Effects of cyclodextrins, humic substances, and rhamnolipids on the washing of a historically contaminated soil and on the aerobic bioremediation of the resulting effluents.

Nontoxic and biodegradable pollutant-mobilizing agents, instead of chemical surfactants, were tested in the washing of an actual-site chloroaromatic-contaminated soil. A soil historically contaminated by chlorinated anilines and benzenes, thiophenes and several polycyclic aromatic hydrocarbons was subjected to washing by suspending it (15% w/v) in water or in water with 1.0% (w/v) beta-clodextrin (beta-CD), hydroxypropyl-beta-cyclodextrin (HP-beta-CD), rhamnolipid (RL), dissolved humic substances (HS), or Triton X-100 (TX) in shaken batch reactors for 24 hr. The resulting wastewaters were amended with nutrients and treated aerobically in shaken reactors for 65 days. The biogenic agents markedly enhanced (by 237%, beta-CD; 265%, HP-beta-CD; 400%, RL; 566%, HS) the capability of water of eluting organic pollutants from the soil. TX enhanced the overall pollutant removal by about 660%; however, a lower depletion of the initial soil ecotoxicity, along with a more extensive impact on the soil organic matter, was observed. Furthermore, TX adversely affected the bioremediation of the resulting effluent by apparently inducing a premature decrease of specialized bacterial biomass. By contrast, 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. Thus, the biogenic agents proposed here seem to be promising nontoxic and nonaggressive soil washing agents for the integrated physicochemical (washing) and biological (aerobic posttreatment) restoration of poorly bioremediable (chloro) organics-contaminated soils.

Photo-Fenton oxidation of oil mill waste water: chemical degradation and biodegradability increase.

The mill waste water holds a large amount of polyphenols, preventing the biodegradation processes because of their inhibitory action on microbial growth. Thus, its disposal represents an environmental problem for the great olive oil producing countries in the Mediterranean area. In this work, we present the preliminary results from the application of a photo-oxidative process on mill waste water to evaluate the organic matter degradation potential and the biodegradability of the treated residue. The total organic carbon is reduced up to 35% after 6 hours but the cost-effectiveness is unfavourable. In contrast, the aim of toxicity reduction is less expensive and shows good applicable chances; after 2 h, the polyphenols concentration drops by 60%.