## 1 Introduction  
Biobeds are biopurification systems used to minimize pesticide point-source contamination. Currently, these systems are widely expanded worldwide, accounting for more than 10,000 units, especially in European and South American countries. These systems have an active biomixture that adsorbs pesticides in organic matter and enhances their microbial degradation. The most commonly used biomixture includes soil, peat and straw (25:25:50 vol %)--original Swedish biobed [1]. However, in recent years, peat and straw are being efficiently replaced by local organic wastes from agricultural, agro-industrial and energy production sectors in order to reduce costs and favor the recycling of local wastes [2; 3; 4]. Biomixtures used in the biobeds should be replaced every five to eight years (periodically) in order to maintain the overall efficiency of this biopurification system. After usage, the exhausted biomixtures can contain residues of pesticides. For that reason, they should be considered as hazardous wastes and thus, need special treatments. Among others, dispersion, landfill disposal and incination are techniques applicable to the exhausted biomixtures but, in general, they are expensive and transfer pesticide residues to other compartments. Therefore, decontamination of exhausted biomixtures is essential prior to their final disposal or prior to their possible reuse to enhance biodegradation in new biobeds [5]. Previous studies revealed that, after 76 days of computing and maturation, 70% of bentazon, 93% of linuron, 90% of metalaxyl and 20% of bifenthrin were dissipated from a contaminated biomixture used in a biopurification system [6]. [PERSON] et al. [7] showed that bioaugmentation with pesticides degrading bacteria removed 83% and 97% of thiabendazole and imazalli, respectively,from residual biomixtures. Nevertheless, when the suitable microbial inocula for the degradation of pesticide residues are not available, composting can also be a valuable alternative. Vermicomposting, which involves the joint action of earthworms and microorganisms under aerobic and mesophilic conditions, is a useful biotechnological process for recycling, biodegradation, biostabilization and biomaturation of a great variety of organic wastes [8; 9; 10]. Among others, _Eisenia fetida_ is the most common epigeic earthworm used in vermicomposting processes, characterized by its ubiquity, high reproduction rate, short life cycle, and high tolerance to changing conditions [11]. In addition, this earthworm is one of the more useful species for ecotoxicological testing, being a sensitive indicator of polluted substrates [12]. Although the main objective of that biotechnology is obtaining soil organic amendments--vermicomposts--for agricultural purposes [13; 14], both the final product and the earthworms themselves have been used for bioremediation of soils and organic wastes contaminated with organic pollutants and heavy metals. These biological strategies are included in the term of vermiremediation, which is considered as a promising, low-cost, aesthetically pleasing, and eco-friendly technology [15]. Despite the limited information regarding vermiremediation, the vermicomposting has proven to be an effective process to remove organic pollutants (polycyclic aromatic hydrocarbons, pesticides), even in some complex substrates as sewage sludges [16; 17] or heavy metals in coal fly ashes [18]. In addition, the use of vermicompost as soil amendment reduced the availability and mobility of potential toxic metals [19; 20] and pesticides [21], which favors their elimination in soils [22; 23]. Finally, different studies have reported that the inoculation of polluted soils with different earthworm species, including _Eisenia fetida_, directly or in combination with organic matter, enhanced the degradation and the removal of a broad range of environmental contaminants [12; 15; 24].