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

Abstract

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.

Role of Autochthonous Filamentous Fungi in Bioremediation of a Soil Historically Contaminated with Aromatic Hydrocarbons

“…Among them, biostimulation of indigenous prokaryotes turned out to be unsuccessful, despite the presence of bacteria specialized in the catabolism of several aromatic compounds (10).…”

Sustainable decontamination of an actual‐site aged PCB‐polluted soil through a biosurfactant‐based washing followed by a photocatalytic treatment

“…It was also analyzed for its main mechanical properties according to standard methods described by Gee and Bauder (1986). Soil washing experiments were performed as described by Berselli et al (2004). In brief, 150.0 g of airdried soil were suspended in 1.0 L of distilled water or a water solution (prepared in distilled water) of SL or TX at 2.25 g/L (corresponding to 15 g of applied agent per kg of air-dried soil) in identical 3L-baffled Erlenmeyer flasks closed with Teflon liner-screw caps.…”

“…Satisfactory decontamination yields have been obtained with this technique on a variety of hydrocarbons polluted soils; in the most of the cases aqueous solutions of commercial synthetic surfactants have been applied at concentrations well above their critical micelle concentrations (CMCs; Chang et al, 2000;Cheah et al, 1998;Chu and So, 2001;Deshpande et al, 1999;Mulligan et al, 2001;Saxe et al, 2000;Urum and Pekdmir, 2004). In general synthetic chemical surfactants were found to persist and exert toxic effects both in the soil resulting from washing (Berselli et al, 2004(Berselli et al, , 2006Christofi and Ivshina, 2002;Rouse et al, 1994;Volkering et al, 1998;Wong JW et al, 2004) and in the resulting aqueous effluents (Berselli et al, 2004(Berselli et al, , 2006. This limitation of conventional soil washing procedure can be mitigated by replacing synthetic surfactants with biogenic pollutant mobilizing agents able to provide marked pollutant mobilization activity along with complete biodegradability and none toxicity (Christofi and Ivshina, 2002;Rouse et al, 1994;Volkering et al, 1998).…”

“…This limitation of conventional soil washing procedure can be mitigated by replacing synthetic surfactants with biogenic pollutant mobilizing agents able to provide marked pollutant mobilization activity along with complete biodegradability and none toxicity (Christofi and Ivshina, 2002;Rouse et al, 1994;Volkering et al, 1998). So far, few information are available about biogenic agents' suitability for soil washing operations (Berselli et al, 2004(Berselli et al, , 2006Conte et al, 2005). Some commercial phytogenic surfactants, like soya lecithin (SL), have been found to be very effective hydrophobic pollutantsmobilizing agents in the semisolid bioremediation of PCBs contaminated soils Di Gioia, 1998, 2001).…”

“…The large scale application of conventional soil washing procedures is also inhered by the fact they generate large volumes of contaminated aqueous streams which are generally not easily detoxified through conventional or advanced biological treatments (Berselli et al, 2004(Berselli et al, , 2006. These effluents might be decontaminated through photocatalytic treatments based on the use of dispersed or fixed-bed TiO 2 catalysts.…”