BIOGENIC POLLUTANT MOBILIZING AGENTS IN THE WASHING OF A CONTAMINATED SOIL AND IN THE AEROBIC BIOREMEDIATION OF THE RESULTING EFFLUENTS

Soil washing might be an effective strategy for remediating soils which are not treatable through conventional bioremediation techniques. In the present research, the possibility of replacing toxic and recalcitrant chemical surfactants, which are commonly employed in such a treatment, with biogenic, nontoxic and biodegradable pollutants mobilizing agents was investigated (1). A soil historically contaminated by chlorinated aromatic compounds was suspended (15% w/v) in water or in water with 1% (w/v) of -cyclodextrin (-CD), Hydroxypropil--cyclodextrin (HP--CD), Rhamnolipid (RL), dissolved Humic Substances (HS) or Triton X-100 (TX) in batch reactors then shaken for 24 h. The resulting effluents were transferred in shaken batch reactors and then treated aerobically for 65 days (1). All biogenic agents enhanced the pollutant solubilizing potential of water (by 237 % for -CD, 265% for HP--CD, 400 % for RL and 566 % for HS). TX mediated the highest solubilizing effect as it enhanced the overall pollutant removal by about 660 %, but it mediated the lowest depletion of the original soil ecotoxicity. In addition, TX adversely affected the bioremediation of the effluent, by apparently inducing a premature depletion of specialized bacterial biomass. The biogenic agents, and in particular HS and RL, sustained the biodegradation and dechlorination of pollutants, by apparently enhancing the availability of specialized bacteria in the reactors (1). Thus, the biogenic agents, and in particular HS and RL, seem to be effective and nontoxic agents for the remediation, through the integrated approach here evaluated, of poorly bioremediable (chloro)organics-contaminated soils (1). (1) S. Berselli et al., (2004) Biotechnology & Bioengineering 88: 111-120.