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

TL;DR

This study assesses a semi-closed photobioreactor's ability to remove pesticides from agricultural runoff, showing variable efficiencies and potential environmental risk reduction, highlighting the system's capacity for microalgae-based water treatment.

Contribution

It provides new data on the effectiveness of microalgae-based bioremediation systems in removing diverse pesticides from real agricultural runoff conditions.

Findings

10 out of 51 pesticides were completely removed.

Removal efficiencies ranged from negative to 100%.

Environmental risk was reduced for most compounds.

Abstract

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 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% on average, and the insecticides 2,4-D and diazinon showed variable removals, between 100% and negative values. The environmental risk associated with 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, similar to conventional wastewater treatment plants. This study provides new data on the capacity of icroalgae-based treatment systems to eliminate a wide range of priority pesticides under real/environmental conditions.