Microalgae-based bioremediation of water contaminated by pesticides in peri-urban agricultural areas

The present study evaluated the capacity of a semi-closed, tubular horizontal photobioreactor (PBR) to remove pesticides from agricultural run-off. The study was carried out in summer (July) to study its efficiency under the best conditions (highest solar irradiation). A total of 51 pesticides, including 10 transformation products, were selected and investigated based on their consumption rate and environmental relevance. Sixteen of them were detected in the agricultural run-off, and the estimated removal efficiencies ranged from negative values, obtained for 3 compounds, namely terbutryn, diuron and imidacloprid, to 100%, achieved for 10 compounds. The acidic herbicide MCPA was removed by 88% in average, and the insecticides 2,4-D and diazinon showed variable removals, between 100% and negative values. The environmental risk associated to the compounds still present in the effluent of the PBR was evaluated using hazard quotients (HQs), calculated using the average and highest measured concentrations of the compounds. HQ values > 10 (meaning high risk) were obtained for imidacloprid (21), between 1 and 10 (meaning moderate risk) for 2,4-D (2.8), diazinon (4.6) and terbutryn (1.5), and <1 (meaning low risk) for the remaining compounds diuron, linuron and MCPA. The PBR treatment yielded variable removals depending on the compound, similarly to conventional wastewater treatment plants. This study provides new data on the capacity of microalgae-based treatment systems to eliminate a wide range of priority pesticides under real/environmental conditions.

This research was funded by European Union's Horizon 2020 research and innovation program within the framework of the INCOVER project (GA 689242) and WATERPROTECT project (727450); by the Spanish Ministry of Science, Innovation and Universities, the Research National Agency (AEI), and the European Regional Development Fund (FEDER) within the project AL4BIO (RTI2018-099495-B-C21), and by the Government of Catalonia (Consolidated Research Group 2017 SGR 01404-Water and Soil Quality Unit). M.J. García-Galán, E. Uggetti and R. Díez-Montero would like to thank the Spanish Ministry of Economy and Competitiveness for their research grants (IJCI-2017-34601, RYC2018-025514-I and FJCI-2016-30997, respectively).

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