until ihe system is 75% full. Optimum conditions for the degrada- tion [of dinoseb are a temperature of 30 to 35°C and a pH between 7 and 7.5. WASTE APPLICABILITY: This technology is suitable for soils and liquids contaminated with nitroaromatic compounds. How- ever,! the medium to be treated must be free of toxic metals or Contaminated Soil Vibrating Screen Potato Waste Addition contaminated soil > 12.7mm contaminated soil I f < 12.7mm Homogenization (using a pug mill) Mixer Water From Screen Overs Washing * Clean rejects if contaminants in the soil are water soluble. Figure 1. Schematic flow diagram of the J.R. Simplot Ex-Situ Anaerobic Bioremeciation Process - Dinoseb. pH, Redox Potential, & Temperature Probe Printed on Recycled Paper ------- I any other compounds that may be detrimental to the appropriate microorganisms. DEMONSTRATION RESULTS: Two demonstrations of the J.R. Slmptot Ex-Shu Anaerobic Btoremediation System has been performed under the Superfund Innovative Technology Evaluation (SITE) Program. The first demonstration occurred in June/July 1993 at Bowers Field, a municipal airport in the Ellensburg, Washington area. The source of the contamination can be traced to crop dusters in Central Washington during the agricultural season. During the demonstration 30 m3 (40 yd3} of soil contaminated with dinoseb at an average level of 28 mg/kg was placed in the bioroactor. If a larger volume of soil or a molecular bioreactor was to be used for the Demonstration Test, then a lined pit would have boon more appropriate than a molecular bioreactor. The demon- stration was anticipated to last approximately 6 weeks, however, sampling at the anticipated mid-point of the test (23 days) showed that dJnoseb was not detected in any of the samples. This was in sptta of the fact that the average ambient temperature during this period maintained the bioreactor at an unseasonable 18°C. Thus, post-treatment sampling was initiated. Demonstration Testing of the J.R. Simplot Ex-Srtu Anaerobic Btoremediation System gave the following results: • The process can reduce the levels of dinoseb in the feed soil to below detection limits. Based on an average pre-treatment concentration of 28 mg/kg and af inal post- treatment concentra- tion beiow the detection limit of the analytical instrumentation a, >99.8% reduction of dinoseb was achieved. • No known polymerization products were found in the analysis of the post-treatment samples. • Other pesticides (nitroanaline, malathion, and parathion) were reduced from parts per million levels in the feed soil to belowthe analytical detection limit in the treated slurry. • Theprocesscansuccessfullyoperatewithbioreactortempera- tures as low as 18°C, much below optimum. • Treatabil'rty studies and, to a limited extent, the Demonstration Test has shown that continuous mixing of the bioreactor is not required. A static system can achieve acceptable results pro- viding the soil, water, and potato starch are well-mixed during loading of the bioreactor. The presence of other herbicides and pesticides in the feed soil negated the meaningful purpose of performing toxicity tests on the pre- and post-treatment samples as part of the dinoseb Demonstration Test. However, toxicity tests will be performed as part of the demonstration for TNT degradation. An Innovative Technology Evaluation Report describing the com- plete Demonstration and other pertinent information will be avail- able in the Summer of 1994. FOR FURTHER INFORMATION: EPA Project Manager: Dr. Wendy Davis-Hoover U.S. EPA Risk Reduction EEngineering Laboratory 5995 Center Hill Avenue Cincinnati, OH 45224 (513) 569-7206 •U.S. Government Printing Office: 1994— 550-067/80238 United States Environmental Protection Agency Center for Environmental Research Information Cincinnati, OH 45268 Official Business Penatty for Private Use $300 BULK RATE POSTAGE & FEES PAID EPA PERMIT No. G-35 EPA/S40/MR-94/508 ------- |