Expanding the application scope of on-farm biopurification systems: Effect and removal of oxytetracycline in a biomixture

Biological treatment of pesticide-containing wastewater from coffee crops: selection and optimization of a biomixture and biobed design

The biopurification systems (BPS) or biobeds are employed for the treatment of pesticide-containing wastewater of agricultural origin. The use of these devices for pesticide removal requires the proper optimization of the composition of biomixtures (BPS active matrix) according to the target pesticides applied on a specific crop and the available materials used in their elaboration. This work aims to design a biomixture for the simultaneous treatment of several pesticides applied in coffee crops, according to local practices in Costa Rica. Three biomixtures containing either coffee husk, coconut fiber or rice husk (as the lignocellulosic substrate) were applied for the removal of 12 pesticides. The profiles of pesticide elimination and the mineralization of radiolabeled chlorpyrifos (14C-chlorpyrifos) revealed that the best performance was achieved with the coconut fiber biomixture, even though similar detoxification patterns were determined in every biomixture (according to immobilization in Daphnia magna and germination tests in Lactuca sativa). The optimization of this biomixture's composition by means of a central composite design permitted the definition of two optimal compositions (compost:soil:coconut fiber, % v/v) that maximized pesticide removal: i. 29:7.3:63.7 and ii. 11:7.3:81.7. The validation of these optimized compositions also included the use of an alternative soil from another coffee farm and resulted in overall DT50 values of 7.8-9.0 d for the pesticide mixture. Considering the removal kinetics in the optimized biomixture, a 1 m3 BPS prototype was dimensioned to be eventually used in local coffee farms. This work provides relevant information for the design and implementation of BPS at on-farm conditions for the treatment of pesticide-containing wastewater of a major crop.

A novel and affordable bioaugmentation strategy with microbial extracts to accelerate the biodegradation of emerging contaminants in different media

This study describes a new bioaugmentation alternative based on the application of aqueous aerated extracts from a biomixture acclimated with ibuprofen, diclofenac and triclosan. This bioaugmentation strategy was assayed in biopurification systems (BPS) and in contaminated aqueous solutions to accelerate the removal of these emerging contaminants. Sterilized extracts or extracts from the initial uncontaminated biomixture were used as controls. In BPS, the dissipation of 90% of diclofenac and triclosan required, respectively, 60 and 108 days less than in the controls. The metabolite methyl-triclosan was determined at levels 12 times lower than in controls. In the bioaugmented solutions, ibuprofen was almost completely eliminated (99%) in 21 days and its hydroxylated metabolites were also determined to be at lower levels than in the controls. The plasmidome of acclimated biomixtures and its extract appeared to maintain certain types of plasmids but degradation related genes became less evident. Several dominant OTUs found in the extract identified as Flavobacterium and Fluviicola of the phylum Bacteroidetes, Thermomicrobia (phylum Chloroflexi) and Nonomuraea (phylum Actinobacteria), may be responsible for the enhanced dissipation of these contaminants. This bioaugmentation strategy represents an advantageous tool to facilitate in situ bioaugmentation.

Destination of pesticide residues on biobeds: State of the art and future perspectives in Latin America

Land-use intensification with a high demand for pesticides is a consequence of human population increase. Feasible alternatives for correct concentrated residues discharge are necessary to avoid soil and water resources contamination. Biobeds are in situ bioreactors for treating pesticide residues, used by several European and American countries due to its low cost and simple construction, whose efficiency has been scientifically proved for over 20 years. This review presents the state of the art of biobeds in Latin America (LA), identifying advances and future research needs. Factors affecting the efficiency of biobeds are discussed, like ideal temperature, moisture, and microbial communities, followed by methods for evaluating the bioreactor's efficiency. It was necessary to adapt this technology to the climatic and economic conditions of Latin-American countries, due to its European origins. Guatemala is the LA country that uses biobeds as official technology. Brazil, Argentina, Costa Rica and Chile are examples of countries that are actively investigating new substrates and pursuing legal aspects for the establishment of the biobeds. Robust scientific evidences may enable farmers start using this technology, which is an environmentally safe system to protect water resources.

Fate of environmental pollutants

This annual review covers the literature published in 2018 on topics related to the occurrence and fate of environmental pollutants in wastewater. Due to the vast amount of literature published on this topic, we have discussed only a portion of the quality research publications, due to the limitation of space. The abstract search was carried out using Web of Science, and the abstracts were selected based on their relevance. In a few cases, full-text articles were referred to understand new findings better. This review is divided into the following sections: antibiotic-resistant bacteria (ARBs) and antibiotic-resistant genes (ARGs), disinfection by-products (DBPs), drugs of abuse (DoAs), estrogens, heavy metals, microplastics, per- and polyfluoroalkyl compounds (PFAS), pesticides, and pharmaceuticals and personal care products (PPCPs), with the addition of two new classes of pollutants to previous years (DoAs and PFAS).

Removal of triazines, triazoles and organophophates in biomixtures and application of a biopurification system for the treatment of laboratory wastewaters

Biopurification systems (BPS) have been barely explored for removing complex mixtures of pesticides. In this study, the potential of a biomixture to remove simultaneously a mixture of herbicides (triazines), fungicides (triazoles) and insecticides (organophosphates) is presented. Also, a BPS using the same biomixture was used for treating a pesticide testing laboratory wastewater containing a mixture of 38 compounds. Ecotoxicological assays were conducted on the BPS elutriates to investigate the mixture detoxification. A mixture (concentrations of 4-8 mg kg^-1) run in small-scale biomixture systems (SSB) for 128 d showed 59.3% removal of triazines, 68.5% of organophosphates and no elimination of triazoles. The treatment of the laboratory wastewater (individual concentrations range: 0.0036-0.25 mg kg^-1) in the pilot-scale BPS for 281 d resulted in the elimination pattern of organophosphates (90.0%) > triazoles (73.4%) > carbamates (71.3%) > triazines (54.3%). Complete detoxification towards Daphnia magna and partial detoxification in Lactuca sativa seeds germination occurred in the BPS. Although the pesticide mixture complexity is higher in the BPS, the lower concentrations found in this matrix, could explain removal differences between SSB and BPS and the apparent inhibition in the elimination of carbamates and some triazines observed in the latter. These findings suggest that disposal of pesticide-containing laboratory-wastewater should be done in separate containers, according to chemical groups before their treatment in separate BPS, in order to reduce treatment periods. Monitoring the treatment process in the BPS with a battery of ecotoxicological tests is strongly recommended.

Removal of herbicides in a biopurification system is not negatively affected by oxytetracycline or fungally pretreated oxytetracycline

The disposal of agricultural antibiotic-containing wastewater in biopurification systems (BPS) employed in the treatment of pesticides, may negatively affect the removal capacity of these devices. This work aimed to employ a fungal pretreatment of oxytetracycline (OTC)-rich wastewater, before its disposal in a BPS used for the treatment of two pesticides. The fungal treatment at reactor scale (stirred tank reactor, 3L) with biomass of Trametes versicolor efficiently removed 100 mg L-1 OTC in only 60 h. However, ecotoxicity tests on seed germination with Lactuca sativa revealed that antibiotic elimination did not correlate with a decrease in toxicity. After the pretreatment, treated OTC was discarded in biomixtures used for the elimination of the herbicides ametryn and terbutryn. The co-application of treated or untreated OTC did not inhibit the removal of the herbicides; moreover, in both cases their removal seemed to be slightly enhanced in the presence of OTC or its residues, with respect to antibiotic-free biomixtures. Estimated half-lives ranged from 28.4 to 34.8 d for ametryn, and 34.0-51.0 d for terbutryn. In addition, the biomixture was also able to remove OTC in the presence of the herbicides, with an estimated half-life of 38 d. Remarkably, the toxicity of the wastewater containing OTC or treated OTC was mostly eliminated after its disposal in the biomixture. Overall results suggest that, given the high efficiency of the biomixture, the fungal pretreatment of OTC-containing wastewater is not mandatory before its disposal in the BPS.

Impact of oxytetracycline and bacterial bioaugmentation on the efficiency and microbial community structure of a pesticide-degrading biomixture

An experimental study evaluating the effect of bioaugmentation and antibiotic (oxytetracycline) application on pesticide degradation and microbial community structure of a biomixture used in a biopurification system (BPR) was conducted. The bioaugmentation employed a carbofuran-degrading bacterial consortium. The non-bioaugmented biomixture showed excellent performance for removal of atrazine (t_1/2: 9.9 days), carbendazim (t_1/2: 3.0 days), carbofuran (t_1/2: 2.8 days), and metalaxyl (t_1/2: 2.7 days). Neither the addition of oxytetracycline nor bioaugmentation affected the efficiency of pesticide removal or microbial community (bacterial and fungal) structure, as determined by DGGE analysis. Instead, biomixture aging was mainly responsible for microbial population shifts. Even though the bioaugmentation did not enhance the biomixtures' performance, this matrix showed a high capability to sustain initial stresses related to antibiotic addition; therefore, simultaneous elimination of this particular mixture of pesticides together with oxytetracycline residues is not discouraged.