Design of an optimized biomixture for the degradation of carbofuran based on pesticide removal and toxicity reduction of the matrix

Abstract

Pesticide biopurification systems contain a biologically active matrix (biomixture) responsible for the accelerated elimination of pesticides in wastewaters derived from pest control in crop fields. Biomixtures have been typically prepared using the volumetric composition 50:25:25 (lignocellulosic substrate/humic component/soil); nonetheless, formal composition optimization has not been performed so far. Carbofuran is an insecticide/nematicide of high toxicity widely employed in developing countries. Therefore, the composition of a highly efficient biomixture (composed of coconut fiber, compost, and soil, FCS) for the removal of carbofuran was optimized by means of a central composite design and response surface methodology. The volumetric content of soil and the ratio coconut fiber/compost were used as the design variables. The performance of the biomixture was assayed by considering the elimination of carbofuran, the mineralization of (14)C-carbofuran, and the residual toxicity of the matrix, as response variables. Based on the models, the optimal volumetric composition of the FCS biomixture consists of 45:13:42 (coconut fiber/compost/soil), which resulted in minimal residual toxicity and ∼99% carbofuran elimination after 3 days. This optimized biomixture considerably differs from the standard 50:25:25 composition, which remarks the importance of assessing the performance of newly developed biomixtures during the design of biopurification systems.

On-Farm Removal of Pesticides: Current Insights on Biopurification Systems

“…Nonetheless, after the spread of BPS use to other geographic locations, readily available materials were adopted, including several local lignocellulosic substrates such as barley husk, coconut fiber, rice husk, oak husk, pine sawdust, and vine branches; − likewise, the use of compost as a substitute for peat in Mediterranean and tropical latitudes , has yielded efficient biomixtures. Not only has the application of alternative materials resulted in improved biomixtures, but also the recent optimization of the volumetric composition itself has been proven to be an important parameter for the enhancement of removal performance in these matrices. , …”

“…The use of the acute test in D. magna has revealed a marked detoxification (even reaching complete detoxification) during the treatment of insecticides such as carbofuran, , mixtures of carbofuran and chlorpyrifos, mixtures of carbamates (aldicarb, carbofuran, methiocarb, methomyl), or even in the combination of chlorpyrifos with triazine herbicides . The chronic test, however, revealed adverse effects of carbofuran residues on the reproduction of daphnids even if acute toxicity was negligible; similarly, these residues also produced metabolic alterations in the fish O. aureus .…”

“…Not only has the application of alternative materials resulted in improved biomixtures, but also the recent optimization of the volumetric composition itself has been proven to be an important parameter for the enhancement of removal performance in these matrices. 14,15 Due to their simple construction and maintenance, BPSs have been adopted in several countries, particularly in Europe 6,7 and Latin America; 5 moreover, configuration variations have led to their renaming as biofilters in Belgium, Phytobacs or biobacs in France, and biomassbeds in Italy, just to mention a few. 2,3…”

“…The volumetric composition has been modified as well, resulting in biomixtures prepared using only two components 11 or the usual three at different ratios. For instance, the systematic optimization of the volumetric composition was performed for the design of a biomixture intended for carbofuran removal; a central composite design coupled to a surface response approach showed that a composition of 45:13:42 (coconut fiber:compost:soil) maximized removal and minimized residual toxicity in a standard biomixture; 14 in the meantime, the same approach resulted in an optimized composition of 30:43:27 for a fungally bioaugmented biomixture. 15 Such variable results suggest that, although expensive and time-consuming, the optimization of biomixture composition should ideally be performed for the target pesticide or mixture of pesticides to be treated.…”

“…Available reports have basically assessed the effect on two different processes, mineralization of pesticides to CO 2 or the removal of the active ingredients during codisposal of commercial formulations of oxytetracycline, kasugamycin, or the mixture containing oxytetracycline+gentamicin (Table 4). Mineralization profiles of 14 C-carbofuran during codisposal of oxytetracycline 29 and 14 C-chlorpyrifos during codisposal of either oxytetracycline 23 or kasugamycin 80 exhibited interesting hormetic-like effects on parameters such as mineralization rates or maximum mineralization according to antibiotic doses employed (Figure 1A); i.e., lower doses (usually within the range of potential concentrations found in BPSs according to common antibiotic use recommendations; <100 mg/kg in the biomixture) enhanced pesticide mineralization, while extremely high doses (unlikely to be found in a BPS, >500 mg/kg) had the contrary (and expected) effect of decreasing mineralization parameters. Particular case-by-case differences can be found in Table 4.…”