Abstract

Repetitive spills of fuels and lubricants during reparation and maintenance of machinery within Chilean mining industry constitute an unseen pollution of current environmental concern. These spills had subsequently been adsorbed by desert soils and sawdust used as cheap sorbent materials are considered hazardous wastes (Chilean legislation) and must be contained and disposed on a hazardous waste landfill. Alternative accepted treatments to landfilling consist in biological treatments such as bioremediation, a cost-effective opportunity for Chile. Nevertheless, it remains unknown if bioremediation of fuel-contaminated wastes is feasible under in desert mining soils. In this study we determined the feasibility of bioremediation by aerated in-vessel composting of an aged fuel-contaminated desert mining soil and sawdust. We investigated the removal of total organic compounds (TOCs) in a composting process at laboratory scale under controlled conditions of temperature, humidity and ventilation at five soil to sawdust ratios (S:SD, 1:0, 3:1, 1:1, 1:3, 0:1). Terminal-restriction fragment length polymorphism (TRFLP) tests were conducted in order to determinate the Richness and Diversity of Operational Taxonomic Units through treatment (O.T.U.). We relate removal curves to changes in the diversity of microbial communities determinate molecular tools. Different TOC removal curves were obtained and observed after 56 days of treatment. The highest (50%) and the lowest (35%) removal rate were found in reactor S: SD-0:1 and S: SD-1:0, respectively. Interaction between presence of sawdust and time factors, both as source of variation, was statistically significative on removal curves. No trends were found among changes in richness and diversity as well as in correlation between them and removal curves. However, higher levels of sawdust corresponded with an incremental number of O.T.U., diversity and higher removal's rate. Our results shown that removal TOCs are feasible desert soil at every ratio S: SD but with differential goal achievements and molecular profiles obtained are not a predictive tool related to abatement of pollution in this treatment.