Integrating composite-media and plants to improve aquifer recharge: measurements, implications, and challenges

Water scarcity intensified by population growth and climate change has caused freshwater resources to dwindle while global water usage per capita increases.Ecosystem-based wastewater treatment that adopts natural processes like soil aquifer treatment (SAT) and constructed wetlands (CW) has been successfully used but requires a large land area and often competes with urban development.It is, therefore, imperative to develop and improve alternative methods to increase effluent recharge volumes without sacrificing water quality.In this study, we adopted a hybrid approach that synergizes the operational dynamics of SAT with CW into a new system that infuses coarse and porous media with plants (termed hereafter MP-SAT).This new approach integrates natural lava rocks (tuff) and hydrophytes (Phragmites australis variegate, Cyperus corymbosus, and Canna coccinea) to increase infiltration flux compared to conventional SAT, while maintaining high water quality.Five pilot-scale lysimeters consisting of MP-SAT packed at 30 and 60 cm, and conventional SAT packed at 60 cm were flooded with secondary wastewater (TWW) for 4 h flooding and dried for 12 h.Infiltration flux, water quality, and removal rates of organic and inorganic nutrients, as well as micropollutants after spiking the feedwater with T4 bacteriophage and ibuprofen were tested.The results indicate that the infiltration flux increased by ~4-fold in MP-SAT configurations compared to SAT.Yet, MP-SAT water quality showed similar (or better) removal efficiencies compared to SAT for NH 4 (50-70 %), TOC (20-25 %), total phosphorus (30-40 %), T4 bacteriophage (98-99 %), bacteria numbers (58-70 %), and ibuprofen (25-40 %).These high removal efficiencies were likely due to high biodegradation rates (1.4-2.5folds) in all MP-SAT compared to the SAT.These results and corresponding insights indicate that integrating porous media and plants with SAT could prove highly advantageous in increasing aquifer recharge without sacrificing water quality or increasing the infiltration areal footprint.