A compact remediation system for the treatment of groundwater contaminated with BTEX and TPH.

Gas stations constitute important point sources of soil and groundwater pollution. The leaking of hydrocarbons into the soil is a significant environment issue due to the wide-ranging occurrence of leaks and the high levels and toxicity of pollutants involved in the contamination of groundwater for human use. This study introduces a compact system developed to treat groundwater contaminated with benzene, toluene, ethyl benzene, and xylenes (BTEX) and total petroleum hydrocarbon (TPH) leaked from gas station tanks. The system comprises three units: (1) suction and volatilization of volatile organic compounds (VOCs), (2) aeration tank (to remove volatile organic substances), and (3) an adsorption packed-bed filter (activated carbon (AC) and rice husk ash, 50% each, to remove TPH). Contaminated groundwater was characterized in a pilot study and in the field. Levels of BTEX and of TPH decreased by 96% with an 8-h retention time. The results obtained show that the remediation system is highly efficient and yielded water that met the discharge standards defined in the Brazilian legislation, that is, maximum benzene, toluene, and xylene levels of 5, 170, and 300 µg/L, respectively.

Performance of UASB and DAEB reactors in the anaerobic digestion of synthetic wastewater containing sodium oleate and sodium stereate.

This study aimed at evaluating the performance of five laboratory-scale reactors, three UASB and two downflow anaerobic expanded bed (DAEB), fed with saccharose and long chain fatty acids (LCFA) for 410 days. Reactors operated at a temperature of 35 degrees C. The organic load rates were changed between 3.45 and 6.38 kg COD.m3.d(-1). During period I the substrate was saccharose and in periods II, III and IV it was saccharose plus sodium oleate, stereate and a mixture of sodium oleate and stereate. The UASB and DAEB reactors showed a similar performance. In UASB reactors specific methanogenic activity decreased in the periods II, III and IV. COD removal, biogas production and CH4 concentration in biogas decreased in all reactors at the end of the study. A washout occurred in UASB 2 and 3 when sodium stereate exceeded 500 mg.L(-1). In DAEB reactors the main problem was adsorption of LCFA particles onto the solid support.