The bioremediation of soil contaminated with polycyclic aromatic hydrocarbons (PAH) often is limited by a low bioavailability of the contaminants. The effect of two nonionic surfactants of the alkylphenolethoxylate type, Arkopal N-300 and Sapogenat T-300, on bioavailability of PAH in manufactured gas plant soil was evaluated in soil columns percolated by recirculating flushing water. Both surfactants enhanced the mass transfer rate of sorbed PAH into the aqueous phase due to solubilization. Solubilized PAH were available for biodegradation. Degradation of the surfactants themselves was monitored by counting cell numbers of surfactant degraders. It could be demonstrated that the rapid degradation of Arkopal N-300 resulted in a lack of oxygen and an inhibition of PAH degradation. Sapogenat T-300 was degraded more slowly, but a depletion of oxygen occurred after 54 d of incubation. Until then the surfactant-enhanced PAH mobilization resulted in an increased PAH degradation as compared to the treatment without surfactant. Therefore, biodegradability of the surfactants was shown to be one of the key functions for the use of surfactants in practice. Reduction of PAH content and toxicity of the contaminated soil was obtained in all cases. Decrease of soil toxicity as indicated by the bioluminescence test was most pronounced in case of the Sapogenat T-300-amended treatment. It is concluded that surfactants can be a useful tool for stimulating biodegradation of PAH in contaminated soil.

Several laboratory column percolators were operated in order to study the bioremediation potential of polycyclic aromatic hydrocarbons (PAH)‐contaminated soils. The columns contained either soil artificially amended with specific PAH mixtures or contaminated soil from a site in Karlsruhe, Germany. In all cases, biodegradative processes led to the elimination of the original contaminants. This, however, was accompanied by a marked increase in genotoxic activity of the column effluents as determined by the MutatoxTM assay. Genotoxicity was practically abolished, however, when a surfactant was added to the percolating fluids. While in some cases the changes in genotoxicity were paralleled by toxicity (MicrotoxTM) data, in others the trend was opposite. It is concluded that when degradation is incomplete, the potential exists for toxicity and genotoxicity enhancement, with the latter hazard not always predictable by short‐term toxicity assays. Routine genotoxicity monitoring is thus advocated for bioremediation projects; the MutatoxTM assay appears to be a convenient tool for this purpose. © 1994 by John Wiley & Sons, Inc..

This research examined whether treatment with zero-valent iron in the presence of oxygen is a suitable process for the degradation of pharmaceuticals (antibiotics, cytostatic drugs) and diagnostic agents. It was shown that the concentration of all selected compounds was decreased efficiently by treatment with iron. The compounds exhibited a pseudo-first-order decay with a linear dependence on ln(c/c(0)) on time. The observed reaction rate strongly depended on pH, the amount of added iron, and the stirring speed. The influence of temperature on the reaction rate was small. Comparison of detected transformation products with those obtained after catalytic hydrogenation and treatment with Fenton's reagent revealed that reductive and oxidative processes are responsible for the transformations observed.

In particular in arid regions the reuse of waste water and aquifer recharge is an important issue. Elimination of persistent emerging pollutants represents a key factor in integrated water resources management, and identifying suitable treatment processes to eliminate such compounds becomes inevitably necessary. It is the objective of this study (1) to assess the occurrence of emerging pollutants in the Jordan Valley and (2) to review and examine the biodegradability of selected key compounds. Among the most frequently detected compounds during a sampling campaign in 2007 were pharmaceutical residues such as carbamazepine, diclofenac, or naproxen, and X-ray contrast agents such as diatrizoic acid and iopromide, all typically found in Europe and the USA as well. To gain further insight into elimination processes, biodegradation studies were conducted with batch tests and flow-through soil columns under unsaturated, aerobic conditions. Results demonstrated biodegradation for pharmaceutical residues such as ibuprofen, diclofenac and bezafibrate. The degradation rate was faster in treated waste water as compared to raw waste water, most probably due to competing substrate consumption in raw waste water. The antiepileptic carbamazepine showed no degradation in the batch tests and only moderate removal during soil passage, probably due to sorption. The results of this study and previously published data emphasize the need for further studies under more defined conditions to elucidate the specific conditions under which biodegradation of emerging pollutants proceeds.

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