H.I. Atagana and R.J. Haynes (South Africa)
bioremediation; composting; creosote; organic manures; polycyclic aromatic hydrocarbons; sewage sludge
Soils around a creosote wood preservation factory were found to contain very high concentrations (> 300 000 mg kg-1 ) of creosote. Attempts at land farming were ineffective at reducing concentrations of recalcitrant polycyclic aromatic hydrocarbons (PAHs) to acceptable levels. An attempt was made to achieve removal of creosote compounds by co-composting contaminated soil (380 000 mg kg-1 ) with organic waste materials (sewage sludge, vegetable waste, cow and poultry manure). Concentrations of residual creosote present in the soil after the 19-month composting period were high in the control (only 17% creosote degraded) and low in the composted treatments (97 – 98% degraded). The composting periods required to reduce residual creosote concentrations to below 10 000 mg kg-1 were : poultry manure, 13 months; vegetable waste, 9 months; cow manure, 8.5 months and sewage sludge, 7 months. The relatively rapid rate of decomposition during co composting with sewage sludge was attributed to the high initial microbial load in sludge and the heterogeneous nature of the organic substrate which probably supported a metabolically diverse microbial community which was able to adapt rapidly to the creosote substrate. It was concluded that co-composting is an attractive as well as effective bioremediation strategy since it involves the simultaneous use of wastes and the decontamination of polluted soil.
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