Enhancing Constructed Wetlands with Activated Biochar for the Removal of Pesticides and Pharmaceuticals
Constructed wetlands are nature-based solutions increasingly employed for the treatment of wastewater, mainly in the countryside and urban-rural fringe. Nonetheless, their capacity to effectively reduce the concentrations of contaminants such as pesticides and drugs is generally low. The use of biochar as an amendment to the substrate provides a potential solution to improve the efficiency of CWs.
Biochar, being rich in carbon and derived from the pyrolysis of biomass, is prized for its large surface area, pore structure, and capacity to adsorb micropollutants of an organic nature. It can be originated from vegetal waste thus increasing circularity. When it is added to wetland media, biochar can sequester pesticides and pharmaceuticals through physical adsorption, electrostatic forces, and π–π association. Also, its pore structure is conducive to microbial habitats, thus facilitating biodegradation reactions.
To optimise its pollutant removal capacity, biochar can be activated before use. Chemical activation, using agents such as phosphoric acid (H₃PO₄), potassium hydroxide (KOH), or hydrochloric acid (HCl), enhances surface acidity and introduces functional groups that improve adsorption affinity. The choice of activation method depends on the target contaminants and source biomass.
Left image: Surface area image of biochar before activation under Scanning Electron Microscope (SEM) – Right image: Column of biochar (left) and sand (right).
Field and pilot-scale studies show that activated biochar significantly improves the retention of pesticides (e.g., atrazine, glyphosate) and pharmaceuticals (e.g., antibiotics, anti-inflammatories), extending the lifespan and efficiency of CWs. By combining adsorption and biodegradation, biochar-amended wetlands represent a low-cost, scalable, and eco-friendly solution for improving the removal of trace organic pollutants from irrigation water coming from either traditional or alternative sources.
