RESUMO
Background: This work studied the use of the organic fertilizers DTPA-Fe and EDDS-Fe as iron chelates for solar driven photo-Fenton process at natural pH. This process was proposed to investigate its performance on removing a mixture of agrochemicals (propiconazole, imidacloprid and diuron) from pineapple processing wastewater to obtain a suitable effluent to be reused in the agricultural sector. Methods: Experiments were carried out in a solar simulator with a stirred cylindric photoreactor, with a volume of 150 mL and controlled temperature (20°C). The first set of experiments was carried out with ultrapure water to determine optimal iron and H 2O 2 concentrations. The second was performed with simulated wastewater of pineapple processing. Results: The optimized operational conditions for both iron complexes were 10 mg L -1 of Fe (III) and 25 mg L -1 of H 2O 2, since more than 80% of micropollutants (MP) (at an initial concentration of 1 mg L -1 of each compound) were removed in only 20 min with both DTPA-Fe and EDDS-Fe. The effect of organic matter and inorganic salts on radicals scavenging and chelates stability was also investigated in the experiments performed with synthetic pineapple processing wastewater. The results disclosed differences depending on the iron complex. Nitrites were the principal component influencing the tests carried out with EDDS-Fe. While carbonates at low concentration only significantly affected the experiments performed with DTPA-Fe, they were the major influence on the MPs removal efficiency decrease. In contrast, the presence of Ca 2+ and Mg 2+ only influence on this last one. Finally, the results of phytotoxicity disclosed the suitability of treated effluent to be reused in the agricultural sector. Conclusions: This work demonstrated that solar powered photo-Fenton catalysed by iron fertilizer EDDS is a suitable technology for depolluting water streams coming from pineapple processing plants at circumneutral pH, and its subsequent reuse for crop irrigation.
RESUMO
Background: The management of empty pesticide containers (EPC) in Bolivia has been recently promoted as a control strategy for dispersed pollution in surface and underground water bodies, as well as in soil. It comprises the rinsing and proper disposal or reuse of clean EPC. However, the rinsing transfers the hazard to water, which must be properly treated before being discharged. Methods: In this study, solar photo-Fenton at low Fe 2+ doses were tested at pilot plant scale in Cochabamba (Bolivia) for the removal of pesticides dimethoate and atrazine in their commercial form, spiked in river water. Results: The results demonstrated that solar photo-Fenton ([H 2O 2] 0 = 200 mg L -1) with Fe 2+ concentrations between 0.5 and 1.5 mg L -1 is an effective method to remove dimethoate and atrazine, at an initial concentration of 10 mg L -1 each. Efficiency increased when increasing Fe 2+ doses, achieving a removal over 99% of both pesticides after a solar irradiation period of 60 minutes (corresponding to an accumulated energy of 4.96 kJ L -1). Conclusions: The presence of high concentrations of natural components of river water, mainly organic and inorganic carbon species, would have contributed to hydroxyl radical scavenging, explaining, together with the low iron dose applied, the high energy (irradiation time) and high hydrogen peroxide concentration required to produce pesticide depletion. Additionally, the relatively low oxidant consumption and mineralization observed leave room for process optimization regarding oxidant and catalyst doses and warrant further studies on its coupling with biological or other post-treatments for the removal of transformation products.
RESUMO
Due to the increasing food demand, the use of pesticides in agriculture is increasing. Particularly in low income countries poor training among farmers, combined with the use of obsolete pesticides may result in a high risk for the consumers. In this study six organochlorines and five organophosphates were analyzed in 54 samples of tomatoes from small scale farmers in Bolivia. The analyses were done on unprocessed, stored, washed and peeled tomatoes. The cumulated risk associated with consumption of the tomatoes after different storage times and processing treatments was evaluated using the Hazard Index (HI) for acute risk assessment. All 11 pesticides were detected in the analyses although several of them are obsolete and included in the Stockholm convention ratified by Bolivia. The organochlorines were found in the µg pesticide/kg tomato range and below the HI, while the organophosphates were present in the mg pesticide/kg tomato range and most often above the HI. The low organochlorine concentrations were not significantly affected by time or treatment, but storage significantly decreased the concentrations of organophosphates. Washing decreased the initial concentrations to between 53% (malathion) down to 2% (ethyl parathion), while peeling had a larger effect reducing the initial concentrations to between 33% (malathion) and 0.7% (chlorpyriphos). Both the acute and chronic cumulative risk assessment of organophosphates showed a dietary risk for unprocessed tomatoes three days after harvest. For children, also the consumption of washed tomatoes constituted a dietary risk. To reduce the dietary risk of pesticide residues in Bolivia, there is an urgent need of farmer education and introduction of less hazardous pesticides as well as resources for surveillance and enforcement of legislation in order to ensure public health.