Innovative application of biobed bioremediation systems to remove emerging contaminants: Adsorption, degradation and bioaccesibility.

Biobed bioremediation systems (BBSs) are widely used to prevent point-source pesticide contamination of water. However, these systems have never been investigated for possible elimination of emerging contaminants (ECs). In this study, two biobed systems, involving biomixtures elaborated with soil and raw olive mill cake (SCP) or its vermicompost (SVP), were assayed to determine their effectiveness in removing the ECs diclofenac, ibuprofen and triclosan from effluent wastewater. Adsorption, incubation and bioaccesibility experiments were carried out. The SCP and SVP biomixtures showed greater adsorption capacity than the soil (S), used as reference. In SVP and S, the degradation rates of the ECs applied were similar and over 94% of these compounds was removed after 84 days of incubation. However, SCP biomixture had a lower removal rate and the percentage of ECs removed ranged from 32 to 68%. In SVP, the bioaccesible fraction (E) reveals that approximately 82% of triclosan and diclofenac adsorption occurred in bioaccesible sites, thus explaining the more efficient decontamination observed in this biomixture. The relationship established between the bioaccesible and biodegradable fractions suggests that E values are a useful tool for predicting the endpoints of ECs biodegradation in bioremediation systems. UPLC/Q-TOF-MS analysis of samples showed different metabolite products.

Biodegradation of high doses of commercial pesticide products in pilot-scale biobeds using olive-oil agroindustry wastes.

Biobeds systems containing soil, peat and straw (SPS) are used worldwide to eliminate pesticide point-source contamination, but implantation is difficult when peat and/or straw are not available. Novel biobeds composed of soil, olive pruning and wet olive mill cake (SCPr) or its vermicompost (SVPr) were assayed at pilot scale for its use in olive grove areas. Their removal efficiency for five pesticides applied at high concentration was compared with the biobed with SPS. The effect of a grass layer on the efficiency of these biobeds was also evaluated. Pesticides were retained mainly in the upper layer. In non-planted biobeds with SCPr and SVPr, pesticides dissipation was higher than in SPS, except for diuron. In the biobed with SVPr, with the highest pesticide dissipation capacity, the removed amount of dimethoate, imidacloprid, tebuconazole, diuron and oxyfluorfen was 100, 80, 73, 75 and 50%, respectively. The grass layer enhanced dehydrogenase and diphenol-oxidase activities, modified the pesticides dissipation kinetics and favored the pesticide downward movement. One metabolite of imidacloprid, 3 of oxyfluorfen and 4 of diuron were identified by GC-MS. These novel biobeds represent an alternative to the traditional one and a contribution to promote a circular economy for the olive-oil production.

Effect of dissolved organic carbon on sorption of pyrethroids to sediments.

Despite their strong hydrophobicity, recent studies showed widespread occurrence of pyrethroid in downstream surface waters bodies. In this work, the effect of dissolved organic carbon (DOC) on the sorption and desorption of pyrethroids in sediment was evaluated to understand the role of DOC in facilitating pyrethroid transport. Presence of DOC from three sources at 38 ± 2 mg L⁻¹ in the aqueous phase decreased pesticide sorption to a sediment by 1.7 to 38.9 times and increased their desorption by 1.2 to 41.4 times. The effect on pyrethroid sorption to the sediment was linear. In addition, interactions between DOC and pyrethroids, when taking place prior to the contact with sediment, decreased sorption of some pyrethroids even further, implying that DOC-pyrethroid complexs were relatively stable in solution. DOC sources with higher contents of carboxylic and phenolic groups were found to have a higher potential to associate with pyrethroids. The DOC-water partition coefficients (K(DOC)) obtained by solid-phase microextraction measurement were significantly correlated (P < 0.01) with K(d) values measured for the sediment. These results provide evidence that DOC increases the distribution of pyrethroids from the sediment to the solution phase and plays an important role in mobilizing pyrethroids in runoff and surface streams.

Contribution by different organic fractions to triazines sorption in Calcaric Regosol amended with raw and biotransformed olive cake.

A soil, olive cake, compost and vermicompost of olive cake, were subjected to sequential laboratory extraction to progressively remove water-soluble, lipid and alkali-soluble (humic-type) fractions. Sorption experiments with triazines were carried out with non-amended and amended soil and with soil residues in the intermediate stages during the laboratory removal of the different organic fractions. Herbicide sorption in soil amended with olive cake was between two and three times higher than sorption in composted substrates. In non-amended soil, the removal of humic and fulvic acids led to a decrease of triazines sorption indicating the importance of these fractions in the sorption of these pesticides. The greater triazines sorption in soil amended with olive cake could be associated with the high concentration of water-soluble substances. In contrast, olive cake lipids did not favour the sorption of the more hydrophobic herbicides as indicated by the fact that the sorbed amount increased 30-40% when this fraction was removed. No significant (P>0.05) differences in K(oc) values were found in soils amended with compost and vermicompost in the course of the progressive removal of the different organic fractions, indicating triazine sorption was related more with the total amount of organic matter than with its chemical composition.

Design of experiments in environmental chemistry studies: example of the extraction of triazines from soil after olive cake amendment.

The disposal of natural, composted and vermicomposted olive cake for modifying the fate of triazine herbicides with different physicochemical properties (terbuthylazine, cyanazine, simazine and prometryn) has been tested. Experimental design (surface response methodology plus desirability function) to multicriteria optimization was carried out to evaluate both dose and type of amendment to retain the cited analytes and to develop two simple and low cost analytical methods for extracting triazines from soil. From a methodological point of view, classical and D-optimal designs were employed depending on the problem. Thus, the best combination of soil amount and solvent ratio, the most important parameters affecting triazine extraction from soil, was looked for by means of Central Composite Designs. Under the optimized conditions, the range of triazines recovery was 75-85% for shaking extraction and 87-107% for ultrasonic extraction. Regarding the amendment assay, D-optimal design was selected to keep the reliability of the estimations. Natural olive cake added to the soil at a high dose (8%) reduced herbicide recovery to ca. 50-60% for terbuthylazine, prometryn and simazine, while cyanazine recovery was negligible. Design of experiment provides an efficient working strategy to explore those conditions which ensure the optimum or target value of several responses evaluated simultaneously.

Behavior of bensulfuron-methyl in an agricultural alkaline soil.

A field experiment to determine the available bensulfuron-methyl (BSM) in the upper soil layer was conducted in an agricultural area in the South of Spain. To facilitate herbicide analysis, two application rates were employed, 200 g ha(-1) and 5 kg ha(-1). Samples of upper soil and soil solution were collected. Soil solution was sampled by means of metallic samplers, placed at a depth of 35 cm. In the plots receiving the lower dose ceramic suction, porous cups were also installed. Results from soil solution samples showed that the maximum BSM concentration was found after 8-10 days for the high irrigation supply (945 mm) and after 18-25 days for the lower irrigation regime (405 mm). The mathematical model FOCUSPELMO 1.1.1 was applied to interpret the data obtained in the field experiments. In general, there was a reasonable agreement between experimental and simulated data for soil samples, although the model did not acceptably predict herbicide concentrations in water soil samples. Ceramic cups sampled a higher soil water volume and more frequently than did the metallic samplers. However some variable results were attributed to preferential flow.